REFRIGERATION CYCLE APPARATUS

A refrigeration cycle apparatus efficiently performs a cooling operation and a heating operation using a low-pressure refrigerant and a high-pressure refrigerant. A refrigeration cycle apparatus performs a heating operation by performing a two-stage refrigeration cycle, the two-stage refrigeration cycle including a use-side refrigeration cycle using a first refrigerant having 1 MPa or less at 30° C. and a heat-source-side refrigeration cycle using a second refrigerant having 1.5 MPa or Imre at 30° C., and performs a cooling operation by performing a single-stage refrigeration cycle using the first refrigerant.

TECHNICAL FIELD

The present disclosure relates to a refrigeration cycle apparatus.

BACKGROUND ART

To date, refrigeration cycle apparatuses have been proposed that use refrigerants with low global warming potential (GWP), taking into account the global environment.

For example, in a refrigeration cycle apparatus described in PTL 1 (Japanese Unexamined Patent Application Publication No. 2015-197254), it is proposed to fill a refrigerant circuit with a working fluid having a GWP equal to or less than a predetermined value.

SUMMARY

A refrigeration cycle apparatus according to a first aspect performs a heating operation by performing a two-stage refrigeration cycle, the two-stage refrigeration cycle including a use-side refrigeration cycle using a first refrigerant and a heat-source-side refrigeration cycle using a second refrigerant. The first refrigerant has 1 MPa or less at 30° C. The second refrigerant has 1.5 MPa or more at 30° C. The refrigeration cycle apparatus performs a cooling operation by performing a single-stage refrigeration cycle using the first refrigerant.

DESCRIPTION OF EMBODIMENTS

(1) FIRST EMBODIMENT

FIG.1is a schematic configuration diagram of a refrigeration cycle apparatus1according to a first embodiment.FIG.2is a functional block configuration diagram of the refrigeration cycle apparatus1according to the first embodiment.

The refrigeration cycle apparatus1is an apparatus used to process a heat load through a vapor-compression refrigeration cycle operation. The refrigeration cycle apparatus1includes a heat-load circuit90, a first refrigerant circuit10, a second refrigerant circuit20, an outdoor fan9, and a controller7.

The heat load to be processed by the refrigeration cycle apparatus1is not limited, and a fluid such as air, water, or brine may be subjected to heat exchange. In the refrigeration cycle apparatus1according to the present embodiment, water flowing through the heat-load circuit90is supplied to a heat-load heat exchanger91, and the heat load in the heat-load heat exchanger91is processed. The heat-load circuit90is a circuit in which water serving as a heat medium circulates, and includes the heat-load heat exchanger91, a pump92, and a use heat exchanger13shared with the first refrigerant circuit10. The pump92is driven and controlled by the controller7, which will be described below, to circulate the water through the heat-load circuit90. In the heat-load circuit90, the water flows through a heat-load flow path13cincluded in the use heat exchanger13. As described below, the use heat exchanger13includes a first use flow path13athrough which a first refrigerant flowing through the first refrigerant circuit10passes. The water flowing through the heat-load flow path13cof the use heat exchanger13exchanges heat with the first refrigerant flowing through the first use flow path13a. As a result, the water is cooled during a cooling operation and is heated during a heating operation.

The first refrigerant circuit10includes a first compressor11, a first switching mechanism12, the use heat exchanger13shared with the heat-load circuit90, a first use expansion valve15, a second use expansion valve16, a heat-source heat exchanger17shared with the second refrigerant circuit20, and a first outdoor heat exchanger18. The first refrigerant circuit10is filled with the first refrigerant, which is a low-pressure refrigerant, as a refrigerant. The first refrigerant is a refrigerant having 1 MPa or less at 30° C., and is a refrigerant including, for example, at least one of R1234yf or R1234ze. The first refrigerant may include only R1234yf or may include only R1234ze.

The first compressor11is a positive-displacement compressor to be driven by a compressor motor. The compressor motor is driven by electric power supplied via an inverter device. The first compressor11has an operating capacity that is changeable by varying a drive frequency that is the number of rotations of the compressor motor. A discharge side of the first compressor11is connected to the first switching mechanism12. A suction side of the first compressor11is connected to a gas-refrigerant-side outlet of a first heat-source flow path17aof the heat-source heat exchanger17.

The first switching mechanism12includes a switching valve12aand a switching valve12b. The switching valve12aand the switching valve12bare connected in parallel to each other on the discharge side of the first compressor11. The switching valve12ais a three-way valve that switches between a state in which the discharge side of the first compressor11is connected to the first use flow path13aof the use heat exchanger13and a state in which the suction side of the first compressor11is connected to the first use flow path13aof the use heat exchanger13. The switching valve12bis a three-way valve that switches between a state in which the discharge side of the first compressor11is connected to the first outdoor heat exchanger18and a state in which the suction side of the first compressor11is connected to the first outdoor heat exchanger18.

A gas refrigerant side of the first use flow path13aof the use heat exchanger13through which the first refrigerant flowing through the first refrigerant circuit10passes is connected to the switching valve12a. A liquid refrigerant side of the first use flow path13ais connected to a first branch point A included in the first refrigerant circuit10. The first refrigerant evaporates when flowing through the first use flow path13aof the use heat exchanger13to cool the water flowing through the heat-load circuit90. The first refrigerant condenses when flowing through the first use flow path13aof the use heat exchanger13to heat the water flowing through the heat-load circuit90.

At the first branch point A, a flow path extending from the liquid refrigerant side of the first use flow path13a, a flow path extending to the side of the first use expansion valve15opposite to the heat-source heat exchanger17side, and a flow path extending to the side of the second use expansion valve16opposite to the first outdoor heat exchanger18side are connected.

The first use expansion valve15includes an electronic expansion valve that is adjustable in valve opening degree. In the first refrigerant circuit10, the first use expansion valve15is disposed between the first branch point A and an inlet on a liquid refrigerant side of the first heat-source flow path17aof the heat-source heat exchanger17.

The second use expansion valve16includes an electronic expansion valve that is adjustable in valve opening degree. In the first refrigerant circuit10, the second use expansion valve16is disposed between the first branch point A and an outlet on a liquid refrigerant side of the first outdoor heat exchanger18.

The heat-source heat exchanger17is a cascade heat exchanger that includes the first heat-source flow path17athrough which the first refrigerant flowing through the first refrigerant circuit10passes, and a second heat-source flow path17bthrough which a second refrigerant flowing through the second refrigerant circuit20passes, and that exchanges heat between the first refrigerant and the second refrigerant. In the heat-source heat exchanger17, the first heat-source flow path17aand the second heat-source flow path17bare independent of each other, and the first refrigerant and the second refrigerant do not mix with each other. The gas-refrigerant-side outlet of the first heat-source flow path17aof the heat-source beat exchanger17is connected to the suction side of the first compressor11. The inlet on the liquid refrigerant side of the first heat-source flow path17aof the heat-source heat exchanger17is connected to the first use expansion valve15.

The first outdoor heat exchanger18includes a plurality of heat transfer tubes and a plurality of fins joined to the plurality of heat transfer tubes. In the present embodiment, the first outdoor heat exchanger18is arranged outdoors. The first refrigerant flowing through the first outdoor heat exchanger18exchanges heat with air sent to the first outdoor heat exchanger18, thereby allowing the first outdoor heat exchanger18to function as a condenser of the first refrigerant.

The outdoor fan9generates an air flow of outdoor air passing through both the first outdoor heat exchanger18and a second outdoor heat exchanger23.

The second refrigerant circuit20includes a second compressor21, the heat-source heat exchanger17shared with the first refrigerant circuit10, a first heat-source expansion valve26, and the second outdoor beat exchanger23. The second refrigerant circuit20is filled with the second refrigerant, which is a high-pressure refrigerant, as a refrigerant. The second refrigerant is a refrigerant having 1.5 MPa or more at 30° C. The second refrigerant may include carbon dioxide, or may include only carbon dioxide.

The second compressor21is a positive-displacement compressor to be driven by a compressor motor. The compressor motor is driven by electric power supplied via an inverter device. The second compressor21has an operating capacity that is changeable by varying a drive frequency that is the number of rotations of the compressor motor. A discharge side of the second compressor21is connected to an inlet on a gas refrigerant side of the second heat-source flow path17bof the heat-source heat exchanger17. A suction side of the second compressor21is connected to the second outdoor heat exchanger23.

The inlet on the gas refrigerant side of the second heat-source flow path17bof the heat-source heat exchanger17is connected to the discharge side of the second compressor21. An outlet on a liquid refrigerant side of the second heat-source flow path17bof the heat-source heat exchanger17is connected to the first heat-source expansion valve26.

The first heat-source expansion valve26is disposed in a flow path between the liquid refrigerant side of the second heat-source flow path17bof the heat-source heat exchanger17and a liquid refrigerant side of the second outdoor heat exchanger23.

The second outdoor heat exchanger23includes a plurality of heat transfer tubes and a plurality of fins joined to the plurality of heat transfer tubes. In the present embodiment, the second outdoor heat exchanger23is arranged outdoors alongside the first outdoor heat exchanger18. The second refrigerant flowing through the second outdoor heat exchanger23exchanges heat with air sent to the second outdoor heat exchanger23, thereby allowing the second outdoor heat exchanger23to function as an evaporator of the second refrigerant.

The controller7controls the operation of the devices included in the heat-load circuit90, the first refrigerant circuit10, and the second refrigerant circuit20. Specifically, the controller7includes a processor serving as a CPU provided for performing control, a memory, and the like.

In the refrigeration cycle apparatus1described above, the controller7controls the devices to execute a refrigeration cycle, thereby performing a cooling operation for processing a cooling load in the heat-load heat exchanger91and a heating operation for processing a heating load in the heat-load heat exchanger91.

(1-1) Cooling Operation

During the cooling operation, as illustrated inFIG.3, the first refrigerant circuit10performs a single-stage refrigeration cycle such that the use heat exchanger13functions as an evaporator of the first refrigerant and the first outdoor heat exchanger18functions as a condenser of the first refrigerant, and the second refrigerant circuit20does not perform a refrigeration cycle. Specifically, the switching valves12aand12bof the first switching mechanism12are switched to a connection state indicated by solid lines inFIG.3, the pump92, the first compressor11, and the outdoor fan9are driven, the first use expansion valve15is fully closed, and the valve opening degree of the second use expansion valve16is controlled such that the degree of superheating of the first refrigerant to be sucked into the first compressor11satisfies a predetermined condition.

Accordingly, the first refrigerant discharged from the first compressor11is sent to the first outdoor heat exchanger18via the switching valve12bof the first switching mechanism12. The first refrigerant sent to the first outdoor heat exchanger18is condensed by heat exchange with the outdoor air supplied by the outdoor fan9. The first refrigerant having passed through the first outdoor heat exchanger18is decompressed in the second use expansion valve16, passes through the first branch point A, and is sent to the first use flow path13aof the use heat exchanger13. The first refrigerant flowing through the first use flow path13aof the use heat exchanger13is evaporated by heat exchange with the water flowing through the heat-load flow path13cof the use heat exchanger13included in the heat-load circuit90. The water cooled by this heat exchange is sent to the heat-load heat exchanger91in the heat-load circuit to process the cooling load. The first refrigerant evaporated in the first use flow path13aof the use heat exchanger13is sucked into the first compressor11via the switching valve12aof the first switching mechanism12.

(1-2) Heating Operation

During the heating operation, as illustrated inFIG.4, the first refrigerant circuit10performs a refrigeration cycle such that the use heat exchanger13functions as a condenser of the first refrigerant and the heat-source heat exchanger17functions as an evaporator of the first refrigerant, and the second refrigerant circuit20performs a refrigeration cycle such that the heat-source heat exchanger17functions as a radiator of the second refrigerant and the second outdoor heat exchanger23functions as an evaporator of the second refrigerant. As a result, a two-stage refrigeration cycle is performed by the second refrigerant circuit20and the first refrigerant circuit10during the heating operation. Specifically, the switching valves12aand12bof the first switching mechanism12are switched to a connection state indicated by broken lines inFIG.4, the pump92, the first compressor11, the second compressor21, and the outdoor fan9are driven, the second use expansion valve16is fully closed, the valve opening degree of the first use expansion valve15is controlled such that the degree of superheating of the first refrigerant to be sucked into the first compressor11satisfies a predetermined condition, and the valve opening degree of the first heat-source expansion valve26is controlled such that the degree of superheating of the second refrigerant to be sucked into the second compressor21satisfies a predetermined condition.

Accordingly, the second refrigerant discharged from the second compressor21is sent to the heat-source heat exchanger17. When flowing through the second heat-source flow path17b, the second refrigerant radiates heat by heat exchange with the first refrigerant flowing through the first heat-source flow path17a. The second refrigerant, which has radiated heat in the heat-source heat exchanger17, is decompressed in the first heat-source expansion valve26. Then, the second refrigerant is evaporated by heat exchange with the outdoor air supplied by the outdoor fan9in the second outdoor heat exchanger23, and is sucked into the second compressor21. The first refrigerant discharged from the first compressor11is sent to the first use flow path13aof the use heat exchanger13via the switching valve12aof the first switching mechanism12. The first refrigerant flowing through the first use flow path13aof the use heat exchanger13is condensed by heat exchange with the water flowing through the heat-load flow path13cof the use heat exchanger13included in the heat-load circuit90. The water heated by this heat exchange is sent to the heat-load heat exchanger91in the heat-load circuit90to process the heating load. The first refrigerant condensed in the first use flow path13aof the use heat exchanger13passes through the first branch point A and is then decompressed in the first use expansion valve15. The first refrigerant decompressed by the first use expansion valve15is evaporated, when passing through the first heat-source flow path17aof the heat-source heat exchanger17, by heat exchange with the second refrigerant flowing through the second heat-source flow path17b. The first refrigerant evaporated in the first heat-source flow path17aof the heat-source heat exchanger17is sucked into the first compressor11.

(1-3) Features of First Embodiment

In the refrigeration cycle apparatus1according to the first embodiment, the first refrigerant circuit10uses the first refrigerant having a sufficiently low global warming potential (GWP). Further, the second refrigerant circuit20uses the second refrigerant having a sufficiently low ozone depletion potential (ODP) and a sufficiently low global warming potential (GWP). Thus, global environmental deterioration can be reduced.

In addition, even when the first refrigerant circuit10uses the first refrigerant having a sufficiently low global warming potential (GWP), the two-stage refrigeration cycle in which the second refrigerant circuit20is used for the heat-source-side cycle and the first refrigerant circuit10is used for the use-side cycle is performed as the heating operation. This makes it easier to secure heating operation capacity than a single-stage refrigeration cycle in which the first refrigerant, which is a low-pressure refrigerant, is used.

During the cooling operation, the second refrigerant circuit20does not perform a refrigeration cycle, and the first refrigerant circuit10performs the single-stage refrigeration cycle although the second refrigerant circuit20uses carbon dioxide as the second refrigerant. This makes it possible to perform the cooling operation without causing a reduction in COP, as in the case of performing a single-stage refrigeration cycle using a carbon dioxide refrigerant, which is a high-pressure refrigerant, or as in the case of performing a two-stage refrigeration cycle in which carbon dioxide, which is a high-pressure refrigerant, is used in the heat-source-side cycle, the reduction in COP being due to the pressure of the carbon dioxide refrigerant exceeding the critical pressure. It is also possible to reduce the compression strength standards required for the components of the second refrigerant circuit20in which carbon dioxide, which is a high-pressure refrigerant, is used.

(2) SECOND EMBODIMENT

FIG.5is a schematic configuration diagram of a refrigeration cycle apparatus1aaccording to a second embodiment.FIG.6is a functional block configuration diagram of the refrigeration cycle apparatus1aaccording to the second embodiment.

The refrigeration cycle apparatus1ais an apparatus used to process a heat load through a vapor-compression refrigeration cycle operation. The refrigeration cycle apparatus1aincludes a heat-load circuit90, a first refrigerant circuit10, a second refrigerant circuit20, an outdoor fan9, and a controller7.

The heat load to be processed by the refrigeration cycle apparatus1aand the heat-load circuit90are similar to those according to the first embodiment.

A use heat exchanger13includes a heat-load flow path13cthrough which the water flowing through the heat-load circuit90passes, a first use flow path13athrough which the first refrigerant flowing through the first refrigerant circuit10passes, and a second use flow path13bthrough which the second refrigerant flowing through the second refrigerant circuit20passes. The water flowing through the heat-load flow path13cof the use heat exchanger13exchanges heat with the first refrigerant flowing through the first use flow path13aor the second refrigerant flowing through the second use flow path13b. As a result, the water is cooled during a cooling operation and is heated during a heating operation.

The first refrigerant circuit10includes a first compressor11, a first switching mechanism12x, the use heat exchanger13shared with the heat-load circuit90and the second refrigerant circuit20, a second use expansion valve16, a third use expansion valve14, a heat-source heat exchanger17shared with the second refrigerant circuit20, and a first outdoor heat exchanger18. The first refrigerant circuit10is filled with the first refrigerant, which is a low-pressure refrigerant, as a refrigerant. The first refrigerant is a refrigerant having 1 MPa or less at 30° C., and is a refrigerant including, for example, at least one of R1234yf or R1234ze. The first refrigerant may include only R1234yf or may include only R1234ze.

The specific configuration of the first compressor11is similar to that according to the first embodiment. A discharge side of the first compressor11is connected to the first switching mechanism12x. A suction side of the first compressor11is connected to a gas-refrigerant-side outlet of a first heat-source flow path17aof the heat-source heat exchanger17.

The first switching mechanism12xis a four-way switching valve that switches between a state in which the suction side of the first compressor11is connected to the first outdoor heat exchanger18while the discharge side of the first compressor11is connected to the first use flow path13aof the use heat exchanger13, and a state in which the suction side of the first compressor11is connected to the first use flow path13aof the use heat exchanger13while the discharge side of the first compressor11is connected to the first outdoor heat exchanger18.

A gas refrigerant side of the first use flow path13aof the use heat exchanger13through which the first refrigerant flowing through the first refrigerant circuit10passes is connected to the first switching mechanism12x. A liquid refrigerant side of the first use flow path13ais connected to a flow path extending from the third use expansion valve14. The first refrigerant condenses when flowing through the first use flow path13aof the use heat exchanger13to heat the water flowing through the heat-load circuit90.

The third use expansion valve14includes an electronic expansion valve that is adjustable in valve opening degree. The third use expansion valve14is disposed between the use heat exchanger13and a first branch point A in the first refrigerant circuit10.

At the first branch point A, a flow path extending from the third use expansion valve14, a flow path extending from a liquid refrigerant side of the first heat-source flow path17ain the heat-source heat exchanger17, and a flow path extending to the side of the second use expansion valve16opposite to the first outdoor heat exchanger18side are connected.

The second use expansion valve16is similar to that according to the first embodiment.

The heat-source heat exchanger17is similar to that according to the first embodiment. The gas-refrigerant-side outlet of the first heat-source flow path17aof the heat-source heat exchanger17is connected to the suction side of the first compressor11. An inlet on the liquid refrigerant side of the first heat-source flow path17aof the heat-source heat exchanger17is connected to the first branch point A.

The first outdoor heat exchanger18is similar to that according to the first embodiment.

The outdoor fan9generates an air flow of outdoor air passing through both the first outdoor heat exchanger18and a second outdoor heat exchanger23.

The second refrigerant circuit20includes a second compressor21, the use heat exchanger13shared with the heat-load circuit90and the first refrigerant circuit10, the heat-source heat exchanger17shared with the first refrigerant circuit10, a first heat-source expansion valve26, a second heat-source expansion valve24, and the second outdoor heat exchanger23. The second refrigerant circuit20is filled with the second refrigerant, which is a high-pressure refrigerant, as a refrigerant. The second refrigerant is a refrigerant having 1.5 MPa or more at 30° C. The second refrigerant may include carbon dioxide, or may include only carbon dioxide.

The specific configuration of the second compressor21is similar to that according to the first embodiment. A discharge side of the second compressor21is connected to an inlet on a gas refrigerant side of the second heat-source flow path17bof the heat-source heat exchanger17. A suction side of the second compressor21is connected to a flow path extending from a third branch point C in the second refrigerant circuit20.

At the third branch point C, a flow path extending from the suction side of the second compressor21, a flow path extending from an outlet on a gas refrigerant side of the second outdoor heat exchanger23, and a flow path extending from the outlet on the gas refrigerant side of the second use flow path13bof the use heat exchanger13are connected.

The inlet on the gas refrigerant side of the second heat-source flow path17bof the heat-source heat exchanger17is connected to the discharge side of the second compressor21. An outlet on a liquid refrigerant side of the second heat-source flow path17bof the heat-source heat exchanger17is connected to a flow path extending from a second branch point B in the second refrigerant circuit20. The second refrigerant radiates heat when flowing through the second heat-source flow path17bof the heat-source heat exchanger17to evaporate the first refrigerant flowing through the first heat-source flow path17a.

At the second branch point B, a flow path extending from the outlet on the liquid refrigerant side of the second heat-source flow path17bof the heat-source heat exchanger17, a flow path extending from the first heat-source expansion valve26, and a flow path extending from the second heat-source expansion valve24are connected.

The first heat-source expansion valve26is disposed in a flow path between the second branch point B and an inlet on a liquid refrigerant side of the second outdoor heat exchanger23.

The second outdoor heat exchanger23is similar to that according to the first embodiment.

The second heat-source expansion valve24is disposed in a flow path between the second branch point B and an inlet on a liquid refrigerant side of the second use flow path13bof the use heat exchanger13.

The second use flow path13bof the use heat exchanger13through which the second refrigerant flowing through the second refrigerant circuit20passes is disposed in a flow path between the second heat-source expansion valve24and the third branch point C. The second refrigerant evaporates when flowing through the second use flow path13bof the use heat exchanger13to cool the water flowing through the heat-load circuit90.

The controller7controls the operation of the devices included in the heat-load circuit90, the first refrigerant circuit10, and the second refrigerant circuit20. Specifically, the controller7includes a processor serving as a CPU provided for performing control, a memory, and the like.

In the refrigeration cycle apparatus1adescribed above, the controller7controls the devices to execute a refrigeration cycle, thereby performing a cooling operation for processing a cooling load in the heat-load heat exchanger91and a heating operation for processing a heating load in the heat-load heat exchanger91.

(2-1) Cooling Operation

During the cooling operation, as illustrated inFIG.7, while the first refrigerant circuit10performs a refrigeration cycle such that the first outdoor heat exchanger18functions as a condenser of the first refrigerant and the heat-source heat exchanger17functions as an evaporator of the first refrigerant, the second refrigerant circuit20performs a refrigeration cycle such that the heat-source heat exchanger17functions as a radiator of the second refrigerant and the use heat exchanger13functions as an evaporator of the second refrigerant. As a result, a two-stage refrigeration cycle is performed. Specifically, the first switching mechanism12xis switched to a connection state indicated by solid lines inFIG.7, the pump92, the first compressor11, the second compressor21, and the outdoor fan9are driven, the third use expansion valve14is fully closed, the first heat-source expansion valve26is fully closed, the valve opening degree of the second use expansion valve16is controlled such that the degree of superheating of the first refrigerant to be sucked into the first compressor11satisfies a predetermined condition, and the valve opening degree of the second heat-source expansion valve24is controlled such that the degree of superheating of the second refrigerant to be sucked into the second compressor21satisfies a predetermined condition.

Accordingly, the first refrigerant discharged from the first compressor11is sent to the first outdoor heat exchanger18via the first switching mechanism12x. The first refrigerant sent to the first outdoor heat exchanger18is condensed by heat exchange with the outdoor air supplied by the outdoor fan9. The first refrigerant having passed through the first outdoor heat exchanger18is decompressed in the second use expansion valve16, passes through the first branch point A, and is sent to the first heat-source flow path17aof the heat-source heat exchanger17. The first refrigerant flowing through the first heat-source flow path17aof the heat-source heat exchanger17is evaporated by heat exchange with the second refrigerant flowing through the second heat-source flow path17bof the heat-source heat exchanger17. The first refrigerant evaporated in the first heat-source flow path17aof the heat-source heat exchanger17is sucked into the first compressor11.

The second refrigerant discharged from the second compressor21is sent to the second heat-source flow path17bof the heat-source heat exchanger17. The second refrigerant flowing through the second heat-source flow path17bof the heat-source heat exchanger17radiates heat by heat exchange with the first refrigerant flowing through the first heat-source flow path17aof the heat-source heat exchanger17. The second refrigerant having passed through the second heat-source flow path17bof the heat-source heat exchanger17is decompressed in the second heat-source expansion valve24via the second branch point B, and flows into the use heat exchanger13. The second refrigerant flowing through the second use flow path13bof the use heat exchanger13is evaporated by heat exchange with the water flowing through the heat-load flow path13cof the use heat exchanger13included in the heat-load circuit90. The water cooled by this heat exchange is sent to the heat-load heat exchanger91in the heat-load circuit90to process the cooling load. The second refrigerant having passed through the second use flow path13bof the use heat exchanger13is sucked into the second compressor21.

(2-2) Heating Operation

During the heating operation, as illustrated inFIG.8, the first refrigerant circuit10performs a refrigeration cycle such that the use heat exchanger13functions as a condenser of the first refrigerant and the heat-source heat exchanger17functions as an evaporator of the first refrigerant, and the second refrigerant circuit20performs a refrigeration cycle such that the heat-source heat exchanger17functions as a radiator of the second refrigerant and the second outdoor heat exchanger23functions as an evaporator of the second refrigerant. As a result, a two-stage refrigeration cycle is performed by the second refrigerant circuit20and the first refrigerant circuit10during the heating operation. Specifically, the first switching mechanism12xis switched to a connection state indicated by broken lines inFIG.8, the pump92, the first compressor11, the second compressor21, and the outdoor fan9are driven, the second use expansion valve16is fully closed, the second heat-source expansion valve24is fully closed, the valve opening degree of the third use expansion valve14is controlled such that the degree of superheating of the first refrigerant to be sucked into the first compressor11satisfies a predetermined condition, and the valve opening degree of the first heat-source expansion valve26is controlled such that the degree of superheating of the second refrigerant to be sucked into the second compressor21satisfies a predetermined condition.

Accordingly, the second refrigerant discharged from the second compressor21is sent to the heat-source heat exchanger17. When flowing through the second heat-source flow path17b, the second refrigerant radiates heat by heat exchange with the first refrigerant flowing through the first heat-source flow path17a. The second refrigerant, which has radiated heat in the heat-source heat exchanger17, passes through the second branch point B and is then decompressed in the first heat-source expansion valve26. Then, the second refrigerant is evaporated by heat exchange with the outdoor air supplied by the outdoor fan9in the second outdoor heat exchanger23, and is sucked into the second compressor21. The first refrigerant discharged from the first compressor11is sent to the first use flow path13aof the use heat exchanger13via the first switching mechanism12x. The first refrigerant flowing through the first use flow path13aof the use heat exchanger13is condensed by heat exchange with the water flowing through the heat-load flow path13cof the use heat exchanger13included in the heat-load circuit90. The water heated by this heat exchange is sent to the heat-load heat exchanger91in the heat-load circuit90to process the heating load. The first refrigerant condensed in the first use flow path13aof the use heat exchanger13is decompressed in the third use expansion valve14. The first refrigerant decompressed in the third use expansion valve14passes through the first branch point A. After that, when passing through the first heat-source flow path17aof the heat-source heat exchanger17, the first refrigerant is evaporated by heat exchange with the second refrigerant flowing through the second heat-source flow path17b. The first refrigerant evaporated in the first heat-source flow path17aof the heat-source heat exchanger17is sucked into the first compressor11.

(2-3) Features of Second Embodiment

In the refrigeration cycle apparatus1aaccording to the present embodiment, as in the refrigeration cycle apparatus1according to the first embodiment, global environmental deterioration can be reduced. In addition, the two-stage refrigeration cycle is performed during the heating operation, thereby making it easy to secure the capacity. The two-stage refrigeration cycle is also performed during the cooling operation. However, the carbon dioxide refrigerant serving as the second refrigerant does not radiate heat in the second outdoor heat exchanger23, nor is the carbon dioxide refrigerant serving as the second refrigerant evaporated in the heat-source heat exchanger17to condense the first refrigerant. Instead of this, in the heat-source heat exchanger17, the carbon dioxide refrigerant serving as the second refrigerant radiates heat to evaporate the first refrigerant. As a result, the second refrigerant is evaporated in the use heat exchanger13to process the cooling load. This makes it possible to perform the cooling operation without causing a reduction in COP due to the pressure of the carbon dioxide refrigerant exceeding the critical pressure when the cooling operation is performed using the carbon dioxide refrigerant in the heat-source-side cycle of the two-stage refrigeration cycle. It is also possible to reduce the compression strength standards required for the components of the second refrigerant circuit20in which carbon dioxide, which is a high-pressure refrigerant, is used.

FIG.9is a schematic configuration diagram of a refrigeration cycle apparatus1baccording to a third embodiment.FIG.10is a functional block configuration diagram of the refrigeration cycle apparatus1baccording to the third embodiment.

The refrigeration cycle apparatus1bis an apparatus used to process a heat load through a vapor-compression refrigeration cycle operation. The refrigeration cycle apparatus1bincludes a heat-load circuit90, a first refrigerant circuit10, a second refrigerant circuit20, an outdoor fan9, and a controller7.

The heat load to be processed by the refrigeration cycle apparatus1band the heat-load circuit90are similar to those according to the first embodiment.

A use heat exchanger13includes a heat-load flow path13cthrough which the water flowing through the heat-load circuit90passes, a first use flow path13athrough which the first refrigerant flowing through the first refrigerant circuit10passes, and a second use flow path13bthrough which the second refrigerant flowing through the second refrigerant circuit20passes. The water flowing through the heat-load flow path13cof the use heat exchanger13exchanges heat with the first refrigerant flowing through the first use flow path13aor the second refrigerant flowing through the second use flow path13b. As a result, the water is cooled during a cooling operation and is heated during a heating operation.

The first refrigerant circuit10includes a first compressor11, a first switching mechanism12, the use heat exchanger13shared with the heat-load circuit90and the second refrigerant circuit20, a first use expansion valve15, a second use expansion valve16, a third use expansion valve14, a heat-source heat exchanger17shared with the second refrigerant circuit20, and a first outdoor heat exchanger18. The first refrigerant circuit10is filled with the first refrigerant, which is a low-pressure refrigerant, as a refrigerant. The first refrigerant is a refrigerant having 1 MPa or less at 30° C., and is a refrigerant including, for example, at least one of R1234yf or R1234ze. The first refrigerant may include only R1234yf or may include only R1234ze.

The specific configuration of the first compressor11is similar to that according to the first embodiment. A discharge side of the first compressor11is connected to the first switching mechanism12. A suction side of the first compressor11is connected to a gas-refrigerant-side outlet of a first heat-source flow path17aof the heat-source heat exchanger17.

The first switching mechanism12includes a switching valve12aand a switching valve12b. The switching valve12aand the switching valve12bare connected in parallel to each other on the discharge side of the first compressor11. The switching valve12ais a three-way valve that switches between a state in which the discharge side of the first compressor11is connected to the first use flow path13aof the use heat exchanger13and a state in which the suction side of the first compressor11is connected to the first use flow path13aof the use heat exchanger13. The switching valve12bis a three-way valve that switches between a state in which the discharge side of the first compressor11is connected to the first outdoor heat exchanger18and a state in which the suction side of the first compressor11is connected to the first outdoor heat exchanger18.

A gas refrigerant side of the first use flow path13aof the use heat exchanger13through which the first refrigerant flowing through the first refrigerant circuit10passes is connected to the switching valve12aof the first switching mechanism12. A liquid refrigerant side of the first use flow path13ais connected to a flow path extending from the third use expansion valve14. The first refrigerant condenses when flowing through the first use flow path13aof the use heat exchanger13to heat the water flowing through the heat-load circuit90.

The third use expansion valve14includes an electronic expansion valve that is adjustable in valve opening degree. The third use expansion valve14is disposed between the use heat exchanger13and a first branch point A in the first refrigerant circuit10.

At the first branch point A, a flow path extending from the third use expansion valve14, a flow path extending from the first use expansion valve15, and a flow path extending to the side of the second use expansion valve16opposite to the first outdoor heat exchanger18side are connected.

The first use expansion valve15is similar to that according to the first embodiment.

The second use expansion valve16is similar to that according to the first embodiment.

The heat-source heat exchanger17is similar to that according to the first embodiment. The gas-refrigerant-side outlet of the first heat-source flow path17aof the heat-source heat exchanger17is connected to the suction side of the first compressor11. An inlet on a liquid refrigerant side of the first heat-source flow path17aof the heat-source heat exchanger17is connected to a flow path extending from the first use expansion valve15.

The first outdoor heat exchanger18is similar to that according to the first embodiment.

The outdoor fan9generates an air flow of outdoor air passing through both the first outdoor heat exchanger18and a second outdoor heat exchanger23.

The second refrigerant circuit20includes a second compressor21, the use heat exchanger13shared with the heat-load circuit90and the first refrigerant circuit10, the heat-source heat exchanger17shared with the first refrigerant circuit10, a first heat-source expansion valve26, a second heat-source expansion valve24, and the second outdoor heat exchanger23. The second refrigerant circuit20is filled with the second refrigerant, which is a high-pressure refrigerant, as a refrigerant. The second refrigerant is a refrigerant having 1.5 MPa or more at 30° C. The second refrigerant may include carbon dioxide, or may include only carbon dioxide.

The specific configuration of the second compressor21is similar to that according to the first embodiment. A discharge side of the second compressor21is connected to an inlet on a gas refrigerant side of the second heat-source flow path17bof the heat-source heat exchanger17. A suction side of the second compressor21is connected to a flow path extending from a third branch point C in the second refrigerant circuit20.

At the third branch point C, a flow path extending from the suction side of the second compressor21, a flow path extending from an outlet on a gas refrigerant side of the second outdoor heat exchanger23, and a flow path extending from the outlet on the gas refrigerant side of the second use flow path13bof the use heat exchanger13are connected.

The inlet on the gas refrigerant side of the second heat-source flow path17bof the heat-source heat exchanger17is connected to the discharge side of the second compressor21. An outlet on a liquid refrigerant side of the second heat-source flow path17bof the heat-source heat exchanger17is connected to a flow path extending from a second branch point B in the second refrigerant circuit20. The second refrigerant radiates heat when flowing through the second heat-source flow path17bof the heat-source heat exchanger17to evaporate the first refrigerant flowing through the first heat-source flow path17a.

At the second branch point B, a flow path extending from the outlet on the liquid refrigerant side of the second heat-source flow path17bof the heat-source heat exchanger17, a flow path extending from the first heat-source expansion valve26, and a flow path extending from the second heat-source expansion valve24are connected.

The first heat-source expansion valve26is disposed in a flow path between the second branch point B and an inlet on a liquid refrigerant side of the second outdoor heat exchanger23.

The second outdoor heat exchanger23is similar to that according to the first embodiment.

The second heat-source expansion valve24is disposed in a flow path between the second branch point B and an inlet on a liquid refrigerant side of the second use flow path13bof the use heat exchanger13.

The second use flow path13bof the use heat exchanger13through which the second refrigerant flowing through the second refrigerant circuit20passes is disposed in a flow path between the second heat-source expansion valve24and the third branch point C. The second refrigerant evaporates when flowing through the second use flow path13bof the use heat exchanger13to cool the water flowing through the heat-load circuit90.

The controller7controls the operation of the devices included in the heat-load circuit90, the first refrigerant circuit10, and the second refrigerant circuit20. Specifically, the controller7includes a processor serving as a CPU provided for performing control, a memory, and the like.

In the refrigeration cycle apparatus1bdescribed above, the controller7controls the devices to execute a refrigeration cycle, thereby performing a cooling operation for processing a cooling load in the heat-load heat exchanger91and a heating operation for processing a heating load in the heat-load heat exchanger91.

(3-1) Cooling Operation

During the cooling operation, as illustrated inFIG.11, while the first refrigerant circuit10performs a refrigeration cycle such that the first outdoor heat exchanger18functions as a condenser of the first refrigerant and the heat-source heat exchanger17functions as an evaporator of the first refrigerant, the second refrigerant circuit20performs a refrigeration cycle such that the heat-source heat exchanger17functions as a radiator of the second refrigerant and the use heat exchanger13functions as an evaporator of the second refrigerant. As a result, a two-stage refrigeration cycle is performed. Specifically, the switching valves12aand12bof the first switching mechanism12are switched to a connection state indicated by solid lines inFIG.11, the pump92, the first compressor11, the second compressor21, and the outdoor fan9are driven, the third use expansion valve14is fully closed, the first heat-source expansion valve26is fully closed, one of the first use expansion valve15and the second use expansion valve16is controlled to be fully opened while the valve opening degree of the other use expansion valve is controlled such that the degree of superheating of the first refrigerant to be sucked into the first compressor11satisfies a predetermined condition, and the valve opening degree of the second heat-source expansion valve24is controlled such that the degree of superheating of the second refrigerant to be sucked into the second compressor21satisfies a predetermined condition.

Accordingly, the first refrigerant discharged from the first compressor11is sent to the first outdoor heat exchanger18via the switching valve12bof the first switching mechanism12. The first refrigerant sent to the first outdoor heat exchanger18is condensed by heat exchange with the outdoor air supplied by the outdoor fan9. The first refrigerant having passed through the first outdoor heat exchanger18is decompressed in the second use expansion valve16and passes through the first branch point A, or is decompressed in the first use expansion valve15after passing through the first branch point A. Then, the first refrigerant is sent to the first heat-source flow path17aof the heat-source heat exchanger17. The first refrigerant flowing through the first heat-source flow path17aof the heat-source heat exchanger17is evaporated by heat exchange with the second refrigerant flowing through the second heat-source flow path17bof the heat-source heat exchanger17. The first refrigerant evaporated in the first heat-source flow path17aof the heat-source heat exchanger17is sucked into the first compressor11.

The second refrigerant discharged from the second compressor21is sent to the second heat-source flow path17bof the heat-source heat exchanger17. The second refrigerant flowing through the second heat-source flow path17bof the heat-source heat exchanger17radiates heat by heat exchange with the first refrigerant flowing through the first heat-source flow path17aof the heat-source heat exchanger17. The second refrigerant having passed through the second heat-source flow path17bof the heat-source heat exchanger17is decompressed in the second heat-source expansion valve24via the second branch point B, and flows into the use heat exchanger13. The second refrigerant flowing through the second use flow path13bof the use heat exchanger13is evaporated by heat exchange with the water flowing through the heat-load flow path13cof the use heat exchanger13included in the heat-load circuit90. The water cooled by this heat exchange is sent to the heat-load heat exchanger91in the heat-load circuit90to process the cooling load. The second refrigerant having passed through the second use flow path13bof the use heat exchanger13is sucked into the second compressor21.

(3-2) Heating Operation

During the heating operation, as illustrated inFIG.12, the first refrigerant circuit10performs a refrigeration cycle such that the use heat exchanger13functions as a condenser of the first refrigerant and the heat-source heat exchanger17functions as an evaporator of the first refrigerant, and the second refrigerant circuit20performs a refrigeration cycle such that the heat-source heat exchanger17functions as a radiator of the second refrigerant and the second outdoor heat exchanger23functions as an evaporator of the second refrigerant. As a result, a two-stage refrigeration cycle is performed by the second refrigerant circuit20and the first refrigerant circuit10during the heating operation. Specifically, the switching valves12aand12bof the first switching mechanism12are switched to a connection state indicated by broken lines inFIG.12, the pump92, the first compressor11, the second compressor21, and the outdoor fan9are driven, the second use expansion valve16is fully closed, the second heat-source expansion valve24is fully closed, the valve opening degree of the third use expansion valve14or the first use expansion valve15is controlled such that the degree of superheating of the first refrigerant to be sucked into the first compressor11satisfies a predetermined condition, and the valve opening degree of the first heat-source expansion valve26is controlled such that the degree of superheating of the second refrigerant to be sucked into the second compressor21satisfies a predetermined condition.

Accordingly, the second refrigerant discharged from the second compressor21is sent to the heat-source heat exchanger17. When flowing through the second heat-source flow path17b, the second refrigerant radiates heat by heat exchange with the first refrigerant flowing through the first heat-source flow path17a. The second refrigerant, which has radiated heat in the heat-source heat exchanger17, passes through the second branch point B and is then decompressed in the first heat-source expansion valve26. Then, the second refrigerant is evaporated by heat exchange with the outdoor air supplied by the outdoor fan9in the second outdoor heat exchanger23, and is sucked into the second compressor21. The first refrigerant discharged from the first compressor11is sent to the first use flow path13aof the use heat exchanger13via the switching valve12aof the first switching mechanism12. The first refrigerant flowing through the first use flow path13aof the use heat exchanger13is condensed by heat exchange with the water flowing through the heat-load flow path13cof the use heat exchanger13included in the heat-load circuit90. The water heated by this heat exchange is sent to the heat-load heat exchanger91in the heat-load circuit90to process the heating load. The first refrigerant condensed in the first use flow path13aof the use heat exchanger13passes through the first branch point A after being decompressed in the third use expansion valve14, or passes through the first branch point A and is then decompressed in the first use expansion valve15. The first refrigerant having passed through the first branch point A is evaporated, when passing through the first heat-source flow path17aof the heat-source heat exchanger17, by heat exchange with the second refrigerant flowing through the second heat-source flow path17b. The first refrigerant evaporated in the first heat-source flow path17aof the heat-source heat exchanger17is sucked into the first compressor11.

(3-3) Features of Third Embodiment

Like the refrigeration cycle apparatus1according to the first embodiment, the refrigeration cycle apparatus1baccording to the present embodiment can reduce global environmental deterioration and can easily secure heating operation capacity. The two-stage refrigeration cycle is also performed during the cooling operation. However, the carbon dioxide refrigerant serving as the second refrigerant does not radiate heat in the second outdoor heat exchanger23, nor is the carbon dioxide refrigerant serving as the second refrigerant evaporated in the heat-source heat exchanger17to condense the first refrigerant. Instead of this, in the heat-source heat exchanger17, the carbon dioxide refrigerant serving as the second refrigerant radiates heat to evaporate the first refrigerant. As a result, the second refrigerant is evaporated in the use heat exchanger13to process the cooling load. This makes it possible to perform the cooling operation without causing a reduction in COP due to the pressure of the carbon dioxide refrigerant exceeding the critical pressure when the cooling operation is performed using the carbon dioxide refrigerant in the heat-source-side cycle of the two-stage refrigeration cycle. It is also possible to reduce the compression strength standards required for the components of the second refrigerant circuit20in which carbon dioxide, which is a high-pressure refrigerant, is used.

FIG.13is a schematic configuration diagram of a refrigeration cycle apparatus1caccording to a fourth embodiment.FIG.14is a functional block configuration diagram of the refrigeration cycle apparatus1caccording to the fourth embodiment.

The refrigeration cycle apparatus1cis an apparatus used to process a heat load through a vapor-compression refrigeration cycle operation. The refrigeration cycle apparatus is includes a heat-load circuit90, a first refrigerant circuit10, a second refrigerant circuit20, an outdoor fan9, and a controller7.

The heat load to be processed by the refrigeration cycle apparatus1cand the heat-load circuit90are similar to those according to the first embodiment.

A use heat exchanger13includes a heat-load flow path13cthrough which the water flowing through the heal-load circuit90passes, a first use flow path13athrough which the first refrigerant flowing through the first refrigerant circuit10passes, and a second use flow path13bthrough which the second refrigerant flowing through the second refrigerant circuit20passes. The water flowing through the heat-load flow path13cof the use heat exchanger13exchanges heat with the first refrigerant flowing through the first use flow path13aand/or the second refrigerant flowing through the second use flow path13b. As a result, the water is cooled during a cooling operation and is heated during a heating operation.

The first refrigerant circuit10includes a first compressor11, a first switching mechanism12, the use heat exchanger13shared with the heat-load circuit90and the second refrigerant circuit20, a first use expansion valve15, a second use expansion valve16, a third use expansion valve14, a heat-source heat exchanger17shared with the second refrigerant circuit20, and a first outdoor heat exchanger18. The first refrigerant circuit10is filled with the first refrigerant, which is a low-pressure refrigerant, as a refrigerant. The first refrigerant is a refrigerant having 1 MPa or less at 30° C., and is a refrigerant including, for example, at least one of R1234yf or R1234ze. The first refrigerant may include only R1234yf or may include only R1234ze.

The specific configuration of the first compressor11is similar to that according to the first embodiment. A discharge side and a suction side of the first compressor11are connected to different connection points of the first switching mechanism12.

The first switching mechanism12includes a switching valve12a, a switching valve12b, and a switching valve12c. The switching valve12a, the switching valve12b, and the switching valve12care connected in parallel to each other on the discharge side of the first compressor11. The switching valve12ais a three-way valve that switches between a state in which the discharge side of the first compressor11is connected to the first use flow path13aof the use heat exchanger13and a state in which the suction side of the first compressor11is connected to the first use flow path13aof the use heat exchanger13. The switching valve12bis a three-way valve that switches between a state in which the discharge side of the first compressor11is connected to the first outdoor heat exchanger18and a state in which the suction side of the first compressor11is connected to the first outdoor heat exchanger18. The switching valve12cis a three-way valve that switches between a state in which the discharge side of the first compressor11is connected to a first heat-source flow path17aof the heat-source heat exchanger17and a state in which the suction side of the first compressor11is connected to the first heat-source flow path17aof the heat-source heat exchanger17.

A gas refrigerant side of the first use flow path13aof the use heat exchanger13through which the first refrigerant flowing through the first refrigerant circuit10passes is connected to the switching valve12aof the first switching mechanism12. A liquid refrigerant side of the first use flow path13ais connected to a flow path extending from the third use expansion valve14. The first refrigerant evaporates when flowing through the first use flow path13aof the use heat exchanger13to cool the water flowing through the heat-load circuit90. The first refrigerant condenses when flowing through the first use flow path13aof the use heat exchanger13to heat the water flowing through the heat-load circuit90.

The third use expansion valve14includes an electronic expansion valve that is adjustable in valve opening degree. The third use expansion valve14is disposed between the use heat exchanger13and a first branch point A in the first refrigerant circuit10.

At the first branch point A, a flow path extending from the third use expansion valve14, a flow path extending from the first use expansion valve15, and a flow path extending to the side of the second use expansion valve16opposite to the first outdoor heat exchanger18side are connected.

The first use expansion valve15is similar to that according to the first embodiment.

The second use expansion valve16is similar to that according to the first embodiment.

The heat-source heat exchanger17is similar to that according to the first embodiment. An outlet on a gas refrigerant side of the first heat-source flow path17aof the heat-source heat exchanger17is connected to the switching valve12cof the first switching mechanism12. An inlet on a liquid refrigerant side of the first heat-source flow path17aof the heat-source heat exchanger17is connected to a flow path extending from the first use expansion valve15.

The first outdoor heat exchanger18is similar to that according to the first embodiment.

The outdoor fan9generates an air flow of outdoor air passing through both the first outdoor heat exchanger18and a second outdoor heat exchanger23.

The second refrigerant circuit20includes a second compressor21, a second switching mechanism22, the use heat exchanger13shared with the heat-load circuit90and the first refrigerant circuit10, the heat-source heat exchanger17shared with the first refrigerant circuit10, a first heat-source expansion valve26, a second heat-source expansion valve24, a third heat-source expansion valve25, and the second outdoor heat exchanger23. The second refrigerant circuit20is filled with the second refrigerant, which is a high-pressure refrigerant, as a refrigerant. The second refrigerant is a refrigerant having 1.5 MPa or more at 30° C. The second refrigerant may include carbon dioxide, or may include only carbon dioxide.

The specific configuration of the second compressor21is similar to that according to the first embodiment. A discharge side and a suction side of the second compressor21are connected to different connection points of the second switching mechanism22.

The second switching mechanism22includes a switching valve22a, a switching valve22b, and a switching valve22c. The switching valve22a, the switching valve22b, and the switching valve22care connected in parallel to each other on the discharge side of the second. compressor21. The switching valve22ais a three-way valve that switches between a state in which the discharge side of the second compressor21is connected to the second use flow path13bof the use heat exchanger13and a state in which the suction side of the second compressor21is connected to the second use flow path13bof the use heat exchanger13. The switching valve22bis a three-way valve that switches between a state in which the discharge side of the second compressor21is connected to the second outdoor heat exchanger23and a state in which the suction side of the second compressor21is connected to the second outdoor heat exchanger23. The switching valve22cis a three-way valve that switches between a state in which the discharge side of the second compressor21is connected to a second heart-source flow path17bof the heat-source heat exchanger17and a state in which the suction side of the second compressor21is connected to the second heat-source flow path17bof the heat-source heat exchanger17.

An inlet on a gas refrigerant side of the second heat-source flow path17bof the heat-source heat exchanger17is connected to the switching valve22cof the second switching mechanism22. An outlet on a liquid refrigerant side of the second heat-source flow path17bof the heat-source heat exchanger17is connected to a flow path extending from the third heat-source expansion valve25. The second refrigerant radiates heat when flowing through the second heat-source flow path17bof the heat-source heat exchanger17to evaporate the first refrigerant flowing through the first heat-source flow path17a.

At a second branch point B, a flow path extending from the third heat-source expansion valve25, a flow path extending from the first heat-source expansion valve26, and a flow path extending from the second heat-source expansion valve24are connected.

The first heat-source expansion valve26is disposed in a flow path between the second branch point B and an inlet on a liquid refrigerant side of the second outdoor heat exchanger23.

The second outdoor heat exchanger23is similar to that according to the first embodiment.

The second heat-source expansion valve24is disposed in a flow path between the second branch point B and an inlet on a liquid refrigerant side of the second use flow path13bof the use heat exchanger13.

The second use flow path13bof the use heat exchanger13through which the second refrigerant flowing through the second refrigerant circuit20passes is disposed in a flow path between the second heat-source expansion valves24and the switching valve22aof the second switching mechanism22. The second refrigerant evaporates when flowing through the second use flow path13bof the use heat exchanger13to cool the water flowing through the heat-load circuit90. The second refrigerant radiates heat when flowing through the second use flow path13bof the use heat exchanger13to heat the water flowing through the heat-load circuit90.

The controller7controls the operation of the devices included in the heat-load circuit90, the first refrigerant circuit10, and the second refrigerant circuit20. Specifically, the controller7includes a processor serving as a CPU provided for performing control, a memory, and the like.

In the refrigeration cycle apparatus1cdescribed above, the controller7controls the devices to execute a refrigeration cycle, thereby performing a cooling operation for processing a cooling load in the heat-load heat exchanger91and a heating operation for proscessing a heating load in the heat-load heat exchanger91.

(4-1) Cooling Operation

During the cooling operation, a first cooling operation, a second cooling operation, and a third cooling operation are selectively performed.

In the first cooling operation, as illustrated inFIG.15, the first refrigerant circuit10performs a refrigeration cycle such that the first outdoor heat exchanger18functions as a condenser of the first refrigerant and the use heat exchanger13functions as an evaporator of the first refrigerant, and the second refrigerant circuit20causes the second compressor21to stop operation. As a result, a single-stage refrigeration cycle is performed. Specifically, the switching valves12a,12b, and12cof the first switching mechanism12are switched to a connection state indicated by solid lines inFIG.15, the pump92, the first compressor11, and the outdoor fan9are driven, the second use expansion valve16is fully opened, the first use expansion valve15is controlled to be fully closed, and the valve opening degree of the third use expansion valve14is controlled such that the degree of superheating of the first refrigerant to be sucked into the first compressor11satisfies a predetermined condition.

Accordingly, the first refrigerant discharged from the first compressor11is sent to the first outdoor heat exchanger18via the switching valve12bof the first switching mechanism12. The first refrigerant sent to the first outdoor heat exchanger18is condensed by heat exchange with the outdoor air supplied by the outdoor fan9. The first refrigerant having passed through the first outdoor heat exchanger18passes through the second use expansion valve16and the first branch point A, is decompressed in the third use expansion valve14, and then flows into the use heat exchanger13. The first refrigerant flowing through the first use flow path13aof the use heat exchanger13is evaporated by heat exchange with the water flowing through the heal-load flow path13cof the use heat exchanger13included in the heat-load circuit90. The water cooled by this heat exchange is sent to the heat-load heat exchanger91in the heat-load circuit90to process the cooling load. The first refrigerant evaporated in the first use flow path13ais sucked into the first compressor11via the switching valve12aof the first switching mechanism12.

The second cooling operation is performed when the single-stage refrigeration cycle performed by the first refrigerant circuit10causes insufficient capacity because the required temperature of the heat medium flowing through the heat-load circuit90drops to a predetermined value or less to increase the cooling load. The second cooling operation is performed, in particular, in a refrigeration cycle apparatus in which the heat medium flowing through the heat-load circuit90is antifreeze, when the temperature required in the heat-load circuit90is low. In the second cooling operation, as illustrated inFIG.16, the first refrigerant circuit10performs a refrigeration cycle such that the first outdoor heat exchanger18functions as a condenser of the first refrigerant and the heat-source heat exchanger17functions as an evaporator of the first refrigerant, and the second refrigerant circuit20performs a refrigeration cycle such that the heat-source heat exchamzer17functions as a radiator of the second refrigerant and the use heat exchanger13functions as an evaporator of the second refrigerant. As a result, a two-stage refrigeration cycle is performed. Specifically, the switching valves12a,12b, and12cof the first switching mechanism12are switched to a connection state indicated by solid lines inFIG.16, the switching valves22a,22b, and22cof the second switching mechanism22are switched to a connection state indicated by solid lines inFIG.16, and the pump92, the first compressor11, the second compressor21, and the outdoor fan9are driven. Then, the second use expansion valve16is controlled to be fully opened, the third use expansion valve14is controlled to be fully closed, and the valve opening degree of the first use expansion valve15is controlled such that the degree of superheating of the first refrigerant to be sucked into the first compressor11satisfies a predetermined condition. Further, the first heat-source expansion valve26is controlled to be fully closed, the third heat-source expansion valve25is controlled to be fully opened, and the valve opening degree of the second heat-source expansion valve24is controlled such that the degree of superheating of the second refrigerant to be sucked into the second compressor21satisfies a predetermined condition.

Accordingly, the first refrigerant discharged from the first compressor11is sent to the first outdoor heat exchanger18via the switching valve12b of the first switching mechanism12. The first refrigerant sent to the first outdoor heat exchanger18is condensed by heat exchange with the outdoor air supplied by the outdoor fan9. The first refrigerant having passed through the first outdoor heat exchanger18passes through the second use expansion valve16, is decompressed in the first use expansion valve15, and then flows into the heat-source heat exchanger17. The first refrigerant flowing through the first heat-source flow path17aof the heat-source heat exchanger17is evaporated by heat exchange with the second refrigerant flowing through the second heat-source flow path17b. The first refrigerant evaporated in the heat-source heat exchanger17is sucked into the first compressor11via the switching valve12cof the first switching mechanism12. The second refrigerant discharged from the second compressor21is sent to the heat-source heat exchanger17via the switching valve22cof the second switching mechanism22. The second refrigerant flowing through the second heat-source flow path17bof the heat-source heat exchanger17radiates heat by heat exchange with the first refrigerant flowing through the first heal-source flow path17a. The second refrigerant having passed through the heat-source heat exchanger17passes through the third heat-source expansion valve25, is decompressed in the second heat-source expansion valve24, and then flows into the use heat exchanger13. The second refrigerant flowing through the second use flow path13bof the use heat exchanger13is evaporated by heat exchange with the antifreeze flowing through the heat-load flow path13cof the use heat exchanger13included in the heat-load circuit90. The antifreeze cooled by this heat exchange is sent to the heat-load heat exchanger91in the heat-load circuit90to process the cooling load. The second refrigerant evaporated in the use heat exchanger13is sucked into the second compressor21via the switching valve22aof the second switching mechanism22.

The third cooling operation is an operation performed when more emphasis is placed on the exercise of the capacity than the increase of the operation efficiency in a case where the temperature of the heat medium flowing through the heat-load circuit90is higher than a predetermined value and the cooling load is large. In the third cooling operation parallel refrigeration cycles are performed by the first refrigerant circuit10and the second refrigerant circuit20to exercise the capacity more than when the single-stage refrigeration cycle using the first refrigerant or the two-stage refrigeration cycle in which the first refrigerant is used in the heat-source-side refrigeration cycle in the higher stage and the second refrigerant is used in the use-side refrigeration cycle in the lower stage is performed. In the third cooling operation, as illustrated inFIG.17, the first refrigerant circuit10performs a refrigeration cycle such that the first outdoor heat exchanger18functions as a condenser of the first refrigerant and the use heat exchanger13functions as an evaporator of the first refrigerant, and the second refrigerant circuit20performs a refrigeration cycle such that the second outdoor heat exchanger23functions as a radiator of the second refrigerant and the use heat exchanger13functions as an evaporator of the second refrigerant. As a result, parallel refrigeration cycles are performed. Specifically, the switching valves12a,12b, and12cof the first switching mechanism12are switched to a connection state indicated by solid lines inFIG.17, the switching valves22a,22b, and22cof the second switching mechanism22are switched to a connection state indicated by solid lines inFIG.17, and the pump92, the first compressor11, the second compressor21, and the outdoor fan9are driven. Then, the second use expansion valve16is controlled to be fully opened, the first use expansion valve15is controlled to be fully closed, and the valve opening degree of the third use expansion valve14is controlled such that the degree of superheating of the first refrigerant to be sucked into the first compressor11satisfies a predetermined condition. Further, the first heal-source expansion valve26is controlled to be fully opened, the third heat-source expansion valve25is controlled to be fully closed, and the valve opening degree of the second heat-source expansion valve24is controlled such that the degree of superheating of the second refrigerant to be sucked into the second compressor21satisfies a predetermined condition.

Accordingly, the first refrigerant discharged from the first compressor11is sent to the first outdoor heat exchanger18via the switching valve12bof the first switching mechanism12. The first refrigerant sent to the first outdoor heat exchanger18is condensed by heat exchange with the outdoor air supplied by the outdoor fan9. The first refrigerant having passed through the first outdoor heat exchanger18passes through the second use expansion valve16, is decompressed in the third use expansion valve14, and then flows into the use heat exchanger13. The first refrigerant flowing through the first use flow path13aof the use heat exchanger13is evaporated by heat exchange with the water flowing through the heat-load flow path13cof the use heat exchanger13included in the heat-load circuit90. The first refrigerant evaporated in the use heat exchanger13is sucked into the first compressor11via the switching valve12aof the first switching mechanism12. The second refrigerant discharged from the second compressor21is sent to the second outdoor heat exchanger23via the switching valve22bof the second switching mechanism22. The second refrigerant sent to the second outdoor heat exchanger23radiates heat by heat exchange with the outdoor air supplied by the outdoor fan9. The second refrigerant having passed through the second outdoor heat exchanger23passes through the first heat-source expansion valve26, is decompressed in the second heat-source expansion valve24, and then flows into the use heat exchanger13. The second refrigerant flowing through the second use flow path13bof the use heat exchanger13is evaporated by heat exchange with the water flowing through the heat-load flow path13cof the use heat exchanger13included in the heat-load circuit90. The water cooled by exchanging heat with the two refrigerants, namely, the first refrigerant and the second refrigerant, in the way described above is sent to the heat-load heat exchanger91in the heat-load circuit90to process the cooling load. The second refrigerant evaporated in the use heat exchanger13is sucked into the second compressor21via the switching valve22aof the second switching mechanism22.

(4-2) Heating Operation

During the heating operation, a first heating operation, a second heating operation, and a third heating operation are selectively performed.

The first heating operation is performed when the outside air temperature is equal to or higher than a predetermined value.

In the first heating operation, as illustrated inFIG.18, the first refrigerant circuit10causes the use heat exchanger13to function as a condenser of the first refrigerant, and causes the first outdoor heat exchanger18to function as an evaporator of the first refrigerant, and the second refrigerant circuit20causes the second compressor21to stop operation. As a result, a single-stage refrigeration cycle is performed. Specifically, the switching valves12aand12bof the first switching mechanism12are switched to a connection state indicated by broken lines inFIG.18and the switching valve12care switched to a connection state indicated by, solid line inFIG.18, the pump92, the first compressor11, and the outdoor fan9are driven, the third use expansion valve14is fully opened, the first use expansion valve15is controlled to be fully closed, and the valve opening degree of the second use expansion valve16is controlled such that the degree of superheating of the first refrigerant to be sucked into the first compressor11satisfies a predetermined condition.

Accordingly, the first refrigerant discharged from the first compressor11is sent to the first use flow path13aof the use heat exchanger13via the switching valve12aof the first switching mechanism12. The first refrigerant flowing through the first use flow path13aof the use heat exchanger13is condensed by heat exchange with the water flowing through the heat-load flow path13cof the use heat exchanger13included in the heat-load circuit90. The water heated by this heat exchange is sent to the heat-load heat exchanger91in the heat-load circuit90to process the heating load. The first refrigerant condensed in the first use flow path13aof the use heat exchanger13passes through the third use expansion valve14and the first branch point A, is decompressed in the second use expansion valve16, and then flows into the first outdoor heat exchanger18. The first refrigerant sent to the first outdoor heat exchanger18is evaporated by heat exchange with the outdoor air supplied by the outdoor fan9. The first refrigerant evaporated in the first outdoor heat exchanger18is sucked into the first compressor11via the switching valve12bof the first switching mechanism12.

The second heating operation is an operation performed when the outside air temperature drops to a predetermined value or lower and the capacity is difficult to secure with the single-stage refrigeration cycle using the first refrigerant in the first refrigerant circuit10. In the second heating operation, as illustrated inFIG.19, the first refrigerant circuit10performs a refrigeration cycle such that the use heat exchanger13functions as a condenser of the first refrigerant and the heat-source heat exchanger17functions as an evaporator of the first refrigerant, and the second refrigerant circuit20performs a refrigeration cycle such that the heat-source heat exchanger17functions as a radiator of the second refrigerant and the second outdoor heat exchanger23functions as an evaporator of the second refrigerant. As a result, a two-stage refrigeration cycle is performed. Specifically, the switching valves12a,12b, and12cof the first switching mechanism12are switched to a connection state indicated by broken lines inFIG.19, the switching valves22a,22b, and22cof the second switching mechanism22are switched to a connection state indicated by solid lines inFIG.19, and the pump92, the first compressor11, the second compressor21, and the outdoor fan9are driven. Then, the second use expansion valve16is controlled to be fully closed, the third use expansion valve14is controlled to be fully opened, and the valve opening degree of the first use expansion valve15is controlled such that the degree of superheating of the first refrigerant to be sucked into the first compressor11satisfies a predetermined condition. Further, the second heat-source expansion valve24is controlled to be fully closed, the third heat-source expansion valve25is controlled to be fully opened, and the valve opening degree of the first heat-source expansion valve26is controlled such that the degree of superheating of the second refrigerant to be sucked into the second compressor21satisfies a predetermined condition.

Accordingly, the first refrigerant discharged from the first compressor11is sent to the use heat exchanger13via the switching valve12aof the first switching mechanism12. The first refrigerant flowing through the first use flow path13aof the use heat exchanger13is condensed by heat exchange with the water flowing through the heat-load flow path13cof the use heat exchanger13included in the heat-load circuit90. The water heated by this heat exchange is sent to the heat-load heat exchanger91in the heat-load circuit90to process the heating load. The first refrigerant having passed through the use heat exchanger13passes through the third use expansion valve14, is decompressed in the first use expansion valve15, and then flows into the heat-source heat exchanger17. The first refrigerant flowing through the first heat-source flow path17aof the heat-source heat exchanger17is evaporated by heat exchange with the second refrigerant flowing through the second heat-source flow path17b. The first refrigerant evaporated in the heat-source heat exchanger17is sucked into the first compressor11via the switching valve12cof the first switching mechanism12. The second refrigerant discharged from the second compressor21is sent to the heat-source heat exchanger17via the switching valve22cof the second switching mechanism22. The second refrigerant flowing through the second heat-source flow path17bof the heat-source heat exchanger17radiates heat by heat exchange with the first refrigerant flowing through the first heat-source flow path17a. The second refrigerant having passed through the heat-source heat exchanger17passes through the third heat-source expansion valve25, is decompressed in the first heat-source expansion valve26, and then flows into the second outdoor heat exchanger23. The second refrigerant sent to the second outdoor heat exchanger23is evaporated by heat exchange with the outdoor air supplied by the outdoor fan9. The second refrigerant evaporated in the second outdoor heat exchanger23is sucked into the second compressor21via the switching valve22bof the second switching mechanism22.

The third heating operation is an operation performed when more emphasis is placed on the exercise of the capacity than the increase of the operation efficiency in a case where the temperature of the heat medium flowing through the heat-load circuit90is lower than a predetermined value and the heating load is large. In the third heating operation, parallel refrigeration cycles are performed by the first refrigerant circuit10and the second refrigerant circuit20to exercise the capacity more than the single-stage refrigeration cycle using the first refrigerant and more than the two-stage refrigeration cycle in which the first refrigerant is used in the heat-source-side refrigeration cycle in the higher stage and the second refrigerant is used in the use-side refrigeration cycle in the lower stage. In the third heating operation, as illustrated inFIG.20, the first refrigerant circuit10performs a refrigeration cycle such that the use heat exchanger13functions as a condenser of the first refrigerant and the first outdoor heat exchanger18functions as an evaporator of the first refrigerant, and the second refrigerant circuit20performs a refrigeration cycle such that the use heat exchanger13functions as a radiator of the second refrigerant and the second outdoor heat exchanger23functions as an evaporator of the second refrigerant. As a result, parallel refrigeration cycles are performed. Specifically, the switching valves12a,12b, and12cof the first switching mechanism12are switched to a connection state indicated by broken lines inFIG.20, the switching valves22aand22cof the second switching mechanism22are switched to a connection state indicated by broken lines inFIG.20, the switching valve22bof the second switching mechanism22is switched to a connection state indicated by a solid line inFIG.20, and the pump92, the first compressor11, the second compressor21, and the outdoor fan9are driven. Then, the third use expansion valve14is controlled to be fully opened, the first use expansion valve15is controlled to be fully closed, and the valve opening degree of the second use expansion valve16is controlled such that the degree of superheating of the first refrigerant to be sucked into the first compressor11satisfies a predetermined condition. Further, the second heat-source expansion valve24is controlled to be fully opened, the third heat-source expansion valve25is controlled to be fully closed, and the valve opening degree of the first heat-source expansion valve26is controlled such that the degree of superheating of the second refrigerant to be sucked into the second compressor21satisfies a predetermined condition.

Accordingly, the first refrigerant discharged from the first compressor11is sent to the use heat exchanger13via the switching valve12aof the first switching mechanism12, and the first refrigerant flowing through the first use flow path13aof the use heat exchanger13is condensed by heat exchange with the water flowing through the heat-load flow path13cof the use heat exchanger13included in the heat-load circuit90. The first refrigerant having passed through the use heat exchanger13passes through the third use expansion valve14, is decompressed in the second use expansion valve16, and then flows into the first outdoor heat exchanger18. The first refrigerant sent to the first outdoor heat exchanger18is evaporated by heat exchange with the outdoor air supplied by the outdoor fan9. The first refrigerant evaporated in the first outdoor heat exchanger18is sucked into the first compressor11via the switching valve12bof the first switching mechanism12. The second refrigerant discharged from the second compressor21is sent to the use heat exchanger13via the switching valve22aof the second switching mechanism22. The second refrigerant flowing through the second use flow path13bof the use heat exchanger13radiates heat by heat exchange with the water flowing through the heat-load flow path13cof the use heat exchanger13included in the heat-load circuit90. The water heated by exchanging heat with the two refrigerants, namely, the first refrigerant and the second refrigerant, in the way described above is sent to the heat-load heat exchanger91in the heat-load circuit90to process the heating load. The second refrigerant having passed through the use heat exchanger13passes through the second heat-source expansion valve24, is decompressed in the first heat-source expansion valve26, and then flows into the second outdoor heat exchanger23. The second refrigerant sent to the second outdoor heat exchanger23is evaporated by heat exchange with the outdoor air supplied by the outdoor fan9. The second refrigerant evaporated in the second outdoor heat exchanger23is sucked into the second compressor21via the switching valve22bof the second switching mechanism22.

(4-3) Features of Fourth Embodiment

Like the refrigeration cycle apparatus1according to the first embodiment, the refrigeration cycle apparatus1caccording to the present embodiment can reduce global environmental deterioration, and can easily secure heating operation capacity. Further, in addition to the single-stage refrigeration cycle and the two-stage refrigeration cycle, the parallel refrigeration cycles can be performed in both of the cooling operation and the heating operation. Thus, the capacity can be secured according to the situation.

In the use heat exchanger, the first refrigerant may condense during the heating operation.

The use heat exchanger is preferably a heat exchanger that processes a heat load. The refrigerant flowing through the use heat exchanger may exchange heat with air, or may exchange heat with a fluid such as brine or water.

In the first outdoor heat exchanger, the first refrigerant may condense during the cooling operation.

The first outdoor heat exchanger is not limited. For example, the refrigerant flowing through the first outdoor heat exchanger may exchange heat with air.

The second outdoor heat exchanger is not limited. For example, the refrigerant flowing through the second outdoor heat exchanger may exchange heat with air.

The first refrigerant may condense when passing through the first use flow path during the heating operation.

In the first outdoor heat exchanger, the first refrigerant may condense during the cooling operation.

The first refrigerant may include only R1234yf or may include only R1234ze.

The second refrigerant may include only carbon dioxide.

Supplementary Note

While embodiments of the present disclosure have been described, it will be understood that various changes may be made in form and details without departing from the spirit and scope of the present disclosure as defined in the claims.

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