Refrigeration cycle device

Abstract

A first switching mechanism (15) can switch between a first state in which a discharge side of a first compressor (11) is connected to a first water heat exchanger (14) or a refrigerant heat exchanger (30), and a second state in which the discharge side of the first compressor (11) is connected to a heat source heat exchanger (12). In a defrosting operation for defrosting the heat source heat exchanger (12), a control unit (100) drives a first refrigerant circuit (10) in a state in which the first switching mechanism (15) is in the second state.

Description

Refrigeration cycle device

[0001] The present disclosure relates to a refrigeration cycle device.

[0002] Patent Document 1 discloses a refrigeration cycle device including a high-pressure side refrigerant circuit and a low-pressure side refrigerant circuit. The high-pressure side refrigerant circuit has a high-pressure side compressor, a six-way valve, a high-pressure side refrigerant heat exchanger, a high-pressure side expansion valve, a cascade heat exchanger, and a first heat medium heat exchanger, and circulates the high-pressure side refrigerant. The low-pressure side refrigerant circuit has a low-pressure side compressor, a four-way valve, a cascade heat exchanger, a low-pressure side expansion valve, and a second heat medium heat exchanger, and circulates the low-pressure side refrigerant.

[0003] International Publication No. 2021 / 106084

[0004] In a refrigeration cycle device as described above, from the viewpoint of eliminating the reduction in capacity due to frosting of the heat source heat exchanger, it is desirable to perform a defrost operation for defrosting the heat source heat exchanger.

[0005] A first aspect of the present disclosure relates to a refrigeration cycle device, the refrigeration cycle device comprising: a first refrigerant circuit (10) through which a first refrigerant circulates; a second refrigerant circuit (20) through which a second refrigerant circulates; a refrigerant heat exchanger (30) for heat exchange between the first refrigerant in the first refrigerant circuit (10) and the second refrigerant in the second refrigerant circuit (20); a water circuit (40) through which water circulates; and a control unit (100) for controlling the first refrigerant circuit (10) and the second refrigerant circuit (20), wherein the first refrigerant circuit (10) comprises a first compressor (11), a heat source heat exchanger (12), a first expansion valve (13), a first water heat exchanger (14), and a first switching mechanism (15); and the second refrigerant circuit (20) comprises a second compressor (21), a second water heat exchanger (22), and a second expansion valve (23). The first water heat exchanger (14) exchanges heat between the first refrigerant of the first refrigerant circuit (10) and the water of the water circuit (40). The second water heat exchanger (22) exchanges heat between the second refrigerant of the second refrigerant circuit (20) and the water of the water circuit (40). The first switching mechanism (15) is switchable between a first state in which the discharge side of the first compressor (11) is connected to the first water heat exchanger (14) or the refrigerant heat exchanger (30), and a second state in which the discharge side of the first compressor (11) is connected to the heat source heat exchanger (12). The control unit (100) drives the first refrigerant circuit (10) in a state where the first switching mechanism (15) is in the second state during a defrost operation to defrost the heat source heat exchanger (12).

[0006] In the first embodiment, during defrost operation, the first refrigerant circuit (10) is driven when the first switching mechanism (15) is in the second state, thereby supplying the high-temperature, high-pressure first refrigerant discharged from the first compressor (11) to the heat source heat exchanger (12). This allows the heat source heat exchanger (12) to be defrosted.

[0007] A second aspect of the present disclosure is a refrigeration cycle apparatus according to the first aspect, wherein the first refrigerant circuit (10) includes a gas flow path (61) connected to the gas side of the first water heat exchanger (14), a liquid flow path (62) connected to the liquid side of the first water heat exchanger (14), a connecting flow path (63) connecting the gas flow path (61) and the liquid flow path (62), and a second switching mechanism (60), wherein the second switching mechanism (60) is switchable between a third state in which the first refrigerant flows through the first water heat exchanger (14) without flowing through the connecting flow path (63), and a fourth state in which the first refrigerant flows through the connecting flow path (63) without flowing through the first water heat exchanger (14).

[0008] In the second embodiment, the system can be switched between operating with the first refrigerant flowing through the first water heat exchanger (14) and operating without the first refrigerant flowing through the first water heat exchanger (14). This improves the flexibility of operation of the refrigeration cycle device (1).

[0009] A third aspect of the present disclosure is a refrigeration cycle apparatus according to the second aspect, wherein the control unit (100) drives the first refrigerant circuit (10) such that, in the defrost operation, the heat source heat exchanger (12) becomes a heat radiator and the refrigerant heat exchanger (30) in the first refrigerant circuit (10) becomes a heat absorber.

[0010] In the third embodiment, during defrosting operation, the heat obtained in the refrigerant heat exchanger (30) can be used to defrost the heat source heat exchanger (12). This makes it possible to accelerate the defrosting of the heat source heat exchanger (12).

[0011] A fourth aspect of the present disclosure is a refrigeration cycle apparatus of the third aspect, wherein the defrost operation includes a first operation, and the control unit (100) drives the first refrigerant circuit (10) in the first operation with the second switching mechanism (60) in the fourth state.

[0012] In the fourth embodiment, the first refrigerant can be prevented from flowing into the first water heat exchanger (14) during the first operation. This makes it possible to suppress the temperature drop of the water in the water circuit (40) more than when the first refrigerant flows into the first water heat exchanger (14) and the first water heat exchanger (14) functions as a heat absorber.

[0013] A fifth aspect of the present disclosure is a refrigeration cycle apparatus according to the fourth aspect, wherein the defrost operation includes a first operation and a second operation performed after the completion of the first operation, and the control unit (100) drives the first refrigerant circuit (10) in the second operation with the second switching mechanism (60) switched from the fourth state to the third state.

[0014] In the fifth embodiment, the first water heat exchanger (14) can be made to function as a heat absorber during the second operation. This allows the heat obtained in the first water heat exchanger (14) to be used for defrosting the heat source heat exchanger (12) during the second operation, thereby accelerating the defrosting of the heat source heat exchanger (12) compared to when only the first operation is performed during defrosting.

[0015] A sixth aspect of the present disclosure is a refrigeration cycle apparatus according to the fifth aspect, wherein the water circuit (40) has a pump (41), and the control unit (100) drives the pump (41) in the second operation.

[0016] In the sixth embodiment, during the second operation, the pump (41) is driven to prevent the water in the water circuit (40) from stagnating in the first water heat exchanger (14). This makes it possible to suppress the temperature drop of the water in the water circuit (40) in the first water heat exchanger (14).

[0017] A seventh aspect of the present disclosure is a refrigeration cycle apparatus according to the sixth aspect, wherein the control unit (100) drives the pump (41) in the first operation.

[0018] In the seventh embodiment, the pump (41) is driven during the first operation, which is performed before the second operation, so that the water in the water circuit (40) does not stagnate in the first water heat exchanger (14) before the start of the second operation. This makes it easier to suppress the temperature drop of the water in the water circuit (40) in the first water heat exchanger (14) during the second operation.

[0019] An eighth aspect of the present disclosure is a refrigeration cycle apparatus of the fourth aspect, wherein the defrost operation includes a first operation and a second operation performed after the completion of the first operation, and the control unit (100) drives the first refrigerant circuit (10) in the second operation with the second switching mechanism (60) in the fourth state, and drives the second refrigerant circuit (20) such that the second refrigerant flows sequentially through the second compressor (21), the second water heat exchanger (22), the second expansion valve (23), and the refrigerant heat exchanger (30), and the opening of the second expansion valve (23) in the second operation is greater than the opening of the second expansion valve (23) in the heating operation where the second water heat exchanger (22) is a heat radiator and the refrigerant heat exchanger (30) in the second refrigerant circuit (20) is a heat absorber.

[0020] In the eighth aspect, the second refrigerant circuit (20) is driven with the opening of the second expansion valve (23) in the second operation being greater than the opening of the second expansion valve (23) in the heating operation. This allows the high-temperature, high-pressure second refrigerant discharged from the second compressor (21) to be dissipated to the first refrigerant in the first refrigerant circuit (10) in the refrigerant heat exchanger (30) during the second operation. As a result, the heat obtained in the refrigerant heat exchanger (30) (heat from the second refrigerant discharged from the second compressor (21)) can be used for defrosting the heat source heat exchanger (12) during the second operation, thereby accelerating the defrosting of the heat source heat exchanger (12).

[0021] A ninth aspect of the present disclosure is a refrigeration cycle apparatus according to the eighth aspect, wherein the control unit (100) drives the second refrigerant circuit (20) such that the second compressor (21) is driven intermittently during the second operation.

[0022] In the ninth aspect, during the second operation, the second compressor (21) is driven intermittently to prevent the temperature of the second refrigerant discharged from the second compressor (21) from becoming too high. This makes it possible to suppress the occurrence of high-temperature abnormalities (abnormalities in which the temperature of the second refrigerant exceeds the allowable temperature) in the second refrigerant circuit (20).

[0023] A tenth aspect of the present disclosure is a refrigeration cycle apparatus according to the eighth or ninth aspect, wherein the water circuit (40) has a pump (41), and the control unit (100) stops the pump (41) in the second operation.

[0024] In the tenth embodiment, in the second operation, the pump (41) can be stopped to prevent water in the water circuit (40) from flowing through the first water heat exchanger (14) and the second water heat exchanger (22). This suppresses heat dissipation from the second refrigerant in the second refrigerant circuit (20) to the water in the water circuit (40) in the second water heat exchanger (22), thereby allowing the heat of the second refrigerant discharged from the second compressor (21) to be effectively utilized for defrosting the heat source heat exchanger (12).

[0025] An eleventh aspect of the present disclosure is a refrigeration cycle apparatus according to the fourth aspect, wherein the second refrigerant circuit (20) has a third switching mechanism (24), the third switching mechanism (24) is switchable between a fifth state in which the discharge side of the second compressor (21) is connected to the second water heat exchanger (22), and a sixth state in which the discharge side of the second compressor (21) is connected to the refrigerant heat exchanger (30), and the control unit (100) drives the second refrigerant circuit (20) in the sixth state during the first operation.

[0026] In the eleventh embodiment, during the first operation, the high-temperature, high-pressure second refrigerant discharged from the second compressor (21) can be dissipated into the first refrigerant in the first refrigerant circuit (10) via the refrigerant heat exchanger (30). This allows the heat obtained in the refrigerant heat exchanger (30) (heat from the second refrigerant discharged from the second compressor (21)) to be used for defrosting the heat source heat exchanger (12) during the second operation, thereby accelerating the defrosting of the heat source heat exchanger (12).

[0027] A twelfth aspect of the present disclosure is a refrigeration cycle device according to a second aspect, wherein the second switching mechanism (60) includes a first valve (64) provided in the connecting passage (63) and a second valve (65) provided in the liquid passage (62) between the connection point between the connecting passage (63) and the liquid passage (62) and the liquid side of the first water heat exchanger (14), and the second valve (65) is an electrically operated valve.

[0028] In the twelfth embodiment, the amount of the first refrigerant flowing through the first water heat exchanger (14) can be controlled by making the second valve (65) of the second switching mechanism (60) an electric valve. This improves the degree of freedom in controlling the first water heat exchanger (14).

[0029] A thirteenth aspect of the present disclosure is a refrigeration cycle apparatus of the twelfth aspect, wherein the control unit (100) drives the first refrigerant circuit (10) such that in the defrost operation the first expansion valve (13) is open and the first valve (64) is closed, and the first refrigerant flows sequentially through the first compressor (11), the heat source heat exchanger (12), the first expansion valve (13), the refrigerant heat exchanger (30), the second valve (65), and the first water heat exchanger (14), and the opening of the first expansion valve (13) in the defrost operation is greater than the opening of the second valve (65) in the defrost operation.

[0030] In the 13th embodiment, during defrost operation, the heat source heat exchanger (12) and the refrigerant heat exchanger (30) in the first refrigerant circuit (10) can be made to function as radiators, and the first water heat exchanger (14) can be made to function as a heat absorber. This makes it possible to increase the degree of subcooling of the first refrigerant in the refrigerant heat exchanger (30), thereby improving the COP (Coefficient of Performance) during defrost operation.

[0031] A fourteenth aspect of the present disclosure is a refrigeration cycle apparatus according to the thirteenth aspect, wherein the water circuit (40) has a pump (41), and the control unit (100) drives the second refrigerant circuit (20) and the pump (41) so that the second refrigerant flows sequentially through the second compressor (21), the second water heat exchanger (22), the second expansion valve (23), and the refrigerant heat exchanger (30) during the defrost operation.

[0032] In the 14th embodiment, during defrost operation, the second refrigerant circuit (20) can be driven so that the second water heat exchanger (22) acts as a heat radiator and the refrigerant heat exchanger (30) in the second refrigerant circuit (20) acts as a heat absorber. This allows the water in the water circuit (40) to be heated in the second water heat exchanger (22) and promotes the subcooling of the first refrigerant in the refrigerant heat exchanger (30). Furthermore, during defrost operation, by driving the pump (41), the water in the water circuit (40) can be prevented from stagnating in the first water heat exchanger (14) and the second water heat exchanger (22), and the water heated in the second water heat exchanger (22) can be circulated back into the water circuit (40). This suppresses the temperature drop of the water in the water circuit (40).

[0033] Figure 1 is a piping diagram illustrating the configuration of a refrigeration cycle device according to Embodiment 1. Figure 2 is a block diagram illustrating the connections of each part in the refrigeration cycle device according to Embodiment 1. Figure 3 is a piping diagram illustrating the flow of refrigerant during heating operation. Figure 4 is a piping diagram illustrating the flow of refrigerant during the first operation included in the defrost operation of Embodiment 1. Figure 5 is a piping diagram illustrating the flow of refrigerant during the second operation included in the defrost operation of Embodiment 1. Figure 6 is a flowchart illustrating the operation switching during defrost operation. Figure 7 is a piping diagram illustrating the flow of refrigerant during the second operation included in the defrost operation of Embodiment 2. Figure 8 is a piping diagram illustrating the configuration of a refrigeration cycle device and the flow of refrigerant during defrost operation according to Embodiment 3. Figure 9 is a piping diagram illustrating the configuration of a refrigeration cycle device and the flow of refrigerant during defrost operation according to Embodiment 4.

[0034] The embodiments will be described in detail below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated. Furthermore, this disclosure is not limited to the embodiments shown below, and various modifications are possible without departing from the technical idea of ​​this disclosure. Since the drawings are for conceptual explanation of this disclosure, dimensions, ratios, or numbers may be exaggerated or simplified as necessary for ease of understanding.

[0035] (Embodiment 1) Figure 1 illustrates the configuration of a refrigeration cycle device (1) according to Embodiment 1. In this example, the refrigeration cycle device (1) constitutes a hot water supply device that generates hot water. The hot water generated by the hot water supply device is stored in a hot water storage tank (not shown) and supplied to a predetermined target. The refrigeration cycle device (1) also includes an outdoor unit (OU) installed outside and an indoor unit (IU) installed inside.

[0036] As shown in Figure 1, the refrigeration cycle device (1) comprises a first refrigerant circuit (10), a second refrigerant circuit (20), a refrigerant heat exchanger (30), and a water circuit (40). The first refrigerant circuit (10) is filled with a first refrigerant and circulates through it. The second refrigerant circuit (20) is filled with a second refrigerant different from the first refrigerant and circulates through it. In this example, the first refrigerant is carbon dioxide and the second refrigerant is propane (R290).

[0037] The refrigeration cycle device (1) performs a dual-stage refrigeration cycle. Specifically, a first refrigerant circuit (10) on the lower end and a second refrigerant circuit (20) on the higher end are connected via a refrigerant heat exchanger (30). In this example, the refrigerant heat exchanger (30) has a first flow path (30a) through which the first refrigerant of the first refrigerant circuit (10) flows, and a second flow path (30b) through which the second refrigerant of the second refrigerant circuit (20) flows. In other words, the first refrigerant circuit (10) has the first flow path (30a) of the refrigerant heat exchanger (30), and the second refrigerant circuit (20) has the second flow path (30b) of the refrigerant heat exchanger (30). The refrigerant heat exchanger (30) will be described in detail later.

[0038] [First Refrigerant Circuit] The first refrigerant circuit (10) performs a refrigeration cycle using the first refrigerant. In this example, the first refrigerant circuit (10) includes a first compressor (11), a heat source heat exchanger (12), a first expansion valve (13), a first water heat exchanger (14), a first four-way switching valve (15), and a receiver (16). The first refrigerant circuit (10) also includes a bridge circuit (50), a gas flow path (61), a liquid flow path (62), a connecting flow path (63), and a bypass mechanism (60). Near the heat source heat exchanger (12), an outdoor fan (17) is provided to transport outdoor air (an example of heat source air) to the heat source heat exchanger (12) so that the outdoor air passes through the heat source heat exchanger (12). The outdoor fan (17) is an example of a heat source fan that transports heat source air to the heat source heat exchanger (12).

[0039] The first compressor (11), the heat source heat exchanger (12), the first expansion valve (13), the first four-way switching valve (15), the receiver (16), and the bridge circuit (50) are installed in the outdoor unit (OU). The first water heat exchanger (14) and the bypass mechanism (60) are installed in the indoor unit (IU).

[0040] The first compressor (11) compresses the inhaled refrigerant and discharges the compressed refrigerant. For example, the first compressor (11) is a high-pressure dome type compressor.

[0041] The heat source heat exchanger (12) functions as a radiator or an evaporator (heat absorber). In this example, the heat source heat exchanger (12) is composed of an air heat exchanger that exchanges heat between "outdoor air conveyed to the heat source heat exchanger (12) by the outdoor fan (17)" and "the first refrigerant flowing through the heat source heat exchanger (12)".

[0042] The first expansion valve (13) is an example of a pressure reducing mechanism for reducing the pressure of the first refrigerant. In this example, the first expansion valve (13) is composed of an electric valve with adjustable opening degree.

[0043] The first water heat exchanger (14) exchanges heat between the first refrigerant in the first refrigerant circuit (10) and the water in the water circuit (40). In this example, the first water heat exchanger (14) is composed of a plate type heat exchanger. Specifically, the first water heat exchanger (14) has a first flow path (14a) through which the first refrigerant in the first refrigerant circuit (10) flows and a second flow path (14b) through which the water in the water circuit (40) flows, and exchanges heat between the first refrigerant in the first flow path (14a) and the water in the second flow path (14b). The first water heat exchanger (14) functions as a radiator or an evaporator.

[0044] The first four-way switching valve (15) has a first port (P1), a second port (P2), a third port (P3), and a fourth port (P4). The first four-way switching valve (15) can be switched between a first state in which the first port (P1) and the second port (P2) communicate with each other and the third port (P3) and the fourth port (P4) communicate with each other, and a second state in which the first port (P1) and the third port (P3) communicate with each other and the second port (P2) and the fourth port (P4) communicate with each other.

[0045] In this example, in the first four-way switching valve (15), the first port (P1) is connected to the discharge side of the first compressor (11), and the second port (P2) is connected to the gas side of the first water heat exchanger (14) via the gas flow path (61). The third port (P3) is connected to the gas side of the heat source heat exchanger (12), and the fourth port (P4) is connected to the suction side of the first compressor (11). Also, the first flow path (30a) of the refrigerant heat exchanger (30) is connected to the liquid side of the first water heat exchanger (14) via the liquid flow path (62).

[0046] Note that the first four-way switching valve (15) is an example of the first switching mechanism. The first switching mechanism can be switched between a first state in which the discharge side of the first compressor (11) is connected to the first water heat exchanger (14) or the refrigerant heat exchanger (30), and a second state in which the discharge side of the first compressor (11) is connected to the heat source heat exchanger (12).

[0047] The receiver (16) stores the first refrigerant and separates the first refrigerant into a gas refrigerant and a liquid refrigerant. For example, the receiver (16) is constituted by a pressure vessel.

[0048] The bridge circuit (50) has a first pipe (51), a second pipe (52), a third pipe (53), a fourth pipe (54), and four check valves (CV). The four check valves (CV) are arranged one-to-one in the above four pipes (the first to fourth pipes (51 to 54)). The check valve (CV) allows the flow of the refrigerant in the direction indicated by the arrow in FIG. 1 and prohibits the flow of the refrigerant in the opposite direction.

[0049] The outflow end of the first pipe (51) and the outflow end of the second pipe (52) are connected to the inflow side of the receiver (16). The inflow end of the third pipe (53) and the inflow end of the fourth pipe (54) are connected to the outflow side of the receiver (16). The inflow end of the first pipe (51) and the outflow end of the third pipe (53) are connected to the liquid side of the heat source heat exchanger (12). The inflow end of the second pipe (52) and the outflow end of the fourth pipe (54) are connected to the first flow path (30a) of the refrigerant heat exchanger (30).

[0050] In this example, a first expansion valve (13) is located on the outlet side of the receiver (16). The first refrigerant that flows out from the receiver (16) flows through the first expansion valve (13) and then enters the heat source heat exchanger (12) or the refrigerant heat exchanger (30) via the bridge circuit (50). In other words, the first expansion valve (13) is located between the receiver (16) and the heat source heat exchanger (12) and the refrigerant heat exchanger (30). Specifically, in the heating operation described later, the first expansion valve (13) is located between the receiver (16) and the heat source heat exchanger (12), and in the defrost operation described later, the first expansion valve (13) is located between the receiver (16) and the refrigerant heat exchanger (30).

[0051] The gas passage (61) is connected to the gas side of the first water heat exchanger (14). In this example, one end of the gas passage (61) is connected to the gas side of the first water heat exchanger (14). The other end of the gas passage (61) is connected to the second port (P2) of the first four-way switching valve (15).

[0052] The liquid channel (62) is connected to the liquid side of the first water heat exchanger (14). In this example, one end of the liquid channel (62) is connected to the liquid side of the first water heat exchanger (14). The other end of the liquid channel (62) is connected to the first channel (30a) of the refrigerant heat exchanger (30).

[0053] The connecting channel (63) connects the gas channel (61) and the liquid channel (62). In this example, one end of the connecting channel (63) is connected to the gas channel (61) which connects the gas side of the first water heat exchanger (14) to the second port (P2) of the first four-way switching valve (15). The other end of the connecting channel (63) is connected to the liquid channel (62) which connects the liquid side of the first water heat exchanger (14) to the first channel (30a) of the refrigerant heat exchanger (30).

[0054] The bypass mechanism (60) is switchable between a third state in which the first refrigerant flows through the first water heat exchanger (14) without flowing through the connecting channel (63), and a fourth state in which the first refrigerant flows through the connecting channel (63) without flowing through the first water heat exchanger (14). The bypass mechanism (60) is an example of a second switching mechanism.

[0055] In this example, the bypass mechanism (60) has a first valve (64) and a second valve (65). The first valve (64) is provided in the connecting passage (63). The second valve (65) is provided in the liquid passage (62) between the connection point between the liquid passage (62) and the connecting passage (63) and the liquid side of the first water heat exchanger (14). In this example, the first valve (64) and the second valve (65) are configured as switchable on / off valves (e.g., solenoid valves).

[0056] [Second Refrigerant Circuit] The second refrigerant circuit (20) performs a refrigeration cycle using the second refrigerant. In this example, the second refrigerant circuit (20) includes a second compressor (21), a second water heat exchanger (22), and a second expansion valve (23). The second refrigerant circuit (20) is installed in the indoor unit (IU).

[0057] In this example, propane, a highly flammable refrigerant, is used as the refrigerant to fill the second refrigerant circuit (20). Highly flammable refrigerants have the potential to ignite. For example, according to IEC60335-2-40 Ed.7, if propane is used as the refrigerant to fill the second refrigerant circuit (20) and the second refrigerant circuit (20) is installed indoors, if the amount of refrigerant exceeds 152g, the floor area of ​​the equipment installation room (the room in which the second refrigerant circuit (20) is installed) will be limited, and safety measures in case of leakage will need to be taken. In this embodiment, since the second refrigerant circuit (20) is installed in an indoor unit (IU), the amount of refrigerant to fill the second refrigerant circuit (20) is limited. For this reason, the amount of refrigerant to fill the second refrigerant circuit (20) is less than the amount of refrigerant to fill the first refrigerant circuit (10). For example, the amount of refrigerant to fill the first refrigerant circuit (10) is 15 times or more and 25 times or less than the amount of refrigerant to fill the second refrigerant circuit (20). Furthermore, for example, if the refrigerant charge amount of the second refrigerant circuit (20) is 152g or less, the refrigerant charge amount of the first refrigerant circuit (10) is 2500g or more and 3500g or less.

[0058] The second compressor (21) compresses the inhaled refrigerant and discharges the compressed refrigerant. For example, the second compressor (21) is a high-pressure dome-type compressor.

[0059] The second water heat exchanger (22) exchanges heat between the second refrigerant in the second refrigerant circuit (20) and the water in the water circuit (40). In this example, the second water heat exchanger (22) is composed of a plate-type heat exchanger. Specifically, the second water heat exchanger (22) has a first flow path (22a) through which the second refrigerant in the second refrigerant circuit (20) flows, and a second flow path (22b) through which the water in the water circuit (40) flows, and exchanges heat between the second refrigerant in the first flow path (22a) and the water in the second flow path (22b). The second water heat exchanger (22) functions as a radiator or evaporator.

[0060] The second expansion valve (23) is an example of a pressure reduction mechanism for reducing the pressure of the second refrigerant. In this example, the second expansion valve (23) is comprised of an electrically operated valve whose opening degree can be adjusted.

[0061] In this example, the discharge side of the second compressor (21) is connected to the first flow path (22a) of the second water heat exchanger (22), and the suction side of the second compressor (21) is connected to the second flow path (30b) of the refrigerant heat exchanger (30). The first flow path (22a) of the second water heat exchanger (22) is connected to the second flow path (30b) of the refrigerant heat exchanger (30) via the second expansion valve (23).

[0062] [Refrigerant Heat Exchanger] The refrigerant heat exchanger (30) exchanges heat between the first refrigerant of the first refrigerant circuit (10) and the second refrigerant of the second refrigerant circuit (20). In this example, the refrigerant heat exchanger (30) is composed of a plate-type heat exchanger. Specifically, the refrigerant heat exchanger (30) has a first flow path (30a) through which the first refrigerant of the first refrigerant of the first refrigerant circuit (10) flows, and a second flow path (30b) through which the second refrigerant of the second refrigerant of the second refrigerant circuit (20) flows, and exchanges heat between the first refrigerant of the first flow path (30a) and the second refrigerant of the second flow path (30b).

[0063] Furthermore, the refrigerant heat exchanger (30) functions as either a heat radiator or an evaporator. Specifically, when heat is radiated from the first refrigerant to the second refrigerant in the refrigerant heat exchanger (30), the refrigerant heat exchanger (30) in the first refrigerant circuit (10) functions as a "heat radiator," and the refrigerant heat exchanger (30) in the second refrigerant circuit (20) functions as an "evaporator." Conversely, when heat is radiated from the second refrigerant to the first refrigerant in the refrigerant heat exchanger (30), the refrigerant heat exchanger (30) in the first refrigerant circuit (10) functions as an "evaporator," and the refrigerant heat exchanger (30) in the second refrigerant circuit (20) functions as a "heat radiator."

[0064] [Water Circuit] In the water circuit (40), water supplied to a predetermined object circulates. In this example, the water circuit (40) has a pump (41) for circulating the water. The water circuit (40) is also provided with a hot water storage tank (not shown) for storing heated water. In the water circuit (40), the pump (41), the second flow path (22b) of the second water heat exchanger (22), the second flow path (14b) of the first water heat exchanger (14), and the hot water storage tank are connected in that order.

[0065] [Various Sensors] The refrigeration cycle device (1) is also equipped with various sensors (80), such as pressure sensors and temperature sensors. Examples of physical quantities detected by the various sensors (80) include physical quantities related to the first refrigerant circuit (10), physical quantities related to the second refrigerant circuit (20), and physical quantities related to the water circuit (40). The various information detected by the various sensors (80) is transmitted to the control unit (100), which will be described later.

[0066] Examples of physical quantities relating to the first refrigerant circuit (10) include the pressure and temperature of the high-pressure refrigerant in the first refrigerant circuit (10), the pressure and temperature of the low-pressure refrigerant in the first refrigerant circuit (10), the degree of superheating of the first refrigerant at the outlet of the heat exchanger that functions as an evaporator in the first refrigerant circuit (10), and the temperature of the outdoor air transported to the heat source heat exchanger (12). For example, the high-pressure refrigerant in the first refrigerant circuit (10) is the first refrigerant discharged from the first compressor (11), and the low-pressure refrigerant in the first refrigerant circuit (10) is the first refrigerant drawn into the first compressor (11).

[0067] Examples of physical quantities relating to the second refrigerant circuit (20) include the pressure and temperature of the high-pressure refrigerant in the second refrigerant circuit (20), the pressure and temperature of the low-pressure refrigerant in the second refrigerant circuit (20), and the degree of superheating of the second refrigerant at the outlet of the heat exchanger that functions as an evaporator in the second refrigerant circuit (20). For example, the high-pressure refrigerant in the second refrigerant circuit (20) is the second refrigerant discharged from the second compressor (21), and the low-pressure refrigerant in the second refrigerant circuit (20) is the second refrigerant drawn into the second compressor (21).

[0068] Examples of physical quantities related to the water circuit (40) include the temperature of the water flowing into the second channel (14b) of the first water heat exchanger (14) and the temperature of the water flowing into the second channel (22b) of the second water heat exchanger (22).

[0069] The various sensors (80) described above may be sensors provided to directly detect the physical quantities described above, or they may be sensors provided to indirectly detect or estimate the physical quantities described above.

[0070] [Control Unit] The refrigeration cycle device (1) also includes a control unit (100). The control unit (100) includes an MCU (Micro Control Unit), electrical circuits, electronic circuits, etc. The MCU includes a CPU (Central Processing Unit), memory, communication interface, etc. The memory stores various programs for the CPU (processor) to execute. The memory also stores information and data used for controlling the refrigeration cycle device (1) (e.g., setting values ​​such as thresholds), information and data obtained by various sensors (80) (e.g., measured values), and information and data input from outside the refrigeration cycle device (1) (e.g., command values). The control unit (100) may consist of one physically independent element, or it may consist of two or more physically separated elements.

[0071] The control unit (100) controls the first refrigerant circuit (10) and the second refrigerant circuit (20). Specifically, the control unit (100) controls each part of the first refrigerant circuit (10) and the second refrigerant circuit (20) based on various information detected by various sensors (80) and instructions input by the operator of the refrigeration cycle device (1). For example, the operator inputs the desired instructions to the control unit (100) by inputting operations corresponding to the desired instructions to an operation unit (not shown), such as a remote controller. The operation unit transmits a signal corresponding to the operation to the control unit (100).

[0072] In this example, the control unit (100) controls the starting and stopping of the first compressor (11), the rotational speed of the first compressor (11), the opening degree of the first expansion valve (13), the switching of the first four-way switching valve (15), the starting and stopping of the outdoor fan (17), the rotational speed of the outdoor fan (17), the opening and closing of the first valve (64), the opening and closing of the second valve (65), the starting and stopping of the second compressor (21), the rotational speed of the second compressor (21), the opening degree of the second expansion valve (23), the starting and stopping of the pump (41), and so on.

[0073] [Heating Operation] Next, the heating operation performed in the refrigeration cycle device (1) will be explained with reference to Figure 3. The heating operation is an operation to heat the water in the water circuit (40). In the heating operation shown in Figure 3, in the first refrigerant circuit (10), the first water heat exchanger (14) and the refrigerant heat exchanger (30) act as radiators, and the heat source heat exchanger (12) acts as an evaporator. In the second refrigerant circuit (20), the second water heat exchanger (22) acts as a radiator, and the refrigerant heat exchanger (30) acts as an evaporator. In this heating operation, the water in the water circuit (40) is heated in the first water heat exchanger (14) and the second water heat exchanger (22).

[0074] Specifically, during heating operation, the control unit (100) sets the first four-way switching valve (15) to the first state. This connects the discharge side of the first compressor (11) to the gas flow path (61). The control unit (100) also closes the first valve (64) and opens the second valve (65). This puts the bypass mechanism (60) into a "third state" where the first refrigerant flows through the first water heat exchanger (14) without flowing through the connecting flow path (63). The control unit (100) also drives the first compressor (11), the outdoor fan (17), the second compressor (21), and the pump (41), and adjusts the opening of the first expansion valve (13) and the second expansion valve (23) as appropriate.

[0075] In the first refrigerant circuit (10), the first refrigerant flows sequentially through the first compressor (11), the first water heat exchanger (14), the refrigerant heat exchanger (30), the receiver (16), the first expansion valve (13), and the heat source heat exchanger (12).

[0076] Specifically, in the first refrigerant circuit (10), the first refrigerant discharged from the first compressor (11) dissipates heat to the water in the water circuit (40) in the first water heat exchanger (14). This heats the water in the water circuit (40). The first refrigerant that flows out of the first water heat exchanger (14) dissipates heat to the second refrigerant in the second refrigerant circuit (20) in the refrigerant heat exchanger (30). This increases the degree of subcooling of the first refrigerant. The first refrigerant that flows out of the refrigerant heat exchanger (30) passes through the receiver (16), is depressurized in the first expansion valve (13), and evaporates by absorbing heat from the outside air in the heat source heat exchanger (12). The first refrigerant that flows out of the heat source heat exchanger (12) is drawn into the first compressor (11).

[0077] In the second refrigerant circuit (20), the second refrigerant flows sequentially through the second compressor (21), the second water heat exchanger (22), the second expansion valve (23), and the refrigerant heat exchanger (30).

[0078] Specifically, in the second refrigerant circuit (20), the second refrigerant discharged from the second compressor (21) dissipates heat into the water in the water circuit (40) in the second water heat exchanger (22). This heats the water in the water circuit (40). The second refrigerant that flows out of the second water heat exchanger (22) is depressurized in the second expansion valve (23) and evaporates by absorbing heat from the first refrigerant in the first refrigerant circuit (10) in the refrigerant heat exchanger (30). The refrigerant that flows out of the refrigerant heat exchanger (30) is drawn into the second compressor (21).

[0079] In the water circuit (40), the water transported by the pump (41) flows sequentially through the second water heat exchanger (22) and the first water heat exchanger (14). Specifically, the water discharged from the pump (41) is heated in the second water heat exchanger (22) and the first water heat exchanger (14) and flows into the hot water storage tank. In this way, the water heated in the water circuit (40) is used to generate hot water in the hot water storage tank.

[0080] [Modification 1 of heating operation] In the heating operation described above, the first refrigerant may not flow to the first water heat exchanger (14). In this case, in the first refrigerant circuit (10), the refrigerant heat exchanger (30) becomes a heat radiator and the heat source heat exchanger (12) becomes an evaporator, and in the second refrigerant circuit (20), the second water heat exchanger (22) becomes a heat radiator and the refrigerant heat exchanger (30) becomes an evaporator. In modification 1 of heating operation, the water in the water circuit (40) is heated in the second water heat exchanger (22), but the water in the water circuit (40) is not heated in the first water heat exchanger (14).

[0081] Specifically, in Modification 1 of the heating operation, the control unit (100) opens the first valve (64) and closes the second valve (65). As a result, the bypass mechanism (60) enters a "fourth state" in which the first refrigerant flows through the connecting channel (63) without flowing through the first water heat exchanger (14). The other controls in Modification 1 of the heating operation are the same as those in the heating operation shown in Figure 3.

[0082] [Modification 2 of heating operation] In the heating operation described above, the second refrigerant may be prevented from flowing to the second water heat exchanger (22). In this case, in the first refrigerant circuit (10), the first water heat exchanger (14) and the refrigerant heat exchanger (30) become radiators, and the heat source heat exchanger (12) becomes an evaporator. The second refrigerant circuit (20) is stopped. In modification 2 of heating operation, the water in the water circuit (40) is heated in the first water heat exchanger (14), but the water in the water circuit (40) is not heated in the second water heat exchanger (22).

[0083] Specifically, in Modification 2 of the heating operation, the control unit (100) stops the second compressor (21) and does not adjust the opening degree of the second expansion valve (23). The other controls in Modification 2 of the heating operation are the same as those in the heating operation shown in Figure 3.

[0084] In the refrigeration cycle device (1), the control unit (100) may switch between heating operation, modified heating operation 1, and modified heating operation 2 based on the target temperature of the water supplied to a predetermined target in the water circuit (40) and the temperature of the water flowing into the first water heat exchanger (14) or the second water heat exchanger (22).

[0085] [Defrost Operation] Next, with reference to Figures 4 and 5, the defrost operation performed in the refrigeration cycle device (1) of Embodiment 1 will be described. The defrost operation is an operation to defrost the heat source heat exchanger (12). If heating operation is continued, frost may accumulate on the heat source heat exchanger (12), which functions as an evaporator in the first refrigerant circuit (10). If frost accumulates on the heat source heat exchanger (12), the capacity of the heat source heat exchanger (12) will decrease. Therefore, it is desirable to perform a defrost operation to defrost the heat source heat exchanger (12).

[0086] During defrosting, the control unit (100) drives the first refrigerant circuit (10) when the first four-way switching valve (15) is in the second state (the discharge side of the first compressor (11) is connected to the heat source heat exchanger (12)).

[0087] In Embodiment 1, during defrosting operation, the control unit (100) drives the first refrigerant circuit (10) such that the heat source heat exchanger (12) becomes a heat radiator and the refrigerant heat exchanger (30) in the first refrigerant circuit (10) becomes an evaporator.

[0088] In Embodiment 1, the defrost operation includes a first operation and a second operation performed after the completion of the first operation. The control unit (100) determines whether the conditions for ending the first operation and starting the second operation (switching conditions) are met. If the control unit (100) determines that the switching conditions are met after the start of the first operation, it terminates the first operation and starts the second operation.

[0089] Examples of switching conditions include the condition that the difference between the temperature of the first refrigerant at the inlet of the first flow path (30a) of the refrigerant heat exchanger (30) and the temperature of the first refrigerant at the outlet of the first flow path (30a) of the refrigerant heat exchanger (30) is less than or equal to a predetermined value, the condition that a predetermined time has elapsed since the start of the first operation, and the condition that the degree of superheating of the first refrigerant at the outlet of the first flow path (30a) of the refrigerant heat exchanger (30) is less than or equal to a predetermined value. These conditions are examples of conditions under which the residual heat of the refrigerant heat exchanger (30) is considered to be unusable for defrosting operation (i.e., there is no residual heat remaining in the refrigerant heat exchanger (30) that can be used for defrosting operation).

[0090] In the first operation, the control unit (100) drives the first refrigerant circuit (10) when the bypass mechanism (60) is in the fourth state (a state in which the first refrigerant flows through the connecting channel (63) without flowing through the first water heat exchanger (14). Also in the first operation, the control unit (100) drives the pump (41).

[0091] In the second operation, the control unit (100) drives the first refrigerant circuit (10) with the bypass mechanism (60) switched from the fourth state to the third state (a state in which the first refrigerant flows through the first water heat exchanger (14) without flowing through the connecting flow path (63). Also in the second operation, the control unit (100) drives the pump (41).

[0092] [First operation of defrosting] Next, with reference to Figure 4, the first operation included in defrosting will be explained. In the first operation, in the first refrigerant circuit (10), the heat source heat exchanger (12) becomes a heat radiator, and the refrigerant heat exchanger (30) becomes an evaporator. The second refrigerant circuit (20) is stopped.

[0093] Specifically, in the first operation, the control unit (100) sets the first four-way switching valve (15) to the second state. As a result, the discharge side of the first compressor (11) is connected to the heat source heat exchanger (12). The control unit (100) also sets the first valve (64) to the open state and the second valve (65) to the closed state. As a result, the bypass mechanism (60) enters the "fourth state" in which the first refrigerant flows through the connecting channel (63) without flowing through the first water heat exchanger (14). The control unit (100) also drives the first compressor (11), the outdoor fan (17), and the pump (41), stops the second compressor (21), and adjusts the opening degree of the first expansion valve (13) as appropriate.

[0094] In the first refrigerant circuit (10), the first refrigerant flows sequentially through the first compressor (11), the heat source heat exchanger (12), the receiver (16), the first expansion valve (13), and the refrigerant heat exchanger (30), bypassing the first water heat exchanger (14).

[0095] Specifically, in the first refrigerant circuit (10), the first refrigerant discharged from the first compressor (11) dissipates heat into the outside air in the heat source heat exchanger (12). This heats the heat source heat exchanger (12), and as a result, the heat source heat exchanger (12) is defrosted. The first refrigerant that flows out of the heat source heat exchanger (12) passes through the receiver (16), is depressurized in the first expansion valve (13), and evaporates in the refrigerant heat exchanger (30) by absorbing heat from the second refrigerant in the second refrigerant circuit (20). In the refrigerant heat exchanger (30), the first refrigerant absorbs the residual heat of the refrigerant heat exchanger (30). The first refrigerant that flows out of the refrigerant heat exchanger (30) bypasses the first water heat exchanger (14) and is then drawn into the first compressor (11).

[0096] In the water circuit (40), the water transported by the pump (41) flows sequentially through the second water heat exchanger (22) and the first water heat exchanger (14).

[0097] [Second operation of defrosting] Next, with reference to Figure 5, the second operation included in the defrosting operation will be explained. In the second operation, in the first refrigerant circuit (10), the heat source heat exchanger (12) becomes a heat radiator, and the refrigerant heat exchanger (30) and the first water heat exchanger (14) become evaporators. The second refrigerant circuit (20) remains stopped.

[0098] Specifically, in the second operation, the control unit (100) closes the first valve (64) and opens the second valve (65). As a result, the bypass mechanism (60) enters a third state in which the first refrigerant flows through the first water heat exchanger (14) without flowing through the connecting flow path (63). Other controls in the second operation are the same as those in the first operation.

[0099] In the first refrigerant circuit (10), the first refrigerant flows sequentially through the first compressor (11), the heat source heat exchanger (12), the receiver (16), the first expansion valve (13), the refrigerant heat exchanger (30), and the first water heat exchanger (14).

[0100] Specifically, in the first refrigerant circuit (10), the first refrigerant discharged from the first compressor (11) dissipates heat into the outside air in the heat source heat exchanger (12). This heats the heat source heat exchanger (12), and as a result, the heat source heat exchanger (12) is defrosted. The refrigerant flowing out of the heat source heat exchanger (12) passes through the receiver (16), is depressurized in the first expansion valve (13), and evaporates in the refrigerant heat exchanger (30) by absorbing heat from the second refrigerant in the second refrigerant circuit (20). The first refrigerant flowing out of the refrigerant heat exchanger (30) evaporates in the first water heat exchanger (14) by absorbing heat from the water in the water circuit (40). The first refrigerant flowing out of the first water heat exchanger (14) is drawn into the first compressor (11).

[0101] In the water circuit (40), the water transported by the pump (41) flows sequentially through the second water heat exchanger (22) and the first water heat exchanger (14).

[0102] [Operation Switching in Defrost Operation] Next, with reference to Figure 6, operation switching in defrost operation will be explained. In this example, when switching from heating operation to defrost operation, the first operation starts, and then the system switches from the first operation to the second operation. Specifically, when the defrost operation start conditions (conditions for starting defrost operation) are met during heating operation, the following processes are performed.

[0103] <Step (ST11)> The control unit (100) stops the first compressor (11) and the second compressor (21).

[0104] <Step (ST12)> Next, the control unit (100) opens the first valve (64).

[0105] <Step (ST13)> Next, the control unit (100) closes the second valve (65).

[0106] <Step (ST14)> Next, the control unit (100) switches the first four-way switching valve (15) from the first state to the second state.

[0107] <Step (ST15)> Next, the control unit (100) starts the first compressor (11). This starts the first operation. Next, the process in step (ST16) is performed.

[0108] Step (ST16) The control unit (100) determines whether the difference between the temperature of the first refrigerant at the inlet of the first flow path (30a) of the refrigerant heat exchanger (30) and the temperature of the first refrigerant at the outlet of the first flow path (30a) of the refrigerant heat exchanger (30) is less than or equal to a predetermined value. The process in step (ST16) is repeated until the temperature difference between the inlet and outlet of the first flow path (30a) of the refrigerant heat exchanger (30) is less than or equal to a predetermined value, at which point the process in step (ST17) is performed.

[0109] <Step (ST17)> The control unit (100) opens the second valve (65).

[0110] <Step (ST18)> Next, the control unit (100) closes the first valve (64). This starts the second operation. Next, the process in step (ST19) is performed.

[0111] <Step (ST19)> The control unit (100) determines whether the defrost operation termination condition (the condition for terminating the defrost operation) is met. The process in step (ST19) is repeated until the defrost operation termination condition is met, at which point the defrost operation ends and the heating operation resumes.

[0112] [Effects of Embodiment 1] As described above, in the refrigeration cycle device (1) of Embodiment 1, the first four-way switching valve (15) (first switching mechanism) is switchable between a first state in which the discharge side of the first compressor (11) is connected to the first water heat exchanger (14) or the refrigerant heat exchanger (30), and a second state in which the discharge side of the first compressor (11) is connected to the heat source heat exchanger (12). In defrost operation for defrosting the heat source heat exchanger (12), the control unit (100) drives the first refrigerant circuit (10) with the first four-way switching valve (15) in the second state.

[0113] In the above configuration, during defrosting operation, the first refrigerant circuit (10) is driven when the first switching mechanism (15) is in the second state, thereby supplying the high-temperature, high-pressure first refrigerant discharged from the first compressor (11) to the heat source heat exchanger (12). This allows the heat source heat exchanger (12) to be defrosted.

[0114] Furthermore, in the refrigeration cycle device (1) of Embodiment 1, the bypass mechanism (60) (second switching mechanism) is switchable between a third state in which the first refrigerant flows through the first water heat exchanger (14) without flowing through the connecting channel (63), and a fourth state in which the first refrigerant flows through the connecting channel (63) without flowing through the first water heat exchanger (14).

[0115] In the above configuration, it is possible to switch between operation in which the first refrigerant flows through the first water heat exchanger (14) and operation in which the first refrigerant does not flow through the first water heat exchanger (14). This improves the flexibility of operation of the refrigeration cycle device (1). For example, before performing operation in which the first refrigerant flows through the first water heat exchanger (14) (second operation), operation in which the first refrigerant does not flow through the first water heat exchanger (14) (first operation) can be performed. This slows down the temperature drop of the water in the water circuit (40), thereby improving comfort.

[0116] Furthermore, in the refrigeration cycle device (1) of Embodiment 1, the control unit (100) drives the first refrigerant circuit (10) such that, during defrost operation, the heat source heat exchanger (12) becomes a heat radiator and the refrigerant heat exchanger (30) in the first refrigerant circuit (10) becomes an evaporator (heat absorber).

[0117] In the above configuration, during defrosting operation, the heat obtained in the refrigerant heat exchanger (30) can be used to defrost the heat source heat exchanger (12). This makes it possible to accelerate the defrosting of the heat source heat exchanger (12).

[0118] Furthermore, in the refrigeration cycle device (1) of Embodiment 1, the defrost operation includes a first operation. In the first operation, the control unit (100) drives the first refrigerant circuit (10) with the bypass mechanism (60) (second switching mechanism) in the fourth state.

[0119] In the above configuration, the first refrigerant can be prevented from flowing through the first water heat exchanger (14) during the first operation. This makes it possible to suppress the temperature drop of the water in the water circuit (40) more than when the first refrigerant flows through the first water heat exchanger (14) and the first water heat exchanger (14) functions as an evaporator (heat absorber).

[0120] Furthermore, in the refrigeration cycle device (1) of Embodiment 1, the defrost operation includes the first operation described above and a second operation performed after the completion of the first operation. In the second operation, the control unit (100) drives the first refrigerant circuit (10) with the bypass mechanism (60) (second switching mechanism) switched from the fourth state to the third state.

[0121] In the above configuration, the first water heat exchanger (14) can function as an evaporator (heat absorber) during the second operation. This allows the heat obtained in the first water heat exchanger (14) to be used for defrosting the heat source heat exchanger (12) during the second operation, thus accelerating the defrosting of the heat source heat exchanger (12) compared to when only the first operation is performed during defrosting.

[0122] Furthermore, in the refrigeration cycle device (1) of Embodiment 1, the control unit (100) drives the pump (41) during the second operation.

[0123] In the above configuration, during the second operation, the pump (41) is driven to prevent the water in the water circuit (40) from stagnating in the first water heat exchanger (14). This makes it possible to suppress the temperature drop of the water in the water circuit (40) in the first water heat exchanger (14).

[0124] Furthermore, in the refrigeration cycle device (1) of Embodiment 1, the control unit (100) drives the pump (41) during the first operation.

[0125] In the above configuration, by driving the pump (41) during the first operation which is performed before the second operation, it is possible to prevent the water in the water circuit (40) from stagnating in the first water heat exchanger (14) even before the start of the second operation. This makes it easier to suppress the temperature drop of the water in the water circuit (40) in the first water heat exchanger (14) during the second operation.

[0126] (Embodiment 2) The refrigeration cycle device (1) of Embodiment 2 differs from the refrigeration cycle device (1) of Embodiment 1 in its control during the second operation included in the defrost operation. The other configurations and processes of the refrigeration cycle device (1) of Embodiment 2 are the same as those of the refrigeration cycle device (1) of Embodiment 1.

[0127] [Second operation of defrost operation] In the second operation included in the defrost operation of Embodiment 2, the control unit (100) drives the first refrigerant circuit (10) with the bypass mechanism (60) in the fourth state. The control unit (100) also drives the second refrigerant circuit (20) so that the second refrigerant flows sequentially through the second compressor (21), the second water heat exchanger (22), the second expansion valve (23), and the refrigerant heat exchanger (30). Note that the opening of the second expansion valve (23) in the second operation is greater than the opening of the second expansion valve (23) in the heating operation where the second water heat exchanger (22) becomes a heat radiator and the refrigerant heat exchanger (30) in the second refrigerant circuit (20) becomes an evaporator (for example, the assumed maximum opening). For example, the opening of the second expansion valve (23) in the second operation is fully open.

[0128] In the second embodiment, the control unit (100) drives the second refrigerant circuit (20) so that the second compressor (21) is driven intermittently during the second operation. The control unit (100) also stops the pump (41) during the second operation.

[0129] Next, with reference to Figure 7, the second operation included in the defrost operation of Embodiment 2 will be described. In the second operation of Embodiment 2, in the first refrigerant circuit (10), the heat source heat exchanger (12) becomes a heat radiator, and the refrigerant heat exchanger (30) becomes an evaporator. In the second refrigerant circuit (20), the second refrigerant dissipates heat in the refrigerant heat exchanger (30).

[0130] Specifically, in the second operation, the control unit (100) maintains the first valve (64) in the open state and the second valve (65) in the closed state. As a result, the bypass mechanism (60) is maintained in the "fourth state in which the first refrigerant flows through the connecting channel (63) without flowing through the first water heat exchanger (14)". The control unit (100) also maintains the first compressor (11) and the outdoor fan (17) in the driven state and continues to adjust the opening degree of the first expansion valve (13).

[0131] Then, in the second operation, the control unit (100) sets the opening of the second expansion valve (23) to a predetermined opening and drives the second compressor (21) intermittently. The predetermined opening is set to an opening (for example, fully open) that allows the second refrigerant, which is discharged from the second compressor (21) and passes sequentially through the second water heat exchanger (22) and the second expansion valve (23), to dissipate heat in the refrigerant heat exchanger (30).

[0132] In the first refrigerant circuit (10), the first refrigerant flows sequentially through the first compressor (11), the heat source heat exchanger (12), the receiver (16), the first expansion valve (13), and the refrigerant heat exchanger (30), bypassing the first water heat exchanger (14).

[0133] Specifically, in the first refrigerant circuit (10), the first refrigerant discharged from the first compressor (11) dissipates heat into the outside air in the heat source heat exchanger (12). This heats the heat source heat exchanger (12), and as a result, the heat source heat exchanger (12) is defrosted. The refrigerant flowing out of the heat source heat exchanger (12) passes through the receiver (16), is depressurized in the first expansion valve (13), and evaporates in the refrigerant heat exchanger (30) by absorbing heat from the second refrigerant in the second refrigerant circuit (20). The first refrigerant flowing out of the refrigerant heat exchanger (30) bypasses the first water heat exchanger (14) and is then drawn into the first compressor (11).

[0134] In the second refrigerant circuit (20), the second refrigerant flows sequentially through the second compressor (21), the second water heat exchanger (22), the second expansion valve (23) which is maintained at a predetermined opening, and the refrigerant heat exchanger (30).

[0135] Specifically, the second refrigerant discharged from the second compressor (21) flows sequentially through the second water heat exchanger (22) and the second expansion valve (23), which is maintained at a predetermined opening (for example, fully open), and then dissipates heat to the first refrigerant in the first refrigerant circuit (10) in the refrigerant heat exchanger (30).

[0136] In the water circuit (40), since the pump (41) is stopped, the water in the water circuit (40) does not flow between the first water heat exchanger (14) and the second water heat exchanger (22).

[0137] [Effects of Embodiment 2] The refrigeration cycle device (1) of Embodiment 2 can obtain the same effects as the refrigeration cycle device (1) of Embodiment 1. For example, the high-temperature, high-pressure first refrigerant discharged from the first compressor (11) can be supplied to the heat source heat exchanger (12), so the heat source heat exchanger (12) can be defrosted.

[0138] Furthermore, in the refrigeration cycle device (1) of Embodiment 2, the control unit (100) drives the first refrigerant circuit (10) in the second operation included in the defrost operation with the bypass mechanism (60) (second switching mechanism) in the fourth state, and drives the second refrigerant circuit (20) so that the second refrigerant flows sequentially through the second compressor (21), the second water heat exchanger (22), the second expansion valve (23), and the refrigerant heat exchanger (30). The opening of the second expansion valve (23) in the second operation is greater than the opening of the second expansion valve (23) in the heating operation where the second water heat exchanger (22) becomes a heat radiator and the refrigerant heat exchanger (30) in the second refrigerant circuit (20) becomes an evaporator (heat absorber).

[0139] In the above configuration, by driving the second refrigerant circuit (20) with the opening of the second expansion valve (23) greater than the opening of the second expansion valve (23) during the second operation than during the heating operation, the high-temperature, high-pressure second refrigerant discharged from the second compressor (21) can be dissipated to the first refrigerant in the first refrigerant circuit (10) in the refrigerant heat exchanger (30) during the second operation. As a result, the heat obtained in the refrigerant heat exchanger (30) (heat from the second refrigerant discharged from the second compressor (21)) can be used for defrosting the heat source heat exchanger (12) during the second operation, thereby accelerating the defrosting of the heat source heat exchanger (12).

[0140] Furthermore, in the refrigeration cycle device (1) of Embodiment 2, the control unit (100) drives the second refrigerant circuit (20) so that the second compressor (21) is driven intermittently during the second operation.

[0141] In the above configuration, during the second operation, the second compressor (21) is driven intermittently to prevent the temperature of the second refrigerant discharged from the second compressor (21) from becoming too high. This makes it possible to suppress the occurrence of high-temperature abnormalities (abnormalities in which the temperature of the second refrigerant exceeds the allowable temperature) in the second refrigerant circuit (20).

[0142] Furthermore, in the refrigeration cycle device (1) of Embodiment 2, the control unit (100) stops the pump (41) during the second operation.

[0143] In the above configuration, during the second operation, the pump (41) can be stopped to prevent water from the water circuit (40) from flowing through the first water heat exchanger (14) and the second water heat exchanger (22). This suppresses heat dissipation from the second refrigerant in the second refrigerant circuit (20) to the water in the water circuit (40) in the second water heat exchanger (22), thereby allowing the heat from the second refrigerant discharged from the second compressor (21) to be effectively utilized for defrosting the heat source heat exchanger (12).

[0144] (Embodiment 3) Figure 8 illustrates the configuration of the refrigeration cycle device (1) of Embodiment 3. The refrigeration cycle device (1) of Embodiment 3 differs from the refrigeration cycle device (1) of Embodiment 1 in the "configuration of the second refrigerant circuit (20)", "control during heating operation", and "control during refrigerant recovery operation". The other configurations and processes of the refrigeration cycle device (1) of Embodiment 3 are the same as those of the refrigeration cycle device (1) of Embodiment 1.

[0145] The second refrigerant circuit (20) of Embodiment 3 has a second four-way switching valve (24) in addition to the configuration of the second refrigerant circuit (20) of Embodiment 1 shown in Figure 1.

[0146] The second four-way switching valve (24) has a first port (P1), a second port (P2), a third port (P3), and a fourth port (P4). The second four-way switching valve (24) is switchable between a fifth state in which the first port (P1) and the second port (P2) are in communication and the third port (P3) and the fourth port (P4) are in communication, and a sixth state (shown in Figure 8) in which the first port (P1) and the third port (P3) are in communication and the second port (P2) and the fourth port (P4) are in communication.

[0147] In this example, in the second four-way switching valve (24), the first port (P1) is connected to the discharge side of the second compressor (21), and the second port (P2) is connected to the first flow path (22a) of the second water heat exchanger (22). The third port (P3) is connected to the second flow path (30b) of the refrigerant heat exchanger (30), and the fourth port (P4) is connected to the suction side of the second compressor (21). Furthermore, the first flow path (22a) of the second water heat exchanger (22) is connected to the second flow path (30b) of the refrigerant heat exchanger (30) via the second expansion valve (23).

[0148] The second four-way switching valve (24) is an example of the third switching mechanism. The third switching mechanism can switch between a fifth state in which the discharge side of the second compressor (21) is connected to the second water heat exchanger (22), and a sixth state in which the discharge side of the second compressor (21) is connected to the refrigerant heat exchanger (30).

[0149] [Heating Operation] In the heating operation of Embodiment 3, the control unit (100) drives the second refrigerant circuit (20) when the second four-way switching valve (24) is in the fifth state (the discharge side of the second compressor (21) is connected to the second water heat exchanger (22)).

[0150] The control of the second refrigerant circuit (20) in the heating operation of Embodiment 3 (control of the second compressor (21) and the second expansion valve (23)) is the same as the control of the second refrigerant circuit (20) in the heating operation of Embodiment 1. The flow and state changes (heat dissipation and heat absorption) of the second refrigerant in the second refrigerant circuit (20) in the heating operation of Embodiment 3 are the same as the flow and state changes of the second refrigerant in the second refrigerant circuit (20) in the heating operation of Embodiment 1.

[0151] [Defrost Operation] The defrost operation of Embodiment 3 includes a first operation but does not include a second operation. In the first operation included in the defrost operation of Embodiment 3, the control unit (100) drives the second refrigerant circuit (20) when the second four-way switching valve (24) is in the sixth state (the discharge side of the second compressor (21) is connected to the refrigerant heat exchanger (30)). The control of the first refrigerant circuit (10) and the water circuit (40) in the first operation included in the defrost operation of Embodiment 3 is the same as the control of the first refrigerant circuit (10) and the water circuit (40) in the first operation included in the defrost operation of Embodiment 1.

[0152] Next, with reference to Figure 8, the first operation included in the defrost operation of Embodiment 3 will be described. In the first operation of Embodiment 3, in the first refrigerant circuit (10), the heat source heat exchanger (12) becomes a radiator and the refrigerant heat exchanger (30) becomes an evaporator. In the second refrigerant circuit (20), the refrigerant heat exchanger (30) becomes a radiator and the second water heat exchanger (22) becomes an evaporator.

[0153] Specifically, in the first operation of Embodiment 3, the control unit (100) sets the second four-way switching valve (24) to the sixth state. As a result, the discharge side of the second compressor (21) is connected to the refrigerant heat exchanger (30). The control unit (100) also drives the second compressor (21) and adjusts the opening degree of the second expansion valve (23) as appropriate. The other controls in the first operation of Embodiment 3 (controls relating to the first refrigerant circuit (10) and the water circuit (40)) are the same as the controls in the first operation of Embodiment 1.

[0154] In the second refrigerant circuit (20), the second refrigerant flows sequentially through the second compressor (21), the refrigerant heat exchanger (30), the second expansion valve (23), and the second water heat exchanger (22). Specifically, in the second refrigerant circuit (20), the second refrigerant discharged from the second compressor (21) dissipates heat to the first refrigerant in the first refrigerant circuit (10) in the refrigerant heat exchanger (30). The second refrigerant flowing out of the refrigerant heat exchanger (30) is depressurized in the second expansion valve (23) and absorbs heat from the water in the water circuit (40) in the second water heat exchanger (22). The second refrigerant flowing out of the second water heat exchanger (22) is drawn into the second compressor (21).

[0155] [Effects of Embodiment 3] The refrigeration cycle device (1) of Embodiment 3 can obtain the same effects as the refrigeration cycle device (1) of Embodiment 1. For example, the high-temperature, high-pressure first refrigerant discharged from the first compressor (11) can be supplied to the heat source heat exchanger (12), so the heat source heat exchanger (12) can be defrosted.

[0156] Furthermore, in the refrigeration cycle device (1) of Embodiment 3, the second four-way switching valve (24) (third switching mechanism) is switchable between a fifth state in which the discharge side of the second compressor (21) is connected to the second water heat exchanger (22), and a sixth state in which the discharge side of the second compressor (21) is connected to the refrigerant heat exchanger (30). In the first operation included in the defrost operation, the control unit (100) drives the second refrigerant circuit (20) with the second four-way switching valve (24) (third switching mechanism) in the sixth state.

[0157] In the above configuration, during the first operation, the high-temperature, high-pressure second refrigerant discharged from the second compressor (21) can be dissipated into the first refrigerant in the first refrigerant circuit (10) via the refrigerant heat exchanger (30). As a result, during the first operation, the heat obtained in the refrigerant heat exchanger (30) (heat from the second refrigerant discharged from the second compressor (21)) can be used for defrosting the heat source heat exchanger (12), thereby accelerating the defrosting of the heat source heat exchanger (12).

[0158] (Embodiment 4) Figure 9 illustrates the configuration of the refrigeration cycle device (1) of Embodiment 4. The refrigeration cycle device (1) of Embodiment 4 differs from the refrigeration cycle device (1) of Embodiment 1 in the second valve (65) of the bypass mechanism (60) and the control during defrost operation. The other configurations and operations of the refrigeration cycle device (1) of Embodiment 4 are the same as those of the refrigeration cycle device (1) of Embodiment 1.

[0159] The second valve (65) of the bypass mechanism (60) in Embodiment 4 is an electrically operated valve with adjustable opening.

[0160] In the defrost operation of Embodiment 4, the control unit (100) drives the first refrigerant circuit (10) such that the first expansion valve (13) and the second valve (65) are open, the first valve (64) is closed, and the first refrigerant flows sequentially through the first compressor (11), the heat source heat exchanger (12), the first expansion valve (13), the refrigerant heat exchanger (30), the second valve (65), and the first water heat exchanger (14). Note that the opening degree of the first expansion valve (13) in defrost operation is greater than the opening degree of the second valve (65) in defrost operation (for example, the assumed maximum opening degree). For example, the opening degree of the first expansion valve (13) in defrost operation is fully open.

[0161] Furthermore, in the defrost operation of Embodiment 4, the control unit (100) drives the second refrigerant circuit (20) so that the second refrigerant flows sequentially through the second compressor (21), the second water heat exchanger (22), the second expansion valve (23), and the refrigerant heat exchanger (30). Also, in the defrost operation of Embodiment 4, the control unit (100) drives the pump (41).

[0162] Next, with reference to Figure 9, the defrost operation of Embodiment 4 will be described. In defrost operation, in the first refrigerant circuit (10), the heat source heat exchanger (12) and the refrigerant heat exchanger (30) act as radiators, and the first water heat exchanger (14) acts as an evaporator. In the second refrigerant circuit (20), the second water heat exchanger (22) acts as a radiator, and the refrigerant heat exchanger (30) acts as an evaporator.

[0163] Specifically, during defrosting operation, the control unit (100) sets the first four-way switching valve (15) to the second state. As a result, the discharge side of the first compressor (11) is connected to the heat source heat exchanger (12). The control unit (100) also closes the first valve (64) and opens the second valve (65). As a result, the bypass mechanism (60) enters a third state in which the first refrigerant flows through the first water heat exchanger (14) without flowing through the connecting passage (63). The control unit (100) also drives the first compressor (11), the outdoor fan (17), the second compressor (21), and the pump (41), and adjusts the opening degree of the second valve (65) as appropriate.

[0164] In the first refrigerant circuit (10), the first refrigerant flows sequentially through the first compressor (11), the heat source heat exchanger (12), the receiver (16), the first expansion valve (13), the refrigerant heat exchanger (30), the second valve (65), and the first water heat exchanger (14).

[0165] Specifically, in the first refrigerant circuit (10), the first refrigerant discharged from the first compressor (11) dissipates heat to the outside air in the heat source heat exchanger (12). This heats the heat source heat exchanger (12), resulting in defrosting of the heat source heat exchanger (12). The first refrigerant flowing out of the heat source heat exchanger (12) passes through the receiver (16), then through the first expansion valve (13) which is maintained at a predetermined opening (e.g., fully open), and dissipates heat to the second refrigerant in the second refrigerant circuit (20) in the refrigerant heat exchanger (30). This increases the degree of subcooling of the first refrigerant. The first refrigerant flowing out of the refrigerant heat exchanger (30) is depressurized in the second valve (65) and dissipates heat and evaporates in the first water heat exchanger (14). The first refrigerant flowing out of the first water heat exchanger (14) is drawn into the first compressor (11).

[0166] In the second refrigerant circuit (20), the second refrigerant flows sequentially through the second compressor (21), the second water heat exchanger (22), the second expansion valve (23), and the refrigerant heat exchanger (30).

[0167] Specifically, in the second refrigerant circuit (20), the second refrigerant discharged from the second compressor (21) dissipates heat into the water in the water circuit (40) in the second water heat exchanger (22). The second refrigerant flowing out of the second water heat exchanger (22) is depressurized in the second expansion valve (23) and evaporates by absorbing heat from the first refrigerant in the first refrigerant circuit (10) in the refrigerant heat exchanger (30). The second refrigerant flowing out of the refrigerant heat exchanger (30) is drawn into the second compressor (21).

[0168] In the water circuit (40), the water transported by the pump (41) flows sequentially through the second water heat exchanger (22) and the first water heat exchanger (14). Specifically, the water discharged from the pump (41) releases heat from the second refrigerant in the second refrigerant circuit (20) in the second water heat exchanger (22), absorbs heat from the first refrigerant in the first refrigerant circuit (10) in the first water heat exchanger (14), and then flows into the hot water storage tank.

[0169] [Effects of Embodiment 4] The refrigeration cycle device (1) of Embodiment 4 can obtain the same effects as the refrigeration cycle device (1) of Embodiment 1. For example, the high-temperature, high-pressure first refrigerant discharged from the first compressor (11) can be supplied to the heat source heat exchanger (12), so the heat source heat exchanger (12) can be defrosted.

[0170] Furthermore, in the refrigeration cycle device (1) of Embodiment 4, the bypass mechanism (60) (second switching mechanism) includes a first valve (64) provided in the connecting passage (63) and a second valve (65) provided in the liquid passage (62) between the connection point between the connecting passage (63) and the liquid passage (62) and the liquid side of the first water heat exchanger (14). The second valve (65) is an electrically operated valve.

[0171] In the above configuration, by making the second valve (65) of the second switching mechanism (60) an electric valve, the amount of the first refrigerant flowing through the first water heat exchanger (14) can be controlled. This improves the degree of freedom in controlling the first water heat exchanger (14).

[0172] Furthermore, in the refrigeration cycle device (1) of Embodiment 4, the control unit (100) drives the first refrigerant circuit (10) such that, during defrost operation, the first expansion valve (13) is open, the first valve (64) is closed, and the first refrigerant flows sequentially through the first compressor (11), the heat source heat exchanger (12), the first expansion valve (13), the refrigerant heat exchanger (30), the second valve (65), and the first water heat exchanger (14). The opening degree of the first expansion valve (13) during defrost operation is greater than the opening degree of the second valve (65) during defrost operation.

[0173] In the above configuration, during defrost operation, the heat source heat exchanger (12) and the refrigerant heat exchanger (30) in the first refrigerant circuit (10) can function as radiators, and the first water heat exchanger (14) can function as an evaporator (heat absorber). This allows for a greater degree of subcooling of the first refrigerant in the refrigerant heat exchanger (30), thereby improving the COP (Coefficient of Performance) during defrost operation.

[0174] Furthermore, in the refrigeration cycle device (1) of Embodiment 4, the control unit (100) drives the second refrigerant circuit (20) and the pump (41) so that the second refrigerant flows sequentially through the second compressor (21), the second water heat exchanger (22), the second expansion valve (23), and the refrigerant heat exchanger (30) during defrost operation.

[0175] In the above configuration, during defrosting operation, the second refrigerant circuit (20) can be driven so that the second water heat exchanger (22) acts as a heat radiator and the refrigerant heat exchanger (30) in the second refrigerant circuit (20) acts as an evaporator (heat absorber). This allows the water in the water circuit (40) to be heated in the second water heat exchanger (22), and the supercooling of the first refrigerant in the refrigerant heat exchanger (30) to be promoted.

[0176] Furthermore, in the above configuration, during defrosting operation, driving the pump (41) prevents water in the water circuit (40) from stagnating in the first water heat exchanger (14) and the second water heat exchanger (22), and allows the water heated in the second water heat exchanger (22) to be circulated back into the water circuit (40). This suppresses a decrease in the temperature of the water in the water circuit (40).

[0177] (Other Embodiments) In the above description, the following configuration may be used.

[0178] The refrigeration cycle device (1) does not necessarily have to include a receiver (16) and a bridge circuit (50). In this case, the first expansion valve (13) may be placed between the heat source heat exchanger (12) and the refrigerant heat exchanger (30).

[0179] As an example of the first switching mechanism, a "first four-way switching valve (15)" was given, but it is not limited to this. For example, the first switching mechanism may be composed of two three-way valves, or of other combinations of valves.

[0180] An example of a second switching mechanism, the bypass mechanism (60), has been given as having a "first valve (64)" and a "second valve (65)," but it is not limited to this. For example, the bypass mechanism (60) may have a three-way valve.

[0181] As an example of a third switching mechanism, a "second four-way switching valve (24)" was given, but it is not limited to this. For example, the third switching mechanism may be composed of two three-way valves, or of other combinations of valves.

[0182] Furthermore, while embodiments and modifications have been described, it will be understood that various changes in form and details are possible without departing from the spirit and scope of the claims. Additionally, elements of the above embodiments, modifications, and other embodiments may be combined or substituted as appropriate. Moreover, the designations "first," "second," "third," etc., in the specification and claims are used to distinguish the phrases to which these designations are given, and do not limit the number or order of such phrases.

[0183] As described above, this disclosure is useful as a refrigeration cycle device.

[0184] 1 Refrigeration cycle unit 10 First refrigerant circuit 11 First compressor 12 Heat source heat exchanger 13 First expansion valve 14 First water heat exchanger 15 First four-way switching valve (first switching mechanism) 16 Receiver 17 Outdoor fan 20 Second refrigerant circuit 21 Second compressor 22 Second water heat exchanger 23 Second expansion valve 24 Second four-way switching valve (third switching mechanism) 30 Refrigerant heat exchanger 40 Water circuit 41 Pump 50 Bridge circuit 60 Bypass mechanism (second switching mechanism) 61 Gas flow path 62 Liquid flow path 63 Connecting flow path 64 First valve 65 Second valve 100 Control unit

Claims

1. The system comprises a first refrigerant circuit (10) through which a first refrigerant circulates, a second refrigerant circuit (20) through which a second refrigerant circulates, a refrigerant heat exchanger (30) for exchanging heat between the first refrigerant in the first refrigerant circuit (10) and the second refrigerant in the second refrigerant circuit (20), a water circuit (40) through which water circulates, and a control unit (100) for controlling the first refrigerant circuit (10) and the second refrigerant circuit (20), wherein the first refrigerant circuit (10) includes a first compressor (11), a heat source heat exchanger (12), a first expansion valve (13), a first water heat exchanger (14), and a first switching mechanism (15), and the second refrigerant circuit (20) includes a second compressor (21), a second water heat exchanger (22), and a second expansion valve (23). The first water heat exchanger (14) exchanges heat between the first refrigerant of the first refrigerant circuit (10) and the water of the water circuit (40); the second water heat exchanger (22) exchanges heat between the second refrigerant of the second refrigerant circuit (20) and the water of the water circuit (40); the first switching mechanism (15) is switchable between a first state in which the discharge side of the first compressor (11) is connected to the first water heat exchanger (14) or the refrigerant heat exchanger (30) and a second state in which the discharge side of the first compressor (11) is connected to the heat source heat exchanger (12); and the control unit (100) drives the first refrigerant circuit (10) in a state where the first switching mechanism (15) is in the second state during a defrost operation to defrost the heat source heat exchanger (12).

2. The refrigeration cycle apparatus according to claim 1, wherein the first refrigerant circuit (10) comprises a gas flow path (61) connected to the gas side of the first water heat exchanger (14), a liquid flow path (62) connected to the liquid side of the first water heat exchanger (14), a connecting flow path (63) connecting the gas flow path (61) and the liquid flow path (62), and a second switching mechanism (60), wherein the second switching mechanism (60) is switchable between a third state in which the first refrigerant flows through the first water heat exchanger (14) without flowing through the connecting flow path (63), and a fourth state in which the first refrigerant flows through the connecting flow path (63) without flowing through the first water heat exchanger (14).

3. A refrigeration cycle apparatus according to claim 2, wherein the control unit (100) drives the first refrigerant circuit (10) such that, in the defrost operation, the heat source heat exchanger (12) becomes a heat radiator and the refrigerant heat exchanger (30) in the first refrigerant circuit (10) becomes a heat absorber.

4. A refrigeration cycle apparatus according to claim 3, wherein the defrost operation includes a first operation, and the control unit (100) drives the first refrigerant circuit (10) in the first operation with the second switching mechanism (60) in the fourth state.

5. A refrigeration cycle apparatus according to claim 4, wherein the defrost operation includes the first operation and a second operation performed after the completion of the first operation, and the control unit (100) drives the first refrigerant circuit (10) in the second operation with the second switching mechanism (60) switched from the fourth state to the third state.

6. A refrigeration cycle device according to claim 5, wherein the water circuit (40) has a pump (41), and the control unit (100) drives the pump (41) in the second operation.

7. A refrigeration cycle device according to claim 6, wherein the control unit (100) drives the pump (41) in the first operation.

8. A refrigeration cycle apparatus according to claim 4, wherein the defrost operation includes a first operation and a second operation performed after the completion of the first operation, the control unit (100) drives the first refrigerant circuit (10) in the second operation with the second switching mechanism (60) in the fourth state, and drives the second refrigerant circuit (20) such that the second refrigerant flows sequentially through the second compressor (21), the second water heat exchanger (22), the second expansion valve (23), and the refrigerant heat exchanger (30), and the opening of the second expansion valve (23) in the second operation is greater than the opening of the second expansion valve (23) in the heating operation in which the second water heat exchanger (22) is a heat radiator and the refrigerant heat exchanger (30) in the second refrigerant circuit (20) is a heat absorber.

9. A refrigeration cycle apparatus according to claim 8, wherein the control unit (100) drives the second refrigerant circuit (20) such that the second compressor (21) is driven intermittently during the second operation.

10. A refrigeration cycle apparatus according to claim 8 or 9, wherein the water circuit (40) has a pump (41), and the control unit (100) stops the pump (41) in the second operation.

11. The refrigeration cycle apparatus according to claim 4, wherein the second refrigerant circuit (20) has a third switching mechanism (24), the third switching mechanism (24) is switchable between a fifth state in which the discharge side of the second compressor (21) is connected to the second water heat exchanger (22), and a sixth state in which the discharge side of the second compressor (21) is connected to the refrigerant heat exchanger (30), and the control unit (100) drives the second refrigerant circuit (20) in the sixth state during the first operation.

12. A refrigeration cycle device according to claim 2, wherein the second switching mechanism (60) comprises a first valve (64) provided in the connecting passage (63) and a second valve (65) provided in the liquid passage (62) between the connection point between the connecting passage (63) and the liquid passage (62) and the liquid side of the first water heat exchanger (14), and the second valve (65) is an electrically operated valve.

13. A refrigeration cycle apparatus according to claim 12, wherein the control unit (100) drives the first refrigerant circuit (10) such that in the defrost operation the first expansion valve (13) is open and the first valve (64) is closed, and the first refrigerant flows sequentially through the first compressor (11), the heat source heat exchanger (12), the first expansion valve (13), the refrigerant heat exchanger (30), the second valve (65), and the first water heat exchanger (14), and the opening degree of the first expansion valve (13) in the defrost operation is greater than the opening degree of the second valve (65) in the defrost operation.

14. A refrigeration cycle device according to claim 13, wherein the water circuit (40) has a pump (41), and the control unit (100) drives the second refrigerant circuit (20) and the pump (41) in the defrost operation such that the second refrigerant flows sequentially through the second compressor (21), the second water heat exchanger (22), the second expansion valve (23), and the refrigerant heat exchanger (30).

Images