JP2009180428A - Refrigeration system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a refrigerant sucked in a compression element of a subsequent stage side from being brought into a moist state even in an operation state that a heat source temperature of an intermediate cooler is low in a refrigeration system carrying out a multistage compression type refrigerating cycle. <P>SOLUTION: An air conditioner 1 is equipped with a two-stage compression type compression mechanism 2, a heat source side heat exchanger 4, a utilization side heat exchanger 6, an intermediate cooler 7 provided in an intermediate refrigerant pipe 8 for sucking a refrigerant delivered from a precedent stage compression element 2c into a subsequent stage compression element 2d, and an intermediate cooler bypass pipe 9 connected to an intermediate refrigerant pipe 8 to bypass the intermediate cooler 7. In the air conditioner 1, when the heat source temperature of the intermediate cooler 7 or an outlet refrigerant temperature of the intermediate cooler 7 becomes lower than a saturation temperature of the refrigerant sent from the precedent stage side compression element 2c to the subsequent stage side compression element 2d, the moisture prevention control of preventing the flow of the refrigerant to the intermediate cooler 7 is carried out by using the intermediate cooler bypass pipe 9. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a refrigeration apparatus, and more particularly to a refrigeration apparatus that performs a multistage compression refrigeration cycle.

Conventionally, as one of refrigeration apparatuses that perform a multistage compression refrigeration cycle, there is an air conditioner that performs a two-stage compression refrigeration cycle as disclosed in Patent Document 1. This air conditioner mainly includes a compressor having two compression elements connected in series, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger.
JP 2007-232263 A

  In the air conditioning apparatus described above, the refrigerant discharged from the compression element on the lower stage side of the compressor is sucked into the compression element on the rear stage side of the compressor and further compressed, so that the refrigerant from the compression element on the rear stage side of the compressor For example, in an outdoor heat exchanger that functions as a refrigerant cooler, a temperature difference between air or water as a heat source and the refrigerant becomes large, and the temperature of the discharged refrigerant increases. Since the heat dissipation loss increases, there is a problem that it is difficult to obtain high operating efficiency.

  To solve this problem, an intermediate cooler that functions as a refrigerant cooler that is discharged from the former-stage compression element and sucked into the latter-stage compression element is used to compress the refrigerant discharged from the former-stage compression element on the latter-stage side. By providing the intermediate refrigerant pipe for inhaling the element, the temperature of the refrigerant sucked into the compression element on the rear stage side is lowered, and as a result, the temperature of the refrigerant discharged from the compression element on the rear stage side is lowered, It is conceivable to reduce the heat dissipation loss in the outdoor heat exchanger.

  However, in such a configuration, when the temperature of the air or water as the heat source of the intermediate cooler is low, the refrigerant discharged from the front-stage compression element and sucked into the rear-stage compression element is excessively cooled. As a result, the refrigerant sucked into the downstream compression element becomes wet, which may impair the reliability of the compressor.

  The problem of the present invention is that, in a refrigeration apparatus that performs a multistage compression refrigeration cycle, even when the heat source temperature of the intermediate cooler is low in operating conditions, the refrigerant sucked into the compression element on the rear stage side becomes wet. It is to prevent becoming.

  The refrigeration apparatus according to the first aspect of the present invention includes a heat source side heat exchanger, a use side heat exchanger, an intermediate cooler, and an intermediate cooler bypass pipe. The compression mechanism has a plurality of compression elements, and is configured to sequentially compress the refrigerant discharged from the compression element on the front stage side among the plurality of compression elements by 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 ”. The intermediate cooler is provided in an intermediate refrigerant pipe for sucking the refrigerant discharged from the compression element on the front stage side into the compression element on the rear stage side, and is discharged from the compression element on the front stage side and sucked into the compression element on the rear stage side. Functions as a refrigerant cooler. The intermediate cooler bypass pipe is connected to the intermediate refrigerant pipe so as to bypass the intermediate cooler. The refrigeration apparatus is provided with an intermediate cooler when the heat source temperature of the intermediate cooler or the outlet refrigerant temperature of the intermediate cooler is equal to or lower than the saturation temperature of the refrigerant sent from the front-stage compression element to the rear-stage compression element. Wet prevention control is performed to prevent the refrigerant from flowing into the intercooler by using a bypass pipe.

  In this refrigeration apparatus, when the heat source temperature of the intermediate cooler or the outlet refrigerant temperature of the intermediate cooler becomes equal to or lower than the saturation temperature of the refrigerant sent from the front-stage compression element to the rear-stage compression element, the intermediate cooler bypass pipe Is used to prevent the refrigerant from flowing into the intercooler, so that even if the heat source temperature of the intercooler is low, it is sucked into the downstream compression element. It is possible to prevent the refrigerant to be wet from becoming wet.

  The refrigeration apparatus according to the second invention is the refrigeration apparatus according to the first invention, wherein the intermediate cooler is a heat exchanger using air as a heat source.

  In this refrigeration apparatus, it is possible to prevent the refrigerant sucked into the compression element on the rear stage from becoming wet even when the temperature of the air that is the heat source of the intercooler is low.

  The refrigeration apparatus according to a third aspect of the present invention is the refrigeration apparatus according to the first aspect of the present invention, wherein the intermediate cooler is a heat exchanger that uses water as a heat source. The supply is stopped.

  In this refrigeration apparatus, the refrigerant sucked into the compression element on the rear stage side can be prevented from becoming wet even when the temperature of the water that is the heat source of the intermediate cooler is low. In addition, in this refrigeration apparatus, the supply of water to the intermediate cooler is stopped in the wetness prevention control, so that the refrigerant in the intermediate cooler can be prevented from being stored in a liquid state.

  A refrigeration apparatus according to a fourth invention includes a compression mechanism, a heat source side heat exchanger, a use side heat exchanger, and an intermediate cooler. The compression mechanism has a plurality of compression elements, and is configured to sequentially compress the refrigerant discharged from the compression element on the front stage side among the plurality of compression elements by 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 ”. The intermediate cooler is provided in an intermediate refrigerant pipe for sucking the refrigerant discharged from the compression element on the front stage side into the compression element on the rear stage side, and is discharged from the compression element on the front stage side and sucked into the compression element on the rear stage side. Functions as a refrigerant cooler. The refrigeration apparatus is provided with an intermediate cooler when the heat source temperature of the intermediate cooler or the outlet refrigerant temperature of the intermediate cooler is equal to or lower than the saturation temperature of the refrigerant sent from the front-stage compression element to the rear-stage compression element. Wet prevention control to reduce the flow rate of the water flowing through. Here, “decreasing the flow rate of water flowing through the intercooler” also means “stopping the supply of water to the intercooler”.

  In this refrigeration apparatus, when the heat source temperature of the intermediate cooler or the outlet refrigerant temperature of the intermediate cooler becomes equal to or lower than the saturation temperature of the refrigerant sent from the front-stage compression element to the rear-stage compression element, the intermediate cooler flows. Because wetting prevention control is performed to reduce the flow rate of water, the refrigerant sucked into the compression element on the downstream side is moistened even when the temperature of the water that is the heat source of the intercooler is low. It can be prevented from becoming a state.

  In the refrigeration apparatus according to the fifth aspect of the present invention, in the refrigeration apparatus according to the fourth aspect of the present invention, the refrigerant in which the outlet refrigerant temperature of the intermediate cooler is further sent from the front-stage compression element to the rear-stage compression element in the moisture prevention control The flow rate of water flowing through the intercooler is controlled so as to be higher than the saturation temperature of the intermediate cooler.

  In this refrigeration apparatus, in the wetting prevention control, the refrigerant flows through the intermediate cooler so that the outlet refrigerant temperature of the intermediate cooler is higher than the saturation temperature of the refrigerant sent from the front-stage compression element to the rear-stage compression element. Since the flow rate of water is controlled, not only can the refrigerant sucked into the downstream compression element be prevented from becoming wet, but also the temperature of the refrigerant sucked into the downstream compression element is made as low as possible. As a result, the temperature of the refrigerant discharged from the compression element on the rear stage side can be kept low, and the power consumption of the compression mechanism can be reduced.

  The refrigeration apparatus according to a sixth aspect of the present invention is the refrigeration apparatus according to any of the first to fifth aspects, wherein the refrigerant flows between the heat source side heat exchanger and the use side heat exchanger after being compressed by the compression mechanism. Is further provided with a rear-stage injection pipe for branching back to the rear-stage compression element.

  In this refrigeration apparatus, in addition to cooling of the refrigerant sucked into the downstream compression element by the intermediate cooler, the temperature of the refrigerant sucked into the downstream compression element is further increased by intermediate injection using the rear injection pipe. Since the temperature can be kept low, the temperature of the refrigerant discharged from the compression mechanism can be further reduced, and the power consumption of the compression mechanism can be reduced.

  As described above, according to the present invention, the following effects can be obtained.

  In the first aspect of the invention, it is possible to prevent the refrigerant sucked into the compression element on the rear stage from getting wet even when the heat source temperature of the intermediate cooler is low.

  In the second aspect of the invention, even when the temperature of the air that is a heat source of the intermediate cooler is low, it is possible to prevent the refrigerant sucked into the compression element on the rear stage from becoming wet. .

  In the third aspect of the invention, the refrigerant sucked into the downstream compression element can be prevented from becoming wet even when the temperature of the water that is the heat source of the intercooler is low. In addition, in the wetting prevention control, the supply of water to the intermediate cooler is stopped, so that the refrigerant in the intermediate cooler can be prevented from being stored in a liquid state.

  In the fourth aspect of the invention, even when the temperature of the water that is the heat source of the intermediate cooler is low, it is possible to prevent the refrigerant sucked into the subsequent compression element from becoming wet. .

  In the fifth aspect of the invention, not only can the refrigerant sucked into the compression element on the rear stage side be prevented from becoming wet, but also the temperature of the refrigerant sucked into the compression element on the rear stage side is made as low as possible. The temperature of the refrigerant discharged from the downstream compression element can be kept low, and the power consumption of the compressor can be reduced.

  In the sixth invention, the temperature of the refrigerant discharged from the compression mechanism can be further reduced, and the power consumption of the compression mechanism can be reduced.

  Hereinafter, an embodiment of a refrigeration apparatus according to the present invention will be described based on the drawings.

(1) Configuration of Air Conditioner FIG. 1 is a schematic configuration diagram of an air conditioner 1 as an embodiment of a refrigeration apparatus according to the present invention. The air conditioner 1 includes a refrigerant circuit 10 configured to be capable of cooling operation, and performs a two-stage compression refrigeration cycle using a refrigerant (here, carbon dioxide) that operates in a supercritical region. Device.

  The refrigerant circuit 10 of the air conditioner 1 mainly includes a compression mechanism 2, a heat source side heat exchanger 4, an expansion mechanism 5, a use side heat exchanger 6, and an intermediate cooler 7.

  In this embodiment, the compression mechanism 2 includes a compressor 21 that compresses the 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 is a refrigerant pipe for sucking the refrigerant 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. is there. The discharge pipe 2b is a refrigerant pipe for sending the refrigerant discharged from the compression mechanism 2 to the heat source side heat exchanger 4, and the discharge pipe 2b is provided with an oil separation mechanism 41 and a check mechanism 42. ing. 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 allows the refrigerant to flow from the discharge side of the compression mechanism 2 to the heat source side heat exchanger 4 and blocks the refrigerant flow from the heat source side heat exchanger 4 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 heat source side heat exchanger 4 is a heat exchanger that functions as a refrigerant cooler. The heat source side heat exchanger 4 has one end connected to the compression mechanism 2 and the other end connected to the expansion mechanism 5. The heat source side heat exchanger 4 is a heat exchanger that uses air as a heat source (that is, a cooling source). The air as the heat source is supplied to the heat source side heat exchanger 4 by a heat source side fan (not shown).

  The expansion mechanism 5 is a mechanism that depressurizes the refrigerant, and an electric expansion valve is used in the present embodiment. One end of the expansion mechanism 5 is connected to the heat source side heat exchanger 4, and the other end is connected to the use side heat exchanger 6. In the present embodiment, the expansion mechanism 5 decompresses the high-pressure refrigerant cooled in the heat source side heat exchanger 4 before sending it to the use side heat exchanger 6.

  The use-side heat exchanger 6 is a heat exchanger that functions as a refrigerant heater. One end of the use side heat exchanger 6 is connected to the expansion mechanism 5, and the other end is connected to the compression mechanism 2. The use-side heat exchanger 6 is a heat exchanger that uses air or water as a heat source (that is, a heating source).

  The intermediate cooler 7 is a heat exchanger that is provided in the intermediate refrigerant pipe 8 and functions as a refrigerant cooler that is discharged from the preceding compression element 2c and sucked into the compression element 2d. The intercooler 7 is a heat exchanger that uses air as a heat source (that is, a cooling source). The air as the heat source is supplied to the intercooler 7 by a heat source side fan (not shown). The intermediate cooler 7 may be integrated with the heat source side heat exchanger 4. In this case, the heat source side fan is common to both the heat source side heat exchanger 4 and the intermediate cooler 7, so that the heat source There are also cases where air is supplied. Thus, the intermediate cooler 7 can be called a cooler using an external heat source in the sense that it does not use the refrigerant circulating in the refrigerant circuit 10.

  An intermediate cooler bypass pipe 9 is connected to the intermediate refrigerant pipe 8 so as to bypass the intermediate cooler 7. The intermediate cooler bypass pipe 9 is a refrigerant pipe that limits the flow rate of the refrigerant flowing through the intermediate cooler 7. The intermediate cooler bypass pipe 9 is provided with an intermediate cooler bypass opening / closing valve 11. The intermediate cooler bypass on-off valve 11 is an electromagnetic valve in the present embodiment. In the present embodiment, the intermediate cooler bypass on-off valve 11 is basically closed except when a temporary operation such as wetness prevention control described later is performed.

  Further, the intermediate refrigerant pipe 8 has a position on the intermediate cooler 7 side from the connection with the intermediate cooler bypass pipe 9 (that is, an intermediate from the connection with the intermediate cooler bypass pipe 9 on the inlet side of the intermediate cooler 7). A cooler on / off valve 12 is provided on a portion of the cooler 7 up to the connection portion on the outlet side. The cooler on / off valve 12 is a mechanism that limits the flow rate of the refrigerant flowing through the intermediate cooler 7. The cooler on / off valve 12 is an electromagnetic valve in the present embodiment. In the present embodiment, the cooler on / off valve 12 is basically opened except when a temporary operation such as wetness prevention control described later is performed. In the present embodiment, the cooler on / off valve 12 is provided at a position on the inlet side of the intermediate cooler 7.

  The intermediate refrigerant pipe 8 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 from the discharge side of the rear-stage compression element 2d to the front stage. A check mechanism 15 for blocking the flow of the refrigerant to the compression element 2c on the side is provided. The check mechanism 15 is a check valve in the present embodiment. In the present embodiment, the check mechanism 15 is provided in a portion from the outlet side of the intermediate cooler 7 of the intermediate refrigerant pipe 8 to the connection portion with the intermediate cooler bypass pipe 9.

  Furthermore, the air conditioning apparatus 1 is provided with various sensors. Specifically, an intermediate cooler outlet temperature sensor 52 that detects the temperature of the refrigerant at the outlet of the intermediate cooler 7 is provided at the outlet of the intermediate cooler 7. The air conditioner 1 is provided with an air temperature sensor 53 that detects the temperature of air as a heat source of the intercooler 7. The intermediate refrigerant pipe 8 is provided with an intermediate pressure sensor 54 that detects an intermediate pressure of the compression mechanism that is the pressure of the refrigerant flowing through the intermediate refrigerant pipe 8. In addition, the air conditioner 1 controls the operation of each part constituting the air conditioner 1 such as the compression mechanism 2, the expansion mechanism 5, the intermediate cooler bypass on / off valve 11, and the cooler on / off valve 12, although not shown here. It has a control part.

(2) Operation | movement of an air conditioning apparatus Next, operation | movement of the air conditioning apparatus 1 of this embodiment is demonstrated using FIGS. 1-3. 2 is a pressure-enthalpy diagram illustrating the refrigeration cycle during the cooling operation, and FIG. 3 is a temperature-entropy diagram illustrating the refrigeration cycle during the cooling operation. The operation control in the following cooling operation and the anti-wetting control for preventing the refrigerant sucked into the compression element on the rear stage from being wet by the cooling in the intermediate cooler 7 are 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. 2 and 3), and “low pressure” means low pressure in the refrigeration cycle ( That is, it means the pressure at points A and F in FIGS. 2 and 3, and “intermediate pressure” and “compression mechanism intermediate pressure” mean intermediate pressures in the refrigeration cycle (that is, at points B1 and C1 in FIGS. Pressure).

  During the cooling operation, the opening degree of the expansion mechanism 5 is adjusted. Then, the cooler on / off valve 12 is opened, and the intermediate cooler bypass on / off valve 11 of the intermediate cooler bypass pipe 9 is closed, so that the intermediate cooler 7 functions as a cooler.

  When the compression mechanism 2 is driven in the state of the refrigerant circuit 10, low-pressure refrigerant (see point A in FIGS. 1 to 3) is sucked into the compression mechanism 2 from the suction pipe 2a, and first, the intermediate pressure is compressed by the compression element 2c. And then discharged to the intermediate refrigerant pipe 8 (see point B1 in FIGS. 1 to 3). The intermediate-pressure refrigerant discharged from the preceding compression element 2c is cooled by exchanging heat with air as a cooling source in the intermediate cooler 7 (see point C1 in FIGS. 1 to 3). The refrigerant cooled in the intermediate cooler 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 FIG. 1 to point D in FIG. 3). 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. 2) 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 through the check mechanism 42 to the heat source side heat exchanger 4 that functions as a refrigerant cooler. Then, the high-pressure refrigerant sent to the heat source side heat exchanger 4 is cooled by exchanging heat with water or air as a cooling source in the heat source side heat exchanger 4 (point E in FIGS. 1 to 3). reference). The high-pressure refrigerant cooled in the heat source-side heat exchanger 4 is decompressed by the expansion mechanism 5 to become a low-pressure gas-liquid two-phase refrigerant, and is sent to the use-side heat exchanger 6 that functions as a refrigerant heater. (See point F in FIGS. 1 to 3). The low-pressure gas-liquid two-phase refrigerant sent to the use side heat exchanger 6 is heated and evaporated in the use side heat exchanger 6 through heat exchange with water or air as a heating source. (Refer to point A in FIGS. 1 to 3). Then, the low-pressure refrigerant heated in the use side heat exchanger 6 is again sucked into the compression mechanism 2. In this way, the cooling operation is performed.

  As described above, in the air conditioner 1, the intermediate cooler 7 is provided in the intermediate refrigerant pipe 8 for allowing the refrigerant discharged from the compression element 2c to be sucked into the compression element 2d, and the cooler on / off valve 12 is provided in the cooling operation. When the intermediate cooler 7 is not provided because the intermediate cooler 7 functions as a cooler by opening and closing the intermediate cooler bypass opening / closing valve 11 of the intermediate cooler bypass pipe 9 (this 2 and FIG. 3, the refrigeration cycle is performed in the order of point A → point B1 → point D ′ → point E → point F). The temperature of the refrigerant sucked decreases (see points B1 and C1 in FIG. 3), and the temperature of the refrigerant discharged from the compression element 2d also decreases (see points D and D ′ in FIG. 3). For this reason, in this air conditioning apparatus 1, compared with the case where the intermediate cooler 7 is not provided in the heat source side heat exchanger 4 that functions as a high-pressure refrigerant cooler, water and air as the cooling source, and the refrigerant 3 can be reduced, and the heat dissipation loss corresponding to the area surrounded by connecting the points B1, D ′, D, and C1 in FIG. 3 can be reduced, so that the operation efficiency can be improved. it can.

<Wetting prevention control>
In the cooling operation involving the cooling of the intermediate pressure refrigerant by the intermediate cooler 7 as described above, when the air as a heat source of the intermediate cooler 7 is in a low operating condition, the air is discharged from the compression element 2c on the front stage side and the rear stage side. The refrigerant sucked into the compression element 2d may be excessively cooled, and as a result, the refrigerant sucked into the compression element 2d at the rear stage becomes wet, and the reliability of the compression mechanism 2 is impaired. There is a risk of being lost.

  Therefore, in the present embodiment, when the heat source temperature of the intercooler 7 becomes equal to or lower than the saturation temperature of the refrigerant sent from the front-stage compression element 2c to the rear-stage compression element 2d, the intercooler bypass pipe 9 is In this way, wetting prevention control is performed to prevent the refrigerant from flowing into the intercooler 7. Specifically, in this embodiment, the temperature of the air as the heat source of the intermediate cooler 7 detected by the air temperature sensor 53 is obtained by converting the compression mechanism intermediate pressure detected by the intermediate pressure sensor 54. When the temperature is equal to or lower than that, the refrigerant discharged from the compression element 2c on the upstream side is opened by opening the intermediate cooler bypass on / off valve 11 of the intermediate cooler bypass pipe 9 and closing the cooler on / off valve 12. The refrigerant flows through the intermediate cooler bypass pipe 9 to the suction side of the downstream compression element 2 d, thereby preventing the intermediate pressure refrigerant from flowing into the intermediate cooler 7. In addition, when the refrigerant | coolant which operate | moves in a supercritical region like this embodiment is used, the pressure of the refrigerant | coolant discharged from the compression element 2c of the front | former stage side becomes high, and compression mechanism intermediate pressure becomes critical pressure (that is, 2, there may be an operating condition that exceeds the critical pressure Pcp at the critical point CP shown in FIG. 2, but in such an operating condition, not only a high-pressure refrigerant but also an intermediate-pressure refrigerant is called a saturated state. Since the concept does not exist, it is not necessary to perform the above-described wetting prevention control. For this reason, in this wetting prevention control, before determining whether the temperature of the air as the heat source is equal to or lower than the saturation temperature of the refrigerant sent from the front-stage compression element 2c to the rear-stage compression element 2d, the compression is performed. It is determined whether the mechanism intermediate pressure is lower than the critical pressure. If the compression mechanism intermediate pressure is equal to or higher than the critical pressure, the refrigerant is allowed to flow through the intermediate cooler 7 and sucked into the compression element 2d on the rear stage side. When the intermediate pressure of the compression mechanism is lower than the critical pressure, the temperature of the refrigerant as the heat source of the intermediate cooler 7 detected by the air temperature sensor 53 is reduced as described above. It is determined whether the temperature is equal to or lower than a saturation temperature obtained by converting the compression mechanism intermediate pressure detected by the intermediate pressure sensor 54, and the temperature of the air as the heat source of the intermediate cooler 7 is compressed. When the intermediate temperature is equal to or lower than the saturation temperature obtained by converting the intermediate pressure, the intermediate pressure refrigerant is prevented from flowing into the intermediate cooler 7, and the temperature of the air as the heat source of the intermediate cooler 7 is reduced to the compression mechanism. When the temperature is higher than the saturation temperature obtained by converting the intermediate pressure, the refrigerant is allowed to flow through the intermediate cooler 7.

  Thus, in the air conditioner 1 of the present embodiment, the temperature of the air as the heat source of the intermediate cooler 7 is equal to or lower than the saturation temperature of the intermediate-pressure refrigerant sent from the front-stage compression element 2c to the rear-stage compression element 2d. In this case, since the moisture prevention control is performed to prevent the refrigerant from flowing into the intermediate cooler 7 by using the intermediate cooler bypass pipe 9, the temperature of the air as the heat source of the intermediate cooler 7 is low. Even when the operating conditions are met, it is possible to prevent the refrigerant sucked into the subsequent compression element 2d from becoming wet.

  Further, in this air conditioner 1, when the temperature of the air as the heat source of the intermediate cooler 7 becomes equal to or lower than the saturation temperature of the intermediate-pressure refrigerant sent from the front-stage compression element 2c to the rear-stage compression element 2d. Since the cooler opening / closing valve 12 provided on the inlet side of the intermediate cooler 7 is closed, all the refrigerant discharged from the compression element 2c on the front stage side can flow to the intermediate cooler bypass pipe 9. The intermediate pressure refrigerant flowing through the intermediate refrigerant pipe 8 and the intermediate refrigerant pipe bypass pipe 9 can be prevented from flowing into the intermediate cooler 7 from the inlet side of the intermediate cooler 7 and collecting in the intermediate cooler 7. In addition, in the present embodiment, since the check mechanism 15 is provided on the outlet side of the intermediate cooler 7, the intermediate pressure refrigerant flowing through the intermediate refrigerant pipe 8 and the intermediate refrigerant pipe bypass pipe 9 is transferred to the intermediate cooler 7. It is possible to prevent the refrigerant from flowing into the intermediate cooler 7 from the outlet side and collecting in the intermediate cooler 7. In particular, the intermediate cooler 7 is integrated with the heat source side heat exchanger 4, and the heat source side heat exchanger is provided by a heat source side fan (not shown) common to both the heat source side heat exchanger 4 and the intermediate cooler 7. In the configuration in which air as a heat source is supplied to both the heat exchanger 4 and the intermediate cooler 7, as long as air as a heat source is supplied to the heat source side heat exchanger 4, air as a heat source is also supplied to the intermediate cooler 7. As a result, the intermediate pressure refrigerant may flow into the intermediate cooler 7 and accumulate in the intermediate cooler 7, so that the cooler opening / closing valve 12 and the check mechanism 15 may be provided. It is valid.

  Further, whether or not the moisture prevention control is necessary depends on whether or not the temperature of the air as the heat source of the intermediate cooler 7 is equal to or lower than the saturation temperature of the intermediate-pressure refrigerant sent from the upstream compression element 2c to the downstream compression element 2d. Instead of determining, the temperature of the refrigerant at the outlet of the intermediate cooler 7 (here, the temperature of the refrigerant detected by the intermediate cooler outlet temperature sensor 52) is changed from the compression element 2c on the front stage side to the compression element on the rear stage side. Whether or not the moisture prevention control is necessary may be determined based on whether or not the temperature is equal to or lower than the saturation temperature of the intermediate-pressure refrigerant sent to 2d.

(3) Modification 1
In the above-described embodiment, a heat exchanger using air as a heat source is used as the intermediate cooler 7. However, a heat exchanger using water as a heat source may be used as the intermediate cooler 7.

  For example, as shown in FIG. 4, water is supplied to the intermediate cooler 7 through the intermediate cooling water pipe 14, and the temperature of water as a heat source of the intermediate cooler 7 (here, the intermediate cooler 7 The temperature of the water supplied to the intermediate cooler 7 detected by the water temperature sensor 58 provided on the water inlet side) is sent from the compression element 2c on the front stage side to the compression element 2d on the rear stage side, and the saturation temperature of the intermediate pressure refrigerant Or the temperature of the refrigerant at the outlet of the intermediate cooler 7 (here, the temperature of the refrigerant detected by the intermediate cooler outlet temperature sensor 52) is changed from the compression element 2c on the rear stage side to the compression element on the rear stage side. It is determined whether or not the temperature is equal to or lower than the saturation temperature of the intermediate-pressure refrigerant sent to 2d, and the temperature of water as the heat source of the intermediate cooler 7 or the temperature of the refrigerant at the outlet of the intermediate cooler 7 is Back side pressure When it is determined that the temperature is equal to or lower than the saturation temperature of the refrigerant sent to the element 2d, the intermediate cooler bypass opening / closing valve 11 of the intermediate cooler bypass pipe 9 is opened and the cooler opening / closing valve is opened as in the above-described embodiment. By closing 12, the refrigerant discharged from the compression element 2 c at the front stage flows through the intermediate cooler bypass pipe 9 to the suction side of the compression element 2 d at the rear stage, and thereby the refrigerant at the intermediate pressure is supplied to the intermediate cooler 7. Wet prevention control may be performed so as not to flow.

  And in the structure of this modification, although the point that the heat source of the intercooler 7 is not air but water, the same effect as the above-mentioned embodiment can be obtained.

  Further, as shown in FIG. 5, the water cooling on / off valve 14 a is provided in the intermediate cooling water pipe 14, and the intermediate pressure refrigerant does not flow to the intermediate cooler 7 using the above-described intermediate cooler bypass pipe 9. In addition to performing the control, the water on / off valve 14a may be closed to stop the supply of water to the intercooler 7. Here, the water on-off valve 14a is an electromagnetic valve capable of opening / closing control.

  In this case, it is further possible to prevent the refrigerant in the intermediate cooler 7 from becoming liquid and accumulating.

(4) Modification 2
In the first modified example, water is supplied to the intermediate cooler 7 through the intermediate cooling water pipe 14, and the water on / off valve 14 a is provided in the intermediate cooling water pipe 14. When it is determined that the temperature of water as the heat source of the refrigerant or the temperature of the refrigerant at the outlet of the intercooler 7 is equal to or lower than the saturation temperature of the refrigerant sent from the front-stage compression element 2c to the rear-stage compression element 2d. The intermediate cooler bypass pipe 9 is used to prevent the intermediate pressure refrigerant from flowing into the intermediate cooler 7, and the water on / off valve 14a is closed to stop the supply of water to the intermediate cooler 7. (See FIG. 5), the intermediate cooler 7 such as the intermediate cooler bypass pipe 9 and the cooler on / off valve 12 including the intermediate cooler bypass on / off valve 12 has an intermediate pressure refrigerant. But Omit the configuration for performing control to prevent the wet prevention control for only the control to stop the supply of water to the intercooler 7 may be adopted.

  And in the structure of this modification, unlike the above-mentioned modification 1, although it will be in the state where the refrigerant | coolant is always flowing into the intercooler 7, supply of the water to the intercooler 7 is stopped, Substantially, the refrigerant flowing through the intercooler 7 is not cooled by water, so that the same effects as those of the first modification can be obtained.

(5) Modification 3
In the configuration of the above-described modification 2 (see FIG. 6), the water on-off valve 14a is configured by a valve whose opening degree can be adjusted, and the refrigerant temperature at the outlet of the intermediate cooler 7 changes from the compression element 2c on the upstream side to the downstream side. When it is determined that the temperature is equal to or lower than the saturation temperature of the refrigerant sent to the compression element 2d, the flow rate of water supplied to the intercooler 7 is decreased by reducing the opening of the water on-off valve 14a. Thus, the refrigerant sucked into the second-stage compression element 2d is prevented from becoming wet, and the refrigerant temperature at the outlet of the intermediate cooler 7 is sent from the first-stage compression element 2c to the second-stage compression element 2d. Wet prevention control for controlling the flow rate of water flowing through the intercooler 7 may be employed so as to be higher than the saturation temperature of the refrigerant to be produced.

  In the configuration of the present modification, as in Modification 2 described above, the refrigerant sucked into the compression element 2d on the rear stage side can be prevented from becoming wet, and the compression element 2d on the rear stage side can be prevented. As a result, the temperature of the refrigerant sucked into the compressor can be lowered as much as possible, and thereby the temperature of the refrigerant discharged from the compression element 2d on the rear stage side can be kept low, and the power consumption of the compression mechanism 2 can be reduced.

(6) Modification 4
In the refrigerant circuit 10 (see FIGS. 1, 4, 5, and 6) in the above-described embodiment and its modifications, the refrigerant circuit 10 includes a single use-side heat exchanger 6 and can perform a cooling operation. However, for the purpose of performing cooling or heating according to the air conditioning load of a plurality of air-conditioned spaces, a switching mechanism 3 for switching between cooling operation and heating operation, and a plurality of use side heat exchanges connected in parallel to each other And a receiver 18 that temporarily stores the refrigerant flowing between the heat source side heat exchanger 4 and the use side heat exchanger 6, and the flow rate of the refrigerant flowing through each use side heat exchanger 6 In order to be able to obtain the refrigeration load required in each use side heat exchanger 6, each use between the receiver 18 as a gas-liquid separator and the use side heat exchanger 6. Use side expansion to correspond to the side heat exchanger 6 If a mechanism 5c (e.g., in FIG. 7 and 12 described later, a structure without the second-stage injection tube 18c, 19 and economizer heat exchanger 20) is. In such a configuration, the refrigerant is returned from the receiver 18 as the gas-liquid separator to the compression element 2d on the rear stage side, and discharged from the compression element 2c on the front stage side of the compression mechanism 2 to be compressed on the rear stage side. The intermediate pressure injection that merges with the refrigerant having the intermediate pressure of the compression mechanism sucked into the cylinder is performed, the temperature of the refrigerant discharged from the compression element 2d on the rear stage side is lowered, the power consumption of the compression mechanism 2 is reduced, and the operation efficiency is improved. It is possible to plan.

  However, it has a plurality of use side heat exchangers 6 connected in parallel to each other, and a receiver 18 as a gas-liquid separator and a use side heat exchanger so as to correspond to each use side heat exchanger 6. A utilization side expansion mechanism 5c as a utilization side expansion valve is provided between the utilization side expansion mechanism 5c and the utilization side expansion mechanism 5c so that a refrigeration load required in each utilization side heat exchanger 6 can be obtained. In the configuration in which the flow rate of the refrigerant flowing through each use side heat exchanger 6 is controlled, the flow rate of the refrigerant passing through each use side heat exchanger 6 in the heating operation is downstream of each use side heat exchanger 6. In addition, the opening degree of each use side expansion mechanism 5c is generally determined by the opening degree of the use side expansion mechanism 5c provided on the upstream side of the receiver 18. As well as multiple refrigerant flow rates Depending on the state of flow distribution between the exchangers 6, the opening degree is greatly different among the plurality of use side expansion mechanisms 5 c, or the use side expansion mechanism 5 c has a relatively small opening degree. For this reason, the gas-liquid separator pressure which is the pressure of the refrigerant | coolant in the receiver 18 may fall excessively by the opening degree control of the utilization side expansion mechanism 5c at the time of heating operation. Further, 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, depending on the arrangement of the utilization unit and the heat source unit, this connecting pipe can be very long. In addition, the gas-liquid separator pressure will drop.

  For this reason, the intermediate pressure injection by the receiver 18 as a gas-liquid separator can be used even under a condition where the pressure difference between the gas-liquid separator pressure and the compression mechanism intermediate pressure is small. Thus, it is advantageous when the gas-liquid separator pressure is likely to be excessively lowered.

  However, as in the cooling operation, the first expansion mechanism 5a (for example, described later) is used as the heat source side expansion mechanism before it is cooled in the heat source side heat exchanger 4 and then flows into the receiver 18 as a gas-liquid separator. 7 and 12 (see the first expansion mechanism 5a of FIG. 7), the heat source can be used under the condition that 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 significant pressure reduction operation. The second rear-stage injection pipe 19 that branches the refrigerant flowing between the side heat exchanger 4 and the first expansion mechanism 5a and returns the refrigerant to the rear-stage compression element 2d, the heat source-side heat exchanger 4, and the first expansion mechanism 5a. And an economizer heat exchanger 20 that exchanges heat between the refrigerant flowing between the refrigerant and the refrigerant flowing through the second second-stage injection pipe 19, by heat exchange in the economizer heat exchanger 20. It is preferable that the refrigerant flowing through the second second-stage injection pipe 19 after being heated is returned to the second-stage compression element 2d (that is, intermediate pressure injection is performed by the economizer heat exchanger 20) (for example, FIG. Twelve second rear-stage injection pipes 19 and economizer heat exchanger 20). This is because the intermediate pressure injection by the economizer heat exchanger 20 changes the flow rate of the refrigerant that can be returned to the compression element 2d on the rear stage side depending on the amount of heat exchange in the economizer heat exchanger 20, and thus, as in the heating operation. When the pressure difference between the refrigerant pressure at the inlet of the economizer heat exchanger 20 and the compression mechanism intermediate pressure is small, the amount of heat exchange in the economizer heat exchanger 20 is reduced and returned to the subsequent compression element 2d. Although the flow rate of the refrigerant that can be reduced is difficult to apply, the heat exchange in the economizer heat exchanger 20 is difficult when the pressure difference between the refrigerant pressure at the inlet of the economizer heat exchanger 20 and the intermediate pressure of the compression mechanism is large. The flow rate of the refrigerant that can be returned to the compression element 2d on the rear stage side increases and the application becomes effective. That. In particular, when using a refrigerant that operates in a supercritical region, such as carbon dioxide, the high pressure in the refrigeration cycle exceeds the critical pressure, so the pressure difference between the high pressure and the intermediate pressure in the refrigeration cycle is even greater. Therefore, intermediate pressure injection by the economizer heat exchanger 20 is advantageous. In addition, when using a refrigerant that operates in a supercritical region such as carbon dioxide, the gas-liquid separator pressure rises to a pressure higher than the critical pressure, and the refrigerant in the receiver 18 as the gas-liquid separator is Since it may be difficult to separate the gas refrigerant and liquid refrigerant, 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 in consideration of this point. In terms of conditions, it is preferable to use intermediate pressure injection by the economizer heat exchanger 20.

  Therefore, in this modified example, as described above, the cooling operation and the heating operation can be switched, and a plurality of usage-side heat exchangers 6 connected in parallel to each other are provided, and each usage-side heat is provided. In order to control the flow rate of the refrigerant flowing through the exchanger 6 and obtain the refrigeration load required in each user-side heat exchanger 6, the receiver 18 as a gas-liquid separator and the user-side heat exchange The use side expansion mechanism 5c is provided so as to correspond to each use side heat exchanger 6 between the heat exchanger 6 and the refrigerant pressure on the downstream side of the use side expansion mechanism 5c may be lowered in the heating operation. In consideration of the fact, the intermediate pressure injection by the receiver 18 as a gas-liquid separator is used, and in the cooling operation, the first expansion mechanism 5a as the heat source side expansion mechanism downstream of the heat source side heat exchanger 4 is used. In view of the pressure of the refrigerant in the upstream side is maintained while high, so that use intermediate pressure injection by the economizer heat exchanger 20.

  For example, as shown in FIG. 7, in the refrigerant circuit 10 (see FIG. 1) having the intermediate cooler 7 and the intermediate cooler bypass pipe 9 using air as a heat source in the above-described embodiment, the cooling operation and the heating operation are performed. While having the structure which has the switching mechanism 3 for enabling switching, and the some utilization side heat exchanger 6 connected mutually parallel, it replaces with the expansion mechanism 5, and is the 1st expansion mechanism 5a as a heat source side expansion mechanism. 5d and a use side expansion mechanism 5c as a use side expansion valve, and further, a bridge circuit 17, a receiver 18, a first second-stage injection pipe 18c, a second second-stage injection pipe 19, and an economizer heat exchange The refrigerant circuit 610 provided with the vessel 20 can be provided.

  The switching mechanism 3 is a mechanism for switching the flow direction of the refrigerant in the refrigerant circuit 610. During the cooling operation, the heat source side heat exchanger 4 is used as a refrigerant cooler compressed by the compression mechanism 2 and used. In order for the side heat exchanger 6 to function as a heater for 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. 7, 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 refrigerant cooler to be compressed by the compression mechanism 2 and the heat source side heat exchanger 4 to function as a refrigerant heater cooled in the utilization side heat exchanger 6, Discharge side and use side heat exchanger 6 Can be connected to the suction side of the compression mechanism 2 and one end of the heat source side heat exchanger 4 (see the broken line of the switching mechanism 3 in FIG. "Heating operation state"). In this modification, 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.

  As described above, the switching mechanism 3 is provided only for the compression mechanism 2, the heat source side heat exchanger 4, the expansion mechanisms 5a and 5d, the receiver 18, the use side expansion mechanism 5c, and the use side heat exchanger 6 that constitute the refrigerant circuit 610. When paying attention, the cooling operation state in which the refrigerant is circulated in the order of the compression mechanism 2, the heat source side heat exchanger 4, the first expansion mechanism 5 a as the heat source side expansion mechanism, the receiver 18, the use side expansion mechanism 5 c, and the use side heat exchanger 6. And the compression mechanism 2, the use side heat exchanger 6, the use side expansion mechanism 5c as the use side expansion valve, the receiver 18, the third expansion mechanism 5d as the heat source side expansion mechanism, and the heat source side heat exchanger 4 in this order. The heating operation state to be circulated can be switched.

  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 this modification, the bridge circuit 17 includes three check valves 17a, 17b, and 17c and a third expansion mechanism 5d as a heat source side expansion mechanism. 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 third expansion mechanism 5d is a mechanism that depressurizes the refrigerant, and constitutes a part of the bridge circuit 17. That is, the outlet check valve 17c and the third expansion mechanism 5d 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. Therefore, the third expansion mechanism 5d is fully closed during the cooling operation in which the switching mechanism 3 is in the cooling operation state, and is connected to the receiver outlet in the heating operation in which the switching mechanism 3 is in the heating operation state. The refrigerant sent from the pipe 18b to the heat source side heat exchanger 4 is decompressed. The third expansion mechanism 5d is an electric expansion valve in this modification.

  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 this modification. One end of the first expansion mechanism 5 a is connected to the heat source side heat exchanger 4 via the bridge circuit 17, and the other end is connected to the receiver 18. In the present modification, the first expansion mechanism 5a reduces the pressure of the high-pressure refrigerant cooled in the heat source side heat exchanger 4 before sending it to the use side heat exchanger 6 during the cooling operation, and uses it during the heating operation. The high-pressure refrigerant cooled in the side heat exchanger 6 is decompressed before being sent to the heat source side heat exchanger 4. The receiver inlet pipe 18a is provided with an expansion mechanism bypass valve 5e so as to bypass the first expansion mechanism 5a. The expansion mechanism bypass valve 5e is an electromagnetic valve in the present modification.

  The receiver 18 is a container that can temporarily store the refrigerant that has been decompressed by the first expansion mechanism 5a, and has an inlet connected to the receiver inlet pipe 18a and an outlet connected to the receiver outlet pipe 18b. Has been. The receiver 18 is connected to a first rear-stage injection pipe 18c and a suction return pipe 18f. Here, the first post-stage injection pipe 18c and the suction return pipe 18f are integrated with each other on the receiver 18 side.

  The first second-stage injection pipe 18c is a refrigerant pipe that can perform intermediate pressure injection by extracting refrigerant from the receiver 18 and returning it to the second-stage compression element 2d of the compression mechanism 2. In this modification, The upper part is provided so as to connect 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 first second-stage injection pipe 18c is provided with a first second-stage injection on / off valve 18d and a first second-stage injection check mechanism 18e. The first 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 first 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 suction return pipe 18f is a refrigerant pipe that can extract the refrigerant from the receiver 18 and return it to the compression element 2c on the front stage side of the compression mechanism 2. In this modification, the upper part of the receiver 18 and the suction pipe 2a (that is, It is provided so as to be connected to the suction side of the compression element 2c on the front stage side of the compression mechanism 2. The suction return pipe 18f is provided with a suction return on-off valve 18g. The suction return on-off valve 18g is a valve that can be opened and closed, and is an electromagnetic valve in this modification.

  Thus, when the receiver 18 uses the first second-stage injection pipe 18c and the suction return pipe 18f by opening the first second-stage injection on / off valve 18d and the suction return on-off valve 18g, the heat source side heat exchanger is used. 4 functions as a gas-liquid separator that separates the refrigerant flowing between the user-side heat exchanger 6 and the expansion mechanism 5a, 5d and the user-side expansion mechanism 5c. The liquid refrigerant thus separated can be returned from the upper part of the receiver 18 to the compression element 2d on the rear stage side of the compression mechanism 2 and the compression element 2c on the front stage side.

  The use side expansion mechanism 5c is provided so as to correspond 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. In this modification, an electric expansion valve is used. One end of the use side expansion mechanism 5c is connected to the receiver 18 via the bridge circuit 17, and the other end is connected to the corresponding use side heat exchanger 6. In the present modification, the use-side expansion mechanism 5c further reduces the pressure until the refrigerant is decompressed by the first expansion mechanism 5a before being sent to the use-side heat exchanger 6 during the cooling operation, and during the heating operation. The refrigerant that has passed through the use side heat exchanger 6 is decompressed before being sent to the receiver 18.

  The second 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 second 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 second 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 cooler 7 in the intermediate refrigerant pipe 8. Here, the first rear-stage injection pipe 18c and the second rear-stage injection pipe 19 are integrated with each other on the intermediate refrigerant pipe 8 side. The second second-stage injection pipe 19 is provided with a second second-stage injection valve 19a capable of opening degree control. And the 2nd back | 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 second second-stage injection pipe 19 (more specifically, the second 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 And a refrigerant flowing between the first expansion mechanism 5a and a refrigerant flowing through the second second-stage injection pipe 19, and a flow path through which both refrigerants face each other is provided. Have. In this modification, the economizer heat exchanger 20 is provided on the downstream side of the position where the second rear-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 second 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 second second-stage injection pipe 19.

  Thus, when the switching mechanism 3 is in the cooling operation state by the bridge circuit 17, the receiver 18, the receiver inlet pipe 18 a and the receiver outlet pipe 18 b, the high-pressure refrigerant cooled in the heat source side heat exchanger 4 is , The inlet check valve 17a of the bridge circuit 17, the first expansion mechanism 5a of the receiver inlet pipe 18a, the receiver 18, the outlet check valve 17c of the bridge circuit 17, and the use side expansion mechanism 5c. You can send. In addition, when the switching mechanism 3 is in the heating operation state, the high-pressure refrigerant cooled in the use side heat exchanger 6 is used on the use side expansion mechanism 5c, the inlet check valve 17b of the bridge circuit 17, the receiver inlet pipe. It can be sent to the heat source side heat exchanger 4 through the expansion mechanism bypass valve 5e of 18a, the receiver 18, and the third expansion mechanism 5d of the bridge circuit 17.

  Further, in this modification, an economizer that detects the temperature of the refrigerant at the outlet of the economizer heat exchanger 20 on the second rear-stage injection pipe 19 side is provided at the outlet of the economizer heat exchanger 20 on the second rear-stage injection pipe 19 side. An outlet temperature sensor 55 is provided. The receiver inlet pipe 18a is provided with a gas-liquid separator temperature sensor 57 that detects the temperature of the refrigerant in the receiver 18 at a position closer to the receiver 18 than the first expansion mechanism 5a. The gas-liquid separator temperature sensor 57 may be provided on the receiver outlet pipe 18b, or may be provided directly on the receiver 18 like the bottom of the receiver 18, for example.

  Thus, in this modification, intermediate pressure injection by the receiver 18 that returns the refrigerant from the receiver 18 as a gas-liquid separator through the first second-stage injection pipe 18c to the second-stage compression element 2d, and the second second-stage injection pipe The intermediate pressure injection by the economizer heat exchanger 20 that returns the refrigerant heated in the economizer heat exchanger 20 to the compression element 2d on the rear stage side through 19 can be used properly.

  Next, operation | movement of the air conditioning apparatus 1 of this modification is demonstrated using FIGS. Here, FIG. 8 is a pressure-enthalpy diagram illustrating the refrigeration cycle during the cooling operation in the present modification, and FIG. 9 is a temperature-entropy illustrating the refrigeration cycle during the cooling operation in the present modification. FIG. 10 is a pressure-enthalpy diagram illustrating the refrigeration cycle during the heating operation in the present variation, and FIG. 11 illustrates the temperature illustrating the refrigeration cycle during the heating operation in the present variation. -Entropy diagram. In addition, the operation control in the following cooling operation and heating operation, and the control which suppresses the fall of gas-liquid separator pressure are performed by the above-mentioned control part (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. 8 and 9 and points D, D ′, F, and FIGS. 10 and 11). “Pressure at H”, and “low pressure” means low pressure in the refrigeration cycle (ie, pressure at points A and F in FIGS. 8 and 9 and pressure at points A and E in FIGS. 10 and 11). “Intermediate pressure” means intermediate pressure in the refrigeration cycle (that is, pressure at points B1, C1, and G in FIGS. 8 to 11).

<Cooling operation>
During the cooling operation, the switching mechanism 3 is in a cooling operation state indicated by a solid line in FIG. The opening degree of the first expansion mechanism 5a as the heat source side expansion mechanism and the utilization side expansion mechanism 5c as the utilization side expansion valve are adjusted. Further, the third expansion mechanism 5d and the expansion mechanism bypass valve 5e are fully closed. When the switching mechanism 3 is in the cooling operation state, it is heated in the economizer heat exchanger 20 through the second 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 first second-stage injection on / off valve 18d is closed, and the opening degree of the second second-stage injection valve 19a is adjusted. Here, the second rear-stage injection valve 19a is so-called superheat degree control whose opening degree is adjusted so that the superheat degree of the refrigerant at the outlet of the economizer heat exchanger 20 on the second rear-stage injection pipe 19 side becomes a target value. Has been made. In this modification, the superheat degree of the refrigerant at the outlet of the economizer heat exchanger 20 on the second post-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 second rear-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 second rear-stage injection pipe 19 side may be obtained by subtracting from the refrigerant temperature detected by the above. Further, the cooler on / off valve 12 is opened, and the intermediate cooler bypass on / off valve 11 of the intermediate cooler bypass pipe 9 is closed, so that the intermediate cooler 7 functions as a cooler.

  When the compression mechanism 2 is driven in the state of the refrigerant circuit 610, the low-pressure refrigerant (see point A in FIGS. 7 to 9) is sucked into the compression mechanism 2 from the suction pipe 2a, and first, the compression element 2c reaches the intermediate pressure. After being compressed, the refrigerant is discharged into the intermediate refrigerant pipe 8 (see point B1 in FIGS. 7 to 9). The intermediate-pressure refrigerant discharged from the preceding-stage compression element 2c is cooled by exchanging heat with air or water as a cooling source in the intermediate cooler 7 (see point C1 in FIGS. 7 to 9). . The refrigerant cooled in the intermediate cooler 7 is further cooled by joining with the refrigerant (see point K in FIGS. 7 to 9) returned from the second second-stage injection pipe 19 to the second-stage compression mechanism 2d (see point K in FIGS. 7 to 9). (See point G in FIGS. 7-9). Next, the intermediate-pressure refrigerant that has joined the refrigerant returning from the second second-stage injection pipe 19 (that is, the intermediate-pressure injection performed by the economizer heat exchanger 20) is compressed on 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. 7 to 9). 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. 8) by the two-stage compression operation by the compression elements 2c and 2d. Has been. Then, the high-pressure refrigerant discharged from the compression mechanism 2 is sent to the heat source side heat exchanger 4 functioning as a refrigerant cooler via the switching mechanism 3, and air, water, and heat as the cooling source. It is exchanged and cooled (see point E in FIGS. 7-9). 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 second second-stage injection pipe 19. . And the refrigerant | coolant which flows through the 2nd back | latter stage side injection pipe | tube 19 is sent to the economizer heat exchanger 20 after depressurizing to the intermediate pressure vicinity in the 2nd back | latter stage | side injection valve 19a (refer the point J of FIGS. 7-9). The refrigerant flowing through the receiver inlet pipe 18a after branching to the second second-stage injection pipe 19 flows into the economizer heat exchanger 20, and is cooled by exchanging heat with the refrigerant flowing through the second second-stage injection pipe 19. (Refer to point H in FIGS. 7 to 9). On the other hand, the refrigerant flowing through the second rear-stage injection pipe 19 is heated by exchanging heat with the refrigerant flowing through the receiver inlet pipe 18a (see point K in FIGS. 7 to 9), and as described above, the intermediate cooler 7 In this case, the refrigerant merges with the cooled refrigerant. And the high pressure refrigerant | coolant cooled in the economizer heat exchanger 20 is pressure-reduced by the 1st expansion mechanism 5a to saturation pressure vicinity, and is temporarily stored in the receiver 18 (refer the point I of FIGS. 7-9). Then, the refrigerant stored in the receiver 18 is sent to the receiver outlet pipe 18b, and is sent to the usage-side expansion mechanism 5c through the receiver outlet pipe 18b and the outlet check valve 17c of the bridge circuit 17 to be used. The refrigerant is decompressed by 5c and becomes a low-pressure gas-liquid two-phase refrigerant (see point F in FIGS. 7 to 9). And the refrigerant | coolant of the low-pressure gas-liquid two-phase state sent to the utilization side heat exchanger 6 heats by performing heat exchange with the air and water as a heating source, and evaporates (FIGS. 7-9). 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 in the structure of this modification, in addition to the cooling of the refrigerant | coolant suck | inhaled by the compression element 2d of the back | latter stage side by the intermediate | middle cooler 7, the intermediate injection using the economizer heat exchanger 20 and the 2nd back | latter stage side injection pipe 19 is used. Thus, the temperature of the refrigerant sucked into the compression element 2d on the rear stage side can be further reduced, so that the temperature of the refrigerant discharged from the compression mechanism 2 can be further reduced (points D and D ′ in FIG. 9). reference). Thereby, the power consumption of the compression mechanism 2 can be reduced and the operating efficiency can be improved.

<Heating operation>
During the heating operation, the switching mechanism 3 is in a heating operation state indicated by a broken line in FIG. The opening degree of the third expansion mechanism 5d as the heat source side expansion mechanism and the use side expansion mechanism 5c as the use side expansion valve are adjusted. Further, the expansion mechanism bypass valve 5e is fully opened so that pressure reduction by the first expansion mechanism 5a is not performed. Then, 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 a gas-liquid separator through the first 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 first second-stage injection on / off valve 18d is opened, and the second second-stage injection valve 19a is fully closed. Further, the cooler on / off valve 12 is closed, and the intermediate cooler bypass on / off valve 11 of the intermediate cooler bypass pipe 9 is opened, so that the intermediate cooler 7 does not function as a cooler.

  When the compression mechanism 2 is driven in the state of the refrigerant circuit 610, the low-pressure refrigerant (refer to the point A in FIGS. 7, 10, and 11) is sucked into the compression mechanism 2 from the suction pipe 2a, and is firstly intermediated by the compression element 2c. After being compressed to the pressure, it is discharged to the intermediate refrigerant pipe 8 (see point B1 in FIGS. 7, 10 and 11). Unlike the cooling operation, the intermediate-pressure refrigerant discharged from the preceding-stage compression element 2c passes through the intermediate cooler bypass pipe 9 without passing through the intermediate cooler 7 (that is, without being cooled). By passing (see point C1 in FIG. 7) and joining the refrigerant (see point M in FIGS. 7, 10, and 11) returned from the receiver 18 to the second-stage compression mechanism 2d through the first second-stage injection pipe 18c. It is cooled (see point G in FIGS. 7, 10 and 11). Next, the intermediate-pressure refrigerant that has joined the refrigerant returning from the first latter-stage injection pipe 18c (that is, the intermediate-pressure injection by the receiver 18 as a gas-liquid separator) is connected to the latter stage of the compression element 2c. The compressed element 2d is sucked and further compressed, and discharged from the compression mechanism 2 to the discharge pipe 2b (see point D in FIGS. 7, 10 and 11). 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. 10) by the two-stage compression operation by the compression elements 2c and 2d as in the cooling operation. ) Compressed to a pressure exceeding Then, the high-pressure refrigerant discharged from the compression mechanism 2 is sent via the switching mechanism 3 to the use side heat exchanger 6 that functions as a refrigerant cooler, and air, water, and heat as a cooling source. It is exchanged and cooled (see point F in FIGS. 7, 10 and 11). The high-pressure refrigerant cooled in the use-side heat exchanger 6 is reduced to near the intermediate pressure by the use-side expansion mechanism 5c, flows into the receiver inlet pipe 18a through the inlet check valve 17b of the bridge circuit 17, and is expanded. The gas passes through the mechanism bypass valve 5e and is temporarily stored in the receiver 18, and gas-liquid separation is performed (see points I, L, and M in FIGS. 7, 10, and 11). The gas refrigerant separated from the gas and liquid in the receiver 18 is extracted from the upper portion of the receiver 18 by the first second-stage injection pipe 18c, and has the intermediate pressure discharged from the first-stage compression element 2c as described above. It will join the refrigerant. Then, the liquid refrigerant stored in the receiver 18 is sent to the bridge circuit 17 through the receiver outlet pipe 18b, and is reduced in pressure by the third expansion mechanism 5d to become a low-pressure gas-liquid two-phase refrigerant. To the heat source side heat exchanger 4 that functions as (see point E in FIGS. 7, 10, and 11). Then, the low-pressure gas-liquid two-phase refrigerant sent to the heat source side heat exchanger 4 is heated by exchanging heat with air or water as a heating source to evaporate (FIGS. 7 and 10). , 11 point A). The low-pressure refrigerant heated 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.

  In the configuration of this modification, the intermediate injection using the receiver 18 and the first second-stage injection pipe 19 can keep the temperature of the refrigerant sucked into the second-stage compression element 2d low, so that the compression mechanism The temperature of the refrigerant discharged from 2 can be kept low (see points D and D ′ in FIG. 11). Thereby, the power consumption of the compression mechanism 2 can be reduced and the operating efficiency can be improved. However, unlike the cooling operation, the intermediate cooler 7 is not allowed to function as a cooler, and compared to the case where the intermediate cooler 7 is functioned as a cooler in the same manner as the cooling operation, the external cooler 7 is externally operated. The heat loss in the heat exchanger 6 is suppressed, and the decrease in the heating capacity in the use side heat exchanger 6 is suppressed.

<Control of superheat degree of refrigerant sucked into the compression element at the rear stage>
In this modification, in the heating operation accompanied by the intermediate pressure injection by the receiver 18 as the gas-liquid separator, for some reason, the operation condition is such that a large amount of liquid refrigerant is accumulated in the receiver 18 as the gas-liquid separator, and the gas-liquid separation If the situation becomes difficult, the liquid refrigerant may be mixed with the refrigerant returned from the receiver 18 to the downstream compression element 2d through the first downstream injection pipe 18c, and thus after intermediate pressure injection is performed. The intermediate-pressure refrigerant sucked into the compression element 2d on the rear stage in this state becomes wet, and the reliability of the compression mechanism 2 may be impaired.

  Therefore, in this modification, the degree of superheat of the refrigerant sucked into the second-stage compression element 2d is controlled by the opening / closing operation of the first second-stage injection on / off valve 18d. Specifically, in the present modification, the first second-stage injection is performed so that the degree of superheat of the refrigerant sucked into the second-stage compression element 2d after the intermediate pressure injection by the receiver 18 is not smaller than a predetermined value. The opening / closing operation of the opening / closing valve 18d is performed. Here, the degree of superheat of the refrigerant sucked into the compression element 2d at the rear stage is calculated by converting the intermediate pressure of the compression mechanism detected by the intermediate pressure sensor 54 into the saturation temperature, and the temperature of the refrigerant detected by the intermediate temperature sensor 56. The refrigerant is obtained by subtracting the saturation temperature of the refrigerant corresponding to the intermediate pressure of the compression mechanism. Further, the predetermined value of the superheat degree in this control is, for example, a few degrees C. to a few dozen degrees C. or the like in order to prevent the intermediate pressure refrigerant sucked into the compression element 2d on the rear stage side from becoming wet. A value larger than at least 0 degree is set. The opening / closing operation of the first second-stage injection on / off valve 18d is performed by changing the time ratio between the time t1 for opening the first second-stage injection on / off valve 18d and the time t2 for closing the first second-stage injection on / off valve 18d. In this modification, when the degree of superheat of the refrigerant sucked into the compression element 2d on the rear stage side is equal to or higher than a predetermined value, the intermediate pressure injection by the receiver 18 is actively performed, so that the time t2 relative to the time t1 is increased. When the time ratio is set to 0, the first second-stage injection on-off valve 18d is kept open, and when the superheat degree of the refrigerant sucked into the second-stage compression element 2d becomes smaller than a predetermined value, the receiver In order to reduce the flow rate of the refrigerant returned from 18 to the downstream compression element 2d, the direction in which the time ratio of the time t2 to the time t1 is increased (that is, the time for the first second-stage injection on / off valve 18d to be closed) is increased. To make it longer). Then, after the degree of superheat of the refrigerant sucked into the second-stage compression element 2d has recovered to a predetermined value or more, in order to increase again the flow rate of the refrigerant returned from the receiver 18 to the second-stage compression element 2d, The time ratio of time t2 to t1 is changed in a smaller direction.

  Thus, in this modification, the degree of superheat of the refrigerant discharged from the front-stage compression element 2c and sucked into the rear-stage compression element 2d is controlled by the opening / closing operation of the first second-stage injection on / off valve 18d. Therefore, even if the liquid refrigerant is mixed with the refrigerant returned to the compression element 2d on the rear stage side from the receiver 18 under the operating condition that a large amount of liquid refrigerant is accumulated in the receiver 18 as the gas-liquid separator, the receiver 18 By reducing the flow rate of the refrigerant returned to the rear-stage compression element 2d, it is possible to prevent the refrigerant sucked into the rear-stage compression element 2d from becoming wet. Thereby, in this modification, the reliability of the compression mechanism 2 at the time of heating operation is improving.

  Further, in this modification, during the cooling operation, intermediate pressure injection is performed by the economizer heat exchanger 20, and the degree of superheat of the refrigerant returned from the second rear-stage injection pipe 19 to the rear-stage compression element 2d is: The target value is controlled by adjusting the opening of the second second-stage injection valve 19a. For this reason, in the present modification, in the cooling operation, the refrigerant sucked into the downstream compression element 2d is wet due to the influence of the refrigerant returned to the downstream compression element 2d by the intermediate pressure injection by the economizer heat exchanger 20 Therefore, the reliability of the compression mechanism 2 is improved.

  Moreover, in this modification, as in the above-described embodiment, the temperature of the air as the heat source of the intermediate cooler 7 is saturated with the intermediate-pressure refrigerant sent from the front-stage compression element 2c to the rear-stage compression element 2d. When the following conditions are met, the intercooler bypass pipe 9 is used to prevent the refrigerant from flowing into the intercooler 7, so that the temperature of the air as the heat source of the intercooler 7 is reduced. Even when the operating condition is low, it is possible to prevent the refrigerant sucked into the compression element 2d on the rear stage from getting wet, and thus the reliability of the compression mechanism 2 is improved.

  As described above, in this modification, the refrigerant sucked into the compression element 2d on the rear stage is wet due to the effect of the refrigerant returned to the compression element 2d on the rear stage side by the cooling operation by the intermediate cooler 7 or the intermediate pressure injection. Therefore, the reliability of the compression mechanism 2 is improved in both the cooling operation and the heating operation.

  In the refrigerant circuit 610 (see FIG. 7), the first expansion mechanism 5a and the receiver 18 are exchanged with the heat source side heat exchanger 4 and the use side heat exchange via the bridge circuit 17 (including the third expansion mechanism 5d). As shown in FIG. 12, the bridge circuit 17 is omitted and the first expansion mechanism 5 a is connected between the heat source side heat exchanger 4 and the receiver 18. Thus, when the switching mechanism 3 is in the cooling operation state, the refrigerant flowing between the heat source side heat exchanger 4 and the use side heat exchanger 6 is converted into the first expansion mechanism 5a, the receiver 18, and the use side expansion mechanism 5c. When the switching mechanism 3 is in the heating operation state, the refrigerant flowing between the heat source side heat exchanger 4 and the use side heat exchanger 6 is used as the use side expansion mechanism 5c, the receiver 18, and the first expansion. Refrigerant circuit 7 configured to flow in the order of mechanism 5a It may be set to 0.

  In this configuration, the bridge circuit 17 is omitted, and when the switching mechanism 3 is in the heating operation state, it flows between the heat source side heat exchanger 4 and the use side heat exchanger 6. The point that the refrigerant flows in the order of the use side expansion mechanism 5c, the receiver 18, and the first expansion mechanism 5a is different (therefore, the points I and L in FIGS. 10 and 11 are interchanged), but the same as described above. An effect can be obtained.

  Moreover, in the above-described refrigerant circuits 610 and 710 (see FIGS. 7 and 12), the configuration in the above-described embodiment is adopted as the configuration of the intermediate cooler 7 and the like, but is not limited thereto, and the first to the first modified examples The configuration of 3 may be adopted.

(7) Modification 5
In the above-described embodiment and its modification, the refrigerant discharged from the front-stage compression element of the two compression elements 2c and 2d by the single uniaxial two-stage compression structure 21 is used as the rear-stage compression element. The two-stage compression type compression mechanism 2 that compresses sequentially in the above-described manner is configured. However, 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 a 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. 13, in the refrigerant circuit 610 (see FIG. 7) that does not have the bridge circuit 17 in the above-described modified example 4, instead of the two-stage compression type compression mechanism 2, two-stage compression type compression is performed. A refrigerant circuit 810 employing a compression mechanism 102 in which the mechanisms 103 and 104 are connected in parallel may be used.

  In the present modification, the first compression mechanism 103 includes a compressor 29 that compresses the refrigerant in two stages with two compression elements 103c and 103d. The first suction mechanism 103 is branched from the suction mother pipe 102a of the compression mechanism 102. The branch pipe 103a and the first discharge branch pipe 103b that joins the discharge mother pipe 102b 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 104 a and the second discharge branch pipe 104 b that joins the discharge mother pipe 102 b 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 first 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 part 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. The second oil separator 143a that separates the refrigeration oil accompanying the refrigerant to be cooled from the refrigerant, and the 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 refrigeration oil accumulated in the first compression mechanism 103 and the amount of refrigeration 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 The amount of refrigerating machine oil will return more to the smaller side, so that the bias between the amount of refrigerating machine oil accumulated in the first compression mechanism 103 and the amount of refrigerating machine oil accumulated in the second compression mechanism 104 is eliminated. It has become. Further, in the present 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.

  In the present modification, the intermediate cooler 7 is provided in the intermediate mother pipe 82 that constitutes the intermediate refrigerant pipe 8, and the refrigerant discharged from the compression element 103c on the front stage side of the first compression mechanism 103 and the second compression mechanism This is a heat exchanger that cools the refrigerant combined with the refrigerant discharged from the compression element 104c on the upstream side of 104. That is, the intermediate cooler 7 functions as a cooler common to the two compression mechanisms 103 and 104. Therefore, the circuit configuration around the compression mechanism 102 when the intermediate cooler 7 is provided for the parallel multi-stage compression type compression mechanism 102 in which the multi-stage compression type compression mechanisms 103 and 104 are connected in parallel in a plurality of systems is simplified. It has been.

  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, operations such as cooling operation, heating operation, and wetness prevention control of the air conditioner 1 of the present modified example have a slightly complicated circuit configuration around the compression mechanism 102 by the compression mechanism 102 provided in place of the compression mechanism 2. Except for the change due to the change, the operation is basically the same as the operation in the above-described embodiment and its modifications (FIGS. 1 to 12 and related descriptions), and thus the description thereof is omitted here.

  And also in the structure of this modification, the effect similar to the above-mentioned embodiment and its modification can be obtained.

  Further, as shown in FIG. 14, in the refrigerant circuit 710 (see FIG. 12) that does not include the bridge circuit 17 in the above-described modified example 4, instead of the two-stage compression type compression mechanism 2, two-stage compression type compression is performed. A refrigerant circuit 910 employing a compression mechanism 102 in which the mechanisms 103 and 104 are connected in parallel may be used.

  And in this structure, since the bridge circuit 17 is abbreviate | omitted, when switching mechanism 3 is made into a heating operation state, it flows between the heat source side heat exchanger 4 and the utilization side heat exchanger 6. Although the point that a refrigerant flows in order of use side expansion mechanism 5c, receiver 18, and the 1st expansion mechanism 5a differs from refrigerant circuit 810 (refer to Drawing 13), the same operation effect as mentioned above can be acquired.

(8) Other Embodiments Although the embodiments of the present invention and the modifications thereof have been described with reference to the drawings, the specific configuration is not limited to these embodiments and the modifications thereof, and Changes can be made without departing from the scope of the invention.

  For example, in the above-described embodiment and its modification, water or brine is used as a heating source or a cooling source for performing heat exchange with the refrigerant flowing in the use-side heat exchanger 6, and heat exchange is performed in the use-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 the water or brine and indoor 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 utilizing the present invention, in a refrigeration apparatus that performs a multistage compression refrigeration cycle, even when the heat source temperature of the intercooler is low, the refrigerant sucked into the compression element on the downstream side is in a wet state. Can be prevented.

It is a schematic block diagram of the air conditioning apparatus as one Embodiment of the freezing apparatus concerning this invention. It is the pressure-enthalpy diagram in which the refrigerating cycle at the time of air_conditionaing | cooling operation was illustrated. FIG. 3 is a temperature-entropy diagram illustrating a refrigeration cycle during cooling operation. It is a schematic block diagram of the air conditioning apparatus concerning the modification 1. It is a schematic block diagram of the air conditioning apparatus concerning the modification 1. It is a schematic block diagram of the air conditioning apparatus concerning the modification 2. It is a schematic block diagram of the air conditioning apparatus concerning the modification 4. It is the pressure-enthalpy diagram in which the refrigerating cycle at the time of air_conditionaing | cooling operation in the air conditioning apparatus concerning the modification 4 was illustrated. It is the temperature-entropy diagram in which the refrigerating cycle at the time of air_conditionaing | cooling operation in the air conditioning apparatus concerning the modification 4 was illustrated. It is a pressure-enthalpy diagram in which the refrigerating cycle at the time of heating operation in the air harmony device concerning modification 4 was illustrated. It is the temperature-entropy diagram in which the refrigerating cycle at the time of the heating operation in the air conditioning apparatus concerning the modification 4 was illustrated. It is a schematic block diagram of the air conditioning apparatus concerning the modification 4. It is a schematic block diagram of the air conditioning apparatus concerning the modification 5. It is a schematic block diagram of the air conditioning apparatus concerning the modification 5.

Explanation of symbols

1 Air conditioning equipment (refrigeration equipment)
2,102 Compression mechanism 4 Heat source side heat exchanger 6 Usage side heat exchanger 7 Intermediate cooler 8 Intermediate refrigerant pipe 9 Intermediate cooler bypass pipe 18c First rear stage side injection pipe 19 Second rear stage side injection pipe

Claims (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 source side heat exchanger (4);
A use side heat exchanger (6);
Provided in the intermediate refrigerant pipe (18) for sucking the refrigerant discharged from the front-stage compression element into the rear-stage compression element, and is discharged from the front-stage compression element to the rear-stage compression element. An intercooler (7) that functions as a cooler for the refrigerant to be sucked;
An intermediate cooler bypass pipe (9) connected to the intermediate refrigerant pipe so as to bypass the intermediate cooler;
When the heat source temperature of the intermediate cooler or the outlet refrigerant temperature of the intermediate cooler is equal to or lower than the saturation temperature of the refrigerant sent from the front-stage compression element to the rear-stage compression element, the intermediate cooler bypass pipe To prevent wetness of the refrigerant from flowing into the intercooler,
Refrigeration equipment (1).   The refrigerating apparatus (1) according to claim 1, wherein the intermediate cooler (7) is a heat exchanger using air as a heat source. The intermediate cooler (7) is a heat exchanger using water as a heat source,
In the wetting prevention control, further, the supply of water to the intercooler is stopped,
The refrigeration apparatus (1) according to claim 1. 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 source side heat exchanger (4);
A use side heat exchanger (6);
A heat exchanger using water as a heat source, provided in an intermediate refrigerant pipe (8) for sucking refrigerant discharged from the preceding-stage compression element into the latter-stage compression element, and compressing the preceding-stage compression An intermediate cooler (7) that functions as a refrigerant cooler that is discharged from the element and sucked into the compression element on the rear stage side,
When the heat source temperature of the intermediate cooler or the outlet refrigerant temperature of the intermediate cooler becomes equal to or lower than the saturation temperature of the refrigerant sent from the front-stage compression element to the rear-stage compression element, the intermediate cooler flows. We perform anti-wetting control to reduce the flow rate of water,
Refrigeration equipment (1).   In the wetting prevention control, the intermediate cooling is further performed so that the outlet refrigerant temperature of the intermediate cooler (7) is higher than the saturation temperature of the refrigerant sent from the front-stage compression element to the rear-stage compression element. The refrigeration apparatus (1) according to claim 4, wherein the flow rate of water flowing through the container is controlled.   Rear stage side injection pipes (18c, 19) for branching the refrigerant flowing between the heat source side heat exchanger (4) and the use side heat exchanger (6) and returning them to the rear stage compression element are further provided. The refrigeration apparatus (1) according to any one of claims 1 to 5, which is provided.

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