WO2009107626A1 - 冷凍装置 - Google Patents
冷凍装置 Download PDFInfo
- Publication number
- WO2009107626A1 WO2009107626A1 PCT/JP2009/053347 JP2009053347W WO2009107626A1 WO 2009107626 A1 WO2009107626 A1 WO 2009107626A1 JP 2009053347 W JP2009053347 W JP 2009053347W WO 2009107626 A1 WO2009107626 A1 WO 2009107626A1
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- WIPO (PCT)
- Prior art keywords
- heat exchanger
- refrigerant
- pipe
- compression
- pressure
- Prior art date
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B1/00—Compression machines, plants or systems with non-reversible cycle
- F25B1/10—Compression machines, plants or systems with non-reversible cycle with multi-stage compression
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B13/00—Compression machines, plants or systems, with reversible cycle
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
- F25B9/002—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant
- F25B9/008—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant the refrigerant being carbon dioxide
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2309/00—Gas cycle refrigeration machines
- F25B2309/06—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide
- F25B2309/061—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide with cycle highest pressure above the supercritical pressure
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2313/00—Compression machines, plants or systems with reversible cycle not otherwise provided for
- F25B2313/021—Indoor unit or outdoor unit with auxiliary heat exchanger not forming part of the indoor or outdoor unit
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2313/00—Compression machines, plants or systems with reversible cycle not otherwise provided for
- F25B2313/027—Compression machines, plants or systems with reversible cycle not otherwise provided for characterised by the reversing means
- F25B2313/02741—Compression machines, plants or systems with reversible cycle not otherwise provided for characterised by the reversing means using one four-way valve
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
- F25B2400/04—Refrigeration circuit bypassing means
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
- F25B2400/07—Details of compressors or related parts
- F25B2400/072—Intercoolers therefor
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
- F25B2400/13—Economisers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2600/00—Control issues
- F25B2600/17—Control issues by controlling the pressure of the condenser
Definitions
- the present invention relates to a refrigeration apparatus, and more particularly, to a refrigeration apparatus having a refrigerant circuit configured to be capable of switching between a cooling operation and a heating operation and performing a multistage compression refrigeration cycle.
- the refrigeration apparatus includes a compression mechanism, a heat source side heat exchanger that functions as a refrigerant radiator or evaporator, a use side heat exchanger that functions as a refrigerant evaporator or radiator, and a switching mechanism. And an intermediate heat exchanger.
- 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.
- 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.
- 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 switching mechanism includes a cooling operation state in which the refrigerant is circulated in the order of the compression mechanism, the heat source side heat exchanger that functions as a refrigerant radiator, and the use side heat exchanger that functions as an evaporator of the refrigerant, and the compression mechanism, the refrigerant radiator
- This is a mechanism for switching between a heating operation state in which the refrigerant is circulated in the order of the use side heat exchanger that functions as a refrigerant and the heat source side heat exchanger that functions as a refrigerant evaporator.
- the intermediate heat exchanger causes the switching mechanism to function as a refrigerant cooler that is discharged from the front-stage compression element and sucked into the rear-stage compression element. It is a heat exchanger that can function as an evaporator for the refrigerant that has dissipated heat in the use side heat exchanger.
- 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, the refrigerant from the compression element on the rear stage side of the compressor
- the temperature of the discharged refrigerant becomes high.
- the temperature difference between air or water as a heat source and the refrigerant becomes large. Since the heat dissipation loss increases, there is a problem that it is difficult to obtain high operating efficiency.
- an intermediate heat exchanger that functions as a refrigerant cooler that is discharged from the preceding compression element and sucked into the latter compression element. Since the temperature of the refrigerant sucked into the compression element at the rear stage is lowered, the temperature of the refrigerant finally discharged from the compression mechanism can be kept low compared to the case where no intermediate heat exchanger is provided. Thereby, in the cooling operation, since the heat radiation loss in the heat source side heat exchanger functioning as a refrigerant radiator is reduced, the operation efficiency during the cooling operation can be improved.
- the intermediate heat exchanger By bypassing the refrigerant sucked into the compression element so that it is not cooled in the intermediate heat exchanger, the intermediate heat exchanger is not used, so that the heating capacity in the use side heat exchanger can be increased during the heating operation. It can suppress that it becomes low and it can prevent the operating efficiency at the time of a heating operation falling.
- the intermediate heat exchanger is not used during the heating operation, the intermediate heat exchanger is provided as a heat exchanger that is used only during the cooling operation. Therefore, the intermediate heat exchanger is used during the heating operation. It becomes a device that is not. Therefore, in this refrigeration apparatus, the refrigerant that has radiated heat in the use-side heat exchanger when the switching mechanism is in the cooling operation state, the intermediate heat exchanger functions as a cooler, and the switching mechanism is in the heating operation state. To function as an evaporator. For this reason, in this refrigeration apparatus, the temperature of the refrigerant discharged from the compression mechanism can be kept low during the cooling operation, and during the heating operation, the evaporation capacity of the refrigerant can be increased and intermediate heat exchange can be performed.
- Heat dissipation from the vessel to the outside can be suppressed.
- the heat dissipation loss in the heat source side heat exchanger that functions as a refrigerant radiator can be reduced, and the operating efficiency during the cooling operation can be improved.
- the effective use of the intermediate heat exchanger can be achieved, and the heating capacity in the use side heat exchanger can be suppressed from being lowered, so that the operation efficiency during the heating operation is not lowered.
- the refrigeration apparatus is the refrigeration apparatus according to the first aspect of the invention, wherein the intermediate heat exchanger has an intermediate refrigerant pipe for sucking the refrigerant discharged from the front-stage compression element into the rear-stage compression element.
- An intermediate heat exchanger bypass pipe is connected to the intermediate refrigerant pipe so as to bypass the intermediate heat exchanger, and one end of the intermediate heat exchanger is connected to the suction side of the compression mechanism.
- an intermediate heat exchanger return pipe for connecting between the use side heat exchanger and the heat source side heat exchanger and the other end of the intermediate heat exchanger.
- the intermediate pressure refrigerant flowing through the intermediate refrigerant pipe can be cooled by the intermediate heat exchanger, and during the heating operation, the intermediate pressure refrigerant flowing through the intermediate refrigerant pipe is transferred to the intermediate heat exchanger bypass pipe.
- the intermediate heat exchanger is bypassed and a part of the refrigerant cooled in the use side heat exchanger is led to the intermediate heat exchanger by the suction return pipe and the intermediate heat exchanger return pipe to evaporate, and the compression mechanism Can be returned to the inhalation side.
- the refrigeration apparatus is the refrigeration apparatus according to the second aspect of the invention, wherein the refrigerant discharged from the compression element on the front stage side through the intermediate heat exchanger bypass pipe at the start of operation with the switching mechanism in the cooling operation state. Is sucked into the compression element on the rear stage side, and the intermediate heat exchanger is connected to the suction side of the compression mechanism through the suction return pipe.
- a refrigeration apparatus is the refrigeration apparatus according to the second or third aspect, wherein the intermediate heat exchanger return pipe is provided with a flow rate adjusting valve.
- this refrigeration apparatus it is possible to prevent the refrigerant from flowing into the intermediate heat exchanger return pipe during the cooling operation, and the flow rate of the refrigerant flowing through the heat source side heat exchanger and the flow rate of the refrigerant flowing through the intermediate heat exchanger during the heating operation. Can be reliably distributed.
- a refrigeration apparatus is the refrigeration apparatus according to any of the first to fourth aspects of the present invention, wherein the heat source side heat exchanger and the utilization side heat exchanger are used between the heat source side heat exchanger and the utilization side heat exchanger.
- the expansion device that expands the refrigerant flowing between the heat exchanger and the side heat exchanger in an isentropic manner when the refrigerant flows from the heat source side heat exchanger toward the user side heat exchanger, and from the user side heat exchanger to the heat source side
- the refrigerant is connected via a rectifying circuit that rectifies the refrigerant so that the refrigerant flows in from the inlet of the expansion device.
- the coefficient of performance can be increased and the energy can be recovered by the expansion device, so that the operation efficiency during the cooling operation and the heating operation can be further improved. it can.
- a refrigeration apparatus is the refrigeration apparatus according to the fifth aspect of the invention, wherein a gas-liquid separator that performs gas-liquid separation of the refrigerant is connected to the outlet of the expansion device, A rear-stage injection pipe for returning the gas refrigerant separated in the gas-liquid separator to the rear-stage compression element is connected.
- a gas-liquid separator that performs gas-liquid separation of the refrigerant
- a rear-stage injection pipe for returning the gas refrigerant separated in the gas-liquid separator to the rear-stage compression element is connected.
- FIG. 3 is a pressure-enthalpy diagram illustrating a refrigeration cycle during cooling operation.
- FIG. 3 is a temperature-entropy diagram illustrating a refrigeration cycle during cooling operation.
- FIG. 3 is a pressure-enthalpy diagram illustrating a refrigeration cycle during heating operation.
- FIG. 3 is a temperature-entropy diagram illustrating a refrigeration cycle during heating operation.
- FIG. 1 It is a flowchart of the cooling start control. It is a figure which shows the flow of the refrigerant
- FIG. It is a schematic block diagram of the air conditioning apparatus concerning the modification 3.
- FIG. 1 It is a schematic block diagram of the air conditioning apparatus concerning the modification 3.
- FIG. 10 is a pressure-enthalpy diagram illustrating a refrigeration cycle during cooling operation in an air conditioner according to Modification 3.
- FIG. 10 is a temperature-entropy diagram illustrating a refrigeration cycle during cooling operation in an air conditioner according to Modification 3.
- FIG. 10 is a pressure-enthalpy diagram illustrating a refrigeration cycle during heating operation in an air conditioner according to Modification 3.
- FIG. 10 is a temperature-entropy diagram illustrating a refrigeration cycle during heating operation in an air conditioner according to Modification 3. It is a schematic block diagram of the air conditioning apparatus concerning the modification 4.
- FIG. 10 is a pressure-enthalpy diagram illustrating a refrigeration cycle during heating operation in an air conditioner according to Modification 4.
- FIG. 10 is a pressure-enthalpy diagram illustrating a refrigeration cycle during heating operation in an air conditioner according to Modification 4.
- FIG. 10 is a temperature-entropy diagram illustrating a refrigeration cycle during heating operation in an air conditioner according to Modification 4. It is a schematic block diagram of the air conditioning apparatus concerning the modification 5.
- FIG. 10 is a pressure-enthalpy diagram illustrating a refrigeration cycle during cooling operation in an air conditioner according to Modification 5;
- FIG. 10 is a temperature-entropy diagram illustrating a refrigeration cycle during cooling operation in an air conditioner according to Modification 5;
- It is a schematic block diagram of the air conditioning apparatus concerning the modification 7.
- Air conditioning equipment (refrigeration equipment) 2, 102, 202, 302 Compression mechanism 3 Switching mechanism 4 Heat source side heat exchanger 6 User side heat exchanger 7,307 Intermediate heat exchanger 8, 308 Intermediate refrigerant pipe 9, 309 Intermediate heat exchanger bypass pipe 92, 392 First 2 Suction return pipe 94, 394 Intermediate heat exchanger return pipe 94b, 394b Intermediate heat exchanger return valve (flow control valve) 97 Expansion device 17 Rectifier circuit (bridge circuit) 18 Receiver (gas-liquid separator) 18c Second rear injection pipe
- 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 has a refrigerant circuit 10 configured to be capable of switching between a cooling operation and a heating operation, and uses a refrigerant (here, carbon dioxide) that operates in a supercritical region, and is a two-stage compression refrigeration cycle. It is a device that performs.
- the refrigerant circuit 10 of the air conditioner 1 mainly includes a compression mechanism 2, a switching mechanism 3, a heat source side heat exchanger 4, a bridge circuit 17, a receiver 18, a first expansion mechanism 5a, and a second expansion mechanism.
- the compression mechanism 2 includes a compressor 21 that compresses a refrigerant in two stages with two compression elements.
- the compressor 21 has a sealed structure in which a compressor drive motor 21b, a drive shaft 21c, and compression elements 2c and 2d are accommodated in a casing 21a.
- the compressor drive motor 21b is connected to the drive shaft 21c.
- the drive shaft 21c is connected to the two compression elements 2c and 2d. That is, in the compressor 21, two compression elements 2c and 2d are connected to a single drive shaft 21c, and the two compression elements 2c and 2d are both rotationally driven by the compressor drive motor 21b. It has a stage compression structure.
- the compression elements 2c and 2d are positive displacement compression elements such as a rotary type and a scroll type in the present embodiment.
- the compressor 21 sucks the refrigerant from the suction pipe 2a, compresses the sucked refrigerant by the compression element 2c, discharges the refrigerant to the intermediate refrigerant pipe 8, and discharges the refrigerant discharged to the intermediate refrigerant pipe 8 to the compression element 2d. And the refrigerant is further compressed and then discharged to the discharge pipe 2b.
- the intermediate refrigerant pipe 8 sucks the intermediate-pressure refrigerant in the refrigeration cycle discharged from the compression element 2c connected to the front stage side of the compression element 2d into the compression element 2d connected to the rear stage side of the compression element 2c. It is a refrigerant pipe for making it.
- the discharge pipe 2b is a refrigerant pipe for sending the refrigerant discharged from the compression mechanism 2 to the switching mechanism 3.
- the discharge pipe 2b is provided with an oil separation mechanism 41 and a check mechanism 42.
- the oil separation mechanism 41 is a mechanism that separates the refrigeration oil accompanying the refrigerant discharged from the compression mechanism 2 from the refrigerant and returns it to the suction side of the compression mechanism 2, and is mainly accompanied by the refrigerant discharged from the compression mechanism 2.
- An oil separator 41 a that separates the refrigeration oil from the refrigerant
- 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.
- 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 as a radiator, and discharges the compression mechanism 2 from the heat source side heat exchanger 4 as a radiator.
- This is a mechanism for blocking the flow of refrigerant to the side, and a check valve is used in this embodiment.
- the compression mechanism 2 has the two compression elements 2c and 2d, and the refrigerant discharged from the compression element on the front stage of these compression elements 2c and 2d is returned to the rear stage side.
- the compression elements are sequentially compressed by the compression elements.
- the switching mechanism 3 is a mechanism for switching the flow direction of the refrigerant in the refrigerant circuit 10, and is used as a radiator for the refrigerant compressed by the compression mechanism 2 and used in the cooling operation during the cooling operation.
- 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. 1, hereinafter, the state of the switching mechanism 3 is referred to as “cooling operation state”).
- 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.
- the compression mechanism 2 the heat source side heat exchanger 4 and the use side heat exchanger 6 constituting the refrigerant circuit 10
- the compression mechanism 2 the heat source side that functions as a refrigerant radiator.
- the heat source side heat exchanger 4 is a heat exchanger that functions as a refrigerant radiator or an evaporator. One end of the heat source side heat exchanger 4 is connected to the switching mechanism 3, and the other end is connected to the first expansion mechanism 5 a via the bridge circuit 17. Although not shown here, the heat source side heat exchanger 4 is supplied with water and air as a cooling source for exchanging heat with the refrigerant flowing through the heat source side heat exchanger 4.
- 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.
- the bridge circuit 17 has four check valves 17a, 17b, 17c, and 17d.
- the inlet check valve 17a is a check valve that only allows the refrigerant to flow from the heat source side heat exchanger 4 to the receiver inlet pipe 18a.
- the inlet check valve 17b is a check valve that allows only the refrigerant to flow from the use side heat exchanger 6 to the receiver inlet pipe 18a.
- the inlet check valves 17a and 17b have a function of circulating the refrigerant from one of the heat source side heat exchanger 4 and the use side heat exchanger 6 to the receiver inlet pipe 18a.
- the outlet check valve 17 c is a check valve that allows only the refrigerant to flow from the receiver outlet pipe 18 b to the use side heat exchanger 6.
- the outlet check valve 17d is a check valve that allows only the refrigerant to flow from the receiver outlet pipe 18b to the heat source side heat exchanger 4. That is, the outlet check valves 17c and 17d have a function of circulating the refrigerant from the receiver outlet pipe 18b to the other of the heat source side heat exchanger 4 and the use side heat exchanger 6.
- the first expansion mechanism 5a is a mechanism that depressurizes the refrigerant provided in the receiver inlet pipe 18a, and an electric expansion valve is used in the present embodiment.
- the first expansion mechanism 5a saturates the refrigerant before sending the high-pressure refrigerant cooled in the heat source side heat exchanger 4 to the use side heat exchanger 6 via the receiver 18.
- the pressure is reduced to near the pressure, and during the heating operation, the high-pressure refrigerant cooled in the use side heat exchanger 6 is reduced to near the saturation pressure of the refrigerant before being sent to the heat source side heat exchanger 4 via the receiver 18.
- the receiver 18 is depressurized by the first expansion mechanism 5a so as to be able to store surplus refrigerant generated according to the operating state such as the refrigerant circulation amount in the refrigerant circuit 10 is different between the cooling operation and the heating operation.
- the inlet is connected to the receiver inlet pipe 18a, and the outlet thereof is connected to the receiver outlet pipe 18b.
- the receiver 18 also has a first suction return pipe that can extract the refrigerant from the receiver 18 and return it to the suction pipe 2a of the compression mechanism 2 (that is, the suction side of the compression element 2c on the front stage side of the compression mechanism 2).
- 18f is connected.
- the first suction return pipe 18f is provided with a first suction return on / off valve 18g.
- the first suction return on / off valve 18g is an electromagnetic valve in the present embodiment.
- the second expansion mechanism 5b is a mechanism that depressurizes the refrigerant provided in the receiver outlet pipe 18b, and an electric expansion valve is used in the present embodiment.
- the second expansion mechanism 5b is at a low pressure in the refrigeration cycle before the refrigerant decompressed by the first expansion mechanism 5a is sent to the use-side heat exchanger 6 via the receiver 18 during the cooling operation.
- the refrigerant decompressed by the first expansion mechanism 5a is further depressurized until it reaches a low pressure in the refrigeration cycle before being sent to the heat source side heat exchanger 4 via the receiver 18.
- the use side heat exchanger 6 is a heat exchanger that functions as a refrigerant evaporator or a radiator.
- One end of the use side heat exchanger 6 is connected to the first expansion mechanism 5 a via a bridge circuit, and the other end is connected to the switching mechanism 3.
- the use side heat exchanger 6 is supplied with water and air as a heat source for exchanging heat with the refrigerant flowing through the use side heat exchanger 6.
- the heat source side heat exchanger 4 when the switching mechanism 3 is in the cooling operation state by the bridge circuit 17, the receiver 18, the receiver inlet pipe 18a, and the receiver outlet pipe 18b, the heat source side heat exchanger 4 is cooled.
- the high-pressure refrigerant is supplied to the inlet check valve 17a of the bridge circuit 17, the first expansion mechanism 5a of the receiver inlet pipe 18a, the second expansion mechanism 5b of the receiver 18, the receiver outlet pipe 18b, and the outlet check valve 17c of the bridge circuit 17. It can be sent to the use side heat exchanger 6 through.
- the switching mechanism 3 when the switching mechanism 3 is in the heating operation state, the high-pressure refrigerant cooled in the use-side heat exchanger 6 is converted into the first expansion mechanism of the inlet check valve 17b of the bridge circuit 17 and the receiver inlet pipe 18a. 5a, the receiver 18, the second expansion mechanism 5b of the receiver outlet pipe 18b, and the outlet check valve 17d of the bridge circuit 17 can be sent to the heat source side heat exchanger 4.
- the intermediate heat exchanger 7 is provided in the intermediate refrigerant pipe 8 and dissipates heat in the refrigerant cooler that is discharged from the preceding compression element 2c and sucked into the compression element 2d or in the use-side heat exchanger 6. It is a heat exchanger capable of functioning as a refrigerant evaporator. Although not shown here, the intermediate heat exchanger 7 is supplied with water and air as a cooling source for exchanging heat with the refrigerant flowing through the intermediate heat exchanger 7. Thus, the intermediate heat exchanger 7 can be said to be 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 heat exchanger bypass pipe 9 is connected to the intermediate refrigerant pipe 8 so as to bypass the intermediate heat exchanger 7.
- the intermediate heat exchanger bypass pipe 9 is a refrigerant pipe that limits the flow rate of the refrigerant flowing through the intermediate heat exchanger 7.
- the intermediate heat exchanger bypass pipe 9 is provided with an intermediate heat exchanger bypass opening / closing valve 11.
- the intermediate heat exchanger bypass on-off valve 11 is a solenoid valve in the present embodiment.
- the intermediate heat exchanger bypass on-off valve 11 basically sets the switching mechanism 3 in the cooling operation state except for a case where a temporary operation such as cooling start control described later is performed. It closes at the time and is controlled to open when the switching mechanism 3 is in the heating operation state. That is, the intermediate heat exchanger bypass on-off valve 11 is controlled to be closed when performing the cooling operation and to be opened when performing the heating operation.
- the intermediate refrigerant pipe 8 has an intermediate portion between the connecting portion of the intermediate heat exchanger bypass pipe 9 and the compression element 2c side end on the front stage side to the compression element 2c side end on the front stage side of the intermediate heat exchanger 7.
- a heat exchanger on / off valve 12 is provided.
- the intermediate heat exchanger on / off valve 12 is a mechanism that limits the flow rate of the refrigerant flowing through the intermediate heat exchanger 7.
- the intermediate heat exchanger on / off valve 12 is an electromagnetic valve in the present embodiment.
- the intermediate heat exchanger on / off valve 12 is basically in a state where the switching mechanism 3 is in a cooling operation state except for a case where a temporary operation such as cooling start control described later is performed.
- the intermediate refrigerant pipe 8 allows the refrigerant to flow from the discharge side of the upstream compression element 2c to the suction side of the downstream compression element 2d, and from the suction side of the downstream compression element 2d to the upstream side.
- a check mechanism 15 is provided for blocking the flow of the refrigerant to the discharge side of the compression element 2c on the side.
- the check mechanism 15 is a check valve in the present embodiment. In the present embodiment, the check mechanism 15 is connected to the compression element 2d side end of the intermediate heat exchanger bypass pipe 9 from the compression element 2d side end of the intermediate heat exchanger 7 on the rear stage side. It is provided in the part to the connection part.
- a second suction return pipe 92 is connected to one end of the intermediate heat exchanger 7 (here, the end on the compression element 2 c side on the front stage side), and the other end (here, the rear stage) of the intermediate heat exchanger 7.
- the intermediate heat exchanger return pipe 94 is connected to the side compression element 2d side end).
- the second suction return pipe 92 is in a state where the refrigerant discharged from the front-stage compression element 2c through the intermediate heat exchanger bypass pipe 9 is sucked into the rear-stage compression element 2d.
- the intermediate heat exchanger return pipe 94 allows the refrigerant discharged from the front-stage compression element 2c through the intermediate heat exchanger bypass pipe 9 to be sucked into the rear-stage compression element 2d, and the switching mechanism 3 is During the heating operation state, between the use side heat exchanger 6 and the heat source side heat exchanger 4 (here, the second expansion mechanism 5b for depressurizing the refrigerant until the pressure becomes low in the refrigeration cycle and the evaporator) This is a refrigerant pipe for connecting the heat source side heat exchanger 4) and the other end of the intermediate heat exchanger 7.
- one end of the second suction return pipe 92 is connected to the front end of the intermediate heat exchanger bypass pipe 9 of the intermediate refrigerant pipe 8 from the end of the compression element 2c side of the intermediate heat exchanger 7.
- the other end is connected to the suction side of the compression mechanism 2 (here, the suction pipe 2a).
- the intermediate heat exchanger return pipe 94 has one end connected to a portion from the second expansion mechanism 5 b to the heat source side heat exchanger 4, and the other end connected to the intermediate heat exchanger 7 of the intermediate refrigerant pipe 8. Is connected to the portion from the compression element 2c side end of the previous stage side to the check mechanism 15.
- the second suction return pipe 92 is provided with a second suction return on / off valve 92a
- the intermediate heat exchanger return pipe 94 is provided with an intermediate heat exchanger return on / off valve 94a.
- the second suction return on / off valve 92a and the intermediate heat exchanger return on / off valve 94a are electromagnetic valves in the present embodiment.
- the second suction return on / off valve 92a is basically in a state where the switching mechanism 3 is in the cooling operation state except for a case where a temporary operation such as cooling start control described later is performed. The control is performed so that the switching mechanism 3 is opened when the switching mechanism 3 is in the heating operation state.
- the intermediate heat exchanger return on / off valve 94a is closed when the switching mechanism 3 is in the cooling operation state, including the case where temporary operation such as cooling start control described later is performed, and the switching mechanism 3 is heated. Control to open when in the state.
- the intermediate-pressure refrigerant flowing through the intermediate refrigerant pipe 8 is mainly supplied by the intermediate heat exchanger bypass pipe 9, the second suction return pipe 92, and the intermediate heat exchanger return pipe 94 during the cooling operation.
- the refrigerant can be cooled by the intermediate heat exchanger 7, and during the heating operation, the intermediate pressure refrigerant flowing through the intermediate refrigerant pipe 8 is bypassed by the intermediate heat exchanger bypass pipe 9 and the second suction return is performed.
- the pipe 92 and the intermediate heat exchanger return pipe 94 a part of the refrigerant cooled in the use side heat exchanger 6 can be led to the intermediate heat exchanger 7 to be evaporated and returned to the suction side of the compression mechanism 2. It has become.
- the air conditioner 1 includes a compression mechanism 2, a switching mechanism 3, expansion mechanisms 5a and 5b, an intermediate heat exchanger bypass opening / closing valve 11, an intermediate heat exchanger opening / closing valve 12, a first suction return opening / closing valve. It has a control part which controls operation of each part which constitutes air harmony device 1, such as valve 18g, the 2nd suction return on-off valve 92a, and intermediate heat exchanger return on-off valve 94a.
- FIG. 2 is a diagram showing the flow of the refrigerant in the air conditioner 1 during the cooling operation
- FIG. 3 is a pressure-enthalpy diagram illustrating the refrigeration cycle during the cooling operation
- FIG. 5 is a temperature-entropy diagram illustrating a refrigeration cycle during cooling operation
- FIG. 5 is a diagram illustrating a flow of refrigerant in the air conditioner 1 during heating operation
- FIG. 6 is a diagram during heating operation
- 7 is a pressure-enthalpy diagram illustrating the refrigeration cycle
- FIG. 7 is a temperature-entropy diagram illustrating the refrigeration cycle during heating operation
- FIGS. 8 is a flowchart of the cooling start control.
- 9 is a diagram illustrating the flow of the refrigerant in the air conditioner 1 during the cooling start control.
- high pressure means high pressure in the refrigeration cycle (that is, pressure at points D, D ′, and E in FIGS. 3 and 4 and pressure at points D, D ′, and F in FIGS. 6 and 7).
- Low pressure means the low pressure in the refrigeration cycle (that is, the pressure at points A and F in FIGS. 3 and 4 and the pressure at points A, E and V in FIGS. 6 and 7).
- “Means an intermediate pressure in the refrigeration cycle that is, pressure at points B1 and C1 in FIGS. 3 and 4 and pressure at points B1, C1 and C1 'in FIGS. 6 and 7).
- the switching mechanism 3 is in the cooling operation state indicated by the solid lines in FIGS.
- the opening degree of the first expansion mechanism 5a and the second expansion mechanism 5b is adjusted. Since the switching mechanism 3 is in the cooling operation state, the intermediate heat exchanger on / off valve 12 of the intermediate refrigerant pipe 8 is opened, and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is closed. Thus, the intermediate heat exchanger 7 is brought into a state of functioning as a cooler, and the second suction return on / off valve 92a of the second suction return pipe 92 is closed, whereby the intermediate heat exchanger 7 and the compression mechanism 2 are closed.
- the suction side is not connected (except during the cooling start control described later), and the intermediate heat exchanger return on / off valve 94a of the intermediate heat exchanger return pipe 94 is closed, so that the user side The heat exchanger 6 and the heat source side heat exchanger 4 are not connected to the intermediate heat exchanger 7.
- a low-pressure refrigerant (see point A in FIGS. 1 to 4) is sucked into the compression mechanism 2 from the suction pipe 2a, and is first compressed to an intermediate pressure by the compression element 2c.
- the refrigerant is discharged into the refrigerant pipe 8 (see point B1 in FIGS. 1 to 4).
- the intermediate-pressure refrigerant discharged from the upstream-side compression element 2c is cooled by exchanging heat with water or air as a cooling source in the intermediate heat exchanger 7 (point C1 in FIGS. 1 to 4). reference).
- the refrigerant cooled in the intermediate heat exchanger 7 is then sucked into the compression element 2d connected to the rear stage side of the compression element 2c, further compressed, and discharged from the compression mechanism 2 to the discharge pipe 2b ( (See point D in FIGS. 1-4).
- 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. 3) by the two-stage compression operation by the compression elements 2c and 2d.
- the high-pressure refrigerant discharged from the compression mechanism 2 flows into the oil separator 41a constituting the oil separation mechanism 41, and the accompanying refrigeration oil is separated.
- 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.
- the high-pressure refrigerant after the refrigerating machine oil is separated in the oil separation mechanism 41 is sent to the heat source side heat exchanger 4 functioning as a refrigerant radiator through the check mechanism 42 and the switching mechanism 3.
- the high-pressure refrigerant sent to the heat source side heat exchanger 4 is cooled by exchanging heat with water or air as a cooling source in the heat source side heat exchanger 4 (point E in FIGS. 2 to 4). reference). Then, the high-pressure refrigerant cooled in the heat source side heat exchanger 4 flows into the receiver inlet pipe 18a through the inlet check valve 17a of the bridge circuit 17 and is reduced to near the saturation pressure by the first expansion mechanism 5a. (See point I in FIGS. 1 and 2).
- the refrigerant stored in the receiver 18 is sent to the receiver outlet pipe 18b and is reduced in pressure by the second expansion mechanism 5b to become a low-pressure gas-liquid two-phase refrigerant, and the outlet check valve 17c of the bridge circuit 17 is used. And is sent to the use side heat exchanger 6 functioning as a refrigerant evaporator (see point F in FIGS. 1 to 4). Then, the low-pressure gas-liquid two-phase refrigerant sent to the use side heat exchanger 6 is heated by exchanging heat with water or air as a heating source to evaporate (FIG. 1 to FIG. 1). (See point A in 4). 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.
- the intermediate heat exchanger 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 in the cooling operation, Since the heat exchanger on / off valve 12 is opened and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is closed, the intermediate heat exchanger 7 is in a state of functioning as a cooler. Compared to the case where the heat exchanger 7 is not provided (in this case, the refrigeration cycle is performed in the order of point A ⁇ point B1 ⁇ point D ′ ⁇ point E ⁇ point F in FIGS.
- the switching mechanism 3 is in the heating operation state indicated by the broken lines in FIGS.
- the opening degree of the first expansion mechanism 5a and the second expansion mechanism 5b is adjusted. Since the switching mechanism 3 is in a heating operation state, the intermediate heat exchanger on / off valve 12 of the intermediate refrigerant pipe 8 is closed, and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is opened. As a result, the intermediate heat exchanger 7 does not function as a cooler. Further, since the switching mechanism 3 is in the heating operation state, the intermediate heat exchanger 7 and the suction side of the compression mechanism 2 are connected by opening the second suction return on / off valve 92a of the second suction return pipe 92. The intermediate heat exchanger return pipe 94 is opened, and the intermediate heat exchanger return opening / closing valve 94a is opened, whereby the intermediate heat exchanger is connected between the use side heat exchanger 6 and the heat source side heat exchanger 4. 7 is connected.
- low-pressure refrigerant (see point A in FIGS. 1 and 5 to 7) is sucked into the compression mechanism 2 from the suction pipe 2a and first compressed to an intermediate pressure by the compression element 2c. Thereafter, the refrigerant is discharged into the intermediate refrigerant pipe 8 (see point B1 in FIGS. 1 and 5 to 7). Unlike the cooling operation, the intermediate-pressure refrigerant discharged from the preceding-stage compression element 2c does not pass through the intermediate heat exchanger 7 (that is, is not cooled), and the intermediate heat exchanger bypass pipe. 9 (refer to point C1 in FIGS.
- 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. 6) by the two-stage compression operation by the compression elements 2c and 2d as in the cooling operation. ) Compressed to a pressure exceeding The high-pressure refrigerant discharged from the compression mechanism 2 flows into the oil separator 41a constituting the oil separation mechanism 41, and the accompanying refrigeration oil is separated.
- the refrigerating machine oil separated from the high-pressure refrigerant in the oil separator 41a flows into the oil return pipe 41b constituting the oil separation mechanism 41, and is compressed after being reduced in pressure by the pressure reduction mechanism 41c provided in the oil return pipe 41b. It is returned to the suction pipe 2a of the mechanism 2 and again sucked into the compression mechanism 2.
- the high-pressure refrigerant after the refrigerating machine oil is separated in the oil separation mechanism 41 is sent to the use side heat exchanger 6 functioning as a refrigerant radiator through the check mechanism 42 and the switching mechanism 3 to be cooled. It is cooled by exchanging heat with water or air as a source (see point F in FIGS. 1 and 5 to 7).
- the high-pressure refrigerant cooled in the use-side heat exchanger 6 flows into the receiver inlet pipe 18a through the inlet check valve 17b of the bridge circuit 17, and is reduced to near the saturation pressure by the first expansion mechanism 5a. (See point I in FIGS. 1 and 5). Then, the refrigerant stored in the receiver 18 is sent to the receiver outlet pipe 18b and is reduced in pressure by the second expansion mechanism 5b to become a low-pressure gas-liquid two-phase refrigerant, and the outlet check valve 17d of the bridge circuit 17 is supplied.
- the intermediate heat exchanger return pipe 94 and also to the intermediate heat exchanger 7 functioning as the refrigerant evaporator (FIG. 1, FIG. 1). 5 to point E in FIG. 7).
- the low-pressure gas-liquid two-phase refrigerant sent to the heat source side heat exchanger 4 is heated by exchanging heat with water or air as a heating source to evaporate (FIG. 1, FIG. 1). 5 to point A in FIG. 7). Further, the low-pressure gas-liquid two-phase refrigerant sent to the intermediate heat exchanger 7 is also heated by exchanging heat with water or air as a heating source (FIGS. 1 and 5). (See point V in FIG. 7).
- the low-pressure refrigerant heated and evaporated in the heat source side heat exchanger 4 is again sucked into the compression mechanism 2 via the switching mechanism 3.
- the low-pressure refrigerant heated and evaporated in the intermediate heat exchanger 7 is again sucked into the compression mechanism 2 through the second suction return pipe 92. In this way, the heating operation is performed.
- the intermediate heat exchanger on / off valve 12 in the heating operation in which the switching mechanism 3 is in the heating operation state, the intermediate heat exchanger on / off valve 12 is closed and the intermediate heat exchanger bypass on / off valve 11 is opened. Therefore, the intermediate heat exchanger 7 is not functioning as a cooler. Therefore, when only the intermediate heat exchanger 7 is provided or when the intermediate heat exchanger 7 is functioned as a cooler as in the above cooling operation. (In this case, the refrigeration cycle is performed in the order of point A ⁇ point B1 ⁇ point C1 ′ ⁇ point D ′ ⁇ point F ⁇ point E in FIGS. 6 and 7). The decrease in the temperature of the refrigerant to be performed is suppressed (see points D and D ′ in FIG. 7).
- this air conditioning apparatus 1 compared with the case where only the intermediate heat exchanger 7 is provided or the case where the intermediate heat exchanger 7 functions as a cooler as in the above-described cooling operation, the heat radiation to the outside is reduced. It is possible to suppress the temperature drop of the refrigerant supplied to the use-side heat exchanger 6 that functions as a refrigerant radiator, and the enthalpy difference between point D and point F in FIG. It is possible to prevent a decrease in operating efficiency by suppressing a decrease in heating capacity corresponding to the difference from the enthalpy difference from F.
- the intermediate heat exchanger 7 in the heating operation in which the switching mechanism 3 is in the heating operation state, is not simply used so that it does not function as a cooler. Together with the heat source side heat exchanger 4, the intermediate heat exchanger 7 is made to function as an evaporator for the refrigerant that has radiated heat in the use side heat exchanger 7, and is also used during heating operation.
- the heating capacity of the use-side heat exchanger 4 is reduced by increasing the evaporation capacity of the refrigerant during heating operation and increasing the flow rate of the refrigerant circulating in the refrigerant circuit 10 while suppressing heat radiation to the outside. I try to suppress it.
- the heat dissipation loss in the heat source side heat exchanger 4 that functions as a refrigerant radiator is reduced during the cooling operation, and the operation efficiency during the cooling operation can be improved.
- the intermediate heat exchanger 7 is effectively used, and the heating capacity in the use-side heat exchanger 4 is suppressed from being lowered so that the operation efficiency during the heating operation is not lowered. be able to.
- the refrigerant discharged from the compression element 2c on the front stage side through the intermediate heat exchanger bypass pipe 9 is brought into a state of being sucked into the compression element 2d on the rear stage side.
- the cooling start control for connecting the intermediate heat exchanger 7 and the suction side of the compression mechanism 2 is performed by the two suction return pipe 92.
- step S1 when a cooling operation start command is issued, the process proceeds to a process of operating various valves in step S2.
- step S2 the on-off state of the on-off valves 11, 12, 92a is set such that the refrigerant discharged from the front-stage compression element 2c through the intermediate heat exchanger bypass pipe 9 is sucked into the rear-stage compression element 2d, The state is switched to the refrigerant return state in which the intermediate heat exchanger 7 and the suction side of the compression mechanism 2 are connected through the second suction return pipe 92.
- the intermediate heat exchanger bypass opening / closing valve 11 is opened, and the intermediate heat exchanger opening / closing valve 12 is closed.
- the intermediate heat exchanger bypass pipe 9 causes a flow in which the refrigerant discharged from the front-stage compression element 2 c is sucked into the rear-stage compression element 2 d without passing through the intermediate heat exchanger 7. That is, the intermediate heat exchanger 7 is not functioned as a cooler, and the refrigerant discharged from the upstream compression element 2c through the intermediate heat exchanger bypass pipe 9 is sucked into the downstream compression element 2d. (See FIG. 9). In such a state, the second suction return on / off valve 92a is opened.
- the intermediate heat exchanger 7 and the suction side of the compression mechanism 2 are connected by the second suction return pipe 92, and the intermediate heat exchanger 7 (more specifically, the intermediate heat exchange including the intermediate heat exchanger 7 is performed).
- the pressure of the refrigerant in the portion between the heater on / off valve 12 and the check mechanism 15) is reduced to near the low pressure in the refrigeration cycle, and the refrigerant in the intermediate heat exchanger 7 can be drawn to the suction side of the compression mechanism 2 (See FIG. 9).
- step S3 the open / close state of the on-off valves 11, 12, 92a in step S2 (that is, the refrigerant return state) is maintained for a predetermined time.
- the liquid refrigerant accumulated in the intermediate heat exchanger 7 is evaporated under reduced pressure, Without being sucked into the compression element 2d on the side, it is pulled out of the intermediate heat exchanger 7 (more specifically, on the suction side of the compression mechanism 2), and the compression mechanism 2 (here, the compression element 2c on the front stage side) Will be inhaled.
- the predetermined time is set to a time during which the liquid refrigerant accumulated in the intermediate heat exchanger 7 can be extracted out of the intermediate heat exchanger 7.
- step S4 the open / close state of the on-off valves 11, 12, 92a is changed so that the refrigerant discharged from the front-stage compression element 2c through the intermediate heat exchanger 7 is sucked into the rear-stage compression element 2d and the second suction is performed. Switching to the refrigerant non-return state in which the intermediate heat exchanger 7 and the suction side of the compression mechanism 2 are not connected through the return pipe 92 is performed.
- the control is shifted to the open / closed state of the valves 11, 12, 92a during the cooling operation described above, and the cooling start control is terminated. Specifically, the second suction return on / off valve 92a is closed. Then, the refrigerant in the intermediate heat exchanger 7 does not flow out to the suction side of the compression mechanism 2. In such a state, the intermediate heat exchanger on / off valve 12 is opened, and the intermediate heat exchanger bypass on / off valve 11 is closed. If it does so, it will be in the state in which the intermediate heat exchanger 7 functions as a cooler.
- a refrigerant circuit provided with an intermediate heat exchanger switching valve 93 capable of switching between a refrigerant non-return state and a refrigerant return state. It may be 110.
- the intermediate heat exchanger switching valve 93 is a valve that can be switched between a refrigerant non-return state and a refrigerant return state.
- the intermediate heat exchanger switching valve 93 is connected to the discharge side of the compression element 2c on the upstream side of the intermediate refrigerant pipe 8.
- the intermediate refrigerant pipe 8 is connected to the inlet side of the intermediate heat exchanger 7, the intermediate heat exchanger bypass pipe 9 is connected to the front end side of the compression element 2 c, and the second suction return pipe 92 is connected to the intermediate heat exchanger 7 side end.
- This is a four-way switching valve.
- the intermediate heat exchanger bypass pipe 9 allows the refrigerant to flow from the discharge side of the front-stage compression element 2c to the suction side of the rear-stage compression element 2d, and sucks the rear-stage compression element 2d.
- the check mechanism 9a is a check valve in this modification.
- the refrigerant discharged from the compression element 2c on the upstream side through the intermediate heat exchanger 7 is supplied to the compression element 2d on the downstream side through the intermediate heat exchanger 7.
- the intermediate heat exchanger switching valve 93 can be used to switch between the refrigerant non-return state and the refrigerant return state. Therefore, the plurality of valves 11, 12, and 92 a as in the above-described embodiment allow The number of valves can be reduced compared to a case where a configuration for switching between the non-return state and the refrigerant return state is employed. Further, since the pressure loss is reduced as compared with the case where a solenoid valve is used, it is possible to suppress a decrease in the intermediate pressure in the refrigeration cycle and to suppress a decrease in operating efficiency.
- the intermediate heat exchanger 7 and the heat source side heat exchanger 4 are heat exchangers using air as a heat source (that is, a cooling source or a heating source), and both the heat exchangers 4 and 7 are used. It is conceivable to employ a configuration in which air as a heat source is supplied by a common heat source side fan 40 (described later).
- the air conditioner 1 includes a heat source unit 1a mainly provided with a heat source side fan 40, a heat source side heat exchanger 4 and an intermediate heat exchanger 7, and a use unit mainly provided with a use side heat exchanger 6 (FIG.
- a heat source unit 1a mainly provided with a heat source side fan 40, a heat source side heat exchanger 4 and an intermediate heat exchanger 7, and a use unit mainly provided with a use side heat exchanger 6
- FIG. 11 is an external perspective view of the heat source unit 1a (with the fan grill removed)
- FIG. 12 is a side view of the heat source unit 1a with the right plate of the heat source unit 1a removed.
- “left” and “right” are based on the case where the heat source unit 1a is viewed from the front plate 24 side.
- the heat source unit 1a constituting the air conditioner 1 of the present modification is a so-called top-blowing type that sucks air from the side and blows air upward. It has refrigerant circuit components such as the heat source side heat exchanger 4 and the intermediate heat exchanger 7 arranged inside, and devices such as the heat source side fan 40.
- the casing 71 is a substantially rectangular parallelepiped box, and mainly includes a top plate 72 constituting the top surface of the casing 71, a left plate 73, a right plate 74 constituting the outer peripheral surface of the casing 71, and the front.
- the plate 75 and the rear plate 76 and the bottom plate 77 are constituted.
- the top plate 72 is a member that mainly constitutes the top surface of the casing 71.
- the top plate 72 is a plate-like member having a substantially rectangular shape in a plan view in which the blowing opening 71a is formed at a substantially center.
- the top plate 72 is provided with a fan grill 78 so as to cover the blowout opening 71a from above.
- the left plate 73 is a member that mainly constitutes the left surface of the casing 71.
- the left plate 73 is a plate-like member that is substantially rectangular in a side view extending downward from the left edge of the top plate 72.
- the left plate 73 is formed with a suction opening 73a almost entirely except for the upper part.
- the right plate 74 is a member that mainly constitutes the right surface of the casing 71.
- the right plate 74 is a plate-like member that is substantially rectangular in a side view extending downward from the right edge of the top plate 72.
- the right plate 74 is formed with a suction opening 74a almost entirely except for the upper part.
- the front plate 75 is a member that mainly constitutes the front surface of the casing 71.
- the front plate 75 is formed of a plate-like member that is disposed in order downward from the front edge of the top plate 72 in a substantially rectangular shape.
- the rear plate 76 is a member that mainly constitutes the rear surface of the casing 71.
- the rear plate 76 is formed of a plate-like member that is disposed in order downward from the rear edge of the top plate 72 in a substantially rectangular shape.
- the rear plate 76 is formed with a suction opening 76a in substantially the whole except the upper part.
- the bottom plate 77 is a member that mainly constitutes the bottom surface of the casing 71.
- the bottom plate 77 is a plate-like member having a substantially rectangular shape in plan view.
- the intermediate heat exchanger 7 is integrated with the heat source side heat exchanger 4 while being disposed above the heat source side heat exchanger 4, and is disposed on the bottom plate 77. More specifically, the intermediate heat exchanger 7 is integrated with the heat source side heat exchanger 4 by sharing heat transfer fins. Further, in the present modification, the heat source side heat exchanger 4 and the intermediate heat exchanger 7 are integrated to form a heat exchanger panel having a substantially U shape in plan view, and the suction openings 73a and 74a. , 76a. Further, the heat source side fan 40 is opposed to the blowout opening 71a of the top plate 72, and above the one in which the heat source side heat exchanger 4 and the intermediate heat exchanger 7 are integrated (that is, the heat exchanger panel).
- the heat source side fan 40 is an axial fan, and is driven to rotate by the fan drive motor 40a so that air as a heat source is sucked into the casing 71 from the suction openings 73a, 74a, 76a, and the heat source side After passing through the heat exchanger 4 and the intermediate heat exchanger 7, the air can be blown upward from the blowout opening 71a (see the arrows indicating the air flow in FIG. 12). That is, the heat source side fan 40 supplies air as a heat source to both the heat source side heat exchanger 4 and the intermediate heat exchanger 7.
- the external shape of the heat source unit 1a and the shape of the heat source side heat exchanger 4 and the intermediate heat exchanger 7 integrated are not limited to those described above.
- the intermediate heat exchanger 7 constitutes a heat exchanger panel integrated with the heat source side heat exchanger 4, and is disposed on the upper part of the heat exchanger panel.
- the intermediate heat exchanger 7 is integrated with the heat source side heat exchanger 4, and the intermediate heat exchanger 7 is arranged on the upper part of the heat exchanger panel in which both are integrated.
- a refrigeration cycle such as a cooling operation in which a high-pressure refrigerant exceeding the critical pressure Pcp flows may be performed in the heat source side heat exchanger 4 functioning as a radiator (see FIG. 3).
- the heat transfer coefficient on the refrigerant side of the heat exchanger 7 tends to be lower than the heat transfer coefficient on the refrigerant side of the heat source side heat exchanger 4 that functions as a refrigerant radiator.
- FIG. 13 shows the value of the heat transfer coefficient in the case where 6.5 MPa carbon dioxide flows at a predetermined mass flow rate in a heat transfer channel having a predetermined channel cross-sectional area (intermediate cold heat exchanger 7 as a cooler).
- the heat transfer coefficient value of 10 MPa carbon dioxide under the same heat transfer flow path and mass flow rate condition as 6.5 MPa carbon dioxide (heat source side heat exchanger as a radiator) 4 corresponds to the heat transfer coefficient on the refrigerant side 4), and when viewed, the heat source side heat exchanger 4 that functions as a refrigerant radiator and the intermediate heat exchanger 7 that functions as a refrigerant cooler are shown.
- the value of the heat transfer coefficient of 6.5 MPa carbon dioxide is lower than the value of the heat transfer coefficient of carbon dioxide of 10 MPa in the temperature range of the refrigerant flowing through (about 35 to 70 ° C.).
- the intermediate heat exchanger 7 is temporarily When integrated with the heat source side heat exchanger 4 in a state of being arranged below the heat source side heat exchanger 4, it is integrated with the heat source side heat exchanger 4 at the lower part of the heat source unit 1a where the flow velocity of air serving as the heat source is small.
- the intermediate heat exchanger 7 will be arranged, the influence of the reduction in the heat transfer coefficient on the air side of the intermediate heat exchanger 7 due to the arrangement of the intermediate heat exchanger 7 below the heat source unit 1a, and the intermediate heat exchange This is because the heat transfer performance of the intermediate heat exchanger 7 is deteriorated by overlapping with the effect that the heat transfer coefficient on the refrigerant side of the heat exchanger 7 becomes lower than the heat transfer coefficient on the refrigerant side of the heat source side heat exchanger 4. .
- the intermediate heat exchanger bypass pipe 9 is used during heating operation, the refrigerant discharged from the front-stage compression element 2c and sucked into the rear-stage compression element 2d is intermediate.
- the intermediate air disposed at the position where the flow rate of air as the heat source is the highest in consideration of the heat transfer coefficient during the cooling operation. The heat exchanger 7 does not contribute at all during the heating operation, and the demerit of not effectively using the intermediate heat exchanger 7 is great.
- the intermediate heat exchanger bypass pipe 9 is used to discharge from the upstream compression element 2c to the downstream compression element 2d.
- the intermediate heat exchanger 7 functions as a refrigerant evaporator, thereby contributing to an increase in evaporation capacity during heating operation.
- the first rear-stage injection pipe 19 and the economizer heat exchanger 20 are used.
- the refrigerant circuit 210 can be provided.
- the first second-stage injection pipe 19 has a function of branching the refrigerant flowing between the heat source-side heat exchanger 4 and the use-side heat exchanger 6 and returning it to the compression element 2d on the rear stage side of the compression mechanism 2.
- the first second-stage injection pipe 19 is provided to branch the refrigerant flowing through the receiver inlet pipe 18a and return it to the suction side of the second-stage compression element 2d.
- the first second-stage injection pipe 19 is positioned on the upstream side of the first expansion mechanism 5a of the receiver inlet pipe 18a (that is, when the switching mechanism 3 is in the cooling operation state, the heat source side heat The refrigerant is branched from the exchanger 4 and the first expansion mechanism 5a) and returned to the downstream position of the intermediate heat exchanger 7 in the intermediate refrigerant pipe 8.
- the first second-stage injection pipe 19 is provided with a first second-stage injection valve 19a capable of opening degree control.
- the 1st latter stage side injection valve 19a is an electric expansion valve in this modification.
- the economizer heat exchanger 20 includes a refrigerant flowing between the heat source side heat exchanger 4 and the use side heat exchanger 6 and a refrigerant flowing through the first second-stage injection pipe 19 (more specifically, a first second-stage injection valve).
- 19a is a heat exchanger that performs heat exchange with the refrigerant after being reduced in pressure to near the intermediate pressure.
- the economizer heat exchanger 20 is positioned on the upstream side of the first expansion mechanism 5a of the receiver inlet pipe 18a (that is, when the switching mechanism 3 is in the cooling operation state, the heat source side heat exchanger 4 Between the refrigerant flowing between the refrigerant and the first expansion mechanism 5a) and the refrigerant flowing through the first second-stage injection pipe 19, and a flow path through which the two refrigerants face each other.
- the economizer heat exchanger 20 is provided on the downstream side of the position where the first second-stage injection pipe 19 is branched from the receiver inlet pipe 18a.
- the refrigerant flowing between the heat source side heat exchanger 4 and the use side heat exchanger 6 is transferred to the first second-stage injection pipe 19 before heat exchange is performed in the economizer heat exchanger 20 in the receiver inlet pipe 18a.
- the economizer heat exchanger 20 exchanges heat with the refrigerant flowing through the first second-stage injection pipe 19.
- the high-pressure refrigerant cooled in the heat source side heat exchanger 4 is converted into the inlet check valve 17a of the bridge circuit 17 and the economizer heat. It is sent to the use side heat exchanger 6 through the exchanger 20, the first expansion mechanism 5a of the receiver inlet pipe 18a, the receiver 18, the second expansion mechanism 5b of the receiver outlet pipe 18b, and the outlet check valve 17c of the bridge circuit 17. It can be done. Further, when the switching mechanism 3 is in the heating operation state, the high-pressure refrigerant cooled in the use side heat exchanger 6 is supplied to the inlet check valve 17b of the bridge circuit 17, the economizer heat exchanger 20, the receiver inlet pipe. It can be sent to the heat source side heat exchanger 4 through the first expansion mechanism 5a of 18a, the receiver 18, the second expansion mechanism 5b of the receiver outlet pipe 18b, and the outlet check valve 17d of the bridge circuit 17.
- the intermediate refrigerant pipe 8 or the compression mechanism 2 is provided with an intermediate pressure sensor 54 that detects the pressure of the refrigerant flowing through the intermediate refrigerant pipe 8.
- An economizer outlet temperature sensor 55 that detects the temperature of the refrigerant at the outlet of the economizer heat exchanger 20 on the first rear-stage injection pipe 19 side is provided at the outlet of the economizer heat exchanger 20 on the first rear-stage injection pipe 19 side.
- FIG. 18 is a pressure-enthalpy diagram illustrating the refrigeration cycle during the heating operation
- FIG. 18 is a temperature-entropy diagram illustrating the refrigeration cycle during the heating operation.
- cooling start control is the same as that in the above-described embodiment, the description thereof is omitted here.
- operation control in the following cooling operation and heating operation is performed by the control unit (not shown) in the above-described embodiment.
- “high pressure” means high pressure in the refrigeration cycle (that is, pressure at points D, D ′, E, and H in FIGS. 15 and 16, and points D, D ′, and FIGS. 17 and 18).
- Pressure at F, H and “low pressure” means low pressure in the refrigeration cycle (that is, pressure at points A and F in Figs. 15 and 16 and pressure at points A, E and V in Figs. 17 and 18).
- the “intermediate pressure” means an intermediate pressure in the refrigeration cycle (that is, pressure at points B1, C1, G, J, and K in FIGS. 15 to 18).
- the switching mechanism 3 is in the cooling operation state indicated by the solid line in FIG.
- the opening degree of the first expansion mechanism 5a and the second expansion mechanism 5b is adjusted.
- the opening degree of the first second-stage injection valve 19a is also adjusted. More specifically, in this modification, the first second-stage injection valve 19a has an opening degree so that the degree of superheat of the refrigerant at the outlet of the economizer heat exchanger 20 on the first second-stage injection pipe 19 side becomes a target value. So-called superheat control is performed.
- the superheat degree of the refrigerant at the outlet of the economizer heat exchanger 20 on the first second-stage injection pipe 19 side is obtained by converting the intermediate pressure detected by the intermediate pressure sensor 54 into the saturation temperature, and the economizer outlet temperature sensor 55. This is obtained by subtracting the saturation temperature value of the refrigerant from the refrigerant temperature detected by the above.
- a temperature sensor is provided at the inlet of the economizer heat exchanger 20 on the first second-stage injection pipe 19 side, and the refrigerant temperature detected by this temperature sensor is used as the economizer outlet temperature sensor 55.
- the degree of superheat of the refrigerant at the outlet of the economizer heat exchanger 20 on the first second-stage injection pipe 19 side may be obtained by subtracting from the refrigerant temperature detected by the above.
- the adjustment of the opening degree of the first second-stage injection valve 19a is not limited to the superheat degree control, and, for example, is to open a predetermined opening degree according to the refrigerant circulation amount in the refrigerant circuit 10 or the like. Also good. Since the switching mechanism 3 is in the cooling operation state, the intermediate heat exchanger on / off valve 12 of the intermediate refrigerant pipe 8 is opened, and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is closed.
- the intermediate heat exchanger 7 is brought into a state of functioning as a cooler, and the second suction return on / off valve 92a of the second suction return pipe 92 is closed, whereby the intermediate heat exchanger 7 and the compression mechanism 2 are closed.
- the suction side is not connected (except during the cooling start control), and the intermediate heat exchanger return on / off valve 94a of the intermediate heat exchanger return pipe 94 is closed, whereby the use side heat exchange is performed.
- the heat exchanger 6 and the heat source side heat exchanger 4 are not connected to the intermediate heat exchanger 7.
- the low-pressure refrigerant (see point A in FIGS. 14 to 16) is sucked into the compression mechanism 2 from the suction pipe 2a and first compressed to an intermediate pressure by the compression element 2c, It is discharged into the refrigerant pipe 8 (see point B1 in FIGS. 14 to 16).
- the intermediate-pressure refrigerant discharged from the preceding-stage compression element 2c is cooled by exchanging heat with water or air as a cooling source in the intermediate heat exchanger 7 (point C1 in FIGS. 14 to 16). reference).
- the refrigerant cooled in the intermediate heat exchanger 7 is further cooled by joining with the refrigerant (see point K in FIGS.
- 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.
- the high-pressure refrigerant after the refrigerating machine oil is separated in the oil separation mechanism 41 is sent to the heat source side heat exchanger 4 functioning as a refrigerant radiator through the check mechanism 42 and the switching mechanism 3. Then, the high-pressure refrigerant sent to the heat source side heat exchanger 4 is cooled by exchanging heat with water or air as a cooling source in the heat source side heat exchanger 4 (point E in FIGS. 14 to 16). reference).
- the high-pressure refrigerant cooled in the heat source side heat exchanger 4 flows into the receiver inlet pipe 18 a through the inlet check valve 17 a of the bridge circuit 17, and a part thereof is branched to the first second-stage injection pipe 19. .
- the refrigerant flowing through the first second-stage injection pipe 19 is reduced to near the intermediate pressure at the first second-stage injection valve 19a, and then sent to the economizer heat exchanger 20 (see point J in FIGS. 14 to 16). . Further, the refrigerant branched into the first second-stage injection pipe 19 flows into the economizer heat exchanger 20, and is cooled by exchanging heat with the refrigerant flowing through the first second-stage injection pipe 19 (FIG. 14 to FIG. 14). (See point H in FIG. 16). On the other hand, the refrigerant flowing through the first rear-stage injection pipe 19 is heated by exchanging heat with the high-pressure refrigerant cooled in the heat source-side heat exchanger 4 as a radiator (see point K in FIGS.
- the refrigerant is joined to the intermediate-pressure refrigerant discharged from the preceding compression element 2c. Then, the high-pressure refrigerant cooled in the economizer heat exchanger 20 is decompressed to the vicinity of the saturation pressure by the first expansion mechanism 5a and temporarily stored in the receiver 18 (see point I in FIG. 14). Then, the refrigerant stored in the receiver 18 is sent to the receiver outlet pipe 18b and is decompressed by the second expansion mechanism 5b to become a low-pressure gas-liquid two-phase refrigerant, and the outlet check valve 17c of the bridge circuit 17 is used.
- the use-side heat exchanger 6 that functions as a refrigerant evaporator (see point F in FIGS. 14 to 16). Then, the low-pressure gas-liquid two-phase refrigerant sent to the use side heat exchanger 6 is heated by exchanging heat with water or air as a heating source and evaporated (see FIGS. 14 to 14). 16 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.
- the intermediate heat exchanger 7 is made into the state which functions as a cooler in the air_conditionaing
- the heat radiation loss in the heat source side heat exchanger 4 can be reduced.
- the first rear-stage injection pipe 19 and the economizer heat exchanger 20 are provided to branch the refrigerant sent from the heat source-side heat exchanger 4 to the expansion mechanisms 5a and 5b, thereby compressing the rear-stage compression element.
- the temperature of the refrigerant sucked into the compression element 2d on the rear stage side can be further reduced without performing heat radiation to the outside like the intermediate heat exchanger 7 (FIG. 16). (See points C1 and G). Thereby, the temperature of the refrigerant discharged from the compression mechanism 2 is further suppressed (see points D and D ′ in FIG. 16), and compared with the case where the first second-stage injection pipe 19 is not provided, the point in FIG. Since the heat dissipation loss corresponding to the area surrounded by connecting C1, D ′, D, and G can be further reduced, the operating efficiency can be further improved.
- the refrigerant discharged from the compression element 2c on the front stage side through the intermediate heat exchanger bypass pipe 9 at the start of the cooling operation in which the switching mechanism 3 is in the cooling operation state Is sucked into the compression element 2d on the rear stage side, and the intermediate heat exchanger 7 and the suction side of the compression mechanism 2 are connected through the second suction return pipe 92, so that the switching mechanism 2 is brought into the cooling operation state. Even if liquid refrigerant has accumulated in the intermediate heat exchanger 7 before the start of operation, the liquid refrigerant can be extracted out of the intermediate heat exchanger 7, whereby the switching mechanism 3 is brought into the cooling operation state.
- the state in which the liquid refrigerant has accumulated in the intermediate heat exchanger 7 can be avoided, and the latter-stage compression element caused by the liquid refrigerant having accumulated in the intermediate heat exchanger 7 Hydraulic pressure at 2d It is no longer occurs, it is possible to improve the reliability of the compression mechanism 2.
- the switching mechanism 3 is in a heating operation state indicated by a broken line in FIG.
- the opening degree of the first expansion mechanism 5a and the second expansion mechanism 5b is adjusted. Further, the opening degree of the first second-stage injection valve 19a is adjusted in the same manner as in the above-described cooling operation. Since the switching mechanism 3 is in a heating operation state, the intermediate heat exchanger on / off valve 12 of the intermediate refrigerant pipe 8 is closed, and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is opened. As a result, the intermediate heat exchanger 7 does not function as a cooler.
- the switching mechanism 3 since the switching mechanism 3 is in the heating operation state, the state where the intermediate heat exchanger 7 and the suction side of the compression mechanism 2 are connected by opening the second suction return on / off valve 92a of the second suction return pipe 92.
- the intermediate heat exchanger return on / off valve 94a of the intermediate heat exchanger return pipe 94 between the use side heat exchanger 6 and the heat source side heat exchanger 4, the intermediate heat exchanger 7 and Is connected.
- the low-pressure refrigerant (see point A in FIGS. 14, 17, and 18) is sucked into the compression mechanism 2 from the suction pipe 2a and first compressed to an intermediate pressure by the compression element 2c. Later, it is discharged into the intermediate refrigerant pipe 8 (see point B1 in FIGS. 14, 17, and 18). Unlike the cooling operation, the intermediate-pressure refrigerant discharged from the preceding-stage compression element 2c does not pass through the intermediate heat exchanger 7 (that is, is not cooled), and the intermediate heat exchanger bypass pipe. 9 (see point C1 in FIGS.
- the refrigerant is returned from the first rear-stage injection pipe 19 to the rear-stage compression mechanism 2d (point K in FIGS. 14, 17, and 18). (Refer to point G in FIGS. 14, 17, and 18).
- the intermediate pressure refrigerant combined with the refrigerant returning from the first second-stage injection pipe 19 is sucked into the compression element 2d connected to the second-stage side of the compression element 2c and further compressed, and is discharged from the compression mechanism 2 to the discharge pipe. 2b (see point D in FIGS. 14, 17 and 18).
- 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.
- the high-pressure refrigerant after the refrigerating machine oil is separated in the oil separation mechanism 41 is sent to the use side heat exchanger 6 functioning as a refrigerant radiator through the check mechanism 42 and the switching mechanism 3 to be cooled. It cools by performing heat exchange with water or air as a source (see point F in FIGS. 14, 17, and 18). Then, the high-pressure refrigerant cooled in the use side heat exchanger 6 flows into the receiver inlet pipe 18a through the inlet check valve 17b of the bridge circuit 17, and a part thereof is branched to the first second-stage injection pipe 19. .
- the refrigerant flowing through the first rear-stage injection pipe 19 is heated by exchanging heat with the high-pressure refrigerant cooled in the heat source side heat exchanger 4 as a radiator (see FIGS. 14, 17, and 18).
- the refrigerant merges with the intermediate pressure refrigerant discharged from the preceding compression element 2c.
- the high-pressure refrigerant cooled in the economizer heat exchanger 20 is decompressed to the vicinity of the saturation pressure by the first expansion mechanism 5a and temporarily stored in the receiver 18 (see point I in FIG. 14).
- the refrigerant stored in the receiver 18 is sent to the receiver outlet pipe 18b and is reduced in pressure by the second expansion mechanism 5b to become a low-pressure gas-liquid two-phase refrigerant, and the outlet check valve 17d of the bridge circuit 17 is supplied.
- the intermediate heat exchanger return pipe 94 and also to the intermediate heat exchanger 7 functioning as the refrigerant evaporator (FIGS. 14 and FIG. 14). 17, see point E in FIG.
- the low-pressure gas-liquid two-phase refrigerant sent to the heat source side heat exchanger 4 is heated and exchanged with water or air as a heating source to evaporate (FIG. 14, FIG. 17, see point A in FIG.
- the low-pressure gas-liquid two-phase refrigerant sent to the intermediate heat exchanger 7 is also heated by exchanging heat with water or air as a heating source (FIGS. 14 and 17). , See point V in FIG. 18).
- the low-pressure refrigerant heated and evaporated in the heat source side heat exchanger 4 is again sucked into the compression mechanism 2 via the switching mechanism 3.
- the low-pressure refrigerant heated and evaporated in the intermediate heat exchanger 7 is again sucked into the compression mechanism 2 through the second suction return pipe 92. In this way, the heating operation is performed.
- the temperature of the refrigerant sucked into the second-stage compression element 2d is further reduced without performing heat radiation to the outside like the intermediate heat exchanger 7 because the second-stage compression element 2d is returned to the second-stage compression element 2d. (See points B1 and G in FIG. 18).
- the temperature of the refrigerant discharged from the compression mechanism 2 is further suppressed (see points D and D ′ in FIG. 18), and compared with the case where the first second-stage injection pipe 19 is not provided, the point in FIG. Since the heat dissipation loss corresponding to the area surrounded by connecting B1, D ′, D, and G can be reduced, the operating efficiency can be further improved.
- the heat radiation loss in the heat source side heat exchanger 4 that functions as a refrigerant radiator is reduced, and the operation efficiency during the cooling operation is improved.
- the intermediate heat exchanger 7 is effectively used, and the heating capacity in the use-side heat exchanger 4 is suppressed from being lowered, so that the operation efficiency during the heating operation is not lowered. It is possible to do so.
- the heat exchanger having a flow path that flows so that the refrigerant flowing through the rear-stage-side injection pipe 19 is opposed to the heat-source-side heat exchanger 4 or the utilization-side heat exchanger 6 in the economizer heat exchanger 20 is adopted.
- the temperature difference between the refrigerant sent to the expansion mechanisms 5a and 5b and the refrigerant flowing through the rear-stage injection pipe 19 can be reduced, and high heat exchange efficiency can be obtained.
- the configuration includes a plurality of usage-side heat exchangers 6 connected in parallel to each other, and each usage-side heat exchanger
- each usage-side heat exchanger In order to obtain the refrigeration load required in each use side heat exchanger 6 by controlling the flow rate of the refrigerant flowing through the receiver 6, the receiver 18 as a gas-liquid separator and the use side heat exchanger 6 can be obtained.
- the use side expansion mechanism 5c may be provided so as to correspond to each use side heat exchanger 6.
- the refrigerant circuit 210 see FIG.
- the first expansion mechanism 5a as the heat source side expansion mechanism after being cooled in the heat source side heat exchanger 4 as the radiator like the cooling operation in which the switching mechanism 3 is in the cooling operation state.
- the intermediate pressure by the economizer heat exchanger 20 is the same as in the third modification. Injection is advantageous.
- each use-side expansion mechanism 5c is used as a radiator so that the refrigeration load required in each use-side heat exchanger 6 as a radiator can be obtained.
- the flow rate of the refrigerant flowing through each usage-side heat exchanger 6 is controlled, and the flow rate of the refrigerant passing through each usage-side heat exchanger 6 as a radiator is the same as that of each usage-side heat exchanger 6 as a radiator.
- the opening degree control of each use side expansion mechanism 5c is performed.
- the degree of decompression of the refrigerant varies depending not only on the flow rate of the refrigerant flowing through each use side heat exchanger 6 as a radiator but also on the state of flow distribution among the use side heat exchangers 6 as a plurality of radiators.
- Multiple use-side swelling Since the degree of decompression may vary greatly between the mechanisms 5c, or the degree of decompression in the use-side expansion mechanism 5c may be relatively large, the refrigerant pressure at the inlet of the economizer heat exchanger 20 becomes low. In such a case, the amount of heat exchanged in the economizer heat exchanger 20 (i.e., the flow rate of the refrigerant flowing through the first second-stage injection pipe 19) may be reduced, making it difficult to use.
- 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.
- this connection pipe may be very long depending on the arrangement of the utilization unit and the heat source unit. Therefore, the influence of the pressure loss is also added, and the economizer heat exchanger 20 The refrigerant pressure at the inlet of the refrigerant will further decrease.
- the receiver 18 in order to allow the receiver 18 to function as a gas-liquid separator and perform intermediate pressure injection, the receiver 18 is provided with a second second-stage injection pipe 18c.
- the refrigerant circuit 310 is capable of performing intermediate pressure injection by the economizer heat exchanger 20 during cooling operation and performing intermediate pressure injection by the receiver 18 as a gas-liquid separator during heating operation.
- the second second-stage injection pipe 18c is a refrigerant pipe that can perform intermediate pressure injection by extracting the refrigerant from the receiver 18 and returning it to the second-stage compression element 2d of the compression mechanism 2.
- the second second-stage injection pipe 18c is provided with a second second-stage injection on-off valve 18d and a second second-stage injection check mechanism 18e.
- the second second-stage injection on / off valve 18d is a valve that can be opened and closed, and is an electromagnetic valve in this modification.
- the second second-stage injection check mechanism 18e allows the refrigerant flow from the receiver 18 to the second-stage compression element 2d and blocks the refrigerant flow from the second-stage compression element 2d to the receiver 18. This is a mechanism, and a check valve is used in this modification.
- the second rear injection pipe 18c and the first suction return pipe 18f are integrated with each other on the receiver 18 side. Further, the second rear-stage injection pipe 18c and the first rear-stage injection pipe 19 are integrally formed on the intermediate refrigerant pipe 8 side.
- the use side expansion mechanism 5c is an electric expansion valve.
- the first second-stage injection pipe 19 and the economizer heat exchanger 20 are used during the cooling operation, and the second second-stage injection pipe 18c is used during the heating operation. Therefore, since it is not necessary to make the flow direction of the refrigerant to the economizer heat exchanger 20 constant regardless of the cooling operation and the heating operation, the bridge circuit 17 is omitted and the configuration of the refrigerant circuit 310 is simplified.
- FIG. 20 is a pressure-enthalpy diagram illustrating the refrigeration cycle during the heating operation
- FIG. 21 is a temperature-entropy diagram illustrating the refrigeration cycle during the heating operation.
- operation control including cooling start control not described here
- heating operation is performed by the control unit (not shown) in the above-described embodiment.
- high pressure means high pressure in the refrigeration cycle (that is, pressure at points D, D ′, E, and H in FIGS. 15 and 16, and points D, D ′, and FIGS. 20 and 21).
- Pressure in F means "low pressure” means low pressure in the refrigeration cycle (that is, pressure at points A and F in FIGS. 15 and 16 and pressure at points A, E and V in FIGS. 20 and 21).
- intermediate pressure means an intermediate pressure in the refrigeration cycle (that is, points B1, C1, G, J, K in FIGS. 15 and 16 and points B1, C1, G, I, L, FIGS. 20 and 21). Pressure at M).
- the switching mechanism 3 is in the cooling operation state indicated by the solid line in FIG.
- the opening degree of the first expansion mechanism 5a and the use-side expansion mechanism 5c as the heat source side expansion mechanism is adjusted. Since the switching mechanism 3 is in the cooling operation state, the intermediate heat exchanger on / off valve 12 of the intermediate refrigerant pipe 8 is opened, and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is closed. Thus, the intermediate heat exchanger 7 is brought into a state of functioning as a cooler, and the second suction return on / off valve 92a of the second suction return pipe 92 is closed, whereby the intermediate heat exchanger 7 and the compression mechanism 2 are closed.
- the suction side is not connected (except during the cooling start control), and the intermediate heat exchanger return on / off valve 94a of the intermediate heat exchanger return pipe 94 is closed, whereby the use side heat exchange is performed.
- the heat exchanger 6 and the heat source side heat exchanger 4 are not connected to the intermediate heat exchanger 7.
- the switching mechanism 3 when the switching mechanism 3 is in the cooling operation state, it is heated in the economizer heat exchanger 20 through the first second-stage injection pipe 19 without performing intermediate pressure injection by the receiver 18 as a gas-liquid separator.
- the intermediate pressure injection by the economizer heat exchanger 20 for returning the refrigerant to the compression element 2d on the rear stage side is performed. More specifically, the second second-stage injection on / off valve 18d is closed, and the opening degree of the first second-stage injection valve 19a is adjusted in the same manner as in Modification 3 described above.
- a low-pressure refrigerant (see point A in FIGS. 19, 15, and 16) is sucked into the compression mechanism 2 from the suction pipe 2a and first compressed to an intermediate pressure by the compression element 2c. Later, it is discharged into the intermediate refrigerant pipe 8 (see point B1 in FIGS. 19, 15, and 16).
- the intermediate-pressure refrigerant discharged from the preceding-stage compression element 2c is cooled by exchanging heat with water or air as a cooling source in the intermediate heat exchanger 7 (FIGS. 19, 15, and 16). Point C1).
- the refrigerant cooled in the intermediate heat exchanger 7 joins with the refrigerant (see point K in FIGS.
- 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. 15) by the two-stage compression operation by the compression elements 2c and 2d.
- the high-pressure refrigerant discharged from the compression mechanism 2 is sent to the heat source side heat exchanger 4 functioning as a refrigerant radiator via the switching mechanism 3, and water, air, and heat as a cooling source. It replaces and it cools (refer the point E of Drawing 19, Drawing 15, and Drawing 16).
- a part of the high-pressure refrigerant cooled in the heat source side heat exchanger 4 as a radiator is branched to the first second-stage injection pipe 19.
- the refrigerant flowing through the first second-stage injection pipe 19 is heated by exchanging heat with the high-pressure refrigerant cooled in the heat source side heat exchanger 4 as a radiator (see FIGS. 19, 15, and 16).
- the refrigerant merges with the intermediate pressure refrigerant discharged from the preceding compression element 2c.
- the high-pressure refrigerant cooled in the economizer heat exchanger 20 is depressurized to near the saturation pressure by the first expansion mechanism 5a and temporarily stored in the receiver 18 (point I in FIGS. 19, 15, and 16). reference).
- the refrigerant stored in the receiver 18 is sent to the use-side expansion mechanism 5c, and is decompressed by the use-side expansion mechanism 5c to become a low-pressure gas-liquid two-phase refrigerant, which functions as a refrigerant evaporator. It is sent to the side heat exchanger 6 (see point F in FIGS. 19, 15 and 16). Then, the low-pressure gas-liquid two-phase refrigerant sent to the use side heat exchanger 6 as an evaporator is heated by exchanging heat with water or air as a heating source to evaporate ( (See point A in FIGS. 19, 15 and 16). Then, the low-pressure refrigerant heated and evaporated in the use side heat exchanger 6 as the evaporator is again sucked into the compression mechanism 2 via the switching mechanism 3. In this way, the cooling operation is performed.
- the switching mechanism 3 is in a heating operation state indicated by a broken line in FIG.
- the opening degree of the first expansion mechanism 5a and the use-side expansion mechanism 5c as the heat source side expansion mechanism is adjusted. Since the switching mechanism 3 is in a heating operation state, the intermediate heat exchanger on / off valve 12 of the intermediate refrigerant pipe 8 is closed, and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is opened. As a result, the intermediate heat exchanger 7 does not function as a cooler.
- the switching mechanism 3 since the switching mechanism 3 is in the heating operation state, the state where the intermediate heat exchanger 7 and the suction side of the compression mechanism 2 are connected by opening the second suction return on / off valve 92a of the second suction return pipe 92. In addition, by opening the intermediate heat exchanger return on / off valve 94a of the intermediate heat exchanger return pipe 94, between the use side heat exchanger 6 and the heat source side heat exchanger 4, the intermediate heat exchanger 7 and Is connected. Further, when the switching mechanism 3 is in the heating operation state, the intermediate pressure injection by the economizer heat exchanger 20 is not performed, and the refrigerant is supplied from the receiver 18 as the gas-liquid separator through the second rear-stage injection pipe 18c. Intermediate pressure injection is performed by the receiver 18 that returns to the compression element 2d on the rear stage side. More specifically, the second second-stage injection on / off valve 18d is opened, and the first second-stage injection valve 19a is fully closed.
- low-pressure refrigerant (see point A in FIGS. 19 to 21) is sucked into the compression mechanism 2 from the suction pipe 2a, and first compressed to an intermediate pressure by the compression element 2c, The refrigerant is discharged into the refrigerant pipe 8 (see point B1 in FIGS. 19 to 21).
- the intermediate-pressure refrigerant discharged from the preceding-stage compression element 2c does not pass through the intermediate heat exchanger 7 (that is, is not cooled), and the intermediate heat exchanger bypass pipe. 9 (see point C1 in FIGS. 19 to 21), and the refrigerant (see point M in FIGS.
- 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. 20) by the two-stage compression operation by the compression elements 2c and 2d as in the cooling operation. ) Compressed to a pressure exceeding
- the high-pressure refrigerant discharged from the compression mechanism 2 is sent to the use-side heat exchanger 6 that functions as a refrigerant radiator via the switching mechanism 3, and water, air, and heat as a cooling source. It is exchanged and cooled (see point F in FIGS. 19 to 21).
- the high-pressure refrigerant cooled in the use-side heat exchanger 6 as a radiator is decompressed to the vicinity of the intermediate pressure by the use-side expansion mechanism 5c, and is then temporarily stored in the receiver 18 and gas-liquid separation is performed. (See points I, L, M in FIGS. 19-21).
- the gas refrigerant separated from the gas and liquid in the receiver 18 is extracted from the upper part of the receiver 18 by the second second-stage injection pipe 18c, and has the intermediate pressure discharged from the first-stage compression element 2c as described above. It will join the refrigerant.
- the liquid refrigerant stored in the receiver 18 is decompressed by the first expansion mechanism 5a to become a low-pressure gas-liquid two-phase refrigerant, and is sent to the heat source side heat exchanger 4 functioning as an evaporator of the refrigerant.
- the refrigerant is also sent to the intermediate heat exchanger 7 functioning as a refrigerant evaporator through the intermediate heat exchanger return pipe 94 (see point E in FIGS. 19 to 21).
- the low-pressure gas-liquid two-phase refrigerant sent to the heat source side heat exchanger 4 is heated by exchanging heat with water or air as a heating source to evaporate (FIG. 19 to FIG. 19). (See point A on 21).
- the low-pressure gas-liquid two-phase refrigerant sent to the intermediate heat exchanger 7 is also heated by exchanging heat with water or air as a heating source (FIGS. 19 to 21). Point V).
- the low-pressure refrigerant heated and evaporated in the heat source side heat exchanger 4 is again sucked into the compression mechanism 2 via the switching mechanism 3.
- the low-pressure refrigerant heated and evaporated in the intermediate heat exchanger 7 is again sucked into the compression mechanism 2 through the second suction return pipe 92. In this way, the heating operation is performed.
- this modification differs from the modification 3 in the point that instead of the intermediate pressure injection by the economizer heat exchanger 20 during the heating operation, the intermediate pressure injection by the receiver 18 as a gas-liquid separator is performed. About the point, the effect similar to the modification 3 can be acquired. Further, in this modification, switching between the cooling operation and the cooling start control, that is, switching between the refrigerant non-return state and the refrigerant return state is performed according to the open / close state of the on-off valves 11, 12, 92a.
- an intermediate heat exchanger switching valve 93 that can switch between the refrigerant non-return state and the refrigerant return state may be provided in place of the on-off valves 11, 12, 92a as in the first modification. Furthermore, when adopting the configuration of the heat source unit 1a as in the second modification, a particularly advantageous effect can be obtained.
- each use-side expansion mechanism 5c that is decompressed to near the saturation pressure by the first expansion mechanism 5a and temporarily accumulated in the receiver 18 is used as each use-side expansion mechanism.
- the refrigerant sent from the receiver 18 to each use-side expansion mechanism 5c is in a gas-liquid two-phase state, there is a possibility that a drift may occur during distribution to each use-side expansion mechanism 5c. It is desirable to make the refrigerant sent from each to the use side expansion mechanism 5c as supercooled as possible.
- the supercooling heat exchanger 96 and the third suction return pipe are provided between the receiver 18 and the use side expansion mechanism 5c.
- the refrigerant circuit 410 is provided with 95.
- the supercooling heat exchanger 96 is a heat exchanger that cools the refrigerant sent from the receiver 18 to the use-side expansion mechanism 5c.
- the supercooling heat exchanger 96 branches a part of the refrigerant sent from the receiver 18 to the use-side expansion mechanism 5c during the cooling operation, so that the suction side (that is, as an evaporator) of the compression mechanism 2
- This is a heat exchanger that performs heat exchange with the refrigerant flowing through the third suction return pipe 95 that returns to the suction pipe 2a) between the use-side heat exchanger 6 and the compression mechanism 2, and flows so that both refrigerants face each other.
- a road a road.
- the third suction return pipe 95 branches the refrigerant sent from the heat source side heat exchanger 4 as a radiator to the utilization side expansion mechanism 5c and returns it to the suction side (that is, the suction pipe 2a) of the compression mechanism 2. It is a refrigerant pipe.
- the third suction return pipe 95 is provided with a third suction return valve 95a whose opening degree can be controlled.
- the refrigerant sent from the receiver 18 to the use side expansion mechanism 5c and the third suction return valve 95a are controlled. Heat exchange with the refrigerant flowing through the third suction return pipe 95 after the pressure is reduced to near low pressure in the three suction return valve 95a is performed.
- the third suction return valve 95a is an electric expansion valve in this modification.
- the suction pipe 2 a or the compression mechanism 2 is provided with a suction pressure sensor 60 that detects the pressure of the refrigerant flowing on the suction side of the compression mechanism 2.
- a supercooling heat exchanger outlet temperature sensor 59 that detects the temperature of the refrigerant at the outlet of the supercooling heat exchanger 96 on the third suction return pipe 95 side is provided at the outlet of the supercooling heat exchanger 96 on the third suction return pipe 95 side. Is provided.
- FIG. 23 is a pressure-enthalpy diagram illustrating the refrigeration cycle during the cooling operation
- FIG. 24 is a temperature-entropy diagram illustrating the refrigeration cycle during the cooling operation.
- operation control including cooling start control not described here
- heating operation is performed by the control unit (not shown) in the above-described embodiment.
- “high pressure” means high pressure in the refrigeration cycle (that is, pressure at points D, E, I, and R in FIGS. 23 and 24, and points D, D ′, and F in FIGS. 20 and 21).
- “Low pressure” means low pressure in the refrigeration cycle (that is, pressure at points A, F, F, S ', U in FIGS. 23 and 24, and points A, E,
- “Intermediate pressure” means an intermediate pressure in the refrigeration cycle (ie, points B1, C1, G, J, K in FIGS. 23 and 24 and points B1, C1, Pressure in G, I, L, and M).
- the switching mechanism 3 is in the cooling operation state indicated by the solid line in FIG.
- the opening degree of the first expansion mechanism 5a and the use-side expansion mechanism 5c as the heat source side expansion mechanism is adjusted. Since the switching mechanism 3 is in the cooling operation state, the intermediate heat exchanger on / off valve 12 of the intermediate refrigerant pipe 8 is opened, and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is closed. Thus, the intermediate heat exchanger 7 is brought into a state of functioning as a cooler, and the second suction return on / off valve 92a of the second suction return pipe 92 is closed, whereby the intermediate heat exchanger 7 and the compression mechanism 2 are closed.
- the suction side is not connected (except during the cooling start control), and the intermediate heat exchanger return on / off valve 94a of the intermediate heat exchanger return pipe 94 is closed, whereby the use side heat exchange is performed.
- the heat exchanger 6 and the heat source side heat exchanger 4 are not connected to the intermediate heat exchanger 7. Further, when the switching mechanism 3 is in the cooling operation state, it is heated in the economizer heat exchanger 20 through the first second-stage injection pipe 19 without performing intermediate pressure injection by the receiver 18 as a gas-liquid separator. The intermediate pressure injection by the economizer heat exchanger 20 for returning the refrigerant to the compression element 2d on the rear stage side is performed.
- the second second-stage injection on / off valve 18d is closed, and the opening degree of the first second-stage injection valve 19a is adjusted in the same manner as in Modification 3 described above.
- the degree of opening of the third suction return valve 95a is also adjusted because the supercooling heat exchanger 96 is used. More specifically, in this modification, the third suction return valve 95a adjusts the opening so that the degree of superheat of the refrigerant at the outlet of the supercooling heat exchanger 96 on the third suction return pipe 95 side becomes the target value. In other words, so-called superheat control is performed.
- the superheat degree of the refrigerant at the outlet of the supercooling heat exchanger 96 on the side of the third suction return pipe 95 is calculated by converting the low pressure detected by the suction pressure sensor 60 into a saturation temperature, and the supercooling heat exchange outlet temperature. This is obtained by subtracting the saturation temperature value of the refrigerant from the refrigerant temperature detected by the sensor 59.
- a temperature sensor is provided at the inlet of the third cooling return pipe 95 side of the supercooling heat exchanger 96, and the refrigerant temperature detected by this temperature sensor is used as the supercooling heat exchange outlet.
- the degree of superheat of the refrigerant at the outlet on the third suction return pipe 95 side of the supercooling heat exchanger 96 may be obtained. Further, the adjustment of the opening degree of the third suction return valve 95a is not limited to the superheat degree control. For example, the opening degree of the third suction return valve 95a may be opened by a predetermined opening degree according to the refrigerant circulation amount in the refrigerant circuit 410. Good.
- the low-pressure refrigerant (see point A in FIGS. 22 to 24) is sucked into the compression mechanism 2 from the suction pipe 2a and first compressed to an intermediate pressure by the compression element 2c,
- the refrigerant is discharged into the refrigerant pipe 8 (see point B1 in FIGS. 22 to 24).
- the intermediate-pressure refrigerant discharged from the preceding compression element 2c is cooled by exchanging heat with water or air as a cooling source in the intermediate heat exchanger 7 (point C1 in FIGS. 22 to 24). reference).
- the refrigerant cooled in the intermediate heat exchanger 7 is further cooled by joining with the refrigerant (see point K in FIGS.
- the intermediate-pressure refrigerant joined with the refrigerant returning from the first second-stage injection pipe 19 (that is, subjected to intermediate-pressure injection by the economizer heat exchanger 20) is compressed by being connected to the second-stage side of the compression element 2c. It is sucked into the element 2d, further compressed, and discharged from the compression mechanism 2 to the discharge pipe 2b (see point D in FIGS. 22 to 24).
- 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.
- the high-pressure refrigerant discharged from the compression mechanism 2 is sent to the heat source side heat exchanger 4 functioning as a refrigerant radiator via the switching mechanism 3, and water, air, and heat as a cooling source. It is exchanged and cooled (see point E in FIGS. 22 to 24).
- a part of the high-pressure refrigerant cooled in the heat source side heat exchanger 4 as a radiator is branched to the first second-stage injection pipe 19.
- the refrigerant flowing through the first second-stage injection pipe 19 is sent to the economizer heat exchanger 20 after being reduced to near the intermediate pressure at the first second-stage injection valve 19a (see point J in FIGS.
- the refrigerant branched into the first second-stage injection pipe 19 flows into the economizer heat exchanger 20, and is cooled by exchanging heat with the refrigerant flowing through the first second-stage injection pipe 19 (FIG. 20 to FIG. 20). (See point H in FIG. 22).
- the refrigerant flowing through the first second-stage injection pipe 19 is heated by exchanging heat with the high-pressure refrigerant cooled in the heat source side heat exchanger 4 as a radiator (see point K in FIGS. 22 to 24). ), As described above, the refrigerant is joined to the intermediate-pressure refrigerant discharged from the preceding compression element 2c.
- the high-pressure refrigerant cooled in the economizer heat exchanger 20 is decompressed to near the saturation pressure by the first expansion mechanism 5a and is temporarily stored in the receiver 18 (see point I in FIGS. 22 to 24).
- a part of the refrigerant stored in the receiver 18 is branched to the third suction return pipe 95.
- the refrigerant flowing through the third suction return pipe 95 is depressurized to near low pressure in the third suction return valve 95a, and then sent to the supercooling heat exchanger 96 (see point S in FIGS. 20 to 22).
- the refrigerant branched into the third suction return pipe 95 flows into the supercooling heat exchanger 96 and is further cooled by exchanging heat with the refrigerant flowing through the third suction return pipe 95 (FIG. 22 to FIG. 22). (See point R in FIG. 24).
- the refrigerant flowing through the third suction return pipe 95 is heated by exchanging heat with the high-pressure refrigerant cooled in the economizer heat exchanger 20 (see point U in FIGS. 22 to 24).
- the refrigerant flows through the suction side (here, the suction pipe 2a).
- the refrigerant cooled in the supercooling heat exchanger 96 is sent to the use-side expansion mechanism 5c and decompressed by the use-side expansion mechanism 5c to become a low-pressure gas-liquid two-phase refrigerant, which functions as a refrigerant evaporator.
- a low-pressure gas-liquid two-phase refrigerant which functions as a refrigerant evaporator.
- the use side heat exchanger 6 see point F in FIGS. 22 to 24.
- the low-pressure gas-liquid two-phase refrigerant sent to the use side heat exchanger 6 as an evaporator is heated by exchanging heat with water or air as a heating source to evaporate ( (See point A in FIGS. 22 to 24).
- the low-pressure refrigerant heated and evaporated in the use side heat exchanger 6 as the evaporator is again sucked into the compression mechanism 2 via the switching mechanism 3. In this way, the cooling operation is performed.
- the switching mechanism 3 is in a heating operation state indicated by a broken line in FIG.
- the opening degree of the first expansion mechanism 5a and the use-side expansion mechanism 5c as the heat source side expansion mechanism is adjusted. Since the switching mechanism 3 is in a heating operation state, the intermediate heat exchanger on / off valve 12 of the intermediate refrigerant pipe 8 is closed, and the intermediate heat exchanger bypass on / off valve 11 of the intermediate heat exchanger bypass pipe 9 is opened. As a result, the intermediate heat exchanger 7 does not function as a cooler.
- the switching mechanism 3 since the switching mechanism 3 is in the heating operation state, the state where the intermediate heat exchanger 7 and the suction side of the compression mechanism 2 are connected by opening the second suction return on / off valve 92a of the second suction return pipe 92. In addition, by opening the intermediate heat exchanger return on / off valve 94a of the intermediate heat exchanger return pipe 94, between the use side heat exchanger 6 and the heat source side heat exchanger 4, the intermediate heat exchanger 7 and Is connected. Further, when the switching mechanism 3 is in the heating operation state, the intermediate pressure injection by the economizer heat exchanger 20 is not performed, and the refrigerant is supplied from the receiver 18 as the gas-liquid separator through the second rear-stage injection pipe 18c.
- Intermediate pressure injection is performed by the receiver 18 that returns to the compression element 2d on the rear stage side. More specifically, the second second-stage injection on / off valve 18d is opened, and the first second-stage injection valve 19a is fully closed. Further, when the switching mechanism 3 is in the heating operation state, the supercooling heat exchanger 96 is not used, so that the third suction return valve 95a is also fully closed.
- the low-pressure refrigerant (see point A in FIGS. 22, 20, and 21) is sucked into the compression mechanism 2 from the suction pipe 2a and first compressed to an intermediate pressure by the compression element 2c. Later, it is discharged into the intermediate refrigerant pipe 8 (see point B1 in FIGS. 22, 20, and 21). Unlike the cooling operation, the intermediate-pressure refrigerant discharged from the preceding-stage compression element 2c does not pass through the intermediate heat exchanger 7 (that is, is not cooled), and the intermediate heat exchanger bypass pipe. 9 (see point C1 in FIGS.
- the refrigerant is returned from the receiver 18 to the second-stage compression mechanism 2d through the second second-stage injection pipe 18c (FIGS. 22, 20, and 21). (See point M in FIG. 22) and cooling (see point G in FIGS. 22, 20, and 21).
- the intermediate-pressure refrigerant that has joined the refrigerant returning from the second 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 side of the compression element 2c. It is sucked into the compressed element 2d, further compressed, and discharged from the compression mechanism 2 to the discharge pipe 2b (see point D in FIGS. 22, 20, and 21).
- 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. 20) by the two-stage compression operation by the compression elements 2c and 2d as in the cooling operation. ) Compressed to a pressure exceeding
- the high-pressure refrigerant discharged from the compression mechanism 2 is sent to the use-side heat exchanger 6 that functions as a refrigerant radiator via the switching mechanism 3, and water, air, and heat as a cooling source. It replaces and it cools (refer point F of Drawing 22, Drawing 20, and Drawing 21).
- the high-pressure refrigerant cooled in the use-side heat exchanger 6 as a radiator is decompressed to the vicinity of the intermediate pressure by the use-side expansion mechanism 5c, and is then temporarily stored in the receiver 18 and gas-liquid separation is performed. (See points I, L, and M in FIGS. 22, 20, and 21).
- the gas refrigerant separated from the gas and liquid in the receiver 18 is extracted from the upper part of the receiver 18 by the second second-stage injection pipe 18c, and has the intermediate pressure discharged from the first-stage compression element 2c as described above. It will join the refrigerant.
- the liquid refrigerant stored in the receiver 18 is decompressed by the first expansion mechanism 5a to become a low-pressure gas-liquid two-phase refrigerant, and is sent to the heat source side heat exchanger 4 functioning as an evaporator of the refrigerant. Then, it is also sent to the intermediate heat exchanger 7 functioning as a refrigerant evaporator through the intermediate heat exchanger return pipe 94 (see point E in FIGS. 22, 20, and 21). Then, the low-pressure gas-liquid two-phase refrigerant sent to the heat source side heat exchanger 4 is heated by exchanging heat with water or air as a heating source to evaporate (FIG. 22, FIG. 20, see point A in FIG.
- the low-pressure gas-liquid two-phase refrigerant sent to the intermediate heat exchanger 7 is also heated by exchanging heat with water or air as a heating source (FIGS. 22 and 20). , See point V in FIG. 21).
- the low-pressure refrigerant heated and evaporated in the heat source side heat exchanger 4 is again sucked into the compression mechanism 2 via the switching mechanism 3.
- the low-pressure refrigerant heated and evaporated in the intermediate heat exchanger 7 is again sucked into the compression mechanism 2 through the second suction return pipe 92. In this way, the heating operation is performed.
- 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.
- 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.
- the refrigerant circuit 510 may employ a compression mechanism 102 connected to the refrigerant circuit.
- 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.
- the second compression mechanism 104 includes the compressor 30 that compresses the refrigerant in two stages with the two compression elements 104c and 104d, and the second suction mechanism branched from the suction mother pipe 102a of the compression mechanism 102.
- the branch pipe 104a and the second discharge branch pipe 104b joined to the discharge mother pipe 102b of the compression mechanism 102 are connected. Since the compressors 29 and 30 have the same configuration as that of the compressor 21 in the above-described embodiment and its modifications, the reference numerals indicating the parts other than the compression elements 103c, 103d, 104c, and 104d are the 29th and 30th, respectively. The description will be omitted here, with a replacement for the base.
- the compressor 29 sucks the refrigerant from the first suction branch pipe 103a, and after discharging the sucked refrigerant by the compression element 103c, discharges the refrigerant to the first inlet side intermediate branch pipe 81 constituting the intermediate refrigerant pipe 8.
- the refrigerant discharged to the first inlet-side intermediate branch pipe 81 is sucked into the compression element 103d through the intermediate mother pipe 82 and the first outlet-side intermediate branch pipe 83 constituting the intermediate refrigerant pipe 8, and the refrigerant is further compressed. It is configured to discharge to one discharge branch pipe 103b.
- the compressor 30 sucks the refrigerant from the 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.
- the intermediate refrigerant pipe 8 is configured so that the refrigerant discharged from the compression elements 103c and 104c connected to the upstream side of the compression elements 103d and 104d is compressed by the compression element 103d connected to the downstream side of the compression elements 103c and 104c.
- 104 d is a refrigerant pipe for inhalation, and mainly a first inlet side intermediate branch pipe 81 connected to the discharge side of the compression element 103 c on the front stage side of the first compression mechanism 103, and a front stage of the second compression mechanism 104.
- a second inlet side intermediate branch pipe 84 connected to the discharge side of the compression element 104c on the side, an intermediate mother pipe 82 where both the inlet side intermediate branch pipes 81 and 84 merge, and a first branch branched from the intermediate mother pipe 82.
- a first outlet side intermediate branch pipe 83 connected to the suction side of the compression element 103d on the rear stage side of the compression mechanism 103, and a suction element of the compression element 104d on the rear stage side of the second compression mechanism 104 branched from the intermediate mother pipe 82.
- 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.
- the first oil separation mechanism 141 is a mechanism that separates the refrigeration oil accompanying the refrigerant discharged from the first compression mechanism 103 from the refrigerant and returns it to the suction side of the compression mechanism 102, and is mainly discharged from the first compression mechanism 103.
- the first oil separator 141a that separates the refrigeration oil accompanying the refrigerant to be cooled from the refrigerant, and the first oil separator that is connected to the first oil separator 141a and returns the refrigeration oil separated from the refrigerant to the suction side of the compression mechanism 102 And an oil return pipe 141b.
- the second oil separation mechanism 143 is a mechanism that separates the refrigeration oil accompanying the refrigerant discharged from the second compression mechanism 104 from the refrigerant and returns it to the suction side of the compression mechanism 102, and is mainly discharged from the second compression mechanism 104.
- a second oil separator 143a that separates the refrigeration oil accompanying the refrigerant from the refrigerant, and a second oil separator that is connected to the second oil separator 143a and returns the refrigeration oil separated from the refrigerant to the suction side of the compression mechanism 102.
- an oil return pipe 143b In this modification, the first oil return pipe 141b is connected to the second suction branch pipe 104a, and the second oil return pipe 143c is connected to the first suction branch pipe 103a. For this reason, the refrigerant discharged from the first compression mechanism 103 is caused by a deviation between the amount of the refrigerating machine oil accumulated in the first compression mechanism 103 and the amount of the refrigerating machine oil accumulated in the second compression mechanism 104.
- the amount of refrigerating machine oil in the compression mechanisms 103 and 104 is A large amount of refrigeration oil returns to the smaller one, so that the bias between the amount of refrigeration oil accumulated in the first compression mechanism 103 and the amount of refrigeration oil accumulated in the second compression mechanism 104 is eliminated. It has become. Further, in this modification, the first suction branch pipe 103a has a portion between the junction with the second oil return pipe 143b and the junction with the suction mother pipe 102a at the junction with the suction mother pipe 102a.
- the second suction branch pipe 104a is configured such that the portion between the junction with the first oil return pipe 141b and the junction with the suction mother pipe 102a is the suction mother pipe. It is comprised so that it may become a downward slope toward the confluence
- 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.
- 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.
- 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.
- the intermediate heat exchanger 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 are provided. It is a heat exchanger that cools the refrigerant combined with the refrigerant discharged from the compression element 104c on the front stage side of the mechanism 104. That is, the intermediate heat exchanger 7 functions as a common cooler for the two compression mechanisms 103 and 104.
- 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,
- 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.
- 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.
- 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.
- 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.
- 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.
- the first compression mechanism 103 is a compression mechanism that operates preferentially
- 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.
- 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.
- 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.
- 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.
- an electromagnetic valve is used as the on-off valve 85a.
- 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.
- 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.
- 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.
- the on-off valve 85a 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.
- 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.
- the first compression mechanism 103 can be hardly affected by the intermediate pressure portion.
- an electromagnetic valve is used as the on-off valve 86a.
- the compression type compression mechanism 102 is configured, the refrigerant discharged from the front-stage compression element is sequentially compressed by the rear-stage compression element by connecting the compressors 22 and 23 having a single-stage compression structure in series.
- a two-stage compression type compression mechanism may be configured.
- the compression mechanism 2 instead of the compression mechanism 2 including the compressor 21 having the uniaxial two-stage compression structure, the compression of the single-stage compression structure is performed.
- a refrigerant circuit 610 employing a compression mechanism 202 in which the machines 22 and 23 are connected in series may be used.
- the compression mechanism 202 includes a compressor 22 that compresses the refrigerant with the compression element 2c as the first-stage compression element, and a compressor 22 that compresses the refrigerant with the compression element 2d as the second-stage compression element. It is configured.
- the compressor 22 has a sealed structure in which a compressor drive motor 22b, a drive shaft 22c, and a compression element 2c are accommodated in a casing 22a.
- the compressor drive motor 22b is connected to the drive shaft 22c.
- the compressor 23 has a sealed structure in which a compressor drive motor 23b, a drive shaft 23c, and a compression element 2d are accommodated in a casing 23a.
- the compressor drive motor 23b is connected to the drive shaft 23c.
- the compression elements 2c and 2d are displacement type compression elements such as a rotary type and a scroll type in this modification.
- the compression mechanism 202 sucks the refrigerant from the suction pipe 2 a, compresses the sucked refrigerant by the compression element 2 c of the compressor 22, discharges the refrigerant to the intermediate refrigerant pipe 8, and refrigerant discharged to the intermediate refrigerant pipe 8. Is sucked into the compression element 2d of the compressor 23 to further compress the refrigerant and then discharged to the discharge pipe 2b.
- the operations of the air conditioner 1 of the present modification are the same as those of the above-described modification 1 except that the compression mechanism 2 is replaced with the compression mechanism 202 (FIGS. 10 and 10). 1 to FIG. 9 and the related description), the description is omitted here. Also in the configuration of the present modification, it is possible to obtain the same functions and effects as those of the first modification described above. (10) Modification 8
- the intermediate heat exchanger return pipe 94 is provided with the intermediate heat exchanger return on / off valve 94a made of an electromagnetic valve, and is closed when the switching mechanism 3 is in the cooling operation state.
- the switching mechanism 3 is controlled to be opened when it is in a heating operation state, but instead of the intermediate heat exchanger return on / off valve 94a, an intermediate heat exchange functioning as a refrigerant evaporator during heating operation is performed.
- a flow rate adjusting valve may be provided so that the flow rate of the refrigerant flowing through the vessel 7 can be controlled.
- an intermediate heat exchanger return valve 94b as a flow rate adjustment valve.
- the refrigerant circuit 710 may be provided.
- an electric expansion valve capable of adjusting the opening is used as the intermediate heat exchanger return valve 94b.
- the first expansion mechanism 5a provided in the receiver inlet pipe 18a is connected to the refrigerant pipe 18h (more specifically, connecting the heat source side heat exchanger 4 and the bridge circuit 17).
- the differential pressure before and after the intermediate heat exchanger return valve 94b is provided by providing the refrigerant pipe 18h at a portion between the branch position of the intermediate heat exchanger return pipe 94 and the heat source side heat exchanger 4).
- the second expansion mechanism 5b provided in the receiver outlet pipe 18b is provided in the refrigerant pipe 18i connecting the bridge circuit 17 and the use side heat exchanger 6, so that the refrigerant in the receiver 18 can be obtained. Is set to an intermediate pressure in the refrigeration cycle.
- the refrigerant flows through the refrigerant circuit 710 in the order of the first expansion mechanism 5a, the receiver 18, and the second expansion mechanism 5b via the bridge circuit 17 during the cooling operation, and the bridge circuit during the heating operation.
- the point that the refrigerant flows through the refrigerant circuit 710 in the order of the second expansion mechanism 5b, the receiver 18, and the first expansion mechanism 5a via 17 is different from the above-described modified example 7 (in modified example 7, in the cooling operation and heating)
- the refrigerant flows through the refrigerant circuit 610 in the order of the first expansion mechanism 5a, the receiver, and the second expansion mechanism 5b).
- the intermediate heat exchanger return pipe 94 is provided with the intermediate heat exchanger return valve 94b as a flow rate adjustment valve, so that the refrigerant is supplied to the intermediate heat exchanger return pipe 94 during the cooling operation.
- the intermediate heat exchanger return valve 94b as a flow rate adjustment valve
- Modification 9 In the configuration of the above-described embodiment and its modified example, the refrigerant flowing between the heat source side heat exchanger 4 and the usage side heat exchanger 6 is interposed between the heat source side heat exchanger 4 and the usage side heat exchanger 6.
- An expansion device that expands entropically may be provided.
- the refrigerant circuit 710 in the above-described modified example 8, the refrigerant circuit 810 is provided with an expansion device 97 that expands the refrigerant isentropically in the receiver inlet pipe 18a. Also good.
- the expansion device 97 moves from the heat source side heat exchanger 4 toward the use side heat exchanger 6 and from the use side heat exchanger 6 toward the heat source side heat exchanger 4.
- a bridge circuit 17 as a rectifying circuit that rectifies the refrigerant so as to flow from the inlet of the expansion device 97.
- a centrifugal or positive displacement expander is used as the expansion device 97.
- the bridge circuit 17 is employed as the rectifier circuit.
- the same function may be achieved by combining a four-way switching valve or a plurality of electromagnetic valves.
- the refrigerant flows through the refrigerant circuit 810 in the order of the first expansion mechanism 5a, the expansion device 97, the receiver 18, and the second expansion mechanism 5b via the bridge circuit 17 serving as a rectifier circuit during the cooling operation.
- the refrigerant flows through the refrigerant circuit 810 in the order of the second expansion mechanism 5b, the receiver 18, and the first expansion mechanism 5a via the bridge circuit 17 serving as a rectifier circuit during the heating operation, so that the cooling operation and the heating operation can be performed.
- the expansion device 97 depressurizes the isentropic refrigerant (that is, in the cooling operation, FIGS. 3 and 4 are taken as an example).
- the refrigerant is depressurized while the point F moves toward the low enthalpy side and the low entropy side.
- the refrigerant is depressurized while moving to the low enthalpy side and the low entropy side), so that the coefficient of performance can be increased and the energy can be recovered, thereby further improving the operating efficiency during cooling and heating operations. Can do.
- control is performed to increase the opening of the second expansion mechanism 5b downstream of the expansion device 97, control to open the first suction return valve 18g, or the like.
- the decompression width in the expansion device 97 is increased by performing control to increase the opening degree of the first expansion mechanism 5a downstream of the expansion device 97 or control to open the first suction return valve 18g. You may make it aim at the improvement of driving efficiency to the maximum.
- the receiver 18 positioned at the outlet of the expansion device 97 functions as a gas-liquid separator, and the gas-liquid separated gas-liquid separated in the receiver 18 is returned to the subsequent compression element 2d.
- intermediate pressure injection by the receiver 18 as a gas-liquid separator may be performed during the cooling operation and the heating operation.
- the second post-stage injection pipe 18c is connected to the receiver 18 so as to serve as a gas-liquid separator.
- a refrigerant circuit 910 capable of performing intermediate pressure injection by 18 may be used.
- the second second-stage injection pipe 18c is a refrigerant pipe that can perform intermediate pressure injection by extracting the refrigerant from the receiver 18 and returning it to the second-stage compression element 2d of the compression mechanism 202.
- 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 202).
- the second second-stage injection pipe 18c is provided with a second second-stage injection on-off valve 18d and a second second-stage injection check mechanism 18e.
- the second second-stage injection on / off valve 18d is a valve that can be opened and closed, and is a solenoid valve in this modification.
- the second second-stage injection check mechanism 18e allows the refrigerant flow from the receiver 18 to the second-stage compression element 2d and blocks the refrigerant flow from the second-stage compression element 2d to the receiver 18. This is a mechanism, and a check valve is used in this modification.
- the second rear-stage injection pipe 18c and the first suction return pipe 18f are integrated with each other on the receiver 18 side.
- the receiver 18 connected to the outlet of the expansion device 9 functions as a gas-liquid separator in both the cooling operation and the heating operation, and the gas-liquid separation is performed in the receiver 18.
- the intermediate pressure injection is performed to return the gas refrigerant through the second second-stage injection pipe 18c to the second-stage compression element 2d (that is, from FIG. 20 to FIG.
- the temperature of the intermediate-pressure refrigerant in the refrigeration cycle sucked into the downstream compression element 2d can be lowered, and the operating efficiency can be further improved.
- Modification 11 In the above-described modified examples 7 to 10, a configuration having a plurality of usage-side heat exchangers 6 connected in parallel to each other is performed for the purpose of cooling or heating according to the air-conditioning load of the plurality of conditioned spaces. It may be.
- the refrigerant circuits 810 and 910 in the refrigerant circuits 810 and 910 (see FIGS. 28 and 29) in the above-described modified examples 9 and 10, a plurality (here, two) connected in parallel to each other.
- the refrigerant circuits 1010 and 1110 having the use side heat exchanger 6 may be used.
- a supercooler may be provided for the purpose of cooling the refrigerant sent to the use side heat exchanger 6 and the heat source side heat exchanger 4 so as to be in a supercooled state.
- a supercooling heat exchanger 96 is provided in the receiver outlet pipe 18b, and the receiver inlet pipe 18a is routed through the receiver 18.
- the refrigerant circuit 1210 may be provided with the third suction return pipe 95 provided up to the receiver outlet pipe 18b (here, the receiver 18).
- the supercooling heat exchanger 96 is supplied from the receiver 18 to each usage-side heat exchanger 6 via a plurality of (here, two) usage-side expansion mechanisms 5c during the cooling operation, and from the receiver 18 during the heating operation.
- the heat exchanger cools the refrigerant sent to the heat source side heat exchanger 4 and the intermediate heat exchanger 7 via the mechanism 5a and the intermediate heat exchanger return valve 94b. More specifically, the supercooling heat exchanger 96 performs heat exchange with the refrigerant flowing through the third suction return pipe 95 that returns from the receiver 18 to the suction side (that is, the suction pipe 2a) of the compression mechanism 2. It is.
- the third suction return pipe 95 is provided with a third suction return valve 95a whose opening degree can be controlled, and is sent from the receiver 18 to the use-side expansion mechanism 5c during the cooling operation in the supercooling heat exchanger 96. Heat exchange is performed between the refrigerant and the refrigerant flowing through the third suction return pipe 95 after being reduced to near low pressure in the third suction return valve 95a, and from the receiver 18 to the first expansion mechanism 5a and the intermediate heat exchanger return valve 94b. Heat exchange is performed between the refrigerant to be sent and the refrigerant flowing through the third suction return pipe 95 after being reduced to near low pressure in the third suction return valve 95a.
- the third suction return valve 95a is an electric expansion valve in this modification.
- the third suction return pipe 95 and the first suction return pipe 18f are integrated with each other on the receiver 18 side.
- the refrigerant sent from the receiver 18 to each usage-side expansion mechanism 5c during the cooling operation, and the first expansion mechanism 5a and the intermediate heat from the receiver 18 during the heating operation Since the refrigerant sent to the exchanger return valve 94b can be brought into a supercooled state (that is, the process from the point I to the point R is performed in FIGS. 23 and 24), the cooling is thereby performed.
- the compressors 25 and 26 having a single-stage compression structure similar to the compressors 22 and 23 constituting the compression mechanism 202 27 is connected to the intermediate refrigerant pipe 8 connecting the discharge of the first-stage compressor 25 and the suction of the second-stage compressor 26 as described above.
- An intermediate heat exchanger 7, an intermediate heat exchanger bypass pipe 9, a second suction return pipe 92, an intermediate heat exchanger switching valve 93, and an intermediate heat exchanger return valve 94 which are the same as those of the embodiment and the modified example,
- Heat exchanger switching valve 93 and intermediate heat exchanger return valve 9 Similar intermediate heat exchanger 307 and the intermediate heat exchanger bypass tube 309, the second intake return tube 392, the intermediate heat exchanger switching valve 393, and may be provided an intermediate heat exchanger return valve 394.
- the intermediate heat exchanger switching valves 93 and 393 are switched to the refrigerant non-return state, so that The heat exchangers 7 and 307 are supplied with an intermediate-pressure refrigerant in the refrigeration cycle (a refrigerant sent to the subsequent compression element 302d after being discharged from the previous compression element 302c, and a refrigerant discharged from the previous compression element 303c).
- the intermediate heat exchangers 7 and 307 are made to function as a cooler of the refrigerant that is later sent to the compression element 302e on the subsequent stage, and the intermediate heat exchanger switching valves 93 and 393 are switched to the refrigerant return state during the heating operation.
- Low-pressure refrigerant in the refrigeration cycle (although it differs from the above-described modification 11 etc. in that it functions as an evaporator of the refrigerant that dissipated heat in the use-side heat exchanger 6) Except the points, it is possible to obtain effects similar to such modification 11 described above.
- 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.
- the refrigerant operating in the supercritical region is not limited to carbon dioxide, and ethylene, ethane, nitrogen oxide, or the like may be used.
- a high operating efficiency can be obtained in a refrigeration apparatus having a refrigerant circuit configured to be capable of switching between a cooling operation and a heating operation and performing a multistage compression refrigeration cycle.
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Abstract
Description
この問題に対して、この冷凍装置のように、仮に、前段側の圧縮要素から吐出されて後段側の圧縮要素に吸入される冷媒の冷却器として機能する中間熱交換器を設けた場合には、後段側の圧縮要素に吸入される冷媒の温度が低くなるため、中間熱交換器を設けない場合に比べて、最終的に圧縮機構から吐出される冷媒の温度を低く抑えることができる。これにより、冷却運転時において、冷媒の放熱器として機能する熱源側熱交換器における放熱ロスが小さくなるため、冷却運転時の運転効率を向上させることができる。
これに対して、例えば、中間熱交換器をバイパスする中間熱交換器バイパス管を設けるとともに、加熱運転時には、この中間熱交換器バイパス管を用いて、前段側の圧縮要素から吐出されて後段側の圧縮要素に吸入される冷媒が中間熱交換器において冷却されないようにバイパスすることにより、中間熱交換器を使用しない状態にすることで、加熱運転時において、利用側熱交換器における加熱能力が低くなるのを抑えて、加熱運転時の運転効率が低下しないようにすることができる。
そこで、この冷凍装置では、切換機構を冷却運転状態にしている際に中間熱交換器を冷却器として機能させ、切換機構を加熱運転状態にしている際に、利用側熱交換器において放熱した冷媒の蒸発器として機能させるようにしている。このため、この冷凍装置では、冷却運転時においては、圧縮機構から吐出される冷媒の温度を低く抑えることができ、加熱運転時においては、冷媒の蒸発能力を高めることができるとともに、中間熱交換器から外部への放熱を抑えることができる。
これにより、この冷凍装置では、冷却運転時においては、冷媒の放熱器として機能する熱源側熱交換器における放熱ロスが小さくなり、冷却運転時の運転効率を向上させることができ、加熱運転時においては、中間熱交換器の有効利用が図られるとともに、利用側熱交換器における加熱能力が低くなるのを抑えて、加熱運転時の運転効率が低下しないようにすることができる。
この冷凍装置では、冷却運転時には、中間冷媒管を流れる中間圧の冷媒を中間熱交換器によって冷却することができ、加熱運転時には、中間冷媒管を流れる中間圧の冷媒を中間熱交換器バイパス管によって、中間熱交換器をバイパスさせるとともに、吸入戻し管及び中間熱交換器戻し管によって、利用側熱交換器において冷却された冷媒の一部を中間熱交換器に導いて蒸発させ、圧縮機構の吸入側に戻すことができる。
この冷凍装置では、切換機構を冷却運転状態にした運転の開始時に、中間熱交換器バイパス管を通じて前段側の圧縮要素から吐出された冷媒を後段側の圧縮要素に吸入させるとともに、吸入戻し管を通じて中間熱交換器と圧縮機構の吸入側とを接続させるようにしているため、切換機構を冷却運転状態にした運転の開始前に、中間熱交換器内に液冷媒が溜まり込んでいたとしても、この液冷媒を中間熱交換器外に抜くことができる。これにより、切換機構を冷却運転状態にした運転の開始時に、中間熱交換器内に液冷媒が溜まり込んだ状態を避けることができるようになり、中間熱交換器内に液冷媒が溜まり込むことに起因した後段側の圧縮要素における液圧縮が生じさせることなく、中間熱交換器を通じて前段側の圧縮要素から吐出された冷媒を後段側の圧縮要素に吸入させることができる。
この冷凍装置では、冷却運転時に中間熱交換器戻し管への冷媒の流入を防ぐことができるとともに、加熱運転時に熱源側熱交換器を流れる冷媒の流量と中間熱交換器を流れる冷媒の流量との分配を確実に行うことができる。
この冷凍装置では、冷却運転時及び加熱運転時のいずれにおいても、膨張装置によって成績係数を高めるとともにエネルギー回収を行うことができるため、冷却運転時及び加熱運転時の運転効率をさらに向上させることができる。
この冷凍装置では、後段側の圧縮要素に中間圧の冷媒を戻す中間圧インジェクションを行うことができるため、運転効率をさらに向上させることができる。
2、102、202、302 圧縮機構
3 切換機構
4 熱源側熱交換器
6 利用側熱交換器
7、307 中間熱交換器
8、308 中間冷媒管
9、309 中間熱交換器バイパス管
92、392 第2吸入戻し管
94、394 中間熱交換器戻し管
94b、394b 中間熱交換器戻し弁(流量調節弁)
97 膨張装置
17 整流回路(ブリッジ回路)
18 レシーバ(気液分離器)
18c 第2後段側インジェクション管
(1)空気調和装置の構成
図1は、本発明にかかる冷凍装置の一実施形態としての空気調和装置1の概略構成図である。空気調和装置1は、冷房運転と暖房運転とが切り換え可能に構成された冷媒回路10を有し、超臨界域で作動する冷媒(ここでは、二酸化炭素)を使用して二段圧縮式冷凍サイクルを行う装置である。
空気調和装置1の冷媒回路10は、主として、圧縮機構2と、切換機構3と、熱源側熱交換器4と、ブリッジ回路17と、レシーバ18と、第1膨張機構5aと、第2膨張機構5bと、利用側熱交換器6と、中間熱交換器7とを有している。
圧縮機構2は、本実施形態において、2つの圧縮要素で冷媒を二段圧縮する圧縮機21から構成されている。圧縮機21は、ケーシング21a内に、圧縮機駆動モータ21bと、駆動軸21cと、圧縮要素2c、2dとが収容された密閉式構造となっている。圧縮機駆動モータ21bは、駆動軸21cに連結されている。そして、この駆動軸21cは、2つの圧縮要素2c、2dに連結されている。すなわち、圧縮機21は、2つの圧縮要素2c、2dが単一の駆動軸21cに連結されており、2つの圧縮要素2c、2dがともに圧縮機駆動モータ21bによって回転駆動される、いわゆる一軸二段圧縮構造となっている。圧縮要素2c、2dは、本実施形態において、ロータリ式やスクロール式等の容積式の圧縮要素である。そして、圧縮機21は、吸入管2aから冷媒を吸入し、この吸入された冷媒を圧縮要素2cによって圧縮した後に中間冷媒管8に吐出し、中間冷媒管8に吐出された冷媒を圧縮要素2dに吸入させて冷媒をさらに圧縮した後に吐出管2bに吐出するように構成されている。ここで、中間冷媒管8は、圧縮要素2dの前段側に接続された圧縮要素2cから吐出された冷凍サイクルにおける中間圧の冷媒を、圧縮要素2cの後段側に接続された圧縮要素2dに吸入させるための冷媒管である。また、吐出管2bは、圧縮機構2から吐出された冷媒を切換機構3に送るための冷媒管であり、吐出管2bには、油分離機構41と逆止機構42とが設けられている。油分離機構41は、圧縮機構2から吐出される冷媒に同伴する冷凍機油を冷媒から分離して圧縮機構2の吸入側へ戻す機構であり、主として、圧縮機構2から吐出される冷媒に同伴する冷凍機油を冷媒から分離する油分離器41aと、油分離器41aに接続されており冷媒から分離された冷凍機油を圧縮機構2の吸入管2aに戻す油戻し管41bとを有している。油戻し管41bには、油戻し管41bを流れる冷凍機油を減圧する減圧機構41cが設けられている。減圧機構41cは、本実施形態において、キャピラリチューブが使用されている。逆止機構42は、圧縮機構2の吐出側から放熱器としての熱源側熱交換器4への冷媒の流れを許容し、かつ、放熱器としての熱源側熱交換器4から圧縮機構2の吐出側への冷媒の流れを遮断するための機構であり、本実施形態において、逆止弁が使用されている。
切換機構3は、冷媒回路10内における冷媒の流れの方向を切り換えるための機構であり、冷房運転時には、熱源側熱交換器4を圧縮機構2によって圧縮される冷媒の放熱器として、かつ、利用側熱交換器6を熱源側熱交換器4において冷却された冷媒の蒸発器として機能させるために、圧縮機構2の吐出側と熱源側熱交換器4の一端とを接続するとともに圧縮機21の吸入側と利用側熱交換器6とを接続し(図1の切換機構3の実線を参照、以下、この切換機構3の状態を「冷却運転状態」とする)、暖房運転時には、利用側熱交換器6を圧縮機構2によって圧縮される冷媒の放熱器として、かつ、熱源側熱交換器4を利用側熱交換器6において冷却された冷媒の蒸発器として機能させるために、圧縮機構2の吐出側と利用側熱交換器6とを接続するとともに圧縮機構2の吸入側と熱源側熱交換器4の一端とを接続することが可能である(図1の切換機構3の破線を参照、以下、この切換機構3の状態を「加熱運転状態」とする)。本実施形態において、切換機構3は、圧縮機構2の吸入側、圧縮機構2の吐出側、熱源側熱交換器4及び利用側熱交換器6に接続された四路切換弁である。尚、切換機構3は、四路切換弁に限定されるものではなく、例えば、複数の電磁弁を組み合わせる等によって、上述と同様の冷媒の流れの方向を切り換える機能を有するように構成したものであってもよい。
熱源側熱交換器4は、冷媒の放熱器又は蒸発器として機能する熱交換器である。熱源側熱交換器4は、その一端が切換機構3に接続されており、その他端がブリッジ回路17を介して第1膨張機構5aに接続されている。尚、ここでは図示しないが、熱源側熱交換器4には、熱源側熱交換器4を流れる冷媒と熱交換を行う冷却源として水や空気が供給されるようになっている。
レシーバ18は、冷房運転と暖房運転との間で冷媒回路10における冷媒の循環量が異なる等の運転状態に応じて発生する余剰冷媒を溜めることができるように、第1膨張機構5aで減圧された後の冷媒を一時的に溜めるために設けられた容器であり、その入口がレシーバ入口管18aに接続されており、その出口がレシーバ出口管18bに接続されている。また、レシーバ18には、レシーバ18内から冷媒を抜き出して圧縮機構2の吸入管2a(すなわち、圧縮機構2の前段側の圧縮要素2cの吸入側)に戻すことが可能な第1吸入戻し管18fが接続されている。この第1吸入戻し管18fには、第1吸入戻し開閉弁18gが設けられている。第1吸入戻し開閉弁18gは、本実施形態において、電磁弁である。
利用側熱交換器6は、冷媒の蒸発器又は放熱器として機能する熱交換器である。利用側熱交換器6は、その一端がブリッジ回路を介して第1膨張機構5aに接続されており、その他端が切換機構3に接続されている。尚、ここでは図示しないが、利用側熱交換器6には、利用側熱交換器6を流れる冷媒と熱交換を行う加熱源としての水や空気が供給されるようになっている。
また、中間冷媒管8には、中間熱交換器7をバイパスするように、中間熱交換器バイパス管9が接続されている。この中間熱交換器バイパス管9は、中間熱交換器7を流れる冷媒の流量を制限する冷媒管である。そして、中間熱交換器バイパス管9には、中間熱交換器バイパス開閉弁11が設けられている。中間熱交換器バイパス開閉弁11は、本実施形態において、電磁弁である。この中間熱交換器バイパス開閉弁11は、本実施形態において、後述の冷房開始制御のような一時的な運転を行う場合を除いて、基本的には、切換機構3を冷却運転状態にしている際に閉め、切換機構3を加熱運転状態にしている際に開ける制御がなされる。すなわち、中間熱交換器バイパス開閉弁11は、冷房運転を行う際に閉め、暖房運転を行う際に開ける制御がなされる。
また、中間冷媒管8には、前段側の圧縮要素2cの吐出側から後段側の圧縮要素2dの吸入側への冷媒の流れを許容し、かつ、後段側の圧縮要素2dの吸入側から前段側の圧縮要素2cの吐出側への冷媒の流れを遮断するための逆止機構15が設けられている。逆止機構15は、本実施形態において、逆止弁である。尚、逆止機構15は、本実施形態において、中間冷媒管8の中間熱交換器7の後段側の圧縮要素2d側端から中間熱交換器バイパス管9の後段側の圧縮要素2d側端との接続部までの部分に設けられている。
さらに、空気調和装置1は、ここでは図示しないが、圧縮機構2、切換機構3、膨張機構5a、5b、中間熱交換器バイパス開閉弁11、中間熱交換器開閉弁12、第1吸入戻し開閉弁18g、第2吸入戻し開閉弁92a、及び中間熱交換器戻し開閉弁94a等の空気調和装置1を構成する各部の動作を制御する制御部を有している。
次に、本実施形態の空気調和装置1の動作について、図1~図9を用いて説明する。ここで、図2は、冷房運転時における空気調和装置1内の冷媒の流れを示す図であり、図3は、冷房運転時の冷凍サイクルが図示された圧力-エンタルピ線図であり、図4は、冷房運転時の冷凍サイクルが図示された温度-エントロピ線図であり、図5は、暖房運転時における空気調和装置1内の冷媒の流れを示す図であり、図6は、暖房運転時の冷凍サイクルが図示された圧力-エンタルピ線図であり、図7は、暖房運転時の冷凍サイクルが図示された温度-エントロピ線図であり、図8は、冷房開始制御のフローチャートであり、図9は、冷房開始制御時における空気調和装置1内の冷媒の流れを示す図である。尚、以下の冷房運転や暖房運転における運転制御、及び、冷房開始制御は、上述の制御部(図示せず)によって行われる。また、以下の説明において、「高圧」とは、冷凍サイクルにおける高圧(すなわち、図3、4の点D、D’、Eにおける圧力や図6、7の点D、D’、Fにおける圧力)を意味し、「低圧」とは、冷凍サイクルにおける低圧(すなわち、図3、4の点A、Fにおける圧力や図6、7の点A、E、Vにおける圧力)を意味し、「中間圧」とは、冷凍サイクルにおける中間圧(すなわち、図3、4の点B1、C1における圧力や図6、7の点B1、C1、C1’における圧力)を意味している。
冷房運転時は、切換機構3が図1及び図2の実線で示される冷却運転状態とされる。また、第1膨張機構5a及び第2膨張機構5bは、開度調節される。そして、切換機構3が冷却運転状態となるため、中間冷媒管8の中間熱交換器開閉弁12が開けられ、そして、中間熱交換器バイパス管9の中間熱交換器バイパス開閉弁11が閉められることによって、中間熱交換器7が冷却器として機能する状態とされるとともに、第2吸入戻し管92の第2吸入戻し開閉弁92aが閉められることによって、中間熱交換器7と圧縮機構2の吸入側とが接続していない状態にされ(但し、後述の冷房開始制御時を除く)、また、中間熱交換器戻し管94の中間熱交換器戻し開閉弁94aが閉められることによって、利用側熱交換器6と熱源側熱交換器4との間と中間熱交換器7とが接続していない状態にされる。
暖房運転時は、切換機構3が図1及び図5の破線で示される加熱運転状態とされる。また、第1膨張機構5a及び第2膨張機構5bは、開度調節される。そして、切換機構3が加熱運転状態となるため、中間冷媒管8の中間熱交換器開閉弁12が閉められ、そして、中間熱交換器バイパス管9の中間熱交換器バイパス開閉弁11が開けられることによって、中間熱交換器7が冷却器として機能しない状態とされる。さらに、切換機構3が加熱運転状態となるため、第2吸入戻し管92の第2吸入戻し開閉弁92aが開けられることによって、中間熱交換器7と圧縮機構2の吸入側とを接続されている状態にされ、また、中間熱交換器戻し管94の中間熱交換器戻し開閉弁94aが開けられることによって、利用側熱交換器6と熱源側熱交換器4との間と中間熱交換器7とが接続されている状態にされる。
上述のような中間熱交換器7では、空気調和装置1の停止時等に、液冷媒が溜まり込むおそれがあり、中間熱交換器7に液冷媒が溜まり込んだ状態で、上述の冷房運転を開始すると、中間熱交換器7に溜まり込んだ液冷媒が後段側の圧縮要素2dに吸入されるため、後段側の圧縮要素2cにおいて液圧縮が生じてしまい、圧縮機構2の信頼性が損なわれることになる。
そこで、本実施形態では、上述の冷房運転の開始時に、中間熱交換器バイパス管9を通じて前段側の圧縮要素2cから吐出された冷媒を後段側の圧縮要素2dに吸入させる状態にするとともに、第2吸入戻し管92によって、中間熱交換器7と圧縮機構2の吸入側とを接続させる冷房開始制御を行うようにしている。
まず、ステップS1において、冷房運転開始の指令がなされると、ステップS2の各種弁を操作する処理に移行する。
次に、ステップS2において、開閉弁11、12、92aの開閉状態を、中間熱交換器バイパス管9を通じて前段側の圧縮要素2cから吐出された冷媒を後段側の圧縮要素2dに吸入させるとともに、第2吸入戻し管92を通じて中間熱交換器7と圧縮機構2の吸入側とを接続させる冷媒戻し状態に切り換える。具体的には、中間熱交換器バイパス開閉弁11を開け、そして、中間熱交換器開閉弁12を閉める。そうすると、中間熱交換器バイパス管9によって、前段側の圧縮要素2cから吐出された冷媒が中間熱交換器7を通過することなく後段側の圧縮要素2dに吸入される流れが生じることになる。すなわち、中間熱交換器7が冷却器として機能しない状態にされるとともに、中間熱交換器バイパス管9を通じて前段側の圧縮要素2cから吐出された冷媒が後段側の圧縮要素2dに吸入される状態となる(図9参照)。そして、このような状態において、第2吸入戻し開閉弁92aを開ける。そうすると、第2吸入戻し管92によって、中間熱交換器7と圧縮機構2の吸入側とが接続されて、中間熱交換器7(より具体的には、中間熱交換器7を含む中間熱交換器開閉弁12と逆止機構15との間の部分)における冷媒の圧力が冷凍サイクルにおける低圧付近まで低下し、中間熱交換器7内の冷媒を圧縮機構2の吸入側に抜くことができる状態となる(図9参照)。
次に、ステップS4において、開閉弁11、12、92aの開閉状態を、中間熱交換器7を通じて前段側の圧縮要素2cから吐出された冷媒を後段側の圧縮要素2dに吸入させるとともに第2吸入戻し管92を通じて中間熱交換器7と圧縮機構2の吸入側とを接続させない冷媒不戻し状態に切り換える。すなわち、上述の冷房運転時における弁11、12、92aの開閉状態に移行して、冷房開始制御を終了する。具体的には、第2吸入戻し開閉弁92aを閉める。そうすると、中間熱交換器7内の冷媒が圧縮機構2の吸入側に流出しない状態となる。そして、このような状態において、中間熱交換器開閉弁12を開け、そして、中間熱交換器バイパス開閉弁11を閉める。そうすると、中間熱交換器7が冷却器として機能する状態となる。
(3)変形例1
上述の実施形態においては、冷房運転と冷房開始制御との間の切り換え、すなわち、冷媒不戻し状態と冷媒戻し状態との切り換えを、開閉弁11、12、92aの開閉状態を変化させることによって行うようにしているが、図10に示されるように、開閉弁11、12、92aに代えて、冷媒不戻し状態と冷媒戻し状態とを切り換え可能な中間熱交換器切換弁93を設けた冷媒回路110にしてもよい。
ここで、中間熱交換器切換弁93は、冷媒不戻し状態と冷媒戻し状態に切り換えることが可能な弁であり、本変形例において、中間冷媒管8の前段側の圧縮要素2cの吐出側と、中間冷媒管8の中間熱交換器7の入口側と、中間熱交換器バイパス管9の前段側の圧縮要素2c側端と、第2吸入戻し管92の中間熱交換器7側端に接続された四路切換弁である。また、中間熱交換器バイパス管9には、前段側の圧縮要素2cの吐出側から後段側の圧縮要素2dの吸入側への冷媒の流れを許容し、かつ、後段側の圧縮要素2dの吸入側から前段側の圧縮要素2cの吐出側や圧縮機構2の吸入側への冷媒の流れを遮断するための逆止機構9aがさらに設けられている。逆止機構9aは、本変形例において、逆止弁である。
(4)変形例2
上述の実施形態及びその変形例において、中間熱交換器7及び熱源側熱交換器4を空気を熱源(すなわち、冷却源又は加熱源)とする熱交換器にして、両熱交換器4、7に共通の熱源側ファン40(後述)によって熱源としての空気を供給する構成を採用することが考えられる。
本変形例の空気調和装置1を構成する熱源ユニット1aは、側方から空気を吸い込んで上方に向かって空気を吹き出す、いわゆる、上吹きタイプのものであり、主として、ケーシング71と、ケーシング71の内部に配置される熱源側熱交換器4及び中間熱交換器7等の冷媒回路構成部品や熱源側ファン40等の機器とを有している。
しかし、本変形例では、上述の実施形態及びその変形例と同様、暖房運転時に、中間熱交換器バイパス管9を用いて、前段側の圧縮要素2cから吐出されて後段側の圧縮要素2dに吸入される冷媒が中間熱交換器7において冷却されないようにバイパスするとともに、中間熱交換器7を冷媒の蒸発器として機能させることで、暖房運転時の蒸発能力を高めるのに寄与している。
上述の実施形態及びその変形例においては、切換機構3によって冷房運転と暖房運転とを切換可能に構成された二段圧縮式冷凍サイクルを行う空気調和装置1において、前段側の圧縮要素2cから吐出されて後段側の圧縮要素2dに吸入される冷媒の冷却器として機能する中間熱交換器7、中間熱交換器7をバイパスするように中間冷媒管8に接続されている中間熱交換器バイパス管9、中間熱交換器7の一端と圧縮機構2の吸入側とを接続させるための第2吸入戻し管92、及び利用側熱交換器6と熱源側熱交換器4との間と中間熱交換器7の他端とを接続させるための中間熱交換器戻し管94を設けるようにしているが、この構成に加えて、第1後段側インジェクション管19及びエコノマイザ熱交換器20による中間圧インジェクションを行うようにしてもよい。
第1後段側インジェクション管19は、熱源側熱交換器4と利用側熱交換器6との間を流れる冷媒を分岐して圧縮機構2の後段側の圧縮要素2dに戻す機能を有している。本変形例において、第1後段側インジェクション管19は、レシーバ入口管18aを流れる冷媒を分岐して後段側の圧縮要素2dの吸入側に戻すように設けられている。より具体的には、第1後段側インジェクション管19は、レシーバ入口管18aの第1膨張機構5aの上流側の位置(すなわち、切換機構3を冷却運転状態にしている際には、熱源側熱交換器4と第1膨張機構5aとの間)から冷媒を分岐して中間冷媒管8の中間熱交換器7の下流側の位置に戻すように設けられている。また、この第1後段側インジェクション管19には、開度制御が可能な第1後段側インジェクション弁19aが設けられている。そして、第1後段側インジェクション弁19aは、本変形例において、電動膨張弁である。
次に、本変形例の空気調和装置1の動作について、図14~図18を用いて説明する。ここで、図15は、冷房運転時の冷凍サイクルが図示された圧力-エンタルピ線図であり、図16は、冷房運転時の冷凍サイクルが図示された温度-エントロピ線図であり、図17は、暖房運転時の冷凍サイクルが図示された圧力-エンタルピ線図であり、図18は、暖房運転時の冷凍サイクルが図示された温度-エントロピ線図である。ここで、冷房開始制御については、上述の実施形態と同様であるため、ここでは説明を省略する。また、以下の冷房運転及び暖房運転(ここでは説明しない冷房開始制御も含む)における運転制御は、上述の実施形態における制御部(図示せず)によって行われる。また、以下の説明において、「高圧」とは、冷凍サイクルにおける高圧(すなわち、図15、図16の点D、D’、E、Hにおける圧力や図17、図18の点D、D’、F、Hにおける圧力)を意味し、「低圧」とは、冷凍サイクルにおける低圧(すなわち、図15、16の点A、Fにおける圧力や図17、図18の点A、E、Vにおける圧力)を意味し、「中間圧」とは、冷凍サイクルにおける中間圧(すなわち、図15~図18の点B1、C1、G、J、Kにおける圧力)を意味している。
冷房運転時は、切換機構3が図14の実線で示される冷却運転状態とされる。また、第1膨張機構5a及び第2膨張機構5bは、開度調節される。また、第1後段側インジェクション弁19aも、開度調節される。より具体的には、本変形例において、第1後段側インジェクション弁19aは、エコノマイザ熱交換器20の第1後段側インジェクション管19側の出口における冷媒の過熱度が目標値になるように開度調節される、いわゆる過熱度制御がなされるようになっている。本変形例において、エコノマイザ熱交換器20の第1後段側インジェクション管19側の出口における冷媒の過熱度は、中間圧力センサ54により検出される中間圧を飽和温度に換算し、エコノマイザ出口温度センサ55により検出される冷媒温度からこの冷媒の飽和温度値を差し引くことによって得られる。尚、本変形例では採用していないが、エコノマイザ熱交換器20の第1後段側インジェクション管19側の入口に温度センサを設けて、この温度センサにより検出される冷媒温度をエコノマイザ出口温度センサ55により検出される冷媒温度から差し引くことによって、エコノマイザ熱交換器20の第1後段側インジェクション管19側の出口における冷媒の過熱度を得るようにしてもよい。また、第1後段側インジェクション弁19aの開度調節は、過熱度制御に限られるものではなく、例えば、冷媒回路10における冷媒循環量等に応じて所定開度だけ開けるようにするものであってもよい。そして、切換機構3が冷却運転状態となるため、中間冷媒管8の中間熱交換器開閉弁12が開けられ、そして、中間熱交換器バイパス管9の中間熱交換器バイパス開閉弁11が閉められることによって、中間熱交換器7が冷却器として機能する状態とされるとともに、第2吸入戻し管92の第2吸入戻し開閉弁92aが閉められることによって、中間熱交換器7と圧縮機構2の吸入側とが接続していない状態にされ(但し、冷房開始制御時を除く)、また、中間熱交換器戻し管94の中間熱交換器戻し開閉弁94aが閉められることによって、利用側熱交換器6と熱源側熱交換器4との間と中間熱交換器7とが接続していない状態にされる。
しかも、本変形例の構成では、第1後段側インジェクション管19及びエコノマイザ熱交換器20を設けて熱源側熱交換器4から膨張機構5a、5bに送られる冷媒を分岐して後段側の圧縮要素2dに戻すようにしているため、中間熱交換器7のような外部への放熱を行うことなく、後段側の圧縮要素2dに吸入される冷媒の温度をさらに低く抑えることができる(図16の点C1、G参照)。これにより、圧縮機構2から吐出される冷媒の温度がさらに低く抑えられ(図16の点D、D’参照)、第1後段側インジェクション管19を設けていない場合に比べて、図16の点C1、D’、D、Gを結ぶことによって囲まれる面積に相当する分の放熱ロスをさらに小さくできることから、運転効率をさらに向上させることができる。
暖房運転時は、切換機構3が図14の破線で示される加熱運転状態とされる。また、第1膨張機構5a及び第2膨張機構5bは、開度調節される。また、第1後段側インジェクション弁19aは、上述の冷房運転と同様の開度調節がなされる。そして、切換機構3が加熱運転状態となるため、中間冷媒管8の中間熱交換器開閉弁12が閉められ、そして、中間熱交換器バイパス管9の中間熱交換器バイパス開閉弁11が開けられることによって、中間熱交換器7が冷却器として機能しない状態とされる。さらに、切換機構3が加熱運転状態となるため、第2吸入戻し管92の第2吸入戻し開閉弁92aが開けられることによって、中間熱交換器7と圧縮機構2の吸入側とを接続させる状態とされ、また、中間熱交換器戻し管94の中間熱交換器戻し開閉弁94aが開けられることによって、利用側熱交換器6と熱源側熱交換器4との間と中間熱交換器7とが接続されている状態にされる。
しかも、本変形例の構成では、冷房運転時と同様に、第1後段側インジェクション管19及びエコノマイザ熱交換器20を設けて熱源側熱交換器4から膨張機構5a、5bに送られる冷媒を分岐して後段側の圧縮要素2dに戻すようにしているため、中間熱交換器7のような外部への放熱を行うことなく、後段側の圧縮要素2dに吸入される冷媒の温度をさらに低く抑えることができる(図18の点B1、G参照)。これにより、圧縮機構2から吐出される冷媒の温度がさらに低く抑えられ(図18の点D、D’参照)、第1後段側インジェクション管19を設けていない場合に比べて、図18の点B1、D’、D、Gを結ぶことによって囲まれる面積に相当する分の放熱ロスを小さくできることから、運転効率をさらに向上させることができる。
また、冷房運転及び暖房運転に共通する利点として、本変形例の構成では、エコノマイザ熱交換器20として、熱源側熱交換器4又は利用側熱交換器6から膨張機構5a、5bに送られる冷媒と後段側インジェクション管19を流れる冷媒とが対向するように流れる流路を有する熱交換器を採用しているため、エコノマイザ熱交換器20における熱源側熱交換器4又は利用側熱交換器6から膨張機構5a、5bに送られる冷媒と後段側インジェクション管19を流れる冷媒との温度差を小さくすることができ、高い熱交換効率を得ることができる。
さらに、変形例2のような熱源ユニット1aの構成を採用する場合には、特に有利な効果を得ることができる。
(6)変形例4
上述の変形例3における冷媒回路210(図14参照)においては、上述のように、切換機構3を冷却運転状態にする冷房運転及び切換機構3を加熱運転状態にする暖房運転のいずれにおいても、エコノマイザ熱交換器20による中間圧インジェクションを行うことで、後段側の圧縮要素2dから吐出される冷媒の温度を低下させるとともに、圧縮機構2の消費動力を減らし、運転効率の向上を図るようにしている。そして、エコノマイザ熱交換器20による中間圧インジェクションは、冷凍サイクルにおける中間圧が臨界圧力付近まで上昇した条件においても使用可能であることから、上述の実施形態及びその変形例における冷媒回路10、110、210(図1、10、14参照)のように、1つの利用側熱交換器6を有する構成では、超臨界域で作動する冷媒を使用する場合には、特に、有利であると考えられる。
例えば、詳細は図示しないが、上述の変形例3におけるブリッジ回路17を有する冷媒回路210(図14参照)において、互いが並列に接続された複数(ここでは、2つ)の利用側熱交換器6を設けるとともに、気液分離器としてのレシーバ18(より具体的には、ブリッジ回路17)と利用側熱交換器6との間において各利用側熱交換器6に対応するように利用側膨張機構5cを設け(図19参照)、レシーバ出口管18bに設けられていた第2膨張機構5bを削除し、また、ブリッジ回路17の出口逆止弁17dに代えて、暖房運転時に冷凍サイクルにおける低圧まで冷媒を減圧する第3膨張機構を設けることが考えられる。
しかし、切換機構3を加熱運転状態にする暖房運転のように、各利用側膨張機構5cが放熱器としての各利用側熱交換器6において必要とされる冷凍負荷が得られるように放熱器としての各利用側熱交換器6を流れる冷媒の流量を制御しており、放熱器としての各利用側熱交換器6を通過する冷媒の流量が、放熱器としての各利用側熱交換器6の下流側でかつエコノマイザ熱交換器20の上流側に設けられた利用側膨張機構5cの開度制御による冷媒の減圧操作によって概ね決定される条件においては、各利用側膨張機構5cの開度制御による冷媒の減圧の程度が、放熱器としての各利用側熱交換器6を流れる冷媒の流量だけでなく、複数の放熱器としての利用側熱交換器6間の流量分配の状態によって変動することになり、複数の利用側膨張機構5c間で減圧の程度が大きく異なる状態が生じたり、利用側膨張機構5cにおける減圧の程度が比較的大きくなったりする場合があるため、エコノマイザ熱交換器20の入口における冷媒の圧力が低くなるおそれがあり、このような場合には、エコノマイザ熱交換器20における交換熱量(すなわち、第1後段側インジェクション管19を流れる冷媒の流量)が小さくなってしまい使用が困難になるおそれがある。特に、このような空気調和装置1を、主として圧縮機構2、熱源側熱交換器4及びレシーバ18を含む熱源ユニットと、主として利用側熱交換器6を含む利用ユニットとが連絡配管によって接続されたセパレート型の空気調和装置として構成する場合には、利用ユニット及び熱源ユニットの配置によっては、この連絡配管が非常に長くなることがあり得るため、その圧力損失による影響も加わり、エコノマイザ熱交換器20の入口における冷媒の圧力がさらに低下することになる。そして、エコノマイザ熱交換器20の入口における冷媒の圧力が低下するおそれがある場合には、気液分離器圧力が臨界圧力よりも低い圧力であれば気液分離器圧力と冷凍サイクルにおける中間圧(ここでは、中間冷媒管8を流れる冷媒の圧力)との圧力差が小さい条件であっても使用可能な気液分離器による中間圧インジェクションが有利である。
尚、第2後段側インジェクション管18cは、レシーバ18から冷媒を抜き出して圧縮機構2の後段側の圧縮要素2dに戻す中間圧インジェクションを行うことが可能な冷媒管であり、本変形例において、レシーバ18の上部と中間冷媒管8(すなわち、圧縮機構2の後段側の圧縮要素2dの吸入側)とを接続するように設けられている。この第2後段側インジェクション管18cには、第2後段側インジェクション開閉弁18dと第2後段側インジェクション逆止機構18eとが設けられている。第2後段側インジェクション開閉弁18dは、開閉動作が可能な弁であり、本変形例において、電磁弁である。第2後段側インジェクション逆止機構18eは、レシーバ18から後段側の圧縮要素2dへの冷媒の流れを許容し、かつ、後段側の圧縮要素2dからレシーバ18への冷媒の流れを遮断するための機構であり、本変形例において、逆止弁が使用されている。尚、第2後段側インジェクション管18cと第1吸入戻し管18fとは、レシーバ18側の部分が一体となっている。また、第2後段側インジェクション管18cと第1後段側インジェクション管19とは、中間冷媒管8側の部分が一体となっている。また、本変形例において、利用側膨張機構5cは、電動膨張弁である。また、本変形例では、上述のように、第1後段側インジェクション管19及びエコノマイザ熱交換器20を冷房運転時に使用し、第2後段側インジェクション管18cを暖房運転時に使用するようにしていることから、エコノマイザ熱交換器20への冷媒の流通方向を冷房運転及び暖房運転を問わず一定にする必要がないため、ブリッジ回路17を省略して、冷媒回路310の構成を簡単なものとしている。
冷房運転時は、切換機構3が図19の実線で示される冷却運転状態とされる。熱源側膨張機構としての第1膨張機構5a及び利用側膨張機構5cは、開度調節される。そして、切換機構3が冷却運転状態となるため、中間冷媒管8の中間熱交換器開閉弁12が開けられ、そして、中間熱交換器バイパス管9の中間熱交換器バイパス開閉弁11が閉められることによって、中間熱交換器7が冷却器として機能する状態とされるとともに、第2吸入戻し管92の第2吸入戻し開閉弁92aが閉められることによって、中間熱交換器7と圧縮機構2の吸入側とが接続していない状態にされ(但し、冷房開始制御時を除く)、また、中間熱交換器戻し管94の中間熱交換器戻し開閉弁94aが閉められることによって、利用側熱交換器6と熱源側熱交換器4との間と中間熱交換器7とが接続していない状態にされる。また、切換機構3を冷却運転状態にしている際には、気液分離器としてのレシーバ18による中間圧インジェクションを行わずに、第1後段側インジェクション管19を通じて、エコノマイザ熱交換器20において加熱された冷媒を後段側の圧縮要素2dに戻すエコノマイザ熱交換器20による中間圧インジェクションを行うようにしている。より具体的には、第2後段側インジェクション開閉弁18dは閉状態にされて、第1後段側インジェクション弁19aは、上述の変形例3と同様の開度調節がなされる。
暖房運転時は、切換機構3が図19の破線で示される加熱運転状態とされる。熱源側膨張機構としての第1膨張機構5a及び利用側膨張機構5cは、開度調節される。そして、切換機構3が加熱運転状態となるため、中間冷媒管8の中間熱交換器開閉弁12が閉められ、そして、中間熱交換器バイパス管9の中間熱交換器バイパス開閉弁11が開けられることによって、中間熱交換器7が冷却器として機能しない状態とされる。さらに、切換機構3が加熱運転状態となるため、第2吸入戻し管92の第2吸入戻し開閉弁92aが開けられることによって、中間熱交換器7と圧縮機構2の吸入側とを接続させる状態とされ、また、中間熱交換器戻し管94の中間熱交換器戻し開閉弁94aが開けられることによって、利用側熱交換器6と熱源側熱交換器4との間と中間熱交換器7とが接続されている状態にされる。また、切換機構3を加熱運転状態にしている際には、エコノマイザ熱交換器20による中間圧インジェクションを行わずに、第2後段側インジェクション管18cを通じて、気液分離器としてのレシーバ18から冷媒を後段側の圧縮要素2dに戻すレシーバ18による中間圧インジェクションを行うようにしている。より具体的には、第2後段側インジェクション開閉弁18dが開状態にされて、第1後段側インジェクション弁19aが全閉状態にされる。
また、本変形例では、冷房運転と冷房開始制御との間の切り換え、すなわち、冷媒不戻し状態と冷媒戻し状態との切り換えを、開閉弁11、12、92aの開閉状態によって行うようにしているが、上述の変形例1のように、開閉弁11、12、92aに代えて、冷媒不戻し状態と冷媒戻し状態とを切り換え可能な中間熱交換器切換弁93を設けるようにしてもよい。
さらに、変形例2のような熱源ユニット1aの構成を採用する場合には、特に有利な効果を得ることができる。
上述の変形例4における冷媒回路310(図19参照)においては、複数の空調空間の空調負荷に応じた冷房や暖房を行うこと等を目的として、互いに並列に接続された複数の利用側熱交換器6を有する構成にするとともに、各利用側熱交換器6を流れる冷媒の流量を制御して各利用側熱交換器6において必要とされる冷凍負荷を得ることができるようにするために、レシーバ18と利用側熱交換器6との間において各利用側熱交換器6に対応するように利用側膨張機構5cを設けた構成を採用している。このような構成では、冷房運転時において、第1膨張機構5aによって飽和圧力付近まで減圧されてレシーバ18内に一時的に溜められた冷媒(図19の点I参照)が、各利用側膨張機構5cに分配されるが、レシーバ18から各利用側膨張機構5cに送られる冷媒が気液二相状態であると、各利用側膨張機構5cへの分配時に偏流を生じるおそれがあるため、レシーバ18から各利用側膨張機構5cに送られる冷媒をできるだけ過冷却状態にすることが望ましい。
過冷却熱交換器96は、レシーバ18から利用側膨張機構5cに送られる冷媒を冷却する熱交換器である。より具体的には、過冷却熱交換器96は、冷房運転時に、レシーバ18から利用側膨張機構5cに送られる冷媒の一部を分岐して圧縮機構2の吸入側(すなわち、蒸発器としての利用側熱交換器6と圧縮機構2との間の吸入管2a)に戻す第3吸入戻し管95を流れる冷媒との熱交換を行う熱交換器であり、両冷媒が対向するように流れる流路を有している。ここで、第3吸入戻し管95は、放熱器としての熱源側熱交換器4から利用側膨張機構5cに送られる冷媒を分岐して圧縮機構2の吸入側(すなわち、吸入管2a)に戻す冷媒管である。この第3吸入戻し管95には、開度制御が可能な第3吸入戻し弁95aが設けられており、過冷却熱交換器96において、レシーバ18から利用側膨張機構5cに送られる冷媒と第3吸入戻し弁95aにおいて低圧付近まで減圧された後の第3吸入戻し管95を流れる冷媒との熱交換を行うようになっている。第3吸入戻し弁95aは、本変形例において、電動膨張弁である。また、吸入管2a又は圧縮機構2には、圧縮機構2の吸入側を流れる冷媒の圧力を検出する吸入圧力センサ60が設けられている。過冷却熱交換器96の第3吸入戻し管95側の出口には、過冷却熱交換器96の第3吸入戻し管95側の出口における冷媒の温度を検出する過冷却熱交出口温度センサ59が設けられている。
冷房運転時は、切換機構3が図22の実線で示される冷却運転状態とされる。熱源側膨張機構としての第1膨張機構5a及び利用側膨張機構5cは、開度調節される。そして、切換機構3が冷却運転状態となるため、中間冷媒管8の中間熱交換器開閉弁12が開けられ、そして、中間熱交換器バイパス管9の中間熱交換器バイパス開閉弁11が閉められることによって、中間熱交換器7が冷却器として機能する状態とされるとともに、第2吸入戻し管92の第2吸入戻し開閉弁92aが閉められることによって、中間熱交換器7と圧縮機構2の吸入側とが接続していない状態にされ(但し、冷房開始制御時を除く)、また、中間熱交換器戻し管94の中間熱交換器戻し開閉弁94aが閉められることによって、利用側熱交換器6と熱源側熱交換器4との間と中間熱交換器7とが接続していない状態にされる。また、切換機構3を冷却運転状態にしている際には、気液分離器としてのレシーバ18による中間圧インジェクションを行わずに、第1後段側インジェクション管19を通じて、エコノマイザ熱交換器20において加熱された冷媒を後段側の圧縮要素2dに戻すエコノマイザ熱交換器20による中間圧インジェクションを行うようにしている。より具体的には、第2後段側インジェクション開閉弁18dは閉状態にされて、第1後段側インジェクション弁19aは、上述の変形例3と同様の開度調節がなされる。また、切換機構3を冷却運転状態にしている際には、過冷却熱交換器96を使用するため、第3吸入戻し弁95aについても、開度調節される。より具体的には、本変形例において、第3吸入戻し弁95aは、過冷却熱交換器96の第3吸入戻し管95側の出口における冷媒の過熱度が目標値になるように開度調節される、いわゆる過熱度制御がなされるようになっている。本変形例において、過冷却熱交換器96の第3吸入戻し管95側の出口における冷媒の過熱度は、吸入圧力センサ60により検出される低圧を飽和温度に換算し、過冷却熱交出口温度センサ59により検出される冷媒温度からこの冷媒の飽和温度値を差し引くことによって得られる。尚、本変形例では採用していないが、過冷却熱交換器96の第3吸入戻し管95側の入口に温度センサを設けて、この温度センサにより検出される冷媒温度を過冷却熱交出口温度センサ59により検出される冷媒温度から差し引くことによって、過冷却熱交換器96の第3吸入戻し管95側の出口における冷媒の過熱度を得るようにしてもよい。また、第3吸入戻し弁95aの開度調節は、過熱度制御に限られるものではなく、例えば、冷媒回路410における冷媒循環量等に応じて所定開度だけ開けるようにするものであってもよい。
暖房運転時は、切換機構3が図22の破線で示される加熱運転状態とされる。熱源側膨張機構としての第1膨張機構5a及び利用側膨張機構5cは、開度調節される。そして、切換機構3が加熱運転状態となるため、中間冷媒管8の中間熱交換器開閉弁12が閉められ、そして、中間熱交換器バイパス管9の中間熱交換器バイパス開閉弁11が開けられることによって、中間熱交換器7が冷却器として機能しない状態とされる。さらに、切換機構3が加熱運転状態となるため、第2吸入戻し管92の第2吸入戻し開閉弁92aが開けられることによって、中間熱交換器7と圧縮機構2の吸入側とを接続させる状態とされ、また、中間熱交換器戻し管94の中間熱交換器戻し開閉弁94aが開けられることによって、利用側熱交換器6と熱源側熱交換器4との間と中間熱交換器7とが接続されている状態にされる。また、切換機構3を加熱運転状態にしている際には、エコノマイザ熱交換器20による中間圧インジェクションを行わずに、第2後段側インジェクション管18cを通じて、気液分離器としてのレシーバ18から冷媒を後段側の圧縮要素2dに戻すレシーバ18による中間圧インジェクションを行うようにしている。より具体的には、第2後段側インジェクション開閉弁18dが開状態にされて、第1後段側インジェクション弁19aが全閉状態にされる。また、切換機構3を加熱運転状態にしている際には、過冷却熱交換器96を使用しないため、第3吸入戻し弁95aについても全閉状態にされる。
また、本変形例では、冷房運転と冷房開始制御との間の切り換え、すなわち、冷媒不戻し状態と冷媒戻し状態との切り換えを、開閉弁11、12、92aの開閉状態によって行うようにしているが、上述の変形例1のように、開閉弁11、12、92aに代えて、冷媒不戻し状態と冷媒戻し状態とを切り換え可能な中間熱交換器切換弁93を設けるようにしてもよい。
(8)変形例6
上述の実施形態及びその変形例では、1台の一軸二段圧縮構造の圧縮機21によって、2つの圧縮要素2c、2dのうちの前段側の圧縮要素から吐出された冷媒を後段側の圧縮要素で順次圧縮する二段圧縮式の圧縮機構2が構成されているが、三段圧縮式等のような二段圧縮式よりも多段の圧縮機構を採用してもよいし、また、単一の圧縮要素が組み込まれた圧縮機及び/又は複数の圧縮要素が組み込まれた圧縮機を複数台直列に接続することで多段の圧縮機構を構成してもよい。また、利用側熱交換器6が多数接続される場合等のように、圧縮機構の能力を大きくする必要がある場合には、多段圧縮式の圧縮機構を2系統以上並列に接続した並列多段圧縮式の圧縮機構を採用してもよい。
第1圧縮機構103は、本変形例において、2つの圧縮要素103c、103dで冷媒を二段圧縮する圧縮機29から構成されており、圧縮機構102の吸入母管102aから分岐された第1吸入枝管103a、及び、圧縮機構102の吐出母管102bに合流する第1吐出枝管103bに接続されている。第2圧縮機構104は、本変形例において、2つの圧縮要素104c、104dで冷媒を二段圧縮する圧縮機30から構成されており、圧縮機構102の吸入母管102aから分岐された第2吸入枝管104a、及び、圧縮機構102の吐出母管102bに合流する第2吐出枝管104bに接続されている。尚、圧縮機29、30は、上述の実施形態及びその変形例における圧縮機21と同様の構成であるため、圧縮要素103c、103d、104c、104dを除く各部を示す符号をそれぞれ29番台や30番台に置き換えることとし、ここでは、説明を省略する。そして、圧縮機29は、第1吸入枝管103aから冷媒を吸入し、この吸入された冷媒を圧縮要素103cによって圧縮した後に中間冷媒管8を構成する第1入口側中間枝管81に吐出し、第1入口側中間枝管81に吐出された冷媒を中間冷媒管8を構成する中間母管82及び第1出口側中間枝管83を通じて圧縮要素103dに吸入させて冷媒をさらに圧縮した後に第1吐出枝管103bに吐出するように構成されている。圧縮機30は、第1吸入枝管104aから冷媒を吸入し、この吸入された冷媒を圧縮要素104cによって圧縮した後に中間冷媒管8を構成する第2入口側中間枝管84に吐出し、第2入口側中間枝管84に吐出された冷媒を中間冷媒管8を構成する中間母管82及び第2出口側中間枝管85を通じて圧縮要素104dに吸入させて冷媒をさらに圧縮した後に第2吐出枝管104bに吐出するように構成されている。中間冷媒管8は、本変形例において、圧縮要素103d、104dの前段側に接続された圧縮要素103c、104cから吐出された冷媒を、圧縮要素103c、104cの後段側に接続された圧縮要素103d、104dに吸入させるための冷媒管であり、主として、第1圧縮機構103の前段側の圧縮要素103cの吐出側に接続される第1入口側中間枝管81と、第2圧縮機構104の前段側の圧縮要素104cの吐出側に接続される第2入口側中間枝管84と、両入口側中間枝管81、84が合流する中間母管82と、中間母管82から分岐されて第1圧縮機構103の後段側の圧縮要素103dの吸入側に接続される第1出口側中間枝管83と、中間母管82から分岐されて第2圧縮機構104の後段側の圧縮要素104dの吸入側に接続される第2出口側中間枝管85とを有している。また、吐出母管102bは、圧縮機構102から吐出された冷媒を切換機構3に送るための冷媒管であり、吐出母管102bに接続される第1吐出枝管103bには、第1油分離機構141と第1逆止機構142とが設けられており、吐出母管102bに接続される第2吐出枝管104bには、第2油分離機構143と第2逆止機構144とが設けられている。第1油分離機構141は、第1圧縮機構103から吐出される冷媒に同伴する冷凍機油を冷媒から分離して圧縮機構102の吸入側へ戻す機構であり、主として、第1圧縮機構103から吐出される冷媒に同伴する冷凍機油を冷媒から分離する第1油分離器141aと、第1油分離器141aに接続されており冷媒から分離された冷凍機油を圧縮機構102の吸入側に戻す第1油戻し管141bとを有している。第2油分離機構143は、第2圧縮機構104から吐出される冷媒に同伴する冷凍機油を冷媒から分離して圧縮機構102の吸入側へ戻す機構であり、主として、第2圧縮機構104から吐出される冷媒に同伴する冷凍機油を冷媒から分離する第2油分離器143aと、第2油分離器143aに接続されており冷媒から分離された冷凍機油を圧縮機構102の吸入側に戻す第2油戻し管143bとを有している。本変形例において、第1油戻し管141bは、第2吸入枝管104aに接続されており、第2油戻し管143cは、第1吸入枝管103aに接続されている。このため、第1圧縮機構103内に溜まった冷凍機油の量と第2圧縮機構104内に溜まった冷凍機油の量との間に偏りに起因して第1圧縮機構103から吐出される冷媒に同伴する冷凍機油の量と第2圧縮機構104から吐出される冷媒に同伴する冷凍機油の量との間に偏りが生じた場合であっても、圧縮機構103、104のうち冷凍機油の量が少ない方に冷凍機油が多く戻ることになり、第1圧縮機構103内に溜まった冷凍機油の量と第2圧縮機構104内に溜まった冷凍機油の量との間の偏りが解消されるようになっている。また、本変形例において、第1吸入枝管103aは、第2油戻し管143bとの合流部から吸入母管102aとの合流部までの間の部分が、吸入母管102aとの合流部に向かって下り勾配になるように構成されており、第2吸入枝管104aは、第1油戻し管141bとの合流部から吸入母管102aとの合流部までの間の部分が、吸入母管102aとの合流部に向かって下り勾配になるように構成されている。このため、圧縮機構103、104のいずれか一方が停止中であっても、運転中の圧縮機構に対応する油戻し管から停止中の圧縮機構に対応する吸入枝管に戻される冷凍機油は、吸入母管102aに戻ることになり、運転中の圧縮機構の油切れが生じにくくなっている。油戻し管141b、143bには、油戻し管141b、143bを流れる冷凍機油を減圧する減圧機構141c、143cが設けられている。逆止機構142、144は、圧縮機構103、104の吐出側から切換機構3への冷媒の流れを許容し、かつ、切換機構3から圧縮機構103、104の吐出側への冷媒の流れを遮断するための機構である。
中間熱交換器7は、本変形例において、中間冷媒管8を構成する中間母管82に設けられており、第1圧縮機構103の前段側の圧縮要素103cから吐出された冷媒と第2圧縮機構104の前段側の圧縮要素104cから吐出された冷媒とが合流したものを冷却する熱交換器である。すなわち、中間熱交換器7は、2つの圧縮機構103、104に共通の冷却器として機能するものとなっている。このため、多段圧縮式の圧縮機構103、104を複数系統並列に接続した並列多段圧縮式の圧縮機構102に対して中間熱交換器7を設ける際の圧縮機構102周りの回路構成の簡素化が図られている。
そして、本変形例の構成においても、上述の変形例5と同様の作用効果を得ることができる。
また、本変形例では、冷房運転と冷房開始制御との間の切り換え、すなわち、冷媒不戻し状態と冷媒戻し状態との切り換えを、開閉弁11、12、92aの開閉状態によって行うようにしているが、上述の変形例1のように、開閉弁11、12、92aに代えて、冷媒不戻し状態と冷媒戻し状態とを切り換え可能な中間熱交換器切換弁93を設けるようにしてもよい。
(9)変形例7
上述の実施形態及びその変形例では、1台の一軸二段圧縮構造の圧縮機21によって、前段側の圧縮要素から吐出された冷媒を後段側の圧縮要素で順次圧縮する二段圧縮式の圧縮機構2を構成したり、2台の一軸二段圧縮構造の圧縮機29、30を並列接続することによって、前段側の圧縮要素から吐出された冷媒を後段側の圧縮要素で順次圧縮する二段圧縮式の圧縮機構102を構成しているが、単段圧縮構造の圧縮機22、23を直列接続することによって、前段側の圧縮要素から吐出された冷媒を後段側の圧縮要素で順次圧縮する二段圧縮式の圧縮機構を構成してもよい。
圧縮機構202は、本変形例において、前段側の圧縮要素としての圧縮要素2cで冷媒を圧縮する圧縮機22と、後段側の圧縮要素としての圧縮要素2dで冷媒を圧縮する圧縮機22とから構成されている。圧縮機22は、ケーシング22a内に、圧縮機駆動モータ22bと、駆動軸22cと、圧縮要素2cとが収容された密閉式構造となっている。圧縮機駆動モータ22bは、駆動軸22cに連結されている。また、圧縮機23は、ケーシング23a内に、圧縮機駆動モータ23bと、駆動軸23cと、圧縮要素2dとが収容された密閉式構造となっている。圧縮機駆動モータ23bは、駆動軸23cに連結されている。圧縮要素2c、2dは、本変形例において、ロータリ式やスクロール式等の容積式の圧縮要素である。そして、圧縮機構202は、吸入管2aから冷媒を吸入し、この吸入された冷媒を圧縮機22の圧縮要素2cによって圧縮した後に中間冷媒管8に吐出し、中間冷媒管8に吐出された冷媒を圧縮機23の圧縮要素2dに吸入させて冷媒をさらに圧縮した後に吐出管2bに吐出するように構成されている。
そして、本変形例の構成においても、上述の変形例1等と同様の作用効果を得ることができる。
(10)変形例8
上述の実施形態及びその変形例では、中間熱交換器戻し管94に電磁弁からなる中間熱交換器戻し開閉弁94aが設けられており、切換機構3を冷却運転状態にしている際に閉め、切換機構3を加熱運転状態にしている際に開ける制御がなされるようになっているが、この中間熱交換器戻し開閉弁94aに代えて、暖房運転時に冷媒の蒸発器として機能する中間熱交換器7を流れる冷媒の流量を制御することができるように流量調節弁を設けるようにしてもよい。
上述の実施形態及びその変形例の構成において、熱源側熱交換器4と利用側熱交換器6との間に熱源側熱交換器4と利用側熱交換器6との間を流れる冷媒を等エントロピ的に膨張させる膨張装置を設けるようにしてもよい。
例えば、図28に示されるように、上述の変形例8における冷媒回路710(図27参照)において、レシーバ入口管18aに冷媒を等エントロピ的に膨張させる膨張装置97を設けた冷媒回路810にしてもよい。すなわち、本変形例において、膨張装置97は、熱源側熱交換器4から利用側熱交換器6へ向かって冷媒が流れる場合、及び、利用側熱交換器6から熱源側熱交換器4へ向かって冷媒が流れる場合のいずれにおいても膨張装置97の入口から冷媒が流入するように整流する整流回路としてのブリッジ回路17を介して接続されている。また、本変形例において、膨張装置97としては、遠心式や容積式の膨張機が使用されている。尚、本変形例においては、整流回路としてブリッジ回路17が採用されているが、四路切換弁や複数の電磁弁を組み合わせて同様の機能を果たすことができるように構成してもよい。
上述の変形例9の構成において、膨張装置97の出口に位置するレシーバ18を気液分離器として機能させ、レシーバ18において気液分離されたガス冷媒を後段側の圧縮要素2dに戻す後段側インジェクション管を接続するようにして、冷房運転時及び暖房運転時において、気液分離器としてのレシーバ18による中間圧インジェクションを行うようにしてもよい。
例えば、図29に示されるように、上述の変形例9における冷媒回路810(図28参照)において、レシーバ18に第2後段側インジェクション管18cを接続するようにして、気液分離器としてのレシーバ18による中間圧インジェクションを行うことが可能な冷媒回路910にしてもよい。
(13)変形例11
上述の変形例7~10において、複数の空調空間の空調負荷に応じた冷房や暖房を行うこと等を目的として、互いに並列に接続された複数の利用側熱交換器6を有する構成にするようにしてもよい。
そして、本変形例の構成においても、上述の変形例9、10等と同様の作用効果を得ることができる。
上述の変形例7~11において、利用側熱交換器6や熱源側熱交換器4に送られる冷媒を過冷却状態になるように冷却することを目的として、過冷却器を設けるようにしてもよい。
例えば、図32に示されるように、上述の変形例11における冷媒回路1010(図30参照)において、レシーバ出口管18bに過冷却熱交換器96を設けるとともに、レシーバ入口管18aからレシーバ18を経由してレシーバ出口管18bに至るまでの間(ここでは、レシーバ18)に第3吸入戻し管95を設けた冷媒回路1210にしてもよい。
過冷却熱交換器96は、冷房運転時にはレシーバ18から複数(ここでは、2つ)の利用側膨張機構5cを経由して各利用側熱交換器6に、暖房運転時にはレシーバ18から第1膨張機構5a及び中間熱交換器戻し弁94bを経由して熱源側熱交換器4及び中間熱交換器7に送られる冷媒を冷却する熱交換器である。より具体的には、過冷却熱交換器96は、レシーバ18から圧縮機構2の吸入側(すなわち、吸入管2a)に戻す第3吸入戻し管95を流れる冷媒との熱交換を行う熱交換器である。第3吸入戻し管95には、開度制御が可能な第3吸入戻し弁95aが設けられており、過冷却熱交換器96において、冷房運転時には、レシーバ18から利用側膨張機構5cに送られる冷媒と第3吸入戻し弁95aにおいて低圧付近まで減圧された後の第3吸入戻し管95を流れる冷媒との熱交換を行い、レシーバ18から第1膨張機構5a及び中間熱交換器戻し弁94bに送られる冷媒と第3吸入戻し弁95aにおいて低圧付近まで減圧された後の第3吸入戻し管95を流れる冷媒との熱交換を行うようになっている。第3吸入戻し弁95aは、本変形例において、電動膨張弁である。尚、第3吸入戻し管95と第1吸入戻し管18fとは、レシーバ18側の部分が一体となっている。
(15)変形例13
上述の実施形態及びその変形例では、二段圧縮式の圧縮機構2、102、202を採用しているが、三段圧縮式等のような、さらに多段の圧縮機構を採用してもよい。
以上、本発明の実施形態及びその変形例について図面に基づいて説明したが、具体的な構成は、これらの実施形態及びその変形例に限られるものではなく、発明の要旨を逸脱しない範囲で変更可能である。
例えば、上述の実施形態及びその変形例において、利用側熱交換器6を流れる冷媒と熱交換を行う加熱源又は冷却源としての水やブラインを使用するとともに、利用側熱交換器6において熱交換された水やブラインと室内空気とを熱交換させる二次熱交換器を設けた、いわゆる、チラー型の空気調和装置に本発明を適用してもよい。
また、上述のチラータイプの空気調和装置の他の型式の冷凍装置であっても、超臨界域で作動する冷媒を冷媒として使用して多段圧縮式冷凍サイクルを行うものであれば、本発明を適用可能である。
Claims (6)
- 複数の圧縮要素を有しており、前記複数の圧縮要素のうちの前段側の圧縮要素から吐出された冷媒を後段側の圧縮要素で順次圧縮するように構成された圧縮機構(2、102、202、302)と、
冷媒の放熱器又は蒸発器として機能する熱源側熱交換器(4)と、
冷媒の蒸発器又は放熱器として機能する利用側熱交換器(6)と、
前記圧縮機構、冷媒の放熱器として機能する前記熱源側熱交換器、冷媒の蒸発器として機能する前記利用側熱交換器の順に冷媒を循環させる冷却運転状態と、前記圧縮機構、冷媒の放熱器として機能する前記利用側熱交換器、冷媒の蒸発器として機能する前記熱源側熱交換器の順に冷媒を循環させる加熱運転状態とを切り換える切換機構(3)と、
前記切換機構を前記冷却運転状態にしている際に、前記前段側の圧縮要素から吐出されて前記後段側の圧縮要素に吸入される冷媒の冷却器として機能させ、前記切換機構を前記加熱運転状態にしている際に、前記利用側熱交換器において放熱した冷媒の蒸発器として機能させることが可能な中間熱交換器(7、307)と、
を備えた冷凍装置(1)。 - 前記中間熱交換器(7、307)は、前記前段側の圧縮要素から吐出された冷媒を前記後段側の圧縮要素に吸入させるための中間冷媒管(8、308)に設けられており、
前記中間冷媒管には、前記中間熱交換器をバイパスするように中間熱交換器バイパス管(9、309)が接続されており、
前記中間熱交換器の一端と前記圧縮機構(2、102、202、302)の吸入側とを接続させるための吸入戻し管(92、392)と、前記利用側熱交換器(6)と前記熱源側熱交換器(4)との間と前記中間熱交換器の他端とを接続させるための中間熱交換器戻し管(94、394)とをさらに備えている、
請求項1に記載の冷凍装置(1)。 - 前記切換機構(3)を前記冷却運転状態にした運転の開始時に、前記中間熱交換器バイパス管(9、309)を通じて前記前段側の圧縮要素から吐出された冷媒を前記後段側の圧縮要素に吸入させるとともに、前記吸入戻し管(92、392)を通じて前記中間熱交換器(7、307)と前記圧縮機構(2、102、202、302)の吸入側とを接続させる、請求項2に記載の冷凍装置(1)。
- 前記中間熱交換器戻し管(94、394)には、流量調節弁(94b、394b)が設けられている、請求項2又は3に記載の冷凍装置(1)。
- 前記熱源側熱交換器(4)と前記利用側熱交換器(6)との間には、前記熱源側熱交換器と前記利用側熱交換器との間を流れる冷媒を等エントロピ的に膨張させる膨張装置(97)が、前記熱源側熱交換器から前記利用側熱交換器へ向かって冷媒が流れる場合、及び、前記利用側熱交換器から前記熱源側熱交換器へ向かって冷媒が流れる場合のいずれにおいても前記膨張装置の入口から冷媒が流入するように整流する整流回路(17)を介して接続されている、請求項1~4のいずれかに記載の冷凍装置(1)。
- 前記膨張装置(97)の出口には、冷媒の気液分離を行う気液分離器(18)が接続されており、
前記気液分離器には、前記気液分離器において分離されたガス冷媒を前記後段側の圧縮要素に戻すための後段側インジェクション管(18c)が接続されている、
請求項5に記載の空気調和装置(1)。
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EP09714344.0A EP2264380B1 (en) | 2008-02-29 | 2009-02-25 | Refrigeration device |
US12/919,047 US20110005270A1 (en) | 2008-02-29 | 2009-02-25 | Refrigeration apparatus |
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