Refrigeration cycle device

Abstract

A refrigeration cycle device (1) comprises a refrigerant circuit (10) and a control unit (4). The refrigerant circuit (10) has a first heat exchanger (13). The first heat exchanger (13) performs heat exchange between outdoor air and a refrigerant. The refrigerant circulates in the refrigerant circuit (10). The control unit (4) performs: defrosting operation to melt frost attached to the first heat exchanger; and capacity reduction operation to reduce capacity. The control unit (4) performs the capacity reduction operation in the case where an index regarding frost formation satisfies a second condition, and performs the defrosting operation in the case where the index regarding frost formation satisfies a first condition during the capacity reduction operation.

Description

Refrigeration Cycle Equipment

[0001] This relates to a refrigeration cycle device.

[0002] Patent Document 1 (JP 2018-91579 A) discloses that under certain conditions that require the reduction of frost during heating operation, air heated by the humidifying heater of the humidifying unit flows to an air outlet located near the outdoor heat exchanger.

[0003] However, Patent Document 1 does not disclose how to suppress frost formation on the outdoor heat exchanger in a refrigeration cycle device that does not include a humidification unit.

[0004] A refrigeration cycle device of a first aspect includes a refrigerant circuit and a control unit. The refrigerant circuit has a first heat exchanger. The first heat exchanger exchanges heat between outdoor air and a refrigerant. The refrigerant circulates through the refrigerant circuit. The control unit performs a defrosting operation and a reduced capacity operation. The defrosting operation melts frost that has formed on the first heat exchanger. The reduced capacity operation reduces capacity. The control unit performs the reduced capacity operation when an index related to frost formation satisfies a second condition, and performs the defrosting operation when the index related to frost formation satisfies a first condition during the reduced capacity operation.

[0005] According to the refrigeration cycle apparatus of the first aspect, when the index relating to frost formation satisfies the second condition, a reduced capacity operation is performed to reduce the capacity of the refrigeration cycle apparatus before a defrosting operation to melt frost formed on the first heat exchanger that exchanges heat with outdoor air. By performing this reduced capacity operation, frost formation on the first heat exchanger can be suppressed.

[0006] A refrigeration cycle apparatus according to a second aspect is the refrigeration cycle apparatus according to the first aspect, wherein the refrigerant includes R290.

[0007] Because R290 is a low-pressure refrigerant, the size of the first heat exchanger is large, which results in a long defrosting operation. However, in the refrigeration cycle apparatus of the second aspect, even when a refrigerant containing R290 is used, frost formation in the first heat exchanger can be suppressed by performing reduced capacity operation. Therefore, even when a refrigerant containing R290 is used, frost formation in the first heat exchanger can be suppressed by performing reduced capacity operation, thereby reducing the frequency of defrosting operations.

[0008] A refrigeration cycle apparatus according to a third aspect is the refrigeration cycle apparatus according to the first or second aspect, wherein the first heat exchanger is a microchannel heat exchanger.

[0009] Microchannel heat exchangers are prone to frost formation. However, in the refrigeration cycle apparatus of the third aspect, even when such a microchannel heat exchanger is used as the first heat exchanger that exchanges heat with outdoor air, frost formation on the first heat exchanger can be suppressed by performing reduced capacity operation.

[0010] A refrigeration cycle apparatus according to a fourth aspect is the refrigeration cycle apparatus according to any one of the first to third aspects, wherein the refrigerant circuit further includes a second heat exchanger. The second heat exchanger exchanges heat between the refrigerant and water. The refrigeration cycle apparatus further includes a water circuit and a heat source. The water circulates through the water circuit and flows through the second heat exchanger. The heat source heats the water.

[0011] In the refrigeration cycle apparatus of the fourth aspect, when the temperature of the water in the water circuit falls below the target hot water outlet temperature during reduced capacity operation, etc., the heat source can heat the water, thereby suppressing frost formation and a decrease in the water temperature.

[0012] A refrigeration cycle apparatus according to a fifth aspect is the refrigeration cycle apparatus according to the fourth aspect, wherein the refrigerant circuit further includes a compressor, and the control unit performs reduced capacity operation by reducing the capacity of the compressor or by lowering the target hot water outlet temperature.

[0013] In the refrigeration cycle apparatus of the fifth aspect, the capacity of the refrigeration cycle apparatus is reduced by lowering the capacity of the compressor or the target hot water outlet temperature, so that a refrigeration cycle apparatus that suppresses frost formation can be easily realized.

[0014] A refrigeration cycle apparatus according to a sixth aspect is the refrigeration cycle apparatus according to the fourth or fifth aspect, wherein the control unit operates the heat source during reduced capacity operation.

[0015] In the refrigeration cycle apparatus of the sixth aspect, even if the temperature of the water heated by the refrigerant in the second heat exchanger becomes lower than the target hot water outlet temperature due to a decrease in the capacity of the refrigeration cycle apparatus during reduced capacity operation, the heat source heats the water. In this way, the capacity that is insufficient during reduced capacity operation is compensated for by the heat source. Therefore, a refrigeration cycle apparatus that suppresses frost formation and a decrease in the water temperature can be easily realized.

[0016] A refrigeration cycle apparatus according to a seventh aspect is the refrigeration cycle apparatus according to the sixth aspect, wherein, during reduced capacity operation, the amount of water heated by the refrigeration cycle apparatus is greater than the amount of water heated by the heat source.

[0017] In the refrigeration cycle apparatus of the seventh aspect, during reduced capacity operation, the amount of water heated by the heat source is not reversed to the amount of water heated by the refrigeration cycle apparatus, so that a decrease in the efficiency of the refrigeration cycle apparatus can be suppressed.

[0018] A refrigeration cycle apparatus according to an eighth aspect is the refrigeration cycle apparatus according to any one of the fourth aspect to the seventh aspect, wherein the control unit activates the heat source during the defrosting operation.

[0019] In the refrigeration cycle apparatus of the eighth aspect, even if the temperature of the water drops during the defrosting operation, the heat source heats the water, so that a decrease in comfort can be suppressed.

[0020] A ninth aspect of the present invention is a refrigeration cycle apparatus according to any one of the first to eighth aspects, wherein the second condition is that the outside air temperature is not less than -10°C and not more than 7°C.

[0021] In the refrigeration cycle apparatus of the ninth aspect, the control is performed using the temperature of the outdoor air as the second condition, and therefore the reduced capacity operation can be easily controlled.

[0022] A refrigeration cycle device of a tenth aspect is a refrigeration cycle device of any one of the first aspect to the eighth aspect, wherein the second condition is a state in which the capacity required based on the outside air temperature exceeds the capacity at which the first heat exchanger can operate without frosting.

[0023] In a state where the capacity required based on the outdoor air temperature exceeds the capacity to prevent frost formation, the capacity of the refrigeration cycle device is high because the outdoor air temperature is low. In this case, the first heat exchanger is cooled, making frost formation more likely. Therefore, in the refrigeration cycle device of the tenth aspect, such a state is considered to satisfy the second condition, and frost formation can be suppressed by performing reduced capacity operation.

[0024] The refrigeration cycle device of an eleventh aspect is a refrigeration cycle device of any one of the first aspect to the eighth aspect, wherein the second condition is that the evaporation temperature of the refrigerant in the first heat exchanger is lower than the dew point temperature by a predetermined temperature or more, and the outside air temperature is 2°C or less.

[0025] When the evaporation temperature is lower than the dew point temperature by a predetermined temperature or more and the outside air temperature is low, such as 2° C. or less, the first heat exchanger is cooled, which makes it more likely to form frost. Therefore, in the refrigeration cycle apparatus of the eleventh aspect, such a state is considered to satisfy the second condition, and thereby, frost formation can be suppressed by performing reduced capacity operation.

[0026] A refrigeration cycle apparatus according to a twelfth aspect is the refrigeration cycle apparatus according to any one of the first aspect to the eleventh aspect, wherein the maximum duration of the defrosting operation is shorter than the maximum duration of the reduced capacity operation.

[0027] In the refrigeration cycle apparatus of the twelfth aspect, by continuously performing reduced capacity operation, the frequency of defrosting operation is reduced and, even if defrosting operation is performed, the maximum duration of the defrosting operation is shortened, thereby making it possible to reduce the time during which comfort is reduced due to the defrosting operation.

[0028] A refrigeration cycle apparatus according to a thirteenth aspect is the refrigeration cycle apparatus according to any one of the first to twelfth aspects, wherein the control unit switches to defrosting operation when a first condition is satisfied during reduced capacity operation.

[0029] In the refrigeration cycle apparatus of the thirteenth aspect, the control unit performs the defrosting operation when the first condition is satisfied even during the reduced capacity operation, thereby making it possible to suppress a decrease in the efficiency of the refrigeration cycle apparatus.

[0030] Fig. 1 is a schematic configuration diagram of a refrigeration cycle device according to an embodiment of the present disclosure; Fig. 2 is a control block diagram of the refrigeration cycle device; Fig. 3 is a diagram showing the operation (flow of refrigerant) in cooling operation of the refrigeration cycle device; Fig. 4 is a diagram showing the operation (flow of refrigerant) in heating operation of the refrigeration cycle device; Fig. 5 is a diagram showing a control flow in defrosting cooling operation of the refrigeration cycle device; Fig. 6 is a diagram showing a control flow in reduced capacity operation of the refrigeration cycle device; Fig. 7 is a diagram explaining a second condition of Modification 4; Fig. 8 is a diagram explaining a second condition of Modification 5;

[0031] (1) Overall Configuration The refrigeration cycle device 1 according to one embodiment of the present disclosure shown in FIG. 1 is a device that cools or heats water circulating in a water circuit 30 by performing a vapor compression refrigeration cycle in a refrigerant circuit 10, and uses this water to cool or heat a target space.

[0032] The refrigeration cycle device 1 includes a heat source unit 2 and a utilization unit 3. The heat source unit 2 and the utilization unit 3 are connected to each other. In this embodiment, there is one heat source unit 2 and one utilization unit 3.

[0033] The refrigeration cycle apparatus 1 also includes a refrigerant circuit 10, a water circuit 30, and a control unit 4. Refrigerant circulates in the refrigerant circuit 10. Water circulates in the water circuit 30. The refrigerant circuit 10 and the water circuit 30 are connected to each other. The control unit 4 performs heating operation, cooling operation, defrosting operation, and reduced capacity operation.

[0034] (2) Detailed Configuration (2-1) Refrigerant Circuit The refrigerant circuit 10 is a circuit through which refrigerant circulates during normal operation such as heating operation and cooling operation, and during operation to prevent frosting of the first heat exchanger 13 (described later), such as defrosting operation and reduced capacity operation.

[0035] A refrigerant is sealed in the refrigerant circuit 10. The refrigerant is not particularly limited, but is a flammable refrigerant in this example. The flammable refrigerant is a refrigerant that is combustible. Examples of flammable refrigerants include hydrocarbon refrigerants such as R1234yf, R1234ze, and R32. In this example, the flammable refrigerant is a refrigerant classified as highly flammable (A3) by ISO 817, and includes R290 (propane) in this embodiment. The refrigerant may be R290 alone or a mixture of R290 and another refrigerant. The refrigerant also includes refrigerating machine oil. Examples of the refrigerating machine oil include PAG (polyalkylene glycol).

[0036] The refrigerant circuit 10 mainly includes a compressor 11, a switching mechanism 12, a first heat exchanger 13, a first expansion mechanism 14, a second heat exchanger 15, a liquid pipe 16, a liquid-gas heat exchanger 17, a branch pipe 18, an injection pipe 19, a second expansion mechanism 20, an economizer heat exchanger 21, a first valve 22, a second valve 23, a third valve 24, a fourth valve 25, and an accumulator 26.

[0037] (2-1-1) Compressor The compressor 11 compresses a low-pressure refrigerant in the refrigeration cycle to a high pressure. Here, the compressor 11 is a two-stage compressor that draws in the low-pressure refrigerant in the refrigeration cycle, compresses it to an intermediate pressure in the refrigeration cycle, and then further compresses the intermediate-pressure refrigerant to a high pressure and discharges it.

[0038] The compressor 11 includes a casing 11a, a first compression element 11b, a second compression element 11c, a drive motor 11d, a first suction portion 11e, a second suction portion 11f, and a discharge portion 11g.

[0039] The casing 11a accommodates a first compression element 11b and a second compression element 11c. The first compression element 11b and the second compression element 11c are connected to a single drive shaft (not shown). When the compressor 11 is in operation, a drive motor 11d rotationally drives the first compression element 11b and the second compression element 11c via the drive shaft. In other words, the compressor 11 has a single-shaft, two-stage compression structure.

[0040] The first suction section 11e draws low-pressure refrigerant from the refrigerant circuit 10. The second suction section 11f draws intermediate-pressure refrigerant from the refrigerant circuit 10. The discharge section 11g discharges high-pressure refrigerant to the refrigerant circuit 10. The second suction section 11f is an example of a suction section.

[0041] The second suction section 11f has a check valve (not shown) that allows the refrigerant to flow from the outside to the inside of the casing 11a and restricts the refrigerant from flowing from the inside to the outside of the casing 11a.

[0042] The first compression element 11b compresses the refrigerant drawn by the first suction port 11e to an intermediate pressure and discharges it to the second compression element 11c. The second compression element 11c compresses both the intermediate-pressure refrigerant drawn by the first compression element 11b and the intermediate-pressure refrigerant drawn by the second suction port 11f to a high pressure and discharges it to the discharge port 11g.

[0043] The structure of the compressor 11 is not limited to the single-shaft two-stage compression structure, and may be configured with a compression element driven by a separate drive motor, for example.

[0044] (2-1-2) Switching Mechanism The switching mechanism 12 switches the direction of refrigerant flow in the refrigerant circuit 10 between two states. The switching mechanism 12 is a four-way switching valve. The switching mechanism 12 has a first port P1, a second port P2, a third port P3, and a fourth port P4.

[0045] The switching mechanism 12 switches between a first state (a state indicated by a solid line in FIG. 1 ) and a second state (a state indicated by a dashed line in FIG. 1 ). In the first state, the switching mechanism 12 connects the first port P1 to the second port P2 and connects the third port P3 to the fourth port P4. In the second state, the switching mechanism 12 connects the first port P1 to the fourth port P4 and connects the second port P2 to the third port P3.

[0046] The switching mechanism 12 is not limited to a four-way switching valve, and may be configured, for example, by combining a plurality of electromagnetic valves and refrigerant flow paths.

[0047] (2-1-3) First Heat Exchanger The first heat exchanger 13 is an air heat exchanger. The first heat exchanger 13 exchanges heat between the refrigerant flowing inside and the outside air (outdoor air) sent from the first fan 13a. The first heat exchanger 13 functions as a refrigerant radiator during cooling operation and as a refrigerant evaporator during heating operation. The first heat exchanger 13 may be a cross-fin heat exchanger, a microchannel heat exchanger, or any other heat exchanger suitable for the application. In this embodiment, the first heat exchanger 13 is a microchannel heat exchanger.

[0048] The first heat exchanger 13 has a refrigerant flow path (not shown). The refrigerant flow path of the first heat exchanger 13 is provided in the refrigerant circuit 10.

[0049] In the following, for ease of explanation, during heating operation, the end of the refrigerant flow path of the first heat exchanger 13 into which the refrigerant flows will be referred to as the first end 13aa, and the end of the refrigerant flow path from which the refrigerant flows out will be referred to as the second end 13ab.

[0050] (2-1-4) First Expansion Mechanism The first expansion mechanism 14 reduces the pressure of the refrigerant passing through it to a low pressure. The first expansion mechanism 14 is provided in the liquid pipe 16. The first expansion mechanism 14 is, for example, an electric expansion valve.

[0051] (2-1-5) Second Heat Exchanger The second heat exchanger 15 is a water heat exchanger. In this embodiment, the second heat exchanger 15 exchanges heat between the refrigerant flowing through the refrigerant circuit 10 and the water flowing through the water circuit 30. The second heat exchanger 15 functions as a refrigerant evaporator during cooling operation and as a refrigerant radiator during heating operation. A heat exchanger suitable for the application, such as a plate heat exchanger, is used as the second heat exchanger 15.

[0052] The second heat exchanger 15 has a refrigerant flow path 15a and a water flow path 15b. The refrigerant flow path 15a is provided in the refrigerant circuit 10. The water flow path 15b is provided in the water circuit 30. The refrigerant flowing through the refrigerant flow path 15a exchanges heat with the water flowing through the water flow path 15b. The water that has exchanged heat with the refrigerant circulates through the water circuit 30 and heats or cools the air in the target space.

[0053] For ease of explanation, in the heating operation, the end of the refrigerant flow path 15a into which the refrigerant flows will be referred to as a first end 15aa, and the end of the refrigerant flow path 15a from which the refrigerant flows out will be referred to as a second end 15ab.

[0054] (2-1-6) Liquid Pipe The liquid pipe 16 connects the radiator (the first heat exchanger 13 during cooling operation and the second heat exchanger 15 during heating operation) and the evaporator (the second heat exchanger 15 during cooling operation and the first heat exchanger 13 during heating operation). Here, the liquid pipe 16 connects the first end 13aa of the refrigerant flow path of the first heat exchanger 13 to the second end 15ab of the refrigerant flow path 15a of the second heat exchanger 15.

[0055] (2-1-7) Liquid-to-Gas Heat Exchanger The liquid-to-gas heat exchanger 17 exchanges heat between the refrigerant flowing from the radiator (second heat exchanger 15 during heating operation) to the evaporator (first heat exchanger 13 during heating operation) and the refrigerant flowing from the evaporator to the compressor 11. The liquid-to-gas heat exchanger 17 is a pre-cooling heat exchanger that cools the refrigerant flowing from the radiator to the evaporator. The liquid-to-gas heat exchanger 17 has a first heat transfer pipe 17a and a second heat transfer pipe 17b.

[0056] The first heat transfer pipe 17a is connected to the third port P3 of the switching mechanism 12. The other end of the first heat transfer pipe 17a is connected to the first suction section 11e of the compressor 11 via the accumulator 26.

[0057] The second heat transfer pipe 17b is connected to the branch pipe 18 at both ends thereof, and the refrigerant flows from the radiator to the evaporator through the second heat transfer pipe 17b.

[0058] In this embodiment, during heating operation, the liquid-gas heat exchanger 17 exchanges heat between the refrigerant passing through the first heat transfer pipe 17a and the refrigerant passing through the second heat transfer pipe 17b. On the other hand, during cooling operation, the liquid-gas heat exchanger 17 does not exchange heat between the refrigerant passing through the first heat transfer pipe 17a and the refrigerant passing through the second heat transfer pipe 17b. Specifically, the refrigerant flows through the first heat transfer pipe 17a and the second heat transfer pipe 17b during heating operation, but does not flow through the second heat transfer pipe 17b during cooling operation.

[0059] (2-1-8) Branch Pipe The branch pipe 18 is a refrigerant flow path that branches off from the liquid pipe 16 between the second heat exchanger 15 and the first expansion mechanism 14 and connects to the second heat transfer pipe 17b of the liquid-gas heat exchanger 17. In other words, the second heat transfer pipe 17b is provided midway through the branch pipe 18.

[0060] One end of the second heat transfer pipe 17b is connected to a branch pipe 18 branching from the second heat exchanger 15 side. The other end of the second heat transfer pipe 17b is connected to a branch pipe 18 branching from the first expansion mechanism 14 side.

[0061] In the following, for ease of explanation, the point where the branch pipe 18 branches off from the second heat exchanger 15 side of the liquid pipe 16 may be referred to as the first branch section 18a, and the point where the branch pipe 18 branches off from the first expansion mechanism 14 side of the liquid pipe 16 may be referred to as the second branch section 18b.

[0062] (2-1-9) Injection Pipe The injection pipe 19 branches off a portion of the refrigerant flowing from the radiator (the second heat exchanger 15 in FIG. 1 ) to the evaporator (the first heat exchanger 13 in FIG. 1 ) and sends it to the compressor 11. Here, the injection pipe 19 branches off from the liquid pipe 16 and connects to the first suction section 11e and the second suction section 11f of the compressor 11. Therefore, the injection pipe 19 can merge with the low-pressure refrigerant of the compressor 11 and with the refrigerant of an intermediate pressure between the high pressure and low pressure of the compressor 11.

[0063] The injection pipe 19 branches off between the radiator (the second heat exchanger 15 in FIG. 1 ) and the economizer heat exchanger 21. In this embodiment, the injection pipe 19 branches off between the second heat exchanger 15 and the economizer heat exchanger 21 in the refrigerant flow during heating operation. In other words, the injection pipe 19 branches off downstream of the radiator and upstream of the economizer heat exchanger 21 during heating operation.

[0064] In FIG. 1, the injection tube 19 has a first portion 19a, a second portion 19b, a third portion 19c, and a fourth portion 19d.

[0065] The first portion 19a branches off from the liquid pipe 16 and is shared with the branch pipe 18. Here, the first portion 19a branches off from a first branch portion 18a in the liquid pipe 16.

[0066] The second section 19b allows the refrigerant that has flowed through the first section 19a to flow into a first heat transfer tube 21a (described later) of the economizer heat exchanger 21. The second section 19b is connected to the end of the first section 19a opposite to the branch section (first branch section 18a in this example) from the liquid pipe 16. The first heat transfer tube 21a of the economizer heat exchanger 21 is provided midway through the second section 19b.

[0067] The third section 19c allows the refrigerant that has flowed through the first heat transfer tube 21a of the economizer heat exchanger 21 to flow into the first suction section 11e of the compressor 11. The third section 19c connects the end of the second section 19b opposite to the first section 19a to the first suction section 11e of the compressor 11.

[0068] The fourth section 19d allows the refrigerant that has flowed through the first heat transfer tube 21a of the economizer heat exchanger 21 to flow into the second suction section 11f of the compressor 11. The fourth section 19d connects the end of the second section 19b opposite to the first section 19a to the second suction section 11f of the compressor 11.

[0069] (2-1-10) Second Expansion Mechanism The second expansion mechanism 20 reduces the pressure of the refrigerant passing through the injection pipe 19 to an intermediate pressure. The second expansion mechanism 20 is provided in the second section 19b of the injection pipe 19, between the connection section with the first section 19a and the economizer heat exchanger 21.

[0070] The second expansion mechanism 20 is, for example, an on / off valve such as a solenoid valve, or a flow control valve such as an electrically operated expansion valve. In this embodiment, the second expansion mechanism 20 is an electrically operated expansion valve.

[0071] (2-1-11) Economizer Heat Exchanger The economizer heat exchanger 21 exchanges heat between the refrigerant that passes through the injection pipe 19 and is decompressed by the second expansion mechanism 20, and the refrigerant that flows from the radiator to the evaporator. The economizer heat exchanger 21 has a first heat transfer pipe 21a and a second heat transfer pipe 21b. The economizer heat exchanger 21 exchanges heat between the refrigerant that passes through the first heat transfer pipe 21a and the refrigerant that passes through the second heat transfer pipe 21b.

[0072] The first heat transfer pipe 21a is connected to the injection pipe 19 through which the refrigerant flows. The first heat transfer pipe 21a is provided in the injection pipe 19. One end of the first heat transfer pipe 21a is connected to the second expansion mechanism 20 via the injection pipe 19. The other end of the first heat transfer pipe 21a is connected to the first suction section 11e and the second suction section 11f of the compressor 11 via the injection pipe 19.

[0073] The refrigerant flowing through the branch pipe 18 passes through the second heat transfer pipe 21b. The second heat transfer pipe 21b is provided on the branch pipe 18. One end of the second heat transfer pipe 21b is connected to the first valve 22 via the branch pipe 18. The other end of the second heat transfer pipe 21b is connected to the second heat transfer pipe 17b of the liquid-gas heat exchanger 17 via the branch pipe 18.

[0074] In this embodiment, during heating operation, the economizer heat exchanger 21 exchanges heat between the refrigerant passing through the first heat transfer tube 21a and the refrigerant passing through the second heat transfer tube 21b. On the other hand, during cooling operation, the economizer heat exchanger 21 does not exchange heat between the refrigerant passing through the first heat transfer tube 21a and the refrigerant passing through the second heat transfer tube 21b. Specifically, the refrigerant flows through the first heat transfer tube 21a and the second heat transfer tube 21b during heating operation, but does not flow through the first heat transfer tube 21a and the second heat transfer tube 21b during cooling operation.

[0075] (2-1-12) First Valve The first valve 22 regulates the flow of refrigerant from the liquid pipe 16 to the economizer heat exchanger 21 in the first portion 19a of the injection pipe 19. The first valve 22 is an on-off valve that switches between an open state and a closed state.

[0076] The first valve 22 is in an open state during heating operation and in a closed state during cooling operation.

[0077] (2-1-13) Second Valve The second valve 23 regulates the refrigerant flowing through the injection pipe 19 in the third portion 19c of the injection pipe 19 from flowing into the first suction section 11e of the compressor 11. The second valve 23 is an on-off valve that switches between an open state and a closed state.

[0078] The second valve 23 is closed in heating operation and is open in cooling operation.

[0079] (2-1-14) Third Valve The third valve 24 regulates the flow of refrigerant from the second branch portion 18b to the second heat transfer tube 17b in the branch pipe 18. The third valve 24 is provided in the branch pipe 18. The third valve 24 is a check valve that regulates the flow of refrigerant from the second branch portion 18b to the second heat transfer tube 17b and allows the flow of refrigerant from the second heat transfer tube 17b to the second branch portion 18b.

[0080] (2-1-15) Fourth Valve The fourth valve 25 regulates the flow of refrigerant from the first branch portion 18a to the second branch portion 18b in the liquid pipe 16. The fourth valve 25 is provided between the first branch portion 18a and the second branch portion 18b in the liquid pipe 16. The fourth valve 25 is a check valve that regulates the flow of refrigerant from the first branch portion 18a to the second branch portion 18b and allows the flow of refrigerant from the second branch portion 18b to the first branch portion 18a.

[0081] (2-1-16) Accumulator The accumulator 26 is connected between the switching mechanism 12 and the first suction section 11e of the compressor 11. Here, the accumulator 26 is provided in a refrigerant flow path that connects the other end of the first heat transfer tube 17a of the liquid-gas heat exchanger 17 and the first suction section 11e of the compressor 11. The accumulator 26 separates the refrigerant that flows out of the first heat transfer tube 17a of the liquid-gas heat exchanger 17 and flows into the first suction section 11e of the compressor 11 into gas refrigerant and liquid refrigerant.

[0082] (2-2) Water Circuit The water circuit 30 is a circuit through which water circulates during normal operation such as heating operation and cooling operation, and during operation to prevent frost formation on the first heat exchanger 13 such as defrosting operation and reduced capacity operation.

[0083] The water circuit 30 includes a second heat exchanger 15 , a pump 31 , a gas-liquid separator 32 , a third heat exchanger 33 , and a heat source 34 .

[0084] (2-2-1) Second Heat Exchanger The water flow path 15 b of the second heat exchanger 15 described above constitutes the water circuit 30 .

[0085] (2-2-2) Pump The pump 31 applies a predetermined pressure to the sucked water and discharges it. The pump 31 circulates the water filled in the water circuit 30 in a certain direction through the water circuit 30.

[0086] (2-2-3) Gas-Liquid Separator The gas-liquid separator 32 separates the refrigerant mixed in the water pipe connected to the second heat exchanger 15. The gas-liquid separator 32 is disposed downstream of the second heat exchanger 15. Here, the gas-liquid separator 32 is disposed between the outlet of the water flow path 15b of the second heat exchanger 15 and the inlet of the third heat exchanger 33.

[0087] (2-2-4) Third Heat Exchanger The third heat exchanger 33 exchanges heat between the water flowing inside and the indoor air sent from the second fan 33 a. The third heat exchanger 33 may be a heat exchanger suitable for the application, such as a radiator.

[0088] The third heat exchanger 33 has a water flow path (not shown). The water flow path of the third heat exchanger 33 is provided in the water circuit 30.

[0089] (2-2-5) Heat Source The heat source 34 heats the water filled in the water circuit 30. The heat source 34 is a backup heater that heats the water flowing through the water circuit 30 when the temperature of the water is low. Here, the capacity of the heat source 34 is half or less of the capacity of the refrigeration cycle apparatus 1.

[0090] The heat source 34 is provided between the third heat exchanger 33 and the second heat exchanger 15. Here, the heat source 34 is provided between the third heat exchanger 33 and the gas-liquid separator 32. As the heat source 34, a heater suitable for the application, such as a gas-fired boiler or an electric heater, is used.

[0091] (2-3) Heat Source Unit The heat source unit 2 is placed in a space different from the space to be heated or cooled. Here, the heat source unit 2 is installed outdoors (on the roof of a building, near the exterior wall of a building, etc.). The heat source unit 2 includes the above-mentioned refrigerant circuit 10, the first fan 13a, part of the above-mentioned water circuit 30, and various sensors. Here, the heat source unit 2 includes a pump 31 and a gas-liquid separator 32 as part of the water circuit 30.

[0092] (2-3-1) First Fan The first fan 13a sends outdoor air to the first heat exchanger 13. The first fan 13a is driven by a fan motor.

[0093] (2-3-2) Sensors The heat source unit 2 is provided with an outdoor temperature sensor 41 and an outlet hot water temperature sensor 42. The outdoor temperature sensor 41 detects the temperature of the outdoor air before passing through the first heat exchanger 13. The outlet hot water temperature sensor 42 detects the temperature of the water after passing through the second heat exchanger 15.

[0094] (2-4) User Machine The user machine 3 is installed in a building. The heat source machine 2 and the user machine 3 are thermally connected via the second heat exchanger 15. Here, the water circuit 30 of the user machine 3 is connected to the water flow path 15b of the second heat exchanger 15. The user machine 3 includes a portion of the water circuit 30 described above, a second fan 33a, and various sensors. Here, the user machine 3 includes a heat source 34 and a third heat exchanger 33 as part of the water circuit 30.

[0095] (2-4-1) Second Fan The second fan 33a sends indoor air to the third heat exchanger 33. The second fan 33a is driven by a fan motor.

[0096] (2-4-2) Sensor The utilization device 3 is provided with an indoor temperature sensor 43 that detects the indoor temperature, which is the temperature of the air taken in from the room before passing through the third heat exchanger 33.

[0097] (2-5) Control Unit (2-5-1) Overview The control unit 4 controls the components of the refrigeration cycle apparatus 1. As shown in FIG. 2 , the control unit 4 is electrically connected to the compressor 11, the switching mechanism 12, the first expansion mechanism 14, the second expansion mechanism 20, the first fan 13a, the second fan 33a, the first valve 22, the second valve 23, the pump 31, the heat source 34, the outdoor temperature sensor 41, the outlet hot water temperature sensor 42, and the indoor temperature sensor 43 so as to be able to send and receive signals. The control unit 4 acquires information such as the operating status of each device and the measured values ​​of each sensor. Based on the acquired information, the control unit 4 controls each device of the refrigeration cycle apparatus 1 to perform cooling operation, heating operation, defrosting operation, reduced capacity operation, etc.

[0098] The control unit 4 is realized by a computer. The control unit 4 includes a control and arithmetic device and a storage device (both not shown). A processor such as a CPU or a GPU can be used as the control and arithmetic device. The control and arithmetic device reads a program stored in the storage device and performs predetermined arithmetic processing in accordance with this program. Furthermore, the control and arithmetic device can write the results of calculations to the storage device and read information stored in the storage device in accordance with the program.

[0099] (2-5-2) Control During Defrosting Operation and Reduced Capacity Operation Hereinafter, the control by the control unit 4 during the defrosting operation and reduced capacity operation of the refrigeration cycle apparatus 1 will be described.

[0100] The defrosting operation is an operation for melting frost formed on the first heat exchanger 13. During the defrosting operation, the first heat exchanger 13 functions as a radiator. In this embodiment, the flow of refrigerant in the refrigerant circuit 10 during the defrosting operation is the same as during the cooling operation.

[0101] The reduced capacity operation is an operation for preventing the defrosting operation from occurring during heating operation. In other words, the reduced capacity operation is a frost prevention heating operation. The reduced capacity operation reduces the capacity during heating operation. Specifically, the reduced capacity operation operates the refrigeration cycle device 1 at a capacity lower than the capacity requested by the utilization device 3. Therefore, in the reduced capacity operation, the capacity of the second heat exchanger 15 to heat the water flowing through the water flow path 15b by the refrigerant flowing through the refrigerant flow path 15a is reduced. The flow of refrigerant in the refrigerant circuit 10 during the reduced capacity operation is the same as during heating operation.

[0102] The control unit 4 has a first condition and a second condition for an index related to frost formation in the first heat exchanger 13. The control unit 4 performs a defrosting operation when the index related to frost formation satisfies the first condition. The control unit 4 performs a reduced performance operation when the index related to frost formation satisfies the second condition. The control unit 4 switches to a defrosting operation during a reduced performance operation when the index related to frost formation satisfies the first condition.

[0103] The first condition is a condition under which a defrosting operation is necessary. The second condition is a condition under which a defrosting operation is not necessary. The second condition is a condition under which the possibility of frost formation is lower than that under the first condition. Therefore, the second condition is met before the first condition is met.

[0104] The first condition and the second condition are different. However, the second condition is similar to the first condition. The index related to frost formation is, for example, the outdoor air temperature. The outdoor air temperature under the second condition is higher than the outdoor air temperature under the first condition, and is preferably higher by 2°C or more than the outdoor air temperature under the first condition.

[0105] The second condition in this embodiment is that the outdoor air temperature (outdoor air temperature) is not less than -10°C and not more than 7°C. The first condition is that the outdoor air temperature is less than -10°C.

[0106] The first condition is not limited to the outside air temperature being equal to or lower than a predetermined value, and may be a condition such as a predetermined time having elapsed since the last defrosting operation was completed, a condition such as the temperature of the first heat exchanger 13 being equal to or lower than a predetermined value, or a condition such as the evaporation pressure or evaporation temperature of the refrigerant in the refrigerant circuit 10 being equal to or lower than a predetermined value. The second condition is not limited to the outside air temperature being equal to or lower than a predetermined value, and may be a condition such as the temperature of the first heat exchanger 13 being equal to or lower than a predetermined value lower than the temperature of the first condition, or a condition such as the evaporation pressure or evaporation temperature of the refrigerant in the refrigerant circuit 10 being equal to or lower than a predetermined value lower than the temperature of the first condition. The parameter (index) of the first condition and the parameter (index) of the second condition may be different.

[0107] Here, when the refrigeration cycle apparatus 1 is started, the control unit 4 performs reduced capacity operation if the first condition is not met but the second condition is met. Furthermore, when the refrigeration cycle apparatus 1 is started, the control unit 4 performs defrosting operation if the second condition is not met but the first condition is met. For example, when the outside air temperature is very low, such as -20°C, the control unit 4 performs defrosting operation without performing reduced capacity operation. For example, when the outside air temperature is low, such as 2°C, but no frost has formed on the first heat exchanger 13, the control unit 4 performs reduced capacity operation, and then, when frost forms on the first heat exchanger 13, the control unit 4 performs defrosting operation.

[0108] The control unit 4 performs a capacity reduction control to reduce the capacity of the heat pump during reduced capacity operation. In this embodiment, the control unit 4 performs the reduced capacity operation by reducing the capacity of the compressor 11 or by lowering the target hot water outlet temperature. Specifically, during reduced capacity operation, the control unit 4 reduces the capacity of the compressor 11 to a value lower than the capacity of the compressor 11 set based on the indoor air temperature requested by the user device 3 during heating operation. More specifically, the control unit 4 reduces the rotation speed of the motor of the compressor 11 during reduced capacity operation compared to heating operation. Furthermore, during reduced capacity operation, the control unit 4 lowers the target hot water outlet temperature of the water flowing out of the water flow path 15b of the second heat exchanger 15 below the target hot water outlet temperature set based on the indoor air temperature requested by the user device 3 during heating operation. More specifically, the control unit 4 sets the target hot water outlet temperature during reduced capacity operation to a value several degrees Celsius lower than that during heating operation.

[0109] When reduced capacity operation is performed, the temperature of the water heated by the refrigerant in second heat exchanger 15 becomes lower than the target hot water outlet temperature due to the reduced capacity of refrigeration cycle apparatus 1. For this reason, here, in order to compensate for the target hot water outlet temperature during reduced capacity operation, control unit 4 operates heat source 34 to heat the water before it flows into third heat exchanger 33. Control unit 4 may operate heat source 34 when switching from heating operation to reduced capacity operation, or may operate heat source 34 after a predetermined time has elapsed since switching from heating operation to reduced capacity operation.

[0110] During reduced performance operation, the amount of water heated by the refrigeration cycle apparatus 1 is greater than the amount of water heated by the heat source 34. Specifically, during reduced performance operation, the control unit 4 controls the heat source 34 so that the amount of water heated by the refrigerant in the second heat exchanger 15 is greater than the amount of water heated by the heat source 34. If the amount of water heated by the heat source 34 is reversed to the amount of water heated by the refrigeration cycle apparatus 1, the coefficient of performance (COP) will be lower. Therefore, when the amount of water heated by the heat source 34 becomes equal to or greater than the amount of water heated by the refrigeration cycle apparatus 1, the control unit 4 may switch from reduced performance operation to defrosting operation regardless of the first condition.

[0111] The control unit 4 controls the maximum duration of the defrosting operation and the maximum duration of the reduced performance operation. In this embodiment, the maximum duration of the defrosting operation is shorter than the maximum duration of the reduced performance operation. The maximum duration of the defrosting operation is, for example, 20 minutes. No upper limit is set for the maximum duration of the reduced performance operation. In other words, the maximum duration of the reduced performance operation is unlimited.

[0112] (3) Operation The operation of the refrigeration cycle apparatus 1 will be described with reference to Figures 1 to 6. The refrigeration cycle apparatus 1 performs cooling operation, heating operation, defrosting operation, and reduced capacity operation. The operation of the refrigeration cycle apparatus 1, including these operations, is controlled by the control unit 4.

[0113] (3-1) Cooling Operation Hereinafter, the operation of the refrigeration cycle apparatus 1 during cooling operation will be described with reference to Fig. 3. The cooling operation shown in Fig. 3 is performed by the control unit 4, upon receiving a command for cooling operation, controlling the operation of the compressor 11, the switching mechanism 12, the first expansion mechanism 14, the second expansion mechanism 20, the first fan 13a, the first valve 22, the second valve 23, the pump 31, the second fan 33a, the heat source 34, etc.

[0114] Specifically, the control unit 4 starts the compressor 11 and controls the rotation speed of the drive motor 11d of the compressor 11. The switching mechanism 12 is controlled to be in the second state. The opening of the first expansion mechanism 14 is controlled. The control unit 4 sets a target superheat degree of the refrigerant flowing out from the first end 15aa of the second heat exchanger 15, for example, based on a target outlet temperature of water flowing out from the water flow path 15b of the second heat exchanger 15. Then, the control unit 4 controls the opening of the first expansion mechanism 14 so that the superheat degree of the refrigerant flowing out from the second heat exchanger 15 approaches the target superheat degree. The second expansion mechanism 20 is controlled to be fully open or approximately fully open (hereinafter simply referred to as fully open). The first valve 22 is controlled to be in a closed state. The second valve 23 is controlled to be in an open state.

[0115] The control unit 4 also starts the operation of the pump 31. The heat source 34 is controlled not to operate.

[0116] (3-1-1) Refrigerant Circuit When the compressor 11 starts operating, low-pressure gas refrigerant in the refrigeration cycle is drawn in through the first suction port 11e. The first compression element 11b compresses the low-pressure refrigerant drawn in through the first suction port 11e to an intermediate pressure and discharges it to the second compression element 11c. The second compression element 11c compresses the intermediate-pressure refrigerant discharged from the first compression element 11b to a high pressure in the refrigeration cycle and discharges it as gas refrigerant to the discharge port 11g.

[0117] As will be described in detail later, during cooling operation, a portion of the injection pipe 19 becomes low pressure. Therefore, the check valve of the second suction part 11f restricts the outflow of intermediate-pressure refrigerant from the inside to the outside of the casing 11a.

[0118] The high-pressure gas refrigerant flowing out from the discharge port 11g passes through the switching mechanism 12, in this order, via the first port P1 and the fourth port P4, and flows into the refrigerant flow path of the first heat exchanger 13 from the second end 13ab. The refrigerant that flows into the first heat exchanger 13 exchanges heat with the outdoor air in the location where the first heat exchanger 13 is installed, dissipating heat, becoming high-pressure liquid refrigerant and flowing out from the first end 13aa. In this way, the first heat exchanger 13 functions as a radiator.

[0119] The high-pressure refrigerant flowing out of the first heat exchanger 13 flows through the liquid pipe 16, and is reduced in pressure to a low level when passing through the first expansion mechanism 14, becoming a gas-liquid two-phase refrigerant. Because the branch pipe 18 is provided with the third valve 24, the refrigerant flowing through the liquid pipe 16 passes through the fourth valve 25 without flowing into the branch pipe 18.

[0120] Because the first valve 22 is closed, the refrigerant that has passed through the fourth valve 25 flows from the second end 15ab into the refrigerant flow path of the second heat exchanger 15 without flowing into the branch pipe 18 or the injection pipe 19. The refrigerant that has flowed into the second heat exchanger 15 exchanges heat with water flowing through the water flow path 15b and evaporates, becoming a low-pressure gas refrigerant that flows out from the first end 15aa. In this way, the second heat exchanger 15 functions as an evaporator.

[0121] The low-pressure refrigerant flowing out of the second heat exchanger 15 passes through the switching mechanism 12, in this order, via the second port P2 and the third port P3, and flows into the first heat transfer tube 17a of the liquid-gas heat exchanger 17. As will be described later, in cooling operation, the refrigerant in the second heat transfer tube 17b is recovered by the compressor 11. Therefore, the refrigerant that flowed into the first heat transfer tube 17a flows out of the first heat transfer tube 17a without undergoing heat exchange. The refrigerant that flowed out of the first heat transfer tube 17a passes through the accumulator 26 and is again drawn into the compressor 11 from the first suction port 11e.

[0122] During cooling operation, the first valve 22 is closed, and therefore the refrigerant flowing through the liquid pipe 16 does not flow into the injection pipe 19. Furthermore, during cooling operation, the first valve 22 is closed, the second valve 23 is open, and the second expansion mechanism 20 is fully open. Therefore, when the compressor 11 operates, a portion of the injection pipe 19, the first heat transfer pipe 21 a and the second heat transfer pipe 21 b of the economizer heat exchanger 21, the second heat transfer pipe 17 b of the liquid-gas heat exchanger 17, and a portion of the branch pipe 18 are at low pressure. Specifically, the portion of the injection pipe 19 is the portion between the first valve 22 and the first suction section 11 e of the compressor 11. Specifically, the portion of the branch pipe 18 is the portion between the first valve 22 and the third valve 24.

[0123] As a result, when switching from heating operation to cooling operation, the refrigerant remaining in part of the injection pipe 19, the first heat transfer pipe 21a and the second heat transfer pipe 21b of the economizer heat exchanger 21, the second heat transfer pipe 17b of the liquid-gas heat exchanger 17, and part of the branch pipe 18 flows into the compressor 11 through the first suction section 11e and is recovered.

[0124] In this way, the liquid-gas heat exchanger 17 is configured so that the refrigerant does not flow through the second heat transfer pipe 17b during cooling operation. Also, the economizer heat exchanger 21 is configured so that the refrigerant does not flow through the second heat transfer pipe 17b during cooling operation.

[0125] (3-1-2) Water Circuit When the pump 31 starts operating, the water filled in the water circuit 30 is sucked in through the suction port of the pump 31 and then discharged from the discharge port of the pump 31.

[0126] The water flowing out of the pump 31 flows into the water flow path 15b of the second heat exchanger 15. The water that has flowed into the water flow path 15b exchanges heat with (is cooled by) the low-pressure refrigerant flowing through the refrigerant flow path 15a, and then flows out.

[0127] The water flowing out of the second heat exchanger 15 flows into the gas-liquid separator 32. In the gas-liquid separator 32, when the refrigerant leaks into the water side in the second heat exchanger 15, the refrigerant is recovered.

[0128] The water flowing out of the gas-liquid separator 32 flows into the third heat exchanger 33 without being heated by the heat source 34. The water flowing into the third heat exchanger 33 exchanges heat with the indoor air in the location where the third heat exchanger 33 is installed. This cools the air in the space to be air-conditioned.

[0129] The water that has exchanged heat with the air in the location where the third heat exchanger 33 is installed is sucked back into the pump 31 .

[0130] (3-2) Heating Operation Hereinafter, with reference to Fig. 4, a description will be given of the operation during heating operation of the refrigeration cycle apparatus 1. The heating operation shown in Fig. 4 is performed by the control unit 4, upon receiving a command for heating operation, controlling the operation of the compressor 11, the switching mechanism 12, the first expansion mechanism 14, the second expansion mechanism 20, the first fan 13a, the first valve 22, the second valve 23, the pump 31, the second fan 33a, the heat source 34, etc.

[0131] Specifically, the control unit 4 starts the compressor 11 and controls the rotation speed of the drive motor 11d of the compressor 11. The switching mechanism 12 is controlled to be in the first state. The opening degree of the first expansion mechanism 14 is controlled. The control unit 4 sets a target degree of subcooling of the refrigerant flowing out from the second end 15ab of the second heat exchanger 15, for example, based on a target outlet temperature of water flowing out from the water flow path 15b of the second heat exchanger 15. The control unit 4 then controls the opening degree of the first expansion mechanism 14 so that the degree of subcooling of the refrigerant flowing out from the second heat exchanger 15 approaches the target degree of subcooling. The control unit 4 controls the opening degree of the second expansion mechanism 20 so that the degree of superheat of the refrigerant flowing out from the second expansion mechanism 20 approaches a predetermined target degree of superheat. The first valve 22 is controlled to be in an open state. The second valve 23 is controlled to be in a closed state.

[0132] The control unit 4 also starts the operation of the pump 31. The heat source 34 is controlled not to operate.

[0133] (3-2-1) Refrigerant Circuit When the compressor 11 starts operating, low-pressure gas refrigerant in the refrigeration cycle is drawn through the first suction port 11e, and intermediate-pressure gas refrigerant in the refrigeration cycle is drawn through the second suction port 11f. The first compression element 11b compresses the low-pressure refrigerant drawn through the first suction port 11e to an intermediate pressure and discharges it to the second compression element 11c. The second compression element 11c compresses both the intermediate-pressure refrigerant discharged from the first compression element 11b and the intermediate-pressure refrigerant drawn through the second suction port 11f to a high pressure in the refrigeration cycle and discharges it as gas refrigerant to the discharge port 11g.

[0134] The high-pressure gas refrigerant flowing out from the discharge port 11g passes through the switching mechanism 12, in this order, via the first port P1 and the second port P2, and flows into the refrigerant flow path 15a of the second heat exchanger 15 from the first end 15aa. The refrigerant that flows into the second heat exchanger 15 exchanges heat with water flowing through the water flow path 15b, dissipating heat, becoming high-pressure liquid refrigerant and flowing out from the second end 15ab. In other words, the second heat exchanger 15 functions as a radiator.

[0135] The high-pressure refrigerant flowing out of the second heat exchanger 15 flows through the liquid pipe 16. Because the first valve 22 is open and the fourth valve 25 is provided downstream of the first branch portion 18a, the refrigerant flowing through the liquid pipe 16 flows into the injection pipe 19 at the first branch portion 18a without passing through the fourth valve 25. The refrigerant that has flowed into the injection pipe 19 passes through the first valve 22 at the first portion 19a, and then is divided into the second portion 19b of the injection pipe 19 and the branch pipe 18.

[0136] The refrigerant that has flowed into the second portion 19b of the injection pipe 19 is reduced in pressure to an intermediate pressure as it flows through the second expansion mechanism 20. The intermediate-pressure refrigerant flows into the first heat transfer pipe 21a of the economizer heat exchanger 21, exchanges heat with the refrigerant passing through the second heat transfer pipe 21b of the economizer heat exchanger 21, and then flows out of the first heat transfer pipe 21a.

[0137] Because the second valve 23 is closed, the refrigerant flowing out of the first heat transfer tube 21a does not flow into the third section 19c of the injection tube 19, but flows into the fourth section 19d of the injection tube 19. The refrigerant that has flowed into the fourth section 19d is again drawn into the compressor 11 from the second suction section 11f.

[0138] The refrigerant that flows into the branch pipe 18 flows into the second heat transfer pipe 21b of the economizer heat exchanger 21, exchanges heat with the refrigerant passing through the first heat transfer pipe 21a of the economizer heat exchanger 21, and flows out from the second heat transfer pipe 21b.

[0139] The refrigerant flowing out of the second heat transfer pipe 21b passes through the branch pipe 18 and flows into the second heat transfer pipe 17b of the liquid-gas heat exchanger 17. The refrigerant flowing into the second heat transfer pipe 17b exchanges heat with the refrigerant flowing through the first heat transfer pipe 17a of the liquid-gas heat exchanger 17, passes through the third valve 24, and flows into the liquid pipe 16 from the second branch part 18b.

[0140] The refrigerant that has flowed into the liquid pipe 16 is reduced in pressure to a low level as it passes through the first expansion mechanism 14, becoming a gas-liquid two-phase refrigerant and flowing into the first heat exchanger 13 from the first end 13aa. The refrigerant that has flowed into the first heat exchanger 13 exchanges heat with the outdoor air in the location where the first heat exchanger 13 is installed, evaporating, becoming a low-pressure gas refrigerant and flowing out from the second end 13ab. In other words, the first heat exchanger 13 functions as an evaporator.

[0141] The low-pressure refrigerant flowing out of the first heat exchanger 13 passes through the switching mechanism 12, in this order, via the fourth port P4 and the third port P3, and flows into the first heat transfer tube 17a of the liquid-gas heat exchanger 17. The refrigerant that has flowed into the first heat transfer tube 17a exchanges heat with the refrigerant passing through the second heat transfer tube 17b of the liquid-gas heat exchanger 17, and then flows out of the first heat transfer tube 17a. The refrigerant that has flowed out of the first heat transfer tube 17a passes through the accumulator 26 and is again drawn into the compressor 11 through the first suction port 11e.

[0142] In this way, the liquid-gas heat exchanger 17 and the economizer heat exchanger 21 are configured so that the refrigerant flows through them during heating operation.

[0143] (3-2-2) Water Circuit When the pump 31 starts operating, the water filled in the water circuit 30 is sucked in through the suction port of the pump 31 and then discharged from the discharge port of the pump 31.

[0144] The water flowing out of the pump 31 flows into the water flow path 15b of the second heat exchanger 15. The water that has flowed into the water flow path 15b exchanges heat with the low-pressure refrigerant flowing through the refrigerant flow path 15a (is heated), and then flows out.

[0145] The water flowing out of the second heat exchanger 15 flows into the gas-liquid separator 32. In the gas-liquid separator 32, when the refrigerant leaks into the water side in the second heat exchanger 15, the refrigerant is recovered.

[0146] The water flowing out of the gas-liquid separator 32 flows into the third heat exchanger 33 without being heated by the heat source 34. The water that flows into the third heat exchanger 33 exchanges heat with the indoor air in the location where the third heat exchanger 33 is installed. As a result, the air in the space to be air-conditioned is heated.

[0147] The water that has exchanged heat with the air in the location where the third heat exchanger 33 is installed is sucked back into the pump 31 .

[0148] (3-3) Defrosting Operation In the refrigeration cycle apparatus 1, when the index related to frost formation satisfies the first condition during heating operation, a defrosting operation is performed. Hereinafter, the operation of the refrigeration cycle apparatus 1 during the defrosting operation will be described with reference to Figs. 2 and 5 .

[0149] 5, the control unit 4 determines whether the index related to frost formation on the first heat exchanger 13 satisfies a first condition (step S1). Here, the control unit 4 acquires the outdoor air temperature detected by the outdoor temperature sensor 41 and compares the acquired outdoor air temperature with the first condition.

[0150] If the control unit 4 determines in step S1 that the first condition is not satisfied, it continues the heating operation (step S2). On the other hand, if the control unit 4 determines in step S1 that the first condition is satisfied, it determines that frost has formed on the first heat exchanger 13 and starts the defrosting operation (step S3).

[0151] In step S3, the control unit 4 switches the switching mechanism 12 to the second state, causing the flow of refrigerant in the refrigerant circuit 10 to be the same as that during cooling operation shown in Fig. 3. The control unit 4 also stops the first fan 13a.

[0152] Specifically, in the refrigerant circuit 10, low-pressure gas refrigerant in the refrigeration cycle is compressed by the compressor 11 to the high-pressure refrigerant in the refrigeration cycle, passes through the switching mechanism 12, and flows into the first heat exchanger 13. The high-pressure refrigerant that has flowed into the first heat exchanger 13 supplies heat to the first heat exchanger 13. This melts frost adhering to the first heat exchanger 13, and the first heat exchanger 13 is defrosted.

[0153] The high-pressure refrigerant flowing out of the first heat exchanger 13 passes through the first expansion mechanism 14 to become low-pressure gas-liquid two-phase refrigerant and flows into the refrigerant flow path 15a of the second heat exchanger 15. The low-pressure refrigerant that has flowed into the refrigerant flow path 15a exchanges heat with water flowing through the water flow path 15b, becomes low-pressure gas refrigerant, and flows out of the second heat exchanger 15. The low-pressure gas refrigerant that has flowed out of the second heat exchanger 15 passes through the switching mechanism 12 and is sucked into the compressor 11 again.

[0154] In the water circuit 30, the water that flows into the water flow path 15b of the second heat exchanger 15 exchanges heat with the low-pressure refrigerant flowing through the refrigerant flow path 15a and then flows out. This causes the water in the water flow path 15b to be cooled. For this reason, a maximum duration is set as an upper limit for the operation time of the defrosting operation. Therefore, the control unit 4 determines whether the duration of the defrosting operation has reached the maximum duration (step S4).

[0155] If the controller 4 determines in step S4 that the predetermined time has elapsed, the controller 4 ends the defrosting operation (step S5) and resumes the heating operation (step S2). In this case, the controller 4 switches the switching mechanism 12 to the first state.

[0156] On the other hand, if the control unit 4 determines in step S4 that the maximum duration has not been reached, it continues the defrosting operation. Note that if the control unit 4 determines that the frost on the first heat exchanger 13 has melted before the maximum duration is reached, it may terminate the defrosting operation and resume the heating operation (step S2).

[0157] (3-4) Reduced capacity operation In the refrigeration cycle apparatus 1, when the index related to frost formation satisfies the second condition during heating operation, reduced capacity operation is performed. Hereinafter, the operation of the refrigeration cycle apparatus 1 during reduced capacity operation will be described with reference to FIG.

[0158] 6, similarly to the frosting operation, the control unit 4 determines whether the frosting-related index satisfies a first condition (step S1). If the first condition is satisfied, the control unit 4 starts the defrosting operation (step S3).

[0159] Next, the control unit 4 determines whether the frost-related index satisfies the second condition (step S11). Here, the control unit 4 acquires the outdoor air temperature detected by the outdoor temperature sensor 41 and compares the acquired outdoor air temperature with the second condition.

[0160] If the control unit 4 determines in step S11 that the second condition is not satisfied, the control unit 4 continues the heating operation (step S2).

[0161] On the other hand, if the control unit 4 determines in step S11 that the second condition is satisfied, it starts reduced capacity operation because frost is likely to form on the first heat exchanger 13 (step S12). In this step S3, the flow of refrigerant in the refrigerant circuit 10 is maintained in the same manner as during heating operation.

[0162] In step S12, the capacity of the refrigeration cycle apparatus 1 is reduced. Here, the control unit 4 reduces the capacity of the compressor 11 or the target outlet water temperature. This suppresses a decrease in the temperature of the first heat exchanger 13.

[0163] Also, in step S12, the control unit 4 activates the heat source 34 to heat the water in the water circuit 30. In this state, the control unit 4 determines whether the amount of water heated by the refrigeration cycle device 1 is greater than the amount of water heated by the heat source 34 (step S13).

[0164] In step S13, if the control unit 4 determines that the amount of water heated by the refrigeration cycle device 1 is equal to or less than the amount of water heated by the heat source 34, it switches to defrosting operation (step S3). On the other hand, in step S13, if the control unit 4 determines that the amount of water heated by the refrigeration cycle device 1 is greater than the amount of water heated by the heat source 34, it continues reduced capacity operation (step S14).

[0165] During reduced performance operation, the process returns to step S1 at a predetermined timing to determine whether the first condition is satisfied. Therefore, when the first condition is satisfied during reduced performance operation (step S1), the control unit 4 switches to defrosting operation. Furthermore, when the first condition and the second condition are no longer satisfied during reduced performance operation, the control unit 4 resumes heating operation (step S2).

[0166] As described above, in the refrigeration cycle apparatus 1 of this embodiment, there are cases where the reduced capacity operation is performed and then the operation is switched to the defrosting operation, and cases where the defrosting operation is performed without performing the reduced capacity operation.

[0167] (4) Features (4-1) The refrigeration cycle device 1 of this embodiment includes a refrigerant circuit 10 and a control unit 4. The refrigerant circuit 10 has a first heat exchanger 13. The first heat exchanger 13 exchanges heat between outdoor air and a refrigerant. The refrigerant circulates through the refrigerant circuit 10. The control unit 4 performs a defrosting operation and a reduced capacity operation. The defrosting operation is an operation that melts frost that has formed on the first heat exchanger 13. The reduced capacity operation is an operation that reduces capacity. The control unit performs the reduced capacity operation when an index related to frost formation satisfies a second condition, and performs the defrosting operation when the index related to frost formation satisfies a first condition during the reduced capacity operation.

[0168] According to the refrigeration cycle apparatus 1 of this embodiment, if the frost-related index satisfies a second condition before a defrosting operation to melt frost formed on the first heat exchanger 13 that exchanges heat with outdoor air, a reduced-capacity operation to reduce the capacity of the refrigeration cycle apparatus 1 is performed. In other words, when the second condition is met, indicating that frost is likely to form on the first heat exchanger 13, the reduced-capacity operation is performed. By performing this reduced-capacity operation, frost formation on the first heat exchanger 13 can be suppressed. Therefore, the refrigeration cycle apparatus 1 can reduce the frequency of defrosting operations, thereby improving comfort.

[0169] (4-2) In the refrigeration cycle device 1 of this embodiment, the refrigerant preferably contains R290.

[0170] Because R290 is a low-pressure refrigerant, the size of the first heat exchanger 13 is large, which requires a long time for defrosting operation. However, in the refrigeration cycle apparatus 1 of this embodiment, even when a refrigerant containing R290 is used, frost formation in the first heat exchanger 13 can be suppressed by performing reduced capacity operation. Therefore, even when a refrigerant containing R290 is used, frost formation in the first heat exchanger 13 can be suppressed by performing reduced capacity operation, which reduces the frequency of defrosting operation. Therefore, the efficiency of the refrigeration cycle apparatus 1 using a refrigerant containing R290 can be improved.

[0171] (4-3) In the refrigeration cycle apparatus 1 of this embodiment, the first heat exchanger 13 is preferably a microchannel heat exchanger.

[0172] Microchannel heat exchangers are more susceptible to frosting than plate heat exchangers, etc. However, in the refrigeration cycle apparatus 1 of this embodiment, even if such a microchannel heat exchanger is used as the first heat exchanger 13 that exchanges heat with outdoor air, frosting on the first heat exchanger 13 can be suppressed by performing reduced capacity operation. Therefore, the refrigeration cycle apparatus 1 of this embodiment can suitably use a microchannel heat exchanger as the first heat exchanger 13.

[0173] (4-4) In the refrigeration cycle apparatus 1 of this embodiment, preferably, the refrigerant circuit 10 further includes a second heat exchanger 15. The second heat exchanger 15 exchanges heat between the refrigerant and water. The refrigeration cycle apparatus 1 further includes a water circuit 30 and a heat source 34. The water flowing through the second heat exchanger 15 circulates through the water circuit 30. The heat source 34 heats the water.

[0174] In this case, when the temperature of the water in the water circuit 30 falls below the target hot water outlet temperature due to a decrease in the amount of water heated by the refrigerant during reduced capacity operation, for example, the heat source 34 can heat the water. This makes it possible to suppress frost formation and a decrease in the water temperature.

[0175] (4-5) In the refrigeration cycle apparatus 1 of the present embodiment, preferably, the refrigerant circuit 10 further includes a compressor 11. The control unit 4 performs a reduced capacity operation by reducing the capacity of the compressor 11 or by lowering the target hot water outlet temperature.

[0176] Here, the capacity of the compressor 11 is reduced or the target hot water outlet temperature is reduced, thereby reducing the capacity of the refrigeration cycle device 1. Therefore, a refrigeration cycle device 1 that suppresses frost formation can be easily realized.

[0177] (4-6) In the refrigeration cycle apparatus 1 of this embodiment, the control unit 4 preferably operates the heat source 34 during reduced capacity operation.

[0178] Here, even if the temperature of the water heated by the refrigerant in the second heat exchanger 15 becomes lower than the target hot water outlet temperature due to a decrease in the capacity of the refrigeration cycle apparatus 1 during reduced capacity operation, the heat source 34 heats the water. In this way, the capacity deficiency caused by the reduced capacity operation is compensated for by the heat source 34. Therefore, it is possible to easily realize a refrigeration cycle apparatus 1 that suppresses frost formation while suppressing a decrease in the water temperature.

[0179] (4-7) In the refrigeration cycle apparatus 1 of this embodiment, preferably, during reduced capacity operation, the amount of water heated by the refrigeration cycle apparatus 1 is greater than the amount of water heated by the heat source.

[0180] Here, during reduced capacity operation, the amount of water heated by the heat source 34 is not reversed to the amount of water heated by the refrigeration cycle device 1, so that a decrease in the efficiency of the refrigeration cycle device 1 can be suppressed.

[0181] (4-8) In the refrigeration cycle device 1 of this embodiment, the second condition is preferably that the outside air temperature is not less than -10°C and not more than 7°C.

[0182] Here, since the outdoor air temperature is used as the second condition for control, it is easy to control the reduced capacity operation.

[0183] (4-9) In the refrigeration cycle apparatus 1 of this embodiment, the maximum duration of the defrosting operation is preferably shorter than the maximum duration of the reduced capacity operation.

[0184] In this case, by continuing the reduced capacity operation, the frequency of defrosting operation is reduced and the maximum duration of defrosting operation is shortened even if defrosting operation is performed, thereby reducing the time during which comfort is reduced due to defrosting operation.

[0185] (4-10) In the refrigeration cycle apparatus 1 of this embodiment, preferably, when the first condition is satisfied during reduced capacity operation, the control unit 4 switches to defrosting operation.

[0186] Here, the control unit 4 performs the defrosting operation when the first condition is satisfied even during the reduced capacity operation, thereby making it possible to suppress a decrease in the efficiency of the refrigeration cycle apparatus 1.

[0187] (5) Modifications (5-1) Modification 1 (5-1-1) Overview In the above embodiment, the control unit 4 operates the heat source only during reduced performance operation, but this is not limited to this. In this modification, the control unit 4 operates the heat source 34 during defrosting operation and reduced performance operation. In detail, the control unit 4 may operate the heat source 34 at the start of defrosting operation, or may operate the heat source 34 after a predetermined time has elapsed since the start of defrosting operation.

[0188] (5-1-2) Features As described above, in the refrigeration cycle apparatus 1 of this modified example, the control unit 4 operates the heat source 34 during defrosting operation. Here, even if the water temperature drops during defrosting operation, the heat source 34 heats the water, thereby preventing a decrease in comfort.

[0189] (5-2) Modification 2 In the above embodiment, the heat source 34 is a heater that can be switched on or off, but this is not limiting. In this modification, the output of the heat source 34 is variable. Specifically, the heat source 34 is a heater that can output at two or more levels.

[0190] Furthermore, here, the control unit 4 controls the output of the heat source 34 during reduced capacity operation so that it is greater than the output of the heat source 34 during defrosting operation. Then, when the amount of water heated by the heat source 34 is reversed to the amount of water heated by the refrigeration cycle apparatus 1, the control unit 4 may switch from reduced capacity operation to defrosting operation regardless of the first condition.

[0191] (5-3) Modification 3 In the above embodiment, the water circuit 30 has the heat source 34, but the heat source 34 does not have to be part of the water circuit 30. In this case, the heat source 34 may be provided in the utilization machine 3 or the heat source machine 2.

[0192] Furthermore, the number of heat sources 34 included in the refrigeration cycle apparatus 1 is not limited to one, and may be multiple. In this case, the multiple heat sources 34 may be arranged in each of the utilization unit 3 and the heat source unit 2, or may be arranged in only one of them.

[0193] (5-4) Modification 4 (5-4-1) Overview In the above embodiment, the second condition is a predetermined outdoor air temperature, but this is not limiting. In this modification, the second condition is a state in which the capacity required based on the outdoor air temperature exceeds the capacity at which the first heat exchanger 13 can operate without frosting. Note that the "capacity at which the first heat exchanger 13 can operate without frosting" refers to the maximum capacity at which heating operation can be performed without frost forming on the first heat exchanger 13. This will be described below with reference to FIG. 7.

[0194] Fig. 7 shows an example of the relationship between the outside air temperature and the capacity of the refrigeration cycle apparatus 1. In Fig. 7, line L1 represents the capacity of the refrigeration cycle apparatus 1 required based on the outside air temperature, and line L2 represents the capacity of the refrigeration cycle apparatus 1 at which the refrigeration cycle apparatus 1 can operate without frosting the first heat exchanger 13. As shown in Fig. 7, the slope of line L1, which indicates the capacity required based on the outside air temperature, is different from the slope of line L2, which indicates the capacity at which the first heat exchanger 13 can operate without frosting.

[0195] The second condition in this modification is a state in which the capacity of line L1 exceeds the capacity of line L2. In this state, the refrigeration cycle device 1 is producing capacity despite the low outside air temperature, so the first heat exchanger 13 is cooled and frost is likely to form on the first heat exchanger 13. Here, the second condition is when the outside air temperature is equal to or lower than a predetermined temperature (−3° C. in FIG. 7 ) and exceeds a certain capacity (7 kW in FIG. 7 ).

[0196] In this modification, the control unit 4 operates the heat source 34 to compensate for the capacity of the region R1 in Fig. 7. Specifically, the control unit 4 controls the heat source 34 so that the heat source 34 absorbs the difference between the capacity of the line L1 and the capacity of the line L2 for a given outside air temperature.

[0197] (5-4-2) Features In the refrigeration cycle device 1 of this modified example, the second condition is a state in which the capacity required based on the outside air temperature exceeds the capacity at which the first heat exchanger 13 can operate without frosting.

[0198] When the capacity required based on the outdoor air temperature exceeds the capacity to prevent frost formation, the outdoor air temperature is low, and the capacity of the refrigeration cycle device 1 is high. In this case, the first heat exchanger 13 is cooled, making it more likely to form frost. Therefore, this state is considered to satisfy the second condition, and by performing reduced capacity operation, frost formation can be effectively suppressed.

[0199] (5-5) Modification 5 (5-5-1) Overview In the above embodiment, the second condition is a predetermined outside air temperature, but this is not limiting. In this modification, the second condition is that the evaporation temperature of the refrigerant in the first heat exchanger 13 is lower than the dew point temperature by a predetermined temperature or more, and the outside air temperature is 2°C or less. The following description will be given with reference to FIG. 8.

[0200] Fig. 8 shows an example of the relationship between the outside air temperature, the dew point temperature, and the evaporation temperature of the refrigeration cycle apparatus 1. In Fig. 8, line L3 represents the dew point temperature under standard temperature conditions for the outside air temperature, and line L4 represents the lower limit of the evaporation temperature at which heating operation can be performed without frost forming on the first heat exchanger 13. The evaporation temperature is the evaporation temperature of the refrigerant flowing out from the second end 13ab of the first heat exchanger 13. The standard temperature condition is a condition in which the wet-bulb temperature is 1°C lower than the dry-bulb temperature.

[0201] The second condition in this modification is a state in which the evaporation temperature of line L4 is lower than the dew point temperature of line L3 by a predetermined temperature or more when the outside air temperature is 2° C. or less. In this state, the outside air temperature is low and the evaporation temperature of first heat exchanger 13 is low, so that first heat exchanger 13 cools and frost is likely to form on first heat exchanger 13. In this case, the second condition is a state in which the outside air temperature is 2° C. or less and the evaporation temperature is lower than the dew point temperature by a predetermined temperature or more (2° C. in FIG. 8 ).

[0202] In this modification, the control unit 4 operates the heat source 34 to compensate for the evaporation temperature in region R2 in Fig. 8. Specifically, the control unit 4 controls the heat source 34 so that the heat source 34 compensates for the evaporation temperature of line L3 for a predetermined outside air temperature (2°C from the dew point temperature in Fig. 8). In other words, the control unit 4 controls the heat source 34 so that the evaporation temperature of the first heat exchanger 13 is within a range of 2°C from the dew point temperature.

[0203] (5-5-2) Features As described above, in the refrigeration cycle device 1 of this modified example, the second condition is that the evaporation temperature of the refrigerant in the first heat exchanger 13 is lower than the dew point temperature by a predetermined temperature or more, and the outside air temperature is 2°C or less.

[0204] When the evaporation temperature is lower than the dew point temperature by a predetermined temperature or more and the outside air temperature is low, such as 2° C. or less, the first heat exchanger 13 is cooled, which makes it more likely to form frost. Therefore, this state is considered to satisfy the second condition, and therefore, by performing reduced capacity operation, it is possible to effectively suppress frost formation.

[0205] (5-6) Modification 6 In the above embodiment, reduced capacity operation is performed by reducing the compressor capacity or the target hot water outlet temperature, but this is not limited to this. The reduced capacity operation may be performed by performing other control or multiple controls during heating operation to reduce capacity. In this modification, reduced capacity operation is performed by controlling to lower the evaporation temperature of the first heat exchanger 13.

[0206] (5-7) Modification 7 In the above embodiment, the circulation of the refrigerant in the refrigerant circuit 10 during the defrosting operation is the same as that during the cooling operation, but this is not limiting as long as the refrigerant flows from the compressor 11 to the first heat exchanger 13 and the first heat exchanger 13 functions as a radiator during the defrosting operation. The flow of the refrigerant in the refrigerant circuit 10 during the defrosting operation may be different from that during the cooling operation.

[0207] (5-8) Modification 8 In the above embodiment, the refrigeration cycle apparatus 1 including one third heat exchanger 33 has been described as an example, but is not limited to this. The refrigeration cycle apparatus 1 may include a plurality of third heat exchangers 33.

[0208] In this modification, the multiple third heat exchangers 33 are connected in parallel to each other with respect to the second heat exchanger 15. There are also multiple utilization units 3 that include the third heat exchangers 33. The multiple utilization units 3 may or may not be capable of individually performing cooling or heating operation.

[0209] (5-9) Modification 9 In the above embodiment, in the second heat exchanger 15, the refrigerant flowing through the refrigerant circuit 10 exchanges heat with the water flowing through the water circuit 30, but this is not limited to this. In this modification, the refrigerant flowing through the refrigerant circuit 10 may exchange heat with the air in the target space. In this case, the water circuit 30 is omitted, and the second heat exchanger 15 is disposed in the target space.

[0210] (5-10) Modification 10 In the above embodiment, the refrigeration cycle apparatus 1 includes the refrigerant circuit 10 and the water circuit 30, but is not limited to this. In this modification, the refrigeration cycle apparatus includes a medium circuit through which a medium circulates, instead of the water circuit through which water circulates. The medium includes a refrigerant and a heat medium. Here, carbon dioxide circulates in the medium circuit. Therefore, the carbon dioxide that has exchanged heat with the refrigerant in the second heat exchanger 15 heats or cools the air in the target space in the third heat exchanger 33.

[0211] (5-11) Modification 11 In the above embodiment, a flammable refrigerant is used as the refrigerant, but this is not limited to this. In this modification, a low-pressure refrigerant having a pressure of more than 0.08 MPa and not more than 0.8 MPa at a condensation temperature of 25°C is used as the refrigerant.

[0212] Although the embodiments of the present disclosure have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the present disclosure as defined in the claims.

[0213] REFRIGERATION CYCLE DEVICE 1 : REFRIGERATION CYCLE DEVICE 4 : CONTROL UNIT 10 : REFRIGERATOR 11 : COMPRESSOR 13 : FIRST HEAT EXCHANGER 15 : SECOND HEAT EXCHANGER 30 : WATER CIRCUITS 31 : PUMP 32 : GAS-LIQUID SEPARATOR 33 : THIRD HEAT EXCHANGER 33a : SECOND FAN 34 : HEAT SOURCE

[0214] JP 2018-91579 A

Claims

1. It has a first heat exchanger (13) that performs heat exchange between the outdoor air and the refrigerant, and a refrigerant circuit (10) through which the refrigerant circulates, A control unit (4) performs a defrosting operation to melt frost accumulated on the first heat exchanger and a capacity reduction operation to lower its capacity, Equipped with, The control unit performs the reduced-capacity operation when the indicator for frost formation satisfies the second condition, and performs the defrosting operation during the reduced-capacity operation when the indicator for frost formation satisfies the first condition, in a refrigeration cycle device (1).

2. The refrigerant includes R290, The refrigeration cycle apparatus according to claim 1.

3. The first heat exchanger is a microchannel heat exchanger. A refrigeration cycle apparatus according to claim 1 or 2.

4. The refrigerant circuit further includes a second heat exchanger (15) that performs heat exchange between the refrigerant and water. The water (30) that flows through the second heat exchanger circulates, A heat source (34) for heating the water, Furthermore, A refrigeration cycle apparatus according to claim 1 or 2.

5. The refrigerant circuit further includes a compressor (11), The control unit performs the reduced-capacity operation by reducing the capacity of the compressor or by lowering the target hot water outlet temperature. The refrigeration cycle apparatus according to claim 4.

6. The control unit activates the heat source during the reduced-capacity operation. The refrigeration cycle apparatus according to claim 4.

7. During the reduced-capacity operation, the amount of water heated by the refrigeration cycle device is greater than the amount of water heated by the heat source. The refrigeration cycle apparatus according to claim 6.

8. The control unit activates the heat source during the defrosting operation. The refrigeration cycle apparatus according to claim 4.

9. The second condition is that the outside temperature is between -10°C and 7°C. A refrigeration cycle apparatus according to claim 1 or 2.

10. The second condition is a state in which the capacity required based on the outside air temperature exceeds the capacity that allows the first heat exchanger to operate without frost formation. A refrigeration cycle apparatus according to claim 1 or 2.

11. The second condition is that the evaporation temperature of the refrigerant in the first heat exchanger is at least a predetermined temperature lower than the dew point temperature, and the ambient temperature is 2°C or less. A refrigeration cycle apparatus according to claim 1 or 2.

12. The maximum duration of the defrosting operation is shorter than the maximum duration of the capacity reduction operation. A refrigeration cycle apparatus according to claim 1 or 2.

13. The control unit switches to the defrosting operation when the first condition is met during the reduced capacity operation. A refrigeration cycle apparatus according to claim 1 or 2.