CN117157496A - Refrigeration cycle device - Google Patents

Abstract

Provided is a refrigeration cycle device which is provided with a first refrigerant circuit and a second refrigerant circuit and which can improve the operation efficiency. The refrigeration cycle device includes a first refrigerant circuit (10) using a first refrigerant at 30 ℃ of 1.2MPa or less and a second refrigerant circuit (20) using a second refrigerant at 30 ℃ of 1.5MPa or more, and is capable of switching and executing a binary cycle operation that simultaneously operates the first refrigerant circuit (10) and the second refrigerant circuit (20) so as to exchange heat between the first refrigerant and the second refrigerant, and a single cycle operation that does not operate the second refrigerant circuit (20) but operates the first refrigerant circuit (10) so as to perform a cooling operation or a heating operation.

Description

Refrigeration cycle device

Technical Field

The present disclosure relates to a refrigeration cycle apparatus.

Background

Conventionally, there is a binary refrigeration cycle apparatus in which two refrigerant circuits are operated separately and the refrigerants flowing in the respective refrigerant circuits are heat-exchanged with each other.

For example, in the refrigeration cycle apparatus described in patent document 1 (japanese patent application laid-open No. 2014-9829), there is proposed a two-stage refrigeration cycle including a heat-source-side refrigerant circuit and a usage-side refrigerant circuit thermally connected by a cascade heat exchanger, and in which both a heat-source-side compressor of the heat-source-side refrigerant circuit and a usage-side compressor of the usage-side refrigerant circuit are driven to efficiently perform the two-stage refrigeration cycle.

Disclosure of Invention

Technical problem to be solved by the invention

In the refrigeration cycle apparatus described above, it is desirable that the refrigeration cycle apparatus including the first refrigerant circuit and the second refrigerant circuit have different methods to improve the efficiency of operation.

Technical proposal adopted for solving the technical problems

The refrigeration cycle apparatus according to the first aspect includes a first refrigerant circuit that uses a first refrigerant and a second refrigerant circuit that uses a second refrigerant. The first refrigerant is 1.2MPa or less at 30 ℃. The second refrigerant is at least 1.5MPa at 30 ℃. The refrigeration cycle apparatus is capable of switching between and executing a binary cycle operation and a unitary cycle operation. The two-cycle operation causes the first refrigerant circuit and the second refrigerant circuit to operate simultaneously to exchange heat between the first refrigerant and the second refrigerant. The single circulation operation does not operate the second refrigerant circuit but operates the first refrigerant circuit to perform the cooling operation or the heating operation.

The refrigeration cycle apparatus may perform only either one of the cooling operation and the heating operation as the unitary circulation operation, or the refrigeration cycle apparatus may selectively perform both the cooling operation and the heating operation as the unitary circulation operation.

Further, the first refrigerant circuit and the second refrigerant circuit are independent refrigerant circuits, and the first refrigerant and the second refrigerant may not be mixed together.

In the case of performing the binary refrigeration cycle by the refrigeration cycle apparatus, the second refrigerant circuit side may be used as the heat source side, and the first refrigerant circuit side may be used as the use side. Specifically, the first refrigerant circuit may handle the heat load.

The heat load of air or fluid such as water or brine can be handled on the use side.

In the refrigeration cycle apparatus, by performing a binary refrigeration cycle including a refrigeration cycle in a first refrigerant circuit using a first refrigerant which is a low-pressure refrigerant of 1.2MPa or less at 30 ℃ and a refrigeration cycle in a second refrigerant circuit using a second refrigerant which is a high-pressure refrigerant of 1.5MPa or more at 30 ℃, the operation efficiency is good and the capacity can be easily ensured. In the refrigeration cycle apparatus, for example, when the heating load is small during the heating operation, the binary refrigeration cycle is not performed, and the heating operation is performed by operating the first refrigerant circuit without operating the second refrigerant circuit, so that it is possible to avoid a loss in heat exchange between the first refrigerant and the second refrigerant at the time of low load, and to suppress a decrease in operation efficiency.

The refrigeration cycle apparatus according to the second aspect is the refrigeration cycle apparatus according to the first aspect, wherein the second refrigerant flowing through the second refrigerant circuit heats the first refrigerant flowing through the first refrigerant circuit during the two-cycle operation, thereby performing the heating operation.

In addition, it is preferable that the heating operation is performed by the binary cycle operation when the heating load is larger than a predetermined heating load.

In the refrigeration cycle apparatus, the operation efficiency can be improved by performing the binary refrigeration cycle during the heating operation.

The refrigeration cycle apparatus according to the third aspect is the refrigeration cycle apparatus according to the first or second aspect, wherein the unitary circulation operation is performed when a predetermined low-load condition is satisfied.

In addition, it is preferable that the heating operation is performed by the unitary circulation operation when the heating load satisfies a predetermined low load condition.

In the refrigeration cycle apparatus, a decrease in the operation efficiency of the heating operation at the time of low load can be suppressed.

The refrigeration cycle apparatus according to a fourth aspect is the refrigeration cycle apparatus according to any one of the first to third aspects, further comprising a cascade heat exchanger. The cascade heat exchanger has a first cascade flow path for flowing a first refrigerant and a second cascade flow path independent of the first cascade flow path and for flowing a second refrigerant. The cascade heat exchanger exchanges heat between the first refrigerant and the second refrigerant during the two-cycle operation.

In the refrigeration cycle apparatus, the load can be handled by using the heat acquired from the second refrigerant circuit side by the first refrigerant circuit side during the binary refrigeration cycle operation.

A refrigeration cycle apparatus according to a fifth aspect is the refrigeration cycle apparatus according to the fourth aspect, wherein the first refrigerant circuit includes a first compressor, a first heat exchanger, a first expansion valve, and a first cascade flow path.

In the refrigeration cycle apparatus described above, the refrigeration cycle using the first refrigerant can be performed in the first refrigerant circuit by operating the first compressor.

The refrigeration cycle apparatus according to a sixth aspect is the refrigeration cycle apparatus according to the fifth aspect, wherein the second refrigerant circuit includes a second compressor, a second cascade flow path, a second expansion valve, and a second heat exchanger.

In the refrigeration cycle apparatus, the first compressor and the second compressor can be operated to perform a binary refrigeration cycle.

The refrigeration cycle apparatus according to a seventh aspect is the refrigeration cycle apparatus according to the sixth aspect, wherein the first cascade flow path is caused to function as an evaporator of the first refrigerant, the first heat exchanger is caused to function as a radiator of the first refrigerant, the second cascade flow path is caused to function as a radiator of the second refrigerant, and the second heat exchanger is caused to function as an evaporator of the second refrigerant during the binary cycle operation.

In the refrigeration cycle apparatus, the operation efficiency of the heating operation can be improved by performing the binary refrigeration cycle.

The refrigeration cycle apparatus according to the eighth aspect is the refrigeration cycle apparatus according to the seventh aspect, wherein the first refrigerant circuit further includes a third heat exchanger. The refrigeration cycle device can perform a cooling operation in which the third heat exchanger functions as a radiator of the first refrigerant and the first heat exchanger functions as an evaporator of the first refrigerant.

In the refrigeration cycle apparatus, the cooling operation can be performed by a single cycle.

The refrigeration cycle apparatus according to a ninth aspect is the refrigeration cycle apparatus according to the seventh aspect, wherein the first refrigerant circuit further includes a third heat exchanger. The refrigeration cycle device can perform a heating operation in which the third heat exchanger functions as an evaporator of the first refrigerant and the first heat exchanger functions as a radiator of the first refrigerant.

In the refrigeration cycle apparatus, the heating operation can be performed by a single cycle.

A refrigeration cycle apparatus according to a tenth aspect is the refrigeration cycle apparatus according to the seventh aspect, wherein the first refrigerant circuit further includes a third heat exchanger and a switching unit that switches a flow path of the first refrigerant. In the refrigeration cycle apparatus, by switching the switching unit, it is possible to perform a cooling operation in which the third heat exchanger functions as a radiator of the first refrigerant and the first heat exchanger functions as an evaporator of the first refrigerant, and a heating operation in which the third heat exchanger functions as an evaporator of the first refrigerant and the first heat exchanger functions as a radiator of the first refrigerant.

In the refrigeration cycle apparatus, the heating operation by the unitary refrigeration cycle and the heating operation by the binary refrigeration cycle can be switched and performed.

The refrigeration cycle apparatus according to the eleventh aspect is the refrigeration cycle apparatus according to any one of the eighth to tenth aspects, further comprising a first blower. The second heat exchanger exchanges heat between air flowing outside and a second refrigerant flowing inside. The third heat exchanger exchanges heat between air flowing outside and the first refrigerant flowing inside. The first air supply portion forms an air flow passing through the second heat exchanger and an air flow passing through the third heat exchanger.

In the refrigeration cycle apparatus, heat exchange can be performed in the second heat exchanger and the third heat exchanger using the air flow formed by the first air blowing portion.

A refrigeration cycle apparatus according to a twelfth aspect is the refrigeration cycle apparatus according to the eleventh aspect, wherein the second heat exchanger is disposed at a position other than downwind of the third heat exchanger in the air flow.

The second heat exchanger may be disposed on an upstream side of the third heat exchanger. The second heat exchanger may be arranged in a direction intersecting the air flow direction formed by the first air blowing unit, and may be arranged in parallel with the third heat exchanger. In the case where the first air blowing unit forms an upward air flow, the second heat exchanger and the third heat exchanger may be arranged in a circumferential direction on an upstream side of the air flow with respect to the first air blowing unit so as not to overlap each other in the air flow direction.

In the refrigeration cycle apparatus, the second refrigerant in the second heat exchanger can be suppressed from being warmed by the air passing through the third heat exchanger.

A refrigeration cycle apparatus according to a thirteenth aspect is the refrigeration cycle apparatus according to the eleventh or twelfth aspect, wherein the second heat exchanger and the third heat exchanger are disposed apart from each other in the air flow direction.

In the refrigeration cycle apparatus, the heat of the third heat exchanger itself can be suppressed from heating the second refrigerant in the second heat exchanger.

A refrigeration cycle apparatus according to a fourteenth aspect is the refrigeration cycle apparatus according to any one of the sixth to thirteenth aspects, wherein the second refrigerant circuit further includes a fourth heat exchanger provided between the discharge side of the second compressor and the second cascade flow path.

In the refrigeration cycle apparatus, the heating load on the use side can be handled by using the heat of the refrigerant flowing through the fourth heat exchanger.

A refrigeration cycle apparatus according to a fifteenth aspect is the refrigeration cycle apparatus according to the fourteenth aspect, further comprising a second blower. The first heat exchanger exchanges heat between air flowing outside and a first refrigerant flowing inside. The fourth heat exchanger exchanges heat between air flowing outside and the second refrigerant flowing inside. The second air supply portion forms an air flow passing through both the first heat exchanger and the fourth heat exchanger.

In the refrigeration cycle apparatus described above, the heat of the refrigerant in the first heat exchanger and the fourth heat exchanger can be used by the air flow formed by the second air blowing portion to treat the heating load.

The refrigeration cycle apparatus according to a sixteenth aspect is the refrigeration cycle apparatus according to any one of the first to fifteenth aspects, wherein the first refrigerant includes at least one of R1234yf, R1234ze, and R290.

The first refrigerant may be composed of only R1234yf, only R1234ze, or only R290.

In the refrigeration cycle apparatus, the operation can be performed using a refrigerant having a sufficiently low Global Warming Potential (GWP).

A refrigeration cycle apparatus according to a seventeenth aspect is the refrigeration cycle apparatus according to any one of the first to sixteenth aspects, wherein the second refrigerant contains carbon dioxide.

The second refrigerant may be composed of only carbon dioxide, or may be a mixed refrigerant of carbon dioxide and another refrigerant.

In the refrigeration cycle apparatus, the operation can be performed using a refrigerant having a sufficiently low ozone depletion potential (ODP: ozone Depletion Potential) and Global Warming Potential (GWP). In addition, during the cooling operation, by avoiding the binary refrigeration cycle in which the second refrigerant circuit through which the carbon dioxide-containing refrigerant flows is used as the heat source-side refrigerant circuit in the binary refrigeration cycle, and performing the unitary refrigeration cycle using the first refrigerant circuit, it is possible to avoid the decrease in COP caused by the carbon dioxide refrigerant reaching the supercritical state.

Drawings

Fig. 1 is an overall configuration diagram of a refrigeration cycle apparatus according to a first embodiment.

Fig. 2 is a functional block diagram of the refrigeration cycle apparatus according to the first embodiment.

Fig. 3 is a diagram showing a refrigerant flow pattern during the cooling operation of the first embodiment.

Fig. 4 is a diagram showing a refrigerant flow pattern during the high-load heating operation of the first embodiment.

Fig. 5 is a diagram showing a refrigerant flow pattern during the low-load heating operation of the first embodiment.

Fig. 6 is an overall configuration diagram of the refrigeration cycle apparatus according to the second embodiment.

Fig. 7 is an overall configuration diagram of the refrigeration cycle apparatus according to the third embodiment.

Fig. 8 is a schematic configuration diagram of a first outdoor heat exchanger and a second outdoor heat exchanger of the refrigeration cycle apparatus according to the fourth embodiment.

Fig. 9 is a schematic configuration diagram of a first outdoor heat exchanger and a second outdoor heat exchanger of the refrigeration cycle apparatus according to the fifth embodiment.

Fig. 10 is a schematic configuration diagram of a first outdoor heat exchanger and a second outdoor heat exchanger of the refrigeration cycle apparatus according to the sixth embodiment.

Fig. 11 is a schematic configuration diagram of a first outdoor heat exchanger and a second outdoor heat exchanger of the refrigeration cycle apparatus according to the seventh embodiment.

Detailed Description

(1) First embodiment

Fig. 1 is a schematic configuration diagram of a refrigeration cycle apparatus 1 according to a first embodiment. Fig. 2 is a functional block diagram showing the refrigeration cycle apparatus 1 according to the first embodiment.

The refrigeration cycle apparatus 1 is an apparatus for processing a heat load by performing a vapor compression refrigeration cycle operation. The refrigeration cycle apparatus 1 includes a heat load circuit 90, a first refrigerant circuit 10, a second refrigerant circuit 20, an outdoor fan 9, and a controller 7.

The heat load handled by the refrigeration cycle apparatus 1 is not particularly limited, and a fluid such as air, water, or brine may be subjected to heat exchange, and in the refrigeration cycle apparatus 1 of the present embodiment, water flowing through the heat load circuit 90 is supplied to the heat load heat exchanger 91, and the heat load in the heat load heat exchanger 91 is handled. The heat load circuit 90 is a circuit in which water as a heat medium circulates, and includes a heat load heat exchanger 91, a pump 92, and a use heat exchanger 13 (corresponding to a first heat exchanger) shared with the first refrigerant circuit 10. The pump 92 circulates water in the heat load circuit 90 by being driven and controlled by the controller 7 described later. In the heat load circuit 90, water flows through a heat load flow path 13b provided in the heat exchanger 13. The usage heat exchanger 13 has a usage flow path 13a through which the first refrigerant flowing through the first refrigerant circuit 10 passes, as will be described later. The water flowing through the heat load flow path 13b of the heat exchanger 13 is cooled during the cooling operation and warmed during the heating operation by heat exchange with the first refrigerant flowing through the use flow path 13a.

The first refrigerant circuit 10 includes a first compressor 11, a first switching mechanism 12, a use heat exchanger 13 (corresponding to a first heat exchanger) shared with the heat load circuit 90, a first use expansion valve 15 (corresponding to a first expansion valve), a second use expansion valve 16, a cascade heat exchanger 17 shared with the second refrigerant circuit 20, and a first outdoor heat exchanger 18. The low-pressure refrigerant, i.e., the first refrigerant, is filled in the first refrigerant circuit 10 as the refrigerant. The first refrigerant is a refrigerant of 1.2MPa or less at 30 ℃, and for example, is a refrigerant containing at least one of R1234yf, R1234ze, and R290, and may be composed of only R1234yf, only R1234ze, or only R290.

The first compressor 11 is a positive displacement compressor driven by a compressor motor. The compressor motor is driven by receiving power supplied from the inverter device. The first compressor 11 can change the operation capacity by changing the rotation speed of the compressor motor, that is, the driving frequency. The discharge side of the first compressor 11 is connected to a first switching mechanism 12. The suction side of the first compressor 11 is connected to the gas refrigerant side outlet of the first cascade flow path 17a of the cascade heat exchanger 17.

The first switching mechanism 12 has a switching valve 12a and a switching valve 12b. The switching valve 12a and the switching valve 12b are connected in parallel to each other on the discharge side of the first compressor 11. The switching valve 12a is a three-way valve that switches between a state in which the discharge side of the first compressor 11 is connected to the use flow path 13a of the use heat exchanger 13 and a state in which the suction side of the first compressor 11 is connected to the use flow path 13a of the use heat exchanger 13. The switching valve 12b is a three-way valve for switching between a state in which the discharge side of the first compressor 11 is connected to the first outdoor heat exchanger 18 and a state in which the suction side of the first compressor 11 is connected to the first outdoor heat exchanger 18.

The gas refrigerant side of the usage flow path 13a of the heat exchanger 13 through which the first refrigerant flowing through the first refrigerant circuit 10 passes is connected to the switching valve 12 a. The liquid refrigerant side of the flow path 13a is connected to the first branch point a of the first refrigerant circuit 10. The first refrigerant evaporates when flowing through the use flow path 13a of the use heat exchanger 13, thereby cooling the water flowing through the heat load circuit 90, and condenses when flowing through the use flow path 13a of the use heat exchanger 13, thereby heating the water flowing through the heat load circuit 90.

The first branch point a is connected to a flow path extending from the liquid refrigerant side of the usage flow path 13a, a flow path extending from the side opposite to the cascade heat exchanger 17 side of the first usage expansion valve 15, and a flow path extending from the second usage expansion valve 16 to the side opposite to the first outdoor heat exchanger 18 side.

The first expansion valve 15 is constituted by an electronic expansion valve capable of adjusting the valve opening. The first expansion valve 15 is provided in the first refrigerant circuit 10 between the first branch point a and the inlet, which is the liquid refrigerant side, of the first cascade flow path 17a of the cascade heat exchanger 17.

The second expansion valve 16 is constituted by an electronic expansion valve capable of adjusting the valve opening. The second expansion valve 16 is provided in the first refrigerant circuit 10 between the first branch point a and the outlet, which is the liquid refrigerant side, of the first outdoor heat exchanger 18.

The cascade heat exchanger 17 has a first cascade flow path 17a through which the first refrigerant flowing through the first refrigerant circuit 10 passes and a second cascade flow path 17b through which the second refrigerant flowing through the second refrigerant circuit 20 passes, and is a heat exchanger that exchanges heat between the first refrigerant and the second refrigerant. In the cascade heat exchanger 17, the first cascade flow path 17a and the second cascade flow path 17b are independent of each other, and the first refrigerant and the second refrigerant are not mixed together. The outlet, which is the gas refrigerant side of the first cascade flow path 17a of the cascade heat exchanger 17, is connected to the suction side of the first compressor 11. The first cascade heat exchanger 17 has a liquid refrigerant side inlet of the first cascade flow path 17a connected to the first expansion valve 15.

The first outdoor heat exchanger 18 is configured to have 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 exchanger 18 is disposed outdoors. The first refrigerant flowing in the first outdoor heat exchanger 18 functions as a condenser or an evaporator of the first refrigerant by exchanging heat with the air sent to the first outdoor heat exchanger 18.

The outdoor fan 9 generates an air flow of outdoor air passing through both the first and second outdoor heat exchangers 18 and 23.

The second refrigerant circuit 20 includes a second compressor 21, a cascade heat exchanger 17 shared with the first refrigerant circuit 10, a heat source expansion valve 26, and a second outdoor heat exchanger 23 (corresponding to a second heat exchanger). The second refrigerant, which is the high-pressure refrigerant, is filled in the second refrigerant circuit 20 as the refrigerant. The second refrigerant is a refrigerant of 1.5MPa or higher at 30 ℃, and may be, for example, a mixed refrigerant containing carbon dioxide, or may be composed of only carbon dioxide. The mixed refrigerant containing carbon dioxide may be, for example, a mixed refrigerant of carbon dioxide and R1234ze, or a mixed refrigerant of carbon dioxide and R1234 yf.

The second compressor 21 is a positive displacement compressor driven by a compressor motor. The compressor motor is driven by receiving power supplied from the inverter device. The second compressor 21 can change the operation capacity by changing the rotation speed of the compressor motor, that is, the driving frequency. The discharge side of the second compressor 21 is connected to the inlet, which is the gas refrigerant side, of the second cascade flow path 17b of the cascade heat exchanger 17. The suction side of the second compressor 21 is connected to a second outdoor heat exchanger 23.

The inlet, which is the gas refrigerant side of the second cascade flow path 17b of the cascade heat exchanger 17, is connected to the discharge side of the second compressor 21. The outlet, which is the liquid refrigerant side, of the second cascade flow path 17b of the cascade heat exchanger 17 is connected to the heat source expansion valve 26.

The heat source expansion valve 26 is provided in a flow path between the liquid refrigerant side of the second cascade flow path 17b of the cascade heat exchanger 17 and the liquid refrigerant side of the second outdoor heat exchanger 23.

The second outdoor heat exchanger 23 is configured to have 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 exchanger 23 and the first outdoor heat exchanger 18 are arranged outdoors. Specifically, the second outdoor heat exchanger 23 is disposed on the upwind side of the first outdoor heat exchanger 18, apart from the first outdoor heat exchanger 18 in the direction of the air flow formed by the outdoor fan 9. In this way, by disposing the second outdoor heat exchanger 23 and the first outdoor heat exchanger 18 separately from each other, heat transfer from the first outdoor heat exchanger 18 to the second outdoor heat exchanger 23 can be suppressed. Further, since the second outdoor heat exchanger 23 is not disposed on the leeward side of the first outdoor heat exchanger 18, the air warmed in the first outdoor heat exchanger 18 can be prevented from being sent to the second outdoor heat exchanger 23. This can suppress the carbon dioxide refrigerant in the second outdoor heat exchanger 23 from being heated by the heat of the first outdoor heat exchanger 18. The second refrigerant flowing in the second outdoor heat exchanger 23 functions as an evaporator of the second refrigerant by exchanging heat with the air sent to the second outdoor heat exchanger 23.

The controller 7 controls the operations of the respective devices constituting the heat load circuit 90, the first refrigerant circuit 10, and the second refrigerant circuit 20. Specifically, the controller 7 includes a processor such as a CPU and a memory such as a ROM and a RAM provided for control.

In the refrigeration cycle apparatus 1 described above, the controller 7 controls the respective devices to perform the refrigeration cycle, thereby performing the cooling operation for processing the cooling load in the heat load heat exchanger 91 and the heating operation for processing the heating load in the heat load heat exchanger 91. The heating operation includes a low-load heating operation performed when the heating load is small and a high-load heating operation performed when the heating load is large.

(1-1) cooling operation

In the cooling operation, as shown in fig. 3, the first refrigerant circuit 10 performs a unitary refrigeration cycle such that the heat exchanger 13 functions as an evaporator of the first refrigerant, the first outdoor heat exchanger 18 functions as a condenser of the first refrigerant, and the second refrigerant circuit 20 does not perform a refrigeration cycle. Specifically, the switching valves 12a and 12b of the first switching mechanism 12 are switched to the connected state shown by the solid lines in fig. 3, the pump 92, the first compressor 11, and the outdoor fan 9 are driven, the first utilization expansion valve 15 is set to the fully closed state, and the valve opening degree of the second utilization expansion valve 16 is controlled so that the degree of superheat of the first refrigerant sucked into the first compressor 11 satisfies a predetermined condition. Here, the rotation speed of the first compressor 11 is controlled so as to be able to cope with the cooling load of the heat load heat exchanger 91 in the heat load circuit 90. In the cooling operation, the second compressor 21 is stopped to stop the operation of the second refrigerant circuit 20.

Thereby, the first refrigerant discharged from the first compressor 11 is sent to the first outdoor heat exchanger 18 through the switching valve 12b of the first switching mechanism 12. The first refrigerant sent to the first outdoor heat exchanger 18 is condensed by heat exchange with outdoor air supplied by an outdoor fan. The first refrigerant passing through the first outdoor heat exchanger 18 is depressurized in the second usage expansion valve 16, and is sent to the usage flow path 13a of the usage heat exchanger 13 through the first branch point a. The first refrigerant flowing through the use flow path 13a of the use heat exchanger 13 evaporates by exchanging heat with water flowing through the heat load flow path 13b of the use heat exchanger 13 included in the heat load circuit 90. The water cooled by this heat exchange is sent to the heat load heat exchanger 91 in the heat load circuit 90 to process the refrigeration load. The first refrigerant evaporated in the use flow path 13a of the use heat exchanger 13 is sucked into the first compressor 11 through the switching valve 12a of the first switching mechanism 12.

(1-2) high load heating operation

When the heating operation is performed, the high-load heating operation is performed under the condition that the high-load condition of the heat load heat exchanger 91 of the heat load circuit 90, in which the heating load to be handled is large, is satisfied. The high load condition is not particularly limited, but a low load condition described later may not be satisfied.

In the high-load heating operation, as shown in fig. 4, the refrigeration cycle is performed in the first refrigerant circuit 10 such that the heat exchanger 13 functions as a condenser of the first refrigerant and the cascade heat exchanger 17 functions as an evaporator of the first refrigerant, and in the second refrigerant circuit 20 such that the cascade heat exchanger 17 functions as a radiator of the second refrigerant and the second outdoor heat exchanger 23 functions as an evaporator of the second refrigerant. In this way, during the high-load heating operation, the two-way refrigeration cycle is performed by the second refrigerant circuit 20 and the first refrigerant circuit 10. Specifically, the switching valves 12a and 12b of the first switching mechanism 12 are switched to the connected state shown by the broken lines in fig. 4, the pump 92, the first compressor 11, the second compressor 21, and the outdoor fan 9 are driven, the second use expansion valve 16 is set to the fully closed state, the valve opening degree of the first use expansion valve 15 is controlled so that the degree of superheat of the first refrigerant sucked into the first compressor 11 satisfies a predetermined condition, and the valve opening degree of the heat source expansion valve 26 is controlled so that the degree of superheat of the second refrigerant sucked into the second compressor 21 satisfies a predetermined condition. Further, the rotation speed of the first compressor 11 is controlled so as to be able to cope with the cooling load of the heat load heat exchanger 91 in the heat load circuit 90. The rotation speed of the second compressor 21 is controlled, for example, so that the degree of superheat of the first refrigerant passing through the first cascade flow path 17a in the cascade heat exchanger 17 and sucked into the first compressor 11 reaches a predetermined value, or so that the second refrigerant flowing through the second cascade flow path 17b in the cascade heat exchanger 17 reaches a predetermined pressure.

Thereby, the second refrigerant discharged from the second compressor 21 is sent to the cascade heat exchanger 17, and exchanges heat with the first refrigerant flowing through the first cascade flow path 17a to dissipate heat when flowing through the second cascade flow path 17 b. The second refrigerant having cooled in the cascade heat exchanger 17 is depressurized in the heat source expansion valve 26, then is heat-exchanged with outdoor air supplied from the outdoor fan in the second outdoor heat exchanger 23, evaporated, and sucked into the second compressor 21. The first refrigerant discharged from the first compressor 11 is sent to the usage flow path 13a of the usage heat exchanger 13 through the switching valve 12a of the first switching mechanism 12. The first refrigerant flowing through the use flow path 13a of the use heat exchanger 13 is condensed by heat exchange with water flowing through the heat load flow path 13b of the use heat exchanger 13 included in the heat load circuit 90. The water warmed by this heat exchange is sent to the heat load heat exchanger 91 in the heat load circuit 90 to treat the heating load. The first refrigerant condensed in the use flow path 13a of the use heat exchanger 13 is depressurized in the first use expansion valve 15 after passing through the first bifurcation point a. The refrigerant decompressed by the first utilization expansion valve 15 is evaporated by heat exchange with the second refrigerant flowing through the second cascade flow path 17b when passing through the first cascade flow path 17a of the cascade heat exchanger 17. The first refrigerant evaporated in the first cascade flow path 17a of the cascade heat exchanger 17 is sucked into the first compressor 11.

(1-3) Low load heating operation

When the heating operation is performed, the low-load heating operation is performed under the condition that the low-load condition of the heat load heat exchanger 91 of the heat load circuit 90, in which the heating load to be handled is small, is satisfied.

The low-high load condition is not particularly limited, but may be a condition that the heating load in the heat load heat exchanger 91 of the heat load circuit 90 can handle even if the compression ratio of the first compressor 11 is equal to or smaller than a predetermined compression ratio. The prescribed compression ratio here is the following compression ratio of the first compressor 11: the degree of reduction in the operation efficiency in the refrigeration cycle apparatus 1 caused by the heat exchange loss in the cascade heat exchanger 17 at the time of the heating operation of the binary refrigeration cycle in the refrigeration cycle apparatus 1 is made greater than the degree of reduction in the operation efficiency in the refrigeration cycle apparatus 1 at the time of changing the process of the heating load achieved by the heating operation of the binary refrigeration cycle in which both the first refrigerant circuit 10 and the second refrigerant circuit 20 are operated to the process of the heating load achieved by the heating operation of the unitary refrigeration cycle in which only the first refrigerant 10 is operated. The predetermined compression ratio here may be, for example, the following compression ratio of the first compressor 11: the coefficient of performance (COP: coefficient of Performance) of the refrigeration cycle apparatus 1 in which the heating load is handled by the unitary refrigeration cycle in which only the first refrigerant circuit 10 is operated is made larger than the coefficient of performance (COP) of the refrigeration cycle apparatus in which the heating load is handled by the binary refrigeration cycle in which both the first refrigerant circuit 10 and the second refrigerant circuit 20 are operated.

The low-high load condition is not limited to the condition based on the predetermined compression ratio, and may be, for example, a condition in which the temperature of the fluid required in the heat load heat exchanger 91 of the heat load circuit 90 is equal to or higher than a predetermined value, or a condition in which the difference between the temperature of the fluid required in the heat load heat exchanger 91 of the heat load circuit 90 and the outside air temperature is equal to or higher than a predetermined value, or the predetermined values may be predetermined based on the predetermined compression ratio. The threshold value for determining the low-high load condition may be predetermined and held by a memory or the like of the controller 7.

In the low-load heating operation, as shown in fig. 5, in the first refrigerant circuit 10, the refrigeration cycle is performed so that the heat exchanger 13 functions as a condenser of the first refrigerant, the first refrigerant is not sent to the cascade heat exchanger 17, the first outdoor heat exchanger 18 functions as an evaporator of the first refrigerant, and the operation of the second refrigerant 20 is stopped. Thus, during the low-load heating operation, the single refrigeration cycle is performed by the first refrigeration circuit 10. Specifically, the switching valves 12a and 12b of the first switching mechanism 12 are switched to the connected state shown by the broken lines in fig. 5, the pump 92, the first compressor 11, and the outdoor fan 9 are driven, the first utilization expansion valve 15 is set to the fully closed state, and the valve opening degree of the second utilization expansion valve 16 is controlled so that the degree of superheat of the first refrigerant sucked into the first compressor 11 satisfies a predetermined condition. The rotation speed of the first compressor 11 is controlled so as to be able to cope with the heating load of the heat load heat exchanger 91 in the heat load circuit 90. In addition, in the low-load heating operation, the second compressor 21 is stopped to stop the operation of the second refrigerant circuit 20.

Thereby, the first refrigerant discharged from the first compressor 11 is sent to the usage flow path 13a of the usage heat exchanger 13 through the switching valve 12a of the first switching mechanism 12. The first refrigerant flowing through the use flow path 13a of the use heat exchanger 13 is condensed by heat exchange with water flowing through the heat load flow path 13b of the use heat exchanger 13 included in the heat load circuit 90. The water warmed by this heat exchange is sent to the heat load heat exchanger 91 in the heat load circuit 90 to treat the heating load. The first refrigerant condensed in the use flow path 13a of the use heat exchanger 13 is depressurized in the second use expansion valve 16 whose opening degree is controlled without flowing through the first use expansion valve 15 in the fully closed state after passing through the first bifurcation point a. The refrigerant decompressed in the second utilization expansion valve 16 is evaporated by heat exchange with the air in the air flow formed by the outdoor fan 9 when passing through the first outdoor heat exchanger 18. The first refrigerant evaporated in the first outdoor heat exchanger 18 is sucked into the first compressor 11.

(1-4) features of the first embodiment

In the refrigeration cycle device 1 of the first embodiment, a first refrigerant having a sufficiently low Global Warming Potential (GWP) is used in the first refrigerant circuit 10. In addition, a second refrigerant having a sufficiently low Ozone Depletion Potential (ODP) is used in the second refrigerant circuit 20. Therefore, deterioration of the global environment can be suppressed.

Further, even in the case where the first refrigerant having a sufficiently low Global Warming Potential (GWP) is used in the first refrigerant circuit 10, the heating load can be handled by performing the high-load heating operation when the heating load is large. Specifically, in the high-load heating operation, by performing the binary refrigeration cycle in which the second refrigerant circuit 20 is a heat source side cycle and the first refrigerant circuit 10 is a use side cycle, the capacity in the heating operation can be easily ensured as compared with the case of performing the unitary refrigeration cycle in which the first refrigerant is a low-pressure refrigerant.

In the refrigeration cycle apparatus 1 according to the present embodiment, the first refrigerant circuit 10 uses not the second refrigerant of 1.5MPa or more at 30 ℃ but the first refrigerant of 1.2MPa or less at 30 ℃. Therefore, the density of the first refrigerant sucked by the first compressor 1 of the first refrigerant circuit 10 is increased, so that the efficiency of the first compressor 11 can be improved. Further, the capacity of the first compressor 11 can be reduced.

In the refrigeration cycle apparatus 1 according to the present embodiment, the first refrigerant circuit 10 includes the first outdoor heat exchanger 18 connected in parallel with the cascade heat exchanger 17. Therefore, even in the case where the first refrigerant and the second refrigerant in the cascade heat exchanger 17 do not exchange heat due to the second refrigerant circuit being in the operation-stopped state, the first refrigerant can exchange heat with air in the first outdoor heat exchanger 18. Thus, the first refrigerant circuit 10 can perform the refrigeration cycle even when the second refrigerant circuit 20 is in the operation stopped state. Specifically, in the refrigeration cycle apparatus 1 of the present embodiment, even when the second refrigerant circuit 20 is in the operation-stopped state, the low-load heating operation by the unitary refrigeration cycle can be performed by operating the first refrigerant circuit 10.

When the heating load is small, the low-load heating operation, which is a unitary refrigeration cycle using only the first refrigerant circuit 10, is performed without performing the binary refrigeration cycle. Accordingly, not only the heating load can be handled while the compression ratio of the first compressor 11 is kept small, but also the reduction in the operation efficiency in the refrigeration cycle apparatus 1 can be kept small by suppressing the loss when the first refrigerant and the second refrigerant in the cascade heat exchanger 17 exchange heat.

Although carbon dioxide is used as the second refrigerant in the second refrigerant circuit 20, the refrigeration cycle is not performed in the second refrigerant circuit 20, but the unitary refrigeration cycle is performed by the first refrigerant circuit 10 during the cooling operation. This makes it possible to avoid a decrease in the operation efficiency due to the pressure of the carbon dioxide refrigerant exceeding the critical pressure, as in the case of performing the unitary refrigeration cycle using the carbon dioxide refrigerant as the high-pressure refrigerant or the case of performing the binary refrigeration cycle using the carbon dioxide as the high-pressure refrigerant in the heat source side cycle, and perform the cooling operation. The second refrigerant circuit 20 is used only as a heat source side refrigeration cycle in the binary refrigeration cycle at the time of the high-load heating operation. Therefore, the standard of the compressive strength required for the element components of the second refrigerant circuit 20 using carbon dioxide, which is a high-pressure refrigerant, can be reduced, and the device can be manufactured at low cost.

In the refrigeration cycle apparatus 1 according to the present embodiment, the second outdoor heat exchanger 23 in which the carbon dioxide refrigerant is present is disposed on the upstream side of the first outdoor heat exchanger 18 in the air flow direction of the outdoor fan 9. Therefore, the air warmed by heat exchange with the first refrigerant flowing through the first outdoor heat exchanger 18 can be prevented from being sent to the second outdoor heat exchanger 23. In this way, in a state in which the second refrigerant circuit 20 is stopped as in the low-load heating operation, the pressure rise of the carbon dioxide refrigerant in the second outdoor heat exchanger 23 due to the warmed air being sent to the second outdoor heat exchanger 23 is suppressed. In particular, when the second refrigerant circuit 20 is configured using an element component having a low compressive strength, the pressure rise of the carbon dioxide refrigerant in the second outdoor heat exchanger 23 is likely to be a significant problem, but even in the second refrigerant circuit 20 having a low compressive strength, the air warmed in the refrigeration cycle apparatus 1 of the present embodiment is not sent to the second outdoor heat exchanger 23, and therefore, the occurrence of such a problem can be suppressed.

In the refrigeration cycle apparatus 1 according to the present embodiment, the second outdoor heat exchanger 23 and the first outdoor heat exchanger 18 use the common outdoor fan 9, and thus the fans can be shared. As described above, even when the outdoor fan 9 is shared, in the refrigeration cycle apparatus 1 of the present embodiment, the second outdoor heat exchanger 23 and the first outdoor heat exchanger 18 are disposed apart from each other. Therefore, in a state where the second refrigerant circuit 20 is stopped as in the low-load heating operation, the heat transfer from the first outdoor heat exchanger 18 to the second outdoor heat exchanger 23 is suppressed, and therefore, the pressure rise of the carbon dioxide refrigerant in the second outdoor heat exchanger 23 is suppressed.

(2) Second embodiment

In the refrigeration cycle apparatus 1 according to the first embodiment, the case where the refrigeration cycle apparatus 1 includes the heat load circuit 90 and the use heat exchanger 13 includes the use flow path 13a and the heat load flow path 13b is described as an example.

In this regard, the refrigeration cycle apparatus 1 may not include the heat load circuit 90, and the load to be handled by the refrigeration cycle apparatus 1 may be an air load.

Fig. 6 is a schematic configuration diagram of a refrigeration cycle apparatus 1a according to a second embodiment.

The refrigeration cycle apparatus 1a of the second embodiment includes, for example, a heat load fan 92a that forms an air flow, instead of the pump 92 of the heat load circuit 90 of the above embodiment. The heat load fan 92a is driven and controlled by the controller 7 when the first refrigerant circuit 10 is driven.

The heat exchanger 13 of the refrigeration cycle apparatus 1a according to the second embodiment is used, for example, to cool or warm air in a space such as a room of a building. Specifically, in the use heat exchanger 13, the heat of the first refrigerant and the air is exchanged by the heat load fan 82a carrying the air in the space to be air-conditioned.

In the above configuration, the same effects as those of the first embodiment can be achieved.

(3) Third embodiment

In the second embodiment, the refrigeration cycle apparatus 1a including the heat load fan 92a and processing the heat load of the space to be air-conditioned is described as an example.

In contrast, as the refrigeration cycle apparatus, for example, a refrigeration cycle apparatus 1b dedicated to heating may be used in which the first and second heat exchangers 131 and 132 are used to perform the process of heating the load of the space to be air-conditioned.

Fig. 7 is a schematic configuration diagram of a refrigeration cycle apparatus 1b according to a third embodiment.

The refrigeration cycle apparatus 1b according to the third embodiment is an air heat exchanger in which the first refrigerant flowing inside and the air flowing outside are heat-exchanged by the first heat exchanger 131 of the first refrigerant circuit 10, and the first switching structure 12 is not provided. Therefore, the first usage heat exchanger 131 functions as a radiator of the first refrigerant discharged from the first compressor 11.

The second refrigerant circuit 20 of the refrigeration cycle apparatus 1b according to the third embodiment includes a second usage heat exchanger 132 between the second compressor 21 and the second cascade flow path 17b of the cascade heat exchanger 17. The second use heat exchanger 132 is an air heat exchanger that exchanges heat between the second refrigerant flowing inside and the air flowing outside, and is disposed apart from the first use heat exchanger 131 on the upstream side in the air flow direction generated by the heat load fan 92a of the first use heat exchanger 131. The second usage heat exchanger 132 functions as a radiator of the second refrigerant discharged from the second compressor 21.

In the refrigeration cycle apparatus 1b described above, as the low-load heating operation, the unitary refrigeration cycle operation using only the first refrigerant circuit 10 is performed. In the low-load heating operation, the first utilization expansion valve 15 is controlled to be in the fully closed state. In the low-load heating operation, the refrigerant discharged from the first compressor 11 is controlled to be condensed in the first use heat exchanger 131, decompressed in the second use expansion valve 16, evaporated in the first outdoor heat exchanger 18, and returned to the first compressor 11.

In addition, the refrigeration cycle apparatus 1b performs a binary refrigeration cycle using the first refrigerant circuit 10 and the second refrigerant circuit 20 during the high-load heating operation. In the high-load heating operation, the second utilization expansion valve 16 is controlled to be in the fully closed state in the first refrigerant circuit 10. In the high-load heating operation, the first refrigerant discharged from the first compressor 11 is controlled to condense in the first use heat exchanger 131, depressurized in the first use expansion valve 15, evaporated while flowing through the first cascade flow path 17a of the cascade heat exchanger 17, and returned to the first compressor 11. In the high-load heating operation, the second refrigerant discharged from the second compressor 21 in the second refrigerant circuit 20 is controlled to dissipate heat when passing through the second usage heat exchanger 132, and the second refrigerant is further cooled by heat exchange with the first refrigerant flowing through the first cascade flow path 17a when flowing through the second cascade flow path 17b of the cascade heat exchanger 17, depressurized in the heat source expansion valve 26, evaporated in the second outdoor heat exchanger 23, and returned to the second compressor 21.

The refrigeration cycle apparatus 1b according to the third embodiment is capable of suppressing a decrease in the operation efficiency to a small extent while processing the heating load by switching and operating according to the magnitude of the heating load, as in the first embodiment. In the refrigeration cycle apparatus 1b, the first heat exchanger 131 of the first refrigerant circuit 10 is included, and the second refrigerant circuit 20 also includes the second heat exchanger 132, and the heat exchangers functioning as heat sinks are included in the respective cycles, so that the heating capacity can be improved. Here, the second use heat exchanger 132 is disposed on the upstream side of the first use heat exchanger 131 in the air flow direction generated by the heat load fan 92 a. Accordingly, even when the second refrigerant circuit 20 is in a stopped state and the single refrigeration cycle is performed only in the first refrigerant circuit 10, the air heated when passing through the first use heat exchanger 131 is not sent to the second use heat exchanger 132. Further, the first and second utilization heat exchangers 131 and 132 are disposed apart from each other. Therefore, the carbon dioxide refrigerant inside the second usage heat exchanger 132 is suppressed from being heated when the second refrigerant circuit 20 is stopped, and an excessive increase in the pressure inside the second refrigerant circuit 20 is suppressed. Thereby, the second refrigerant circuit 20 can be designed as a circuit having a small compressive strength.

(4) Fourth embodiment

In the above embodiments, the refrigeration cycle apparatus in which the first outdoor heat exchanger 18 and the second outdoor heat exchanger 23 are disposed separately from each other has been described as an example.

In contrast, in the refrigeration cycle apparatus, the first outdoor heat exchanger 18 and the second outdoor heat exchanger 23 may be configured as an integrated heat exchanger, for example, as shown in fig. 8. Examples of the integrated heat exchanger include a heat exchanger having a plurality of first heat transfer tubes that constitute the first outdoor heat exchanger 18 and through which the first refrigerant flows, a plurality of second heat transfer tubes that constitute the second outdoor heat exchanger 23 and through which the second refrigerant flows, and a plurality of heat transfer fins fixed to both the first heat transfer tubes and the second heat transfer tubes. With the above-described configuration, the device can be easily manufactured.

(5) Fifth embodiment

In the above embodiments, the refrigeration cycle apparatus in which the heat exchange area of the first and second outdoor heat exchangers 18 and 23 when viewed in the air flow direction is arbitrary was described as an example.

In contrast, in the refrigeration cycle apparatus, as shown in fig. 9, for example, the first outdoor heat exchanger 18 and the second outdoor heat exchanger 23 may be configured such that the first outdoor heat exchanger 18 and the second outdoor heat exchanger 23 have overlapping portions when viewed in the air flow direction generated by the outdoor fan 9, and the heat exchange area of the first outdoor heat exchanger 18 is smaller than the heat exchange area of the second outdoor heat exchanger 23 when viewed in the air flow direction.

Accordingly, the ventilation resistance of the air in the first outdoor heat exchanger 18 can be suppressed to be small, and therefore, more air can easily pass through the second outdoor heat exchanger 23. This makes it easy to secure the evaporation capacity of the second refrigerant in the second outdoor heat exchanger 23 during the high-load heating operation, and to handle the high heating load. In particular, the present invention is effective as a refrigeration cycle apparatus having a higher heating capacity than a refrigeration capacity.

In addition, in the case where the first outdoor heat exchanger 18 and the second outdoor heat exchanger 23 are configured as an integrated heat exchanger as described in the fourth embodiment, in particular, the larger the ventilation resistance of the first outdoor heat exchanger 18, the smaller the amount of air passing through the second outdoor heat exchanger 23 tends to be. In this case, in particular, the effect of reducing the heat exchange area of the first outdoor heat exchanger 18 as described above can be significantly obtained.

(6) Sixth embodiment

In the above embodiments, the refrigeration cycle apparatus in which the first outdoor heat exchanger 18 and the second outdoor heat exchanger 23 are arranged to overlap each other when viewed in the air flow direction of the outdoor fan 9 has been described as an example.

In contrast, in the refrigeration cycle apparatus, as shown in fig. 10, for example, the first outdoor heat exchanger 18 and the second outdoor heat exchanger 23 may be disposed on the upstream side of the outdoor fan 9 in the air flow formed by the outdoor fan 9, and may be disposed at different positions around the rotation axis when viewed in the rotation axis direction of the outdoor fan 9. Here, in fig. 10, the rotation axis direction of the outdoor fan 9 is a direction perpendicular to the paper surface. In the top-blowing refrigeration cycle apparatus in which the outdoor fan 9 sucks in air from below and blows the air upward, for example, the first and second outdoor heat exchangers 18 and 23 may be arranged.

In this case, the air passing through the first outdoor heat exchanger 18 is not sent to the second outdoor heat exchanger 23, and therefore, the carbon dioxide refrigerant of the second outdoor heat exchanger 23 can be suppressed from being heated when the second refrigerant circuit 20 is stopped.

(7) Seventh embodiment

In the above embodiments, the refrigeration cycle apparatus in which the first outdoor heat exchanger 18 and the second outdoor heat exchanger 23 are arranged to overlap each other when viewed in the air flow direction of the outdoor fan 9 has been described as an example.

In contrast, in the refrigeration cycle apparatus, the first outdoor heat exchanger 18 and the second outdoor heat exchanger 23 may be arranged so that the first outdoor heat exchanger 18 and the second outdoor heat exchanger 23 do not overlap each other when viewed in the air flow direction, as shown in fig. 11, for example.

In this case, for example, the second outdoor heat exchanger 23 may be disposed above the first outdoor heat exchanger 18.

(additionally remembered)

While the embodiments of the present disclosure have been described above, it should be understood that various changes in form and detail may be made therein without departing from the spirit and scope of the present disclosure as set forth in the following claims.

Symbol description

1. 1a, 1b refrigeration cycle apparatus;

9 an outdoor fan (first air supply unit);

10 a first refrigerant circuit;

11 a first compressor;

12 a first switching mechanism (switching section);

13 using a heat exchanger (first heat exchanger);

13a use a flow path;

13b a heat load flow path;

15 first utilization expansion valve (first expansion valve);

a second utilization expansion valve 16;

17 cascade heat exchangers;

17a first cascade flow path;

17b a second cascade flow path;

18 a first outdoor heat exchanger (third heat exchanger);

a second refrigerant circuit 20;

a second compressor 21;

23 a second outdoor heat exchanger (second heat exchanger);

26 a heat source expansion valve (second expansion valve);

a 90 thermal load loop;

91 a heat load heat exchanger;

92 pumps;

92a heat load fan (second air supply unit);

131 first utilization heat exchanger (first heat exchanger);

132 a second utilization heat exchanger (fourth heat exchanger);

prior art literature

Patent literature

Patent document 1: japanese patent laid-open publication No. 2014-9829

Claims (17)

1. A refrigeration cycle apparatus (1, 1a, 1 b), comprising:

a first refrigerant circuit (10), wherein the first refrigerant circuit (10) uses a first refrigerant of 1.2MPa or less at 30 ℃; and

a second refrigerant circuit (20), wherein the second refrigerant circuit (20) uses a second refrigerant of 1.5MPa or more at 30 ℃,

the refrigerating cycle apparatus is capable of switching and executing a binary cycle operation and a unitary cycle operation,

in the two-cycle operation, the first refrigerant circuit and the second refrigerant circuit are operated simultaneously to exchange heat between the first refrigerant and the second refrigerant,

In the single-cycle operation, the first refrigerant circuit is operated to perform a cooling operation or a heating operation without operating the second refrigerant circuit.

2. A refrigeration cycle apparatus according to claim 1, wherein,

in the two-cycle operation, the second refrigerant flowing through the second refrigerant circuit heats the first refrigerant flowing through the first refrigerant circuit, and the heating operation is performed.

3. A refrigeration cycle apparatus according to claim 1 or 2, wherein,

the monobasic circulation operation is performed when a predetermined low load condition is satisfied.

4. A refrigeration cycle device according to any one of claim 1 to 3,

the refrigeration cycle apparatus includes a cascade heat exchanger (17), the cascade heat exchanger (17) having a first cascade flow path (17 a) for flowing the first refrigerant, and a second cascade flow path (17 b) independent of the first cascade flow path for flowing the second refrigerant, the cascade heat exchanger (17) heat-exchanging the first refrigerant and the second refrigerant at the time of the binary cycle operation.

5. A refrigeration cycle apparatus according to claim 4, wherein,

the first refrigerant circuit has a first compressor (11), a first heat exchanger (13, 131), a first expansion valve (15), and the first cascade flow path (17 a).

6. A refrigeration cycle apparatus according to claim 5, wherein,

the second refrigerant circuit has a second compressor (21), the second cascade flow path (17 b), a second expansion valve (26), and a second heat exchanger (23).

7. A refrigeration cycle apparatus according to claim 6, wherein,

in the two-cycle operation, the refrigeration cycle apparatus causes the first cascade flow path to function as an evaporator of the first refrigerant, causes the first heat exchanger to function as a radiator of the first refrigerant, causes the second cascade flow path to function as a radiator of the second refrigerant, and causes the second heat exchanger to function as an evaporator of the second refrigerant.

8. A refrigeration cycle apparatus according to claim 7, wherein,

the first refrigerant circuit also has a third heat exchanger (18),

the refrigeration cycle device is capable of performing the cooling operation in which the third heat exchanger is caused to function as a radiator of the first refrigerant and the first heat exchanger is caused to function as an evaporator of the first refrigerant.

9. A refrigeration cycle apparatus according to claim 7, wherein,

the first refrigerant circuit also has a third heat exchanger (18),

the refrigeration cycle device is capable of performing the heating operation in which the third heat exchanger is caused to function as an evaporator of the first refrigerant and the first heat exchanger is caused to function as a radiator of the first refrigerant.

10. A refrigeration cycle apparatus according to claim 7, wherein,

the first refrigerant circuit further includes a third heat exchanger (18) and a switching unit (12) for switching a flow path of the first refrigerant,

the refrigeration cycle apparatus is capable of executing the cooling operation in which the third heat exchanger is caused to function as a radiator of the first refrigerant and the first heat exchanger is caused to function as an evaporator of the first refrigerant, and the heating operation in which the third heat exchanger is caused to function as an evaporator of the first refrigerant and the first heat exchanger is caused to function as a radiator of the first refrigerant by switching the switching unit.

11. A refrigeration cycle device according to any one of claims 8 to 10, wherein,

the second heat exchanger exchanges heat between air flowing outside and the second refrigerant flowing inside,

the third heat exchanger exchanges heat between air flowing outside and the first refrigerant flowing inside,

the refrigeration cycle apparatus further includes a first air blowing portion (9), and the first air blowing portion (9) forms an air flow passing through the second heat exchanger and an air flow passing through the third heat exchanger.

12. A refrigeration cycle apparatus according to claim 11, wherein,

the second heat exchanger is disposed in the air stream at a position other than downwind of the third heat exchanger.

13. A refrigeration cycle apparatus according to claim 11 or 12, wherein,

the second heat exchanger and the third heat exchanger are disposed apart in the air flow direction.

14. A refrigeration cycle device according to any one of claims 6 to 13, wherein,

the second refrigerant circuit further has a fourth heat exchanger (132), the fourth heat exchanger (132) being disposed between the discharge side of the second compressor and the second cascade flow path.

15. A refrigeration cycle apparatus according to claim 14, wherein,

the first heat exchanger exchanges heat between air flowing outside and the first refrigerant flowing inside,

the fourth heat exchanger exchanges heat between air flowing outside and the second refrigerant flowing inside,

the refrigeration cycle apparatus further includes a second air blowing unit (92 a), and the second air blowing unit (92 a) forms an air flow passing through both the first heat exchanger and the fourth heat exchanger.

16. A refrigeration cycle device according to any one of claims 1 to 15, wherein,

the first refrigerant comprises at least one of R1234yf, R1234ze, and R290.

17. A refrigeration cycle device according to any one of claims 1 to 16,

the second refrigerant comprises carbon dioxide.