WO2009119375A1 - Refrigeration device - Google Patents

Abstract

A heat pump unit (701) of a heat pump-type hot water supply device includes: a two-stage compression type compression mechanism (702); a water coolant heat exchanger (704); an evaporator (706) using air as a heat source; a bottom plate (777) which serves as a drain pan for receiving drain water generated in the evaporator (706); and a drain heater (797) which heats the drain water by a coolant discharged from a former-stage compression element (702c) of the compressor mechanism (702) and introduced into a latter-stage compression element (702d).

Description

Refrigeration equipment

The present invention relates to a refrigeration apparatus, and more particularly, to a refrigeration apparatus including a refrigerant circuit having a compression mechanism, a radiator, and an evaporator, and a drain pan that receives drain water generated in the evaporator.

Conventionally, as a kind of refrigeration apparatus, a compressor, a water refrigerant heat exchanger as a radiator that performs heat exchange between hot water and refrigerant, an expansion valve, and air heat as an evaporator that evaporates the refrigerant There is a heat pump unit of a heat pump type water heater that includes a refrigerant circuit having an exchanger and a drain pan that receives drain water generated in the air heat exchanger. As such a heat pump unit, as shown in Patent Document 1, the drain water generated in the air heat exchanger is discharged from a compressor or a configuration that heats the drain water generated by the high-pressure side pipe from the water refrigerant heat exchanger to the expansion valve. Some have a refrigerant pipe for preventing freezing that is heated by a high-temperature and high-pressure refrigerant.
JP 2004-218861 A

In the heat pump unit described above, freezing and growth of drain water can be suppressed by the antifreezing refrigerant pipe as a drain heater when used in low temperature conditions such as winter and cold regions. Since the refrigerant flowing through the pipe is a high-pressure refrigerant in the refrigeration cycle, the power consumed to compress the refrigerant flowing through the anti-freezing refrigerant pipe to the high pressure in the refrigeration cycle by the compressor causes energy loss, and the refrigeration cycle This may cause the operating efficiency of the vehicle to deteriorate.
An object of the present invention is to provide a drain capable of suppressing an increase in energy loss in a refrigeration apparatus including a refrigerant circuit having a compression mechanism, a radiator, and an evaporator, and a drain pan that receives drain water generated in the evaporator. It is to provide a heater.

A refrigeration apparatus according to a first invention is generated in a compression mechanism, a radiator that radiates the refrigerant compressed by the compression mechanism, an evaporator that evaporates the refrigerant radiated by the radiator using air as a heat source, and the evaporator A drain pan for receiving drain water and a drain heater. The compression mechanism has a plurality of compression elements, and is configured to sequentially compress the refrigerant discharged from the front-stage compression elements of the plurality of compression elements with the rear-stage compression elements, The drain heater is a heat exchanger that heats drain water using a refrigerant that is discharged from the compression element on the front stage side and sucked into the compression element on the rear stage side. Here, the “compression mechanism” refers to a compressor in which a plurality of compression elements are integrally incorporated, a compressor in which a single compression element is incorporated, and / or a compressor in which a plurality of compression elements are incorporated. This means a configuration that includes a unit connected. In addition, “sequentially compresses the refrigerant discharged from the compression element on the front stage among the plurality of compression elements with the compression element on the rear stage” is referred to as “compression element on the front stage” and “compression element on the rear stage” It is not only meant to include two compression elements connected in series, but a plurality of compression elements are connected in series, and the relationship between the compression elements is the above-mentioned “previous-side compression element” ”And“ compression element on the rear stage side ”.

In this refrigeration apparatus, a multistage compression type compression mechanism is employed, and drain water generated in the evaporator is heated by a refrigerant (that is, an intermediate pressure refrigerant in a refrigeration cycle) sucked into a compression element on the rear stage side of the compression mechanism. Since the drain heater is used, the drain water is heated to suppress freezing and growth of the drain water in the evaporator and drain pan, and the temperature of the intermediate pressure refrigerant in the refrigeration cycle is reduced to reduce the temperature in the refrigeration cycle. Increase in energy loss can be suppressed. Thereby, in this refrigeration apparatus, an increase in energy loss can be suppressed as compared with a case where a drain heater that heats drain water with a high-pressure refrigerant in the refrigeration cycle is used.

A refrigeration apparatus according to a second aspect of the present invention is the refrigeration apparatus according to the first aspect of the present invention, wherein the drain heater is disposed at the lower part of the evaporator.
In this refrigeration apparatus, since the drain heater is disposed at the lower part of the evaporator, the drain water is less likely to freeze at the lower part of the evaporator where the amount of attached drain water is the largest due to the flow of the drain water. Freezing and growth of drain water in the evaporator can be effectively suppressed.

A refrigeration apparatus according to a third aspect is the refrigeration apparatus according to the first aspect, wherein the drain heater is disposed in the drain pan.
In this refrigeration system, since the drain heater is disposed in the drain pan, the drain water that flows down from the evaporator and accumulates in the drain pan becomes difficult to freeze, thereby effectively freezing and growing the drain water in the drain pan. Can be suppressed.

A refrigeration apparatus according to a fourth aspect of the present invention is the refrigeration apparatus according to the first aspect of the present invention, wherein the drain heater is a first drain heater disposed at the lower portion of the evaporator and a second drain heater disposed at the drain pan. And have.
In this refrigeration apparatus, since the drain heater has the first drain heater disposed in the lower part of the evaporator and the second drain heater disposed in the drain pan, the drain water flows most by the flow of the drain water. The drain water is less likely to freeze in the lower part of the evaporator where the amount of adhesion increases, and the drain water that flows down from the evaporator and accumulates in the drain pan is less likely to freeze, thereby freezing and growing the drain water in the evaporator, And both freezing and growth of drain water in a drain pan can be suppressed effectively.

The refrigeration apparatus according to a fifth aspect of the invention is the refrigeration apparatus according to the fourth aspect of the invention, wherein the refrigerant discharged from the front-stage compression element and sucked into the rear-stage compression element is heated by the first drain heater and the second drain heater. A drain heater switching mechanism is further provided for switching so as to allow flow to only one of the units.
In this refrigeration apparatus, since a drain heater switching mechanism that enables switching between the first drain heater and the second drain heater is further provided, either the first drain heater or the second drain heater is provided. Only one can be used as needed.

A refrigeration apparatus according to a sixth aspect of the present invention is a compression mechanism, a heat exchanger that uses air as a heat source and functions as a heat radiator or evaporator for a refrigerant, and a refrigerant evaporator or radiator for a refrigerant. Cooling operation state in which refrigerant is circulated in the order of a functioning use side heat exchanger, a compression mechanism, a heat source side heat exchanger functioning as a refrigerant radiator, a use side heat exchanger functioning as a refrigerant evaporator, and a compression mechanism A switching mechanism that switches between a heating operation state in which the refrigerant is circulated in the order of a use side heat exchanger that functions as a refrigerant radiator and a heat source side heat exchanger that functions as a refrigerant evaporator, and is generated in the heat source side heat exchanger A drain pan for receiving drain water, an intermediate heat exchanger, and a drain heater are provided. The compression mechanism has a plurality of compression elements, and is configured to sequentially compress the refrigerant discharged from the front-stage compression elements of the plurality of compression elements with the rear-stage compression elements, The intermediate heat exchanger is a heat exchanger that functions as a refrigerant cooler that is discharged from the front-stage compression element and sucked into the rear-stage compression element when the switching mechanism is in the cooling operation state. The heater is a heat exchanger capable of heating the drain water with the refrigerant discharged from the front-stage compression element and sucked into the rear-stage compression element when the switching mechanism is in the heating operation state. . Here, the “compression mechanism” refers to a compressor in which a plurality of compression elements are integrally incorporated, a compressor in which a single compression element is incorporated, and / or a compressor in which a plurality of compression elements are incorporated. This means a configuration that includes a unit connected. In addition, “sequentially compresses the refrigerant discharged from the compression element on the front stage among the plurality of compression elements with the compression element on the rear stage” is referred to as “compression element on the front stage” and “compression element on the rear stage” It is not only meant to include two compression elements connected in series, but a plurality of compression elements are connected in series, and the relationship between the compression elements is the above-mentioned “previous-side compression element” ”And“ compression element on the rear stage side ”.

In this refrigeration apparatus, in the refrigerant circuit configured to be able to switch between the cooling operation and the heating operation by the switching mechanism, a multistage compression type compression mechanism is adopted, and when the switching mechanism is in the cooling operation state, An intermediate heat exchanger that functions as a cooler for refrigerant sucked into the compression element on the rear stage side (that is, refrigerant of intermediate pressure in the refrigeration cycle), and a heat source side heat exchanger when the switching mechanism is in a heating operation state Because the drain heater that heats the drain water generated in the refrigeration cycle is used, the intermediate heat exchanger lowers the temperature of the intermediate pressure refrigerant in the refrigeration cycle during the cooling operation. Increase in heat dissipation loss in the exchanger can be suppressed, and during the heating operation, the drain water is heated by the drain heater to heat exchange on the heat source side It suppresses the freezing and growth of drain water in and drain pan, by lowering the temperature of the intermediate-pressure refrigerant in the refrigeration cycle, it is possible to suppress an increase in the energy loss in the refrigeration cycle. Thus, in this refrigeration apparatus, in the cooling operation, the intermediate heat exchanger is used to cool the intermediate pressure refrigerant in the refrigeration cycle with the air as the heat source, so that the heat source side heat exchanger that functions as a refrigerant radiator is used. The heat dissipation loss can be reduced, and during heating operation, the drain heater is used to suppress freezing and growth of drain water, and the intermediate pressure refrigerant in the refrigeration cycle is cooled by the drain water as the heat source. Compared to the case of using a drain heater that heats drain water with a high-pressure refrigerant, an increase in energy loss during heating operation can be suppressed.

A refrigeration apparatus according to a seventh aspect of the invention is the refrigeration apparatus according to the sixth aspect of the invention, wherein the drain heater is disposed at the lower part of the heat source side heat exchanger.
In this refrigeration system, since the drain heater is disposed at the lower part of the heat source side heat exchanger, the drain water is frozen at the lower part of the heat source side heat exchanger where the amount of drain water adhering to the greatest amount due to the flow of drain water. As a result, it is possible to effectively suppress freezing and growth of drain water in the heat source side heat exchanger.

A refrigeration apparatus according to an eighth aspect is the refrigeration apparatus according to the sixth aspect, wherein the drain heater is disposed in the drain pan.
In this refrigeration system, since the drain heater is arranged in the drain pan, the drain water that flows down from the heat source side heat exchanger and accumulates in the drain pan becomes difficult to freeze, thereby freezing and growing the drain water in the drain pan. It can be effectively suppressed.

A refrigeration apparatus according to a ninth aspect is the refrigeration apparatus according to the sixth aspect, wherein the drain heater is a first drain heater disposed at a lower portion of the heat source side heat exchanger and a second drain disposed in the drain pan. And a drain heater.
In this refrigeration apparatus, the drain heater has the first drain heater arranged at the lower part of the heat source side heat exchanger and the second drain heater arranged in the drain pan, so that the drain water flows most In the lower part of the heat source side heat exchanger where the amount of drain water increases, the drain water is less likely to freeze, and the drain water that flows down from the heat source side heat exchanger and accumulates in the drain pan is less likely to freeze. Both freezing and growth of drain water in the heat exchanger and freezing and growth of drain water in the drain pan can be effectively suppressed.

The refrigeration apparatus according to a tenth aspect of the invention is the refrigeration apparatus according to the ninth aspect of the invention, wherein the refrigerant discharged from the front-stage compression element and sucked into the rear-stage compression element is heated by the first drain heater and the second drain heater. A drain heater switching mechanism is further provided for switching so as to allow flow to only one of the units.
In this refrigeration apparatus, since a drain heater switching mechanism that enables switching between the first drain heater and the second drain heater is further provided, either the first drain heater or the second drain heater is provided. One can be used as needed.

The refrigeration apparatus according to an eleventh aspect of the invention is the refrigeration apparatus according to the sixth to tenth aspects of the invention, wherein the intermediate heat exchanger is a refrigerant that dissipates heat in the use side heat exchanger when the switching mechanism is in a heating operation state. It functions as an evaporator.
In this refrigeration apparatus, when the switching mechanism is in the heating operation state, it functions as an evaporator for the refrigerant that has dissipated heat in the use-side heat exchanger. While increasing the size, the intermediate heat exchanger can be effectively used during the heating operation.

A refrigeration apparatus according to a twelfth aspect of the present invention is the refrigeration apparatus according to the eleventh aspect of the present invention, wherein the intermediate heat exchanger is disposed on the heat source side heat exchanger.
In this refrigeration apparatus, drain water is also generated from the intermediate heat exchanger during the heating operation, but is generated in the intermediate heat exchanger because the intermediate heat exchanger is disposed above the heat source side heat exchanger. The drain water flows down through the heat source side heat exchanger, and not only the drain water generated in the heat source side heat exchanger but also the drain water generated in the intermediate heat exchanger can be heated by the drain heater.

A refrigeration apparatus according to a thirteenth invention is the refrigeration apparatus according to any of the sixth to twelfth inventions, wherein the intermediate heat exchanger has a larger heat transfer area than the drain heater.
In this refrigeration system, the intermediate heat exchanger has a larger heat transfer area than the drain heater, so that during the cooling operation, the intermediate pressure refrigerant in the refrigeration cycle can be significantly cooled. The heat dissipation loss in the heat source side heat exchanger that sometimes functions as a radiator can be greatly reduced.

It is a schematic block diagram of the heat pump unit which comprises the heat pump type water heater as 1st Embodiment of the freezing apparatus concerning this invention. It is a perspective view which shows the schematic internal structure of a heat pump unit. It is the figure which looked at the bottom plate as an evaporator, a drain heater, and a drain pan from the front side of the heat pump unit. It is a figure which shows the flow of the refrigerant | coolant in a heat pump unit. 1 is a pressure-enthalpy diagram illustrating a refrigeration cycle. FIG. 3 is a temperature-entropy diagram illustrating a refrigeration cycle. It is a schematic block diagram of the heat pump unit concerning the modification 1 of 1st Embodiment. It is the figure which looked at the evaporator, the drain heater in the modification 1 of 1st Embodiment, and the bottom plate as a drain pan from the front side of the heat pump unit. It is a schematic block diagram of the heat pump unit concerning the modification 2 of 1st Embodiment. It is a schematic block diagram of the heat pump unit concerning the modification 2 of 1st Embodiment. It is the figure which looked at the evaporator, the drain heater in the modification 2 of 1st Embodiment, and the bottom plate as a drain pan from the front side of the heat pump unit. It is a schematic block diagram of the heat pump unit concerning the modification 3 of 1st Embodiment. It is a schematic block diagram of the heat pump unit concerning the modification 3 of 1st Embodiment. It is a schematic block diagram of the air conditioning apparatus as 2nd Embodiment of the freezing apparatus concerning this invention. It is an external appearance perspective view (state which removed the fan grille) of the heat source unit. It is a side view of the heat source unit in a state where the right plate of the heat source unit is removed. It is a figure which shows the flow of the refrigerant | coolant in the air conditioning apparatus at the time of air_conditionaing | cooling operation. FIG. 3 is a pressure-enthalpy diagram illustrating a refrigeration cycle during cooling operation. FIG. 3 is a temperature-entropy diagram illustrating a refrigeration cycle during cooling operation. It is a figure which shows the flow of the refrigerant | coolant in the air conditioning apparatus at the time of heating operation. FIG. 3 is a pressure-enthalpy diagram illustrating a refrigeration cycle during heating operation. FIG. 3 is a temperature-entropy diagram illustrating a refrigeration cycle during heating operation. The characteristics of the heat transfer coefficient when carbon dioxide with an intermediate pressure lower than the critical pressure flows into the heat transfer channel and the heat transfer coefficient with high pressure carbon dioxide exceeding the critical pressure flowing in the heat transfer channel. FIG. It is a schematic block diagram of the air conditioning apparatus concerning the modification 1 of 2nd Embodiment. It is a side view of the heat source unit in the state which removed the right board of the heat source unit in the modification 1 of 2nd Embodiment. It is a schematic block diagram of the air conditioning apparatus concerning the modification 2 of 2nd Embodiment. It is a schematic block diagram of the air conditioning apparatus concerning the modification 2 of 2nd Embodiment. It is a side view of the heat source unit in the state which removed the right board of the heat source unit in the modification 2 of 2nd Embodiment. It is a schematic block diagram of the air conditioning apparatus concerning the modification 3 of 2nd Embodiment. It is a schematic block diagram of the air conditioning apparatus concerning the modification 3 of 2nd Embodiment. It is a schematic block diagram of the air conditioning apparatus concerning the modification 4 of 2nd Embodiment. It is a figure which shows the flow of the refrigerant | coolant in an air conditioning apparatus at the time of the air_conditionaing | cooling operation of the modification 4 of 2nd Embodiment. FIG. 10 is a pressure-enthalpy diagram illustrating a refrigeration cycle during cooling operation according to Modification 4 of the second embodiment. FIG. 3 is a temperature-entropy diagram illustrating a refrigeration cycle during cooling operation. It is a figure which shows the flow of the refrigerant | coolant in an air conditioning apparatus at the time of the heating operation of the modification 4 of 2nd Embodiment. FIG. 10 is a pressure-enthalpy diagram illustrating a refrigeration cycle during a heating operation according to Modification 4 of the second embodiment. It is the temperature-entropy diagram in which the refrigerating cycle at the time of the heating operation concerning the modification 4 of 2nd Embodiment was illustrated. It is a schematic block diagram of the air conditioning apparatus concerning the modification 4 of 2nd Embodiment. It is a schematic block diagram of the air conditioning apparatus concerning the modification 5 of 2nd Embodiment. It is a figure which shows the flow of the refrigerant | coolant in an air conditioning apparatus at the time of the air_conditionaing | cooling operation of the modification 5 of 2nd Embodiment. FIG. 10 is a pressure-enthalpy diagram illustrating a refrigeration cycle during a cooling operation according to Modification 5 of the second embodiment. FIG. 3 is a temperature-entropy diagram illustrating a refrigeration cycle during cooling operation. It is a figure which shows the flow of the refrigerant | coolant in an air conditioning apparatus at the time of the heating operation of the modification 5 of 2nd Embodiment. FIG. 10 is a pressure-enthalpy diagram illustrating a refrigeration cycle during a heating operation according to Modification 5 of the second embodiment. FIG. 10 is a temperature-entropy diagram illustrating a refrigeration cycle during a heating operation according to Modification 5 of the second embodiment. It is a schematic block diagram of the air conditioning apparatus concerning the modification 6 of 2nd Embodiment. It is a figure which shows the flow of the refrigerant | coolant in an air conditioning apparatus at the time of the air_conditionaing | cooling operation of the modification 6 of 2nd Embodiment. FIG. 10 is a pressure-enthalpy diagram illustrating a refrigeration cycle during cooling operation according to Modification 6 of the second embodiment. FIG. 3 is a temperature-entropy diagram illustrating a refrigeration cycle during cooling operation. It is a figure which shows the flow of the refrigerant | coolant in an air conditioning apparatus at the time of the heating operation of the modification 6 of 2nd Embodiment. It is the pressure-enthalpy diagram in which the refrigerating cycle at the time of the heating operation concerning the modification 6 of 2nd Embodiment was illustrated. FIG. 10 is a temperature-entropy diagram illustrating a refrigeration cycle during a heating operation according to Modification 6 of the second embodiment. It is a schematic block diagram of the air conditioning apparatus concerning the modification 7 of 2nd Embodiment.

Explanation of symbols

1 Air conditioning equipment (refrigeration equipment)
2, 102, 702 Compression mechanism 3 Switching mechanism 4 Heat source side heat exchanger (heat radiator, evaporator)
6 Use side heat exchanger (evaporator, radiator)
7 Intermediate heat exchanger 77, 777 Drain pan 97, 797 Drain heater 97a, 797a First drain heater 97b, 797b Second drain heater 98, 798 Drain heater switching mechanism 701 Heat pump unit (refrigeration apparatus)
704 Water refrigerant heat exchanger (heat radiator)
706 Evaporator

Hereinafter, an embodiment of a refrigeration apparatus according to the present invention will be described based on the drawings.
-First embodiment-
(1) Configuration of Heat Pump Unit of Heat Pump Type Water Heater FIG. 1 is a schematic configuration diagram of a heat pump unit 701 constituting a heat pump type hot water heater as a first embodiment of a refrigeration apparatus according to the present invention. The heat pump unit 701 has a refrigerant circuit 710 for heating water (water supply) supplied from a hot water storage unit (not shown), and a unit for returning the heated water (hot water) to the hot water storage unit. It is.
The refrigerant circuit 710 of the heat pump unit 701 mainly includes a compression mechanism 702, a water refrigerant heat exchanger 704, an expansion mechanism 705, an evaporator 706, and a drain heater 797, and operates in the supercritical region. The refrigerant to be charged (here, carbon dioxide) is filled.

In this embodiment, the compression mechanism 702 includes a compressor 721 that compresses the refrigerant in two stages with two compression elements. The compressor 721 has a sealed structure in which a compressor drive motor 721b, a drive shaft 721c, and compression elements 702c and 702d are accommodated in a casing 721a. The compressor drive motor 721b is connected to the drive shaft 721c. The drive shaft 721c is connected to the two compression elements 702c and 702d. That is, in the compressor 721, two compression elements 702c and 702d are connected to a single drive shaft 721c, and the two compression elements 702c and 702d are both rotationally driven by the compressor drive motor 721b. It has a stage compression structure. In the present embodiment, the compression elements 702c and 702d are volumetric compression elements such as a rotary type and a scroll type. The compressor 721 sucks the refrigerant from the suction pipe 702a, compresses the sucked refrigerant by the compression element 702c, discharges the refrigerant to the intermediate refrigerant pipe 708, and discharges the refrigerant discharged to the intermediate refrigerant pipe 708 to the compression element 702d. And the refrigerant is further compressed and then discharged to the discharge pipe 702b. Here, the intermediate refrigerant pipe 708 sucks the intermediate-pressure refrigerant in the refrigeration cycle discharged from the compression element 702c connected to the upstream side of the compression element 702d into the compression element 702d connected to the downstream side of the compression element 702c. It is a refrigerant pipe for making it. The discharge pipe 702b is a refrigerant pipe for sending high-pressure refrigerant in the refrigeration cycle discharged from the compression mechanism 702 to the water-refrigerant heat exchanger 704. The discharge pipe 702b includes an oil separation mechanism 741 and a check mechanism. 742. The oil separation mechanism 741 is a mechanism for separating the refrigeration oil accompanying the refrigerant discharged from the compression mechanism 702 from the refrigerant and returning it to the suction side of the compression mechanism 702, and mainly accompanying the refrigerant discharged from the compression mechanism 702. An oil separator 741a that separates the refrigerating machine oil from the refrigerant, and an oil return pipe 741b that is connected to the oil separator 741a and returns the refrigerating machine oil separated from the refrigerant to the suction pipe 702a of the compression mechanism 702 are provided. The oil return pipe 741b is provided with a pressure reducing mechanism 741c for reducing the pressure of the refrigerating machine oil flowing through the oil return pipe 741b. The decompression mechanism 741c uses a capillary tube in this embodiment. The check mechanism 742 allows the flow of refrigerant from the discharge side of the compression mechanism 702 to the water refrigerant heat exchanger 704 as a radiator, and discharges the compression mechanism 702 from the water refrigerant heat exchanger 704 as a radiator. This is a mechanism for blocking the flow of refrigerant to the side, and a check valve is used in this embodiment.

Thus, in this embodiment, the compression mechanism 702 has the two compression elements 702c and 702d, and the refrigerant discharged from the compression element on the front stage of the compression elements 702c and 702d is on the rear stage side. The compression elements are sequentially compressed by the compression elements.
The water refrigerant heat exchanger 704 is a heat exchanger that functions as a radiator for the refrigerant compressed by the compression mechanism 702. One end of the water-refrigerant heat exchanger 704 is connected to the compression mechanism 702, and the other end is connected to the expansion mechanism 5. The water-refrigerant heat exchanger 704 is configured such that water (water supply) is supplied from a hot water storage unit (not shown) through the water circulation pump 779, and can exchange heat with the refrigerant. The water circulation pump 779 is rotationally driven by a pump drive motor 779a.
The expansion mechanism 705 is a mechanism that depressurizes the refrigerant, and an electric expansion valve is used in the present embodiment. Further, in the present embodiment, the expansion mechanism 705 reduces the pressure of the high-pressure refrigerant radiated in the water-refrigerant heat exchanger 704 until it reaches a low pressure in the refrigeration cycle before being sent to the evaporator 706.

The evaporator 706 is a heat exchanger that evaporates the refrigerant radiated by the water refrigerant heat exchanger 704 as a radiator using air as a heat source, one end of which is connected to the expansion mechanism 705 and the other end is a compression mechanism. 702 is connected. Air as a heat source of the evaporator 706 is supplied by a blower fan 740. The blower fan 740 is rotationally driven by a fan drive motor 740a.
The drain heater 797 is a heat exchanger that heats the drain water generated in the evaporator 706 by the refrigerant discharged from the front-stage compression element 702c and sucked into the rear-stage compression element 702d. The intermediate refrigerant pipe 708 is provided. A drain heater 797 is disposed below the evaporator 706.
Next, a configuration in which the drain heater 797 is disposed below the evaporator 706 will be described with reference to FIGS. 2 and 3. Here, FIG. 2 is a perspective view showing a schematic internal structure of the heat pump unit 701, and FIG. 3 is a view of the evaporator 706, the drain heater 797, and the bottom plate 777 as a drain pan from the front side of the heat pump unit 701. FIG. In the following description, “left” and “right” are based on the case where the heat pump unit 701 is viewed from the front plate 775 side.

In the present embodiment, the heat pump unit 701 is a so-called side-blowing type that sucks air from the back and side surfaces and blows air forward, and mainly includes a casing 771 and water disposed in the casing 771. Refrigerant heat exchanger 704 (not shown in FIG. 2), water circulation pump 779 (not shown in FIG. 2), expansion mechanism 5 (not shown in FIG. 2), evaporator 706, drain heater 797, And a device such as a blower fan 740.
In the present embodiment, the casing 771 is a substantially rectangular parallelepiped box, and mainly includes a top plate 772 (illustrated by a two-dot chain line in FIG. 2) constituting the top surface of the casing 771, and an outer peripheral surface of the casing 771. Are composed of a left plate 773, a right plate 774, a front plate 775 and a rear plate 776 (shown by a two-dot chain line in FIG. 2), and a bottom plate 777. The top plate 772 is a horizontally long and substantially rectangular plate-like member that constitutes the top surface of the heat pump unit 701. The left plate 773 is a plate-like member having a substantially rectangular shape in a side view extending downward from the left edge of the top plate 772, and a suction opening (not shown) is formed almost entirely. The right plate 774 is a plate-like member having a substantially rectangular shape in a side view extending downward from the right edge of the top plate 772. The rear plate 776 is a plate-like member having a substantially rectangular shape in front view that constitutes the front surface of the casing 771, and a suction opening (not shown) is formed almost entirely. The front plate 775 is a plate-like member that forms a front surface of the casing 771 and has a substantially rectangular shape when viewed from the front. The air taken into the casing 771 through the suction openings formed on the rear surface and the left side surface of the casing 771 to the outside. A blowout opening 775a for blowing out is formed. The bottom plate 777 is a plate-like member having a substantially rectangular shape in plan view constituting the bottom surface of the casing 771, and also has a function as a drain pan that receives drain water generated in the evaporator 706 and drains it out of the casing 771. .

And the evaporator 706 consists of the heat exchanger panel formed in the planar view L shape along the left side surface and rear surface of the casing 771 in this embodiment, and was comprised by the heat exchanger tube and many heat-transfer fins. A cross fin type fin-and-tube heat exchanger is used. In the present embodiment, the drain heater 797 is disposed below the evaporator 706 and is integrated with the evaporator 706 on the bottom plate 777. More specifically, the drain heater 797 is integrated with the evaporator 706 by sharing the heat transfer fins, and the lowermost path (here, the heat in the heat exchanger panel in which both are integrated). It constitutes a heat transfer channel comprising a lowermost heat transfer tube in the exchanger panel and a heat transfer tube directly above it (see FIG. 3). The blower fan 740 is disposed on the front side of the heat exchanger panel in which the evaporator 706 and the drain heater 797 are integrated, facing the blowout opening 775a of the top plate 772. In the present embodiment, the blower fan 740 is an axial fan, sucks air as a heat source from the blowout opening 775a of the front plate 775 into the casing 771, and passes through the evaporator 706 and the drain heater 797. The air can be blown forward from the blowout opening 775a. That is, the blower fan 740 supplies air as a heat source to the heat exchanger panel including the evaporator 706. The external shape of the heat pump unit 701 and the type of the heat exchanger panel in which the evaporator 706 and the drain heater 797 are integrated are not limited to those described above.

Thus, in the heat pump unit 701 (refrigeration apparatus) of the present embodiment, the two-stage compression type compression mechanism 702 is adopted, and the refrigerant (that is, the refrigeration) sucked into the compression element 702d on the rear stage side of the compression mechanism 702. A drain heater 797 that heats drain water generated in the evaporator 706 by an intermediate pressure refrigerant in the cycle is used.
Further, the heat pump unit 701 has a control unit that controls the operation of each part constituting the heat pump unit 701 such as the compression mechanism 702, the water circulation pump 779, the expansion mechanism 5, and the blower fan 740, although not shown here.
(2) Operation of Heat Pump Unit Next, the operation of the heat pump unit 701 of the present embodiment will be described with reference to FIGS. 1 and 4 to 6. Here, FIG. 4 is a diagram showing the refrigerant flow in the heat pump unit 701, FIG. 5 is a pressure-enthalpy diagram illustrating the refrigeration cycle, and FIG. 6 is a temperature diagram illustrating the refrigeration cycle. -Entropy diagram. The operation control described below is performed by the above-described control unit (not shown). In the following description, “high pressure” means high pressure in the refrigeration cycle (that is, pressure at points D, D ′, and E in FIGS. 5 and 6), and “low pressure” means low pressure in the refrigeration cycle ( That is, it means a pressure at points A and F in FIGS. 5 and 6, and “intermediate pressure” means an intermediate pressure in the refrigeration cycle (that is, pressure at points B and C2 in FIGS. 5 and 6). .

During the operation of the heat pump unit 701, the opening degree of the expansion mechanism 5 is adjusted, and the water circulation pump 779 and the blower fan 740 are rotationally driven. In the state of the refrigerant circuit 710, the low-pressure refrigerant (see point A in FIGS. 1, 4, 5, and 6) is sucked into the compression mechanism 2 from the suction pipe 2a, and first reaches the intermediate pressure by the compression element 2c. After being compressed, the refrigerant is discharged into the intermediate refrigerant pipe 8 (see point B in FIGS. 1, 4, 5, and 6). The intermediate-pressure refrigerant discharged from the preceding-stage compression element 702c is cooled by exchanging heat with drain water generated in the evaporator 706 and flowing down the evaporator 706 in the drain heater 797 (FIG. 1, point C2 in FIGS. 4, 5, and 6). The refrigerant cooled in the drain heater 797 is sucked into the compression element 702d connected to the downstream side of the compression element 702c, further compressed, and discharged from the compression mechanism 702 to the discharge pipe 702b (FIGS. 1 and 2). 4, see point D in FIGS. Here, the high-pressure refrigerant discharged from the compression mechanism 702 is compressed to a pressure exceeding the critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIG. 5) by the two-stage compression operation by the compression elements 702c and 702d. Has been. The high-pressure refrigerant discharged from the compression mechanism 702 flows into the oil separator 741a constituting the oil separation mechanism 741, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the oil separator 741a flows into the oil return pipe 741b constituting the oil separation mechanism 741, and is compressed after being reduced in pressure by the pressure reduction mechanism 741c provided in the oil return pipe 741b. The air is returned to the suction pipe 702a of the mechanism 702 and sucked into the compression mechanism 702 again. Next, the high-pressure refrigerant after the refrigerating machine oil is separated in the oil separation mechanism 741 is sent to the water refrigerant heat exchanger 704 that functions as a refrigerant radiator through the check mechanism 742. The high-pressure refrigerant sent to the water refrigerant heat exchanger 704 exchanges heat with water (feed water) supplied from a hot water storage unit (not shown) by the water circulation pump 779 in the water refrigerant heat exchanger 704. It is cooled (see point E in FIGS. 1, 4, 5 and 6). Then, the high-pressure refrigerant cooled in the water-refrigerant heat exchanger 704 is decompressed by the expansion mechanism 5 to become a low-pressure gas-liquid two-phase refrigerant and sent to the evaporator 706 (FIGS. 1, 4, and 5). , See point F in FIG. 6). The low-pressure gas-liquid two-phase refrigerant sent to the evaporator 706 is heated and exchanged with air as a heating source supplied by the blower fan 740 to evaporate (FIG. 1). FIG. 4, FIG. 5, and FIG. 6 (see point A). In addition, moisture in the air cooled by the heat exchanger with the refrigerant in the evaporator 706 is condensed to become drain water, and adheres to the surfaces of the heat transfer tubes and heat transfer fins of the evaporator 706. This drain water flows down the surface of the heat transfer tubes and heat transfer fins of the evaporator 706, passes through the drain heater 797, and is received by the bottom plate 777 functioning as a drain pan. Then, the low-pressure refrigerant heated in the evaporator 706 is again sucked into the compression mechanism 702. In this way, the operation of the heat pump unit 701 is performed.

As described above, in the heat pump unit 701 (refrigeration apparatus) of the heat pump type water heater of the present embodiment, the two-stage compression type compression mechanism 702 is adopted and the refrigerant sucked into the compression element 702d on the rear stage side of the compression mechanism 702. Since the drain heater 797 that heats the drain water generated in the evaporator 706 by the refrigerant (that is, the intermediate pressure refrigerant in the refrigeration cycle) is used, the bottom plate that functions as the evaporator 706 or the drain pan by heating the drain water. By suppressing the freezing and growth of the drain water in 777 and lowering the temperature of the intermediate-pressure refrigerant in the refrigeration cycle (see points B and C2 in FIG. 6), the drain water is reduced by the high-pressure refrigerant in the conventional refrigeration cycle. When using a drain heater for heating (in this case, in FIGS. 5 and 6, Compared with A → Point B → Point D ′ → Point E → Point F), the area corresponding to the area surrounded by connecting points B, D ′, D and C2 in FIG. Energy loss can be reduced. As a result, the heat pump unit 701 not only suppresses freezing and growth of drain water in the evaporator 706 and the bottom plate 777 functioning as a drain pan by heating the drain water generated in the evaporator 706, but also a conventional refrigeration. An increase in energy loss can be suppressed as compared with the case of using a drain heater that heats drain water using a high-pressure refrigerant in the cycle.

In addition, in this embodiment, since the drain heater 797 is disposed at the lower part of the evaporator 706, the drain water is hardly frozen at the lower part of the evaporator 706 where the amount of attached drain water is the largest due to the flow of the drain water. Thus, freezing and growth of drain water in the evaporator 706 can be effectively suppressed.
(3) Modification 1
In the above-described embodiment, the drain heater 797 is disposed at the lower portion of the evaporator 706 (more specifically, the drain heater 797 is disposed at the lower portion and integrated with the evaporator 706 on the bottom plate 777). However, the present invention is not limited to this, and the drain heater 797 may be disposed on the bottom plate 777 that functions as a drain pan.
For example, as shown in FIGS. 7 and 8, the drain heater 797 has a structure composed of a heat transfer tube that does not share heat transfer fins with the evaporator 706, and is disposed so as to contact a bottom plate 777 that functions as a drain pan. it can.

The heat pump unit 701 (refrigeration apparatus) of the heat pump water heater of this modification also employs the two-stage compression type compression mechanism 702 and the refrigerant sucked into the compression element 702d on the rear stage side of the compression mechanism 702 ( That is, the point that the drain heater 797 that heats the drain water generated in the evaporator 706 by the intermediate pressure refrigerant in the refrigeration cycle is the same as that in the above-described embodiment, and thus occurs in the evaporator 706. By heating the drain water, a drain heater that not only suppresses freezing and growth of the drain water in the evaporator 706 and the bottom plate 777 functioning as a drain pan but also heats the drain water with a high-pressure refrigerant in a conventional refrigeration cycle is provided. The increase in energy loss can be suppressed compared with the case of using.
In addition, in this modified example, the drain heater 797 is disposed on the bottom plate 777 that functions as a drain pan, so that the drain water that flows down from the evaporator 706 and accumulates on the bottom plate 777 that functions as a drain pan is difficult to freeze. Thus, the freezing and growth of drain water in the bottom plate 777 functioning as a drain pan can be effectively suppressed.

(4) Modification 2
In the above-described embodiment and its modifications, the drain heater 797 is either disposed at the bottom of the evaporator 706 or is disposed on the bottom plate 777 that functions as a drain pan. The bottom plate 777 and the bottom plate 777 functioning as a drain pan may be disposed.
For example, as shown in FIGS. 9 to 11, the drain heater 797 includes a first drain heater 797 a disposed at the lower part of the evaporator 706 and a second drain heater disposed on a bottom plate 777 as a drain pan. 797b, and the first drain heater 797a and the second drain heater 797b are connected in parallel (see FIG. 9), or the first drain heater 797a and the second drain heater 797b are connected in series. Can be connected (see FIG. 10). In FIG. 10, the second drain heater 797b is connected downstream of the first drain heater 797a, but the first drain heater 797a is connected downstream of the second drain heater 797b. Also good.

In the heat pump unit 701 (refrigeration apparatus) of the heat pump type hot water heater of this modification, the two-stage compression type compression mechanism 702 is adopted and the refrigerant (702) that is sucked into the compression element 702d on the rear side of the compression mechanism 702 ( That is, the drain heater 797 (here, the first drain heater 797a and the second drain heater 797b) that heats the drain water generated in the evaporator 706 by the intermediate pressure refrigerant in the refrigeration cycle is used. Is the same as that of the above-described embodiment and the modification thereof, so that the drain water generated in the evaporator 706 is heated to suppress freezing and growth of the drain water in the evaporator 706 and the bottom plate 777 functioning as a drain pan. The drain water is heated by the high-pressure refrigerant in the conventional refrigeration cycle. Compared to using emissions heater, it is possible to suppress an increase in energy loss.

In addition, in this modification, the drain heater 797 includes a first drain heater 797a disposed at the lower portion of the evaporator 706 and a second drain heater 797b disposed on the bottom plate 777 functioning as a drain pan. Therefore, the drain water is hard to freeze in the lower part of the evaporator 797 where the drain water adheres most when the drain water flows, and the drain water that flows down from the evaporator 706 and collects in the bottom plate 777 that functions as a drain pan This makes it difficult to freeze, thereby effectively suppressing both freezing and growth of drain water in the evaporator 706 and freezing and growth of drain water in the bottom plate 777 functioning as a drain pan.
(5) Modification 3
In the above-described modification 2, the drain heater 797 (more specifically, the first drain heater 797a and the second drain heater 797b) is provided below the evaporator 706 and the bottom plate 777 that functions as a drain pan. The refrigerant that is disposed on both sides and that is discharged from the compression element 702c on the front stage side and sucked into the compression element 702d on the rear stage side flows into both the drain heaters 797a and 797b. You may be comprised so that it can be made to flow into any one of the apparatus 797a and the 2nd drain heater 797b.

For example, as shown in FIG. 12, in a configuration in which a first drain heater 797a and a second drain heater 797b are connected in parallel, the first drain that restricts the flow of refrigerant to the first drain heater 797a. A drain heater switching mechanism 798 including a heater on / off valve 798a and a second drain heater on / off valve 798b that restricts the flow of refrigerant to the second drain heater 797b can be provided. Further, as shown in FIG. 13, in the configuration in which the first drain heater 797a and the second drain heater 797b are connected in series, the first drain heater bypass for bypassing the first drain heater 797a. A pipe 799a, a first drain heater on / off valve 798a for limiting the flow of refrigerant to the first drain heater 797a, a second drain heater bypass pipe 799b for bypassing the second drain heater 797b, A drain heater switching mechanism 798 including a second drain heater opening / closing valve 798b that restricts the flow of refrigerant to the two-drain heater 797b can be provided. Here, the first drain heater bypass on / off valve 799c and the second drain heater bypass on / off valve 799d are provided in the first drain heater bypass pipe 799a and the second drain heater bypass pipe 799b, respectively. In this modification, the on-off valves 798a, 798b, 799c, and 799d are electromagnetic valves. Moreover, you may comprise the structure shown by FIG.12 and FIG.13 using a three-way valve etc. instead of a solenoid valve.

And in the heat pump unit 701 (refrigeration apparatus) of the heat pump type hot water heater of this modification, while being able to acquire the same effect as the above-mentioned modification 2, the 1st drain heater 797a and the 2nd drain heater Since a drain heater switching mechanism 798 that enables switching to 797b is further provided, only one of the first drain heater 797a and the second drain heater 797b can be used as necessary. .
-Second Embodiment-
(1) Configuration of Air Conditioner FIG. 14 is a schematic configuration diagram of an air conditioner 1 as a second embodiment of the refrigeration apparatus according to the present invention. The air conditioner 1 has a refrigerant circuit 10 configured to be capable of switching between a cooling operation and a heating operation, and uses a refrigerant (here, carbon dioxide) that operates in a supercritical region to perform a two-stage compression refrigeration cycle. It is a device to perform.

The refrigerant circuit 10 of the air conditioner 1 mainly includes a compression mechanism 2, a switching mechanism 3, a heat source side heat exchanger 4, a bridge circuit 17, a receiver 18, a first expansion mechanism 5a, and a second expansion mechanism. 5b, a use side heat exchanger 6, an intermediate heat exchanger 7, and a drain heater 97.
In the present embodiment, the compression mechanism 2 includes a compressor 21 that compresses a refrigerant in two stages with two compression elements. The compressor 21 has a sealed structure in which a compressor drive motor 21b, a drive shaft 21c, and compression elements 2c and 2d are accommodated in a casing 21a. The compressor drive motor 21b is connected to the drive shaft 21c. The drive shaft 21c is connected to the two compression elements 2c and 2d. That is, in the compressor 21, two compression elements 2c and 2d are connected to a single drive shaft 21c, and the two compression elements 2c and 2d are both rotationally driven by the compressor drive motor 21b. It has a stage compression structure. The compression elements 2c and 2d are positive displacement compression elements such as a rotary type and a scroll type in the present embodiment. The compressor 21 sucks the refrigerant from the suction pipe 2a, compresses the sucked refrigerant by the compression element 2c, discharges the refrigerant to the intermediate refrigerant pipe 8, and discharges the refrigerant discharged to the intermediate refrigerant pipe 8 to the compression element 2d. And the refrigerant is further compressed and then discharged to the discharge pipe 2b. Here, the intermediate refrigerant pipe 8 sucks the intermediate-pressure refrigerant in the refrigeration cycle discharged from the compression element 2c connected to the front stage side of the compression element 2d into the compression element 2d connected to the rear stage side of the compression element 2c. It is a refrigerant pipe for making it. The discharge pipe 2b is a refrigerant pipe for sending the refrigerant discharged from the compression mechanism 2 to the switching mechanism 3. The discharge pipe 2b is provided with an oil separation mechanism 41 and a check mechanism 42. The oil separation mechanism 41 is a mechanism that separates the refrigeration oil accompanying the refrigerant discharged from the compression mechanism 2 from the refrigerant and returns it to the suction side of the compression mechanism 2, and is mainly accompanied by the refrigerant discharged from the compression mechanism 2. An oil separator 41 a that separates the refrigeration oil from the refrigerant, and an oil return pipe 41 b that is connected to the oil separator 41 a and returns the refrigeration oil separated from the refrigerant to the suction pipe 2 a of the compression mechanism 2. The oil return pipe 41b is provided with a pressure reducing mechanism 41c for reducing the pressure of the refrigerating machine oil flowing through the oil return pipe 41b. In the present embodiment, a capillary tube is used as the decompression mechanism 41c. The check mechanism 42 is a mechanism for allowing the refrigerant flow from the discharge side of the compression mechanism 2 to the switching mechanism 3 and blocking the refrigerant flow from the switching mechanism 3 to the discharge side of the compression mechanism 2. In this embodiment, a check valve is used.

Thus, in this embodiment, the compression mechanism 2 has the two compression elements 2c and 2d, and the refrigerant discharged from the compression element on the front stage of these compression elements 2c and 2d is returned to the rear stage side. The compression elements are sequentially compressed by the compression elements.
The switching mechanism 3 is a mechanism for switching the flow direction of the refrigerant in the refrigerant circuit 10, and is used as a radiator for the refrigerant compressed by the compression mechanism 2 and used in the cooling operation during the cooling operation. In order for the side heat exchanger 6 to function as an evaporator of the refrigerant cooled in the heat source side heat exchanger 4, the discharge side of the compression mechanism 2 and one end of the heat source side heat exchanger 4 are connected and the compressor 21 The suction side and the use side heat exchanger 6 are connected (refer to the solid line of the switching mechanism 3 in FIG. 14; hereinafter, the state of the switching mechanism 3 is referred to as “cooling operation state”). In order for the exchanger 6 to function as a radiator for the refrigerant compressed by the compression mechanism 2 and for the heat source side heat exchanger 4 to function as an evaporator for the refrigerant cooled in the utilization side heat exchanger 6, Discharge side and use side heat exchanger 6 And the suction side of the compression mechanism 2 and one end of the heat source side heat exchanger 4 can be connected (see the broken line of the switching mechanism 3 in FIG. "Heating operation state"). In the present embodiment, the switching mechanism 3 is a four-way switching valve connected to the suction side of the compression mechanism 2, the discharge side of the compression mechanism 2, the heat source side heat exchanger 4, and the use side heat exchanger 6. The switching mechanism 3 is not limited to a four-way switching valve, and is configured to have a function of switching the refrigerant flow direction as described above, for example, by combining a plurality of electromagnetic valves. There may be.

Thus, when the switching mechanism 3 pays attention only to the compression mechanism 2, the heat source side heat exchanger 4 and the use side heat exchanger 6 constituting the refrigerant circuit 10, the compression mechanism 2, the heat source side that functions as a refrigerant radiator. The cooling operation state in which the refrigerant is circulated in the order of the heat exchanger 4 and the use side heat exchanger 6 that functions as the refrigerant evaporator, the compression mechanism 2, the use side heat exchanger 6 that functions as the refrigerant radiator, and the evaporation of the refrigerant It is comprised so that the heating operation state which circulates a refrigerant | coolant in order of the heat source side heat exchanger 4 which functions as a heater can be switched.
The heat source-side heat exchanger 4 is a heat exchanger that functions as a refrigerant radiator or evaporator using air as a heat source. One end of the heat source side heat exchanger 4 is connected to the switching mechanism 3, and the other end is connected to the first expansion mechanism 5 a via the bridge circuit 17. The air as the heat source of the heat source side heat exchanger 4 is supplied by the heat source side fan 40. The heat source side fan 40 is rotationally driven by a fan drive motor 740a.

The bridge circuit 17 is provided between the heat source side heat exchanger 4 and the use side heat exchanger 6, and is connected to a receiver inlet pipe 18 a connected to the inlet of the receiver 18 and an outlet of the receiver 18. It is connected to the receiver outlet pipe 18b. In the present embodiment, the bridge circuit 17 has four check valves 17a, 17b, 17c, and 17d. The inlet check valve 17a is a check valve that only allows the refrigerant to flow from the heat source side heat exchanger 4 to the receiver inlet pipe 18a. The inlet check valve 17b is a check valve that allows only the refrigerant to flow from the use side heat exchanger 6 to the receiver inlet pipe 18a. That is, the inlet check valves 17a and 17b have a function of circulating the refrigerant from one of the heat source side heat exchanger 4 and the use side heat exchanger 6 to the receiver inlet pipe 18a. The outlet check valve 17 c is a check valve that allows only the refrigerant to flow from the receiver outlet pipe 18 b to the use side heat exchanger 6. The outlet check valve 17d is a check valve that allows only the refrigerant to flow from the receiver outlet pipe 18b to the heat source side heat exchanger 4. That is, the outlet check valves 17c and 17d have a function of circulating the refrigerant from the receiver outlet pipe 18b to the other of the heat source side heat exchanger 4 and the use side heat exchanger 6.

The first expansion mechanism 5a is a mechanism that depressurizes the refrigerant provided in the receiver inlet pipe 18a, and an electric expansion valve is used in the present embodiment. In the present embodiment, during the cooling operation, the first expansion mechanism 5a saturates the refrigerant before sending the high-pressure refrigerant cooled in the heat source side heat exchanger 4 to the use side heat exchanger 6 via the receiver 18. The pressure is reduced to near the pressure, and during the heating operation, the high-pressure refrigerant cooled in the use side heat exchanger 6 is reduced to near the saturation pressure of the refrigerant before being sent to the heat source side heat exchanger 4 via the receiver 18.
The receiver 18 is depressurized by the first expansion mechanism 5a so as to be able to store surplus refrigerant generated according to the operating state such as the refrigerant circulation amount in the refrigerant circuit 10 is different between the cooling operation and the heating operation. The inlet is connected to the receiver inlet pipe 18a, and the outlet thereof is connected to the receiver outlet pipe 18b. The receiver 18 also has a first suction return pipe that can extract the refrigerant from the receiver 18 and return it to the suction pipe 2a of the compression mechanism 2 (that is, the suction side of the compression element 2c on the front stage side of the compression mechanism 2). 18f is connected. The first suction return pipe 18f is provided with a first suction return on / off valve 18g. The first suction return on / off valve 18g is an electromagnetic valve in the present embodiment.

The second expansion mechanism 5b is a mechanism that depressurizes the refrigerant provided in the receiver outlet pipe 18b, and an electric expansion valve is used in the present embodiment. In the present embodiment, the second expansion mechanism 5b is at a low pressure in the refrigeration cycle before the refrigerant decompressed by the first expansion mechanism 5a is sent to the use-side heat exchanger 6 via the receiver 18 during the cooling operation. In the heating operation, the refrigerant decompressed by the first expansion mechanism 5a is further depressurized until it reaches a low pressure in the refrigeration cycle before being sent to the heat source side heat exchanger 4 via the receiver 18.
The use side heat exchanger 6 is a heat exchanger that functions as a refrigerant evaporator or a radiator. One end of the use side heat exchanger 6 is connected to the first expansion mechanism 5 a via a bridge circuit, and the other end is connected to the switching mechanism 3. Although not shown here, the use side heat exchanger 6 is supplied with water and air as a heat source for exchanging heat with the refrigerant flowing through the use side heat exchanger 6.

Thus, in the present embodiment, when the switching mechanism 3 is in the cooling operation state by the bridge circuit 17, the receiver 18, the receiver inlet pipe 18a, and the receiver outlet pipe 18b, the heat source side heat exchanger 4 is cooled. The high-pressure refrigerant is supplied to the inlet check valve 17a of the bridge circuit 17, the first expansion mechanism 5a of the receiver inlet pipe 18a, the second expansion mechanism 5b of the receiver 18, the receiver outlet pipe 18b, and the outlet check valve 17c of the bridge circuit 17. It can be sent to the use side heat exchanger 6 through. Further, when the switching mechanism 3 is in the heating operation state, the high-pressure refrigerant cooled in the use-side heat exchanger 6 is converted into the first expansion mechanism of the inlet check valve 17b of the bridge circuit 17 and the receiver inlet pipe 18a. 5a, the receiver 18, the second expansion mechanism 5b of the receiver outlet pipe 18b, and the outlet check valve 17d of the bridge circuit 17 can be sent to the heat source side heat exchanger 4.

The intermediate heat exchanger 7 is provided in the intermediate refrigerant pipe 8. In the present embodiment, the intermediate heat exchanger 7 functions as a refrigerant cooler that is discharged from the preceding compression element 2c and sucked into the compression element 2d during the cooling operation. It is a heat exchanger that can. The intermediate heat exchanger 7 is a heat exchanger that uses air as a heat source (here, a cooling source), and is integrated with the heat source side heat exchanger 4 in this embodiment. Thus, the intermediate heat exchanger 7 can be said to be a heat exchanger using an external heat source in the sense that it does not use the refrigerant circulating in the refrigerant circuit 10.
An intermediate heat exchanger bypass pipe 9 is connected to the intermediate refrigerant pipe 8 so as to bypass the intermediate heat exchanger 7. The intermediate heat exchanger bypass pipe 9 is a refrigerant pipe that limits the flow rate of the refrigerant flowing through the intermediate heat exchanger 7. The intermediate heat exchanger bypass pipe 9 is provided with an intermediate heat exchanger bypass opening / closing valve 11. The intermediate heat exchanger bypass on-off valve 11 is a solenoid valve in the present embodiment. In the present embodiment, the intermediate heat exchanger bypass on-off valve 11 is basically closed when the switching mechanism 3 is in the cooling operation state and controlled to be opened when the switching mechanism 3 is in the heating operation state. Made. That is, the intermediate heat exchanger bypass on-off valve 11 is controlled to be closed when performing the cooling operation and to be opened when performing the heating operation.

Further, the intermediate refrigerant pipe 8 has an intermediate portion between the connecting portion of the intermediate heat exchanger bypass pipe 9 and the compression element 2c side end on the front stage side to the compression element 2c side end on the front stage side of the intermediate heat exchanger 7. A heat exchanger on / off valve 12 is provided. The intermediate heat exchanger on / off valve 12 is a mechanism that limits the flow rate of the refrigerant flowing through the intermediate heat exchanger 7. The intermediate heat exchanger on / off valve 12 is an electromagnetic valve in the present embodiment. In the present embodiment, the intermediate heat exchanger on / off valve 12 is basically controlled to be opened when the switching mechanism 3 is in the cooling operation state and closed when the switching mechanism 3 is in the heating operation state. The That is, the intermediate heat exchanger on / off valve 12 is controlled to be opened when the cooling operation is performed and closed when the heating operation is performed.
The intermediate refrigerant pipe 8 allows the refrigerant to flow from the discharge side of the upstream compression element 2c to the suction side of the downstream compression element 2d, and from the suction side of the downstream compression element 2d to the upstream side. A check mechanism 15 is provided for blocking the flow of the refrigerant to the discharge side of the compression element 2c on the side. The check mechanism 15 is a check valve in the present embodiment. In the present embodiment, the check mechanism 15 is connected to the compression element 2d side end of the intermediate heat exchanger bypass pipe 9 from the compression element 2d side end of the intermediate heat exchanger 7 on the rear stage side. It is provided in the part to the connection part.

The drain heater 97 is a drain that is generated in the heat source side heat exchanger 4 that functions as an evaporator of the refrigerant by the refrigerant discharged from the front-stage compression element 2c and sucked into the rear-stage compression element 2d during the heating operation. It is a heat exchanger capable of heating water, and in this embodiment, the intermediate heat exchanger bypass pipe 9 (more specifically, the compression element 2c side end on the front stage side of the intermediate heat exchanger bypass pipe 9 and To the intermediate heat exchanger bypass opening / closing valve 11). The drain heater 97 is disposed below the heat source side heat exchanger 4.
Next, with respect to a configuration in which the intermediate heat exchanger 7 is integrated with the heat source side heat exchanger 4 and a configuration in which the drain heater 97 is disposed below the heat source side heat exchanger 4, FIGS. It explains using. Here, FIG. 15 is an external perspective view of the heat source unit 1a (with the fan grill removed), and FIG. 16 is a side view of the heat source unit 1a with the right plate 74 of the heat source unit 1a removed. In the following description, “left” and “right” are based on the case where the heat source unit 1a is viewed from the front plate 75 side.

First, in this embodiment, the air conditioner 1 mainly includes a heat source unit 1a provided with a heat source side fan 40, a heat source side heat exchanger 4, an intermediate heat exchanger 7 and a drain heater 97, and mainly a use side heat exchange. It is comprised by connecting with the utilization unit (not shown) in which the container 6 was provided. The heat source unit 1a is a so-called top-blowing type that sucks air from the side and blows it upward. It has refrigerant circuit components such as the exchanger 4, the intermediate heat exchanger 7 and the drain heater 97, and devices such as the heat source side fan 40.
In the present embodiment, the casing 71 is a substantially rectangular parallelepiped box, and mainly includes a top plate 72 constituting the top surface of the casing 71, a left plate 73, a right plate 74 constituting the outer peripheral surface of the casing 71, and the front. The plate 75 and the rear plate 76 and a bottom plate 77 are included. The top plate 72 is a member mainly constituting the top surface of the casing 71. In the present embodiment, the top plate 72 is a plate-like member having a substantially rectangular shape in a plan view in which the blowing opening 71a is formed at a substantially center. The top plate 72 is provided with a fan grill 78 so as to cover the blowout opening 71a from above. The left plate 73 is a member that mainly constitutes the left surface of the casing 71. In the present embodiment, the left plate 73 is a plate-like member that is substantially rectangular in a side view extending downward from the left edge of the top plate 72. The left plate 73 is formed with a suction opening 73a almost entirely except the upper part. The right plate 74 is a member that mainly constitutes the right surface of the casing 71. In the present embodiment, the right plate 74 is a plate-like member that is substantially rectangular in a side view extending downward from the right edge of the top plate 72. The right plate 74 is formed with a suction opening 74a almost entirely except the upper part. The front plate 75 is a member that mainly constitutes the front surface of the casing 71. In the present embodiment, the front plate 75 is configured by a plate-like member having a substantially rectangular shape when viewed from the front edge of the top plate 72 in order downward. ing. The rear plate 76 is a member that mainly constitutes the rear surface of the casing 71. In the present embodiment, the rear plate 76 is configured by a substantially rectangular plate-like member that is disposed in order from the rear edge of the top plate 72 in a downward direction. ing. The rear plate 76 is formed with a suction opening 76a in almost the whole except the upper part. The bottom plate 77 is a member that mainly constitutes the bottom surface of the casing 71. In the present embodiment, the bottom plate 77 is a plate-like member having a substantially rectangular shape in plan view. The bottom plate 77 also has a function as a drain pan that receives drain water generated in the heat source side heat exchanger 4 and drains it out of the casing 71.

The intermediate heat exchanger 7 is integrated with the heat source side heat exchanger 4 in a state of being arranged on the upper side of the heat source side heat exchanger 4, and is arranged on the bottom plate 77. More specifically, the heat source side heat exchanger 4 uses a cross fin type fin-and-tube heat exchanger composed of heat transfer tubes and a large number of heat transfer fins, and is an intermediate heat exchanger. 7 is integrated with the heat source side heat exchanger 4 by sharing heat transfer fins. In addition, in the present embodiment, the heat source side heat exchanger 4 and the intermediate heat exchanger 7 are integrated to form a heat exchanger panel having a substantially U shape in plan view, and suction openings 73a and 74a. , 76a. The heat source side fan 40 is disposed on the upper side of the heat source side heat exchanger 4 and the intermediate heat exchanger 7 that are opposed to the blowout opening 71a of the top plate 72. In the present embodiment, the heat source side fan 40 is an axial fan, and is rotationally driven by the fan drive motor 40a, thereby sucking air as a heat source into the casing 71 from the suction openings 73a, 74a, and 76a. After passing through the heat exchanger 4 and the intermediate heat exchanger 7, the air can be blown upward from the blowout opening 71 a (see the arrows indicating the air flow in FIG. 16). That is, the heat source side fan 40 supplies air as a heat source to both the heat source side heat exchanger 4 and the intermediate heat exchanger 7. Further, in the present embodiment, the drain heater 97 is disposed below the heat source side heat exchanger 4 and is integrated with the heat source side heat exchanger 4 by sharing heat transfer fins on the bottom plate 77. Yes. The drain heater 97 is a lowermost path in the heat exchanger panel integrated with the intermediate heat exchanger 7 and the heat source side heat exchanger 4 (that is, the lowermost heat transfer tube in the heat exchanger panel and the heat transfer tube immediately above it). (Refer to FIG. 16). Further, the intermediate heat exchanger 7 has a larger heat transfer area than the drain heater 97. The external shape of the heat source unit 1a and the shape of the heat source side heat exchanger 4, the intermediate heat exchanger 7, and the drain heater 97 integrated with each other are not limited to those described above.

As described above, in the air conditioner 1 of the present embodiment, the two-stage compression type compression mechanism 2 is mainly employed, and at the time of the cooling operation in which the switching mechanism 3 is in the cooling operation state, An intermediate heat exchanger 7 that functions as a cooler for the refrigerant sucked into the compression element 2d (that is, the intermediate-pressure refrigerant in the refrigeration cycle) is provided, and during the heating operation in which the switching mechanism 3 is in the heating operation state, the refrigerant A drain heater 97 is provided for heating the drain water generated in the heat source side heat exchanger 4 functioning as an evaporator.
Furthermore, although not shown here, the air conditioner 1 includes a compression mechanism 2, a switching mechanism 3, expansion mechanisms 5a and 5b, an intermediate heat exchanger bypass opening / closing valve 11, an intermediate heat exchanger opening / closing valve 12, a first suction return opening / closing valve. It has a control part which controls operation of each part which constitutes air harmony device 1 such as valve 18g and heat source side fan 40.

(2) Operation of Air Conditioner Next, the operation of the air conditioner 1 of the present embodiment will be described with reference to FIGS. 14 and 17 to 22. Here, FIG. 17 is a diagram showing the flow of the refrigerant in the air conditioner 1 during the cooling operation, and FIG. 18 is a pressure-enthalpy diagram illustrating the refrigeration cycle during the cooling operation. FIG. 20 is a temperature-entropy diagram illustrating a refrigeration cycle during cooling operation, FIG. 20 is a diagram illustrating a refrigerant flow in the air conditioner 1 during heating operation, and FIG. 21 is a diagram during heating operation. FIG. 22 is a pressure-enthalpy diagram illustrating the refrigeration cycle, and FIG. 22 is a temperature-entropy diagram illustrating the refrigeration cycle during the heating operation. Note that operation control in the following cooling operation and heating operation is performed by the above-described control unit (not shown). In the following description, “high pressure” means high pressure in the refrigeration cycle (that is, pressure at points D, D ′, and E in FIGS. 18 and 19 and pressure at points D, D ′, and F in FIGS. 21 and 22). “Low pressure” means low pressure in the refrigeration cycle (that is, pressure at points A and F in FIGS. 18 and 19 and pressure at points A and E in FIGS. 21 and 22), and “intermediate pressure” Means intermediate pressure in the refrigeration cycle (that is, pressure at points B and C1 in FIGS. 18 and 19 and pressure at points B and C2 in FIGS. 21 and 22).

<Cooling operation>
During the cooling operation, the switching mechanism 3 is in the cooling operation state indicated by the solid lines in FIGS. The opening degree of the first expansion mechanism 5a and the second expansion mechanism 5b is adjusted. Since the switching mechanism 3 is in the cooling operation state, the intermediate heat exchanger on / off valve 12 of the intermediate refrigerant pipe 8 is opened, and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is closed. As a result, the intermediate heat exchanger 7 is brought into a state of functioning as a cooler, and the refrigerant is not allowed to flow into the drain heater 97.
In the state of the refrigerant circuit 10, a low-pressure refrigerant (see point A in FIGS. 14 and 17 to 19) is sucked into the compression mechanism 2 from the suction pipe 2a and first compressed to an intermediate pressure by the compression element 2c. Thereafter, the refrigerant is discharged into the intermediate refrigerant pipe 8 (see point B in FIGS. 14 and 17 to 19). The intermediate-pressure refrigerant discharged from the upstream-side compression element 2c is cooled by exchanging heat with air as a cooling source supplied by the heat-source-side fan 40 in the intermediate heat exchanger 7 (FIG. 14). FIG. 17 to FIG. 19 (see point C1). The refrigerant cooled in the intermediate heat exchanger 7 is then sucked into the compression element 2d connected to the rear stage side of the compression element 2c, further compressed, and discharged from the compression mechanism 2 to the discharge pipe 2b ( (Refer to point D in FIGS. 14 and 17-19). Here, the high-pressure refrigerant discharged from the compression mechanism 2 is compressed to a pressure exceeding the critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIG. 18) by the two-stage compression operation by the compression elements 2c and 2d. Has been. The high-pressure refrigerant discharged from the compression mechanism 2 flows into the oil separator 41a constituting the oil separation mechanism 41, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the oil separator 41a flows into the oil return pipe 41b constituting the oil separation mechanism 41, and is compressed after being reduced in pressure by the pressure reduction mechanism 41c provided in the oil return pipe 41b. It is returned to the suction pipe 2a of the mechanism 2 and again sucked into the compression mechanism 2. Next, the high-pressure refrigerant after the refrigerating machine oil is separated in the oil separation mechanism 41 is sent to the heat source side heat exchanger 4 functioning as a refrigerant radiator through the check mechanism 42 and the switching mechanism 3. The high-pressure refrigerant sent to the heat source side heat exchanger 4 is cooled by exchanging heat with air as a cooling source supplied by the heat source side fan 40 in the heat source side heat exchanger 4 (FIG. 14). FIG. 17 to FIG. 19 (see point E). Then, the high-pressure refrigerant cooled in the heat source side heat exchanger 4 flows into the receiver inlet pipe 18a through the inlet check valve 17a of the bridge circuit 17 and is reduced to near the saturation pressure by the first expansion mechanism 5a. (See point I in FIGS. 14 and 17). Then, the refrigerant stored in the receiver 18 is sent to the receiver outlet pipe 18b and is reduced in pressure by the second expansion mechanism 5b to become a low-pressure gas-liquid two-phase refrigerant, and the outlet check valve 17c of the bridge circuit 17 is used. And is sent to the use side heat exchanger 6 functioning as a refrigerant evaporator (see point F in FIGS. 14 and 17 to 19). Then, the low-pressure gas-liquid two-phase refrigerant sent to the use-side heat exchanger 6 is heated by heat exchange with water or air as a heating source to evaporate (FIG. 14, FIG. 17 to point 19 in FIG. 19). Then, the low-pressure refrigerant heated in the use side heat exchanger 6 is again sucked into the compression mechanism 2 via the switching mechanism 3. In this way, the cooling operation is performed.

Thus, in the air conditioning apparatus 1 (refrigeration apparatus) of the present embodiment, the intermediate refrigerant pipe that employs the two-stage compression type compression mechanism 702 and sucks the refrigerant discharged from the compression element 2c into the compression element 2d. 8 is provided with an intermediate heat exchanger 7, and in the cooling operation, the intermediate heat exchanger on / off valve 12 is opened and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is closed to Since the exchanger 7 is in a state of functioning as a cooler, the intermediate heat exchanger 7 is not provided (in this case, in FIGS. 18 and 19, point A → point B → point D ′ → point E (Refer to the refrigeration cycle in the order of point F), the temperature of the refrigerant sucked into the compression element 2d on the rear stage side of the compression element 2c decreases (see points B and C1 in FIG. 19), and the compression element 2d The temperature of the refrigerant discharged from the tank also decreases It becomes Rukoto (D, D 'reference point in FIG. 19). For this reason, in this air conditioning apparatus 1, compared with the case where the intermediate heat exchanger 7 is not provided in the heat source side heat exchanger 4 that functions as a refrigerant radiator, water or air as a cooling source and the refrigerant The temperature difference can be reduced, and the heat dissipation loss corresponding to the area surrounded by connecting the points B1, D ′, D, and C1 in FIG. 19 can be reduced, so that the operation efficiency can be improved. .

<Heating operation>
During the heating operation, the switching mechanism 3 is in the heating operation state indicated by the broken lines in FIGS. The opening degree of the first expansion mechanism 5a and the second expansion mechanism 5b is adjusted. Since the switching mechanism 3 is in a heating operation state, the intermediate heat exchanger on / off valve 12 of the intermediate refrigerant pipe 8 is closed, and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is opened. As a result, the intermediate heat exchanger 7 is brought into a state where it does not function as a cooler, and the refrigerant flows into the drain heater 97.
In the state of the refrigerant circuit 10, low-pressure refrigerant (see point A in FIGS. 14 and 20 to 22) is sucked into the compression mechanism 2 from the suction pipe 2a, and is first compressed to an intermediate pressure by the compression element 2c. Thereafter, the refrigerant is discharged into the intermediate refrigerant pipe 8 (see point B in FIGS. 14 and 20 to 22). Unlike the cooling operation, the intermediate-pressure refrigerant discharged from the upstream-side compression element 2c does not pass through the intermediate heat exchanger 7 and is supplied to the drain heater 97 provided in the intermediate heat exchanger bypass pipe 9. In the drain heater 97, cooling is performed by exchanging heat with the drain water generated in the heat source side heat exchanger 4 functioning as a refrigerant evaporator and flowing down the heat source side heat exchanger 4 (FIG. 14, see point C2 in FIGS. The refrigerant cooled in the drain heater 97 is sucked into the compression element 2d connected to the rear stage side of the compression element 2c, further compressed, and discharged from the compression mechanism 2 to the discharge pipe 2b (FIG. 14, FIG. 20 to point D in FIG. 22). Here, the high-pressure refrigerant discharged from the compression mechanism 2 is subjected to the critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIG. 21) by the two-stage compression operation by the compression elements 2c and 2d as in the cooling operation. ) Compressed to a pressure exceeding The high-pressure refrigerant discharged from the compression mechanism 2 flows into the oil separator 41a constituting the oil separation mechanism 41, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the oil separator 41a flows into the oil return pipe 41b constituting the oil separation mechanism 41, and is compressed after being reduced in pressure by the pressure reduction mechanism 41c provided in the oil return pipe 41b. It is returned to the suction pipe 2a of the mechanism 2 and again sucked into the compression mechanism 2. Next, the high-pressure refrigerant after the refrigerating machine oil is separated in the oil separation mechanism 41 is sent to the use side heat exchanger 6 functioning as a refrigerant radiator through the check mechanism 42 and the switching mechanism 3 to be cooled. It is cooled by exchanging heat with water or air as a source (see point F in FIGS. 14 and 20 to 22). The high-pressure refrigerant cooled in the use-side heat exchanger 6 flows into the receiver inlet pipe 18a through the inlet check valve 17b of the bridge circuit 17, and is reduced to near the saturation pressure by the first expansion mechanism 5a. (See point I in FIGS. 14 and 20). Then, the refrigerant stored in the receiver 18 is sent to the receiver outlet pipe 18b and is reduced in pressure by the second expansion mechanism 5b to become a low-pressure gas-liquid two-phase refrigerant, and the outlet check valve 17d of the bridge circuit 17 is supplied. And is sent to the heat source side heat exchanger 4 functioning as a refrigerant evaporator (see point E in FIGS. 14, 20 to 22). The low-pressure gas-liquid two-phase refrigerant sent to the heat source side heat exchanger 4 exchanges heat with air as a heating source supplied by the heat source side fan 40 in the heat source side heat exchanger 4. When heated, it evaporates (see point A in FIGS. 14 and 20 to 22). Then, the low-pressure refrigerant heated and evaporated in the heat source side heat exchanger 4 is again sucked into the compression mechanism 2 via the switching mechanism 3. In this way, the heating operation is performed.

Thus, in the air conditioning apparatus 1 (refrigeration apparatus) of the present embodiment, the intermediate heat exchanger on-off valve 12 is employed in the heating operation in which the two-stage compression type compression mechanism 702 is employed and the switching mechanism 3 is in the heating operation state. Is opened, and the intermediate heat exchanger bypass opening / closing valve 11 is opened to make the intermediate heat exchanger 7 not function as a cooler, and to heat drain water generated in the heat source side heat exchanger 4. Since the apparatus 97 is used, the drain water is heated to suppress freezing and growth of the drain water in the heat source side heat exchanger 4 and the bottom plate 77 functioning as a drain pan, and the temperature of the intermediate pressure refrigerant in the refrigeration cycle is reduced. By lowering (see points B and C2 in FIG. 22), a drain heater that heats drain water with a high-pressure refrigerant in a conventional refrigeration cycle is used. In this case (in this case, the refrigeration cycle is performed in the order of point A → point B → point D ′ → point F → point E in FIGS. 21 and 22), points B and D in FIG. The energy loss corresponding to the area surrounded by connecting ', D and C2 can be reduced. Thus, in the air conditioner 1, during the cooling operation, the intermediate heat exchanger 7 is used to cool the intermediate pressure refrigerant in the refrigeration cycle with the air as the heat source, so that the heat source side heat that functions as a refrigerant radiator is obtained. The heat dissipation loss in the exchanger 4 can be reduced, and during the heating operation, the intermediate pressure refrigerant in the refrigeration cycle is cooled by the drain water as the heat source, so that the drain water 97 can be frozen and grown. In addition to the suppression, an increase in energy loss during the heating operation can be suppressed as compared to the case of using a drain heater that heats drain water using a high-pressure refrigerant in the refrigeration cycle.

In addition, in the present embodiment, since the drain heater 97 is disposed at the lower part of the heat source side heat exchanger 4, in the lower part of the heat source side heat exchanger 4, the amount of attached drain water is the largest due to the flow of drain water. It becomes difficult for the drain water to freeze, and thereby, the freezing and growth of the drain water in the heat source side heat exchanger 4 can be effectively suppressed.
In the present embodiment, since the intermediate heat exchanger 7 has a larger heat transfer area than the drain heater 97, the intermediate pressure refrigerant in the refrigeration cycle can be significantly cooled during the cooling operation. Thus, the heat radiation loss in the heat source side heat exchanger 4 functioning as a heat radiator during the cooling operation can be greatly reduced. On the other hand, with respect to the drain heater 97, the cooling of the intermediate pressure refrigerant in the refrigeration cycle is compared with the degree of cooling of the intermediate pressure refrigerant in the refrigeration cycle by the intermediate heat exchanger 7 (see points B and C1 in FIG. 19). Since the degree (refer to points B and C2 in FIG. 22) is reduced, the heat transfer area is suitable for the purpose of heating the drain water.

In the present embodiment, a refrigerant (in this case, carbon dioxide) that operates in the supercritical region is used as the refrigerant. Therefore, during the cooling operation, the intermediate heat exchanger 7 has a critical pressure Pcp (in the case of carbon dioxide). A refrigerant having an intermediate pressure lower than about 7.3 MPa flows, and a refrigeration cycle in which a high-pressure refrigerant exceeding the critical pressure Pcp flows in the heat source side heat exchanger 4 functioning as a refrigerant radiator ( In this case, as shown in FIG. 23, the physical properties of the refrigerant at a pressure lower than the critical pressure Pcp and the physical properties of the refrigerant at a pressure exceeding the critical pressure Pcp (particularly, thermal conductivity and specific heat at constant pressure). Therefore, the heat transfer coefficient on the refrigerant side of the intermediate heat exchanger 7 tends to be lower than the heat transfer coefficient on the refrigerant side of the heat source side heat exchanger 4 that functions as a heat radiator for the refrigerant. Here, FIG. 23 shows the value of the heat transfer coefficient (heat transfer on the refrigerant side of the intermediate heat exchanger 7) when 6 MPa carbon dioxide flows at a predetermined mass flow rate in a heat transfer channel having a predetermined channel cross-sectional area. And the value of the heat transfer coefficient of carbon dioxide of 10 MPa (corresponding to the heat transfer coefficient on the refrigerant side of the heat source side heat exchanger 4) under the same heat transfer flow path and mass flow rate conditions as those of 6 MPa carbon dioxide. However, when this is seen, in the temperature range (about 40 to 70 ° C.) of the refrigerant flowing in the heat source side heat exchanger 4 and the intermediate heat exchanger 7 functioning as a refrigerant cooler, carbon dioxide of 6 MPa is shown. It can be seen that the value of the heat transfer coefficient is lower than the value of the heat transfer coefficient of carbon dioxide of 10 MPa.

For this reason, in the heat source unit 1a of the air conditioner 1 of the present embodiment (that is, a heat source unit configured to suck air from the side and blow the air upward), the intermediate heat exchanger 7 is temporarily When integrated with the heat source side heat exchanger 4 in a state of being arranged below the heat source side heat exchanger 4, it is integrated with the heat source side heat exchanger 4 at the lower part of the heat source unit 1a where the flow velocity of air serving as the heat source is small. The intermediate heat exchanger 7 will be arranged, the influence of the reduction in the heat transfer coefficient on the air side of the intermediate heat exchanger 7 due to the arrangement of the intermediate heat exchanger 7 below the heat source unit 1a, and the intermediate heat exchange The effect that the heat transfer coefficient on the refrigerant side of the heat exchanger 7 becomes lower than the heat transfer coefficient on the refrigerant side of the heat source side heat exchanger 4 overlaps, and the overall heat transfer coefficient of the intermediate heat exchanger 7 becomes low, Integrate with heat source side heat exchanger 4 In view of this, there is a limit to the extent to which the heat transfer area of the intermediate heat exchanger 7 is increased, so that the heat transfer performance of the intermediate heat exchanger 7 is degraded. Since the exchanger 7 is integrated with the heat source side heat exchanger 4 in a state of being disposed above the heat source side heat exchanger 4, an intermediate heat is formed above the heat source unit 1a where the flow rate of air as a heat source is large. As a result, the heat transfer coefficient on the air side of the intermediate heat exchanger 7 is increased, and as a result, a decrease in the overall heat transfer coefficient of the intermediate heat exchanger 7 is suppressed, which is relatively large. It is possible to suppress a decrease in heat transfer performance of the intermediate heat exchanger 7 that requires an exchange heat amount. Moreover, the drain heater 97 is disposed below the heat source unit 1a where the flow rate of air serving as a heat source is small, and below the heat source side heat exchanger 4 as an evaporator for the purpose of heating the drain water. Both the point that needs to be provided and the point that the amount of exchange heat can be smaller than that of the intermediate heat exchanger 7 can be satisfied.

(3) Modification 1
In the second embodiment described above, the drain heater 97 is disposed in the lower part of the heat source side heat exchanger 4 (more specifically, the drain heater 97 is disposed in the lower part, and the heat source is formed on the bottom plate 77. However, the drain heater 97 may be disposed on the bottom plate 77 that functions as a drain pan.
For example, as shown in FIGS. 24 and 25, the drain heater 97 has a structure composed of a heat transfer tube that does not share heat transfer fins with the heat source side heat exchanger 4, and is arranged so as to contact a bottom plate 77 that functions as a drain pan. can do.
And also in the air conditioning apparatus 1 (refrigeration apparatus) of the present modification, the compression mechanism 2 of the two-stage compression type is adopted, and the rear side compression of the compression mechanism 2 is performed during the cooling operation in which the switching mechanism 3 is in the cooling operation state. During the heating operation in which the intermediate heat exchanger 7 functioning as a cooler for the refrigerant sucked into the element 2d (that is, the intermediate-pressure refrigerant in the refrigeration cycle) is used and the switching mechanism 3 is in the heating operation state, the refrigerant evaporator The point that the drain heater 97 that heats the drain water generated in the heat source side heat exchanger 4 that functions as is the same as in the second embodiment described above, and therefore, as a refrigerant radiator during cooling operation. The heat dissipation loss in the functioning heat source side heat exchanger 4 can be reduced. During heating operation, the drain heater 97 is used not only to suppress the freezing and growth of drain water, but also the high pressure in the refrigeration cycle. Compared to using drain heater for heating the drain water by the refrigerant, it is possible to suppress an increase in energy loss at the time of heating operation.

In addition, in the present modification, the drain heater 97 is disposed on the bottom plate 77 that functions as a drain pan, so that the drain water that flows down from the heat source side heat exchanger 4 and accumulates on the bottom plate 77 that functions as a drain pan is difficult to freeze. Thus, freezing and growth of drain water in the bottom plate 77 functioning as a drain pan can be effectively suppressed.
(4) Modification 2
In the above-described second embodiment and its modification, the drain heater 97 is either disposed at the lower part of the heat source side heat exchanger 4 or is disposed on the bottom plate 77 functioning as a drain pan. However, you may arrange | position at both the lower part of the heat source side heat exchanger 4, and the baseplate 77 which functions as a drain pan.
For example, as shown in FIGS. 26 to 28, the drain heater 97 includes a first drain heater 97a disposed at the lower portion of the heat source side heat exchanger 4 and a second plate 77 disposed as a drain pan. The first drain heater 97a and the second drain heater 97b are connected in parallel (see FIG. 26), or the first drain heater 97a and the second drain heater 97b. Can be connected in series (see FIG. 27). In FIG. 27, the second drain heater 97b is connected downstream of the first drain heater 97a, but the first drain heater 97a is connected downstream of the second drain heater 97b. Also good.

Also in the air conditioner 1 (refrigeration apparatus) of the present modification, the compression mechanism 2 of the two-stage compression type is adopted, and the rear side compression of the compression mechanism 2 is performed during the cooling operation in which the switching mechanism 3 is in the cooling operation state. The refrigerant evaporator is used during the heating operation in which the intermediate heat exchanger 7 functioning as a cooler for the refrigerant sucked into the element 2d (that is, the intermediate-pressure refrigerant in the refrigeration cycle) is used to bring the switching mechanism 3 into the heating operation state. The point that the drain heater 97 (here, the first drain heater 97a and the second drain heater 97b) that heats the drain water generated in the heat source side heat exchanger 4 functioning as Since it is the same as 2 embodiment and its modification, the heat dissipation loss in the heat source side heat exchanger 4 which functions as a radiator of the refrigerant can be reduced during the cooling operation, and the drain heating is performed during the heating operation. 97 not only suppresses freezing and growth of drain water, but also suppresses an increase in energy loss during heating operation compared to using a drain heater that heats drain water with a high-pressure refrigerant in the refrigeration cycle. be able to.

In addition, in the present modification, the drain heater 97 includes a first drain heater 97a disposed at the lower portion of the heat source side heat exchanger 4 and a second drain heater 97b disposed on the bottom plate 77 functioning as a drain pan. Therefore, the drain water is less likely to freeze in the lower part of the heat source side heat exchanger 4 where the amount of attached drain water is the largest due to the flow of drain water, and functions as a drain pan by flowing down from the heat source side heat exchanger 4 The drain water collected on the bottom plate 77 is less likely to freeze, and thereby, both the freezing and growth of drain water in the heat source side heat exchanger 4 and the freezing and growth of drain water on the bottom plate 77 functioning as a drain pan are effective. Can be suppressed.
(5) Modification 3
In the second modification of the second embodiment described above, the drain heater 97 (more specifically, the first drain heater 97a and the second drain heater 97b) is provided below the heat source side heat exchanger 4, and The refrigerant is disposed on both of the bottom plates 77 functioning as drain pans, and is configured to flow the refrigerant discharged from the front-stage compression element 2c and sucked into the rear-stage compression element 2d to both the drain heaters 97a and 97b. However, you may be comprised so that it can be sent only to either one of the 1st drain heater 97a and the 2nd drain heater 97b.

For example, as shown in FIG. 29, in the configuration in which the first drain heater 97a and the second drain heater 97b are connected in parallel, the first drain that restricts the flow of the refrigerant to the first drain heater 97a. A drain heater switching mechanism 98 including a heater opening / closing valve 98a and a second drain heater opening / closing valve 98b that restricts the flow of refrigerant to the second drain heater 97b can be provided. Further, as shown in FIG. 30, in the configuration in which the first drain heater 97a and the second drain heater 97b are connected in series, the first drain heater bypass for bypassing the first drain heater 97a. A pipe 99a, a first drain heater on / off valve 98a for restricting the flow of refrigerant to the first drain heater 97a, a second drain heater bypass pipe 99b for bypassing the second drain heater 97b, A drain heater switching mechanism 98 including a second drain heater opening / closing valve 98b that restricts the flow of the refrigerant to the two-drain heater 97b can be provided. Here, a first drain heater bypass opening / closing valve 99c and a second drain heater bypass opening / closing valve 99d are provided in the first drain heater bypass pipe 99a and the second drain heater bypass pipe 99b, respectively. In this modification, the on-off valves 98a, 98b, 99c, and 99d are electromagnetic valves. Moreover, you may comprise the structure shown by FIG.29 and FIG.30 using a three-way valve etc. instead of a solenoid valve.

And also in the air conditioning apparatus 1 (refrigeration apparatus) of this modification, while being able to acquire the effect similar to the modification 2 of the above-mentioned 2nd Embodiment, the 1st drain heater 97a and the 2nd drain heating Since a drain heater switching mechanism 98 that enables switching to the vessel 97b is further provided, only one of the first drain heater 97a and the second drain heater 97b can be used as necessary. it can.
(6) Modification 4
In the above-described second embodiment and its modification, the intermediate heat exchanger 7 is a device that is used only during the cooling operation in which the switching mechanism 3 is in the cooling operation state, and the switching mechanism 3 is in the heating operation state. It is a device that is not used during heating operation.
Therefore, in the present modification, as shown in FIG. 31, in the refrigerant circuit 10 (see FIG. 14) of the above-described second embodiment, the intermediate heat exchanger 7 is in the cooling operation when the switching mechanism 3 is in the cooling operation state. Is used as a refrigerant cooler of intermediate pressure in the refrigeration cycle, and during the heating operation in which the switching mechanism 3 is in the heating operation state, the utilization side heat exchanger 6 functions as a refrigerant evaporator that has dissipated heat. A second suction return pipe 92 for connecting one end of the intermediate heat exchanger 7 and the suction side of the compression mechanism 2, between the use side heat exchanger 6 and the heat source side heat exchanger 4, and the intermediate heat exchanger 7 The refrigerant circuit 110 is provided with an intermediate heat exchanger return pipe 94 for connecting the other end of the refrigerant.

Here, the second suction return pipe 92 is connected to one end of the intermediate heat exchanger 7 (here, the end on the upstream side of the compression element 2c), and passes through the intermediate heat exchanger bypass pipe 9 to compress the upstream side of the compression element. In order to connect one end of the intermediate heat exchanger 7 and the suction side (here, the suction pipe 2a) of the compression mechanism 2 when the refrigerant discharged from 2c is sucked into the compression element 2d on the rear stage side. This is a refrigerant pipe. The intermediate heat exchanger return pipe 94 is connected to the other end of the intermediate heat exchanger 7 (here, the end on the side of the compression element 2d on the rear stage side) and is compressed on the front stage side through the intermediate heat exchanger bypass pipe 9. During the heating operation in which the refrigerant discharged from the element 2c is sucked into the compression element 2d on the rear stage side and the switching mechanism 3 is in the heating operation state, the use side heat exchanger 6 and the heat source side heat exchanger 4 In order to connect the intermediate heat exchanger 7 (here, between the second expansion mechanism 5b that decompresses the refrigerant until the low pressure in the refrigeration cycle and the heat source side heat exchanger 4 as an evaporator) and the other end of the intermediate heat exchanger 7 This is a refrigerant pipe. In the present modification, the second suction return pipe 92 has one end thereof connected to the front end of the intermediate heat exchanger bypass pipe 9 of the intermediate refrigerant pipe 8 from the end on the compression element 2c side, and is connected to the front stage of the intermediate heat exchanger 7. The other end of the compression element 2c is connected to the suction side (here, the suction pipe 2a). The intermediate heat exchanger return pipe 94 has one end connected to a portion from the second expansion mechanism 5 b to the heat source side heat exchanger 4, and the other end connected to the intermediate heat exchanger 7 of the intermediate refrigerant pipe 8. Is connected to the portion from the compression element 2c side end of the previous stage side to the check mechanism 15. The second suction return pipe 92 is provided with a second suction return on / off valve 92a, and the intermediate heat exchanger return pipe 94 is provided with an intermediate heat exchanger return on / off valve 94a. The second suction return on / off valve 92a and the intermediate heat exchanger return on / off valve 94a are electromagnetic valves in this modification. In the present modification, the second suction return on-off valve 92a is basically closed during the cooling operation in which the switching mechanism 3 is in the cooling operation state and controlled to be opened in the heating operation in which the switching mechanism 3 is in the heating operation state. The The intermediate heat exchanger return on / off valve 94a is controlled to be closed during the cooling operation in which the switching mechanism 3 is in the cooling operation state, and is opened during the heating operation in which the switching mechanism 3 is in the heating operation state.

As described above, in this modification, the intermediate pressure in the refrigeration cycle that flows through the intermediate refrigerant pipe 8 mainly during the cooling operation by the intermediate heat exchanger bypass pipe 9, the second suction return pipe 92, and the intermediate heat exchanger return pipe 94 is provided. The intermediate heat exchanger 7 can cool the refrigerant, and during the heating operation, the intermediate heat exchanger 7 is bypassed by the intermediate heat exchanger bypass pipe 9 for the intermediate pressure refrigerant in the refrigeration cycle flowing through the intermediate refrigerant pipe 8. At the same time, the drain water generated in the heat source side heat exchanger 4 is heated in the drain heater 97 and further cooled in the use side heat exchanger 6 by the second suction return pipe 92 and the intermediate heat exchanger return pipe 94. A part of the refrigerant is led to the intermediate heat exchanger 7 to be evaporated and returned to the suction side of the compression mechanism 2.
Next, the operation of the air conditioner 1 according to this modification will be described with reference to FIGS.
Here, FIG. 32 is a diagram showing the flow of the refrigerant in the air conditioner 1 during the cooling operation, and FIG. 33 is a pressure-enthalpy diagram illustrating the refrigeration cycle during the cooling operation. FIG. 35 is a temperature-entropy diagram illustrating a refrigeration cycle during cooling operation, FIG. 35 is a diagram illustrating the flow of refrigerant in the air conditioner 1 during heating operation, and FIG. 36 is during heating operation. FIG. 37 is a pressure-enthalpy diagram illustrating the refrigeration cycle, and FIG. 37 is a temperature-entropy diagram illustrating the refrigeration cycle during the heating operation. Note that operation control in the following cooling operation and heating operation is performed by the above-described control unit (not shown). In the following description, “high pressure” means high pressure in the refrigeration cycle (that is, pressure at points D, D ′, and E in FIGS. 33 and 34 and pressure at points D, D ′, and F in FIGS. 36 and 37). “Low pressure” means low pressure in the refrigeration cycle (that is, pressure at points A and F in FIGS. 33 and 34 and pressure at points A, E and V in FIGS. 36 and 37), and “intermediate pressure”. "Means the intermediate pressure in the refrigeration cycle (that is, the pressure at points B and C1 in FIGS. 33 and 34 and the pressure at points B and C2 in FIGS. 36 and 37).

<Cooling operation>
During the cooling operation, the switching mechanism 3 is in the cooling operation state indicated by the solid lines in FIGS. 31 and 32. The opening degree of the first expansion mechanism 5a and the second expansion mechanism 5b is adjusted. Since the switching mechanism 3 is in the cooling operation state, the intermediate heat exchanger on / off valve 12 of the intermediate refrigerant pipe 8 is opened, and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is closed. As a result, the intermediate heat exchanger 7 is put into a state of functioning as a cooler, the refrigerant does not flow into the drain heater 97, and the second suction return on / off valve 92a of the second suction return pipe 92 is By being closed, the intermediate heat exchanger 7 is not connected to the suction side of the compression mechanism 2, and the intermediate heat exchanger return on / off valve 94a of the intermediate heat exchanger return pipe 94 is closed. The intermediate side heat exchanger 7 is not connected between the use side heat exchanger 6 and the heat source side heat exchanger 4.

In the state of the refrigerant circuit 110, a low-pressure refrigerant (see point A in FIGS. 31 to 34) is sucked into the compression mechanism 2 from the suction pipe 2a, and is first compressed to an intermediate pressure by the compression element 2c. The refrigerant is discharged into the refrigerant pipe 8 (see point B in FIGS. 31 to 34). The intermediate pressure refrigerant discharged from the preceding compression element 2c is cooled by exchanging heat with air as a cooling source supplied by the heat source side fan 40 in the intermediate heat exchanger 7 (FIG. 31). (See point C1 in FIG. 34). The refrigerant cooled in the intermediate heat exchanger 7 is then sucked into the compression element 2d connected to the rear stage side of the compression element 2c, further compressed, and discharged from the compression mechanism 2 to the discharge pipe 2b ( (See point D in FIGS. 31 to 34). Here, the high-pressure refrigerant discharged from the compression mechanism 2 is compressed to a pressure exceeding the critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIG. 33) by the two-stage compression operation by the compression elements 2c and 2d. Has been. The high-pressure refrigerant discharged from the compression mechanism 2 flows into the oil separator 41a constituting the oil separation mechanism 41, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the oil separator 41a flows into the oil return pipe 41b constituting the oil separation mechanism 41, and is compressed after being reduced in pressure by the pressure reduction mechanism 41c provided in the oil return pipe 41b. It is returned to the suction pipe 2a of the mechanism 2 and again sucked into the compression mechanism 2. Next, the high-pressure refrigerant after the refrigerating machine oil is separated in the oil separation mechanism 41 is sent to the heat source side heat exchanger 4 functioning as a refrigerant radiator through the check mechanism 42 and the switching mechanism 3. The high-pressure refrigerant sent to the heat source side heat exchanger 4 is cooled in the heat source side heat exchanger 4 by exchanging heat with air as a cooling source supplied by the heat source side fan 40 (FIG. 31). (See point E in FIG. 34). Then, the high-pressure refrigerant cooled in the heat source side heat exchanger 4 flows into the receiver inlet pipe 18a through the inlet check valve 17a of the bridge circuit 17, and is reduced to near the saturation pressure by the first expansion mechanism 5a. (See point I in FIGS. 31 and 32). Then, the refrigerant stored in the receiver 18 is sent to the receiver outlet pipe 18b and is decompressed by the second expansion mechanism 5b to become a low-pressure gas-liquid two-phase refrigerant, and the outlet check valve 17c of the bridge circuit 17 is used. And is sent to the use side heat exchanger 6 functioning as a refrigerant evaporator (see FIG. 31 to FIG. 34, point F). Then, the low-pressure gas-liquid two-phase refrigerant sent to the use-side heat exchanger 6 is heated by exchanging heat with water or air as a heating source to evaporate (FIG. 31 to FIG. 31). 34, point A). Then, the low-pressure refrigerant heated in the use side heat exchanger 6 is again sucked into the compression mechanism 2 via the switching mechanism 3. In this way, the cooling operation is performed.

And also in the air conditioning apparatus 1 (refrigeration apparatus) of this modification, the same effect as the time of the air_conditionaing | cooling operation in the above-mentioned 2nd Embodiment can be obtained.
<Heating operation>
During the heating operation, the switching mechanism 3 is in the heating operation state indicated by the broken lines in FIG. 31 and FIG. The opening degree of the first expansion mechanism 5a and the second expansion mechanism 5b is adjusted. Since the switching mechanism 3 is in a heating operation state, the intermediate heat exchanger on / off valve 12 of the intermediate refrigerant pipe 8 is closed, and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is opened. As a result, the intermediate heat exchanger 7 is brought into a state in which it does not function as a cooler, the refrigerant flows into the drain heater 97, and the second suction return on / off valve 92a of the second suction return pipe 92 is opened. As a result, the intermediate heat exchanger 7 and the suction side of the compression mechanism 2 are connected, and the intermediate heat exchanger return on / off valve 94a of the intermediate heat exchanger return pipe 94 is opened. Between the use side heat exchanger 6 and the heat source side heat exchanger 4, the intermediate heat exchanger 7 is connected.

In the state of the refrigerant circuit 110, the low-pressure refrigerant (see point A in FIGS. 31 and 35 to 37) is sucked into the compression mechanism 2 from the suction pipe 2a and first compressed to an intermediate pressure by the compression element 2c. Thereafter, the refrigerant is discharged into the intermediate refrigerant pipe 8 (see point B in FIGS. 31 and 35 to 37). Unlike the cooling operation, the intermediate-pressure refrigerant discharged from the upstream-side compression element 2c does not pass through the intermediate heat exchanger 7 and is supplied to the drain heater 97 provided in the intermediate heat exchanger bypass pipe 9. In the drain heater 97, cooling is performed by exchanging heat with the drain water generated in the heat source side heat exchanger 4 functioning as a refrigerant evaporator and flowing down the heat source side heat exchanger 4 (FIG. 31, see point C2 in FIGS. The refrigerant cooled in the drain heater 97 is sucked into the compression element 2d connected to the rear stage side of the compression element 2c, further compressed, and discharged from the compression mechanism 2 to the discharge pipe 2b (FIG. 31, FIG. 35 to point 37 in FIG. 37). Here, the high-pressure refrigerant discharged from the compression mechanism 2 is subjected to the critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIG. 36) by the two-stage compression operation by the compression elements 2c and 2d as in the cooling operation. ) Compressed to a pressure exceeding The high-pressure refrigerant discharged from the compression mechanism 2 flows into the oil separator 41a constituting the oil separation mechanism 41, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the oil separator 41a flows into the oil return pipe 41b constituting the oil separation mechanism 41, and is compressed after being reduced in pressure by the pressure reduction mechanism 41c provided in the oil return pipe 41b. It is returned to the suction pipe 2a of the mechanism 2 and again sucked into the compression mechanism 2. Next, the high-pressure refrigerant after the refrigerating machine oil is separated in the oil separation mechanism 41 is sent to the use side heat exchanger 6 functioning as a refrigerant radiator through the check mechanism 42 and the switching mechanism 3 to be cooled. It is cooled by exchanging heat with water or air as a source (see point F in FIGS. 31 and 35 to 37). The high-pressure refrigerant cooled in the use-side heat exchanger 6 flows into the receiver inlet pipe 18a through the inlet check valve 17b of the bridge circuit 17, and is reduced to near the saturation pressure by the first expansion mechanism 5a. (See point I in FIGS. 31 and 35). Then, the refrigerant stored in the receiver 18 is sent to the receiver outlet pipe 18b and is reduced in pressure by the second expansion mechanism 5b to become a low-pressure gas-liquid two-phase refrigerant, and the outlet check valve 17d of the bridge circuit 17 is supplied. Through the intermediate heat exchanger return pipe 94 and also to the intermediate heat exchanger 7 functioning as the refrigerant evaporator (FIGS. 31 and 31). 35 to point 37 in FIG. 37). Then, the low-pressure gas-liquid two-phase refrigerant sent to the heat source side heat exchanger 4 is heated and evaporated by exchanging heat with air as a heating source supplied by the heat source side fan 40. (Refer to point A in FIGS. 31 and 35 to 37). Further, the low-pressure gas-liquid two-phase refrigerant sent to the intermediate heat exchanger 7 is also heated and evaporated by exchanging heat with air as a heating source supplied by the heat source side fan 40. (Refer to point V in FIGS. 31 and 35 to 37). The low-pressure refrigerant heated and evaporated in the heat source side heat exchanger 4 is again sucked into the compression mechanism 2 via the switching mechanism 3. The low-pressure refrigerant heated and evaporated in the intermediate heat exchanger 7 is again sucked into the compression mechanism 2 through the second suction return pipe 92. In this way, the heating operation is performed.

Thus, also in the air conditioning apparatus 1 (refrigeration apparatus) according to the present modification, it is possible to obtain the same functions and effects as those during the heating operation in the second embodiment described above. Moreover, in the present modification, during the heating operation, the intermediate heat exchanger 7 is not simply put into a state of not functioning as a cooler by not using the intermediate heat exchanger 7. It is made to function as an evaporator of the refrigerant that has dissipated heat in the use side heat exchanger 7, and is also used during heating operation, while suppressing heat radiation from the intermediate heat exchanger 7 to the outside, While increasing the evaporation capacity, the intermediate heat exchanger 7 can be used effectively during heating operation.
In this modification, drain water is also generated from the intermediate heat exchanger 7 during the heating operation. However, since the intermediate heat exchanger 7 is disposed above the heat source side heat exchanger 4, the intermediate heat exchanger 7 generates intermediate water. The drain water generated in the exchanger 7 flows down through the heat source side heat exchanger 4 and includes not only the drain water generated in the heat source side heat exchanger 4 but also the drain water generated in the intermediate heat exchanger 7. 97 can be heated.

In this modification, the second suction return pipe 92 and the intermediate heat exchanger return pipe 94 are provided in the configuration in which the drain heater 97 is provided below the heat source side heat exchanger 4 in the second embodiment. However, the drain heater 97 as in the first to third modifications of the second embodiment described above is provided in the bottom plate 77 that functions as a drain pan, the bottom of the heat source side heat exchanger 4, and the bottom plate that functions as a drain pan. In the configuration provided in 77, a second suction return pipe 92 and an intermediate heat exchanger return pipe 94 may be provided.
(7) Modification 5
In the fourth modification of the second embodiment described above, the refrigerant discharged from the compression element 2c on the front stage side through the intermediate heat exchanger 7 is sucked into the compression element 2d on the rear stage side, and is intermediated through the second suction return pipe 92. A state in which the heat exchanger 7 is not connected to the suction side of the compression mechanism 2 (hereinafter, this state is referred to as “refrigerant non-return state”), and the intermediate heat exchanger bypass pipe 9 is discharged from the compression element 2c on the front stage side. The refrigerant is sucked into the second compression element 2d and the intermediate heat exchanger 7 and the suction side of the compression mechanism 2 are connected through the second suction return pipe 92 (hereinafter, this state is referred to as “refrigerant return state”). Is switched according to the open / close state of the on-off valves 11, 12, 92a. However, as shown in FIG. 38, instead of the on-off valves 11, 12, 92a, the refrigerant unreturned state and the refrigerant Return State and may be a refrigerant circuit 110 provided with the intermediate heat exchanger switching valve 93 capable of switching.

Here, the intermediate heat exchanger switching valve 93 is a valve that can be switched between a refrigerant non-return state and a refrigerant return state. In this modification, the intermediate heat exchanger switching valve 93 is connected to the discharge side of the compression element 2c on the upstream side of the intermediate refrigerant pipe 8. The intermediate refrigerant pipe 8 is connected to the inlet side of the intermediate heat exchanger 7, the intermediate heat exchanger bypass pipe 9 is connected to the front end side of the compression element 2 c, and the second suction return pipe 92 is connected to the intermediate heat exchanger 7 side end. This is a four-way switching valve. The intermediate heat exchanger bypass pipe 9 allows the refrigerant to flow from the discharge side of the front-stage compression element 2c to the suction side of the rear-stage compression element 2d, and sucks the rear-stage compression element 2d. There is further provided a check mechanism 9a for blocking the flow of the refrigerant from the side to the discharge side of the compression element 2c on the upstream side and the suction side of the compression mechanism 2. The check mechanism 9a is a check valve in this modification.
In the present modification, detailed description is omitted, but the intermediate heat exchanger switching valve 93 is switched to the refrigerant non-return state (see the solid line of the intermediate heat exchanger switching valve 93 in FIG. 38). The cooling operation similar to the fourth modification of the second embodiment is performed, and the refrigerant discharged from the compression element 2c on the front stage through the intermediate heat exchanger bypass pipe 9 is sucked into the compression element 2d on the rear stage, and the second By switching to the refrigerant return state in which the intermediate heat exchanger 7 and the suction side of the compression mechanism 2 are connected through the suction return pipe 92 (see the broken line of the intermediate heat exchanger switching valve 93 in FIG. 38), the second implementation described above. A heating operation similar to that of the fourth modification of the embodiment can be performed.

And also in the structure of this modification, the effect similar to the modification 4 of the above-mentioned 2nd Embodiment can be acquired. In addition, in the present modification, the intermediate heat exchanger switching valve 93 can be switched between the refrigerant non-return state and the refrigerant return state, so that the plurality of valves 11 as in the fourth modification of the second embodiment described above, 12 and 92a, the number of valves can be reduced as compared with the case of adopting a configuration in which the refrigerant non-return state and the refrigerant return state are switched. Further, since the pressure loss is reduced as compared with the case where a solenoid valve is used, it is possible to suppress a decrease in the intermediate pressure in the refrigeration cycle and to suppress a decrease in operating efficiency.
In this modification, the intermediate heat exchanger switching valve 93 and the like are provided in the configuration in which the drain heater 97 is provided below the heat source side heat exchanger 4 in the second embodiment. A configuration in which the drain heater 97 as in Modifications 1 to 3 of the second embodiment is provided in the bottom plate 77 that functions as a drain pan, or a configuration in which the lower portion of the heat source side heat exchanger 4 and the bottom plate 77 that functions as a drain pan are provided. In this case, an intermediate heat exchanger switching valve 93 or the like may be provided.

(8) Modification 6
In the above-described embodiment and its modification, in the air conditioner 1 that performs the two-stage compression refrigeration cycle configured to be able to switch between the cooling operation and the heating operation by the switching mechanism 3, the discharge is performed from the compression element 2c on the front stage side Intermediate heat exchanger 7 that functions as a cooler for the refrigerant that is sucked into the downstream compression element 2d, and an intermediate heat exchanger bypass pipe that is connected to the intermediate refrigerant pipe 8 so as to bypass the intermediate heat exchanger 7 9. A drain heater 97 for heating the drain water generated in the heat source side heat exchanger 4 by the intermediate-pressure refrigerant in the refrigeration cycle is provided. In addition to this configuration, the first second-stage injection pipe 19 and Intermediate pressure injection by the economizer heat exchanger 20 may be performed.
For example, as shown in FIG. 39, in the refrigerant circuit 110 (see FIG. 31) of Modification 4 of the second embodiment described above, the refrigerant further provided with the first second-stage injection pipe 19 and the economizer heat exchanger 20. Circuit 210 can be used.

The first second-stage injection pipe 19 has a function of branching the refrigerant flowing between the heat source-side heat exchanger 4 and the use-side heat exchanger 6 and returning it to the compression element 2d on the rear stage side of the compression mechanism 2. . In this modification, the first second-stage injection pipe 19 is provided to branch the refrigerant flowing through the receiver inlet pipe 18a and return it to the suction side of the second-stage compression element 2d. More specifically, the first second-stage injection pipe 19 is positioned on the upstream side of the first expansion mechanism 5a of the receiver inlet pipe 18a (that is, when the switching mechanism 3 is in the cooling operation state, the heat source side heat The refrigerant is branched from the exchanger 4 and the first expansion mechanism 5a) and returned to the downstream position of the intermediate heat exchanger 7 in the intermediate refrigerant pipe 8. In addition, the first second-stage injection pipe 19 is provided with a first second-stage injection valve 19a capable of opening degree control. And the 1st latter stage side injection valve 19a is an electric expansion valve in this modification.

The economizer heat exchanger 20 includes a refrigerant flowing between the heat source side heat exchanger 4 and the use side heat exchanger 6 and a refrigerant flowing through the first second-stage injection pipe 19 (more specifically, a first second-stage injection valve). 19a is a heat exchanger that performs heat exchange with the refrigerant after being reduced in pressure to near the intermediate pressure. In the present modification, the economizer heat exchanger 20 is positioned on the upstream side of the first expansion mechanism 5a of the receiver inlet pipe 18a (that is, when the switching mechanism 3 is in the cooling operation state, the heat source side heat exchanger 4 Between the refrigerant flowing between the refrigerant and the first expansion mechanism 5a) and the refrigerant flowing through the first second-stage injection pipe 19, and a flow path through which the two refrigerants face each other. Have. In this modification, the economizer heat exchanger 20 is provided on the downstream side of the position where the first second-stage injection pipe 19 is branched from the receiver inlet pipe 18a. For this reason, the refrigerant flowing between the heat source side heat exchanger 4 and the use side heat exchanger 6 is transferred to the first second-stage injection pipe 19 before heat exchange is performed in the economizer heat exchanger 20 in the receiver inlet pipe 18a. After branching, the economizer heat exchanger 20 exchanges heat with the refrigerant flowing through the first second-stage injection pipe 19.

As described above, in this modification, during the cooling operation in which the switching mechanism 3 is in the cooling operation state, the high-pressure refrigerant cooled in the heat source side heat exchanger 4 is exchanged with the inlet check valve 17a of the bridge circuit 17 and the economizer heat exchange. Can be sent to the use side heat exchanger 6 through the first expansion mechanism 5a of the receiver 20, the receiver inlet pipe 18a, the receiver 18, the second expansion mechanism 5b of the receiver outlet pipe 18b, and the outlet check valve 17c of the bridge circuit 17. It is like that. Further, during the heating operation in which the switching mechanism 3 is in the heating operation state, the high-pressure refrigerant cooled in the use side heat exchanger 6 is supplied to the inlet check valve 17b of the bridge circuit 17, the economizer heat exchanger 20, and the receiver inlet pipe 18a. The first expansion mechanism 5a, the receiver 18, the second expansion mechanism 5b of the receiver outlet pipe 18b, and the outlet check valve 17d of the bridge circuit 17 can be sent to the heat source side heat exchanger 4.

Further, in this modification, the intermediate refrigerant pipe 8 or the compression mechanism 2 is provided with an intermediate pressure sensor 54 that detects the pressure of the refrigerant flowing through the intermediate refrigerant pipe 8. An economizer outlet temperature sensor 55 that detects the temperature of the refrigerant at the outlet of the economizer heat exchanger 20 on the first rear-stage injection pipe 19 side is provided at the outlet of the economizer heat exchanger 20 on the first rear-stage injection pipe 19 side. ing.
Next, the operation of the air conditioner 1 of this modification will be described with reference to FIGS. 39 to 45. Here, FIG. 40 is a diagram showing the flow of the refrigerant in the air conditioning apparatus 1 during the cooling operation, and FIG. 41 is a pressure-enthalpy diagram illustrating the refrigeration cycle during the cooling operation. FIG. 43 is a temperature-entropy diagram illustrating the refrigeration cycle during cooling operation, FIG. 43 is a diagram illustrating the flow of refrigerant in the air conditioner 1 during heating operation, and FIG. 44 is during heating operation. FIG. 45 is a pressure-enthalpy diagram illustrating the refrigeration cycle, and FIG. 45 is a temperature-entropy diagram illustrating the refrigeration cycle during the heating operation. Note that operation control in the following cooling operation and heating operation is performed by the above-described control unit (not shown). In the following description, “high pressure” means high pressure in the refrigeration cycle (that is, pressure at points D, D ′, E, and H in FIGS. 41 and 42, and points D, D ′, and FIGS. 44 and 45). "Low pressure" means low pressure in the refrigeration cycle (that is, pressure at points A and F in FIGS. 41 and 42 and pressure at points A, E and V in FIGS. 44 and 45). The “intermediate pressure” means an intermediate pressure in the refrigeration cycle (that is, the pressure at points B, C1, G, J, and K in FIGS. 41 and 42, and points B, C2, G, and J in FIGS. , Pressure at K).

<Cooling operation>
During the cooling operation, the switching mechanism 3 is in the cooling operation state indicated by the solid lines in FIGS. The opening degree of the first expansion mechanism 5a and the second expansion mechanism 5b is adjusted. The opening degree of the first second-stage injection valve 19a is also adjusted. More specifically, in this modification, the first second-stage injection valve 19a has an opening degree so that the degree of superheat of the refrigerant at the outlet of the economizer heat exchanger 20 on the first second-stage injection pipe 19 side becomes a target value. So-called superheat control is performed. In this modification, the superheat degree of the refrigerant at the outlet of the economizer heat exchanger 20 on the first second-stage injection pipe 19 side is obtained by converting the intermediate pressure detected by the intermediate pressure sensor 54 into the saturation temperature, and the economizer outlet temperature sensor 55. This is obtained by subtracting the saturation temperature value of the refrigerant from the refrigerant temperature detected by the above. Although not adopted in this modification, a temperature sensor is provided at the inlet of the economizer heat exchanger 20 on the first second-stage injection pipe 19 side, and the refrigerant temperature detected by this temperature sensor is used as the economizer outlet temperature sensor 55. The degree of superheat of the refrigerant at the outlet of the economizer heat exchanger 20 on the first second-stage injection pipe 19 side may be obtained by subtracting from the refrigerant temperature detected by the above. Further, the adjustment of the opening degree of the first second-stage injection valve 19a is not limited to the superheat degree control, and, for example, is to open a predetermined opening degree according to the refrigerant circulation amount in the refrigerant circuit 10 or the like. Also good. Since the switching mechanism 3 is in the cooling operation state, the intermediate heat exchanger on / off valve 12 of the intermediate refrigerant pipe 8 is opened, and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is closed. As a result, the intermediate heat exchanger 7 is put into a state of functioning as a cooler, the refrigerant does not flow into the drain heater 97, and the second suction return on / off valve 92a of the second suction return pipe 92 is By being closed, the intermediate heat exchanger 7 is not connected to the suction side of the compression mechanism 2, and the intermediate heat exchanger return on / off valve 94a of the intermediate heat exchanger return pipe 94 is closed. The intermediate side heat exchanger 7 is not connected between the use side heat exchanger 6 and the heat source side heat exchanger 4.

In the state of the refrigerant circuit 210, low-pressure refrigerant (see point A in FIGS. 39 to 42) is sucked into the compression mechanism 2 from the suction pipe 2a, and is first compressed to an intermediate pressure by the compression element 2c. The refrigerant is discharged into the refrigerant pipe 8 (see point B1 in FIGS. 39 to 42). The intermediate pressure refrigerant discharged from the preceding compression element 2c is cooled by exchanging heat with air as a cooling source supplied by the heat source side fan 40 in the intermediate heat exchanger 7 (FIG. 39). (See point C1 in FIG. 42). The refrigerant cooled in the intermediate heat exchanger 7 is further cooled by joining with the refrigerant (see point K in FIGS. 39 to 42) returned from the first second-stage injection pipe 19 to the second-stage compression mechanism 2d. (See point G in FIGS. 39 to 42). Next, the intermediate-pressure refrigerant joined with the refrigerant returning from the first second-stage injection pipe 19 (that is, subjected to intermediate-pressure injection by the economizer heat exchanger 20) is compressed by being connected to the second-stage side of the compression element 2c. It is sucked into the element 2d, further compressed, and discharged from the compression mechanism 2 to the discharge pipe 2b (see point D in FIGS. 39 to 42). Here, the high-pressure refrigerant discharged from the compression mechanism 2 is compressed to a pressure exceeding the critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIG. 41) by the two-stage compression operation by the compression elements 2c and 2d. Has been. The high-pressure refrigerant discharged from the compression mechanism 2 flows into the oil separator 41a constituting the oil separation mechanism 41, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the oil separator 41a flows into the oil return pipe 41b constituting the oil separation mechanism 41, and is compressed after being reduced in pressure by the pressure reduction mechanism 41c provided in the oil return pipe 41b. It is returned to the suction pipe 2a of the mechanism 2 and again sucked into the compression mechanism 2. Next, the high-pressure refrigerant after the refrigerating machine oil is separated in the oil separation mechanism 41 is sent to the heat source side heat exchanger 4 functioning as a refrigerant radiator through the check mechanism 42 and the switching mechanism 3. Then, the high-pressure refrigerant sent to the heat source side heat exchanger 4 is cooled by exchanging heat with air as a cooling source supplied by the heat source side fan 40 in the heat source side heat exchanger 4 (FIG. 39). (See point E in FIG. 42). The high-pressure refrigerant cooled in the heat source side heat exchanger 4 flows into the receiver inlet pipe 18 a through the inlet check valve 17 a of the bridge circuit 17, and a part thereof is branched to the first second-stage injection pipe 19. . The refrigerant flowing through the first second-stage injection pipe 19 is sent to the economizer heat exchanger 20 after being reduced to near the intermediate pressure at the first second-stage injection valve 19a (see point J in FIGS. 39 to 42). . Further, the refrigerant branched into the first second-stage injection pipe 19 flows into the economizer heat exchanger 20, and is cooled by exchanging heat with the refrigerant flowing through the first second-stage injection pipe 19 (FIG. 39 to FIG. 39). (See point H in FIG. 42). On the other hand, the refrigerant flowing through the first rear-stage injection pipe 19 is heated by exchanging heat with the high-pressure refrigerant cooled in the heat source-side heat exchanger 4 as a radiator (see point K in FIGS. 39 to 42). ), As described above, the refrigerant is joined to the intermediate-pressure refrigerant discharged from the preceding compression element 2c. Then, the high-pressure refrigerant cooled in the economizer heat exchanger 20 is decompressed to near the saturation pressure by the first expansion mechanism 5a and temporarily stored in the receiver 18 (see point I in FIGS. 39 and 40). Then, the refrigerant stored in the receiver 18 is sent to the receiver outlet pipe 18b and is decompressed by the second expansion mechanism 5b to become a low-pressure gas-liquid two-phase refrigerant, and the outlet check valve 17c of the bridge circuit 17 is used. And is sent to the use side heat exchanger 6 functioning as a refrigerant evaporator (see point F in FIGS. 39 to 42). Then, the low-pressure gas-liquid two-phase refrigerant sent to the use side heat exchanger 6 is heated by exchanging heat with water or air as a heating source and evaporated (see FIGS. 39 to 39). 42, point A). Then, the low-pressure refrigerant heated in the use side heat exchanger 6 is again sucked into the compression mechanism 2 via the switching mechanism 3. In this way, the cooling operation is performed.

And also in the air conditioning apparatus 1 (refrigeration apparatus) of this modification, the same effect as the cooling operation in the modification 4 of the second embodiment described above can be obtained. Moreover, in the present modification, the first rear-stage injection pipe 19 and the economizer heat exchanger 20 are provided to branch the refrigerant sent from the heat source-side heat exchanger 4 to the expansion mechanisms 5a and 5b and to the rear-stage compression element 2d. Therefore, the temperature of the refrigerant sucked into the compression element 2d on the rear stage side can be further reduced without performing heat radiation to the outside like the intermediate heat exchanger 7 (point C1 in FIG. 42). , G). Thereby, the temperature of the refrigerant discharged from the compression mechanism 2 is further suppressed (see points D and D ′ in FIG. 42), and the point in FIG. 42 is compared with the case where the first second-stage injection pipe 19 is not provided. Since the heat dissipation loss corresponding to the area surrounded by connecting C1, D ′, D, and G can be further reduced, the operating efficiency can be further improved.

<Heating operation>
During the heating operation, the switching mechanism 3 is in the heating operation state indicated by the broken lines in FIGS. The opening degree of the first expansion mechanism 5a and the second expansion mechanism 5b is adjusted. Further, the opening degree of the first second-stage injection valve 19a is adjusted in the same manner as in the above-described cooling operation. Since the switching mechanism 3 is in a heating operation state, the intermediate heat exchanger on / off valve 12 of the intermediate refrigerant pipe 8 is closed, and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is opened. As a result, the intermediate heat exchanger 7 is brought into a state in which it does not function as a cooler, the refrigerant flows into the drain heater 97, and the second suction return on / off valve 92a of the second suction return pipe 92 is opened. As a result, the intermediate heat exchanger 7 and the suction side of the compression mechanism 2 are connected, and the intermediate heat exchanger return on / off valve 94a of the intermediate heat exchanger return pipe 94 is opened. Between the use side heat exchanger 6 and the heat source side heat exchanger 4, the intermediate heat exchanger 7 is connected.

In the state of the refrigerant circuit 210, the low-pressure refrigerant (see point A in FIGS. 39 and 43 to 45) is sucked into the compression mechanism 2 from the suction pipe 2a and first compressed to an intermediate pressure by the compression element 2c. Thereafter, the refrigerant is discharged into the intermediate refrigerant pipe 8 (see point B in FIGS. 39 and 43 to 45). Unlike the cooling operation, the intermediate-pressure refrigerant discharged from the upstream-side compression element 2c does not pass through the intermediate heat exchanger 7 and is supplied to the drain heater 97 provided in the intermediate heat exchanger bypass pipe 9. In the drain heater 97, cooling is performed by exchanging heat with the drain water generated in the heat source side heat exchanger 4 functioning as a refrigerant evaporator and flowing down the heat source side heat exchanger 4 (FIG. 39, see point C2 in FIGS. The refrigerant cooled in the drain heater 97 is further merged with the refrigerant (see point K in FIGS. 39 and 43 to 45) returned from the first second-stage injection pipe 19 to the second-stage compression mechanism 2d. Cooling is performed (see point G in FIGS. 39 and 43 to 45). Next, the intermediate pressure refrigerant combined with the refrigerant returning from the first second-stage injection pipe 19 is sucked into the compression element 2d connected to the second-stage side of the compression element 2c and further compressed, and is discharged from the compression mechanism 2 to the discharge pipe. 2b (see point D in FIGS. 39 and 43 to 45). Here, the high-pressure refrigerant discharged from the compression mechanism 2 is subjected to the critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIG. 44) by the two-stage compression operation by the compression elements 2c and 2d as in the cooling operation. ) Compressed to a pressure exceeding The high-pressure refrigerant discharged from the compression mechanism 2 flows into the oil separator 41a constituting the oil separation mechanism 41, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the oil separator 41a flows into the oil return pipe 41b constituting the oil separation mechanism 41, and is compressed after being reduced in pressure by the pressure reduction mechanism 41c provided in the oil return pipe 41b. It is returned to the suction pipe 2a of the mechanism 2 and again sucked into the compression mechanism 2. Next, the high-pressure refrigerant after the refrigerating machine oil is separated in the oil separation mechanism 41 is sent to the use side heat exchanger 6 functioning as a refrigerant radiator through the check mechanism 42 and the switching mechanism 3 to be cooled. It is cooled by exchanging heat with water or air as a source (see point F in FIGS. 39 and 43 to 45). Then, the high-pressure refrigerant cooled in the use side heat exchanger 6 flows into the receiver inlet pipe 18a through the inlet check valve 17b of the bridge circuit 17, and a part thereof is branched to the first second-stage injection pipe 19. . The refrigerant flowing through the first second-stage injection pipe 19 is sent to the economizer heat exchanger 20 after being reduced to the vicinity of the intermediate pressure at the first second-stage injection valve 19a (points in FIGS. 39 and 43 to 45). J). Further, the refrigerant branched to the first second-stage injection pipe 19 flows into the economizer heat exchanger 20, and is cooled by exchanging heat with the refrigerant flowing through the first second-stage injection pipe 19 (FIG. 39, (See point H in FIGS. 43 to 45). On the other hand, the refrigerant flowing through the first rear-stage-side injection pipe 19 is heated by exchanging heat with the high-pressure refrigerant cooled in the heat source-side heat exchanger 4 as a radiator (see FIGS. 39 and 43 to 45). As described above, the refrigerant merges with the intermediate pressure refrigerant discharged from the preceding compression element 2c. Then, the high-pressure refrigerant cooled in the economizer heat exchanger 20 is decompressed to near the saturation pressure by the first expansion mechanism 5a and temporarily stored in the receiver 18 (see point I in FIGS. 39 and 43). Then, the refrigerant stored in the receiver 18 is sent to the receiver outlet pipe 18b and is reduced in pressure by the second expansion mechanism 5b to become a low-pressure gas-liquid two-phase refrigerant, and the outlet check valve 17d of the bridge circuit 17 is supplied. Through the intermediate heat exchanger return pipe 94 and also to the intermediate heat exchanger 7 functioning as the refrigerant evaporator (FIG. 39, FIG. 39). 43 to point E in FIG. 45). Then, the low-pressure gas-liquid two-phase refrigerant sent to the heat source side heat exchanger 4 is heated and evaporated by exchanging heat with air as a heating source supplied by the heat source side fan 40. (Refer to point A in FIGS. 39 and 43 to 45). Further, the low-pressure gas-liquid two-phase refrigerant sent to the intermediate heat exchanger 7 is also heated and evaporated by exchanging heat with air as a heating source supplied by the heat source side fan 40. (See point V in FIGS. 39 and 43-45). The low-pressure refrigerant heated and evaporated in the heat source side heat exchanger 4 is again sucked into the compression mechanism 2 via the switching mechanism 3. The low-pressure refrigerant heated and evaporated in the intermediate heat exchanger 7 is again sucked into the compression mechanism 2 through the second suction return pipe 92. In this way, the heating operation is performed.

And also in the air conditioning apparatus 1 (refrigeration apparatus) of this modification, the same effect as the cooling operation in the modification 4 of the second embodiment described above can be obtained. Moreover, in this modification, as in the cooling operation, the first rear-stage injection pipe 19 and the economizer heat exchanger 20 are provided to branch the refrigerant sent from the heat source-side heat exchanger 4 to the expansion mechanisms 5a and 5b. Since the pressure is returned to the compression element 2d on the rear stage side, the temperature of the refrigerant sucked into the compression element 2d on the rear stage side can be further reduced without performing heat radiation to the outside like the intermediate heat exchanger 7. Yes (see points C1 and G in FIG. 45). Thereby, the temperature of the refrigerant discharged from the compression mechanism 2 is further suppressed (see points D and D ′ in FIG. 45), and the point in FIG. 45 is compared with the case where the first second-stage injection pipe 19 is not provided. Since the heat dissipation loss corresponding to the area surrounded by connecting C1, D ′, D, and G can be further reduced, the operating efficiency can be further improved.

In the present modification, the first post-stage injection pipe 19 and the economizer heat exchanger 20 are provided in the configuration in which the drain heater 97 is provided below the heat source side heat exchanger 4 in the above-described modification 4. However, the drain heater 97 as in the first to third modifications of the second embodiment described above is provided in the bottom plate 77 that functions as a drain pan, the bottom of the heat source side heat exchanger 4 and the bottom plate 77 that functions as a drain pan. In the provided configuration, the first second-stage injection pipe 19 and the economizer heat exchanger 20 may be provided.
Further, in this modification, switching between the refrigerant non-return state and the refrigerant return state is performed according to the open / close state of the on-off valves 11, 12, 92a, but as in the above-described fifth modification of the second embodiment. In addition, instead of the on-off valves 11, 12, 92a, an intermediate heat exchanger switching valve 93 or the like capable of switching between the refrigerant non-return state and the refrigerant return state may be provided.

(9) Modification 7
In the refrigerant circuit 210 (see FIG. 39) in the modified example 6 of the second embodiment described above, as described above, the cooling operation in which the switching mechanism 3 is in the cooling operation state and the heating operation in which the switching mechanism 3 is in the heating operation state. In any of the above, by performing intermediate pressure injection by the economizer heat exchanger 20, the temperature of the refrigerant discharged from the compression element 2d on the rear stage side is reduced, and the power consumption of the compression mechanism 2 is reduced to improve the operation efficiency. I try to plan. And since the intermediate pressure injection by the economizer heat exchanger 20 can be used even under the condition that the intermediate pressure in the refrigeration cycle is increased to near the critical pressure, the refrigerant circuit 10 in the second embodiment and the modification thereof, 110 and 210 (see FIGS. 14, 31 and 39) are considered to be particularly advantageous in the case of using a refrigerant operating in the supercritical region, in a configuration having one usage-side heat exchanger 6. It is done.

However, for the purpose of performing cooling and heating according to the air conditioning load of a plurality of air-conditioned spaces, the configuration includes a plurality of usage-side heat exchangers 6 connected in parallel to each other, and each usage-side heat exchanger In order to obtain the refrigeration load required in each use side heat exchanger 6 by controlling the flow rate of the refrigerant flowing through the receiver 6, the receiver 18 as a gas-liquid separator and the use side heat exchanger 6 can be obtained. The use side expansion mechanism 5c may be provided so as to correspond to each use side heat exchanger 6.
For example, although not shown in detail, in the refrigerant circuit 210 (see FIG. 39) having the bridge circuit 17 in the modified example 6 of the second embodiment described above, a plurality of (here, two) connected in parallel to each other. While providing the use side heat exchanger 6, it corresponds to each use side heat exchanger 6 between the receiver 18 (more specifically, the bridge circuit 17) as a gas-liquid separator and the use side heat exchanger 6. Thus, the use side expansion mechanism 5c is provided (see FIG. 46), the second expansion mechanism 5b provided in the receiver outlet pipe 18b is deleted, and the outlet check valve 17d of the bridge circuit 17 is replaced with the heating operation. Sometimes, it is conceivable to provide a third expansion mechanism (not shown) that depressurizes the refrigerant to a low pressure in the refrigeration cycle.

Even in such a configuration, the first expansion mechanism 5a as the heat source side expansion mechanism after being cooled in the heat source side heat exchanger 4 as the radiator, like the cooling operation in which the switching mechanism 3 is in the cooling operation state. In the condition where the pressure difference from the high pressure in the refrigeration cycle to the vicinity of the intermediate pressure in the refrigeration cycle can be used without performing any significant pressure reduction operation, the intermediate pressure by the economizer heat exchanger 20 is the same as in the above-described modification 6. Injection is advantageous.
However, as in the heating operation in which the switching mechanism 3 is in the heating operation state, each use-side expansion mechanism 5c is used as a radiator so that the refrigeration load required in each use-side heat exchanger 6 as a radiator can be obtained. The flow rate of the refrigerant flowing through each usage-side heat exchanger 6 is controlled, and the flow rate of the refrigerant passing through each usage-side heat exchanger 6 as a radiator is the same as that of each usage-side heat exchanger 6 as a radiator. Under conditions generally determined by the refrigerant decompression operation by the opening degree control of the use side expansion mechanism 5c provided on the downstream side and the upstream side of the economizer heat exchanger 20, the opening degree control of each use side expansion mechanism 5c is performed. The degree of decompression of the refrigerant varies depending not only on the flow rate of the refrigerant flowing through each use side heat exchanger 6 as a radiator but also on the state of flow distribution among the use side heat exchangers 6 as a plurality of radiators. Multiple use-side swelling Since the degree of decompression may vary greatly between the mechanisms 5c, or the degree of decompression in the use-side expansion mechanism 5c may be relatively large, the refrigerant pressure at the inlet of the economizer heat exchanger 20 becomes low. In such a case, the amount of heat exchanged in the economizer heat exchanger 20 (i.e., the flow rate of the refrigerant flowing through the first second-stage injection pipe 19) may be reduced, making it difficult to use. Particularly, in such an air conditioner 1, a heat source unit mainly including the compression mechanism 2, the heat source side heat exchanger 4 and the receiver 18 and a utilization unit mainly including the utilization side heat exchanger 6 are connected by a communication pipe. When configured as a separate type air conditioner, this connection pipe may be very long depending on the arrangement of the utilization unit and the heat source unit. Therefore, the influence of the pressure loss is also added, and the economizer heat exchanger 20 The refrigerant pressure at the inlet of the refrigerant will further decrease. If the refrigerant pressure at the inlet of the economizer heat exchanger 20 is likely to decrease, the gas-liquid separator pressure and the intermediate pressure in the refrigeration cycle (if the gas-liquid separator pressure is lower than the critical pressure) Here, intermediate pressure injection by a gas-liquid separator that can be used is advantageous even under a condition in which the pressure difference from the pressure of the refrigerant flowing through the intermediate refrigerant pipe 8 is small.

In addition, as described above, for the purpose of performing cooling or heating according to the air conditioning load of a plurality of air-conditioned spaces, the configuration includes a plurality of usage-side heat exchangers 6 connected in parallel to each other, In order to control the flow rate of the refrigerant flowing through the use side heat exchanger 6 and obtain the refrigeration load required in each use side heat exchanger 6, the receiver 18 and the use side heat exchanger 6 When the configuration in which the use side expansion mechanism 5c is provided so as to correspond to each use side heat exchanger 6 is used during the cooling operation, the first expansion mechanism 5a reduces the pressure to near the saturation pressure and the receiver. The refrigerant temporarily stored in 18 (see point L in FIG. 46) is distributed to each use-side expansion mechanism 5c, but the refrigerant sent from the receiver 18 to each use-side expansion mechanism 5c is gas-liquid two-phase. Each use is in state Since the time distribution to the expansion mechanisms 5c which may cause uneven flow, it is desirable that the refrigerant fed from the receiver 18 to the usage-side expansion mechanisms 5c as possible supercooled state.

Therefore, in this modification, as shown in FIG. 46, in order to allow the receiver 18 to function as a gas-liquid separator and perform intermediate pressure injection, the receiver 18 is provided with a second second-stage injection pipe 18c. In the cooling operation, the intermediate pressure injection by the economizer heat exchanger 20 is performed, and in the heating operation, the intermediate pressure injection by the receiver 18 as a gas-liquid separator can be performed, and the receiver 18 The refrigerant circuit 310 is provided with a supercooling heat exchanger 96 as a cooler and a third suction return pipe 95 as a return pipe between the expansion side 5c and the use side expansion mechanism 5c.
Here, the second second-stage injection pipe 18c is a refrigerant pipe capable of performing intermediate pressure injection by extracting the refrigerant from the receiver 18 and returning it to the second-stage compression element 2d of the compression mechanism 2. The upper part of the receiver 18 is connected to the intermediate refrigerant pipe 8 (that is, the suction side of the compression element 2d on the rear stage side of the compression mechanism 2). The second second-stage injection pipe 18c is provided with a second second-stage injection on-off valve 18d and a second second-stage injection check mechanism 18e. The second second-stage injection on / off valve 18d is a valve that can be opened and closed, and is an electromagnetic valve in this modification. The second second-stage injection check mechanism 18e allows the refrigerant flow from the receiver 18 to the second-stage compression element 2d and blocks the refrigerant flow from the second-stage compression element 2d to the receiver 18. This is a mechanism, and a check valve is used in this modification. The second rear injection pipe 18c and the first suction return pipe 18f are integrated with each other on the receiver 18 side. Further, the second rear-stage injection pipe 18c and the first rear-stage injection pipe 19 are integrally formed on the intermediate refrigerant pipe 8 side. In the present modification, the use side expansion mechanism 5c is an electric expansion valve. In the present modification, as described above, the first second-stage injection pipe 19 and the economizer heat exchanger 20 are used during the cooling operation, and the second second-stage injection pipe 18c is used during the heating operation. Therefore, it is not necessary to make the flow direction of the refrigerant to the economizer heat exchanger 20 constant regardless of the cooling operation and the heating operation, so the bridge circuit 17 is omitted and the configuration of the refrigerant circuit 210 is simplified.

The third suction return pipe 95 branches the refrigerant sent from the heat source side heat exchanger 4 serving as a radiator to the use side heat exchanger 6 serving as an evaporator, and sucks the compression mechanism 2 (that is, the suction pipe). It is a refrigerant pipe returned to 2a). In the present modification, the third suction return pipe 95 is provided so as to branch the refrigerant sent from the receiver 18 to the use-side expansion mechanism 5c. More specifically, the third suction return pipe 95 branches the refrigerant from the upstream position of the supercooling heat exchanger 96 (that is, between the receiver 18 and the economizer heat exchanger 20) and flows to the suction pipe 2a. It is provided to return. The third suction return pipe 95 is provided with a third suction return valve 95a capable of opening degree control. The third suction return valve 95a is an electric expansion valve in this modification.
In addition, the supercooling heat exchanger 96 includes a refrigerant sent from the heat source side heat exchanger 4 as a radiator to the use side heat exchanger 6 as an evaporator and a refrigerant flowing through the third suction return pipe 95 (more specifically, Is a heat exchanger that performs heat exchange with the refrigerant after being reduced to near low pressure in the third suction return valve 95a. In the present modification, the supercooling heat exchanger 96 is a refrigerant that flows through a position upstream of the use side expansion mechanism 5c (that is, between the position where the third suction return pipe 95 is branched and the use side expansion mechanism 5c). And the refrigerant flowing through the third suction return pipe 95 are provided for heat exchange. In the present modification, the supercooling heat exchanger 96 is provided on the downstream side of the position where the third suction return pipe 95 is branched. For this reason, the refrigerant cooled in the heat source side heat exchanger 4 as the radiator passes through the economizer heat exchanger 20 as the cooler, and then is branched to the third suction return pipe 95 to be subcooled heat exchanger 96. In this case, heat exchange with the refrigerant flowing through the third suction return pipe 95 is performed.

The suction pipe 2 a or the compression mechanism 2 is provided with a suction pressure sensor 60 that detects the pressure of the refrigerant flowing on the suction side of the compression mechanism 2. A supercooling heat exchanger outlet temperature sensor 59 that detects the temperature of the refrigerant at the outlet of the supercooling heat exchanger 96 on the third suction return pipe 95 side is provided at the outlet of the supercooling heat exchanger 96 on the third suction return pipe 95 side. Is provided.
Next, the operation of the air conditioner 1 of the present modification will be described with reference to FIGS. Here, FIG. 47 is a diagram showing the refrigerant flow in the air conditioner 1 during the cooling operation, and FIG. 48 is a pressure-enthalpy diagram illustrating the refrigeration cycle during the cooling operation. FIG. 50 is a temperature-entropy diagram illustrating a refrigeration cycle during cooling operation, FIG. 50 is a diagram illustrating the flow of refrigerant in the air conditioner 1 during heating operation, and FIG. 51 is during heating operation. FIG. 52 is a pressure-enthalpy diagram illustrating the refrigeration cycle, and FIG. 52 is a temperature-entropy diagram illustrating the refrigeration cycle during the heating operation. Note that operation control in the following cooling operation and heating operation is performed by the control unit (not shown) in the above-described embodiment. In the following description, “high pressure” means high pressure in the refrigeration cycle (that is, pressure at points D, D ′, E, H, I, and R in FIGS. 48 and 49 and point D in FIGS. 51 and 52). , D ′, F), and “low pressure” means low pressure in the refrigeration cycle (that is, pressure at points A, F, S in FIGS. 48 and 49, and points A, E, “Intermediate pressure” means an intermediate pressure in the refrigeration cycle (ie, points B, C1, G, J, K in FIGS. 48 and 49, and points B, C2, Pressure in G, I, L, and M).

<Cooling operation>
During the cooling operation, the switching mechanism 3 is in the cooling operation state indicated by the solid lines in FIGS. The opening degree of the first expansion mechanism 5a and the use-side expansion mechanism 5c as the heat source side expansion mechanism is adjusted. Further, when the switching mechanism 3 is in the cooling operation state, it is heated in the economizer heat exchanger 20 through the first second-stage injection pipe 19 without performing intermediate pressure injection by the receiver 18 as a gas-liquid separator. The intermediate pressure injection by the economizer heat exchanger 20 for returning the refrigerant to the compression element 2d on the rear stage side is performed. More specifically, the second second-stage injection on / off valve 18d is closed, and the opening degree of the first second-stage injection valve 19a is adjusted in the same manner as in Modification 6 of the second embodiment described above. In addition, when the switching mechanism 3 is in the cooling operation state, the degree of opening of the third suction return valve 95a is also adjusted because the supercooling heat exchanger 96 is used. More specifically, in this modification, the third suction return valve 95a adjusts the opening so that the degree of superheat of the refrigerant at the outlet of the supercooling heat exchanger 96 on the third suction return pipe 95 side becomes the target value. In other words, so-called superheat control is performed. In this modification, the superheat degree of the refrigerant at the outlet of the supercooling heat exchanger 96 on the side of the third suction return pipe 95 is calculated by converting the low pressure detected by the suction pressure sensor 60 into a saturation temperature, and the supercooling heat exchange outlet temperature. This is obtained by subtracting the saturation temperature value of the refrigerant from the refrigerant temperature detected by the sensor 59. Although not adopted in this modification, a temperature sensor is provided at the inlet of the third cooling return pipe 95 side of the supercooling heat exchanger 96, and the refrigerant temperature detected by this temperature sensor is used as the supercooling heat exchange outlet. By subtracting from the refrigerant temperature detected by the temperature sensor 59, the degree of superheat of the refrigerant at the outlet on the third suction return pipe 95 side of the supercooling heat exchanger 96 may be obtained. Further, the adjustment of the opening degree of the third suction return valve 95a is not limited to the superheat degree control. For example, the opening degree of the third suction return valve 95a may be opened by a predetermined opening degree according to the refrigerant circulation amount in the refrigerant circuit 310. Good. Since the switching mechanism 3 is in the cooling operation state, the intermediate heat exchanger on / off valve 12 of the intermediate refrigerant pipe 8 is opened, and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is closed. As a result, the intermediate heat exchanger 7 is put into a state of functioning as a cooler, the refrigerant does not flow into the drain heater 97, and the second suction return on / off valve 92a of the second suction return pipe 92 is By being closed, the intermediate heat exchanger 7 is not connected to the suction side of the compression mechanism 2, and the intermediate heat exchanger return on / off valve 94a of the intermediate heat exchanger return pipe 94 is closed. The intermediate side heat exchanger 7 is not connected between the use side heat exchanger 6 and the heat source side heat exchanger 4.

In the state of the refrigerant circuit 310, low-pressure refrigerant (see point A in FIGS. 46 to 49) is sucked into the compression mechanism 2 from the suction pipe 2a, and is first compressed to an intermediate pressure by the compression element 2c, The refrigerant is discharged into the refrigerant pipe 8 (see point B in FIGS. 46 to 49). The intermediate pressure refrigerant discharged from the preceding compression element 2c is cooled by exchanging heat with air as a cooling source supplied by the heat source side fan 40 in the intermediate heat exchanger 7 (FIG. 46). (See point C1 in FIG. 49). The refrigerant cooled in the intermediate heat exchanger 7 is further cooled by joining with the refrigerant (see point K in FIGS. 46 to 49) returned from the first second-stage injection pipe 19 to the second-stage compression mechanism 2d. (See point G in FIGS. 46 to 49). Next, the intermediate-pressure refrigerant joined with the refrigerant returning from the first second-stage injection pipe 19 (that is, subjected to intermediate-pressure injection by the economizer heat exchanger 20) is compressed by being connected to the second-stage side of the compression element 2c. It is sucked into the element 2d, further compressed, and discharged from the compression mechanism 2 to the discharge pipe 2b (see point D in FIGS. 46 to 49). Here, the high-pressure refrigerant discharged from the compression mechanism 2 is compressed to a pressure exceeding the critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIG. 48) by the two-stage compression operation by the compression elements 2c and 2d. Has been. The high-pressure refrigerant discharged from the compression mechanism 2 flows into the oil separator 41a constituting the oil separation mechanism 41, and the accompanying refrigeration oil is separated. The refrigerating machine oil separated from the high-pressure refrigerant in the oil separator 41a flows into the oil return pipe 41b constituting the oil separation mechanism 41, and is compressed after being reduced in pressure by the pressure reduction mechanism 41c provided in the oil return pipe 41b. It is returned to the suction pipe 2a of the mechanism 2 and again sucked into the compression mechanism 2. Next, the high-pressure refrigerant after the refrigerating machine oil is separated in the oil separation mechanism 41 is sent to the heat source side heat exchanger 4 functioning as a refrigerant radiator through the check mechanism 42 and the switching mechanism 3. Then, the high-pressure refrigerant sent to the heat source side heat exchanger 4 is cooled by exchanging heat with air as a cooling source supplied by the heat source side fan 40 in the heat source side heat exchanger 4 (FIG. 46). (See point E in FIG. 49). A part of the high-pressure refrigerant cooled in the heat source side heat exchanger 4 is branched to the first second-stage injection pipe 19. The refrigerant flowing through the first second-stage injection pipe 19 is reduced to near the intermediate pressure at the first second-stage injection valve 19a, and then sent to the economizer heat exchanger 20 (see point J in FIGS. 46 to 49). . Further, the refrigerant branched into the first second-stage injection pipe 19 flows into the economizer heat exchanger 20, and is cooled by exchanging heat with the refrigerant flowing through the first second-stage injection pipe 19 (FIG. 46 to FIG. 46). (See point H in FIG. 49). On the other hand, the refrigerant flowing through the first rear-stage injection pipe 19 is heated by exchanging heat with the high-pressure refrigerant cooled in the heat source-side heat exchanger 4 as a radiator (see point K in FIGS. 46 to 49). ), As described above, the refrigerant is joined to the intermediate-pressure refrigerant discharged from the preceding compression element 2c. Then, the high-pressure refrigerant cooled in the economizer heat exchanger 20 is decompressed to near the saturation pressure by the first expansion mechanism 5a and is temporarily stored in the receiver 18 (see point I in FIGS. 46 to 49). A part of the refrigerant stored in the receiver 18 is branched to the third suction return pipe 95. Then, the refrigerant flowing through the third suction return pipe 95 is depressurized to near low pressure in the third suction return valve 95a, and then sent to the supercooling heat exchanger 96 (see point S in FIGS. 46 to 49). Further, the refrigerant branched into the third suction return pipe 95 flows into the supercooling heat exchanger 96 and is further cooled by exchanging heat with the refrigerant flowing through the third suction return pipe 95 (FIG. 46 to FIG. 46). (See point R in FIG. 49). On the other hand, the refrigerant flowing through the third suction return pipe 95 is heated by exchanging heat with the high-pressure refrigerant cooled in the economizer heat exchanger 20 (see point U in FIGS. 46 to 49). The refrigerant flows through the suction side (here, the suction pipe 2a). The refrigerant cooled in the supercooling heat exchanger 96 is sent to the use-side expansion mechanism 5c and decompressed by the use-side expansion mechanism 5c to become a low-pressure gas-liquid two-phase refrigerant, which functions as a refrigerant evaporator. To the use side heat exchanger 6 (see point F in FIGS. 46 to 49). Then, the low-pressure gas-liquid two-phase refrigerant sent to the use side heat exchanger 6 as an evaporator is heated by exchanging heat with water or air as a heating source to evaporate ( (See point A in FIGS. 46-49). Then, the low-pressure refrigerant heated and evaporated in the use side heat exchanger 6 as the evaporator is again sucked into the compression mechanism 2 via the switching mechanism 3. In this way, the cooling operation is performed.

And also in the air conditioning apparatus 1 (refrigeration apparatus) of this modification, the effect similar to the time of the cooling operation in the modification 6 of the above-mentioned 2nd Embodiment can be obtained. Moreover, in this modification, the refrigerant (see point I in FIGS. 48 and 49) sent from the receiver 18 to the use-side expansion mechanism 5c can be cooled to a supercooled state by a supercooling heat exchanger 96 as a cooler. Since this can be done (see point R in FIGS. 48 and 49), it is possible to reduce the risk of drift when distributing to each use side expansion mechanism 5c.
<Heating operation>
During the heating operation, the switching mechanism 3 is in the heating operation state indicated by the broken lines in FIGS. The opening degree of the first expansion mechanism 5a and the use-side expansion mechanism 5c as the heat source side expansion mechanism is adjusted. Further, when the switching mechanism 3 is in the heating operation state, the intermediate pressure injection by the economizer heat exchanger 20 is not performed, and the refrigerant is supplied from the receiver 18 as the gas-liquid separator through the second rear-stage injection pipe 18c. Intermediate pressure injection is performed by the receiver 18 that returns to the compression element 2d on the rear stage side. More specifically, the second second-stage injection on / off valve 18d is opened, and the first second-stage injection valve 19a is fully closed. Further, when the switching mechanism 3 is in the heating operation state, the supercooling heat exchanger 96 is not used, so that the third suction return valve 95a is also fully closed. Since the switching mechanism 3 is in a heating operation state, the intermediate heat exchanger on / off valve 12 of the intermediate refrigerant pipe 8 is closed, and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is opened. As a result, the intermediate heat exchanger 7 does not function as a cooler. Further, since the switching mechanism 3 is in the heating operation state, the state where the intermediate heat exchanger 7 and the suction side of the compression mechanism 2 are connected by opening the second suction return on / off valve 92a of the second suction return pipe 92. In addition, by opening the intermediate heat exchanger return on / off valve 94a of the intermediate heat exchanger return pipe 94, between the use side heat exchanger 6 and the heat source side heat exchanger 4, the intermediate heat exchanger 7 and Is connected.

In the state of the refrigerant circuit 310, the low-pressure refrigerant (see point A in FIGS. 46 and 50 to 52) is sucked into the compression mechanism 2 from the suction pipe 2a and first compressed to an intermediate pressure by the compression element 2c. Thereafter, the refrigerant is discharged into the intermediate refrigerant pipe 8 (see point B in FIGS. 46 and 50 to 52). The intermediate-pressure refrigerant discharged from the preceding-stage compression element 2c does not pass through the intermediate heat exchanger 7, unlike the cooling operation, in the intermediate-pressure refrigerant discharged from the preceding-stage compression element 2c. Then, it flows into a drain heater 97 provided in the intermediate heat exchanger bypass pipe 9 and is generated in the heat source side heat exchanger 4 functioning as an evaporator of the refrigerant in the drain heater 97 and is generated in the heat source side heat exchanger 4. The water is cooled by exchanging heat with the drain water flowing down (see point C2 in FIGS. 46 and 50 to 52). The refrigerant cooled in the drain heater 97 is further cooled by joining with the refrigerant (FIGS. 46 and 50 to 52) returned from the receiver 18 to the second-stage compression mechanism 2d through the second second-stage injection pipe 18c. (Refer to point G in FIGS. 46 and 50 to 52.) Next, the intermediate pressure refrigerant combined with the refrigerant returning from the second second-stage injection pipe 18c is compressed into the compression element connected to the second-stage side of the compression element 2c. 2d and further compressed, and discharged from the compression mechanism 2 to the discharge pipe 2b (see point D in FIGS. 46 and 50 to 52), where the high-pressure refrigerant discharged from the compression mechanism 2 is As in the cooling operation, the pressure is compressed to a pressure exceeding the critical pressure (that is, the critical pressure Pcp at the critical point CP shown in FIG. 51) by the two-stage compression operation by the compression elements 2c and 2d. The high-pressure refrigerant discharged from the compression mechanism 2 flows into the oil separator 41a constituting the oil separation mechanism 41, and the accompanying refrigeration oil is separated, and the high-pressure refrigerant in the oil separator 41a. The refrigeration oil separated from the refrigerant flows into the oil return pipe 41b constituting the oil separation mechanism 41, and after being decompressed by the decompression mechanism 41c provided in the oil return pipe 41b, is returned to the suction pipe 2a of the compression mechanism 2. Then, the refrigerant is sucked into the compression mechanism 2. Next, the high-pressure refrigerant after the refrigerating machine oil is separated in the oil separation mechanism 41 is used to function as a refrigerant radiator through the check mechanism 42 and the switching mechanism 3. It is sent to the side heat exchanger 6 and cooled by exchanging heat with water or air as a cooling source (see point F in FIGS. 46 and 50 to 52). Use cooled high-pressure refrigerant After the pressure is reduced to near the intermediate pressure by the expansion mechanism 5c, it is temporarily stored in the receiver 18 and gas-liquid separation is performed (see points I, L, and M in FIGS. 46 and 50 to 52). The gas refrigerant separated from the gas and liquid in the receiver 18 is extracted from the upper part of the receiver 18 by the second second-stage injection pipe 18c, and becomes the intermediate-pressure refrigerant discharged from the first-stage compression element 2c as described above. The liquid refrigerant stored in the receiver 18 is depressurized by the first expansion mechanism 5a to become a low-pressure gas-liquid two-phase refrigerant, and heat source side heat exchange functions as a refrigerant evaporator. In addition, the refrigerant is sent to the intermediate heat exchanger 7 that functions as a refrigerant evaporator through the intermediate heat exchanger return pipe 94 (see point E in FIGS. 46 and 50 to 52). Then, the low-pressure gas-liquid two-phase refrigerant sent to the heat source side heat exchanger 4 is heated and evaporated by exchanging heat with air as a heating source supplied by the heat source side fan 40. (See point A in FIGS. 46 and 50 to 52). Further, the low-pressure gas-liquid two-phase refrigerant sent to the intermediate heat exchanger 7 is also heated and evaporated by exchanging heat with air as a heating source supplied by the heat source side fan 40. (See point V in FIGS. 46 and 50-52). The low-pressure refrigerant heated and evaporated in the heat source side heat exchanger 4 is again sucked into the compression mechanism 2 via the switching mechanism 3. The low-pressure refrigerant heated and evaporated in the intermediate heat exchanger 7 is again sucked into the compression mechanism 2 through the second suction return pipe 92. In this way, the heating operation is performed.

And in the air conditioning apparatus 1 (refrigeration apparatus) of this modification, it is the 2nd point which performs the intermediate pressure injection by the receiver 18 as a gas-liquid separator instead of the intermediate pressure injection by the economizer heat exchanger 20 at the time of heating operation. Although different from the sixth modification of the embodiment, the same effects as those of the sixth modification of the second embodiment can be obtained in other respects.
In this modified example, the configuration of the modified example 6 of the second embodiment described above is configured to have a plurality of usage-side heat exchangers 6, and the injection and air by the economizer heat exchanger 20 are performed in the cooling operation and the heating operation. A configuration in which the injection by the receiver 18 as a liquid separator is selectively used and a supercooling heat exchanger 96 is provided, but the drain heater 97 as in the first to third modifications of the second embodiment described above. Are provided in the bottom plate 77 functioning as a drain pan or in the configuration provided in the lower part of the heat source side heat exchanger 4 and the bottom plate 77 functioning as a drain pan, the first rear-stage injection pipe 19 and the economizer heat exchanger 20 are provided. You may do it.

Further, in this modification, switching between the refrigerant non-return state and the refrigerant return state is performed according to the open / close state of the on-off valves 11, 12, 92a, but as in the above-described fifth modification of the second embodiment. In addition, instead of the on-off valves 11, 12, 92a, an intermediate heat exchanger switching valve 93 or the like capable of switching between the refrigerant non-return state and the refrigerant return state may be provided.
(10) Modification 8
In the second embodiment and the modification thereof, the refrigerant discharged from the compression element on the front stage of the two compression elements 2c and 2d by the compressor 21 having one uniaxial two-stage compression structure is used on the rear stage side. Although a two-stage compression type compression mechanism 2 that sequentially compresses with a compression element is configured, a multistage compression mechanism may be employed rather than a two-stage compression type such as a three-stage compression type. A multistage compression mechanism may be configured by connecting in series a plurality of compressors incorporating one compression element and / or a plurality of compressors incorporating a plurality of compression elements. In addition, when it is necessary to increase the capacity of the compression mechanism, such as when many use-side heat exchangers 6 are connected, parallel multistage compression in which two or more multistage compression type compression mechanisms are connected in parallel. A compression mechanism of the type may be adopted.

For example, as shown in FIG. 53, in the refrigerant circuit 310 (see FIG. 46) in the modified example 7 of the second embodiment described above, a two-stage compression mechanism is used instead of the two-stage compression mechanism 2. A refrigerant circuit 410 may be employed that employs a compression mechanism 102 in which 103 and 104 are connected in parallel.
Here, in the present modification, the first compression mechanism 103 includes the compressor 29 that compresses the refrigerant in two stages with the two compression elements 103c and 103d, and is branched from the suction mother pipe 102a of the compression mechanism 102. The first suction branch pipe 103 b and the first discharge branch pipe 103 b that joins the discharge mother pipe 102 b of the compression mechanism 102 are connected. In the present modification, the second compression mechanism 104 includes the compressor 30 that compresses the refrigerant in two stages with the two compression elements 104c and 104d, and the second suction mechanism branched from the suction mother pipe 102a of the compression mechanism 102. The branch pipe 104a and the second discharge branch pipe 104b joined to the discharge mother pipe 102b of the compression mechanism 102 are connected. Since the compressors 29 and 30 have the same configuration as that of the compressor 21 in the above-described embodiment and its modifications, the reference numerals indicating the parts other than the compression elements 103c, 103d, 104c, and 104d are the 29th and 30th, respectively. The description will be omitted here, with a replacement for the base. The compressor 29 sucks the refrigerant from the first suction branch pipe 103a, and after discharging the sucked refrigerant by the compression element 103c, discharges the refrigerant to the first inlet side intermediate branch pipe 81 constituting the intermediate refrigerant pipe 8. The refrigerant discharged to the first inlet-side intermediate branch pipe 81 is sucked into the compression element 103d through the intermediate mother pipe 82 and the first outlet-side intermediate branch pipe 83 constituting the intermediate refrigerant pipe 8, and the refrigerant is further compressed. It is configured to discharge to one discharge branch pipe 103b. The compressor 30 sucks the refrigerant from the second suction branch pipe 104a, compresses the sucked refrigerant by the compression element 104c, and then discharges the refrigerant to the second inlet side intermediate branch pipe 84 constituting the intermediate refrigerant pipe 8. The refrigerant discharged to the two inlet side intermediate branch pipes 84 is sucked into the compression element 104d through the intermediate mother pipe 82 and the second outlet side intermediate branch pipe 85 constituting the intermediate refrigerant pipe 8, and further compressed, so that the second discharge is performed. It is comprised so that it may discharge to the branch pipe 104b. In the present modification, the intermediate refrigerant pipe 8 is configured so that the refrigerant discharged from the compression elements 103c and 104c connected to the upstream side of the compression elements 103d and 104d is compressed by the compression element 103d connected to the downstream side of the compression elements 103c and 104c. , 104 d is a refrigerant pipe for inhalation, and mainly a first inlet side intermediate branch pipe 81 connected to the discharge side of the compression element 103 c on the front stage side of the first compression mechanism 103, and a front stage of the second compression mechanism 104. A second inlet side intermediate branch pipe 84 connected to the discharge side of the compression element 104c on the side, an intermediate mother pipe 82 where both the inlet side intermediate branch pipes 81 and 84 merge, and a first branch branched from the intermediate mother pipe 82. A first outlet side intermediate branch pipe 83 connected to the suction side of the compression element 103d on the rear stage side of the compression mechanism 103, and a suction element of the compression element 104d on the rear stage side of the second compression mechanism 104 branched from the intermediate mother pipe 82. And a second outlet-side intermediate branch tube 85 connected to the. The discharge mother pipe 102b is a refrigerant pipe for sending the refrigerant discharged from the compression mechanism 102 to the switching mechanism 3. The first discharge branch pipe 103b connected to the discharge mother pipe 102b has a first oil separation. A mechanism 141 and a first check mechanism 142 are provided, and a second oil separation mechanism 143 and a second check mechanism 144 are provided in the second discharge branch pipe 104b connected to the discharge mother pipe 102b. ing. The first oil separation mechanism 141 is a mechanism that separates the refrigeration oil accompanying the refrigerant discharged from the first compression mechanism 103 from the refrigerant and returns it to the suction side of the compression mechanism 102, and is mainly discharged from the first compression mechanism 103. The first oil separator 141a that separates the refrigeration oil accompanying the refrigerant to be cooled from the refrigerant, and the first oil separator that is connected to the first oil separator 141a and returns the refrigeration oil separated from the refrigerant to the suction side of the compression mechanism 102 And an oil return pipe 141b. The second oil separation mechanism 143 is a mechanism that separates the refrigeration oil accompanying the refrigerant discharged from the second compression mechanism 104 from the refrigerant and returns it to the suction side of the compression mechanism 102, and is mainly discharged from the second compression mechanism 104. A second oil separator 143a that separates the refrigeration oil accompanying the refrigerant from the refrigerant, and a second oil separator that is connected to the second oil separator 143a and returns the refrigeration oil separated from the refrigerant to the suction side of the compression mechanism 102. And an oil return pipe 143b. In this modification, the first oil return pipe 141b is connected to the second suction branch pipe 104a, and the second oil return pipe 143c is connected to the first suction branch pipe 103a. For this reason, the refrigerant discharged from the first compression mechanism 103 is caused by a deviation between the amount of the refrigerating machine oil accumulated in the first compression mechanism 103 and the amount of the refrigerating machine oil accumulated in the second compression mechanism 104. Even if there is a bias between the amount of refrigerating machine oil accompanying and the amount of refrigerating machine oil accompanying the refrigerant discharged from the second compression mechanism 104, the amount of refrigerating machine oil in the compression mechanisms 103 and 104 is A large amount of refrigeration oil returns to the smaller one, so that the bias between the amount of refrigeration oil accumulated in the first compression mechanism 103 and the amount of refrigeration oil accumulated in the second compression mechanism 104 is eliminated. It has become. Further, in this modification, the first suction branch pipe 103a has a portion between the junction with the second oil return pipe 143b and the junction with the suction mother pipe 102a at the junction with the suction mother pipe 102a. The second suction branch pipe 104a is configured such that the portion between the junction with the first oil return pipe 141b and the junction with the suction mother pipe 102a is the suction mother pipe. It is comprised so that it may become a downward slope toward the confluence | merging part with 102a. For this reason, even if one of the compression mechanisms 103 and 104 is stopped, the refrigerating machine oil returned from the oil return pipe corresponding to the operating compression mechanism to the suction branch pipe corresponding to the stopped compression mechanism is It will return to the suction | inhalation mother pipe 102a, and it becomes difficult to produce the oil shortage of the compression mechanism during driving | operation. The oil return pipes 141b and 143b are provided with pressure reducing mechanisms 141c and 143c for reducing the pressure of the refrigerating machine oil flowing through the oil return pipes 141b and 143b. The check mechanisms 142 and 144 allow the refrigerant flow from the discharge side of the compression mechanisms 103 and 104 to the switching mechanism 3, and block the refrigerant flow from the switching mechanism 3 to the discharge side of the compression mechanisms 103 and 104. It is a mechanism to do.

As described above, in this modification, the compression mechanism 102 includes the two compression elements 103c and 103d, and the refrigerant discharged from the compression element on the front stage among the compression elements 103c and 103d is used as the compression element on the rear stage side. And the first compression mechanism 103 configured to sequentially compress the first and second compression elements 104c and 104d, and the refrigerant discharged from the compression element on the front stage of the compression elements 104c and 104d The second compression mechanism 104 configured to sequentially compress with the compression element is connected in parallel.
Further, in the present modification, the intermediate heat exchanger 7 is provided in the intermediate mother pipe 82 constituting the intermediate refrigerant pipe 8, and is discharged from the compression element 103c on the front stage side of the first compression mechanism 103 during the cooling operation. This is a heat exchanger that cools the mixture of the refrigerant and the refrigerant discharged from the compression element 104c on the upstream side of the second compression mechanism 104. That is, the intermediate heat exchanger 7 functions as a common cooler for the two compression mechanisms 103 and 104 during the cooling operation. For this reason, simplification of the circuit configuration around the compression mechanism 102 when the intermediate heat exchanger 7 is provided with respect to the parallel multistage compression type compression mechanism 102 in which the multistage compression type compression mechanisms 103 and 104 are connected in parallel in a plurality of systems. It is illustrated.

Further, the first inlet side intermediate branch pipe 81 constituting the intermediate refrigerant pipe 8 allows the refrigerant to flow from the discharge side of the compression element 103c on the front stage side of the first compression mechanism 103 to the intermediate mother pipe 82 side, In addition, a non-return mechanism 81 a for blocking the flow of the refrigerant from the intermediate mother pipe 82 side to the discharge side of the preceding compression element 103 c is provided, and the second inlet-side intermediate branch constituting the intermediate refrigerant pipe 8 is provided. The pipe 84 allows the refrigerant to flow from the discharge side of the compression element 104c on the front stage side of the second compression mechanism 103 to the intermediate mother pipe 82 side, and the compression element 104c on the front stage side from the intermediate mother pipe 82 side. A check mechanism 84a is provided for blocking the flow of the refrigerant to the discharge side. In this modification, check valves are used as the check mechanisms 81a and 84a. For this reason, even if one of the compression mechanisms 103 and 104 is stopped, the refrigerant discharged from the compression element on the front stage side of the operating compression mechanism passes through the intermediate refrigerant pipe 8 to the front stage of the stopped compression mechanism. Therefore, the refrigerant discharged from the compression element on the upstream side of the operating compression mechanism passes through the compression element on the upstream side of the compression mechanism that is stopped. Thus, the refrigerant oil of the stopped compression mechanism does not flow out to the suction side, so that the shortage of the refrigerating machine oil when starting the stopped compression mechanism is less likely to occur. In addition, when the priority of operation is provided between the compression mechanisms 103 and 104 (for example, when the first compression mechanism 103 is a compression mechanism that operates preferentially), it corresponds to the above-described stopped compression mechanism. Since this is limited to the second compression mechanism 104, only the check mechanism 84a corresponding to the second compression mechanism 104 may be provided in this case.

Further, as described above, when the first compression mechanism 103 is a compression mechanism that operates preferentially, since the intermediate refrigerant pipe 8 is provided in common to the compression mechanisms 103 and 104, the first operating mechanism is in operation. The refrigerant discharged from the upstream compression element 103c corresponding to the compression mechanism 103 is sucked into the downstream compression element 104d of the stopped second compression mechanism 104 through the second outlet side intermediate branch pipe 85 of the intermediate refrigerant pipe 8. Accordingly, the refrigerant discharged from the compression element 103c on the front stage side of the operating first compression mechanism 103 passes through the compression element 104d on the rear stage side of the second compression mechanism 104 that is stopped. There is a possibility that the refrigerating machine oil of the stopped second compression mechanism 104 flows out to the discharge side and there is a shortage of refrigerating machine oil when starting the stopped second compression mechanism 104. Therefore, in the present modification, an opening / closing valve 85a is provided in the second outlet-side intermediate branch pipe 85, and when the second compression mechanism 104 is stopped, the opening / closing valve 85a causes the second outlet-side intermediate branch pipe 85 to The refrigerant flow is cut off. Thereby, the refrigerant discharged from the compression element 103c on the front stage side of the first compression mechanism 103 in operation passes through the second outlet side intermediate branch pipe 85 of the intermediate refrigerant pipe 8, and the rear stage side of the stopped second compression mechanism 104. Therefore, the refrigerant discharged from the compression element 103c on the front stage side of the first compression mechanism 103 during operation becomes the compression element on the rear stage side of the second compression mechanism 104 that is stopped. The refrigeration oil of the second compression mechanism 104 that is stopped through the discharge side of the compression mechanism 102 through 104d does not flow out, so that the refrigeration oil when starting the second compression mechanism 104 that is stopped is prevented. The shortage of is even less likely to occur. In this modification, an electromagnetic valve is used as the on-off valve 85a.

In the case where the first compression mechanism 103 is a compression mechanism that operates preferentially, the second compression mechanism 104 is started after the first compression mechanism 103 is started. 8 is provided in common to the compression mechanisms 103 and 104, the pressure on the discharge side of the compression element 103c on the front stage side of the second compression mechanism 104 and the pressure on the suction side of the compression element 103d on the rear stage side are Starting from a state where the pressure on the suction side of the compression element 103c and the pressure on the discharge side of the compression element 103d on the rear stage side become higher, it is difficult to start the second compression mechanism 104 stably. Therefore, in this modification, an activation bypass pipe 86 is provided to connect the discharge side of the compression element 104c on the front stage side of the second compression mechanism 104 and the suction side of the compression element 104d on the rear stage side. When the on-off valve 86a is provided and the second compression mechanism 104 is stopped, the on-off valve 86a blocks the refrigerant flow in the startup bypass pipe 86, and the on-off valve 85a provides the second outlet-side intermediate branch pipe. The refrigerant flow in 85 is interrupted, and when the second compression mechanism 104 is activated, the on-off valve 86a allows the refrigerant to flow into the activation bypass pipe 86, whereby the second compression mechanism 104 The starting bypass pipe 8 does not join the refrigerant discharged from the first-stage compression element 104c with the refrigerant discharged from the first-stage compression element 104c of the first compression mechanism 103. When the operating state of the compression mechanism 102 is stabilized (for example, when the suction pressure, the discharge pressure and the intermediate pressure of the compression mechanism 102 are stabilized), the on-off valve 85a The refrigerant can flow into the second outlet-side intermediate branch pipe 85, and the flow of the refrigerant in the startup bypass pipe 86 is blocked by the on-off valve 86a so that the normal cooling operation can be performed. It has become. In this modification, one end of the activation bypass pipe 86 is connected between the on-off valve 85a of the second outlet side intermediate branch pipe 85 and the suction side of the compression element 104d on the rear stage side of the second compression mechanism 104. The other end is connected between the discharge side of the compression element 104 c on the front stage side of the second compression mechanism 104 and the check mechanism 84 a of the second inlet side intermediate branch pipe 84 to start the second compression mechanism 104. At this time, the first compression mechanism 103 can be hardly affected by the intermediate pressure portion. In this modification, an electromagnetic valve is used as the on-off valve 86a.

In addition, the cooling operation and the heating operation of the air conditioner 1 according to this modification are changed because the circuit configuration around the compression mechanism 102 is slightly complicated by the compression mechanism 102 provided in place of the compression mechanism 2. Except for the above, the operation is basically the same as the operation in the modified example 7 of the second embodiment described above (FIGS. 46 to 52 and related descriptions), and thus the description thereof is omitted here.
And also in the structure of this modification, the effect similar to the modification 7 of the above-mentioned 2nd Embodiment can be acquired.
In this modification, in the configuration in which the drain heater 97 is provided below the heat source side heat exchanger 4 in the modification 7 of the second embodiment described above, the two-stage compression type compression mechanisms 103 and 104 are arranged in parallel. The drain mechanism 97 as in the modified examples 1 to 3 of the second embodiment described above is provided on the bottom plate 77 that functions as a drain pan, or a heat source side heat exchanger. In the structure provided in the lower plate 4 and the bottom plate 77 functioning as a drain pan, a compression mechanism 102 in which two-stage compression type compression mechanisms 103 and 104 are connected in parallel may be employed.

Further, in this modification, switching between the refrigerant non-return state and the refrigerant return state is performed according to the open / close state of the on-off valves 11, 12, 92a, but as in the above-described fifth modification of the second embodiment. In addition, instead of the on-off valves 11, 12, 92a, an intermediate heat exchanger switching valve 93 or the like capable of switching between the refrigerant non-return state and the refrigerant return state may be provided.
-Other embodiments-
As mentioned above, although embodiment of this invention and its modification were demonstrated based on drawing, specific structure is not restricted to these embodiment and its modification, It changes in the range which does not deviate from the summary of invention. Is possible.
For example, in the above-described embodiment and the modification thereof, the example in which the present invention is applied to the heat pump unit 701 of the heat pump type water heater or the air conditioner 1 has been described, but the present invention may be applied to other refrigeration apparatuses.

Further, in the above-described first embodiment and its modified examples, as in the modified example 8 of the second embodiment, the compression mechanism 102 in which the two-stage compression type compression mechanisms 103 and 104 are connected in parallel is adopted. A multi-stage compression type having more than one stage may be applied.
Moreover, in the above-mentioned 2nd Embodiment and its modification, while using the water or brine as a heating source or a cooling source which performs heat exchange with the refrigerant | coolant which flows through the utilization side heat exchanger 6, in the utilization side heat exchanger 6 The present invention may be applied to a so-called chiller type air conditioner provided with a secondary heat exchanger for exchanging heat between water or brine subjected to heat exchange and room air.
Moreover, even if it is another type of refrigeration apparatus of the above-described chiller type air conditioner, the present invention can be used as long as it performs a multistage compression refrigeration cycle using a refrigerant operating in the supercritical region as a refrigerant. Applicable.

Further, the refrigerant operating in the supercritical region is not limited to carbon dioxide, and ethylene, ethane, nitrogen oxide, or the like may be used.

By using the present invention, it is possible to suppress an increase in energy loss in a refrigeration apparatus including a refrigerant circuit having a compression mechanism, a radiator, and an evaporator, and a drain pan that receives drain water generated in the evaporator. A drain heater can be provided.

Claims (13)

1. A compression mechanism (2, 102, which has a plurality of compression elements, and is configured to sequentially compress the refrigerant discharged from the compression element on the front stage side of the plurality of compression elements by the compression element on the rear stage side. 702),
   A radiator (4, 704) for radiating the refrigerant compressed by the compression mechanism;
   An evaporator (6, 706) for evaporating the refrigerant radiated by the radiator using air as a heat source;
   Drain pans (77, 777) for receiving drain water generated in the evaporator;
   Drain heaters (97, 97a, 97b, 797, 797a, 797b) for heating the drain water by the refrigerant discharged from the former-stage compression element and sucked into the latter-stage compression element;
   A refrigeration apparatus (1, 701).
2. The refrigeration apparatus (1, 701) according to claim 1, wherein the drain heater (97, 97a, 797, 797a) is disposed below the evaporator (6, 706).
3. The refrigeration apparatus (1, 701) according to claim 1, wherein the drain heater (97, 97b, 797, 797b) is disposed in the drain pan (77, 777).
4. The drain heater (97, 797) includes a first drain heater (97a, 797a) disposed at a lower part of the evaporator (6, 706) and a second drain heater (77, 777) disposed in the drain pan (77, 777). The refrigeration apparatus (1, 701) according to claim 1, comprising a drain heater (97b, 797b).
5. The refrigerant discharged from the front-stage compression element and sucked into the rear-stage compression element is allowed to flow through only one of the first drain heater (97a, 797a) and the second drain heater (97b, 797b). The refrigeration apparatus (1, 701) according to claim 4, further comprising a drain heater switching mechanism (98, 798) for switching so as to be able to perform the operation.
6. A compression mechanism (2, 102) having a plurality of compression elements and configured to sequentially compress the refrigerant discharged from the front-stage compression elements of the plurality of compression elements by the rear-stage compression elements. When,
   A heat exchanger using air as a heat source, the heat source side heat exchanger (4) functioning as a refrigerant radiator or evaporator;
   A use side heat exchanger (6) that functions as a refrigerant evaporator or radiator;
   A cooling operation state in which the refrigerant is circulated in the order of the compression mechanism, the heat source side heat exchanger functioning as a refrigerant radiator, and the use side heat exchanger functioning as a refrigerant evaporator, and the compression mechanism, the refrigerant radiator A switching mechanism (3) that switches between a heating operation state in which the refrigerant is circulated in the order of the use side heat exchanger that functions as the heat source side heat exchanger that functions as a refrigerant evaporator;
   An intermediate heat exchanger (7) that functions as a refrigerant cooler that is discharged from the front-stage compression element and sucked into the rear-stage compression element when the switching mechanism is in the cooling operation state;
   A drain pan (77) for receiving drain water generated in the heat source side heat exchanger;
   When the switching mechanism is in the heating operation state, a drain heater capable of heating the drain water by the refrigerant discharged from the front-stage compression element and sucked into the rear-stage compression element ( 97, 97a, 97b),
   A refrigeration apparatus (1) comprising:
7. The refrigeration apparatus (1) according to claim 6, wherein the drain heater (97, 97a) is disposed at a lower part of the heat source side heat exchanger (4).
8. The refrigeration apparatus (1) according to claim 6, wherein the drain heater (97, 97b) is arranged in the drain pan (77).
9. The drain heater (97) includes a first drain heater (97a) disposed at a lower portion of the heat source side heat exchanger (4) and a second drain heater (97b) disposed in the drain pan (77). ) Refrigeration apparatus (1) according to claim 6.
10. The refrigerant discharged from the front-stage compression element and sucked into the rear-stage compression element can flow through only one of the first drain heater (97a) and the second drain heater (97b). The refrigeration apparatus (1) according to claim 9, further comprising a drain heater switching mechanism (98) for switching to.
11. The said intermediate heat exchanger (7) functions as an evaporator of the refrigerant | coolant which thermally radiated in the said utilization side heat exchanger (6), when the said switching mechanism (3) is made into the said heating operation state. The refrigeration apparatus (1) according to any one of 1 to 10.
12. The refrigeration apparatus (1) according to claim 11, wherein the intermediate heat exchanger (7) is disposed on an upper portion of the heat source side heat exchanger (4).
13. The refrigeration apparatus (1) according to any one of claims 6 to 12, wherein the intermediate heat exchanger (7) has a larger heat transfer area than the drain heater (97).
    

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