Refrigeration cycle apparatus

Abstract

A refrigeration cycle apparatus includes a refrigerant circuit and circuitry that implements a control unit. The refrigerant circuit includes a first heat exchanger. The first heat exchanger exchanges heat between outdoor air and a refrigerant. The refrigerant circulates in the refrigerant circuit. The control unit controls a defrosting operation to melt frost adhering to the first heat exchanger and a capacity reduction operation to reduce capacity. The control unit further controls the capacity reduction operation when an index related to frosting satisfies the second condition, and performs the defrosting operation when the index related to the frosting satisfies the first condition during the capacity reduction operation.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application is based on, and is a continuation of, PCT application PCT / JP 2023 / 035414 filed Sep. 28, 2023, the entire contents of which being incorporated herein by reference.TECHNICAL FIELD

[0002] The present disclosure relates to a refrigeration cycle apparatus.BACKGROUND ART

[0003] Patent Literature 1 (JP 2018-091579 A) discloses that air heated by a humidifying heater of a humidifying unit flows to an air blow-out portion disposed in the vicinity of an outdoor heat exchanger under a predetermined condition that frost needs to be reduced during heating operation.SUMMARY

[0004] A refrigeration cycle apparatus according to a first aspect includes a refrigerant circuit and circuitry that implements a control unit. The refrigerant circuit includes a first heat exchanger. The first heat exchanger exchanges heat between outdoor air and a refrigerant. The refrigerant circulates in the refrigerant circuit. The control unit controls a defrosting operation to melt frost adhering to the first heat exchanger and a capacity reduction operation to reduce capacity. The control unit further controls the capacity reduction operation when an index related to frosting satisfies the second condition, and performs the defrosting operation when the index related to the frosting satisfies the first condition during the capacity reduction operation.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. 1 is a schematic configuration diagram of a refrigeration cycle apparatus according to an embodiment of the present disclosure.

[0006] FIG. 2 is a control block diagram of the refrigeration cycle apparatus.

[0007] FIG. 3 is a diagram illustrating an operation (a flow of a refrigerant) in a cooling operation of the refrigeration cycle apparatus.

[0008] FIG. 4 is a diagram illustrating an operation (a flow of a refrigerant) in a heating operation of the refrigeration cycle apparatus.

[0009] FIG. 5 is a diagram illustrating a control flow in a defrosting cooling operation of the refrigeration cycle apparatus.

[0010] FIG. 6 is a diagram illustrating a control flow in a capacity reduction operation of the refrigeration cycle apparatus.

[0011] FIG. 7 is a diagram for explaining a second condition of a fourth modification.

[0012] FIG. 8 is a diagram for explaining the second condition of a fifth modification.DESCRIPTION OF EMBODIMENTS(1) Overall Configuration

[0013] A refrigeration cycle apparatus 1 according to an embodiment of the present disclosure illustrated in FIG. 1 is an apparatus that causes a refrigerant circuit 10 to perform a vapor compression refrigeration cycle to cool or heat water circulating in a water circuit 30, and uses the water for cooling and heating a target space.

[0014] The refrigeration cycle apparatus 1 includes a heat source device 2 and a utilization device 3. The heat source device 2 and the utilization device 3 are connected to each other. In the present embodiment, the number of the heat source device 2 is one, and the number of the utilization device 3 is one.

[0015] In addition, the refrigeration cycle apparatus 1 includes the refrigerant circuit 10, the water circuit 30, and a control unit 4. A refrigerant circulates in the refrigerant circuit 10. The water circulates in the water circuit30. The refrigerant circuit 10 and the water circuit 30 are connected to each other. The control unit 4 performs a heating operation, a cooling operation, a defrosting operation, and a capacity reduction operation. The term “control unit”, as used herein, corresponds with a controller that contains circuitry (one or more circuits having at least one of programmable circuitry, such as one or more CPUs, and / or hardwired circuitry, such as an ASIC) configured by execution of code or hardwired connections to perform the described functions.(2) Detailed Configuration(2-1) Refrigerant Circuit

[0016] The refrigerant circuit 10 is a circuit in which a refrigerant circulates during normal operation such as heating operation and cooling operation, and during operation as a countermeasure against frosting of a first heat exchanger 13 (described later) such as defrosting operation and capacity reduction operation.

[0017] The refrigerant circuit 10 is filled with the refrigerant. The refrigerant is not particularly limited, but is a flammable refrigerant here. The flammable refrigerant is a refrigerant having flammability. The flammable refrigerant is, for example, a hydrocarbon-based refrigerant such as R1234yf, R1234ze, and R32, and here, a refrigerant classified as highly flammable (A3) according to ISO817, and includes R290 (propane) in the present embodiment. The refrigerant may be a single refrigerant of R290 or a mixed refrigerant of R290 and another refrigerant. In addition, the refrigerant includes a refrigerating machine oil. The refrigerating machine oil is, for example, polyalkylene glycol (PAG) or the like.

[0018] 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.(2-1-1) Compressor

[0019] 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 sucks the low-pressure refrigerant in the refrigeration cycle, compresses the refrigerant to an intermediate pressure in the refrigeration cycle, then further compresses an intermediate-pressure refrigerant to the high pressure, and discharges the refrigerant.

[0020] 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.

[0021] The casing 11a accommodates the first compression element 11b and the second compression element 11c. The first compression element 11b and the second compression element 11c are coupled to a single drive shaft (not illustrated). During operation of the compressor 11, the 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 uniaxial two-stage compression structure.

[0022] The first suction portion 11e sucks the low-pressure refrigerant from the refrigerant circuit 10. The second suction portion 11f sucks the intermediate-pressure refrigerant from the refrigerant circuit 10. The discharge portion 11g discharges a high-pressure refrigerant to the refrigerant circuit 10. The second suction portion 11f is an example of a suction portion.

[0023] The second suction portion 11f has a check valve (not illustrated) that allows inflow of the refrigerant from an outside to an inside of the casing 11a and regulates outflow of the refrigerant from the inside to the outside of the casing 11a.

[0024] The first compression element 11b compresses the refrigerant sucked by the first suction portion 11e to the intermediate pressure and discharges the refrigerant 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 sucked by the second suction portion 11f to the high pressure, and discharges the compressed refrigerants to the discharge portion 11g.

[0025] Note that a structure of the compressor 11 is not limited to the uniaxial two-stage compression structure. The structure of the compressor 11 may include, for example, a compression element driven by another drive motor.(2-1-2) Switching Mechanism

[0026] The switching mechanism 12 switches a refrigerant flow direction 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.

[0027] The switching mechanism 12 is switched between a first state (state indicated by a solid line in FIG. 1) and a second state (state indicated by a broken line in FIG. 1). In the first state, the switching mechanism 12 causes the first port P1 and the second port P2 to communicate with each other, and causes the third port P3 and the fourth port P4 to communicate with each other. In the second state, the switching mechanism 12 causes the first port P1 and the fourth port P4 to communicate with each other, and causes the second port P2 and the third port P3 to communicate with each other.

[0028] The switching mechanism 12 is not limited to the four-way switching valve, and may be configured by, for example, combining a plurality of electromagnetic valves and refrigerant flow paths.(2-1-3) First Heat Exchanger

[0029] The first heat exchanger 13 is an air heat exchanger. The first heat exchanger 13 exchanges heat between the refrigerant flowing inside and outside air (outdoor air) sent from a first fan 13a. The first heat exchanger 13 is a heat exchanger that functions as a radiator for the refrigerant during the cooling operation, and functions as an evaporator for the refrigerant during the heating operation. As the first heat exchanger 13, a heat exchanger suitable for an application such as a cross-fin heat exchanger or a microchannel heat exchanger is employed. In the present embodiment, the first heat exchanger 13 is the microchannel heat exchanger.

[0030] The first heat exchanger 13 has a refrigerant flow path (not illustrated). The refrigerant flow path of the first heat exchanger 13 is provided in the refrigerant circuit 10.

[0031] Hereinafter, for convenience of description, in the heating operation, an end portion of the refrigerant flow path of the first heat exchanger 13 into which the refrigerant flows is referred to as a first end 13aa, and an end portion of the refrigerant flow path from which the refrigerant flows out is referred to as a second end 13ab. (2-1-4) First Expansion Mechanism

[0032] The first expansion mechanism 14 decompresses the passing refrigerant 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.(2-1-5) Second Heat Exchanger

[0033] The second heat exchanger 15 is a water heat exchanger. In the present 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 is a heat exchanger that functions as the evaporator for the refrigerant during the cooling operation, and functions as the radiator for the refrigerant during the heating operation. As the second heat exchanger 15, a heat exchanger suitable for the application such as a plate heat exchanger is employed.

[0034] 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 having exchanged heat with the refrigerant circulates through the water circuit 30 to heat or cool the air in the target space.

[0035] Hereinafter, for convenience of description, in the heating operation, an end portion of the refrigerant flow path 15a into which the refrigerant flows is referred to as a first end 15aa, and an end portion of the refrigerant flow path 15a from which the refrigerant flows out is referred to as a second end 15ab. (2-1-6) Liquid Pipe

[0036] The liquid pipe 16 connects the radiator (the first heat exchanger 13 during the cooling operation and the second heat exchanger 15 during the heating operation) and the evaporator (the second heat exchanger 15 during the cooling operation and the first heat exchanger 13 during the heating operation). Here, the liquid pipe 16 connects the first end 13aa of the refrigerant flow path of the first heat exchanger 13 and the second end 15ab of the refrigerant flow path 15a of the second heat exchanger 15.(2-1-7) Liquid-Gas Heat Exchanger

[0037] The liquid-gas heat exchanger 17 exchanges heat between the refrigerant flowing from the radiator (the second heat exchanger 15 during the heating operation) to the evaporator (the first heat exchanger 13 during the heating operation) and the refrigerant flowing from the evaporator to the compressor 11. The liquid-gas heat exchanger 17 is a precooling heat exchanger that cools the refrigerant flowing from the radiator to the evaporator. The liquid-gas heat exchanger 17 includes a first heat transfer tube 17a and a second heat transfer tube 17b.

[0038] The refrigerant flowing from the evaporator to the first suction portion 11e of the compressor 11 passes through the first heat transfer tube 17a. One end of the first heat transfer tube 17a is connected to the third port P3 of the switching mechanism 12. The other end of the first heat transfer tube 17a is connected to the first suction portion 11e of the compressor 11 via the accumulator 26.

[0039] The refrigerant flowing from the radiator to the evaporator passes through the second heat transfer tube 17b. Both ends of the second heat transfer tube 17b are connected to the branch pipe 18.

[0040] In the present embodiment, during the heating operation, the liquid-gas heat exchanger 17 exchanges heat between the refrigerant passing through the first heat transfer tube 17a and the refrigerant passing through the second heat transfer tube 17b. On the other hand, during the cooling operation, the liquid-gas heat exchanger 17 does not exchange heat between the refrigerant passing through the first heat transfer tube 17a and the refrigerant passing through the second heat transfer tube 17b. Specifically, the refrigerant flows through the first heat transfer tube 17a and the second heat transfer tube 17b during the heating operation, and does not flow through the second heat transfer tube 17b during the cooling operation.(2-1-8) Branch Pipe

[0041] The branch pipe 18 is a refrigerant flow path that branches from between the second heat exchanger 15 and the first expansion mechanism 14 in the liquid pipe 16 and is connected to the second heat transfer tube 17b of the liquid-gas heat exchanger 17. In other words, the second heat transfer tube 17b is provided in the middle of the branch pipe 18.

[0042] One end of the second heat transfer tube 17b is connected to the branch pipe 18 branching from the second heat exchanger 15 side. The other end of the second heat transfer tube 17b is connected to the branch pipe 18 branching from the first expansion mechanism 14 side.

[0043] Hereinafter, for convenience of description, a portion where the branch pipe 18 branches from the second heat exchanger 15 side in the liquid pipe 16 may be referred to as a first branch portion 18a, and a portion where the branch pipe 18 branches from the first expansion mechanism 14 side in the liquid pipe 16 may be referred to as a second branch portion 18b. (2-1-9) Injection Pipe

[0044] The injection pipe 19 branches a part 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 the refrigerant to the compressor 11. Here, the injection pipe 19 branches from the liquid pipe 16 and is connected to the first suction portion 11e and the second suction portion 11f of the compressor 11. Therefore, the injection pipe 19 can cause the refrigerant to join the low-pressure refrigerant of the compressor 11 and cause the refrigerant to join the intermediate-pressure refrigerant between the high pressure and the low pressure of the compressor 11.

[0045] The injection pipe 19 branches from between the radiator (the second heat exchanger 15 in FIG. 1) and the economizer heat exchanger 21. In the present embodiment, the injection pipe 19 branches from between the second heat exchanger 15 and the economizer heat exchanger 21 in a refrigerant flow during the heating operation. In other words, the injection pipe 19 branches from a position that is downstream of the radiator and upstream of the economizer heat exchanger 21 during the heating operation.

[0046] In FIG. 1, the injection pipe 19 has a first portion 19a, a second portion 19b, a third portion 19c, and a fourth portion 19d.

[0047] The first portion 19a branches from the liquid pipe 16 and is shared with the branch pipe 18. Here, the first portion 19a branches from the first branch portion 18a in the liquid pipe 16.

[0048] The second portion 19b causes the refrigerant flowing through the first portion 19a to flow into a first heat transfer tube 21a (described later) of the economizer heat exchanger 21. The second portion 19b is connected to an end portion of the first portion 19a on a side opposite to a branch portion (here, the first branch portion 18a) from the liquid pipe 16. The second portion 19b is provided with the first heat transfer tube 21a of the economizer heat exchanger 21 in the middle.

[0049] The third portion 19c causes the refrigerant flowing through the first heat transfer tube 21a of the economizer heat exchanger 21 to flow into the first suction portion 11e of the compressor 11. The third portion 19c connects an end portion of the second portion 19b at a side opposite to the first portion 19a and the first suction portion 11e of the compressor 11.

[0050] The fourth portion 19d causes the refrigerant flowing through the first heat transfer tube 21a of the economizer heat exchanger 21 to flow into the second suction portion 11f of the compressor 11. The fourth portion 19d connects the end portion of the second portion 19b at the side opposite to the first portion 19a and the second suction portion 11f of the compressor 11.(2-1-10) Second Expansion Mechanism

[0051] The second expansion mechanism 20 decompresses the refrigerant passing through the injection pipe 19 to the intermediate pressure. The second expansion mechanism 20 is provided between the connection portion with the first portion 19a and the economizer heat exchanger 21 in the second portion 19b of the injection pipe 19.

[0052] The second expansion mechanism 20 is, for example, an on / off valve such as a solenoid valve or a flow rate control valve such as the electric expansion valve. In the present embodiment, the second expansion mechanism 20 is the electric expansion valve.(2-1-11) Economizer Heat Exchanger

[0053] 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 flowing from the radiator to the evaporator. The economizer heat exchanger 21 has the first heat transfer tube 21a and a second heat transfer tube 21b. 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.

[0054] The refrigerant flowing through the injection pipe 19 passes through the first heat transfer tube 21a. The first heat transfer tube 21a is provided in the injection pipe 19. One end of the first heat transfer tube 21a is connected to the second expansion mechanism 20 via the injection pipe 19. The other end of the first heat transfer tube 21a is connected to the first suction portion 11e and the second suction portion 11f of the compressor 11 via the injection pipe 19.

[0055] The refrigerant flowing through the branch pipe 18 passes through the second heat transfer tube 21b. The second heat transfer tube 21b is provided in the branch pipe 18. One end of the second heat transfer tube 21b is connected to the first valve 22 via the branch pipe 18. The other end of the second heat transfer tube 21b is connected to the second heat transfer tube 17b of the liquid-gas heat exchanger 17 via the branch pipe 18.

[0056] In the present embodiment, during the 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 the 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 the heating operation, and does not flow through the first heat transfer tube 21a and the second heat transfer tube 21b during the cooling operation.(2-1-12) First Valve

[0057] The first valve 22 regulates the flow of the 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 is switched between an open state and a closed state.

[0058] The first valve 22 is in an open state in the heating operation and is in a closed state in the cooling operation.(2-1-13) Second Valve

[0059] The second valve 23 regulates the refrigerant flowing through the injection pipe 19 at the third portion 19c of the injection pipe 19 from flowing into the first suction portion 11e of the compressor 11. The second valve 23 is an on-off valve that is switched between an open state and a closed state.

[0060] The second valve 23 is in a closed state in the heating operation and is in an open state in the cooling operation.(2-1-14) Third Valve

[0061] The third valve 24 regulates the flow of the 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 the refrigerant from the second branch portion 18b to the second heat transfer tube 17b and allows the flow of the refrigerant from the second heat transfer tube 17b to the second branch portion 18b. (2-1-15) Fourth Valve

[0062] The fourth valve 25 regulates the flow of the 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 the refrigerant from the first branch portion 18a to the second branch portion 18b and allows the flow of the refrigerant from the second branch portion 18b to the first branch portion 18a. (2-1-16) Accumulator

[0063] The accumulator 26 is connected between the switching mechanism 12 and the first suction portion 11e of the compressor 11. Here, the accumulator 26 is provided in a refrigerant flow path connecting the other end of the first heat transfer tube 17a of the liquid-gas heat exchanger 17 and the first suction portion 11e of the compressor 11. The accumulator 26 separates the refrigerant flowing out of the first heat transfer tube 17a of the liquid-gas heat exchanger 17 and flowing into the first suction portion 11e of the compressor 11 into a gas refrigerant and a liquid refrigerant.(2-2) Water Circuit

[0064] The water circuit 30 is a circuit in which water circulates during normal operation such as heating operation and cooling operation, and during operation as a countermeasure against frosting of a first heat exchanger 13 such as defrosting operation and capacity reduction operation.

[0065] The water circuit 30 includes the second heat exchanger 15, a pump 31, a gas-liquid separator 32, a third heat exchanger 33, and a heat source 34.(2-2-1) Second heat exchanger

[0066] The water flow path 15b of the second heat exchanger 15 described above constitutes the water circuit 30.(2-2-2) Pump

[0067] The pump 31 applies a predetermined pressure to the sucked water and discharges the sucked water. The pump 31 circulates water filled in the water circuit 30 in the water circuit 30 in a certain direction.(2-2-3) Gas-Liquid Separator

[0068] 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 an outlet of the water flow path 15b of the second heat exchanger 15 and an inlet of the third heat exchanger 33.(2-2-4) Third Heat Exchanger

[0069] The third heat exchanger 33 exchanges heat between the water flowing inside and indoor air sent from a second fan 33a. As the third heat exchanger 33, a heat exchanger suitable for the application such as the radiator is employed.

[0070] The third heat exchanger 33 has a water flow path (not illustrated). The water flow path of the third heat exchanger 33 is provided in the water circuit 30.(2-2-5) Heat Source

[0071] 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 when a temperature of the water flowing through the water circuit 30 is low. Here, capacity of the heat source 34 is half or less of capacity of the refrigeration cycle apparatus 1.

[0072] 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 an application such as a gas combustion type boiler or an electric heater is employed.(2-3) Heat Source Device

[0073] The heat source device 2 is disposed in a space different from a target space to be heated or cooled. Here, the heat source device 2 is installed outdoors (on a rooftop of a building, in the vicinity of an outer wall surface of the building, or the like). The heat source device 2 includes the above-described refrigerant circuit 10, the first fan 13a, a part of the above-described water circuit 30, and various sensors. Here, the heat source device 2 includes the pump 31 and the gas-liquid separator 32 as a part of the water circuit 30.(2-3-1) First Fan

[0074] The first fan 13a sends the outdoor air to the first heat exchanger 13. The first fan 13a is driven by a fan motor.(2-3-2) Sensor

[0075] The heat source device 2 is provided with an outdoor temperature sensor 41 and a hot water outflow temperature sensor 42. The outdoor temperature sensor 41 detects a temperature of the outdoor air before passing through the first heat exchanger 13. The hot water outflow temperature sensor 42 detects the temperature of the water after passing through the second heat exchanger 15.(2-4) Utilization Device

[0076] The utilization device 3 is installed in the building. The heat source device 2 and the utilization device 3 are thermally connected to each other via the second heat exchanger 15. Here, the water circuit 30 of the utilization device 3 is connected to the water flow path 15b of the second heat exchanger 15. The utilization device 3 includes a part of the water circuit 30 described above, the second fan 33a, and various sensors. Here, the utilization device 3 includes the heat source 34 and the third heat exchanger 33 as a part of the water circuit 30.(2-4-1) Second Fan

[0077] The second fan 33a sends the indoor air to the third heat exchanger 33. The second fan 33a is driven by the fan motor.

[0078] (2-4-2) Sensor

[0079] The utilization device 3 is provided with an indoor temperature sensor 43 that detects an indoor temperature that is a temperature of air taken in from inside a room and before passing through the third heat exchanger 33.(2-5) Control Unit(2-5-1) Overview

[0080] The control unit 4 controls components of the refrigeration cycle apparatus 1. As illustrated 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 hot water outflow temperature sensor 42, and the indoor temperature sensor 43 so as to be able to transmit and receive signals. The control unit 4 acquires information such as an operating state of each device and a measurement value of each sensor. The control unit 4 controls each device of the refrigeration cycle apparatus 1 based on the acquired information to realize the cooling operation, the heating operation, a defrosting operation, a capacity reduction operation, and the like.

[0081] The control unit 4 is embodied by a computer. The control unit 4 includes a control arithmetic device and a storage device (both are not illustrated). As the control arithmetic device, a processor such as a CPU or a GPU can be used. The control arithmetic device reads a program (computer executable code) stored in the storage device and performs predetermined arithmetic processing according to the program. Furthermore, the control arithmetic device can write an arithmetic result in the storage device and read information stored in the storage device according to the program.(2-5-2) Control During Defrosting Operation and Capacity Reduction Operation

[0082] Hereinafter, control by the control unit 4 during the defrosting operation and the capacity reduction operation of the refrigeration cycle apparatus 1 will be described.

[0083] The defrosting operation is an operation of melting frost adhering to the first heat exchanger 13. During the defrosting operation, the first heat exchanger 13 functions as the radiator. The flow of the refrigerant in the refrigerant circuit 10 during the defrosting operation of the present embodiment is the same as that during the cooling operation.

[0084] The capacity reduction operation is an operation for preventing the defrosting operation from being performed during the heating operation. In other words, the capacity reduction operation is a frost formation preventing heating operation. The capacity reduction operation reduces the capacity during the heating operation. Specifically, in the capacity reduction operation, the refrigeration cycle apparatus 1 is operated with a capacity lower than a capacity required from the utilization device 3. Therefore, in the capacity reduction operation, 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 the refrigerant in the refrigerant circuit 10 during the capacity reduction operation is the same as that during the heating operation.

[0085] The control unit 4 has a first condition and a second condition for an index related to the frosting of the first heat exchanger 13. The control unit 4 performs the defrosting operation when the index related to the frosting satisfies the first condition. The control unit 4 performs the capacity reduction operation when the index related to the frosting satisfies the second condition. The control unit 4 switches to the defrosting operation when the index related to the frosting satisfies the first condition during the capacity reduction operation.

[0086] The first condition is a condition requiring the defrosting operation. The second condition is a condition not requiring the defrosting operation. The second condition is a condition having a lower possibility of the frosting than the first condition. Therefore, the second condition is satisfied before the first condition is satisfied.

[0087] The first condition and the second condition are different from each other. However, the second condition is approximate to the first condition. The index related to the frosting is, for example, an outside air temperature (outdoor air temperature). The outside air temperature of the second condition is higher than the outdoor air temperature of the first condition and preferably higher than the outdoor air temperature of the first condition by 2° C. or more.

[0088] The second condition of the present embodiment is that the outside air temperature (outdoor air temperature) is −10° C. or higher and 7° C. or lower. In the first condition, the outside air temperature is lower than −10° C.

[0089] Note that the first condition is not limited to that the outside air temperature is equal to or lower than a predetermined value, but may be a condition that a predetermined time has elapsed since the last defrosting operation is completed, a condition that a temperature of the first heat exchanger 13 is equal to or lower than a predetermined value, a condition that an evaporation pressure or an evaporation temperature of the refrigerant in the refrigerant circuit 10 is equal to or lower than a predetermined value, or the like. In addition, the second condition is not limited to that the outside air temperature is equal to or lower than a predetermined value, and may be a condition that the temperature of the first heat exchanger 13 is equal to or lower than a predetermined value lower than a temperature of the first condition, a condition that the evaporation pressure or the evaporation temperature of the refrigerant in the refrigerant circuit 10 is equal to or lower than a predetermined value lower than the temperature of the first condition, or the like. A parameter (An index) of the first condition and a parameter (an index) of the second condition may be different from each other.

[0090] Here, when the refrigeration cycle apparatus 1 is activated and the first condition is not satisfied but the second condition is satisfied, the control unit 4 performs the capacity reduction operation. When the refrigeration cycle apparatus 1 is activated and the first condition is satisfied without satisfying the second condition, the control unit 4 performs the defrosting operation. For example, when the outside air temperature is very low such as −20° C., the defrosting operation is performed without performing the capacity reduction operation. For example, when the outside air temperature is low, such as 2° C., but there is no frost on the first heat exchanger 13, the capacity reduction operation is performed, and then the defrosting operation is performed when the frost adheres to the first heat exchanger 13.

[0091] During the capacity reduction operation, the control unit 4 performs the capacity reduction control for reducing capacity of a heat pump. In the present embodiment, the control unit 4 performs the capacity reduction operation by reducing the capacity of the compressor 11 or lowering a target hot water outflow temperature of the water. Specifically, in the capacity reduction operation, the control unit 4 makes the capacity of the compressor 11 smaller than the capacity of the compressor 11 set based on a temperature of the indoor air required from the utilization device 3 during the heating operation. More specifically, the control unit 4 sets a rotation speed of the motor of the compressor 11 during the capacity reduction operation to be lower than that during the heating operation. During the capacity reduction operation, the control unit 4 lowers the target hot water outflow temperature of the water flowing out of the water flow path 15b of the second heat exchanger 15 below the target hot water outflow temperature of the water set based on the temperature of the indoor air required from the utilization device 3 during the heating operation. More specifically, the control unit 4 sets the target hot water outflow temperature during the capacity reduction operation to be lower than that during the heating operation by several ° C.

[0092] When the capacity reduction operation is performed, the temperature of the water heated by the refrigerant in the second heat exchanger 15 becomes lower than the target hot water outflow temperature due to a decrease in the capacity of the refrigeration cycle apparatus 1. Therefore, here the control unit 4 operates the heat source 34 to heat the water before flowing into third heat exchanger 33 in order to supplement the target hot water outflow temperature during the capacity reduction operation. The control unit 4 may operate the heat source 34 when the heating operation is switched to the capacity reduction operation, or may operate the heat source 34 after a predetermined time elapses after the heating operation is switched to the capacity reduction operation.

[0093] During the capacity reduction operation, a heating amount of the water by the refrigeration cycle apparatus 1 is larger than a heating amount of the water by the heat source 34. Specifically, during the capacity reduction operation, the control unit 4 controls the heat source 34 so that the heating amount of the water by the refrigerant in the second heat exchanger 15 is larger than the heating amount of the water by the heat source 34. When the relationship between the heating amount of the water by the heat source 34 and the heating amount of the water by the refrigeration cycle apparatus 1 is reversed, energy consumption efficiency (COP) decreases. Therefore, when the heating amount of the water by the heat source 34 is equal to or larger than the heating amount of the water by the refrigeration cycle apparatus 1, the control unit 4 may switch from the capacity reduction operation to the defrosting operation regardless of the first condition.

[0094] The control unit 4 controls a maximum duration of the defrosting operation and a maximum duration of the capacity reduction operation. In the present embodiment, the maximum duration of the defrosting operation is shorter than the maximum duration of the capacity reduction operation. The maximum duration of the defrosting operation is, for example, 20 minutes. There is no upper limit set on the maximum duration of the capacity reduction operation. In other words, in the capacity reduction operation, the maximum duration is unlimited.(3) Operation

[0095] The operation of the refrigeration cycle apparatus 1 will be described with reference to FIGS. 1 to 6. The refrigeration cycle apparatus 1 performs the cooling operation, the heating operation, the defrosting operation, and the capacity reduction operation. The operation of the refrigeration cycle apparatus 1 including these operations is performed by the control unit 4.(3-1) Cooling Operation

[0096] Hereinafter, the operation of the refrigeration cycle apparatus 1 during the cooling operation will be described with reference to FIG. 3. The cooling operation illustrated in FIG. 3 is performed by the control unit 4, which has received a command of the cooling operation, controlling operations 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, and the like.

[0097] Specifically, the control unit 4 causes the compressor 11 to start operation, and controls a rotation speed of the drive motor 11d of the compressor 11. The switching mechanism12 is controlled to be in the second state. An opening degree of the first expansion mechanism 14 is controlled. The control unit 4 sets the target degree of superheating of the refrigerant flowing out of the first end 15aa of the second heat exchanger 15 based on, for example, a target hot water outflow temperature of the water flowing out of the water flow path 15b of the second heat exchanger 15. Then, the control unit 4 controls the opening degree of the first expansion mechanism 14 so that the degree of superheating of the refrigerant flowing out of the second heat exchanger 15 approaches the target degree of superheating. The second expansion mechanism 20 is controlled so that the opening degree is fully open or substantially fully open (hereinafter, simply referred to as fully open). The first valve 22 is controlled to be in the closed state. The second valve 23 is controlled to be in the open state.

[0098] In addition, the control unit 4 causes the pump 31 to start operation. The heat source 34 is controlled so as not to operate.(3-1-1) Refrigerant Circuit

[0099] When the compressor 11 starts operation, the low-pressure gas refrigerant in the refrigeration cycle is sucked from the first suction portion 11e. The first compression element 11b compresses the low-pressure refrigerant sucked by the first suction portion 11e to the intermediate pressure and discharges the refrigerant to the second compression element 11c. The second compression element 11c compresses the intermediate-pressure refrigerant discharged by the first compression element 11b to the high pressure in the refrigeration cycle, and discharges the refrigerant as the gas refrigerant to the discharge portion 11g.

[0100] Although details will be described later, a part of the injection pipe 19 has a low pressure in the cooling operation. Therefore, the check valve of the second suction portion 11f regulates the outflow of the intermediate-pressure refrigerant from the inside to the outside of the casing 11a.

[0101] The high-pressure gas refrigerant flowing out of the discharge portion 11g passes through the switching mechanism 12 through the first port P1 and the fourth port P4 in this order, and flows into the refrigerant flow path of the first heat exchanger 13 from the second end 13ab. The refrigerant flowing into the first heat exchanger 13 exchanges heat with the outdoor air at the installation place of the first heat exchanger 13 to dissipate heat, becomes a high-pressure liquid refrigerant, and flows out from the first end 13aa. In this manner, the first heat exchanger 13 functions as the radiator.

[0102] The high-pressure refrigerant flowing out of the first heat exchanger 13 flows through the liquid pipe 16 and is decompressed to the low pressure when passing through the first expansion mechanism 14 to be in a gas-liquid two-phase state. Since 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.

[0103] Since the first valve 22 is in the closed state, the refrigerant passing through the fourth valve 25 flows into the refrigerant flow path of the second heat exchanger 15 from the second end 15ab without flowing into the branch pipe 18 and the injection pipe 19. The refrigerant flowing into the second heat exchanger 15 exchanges heat with the water flowing through the water flow path 15b, evaporates to be the low-pressure gas refrigerant, and flows out from the first end 15aa. In this manner, the second heat exchanger 15 functions as the evaporator.

[0104] The low-pressure refrigerant flowing out of the second heat exchanger 15 flows into the first heat transfer tube 17a of the liquid-gas heat exchanger 17 through the switching mechanism 12 through the second port P2 and the third port P3 in this order. As described later, in the cooling operation, the refrigerant in the second heat transfer tube 17b is recovered by the compressor 11. Therefore, the refrigerant flowing into the first heat transfer tube 17a flows out of the first heat transfer tube 17a without exchanging heat. The refrigerant flowing out of the first heat transfer tube 17a passes through the accumulator 26 and is again sucked from the first suction portion 11e into the compressor 11.

[0105] In the cooling operation, since the first valve 22 is in the closed state, the refrigerant flowing through the liquid pipe 16 does not flow into the injection pipe 19. Further, in the cooling operation, since the first valve 22 is in the closed state, the second valve 23 is in the open state, and the second expansion mechanism 20 is fully open, when the compressor 11 operates, a part of the injection pipe 19, the first heat transfer tube 21a and the second heat transfer tube 21b of the economizer heat exchanger 21, the second heat transfer tube 17b of the liquid-gas heat exchanger 17, and a part of the branch pipe 18 have low pressure. Here, the part of the injection pipe 19 is specifically a portion between the first valve 22 and the first suction portion 11e of the compressor 11. In addition, the part of the branch pipe 18 is specifically a portion between the first valve 22 and the third valve 24.

[0106] As a result, at the time of switching from the heating operation to the cooling operation, the refrigerant remaining in the part of the injection pipe 19, the first heat transfer tube 21a and the second heat transfer tube 21b of the economizer heat exchanger 21, the second heat transfer tube 17b of the liquid-gas heat exchanger 17, and the part of the branch pipe 18 flows into the compressor 11 via the first suction portion 11e and is recovered.

[0107] As described above, the liquid-gas heat exchanger 17 is configured such that the refrigerant does not flow through the second heat transfer tube 17b during the cooling operation. In addition, the economizer heat exchanger 21 is configured such that the refrigerant does not flow therethrough during the cooling operation.(3-1-2) Water Circuit

[0108] When the pump 31 starts operation, the water filled in the water circuit 30 is sucked from a suction portion of the pump 31 and then discharged from a discharge portion of the pump 31.

[0109] The water flowing out of the pump 31 flows into the water flow path 15b of the second heat exchanger 15. The water flowing into the water flow path 15b exchanges heat (is cooled) with the low-pressure refrigerant flowing through the refrigerant flow path 15a, and flows out.

[0110] The water flowing out of the second heat exchanger 15 flows into the gas-liquid separator 32. The gas-liquid separator 32 recovers the refrigerant in a case where the refrigerant leaks to the water side in the second heat exchanger 15.

[0111] 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 at an installation place of the third heat exchanger 33. Thus, air in an air conditioning target space is cooled.

[0112] The water having exchanged heat with air at an installation place of the third heat exchanger 33 is again sucked into the pump 31.(3-2) Heating Operation

[0113] Hereinafter, the operation of the refrigeration cycle apparatus 1 during the heating operation will be described with reference to FIG. 4. The heating operation illustrated in FIG. 4 is performed by the control unit 4, which has received a command of the 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, and the like.

[0114] Specifically, the control unit 4 causes the compressor 11 to start operation, and controls a rotation speed of the drive motor 11d of the compressor 11. The switching mechanism 12 is controlled to be in the first state. An opening degree of the first expansion mechanism 14 is controlled. The control unit 4 sets the target degree of subcooling of the refrigerant flowing out of the second end 15ab of the second heat exchanger 15 based on, for example, the target hot water outflow temperature of the water flowing out of the water flow path 15b of the second heat exchanger 15. Then, the control unit 4 controls the opening degree of the first expansion mechanism 14 so that a degree of subcooling of the refrigerant flowing out of the second heat exchanger 15 approaches the target degree of subcooling. For example, the control unit 4 controls the opening degree of the second expansion mechanism 20 so that the degree of superheating of the refrigerant flowing out of the second expansion mechanism 20 approaches a predetermined target degree of superheating. The first valve 22 is controlled to be in the open state. The second valve 23 is controlled to be in the closed state.

[0115] In addition, the control unit 4 causes the pump 31 to start operation. The heat source 34 is controlled so as not to operate.(3-2-1) Refrigerant Circuit

[0116] When the compressor 11 starts operation, the low-pressure gas refrigerant in the refrigeration cycle is sucked from the first suction portion 11e, and the intermediate-pressure gas refrigerant in the refrigeration cycle is sucked from the second suction portion 11f. The first compression element 11b compresses the low-pressure refrigerant sucked by the first suction portion 11e to the intermediate pressure and discharges the refrigerant 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 sucked by the second suction portion 11f to the high pressure in the refrigeration cycle, and discharges the refrigerant as the gas refrigerant to the discharge portion 11g.

[0117] The high-pressure gas refrigerant flowing out of the discharge portion 11g passes through the switching mechanism 12 through the first port P1 and the second port P2 in this order, and flows into the refrigerant flow path 15a of the second heat exchanger 15 from the first end 15aa. The refrigerant flowing into the second heat exchanger 15 exchanges heat with the water flowing through the water flow path 15b to dissipate heat, becomes the high-pressure liquid refrigerant, and flows out from the second end 15ab. In other words, the second heat exchanger 15 functions as the radiator.

[0118] The high-pressure refrigerant flowing out of the second heat exchanger 15 flows through the liquid pipe 16. Since the first valve 22 is in the open state 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 flowing through the fourth valve 25. The refrigerant flowing 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.

[0119] The refrigerant flowing into the second portion 19b of the injection pipe 19 is decompressed to the intermediate pressure when flowing through the second expansion mechanism 20. The intermediate-pressure refrigerant flows into the first heat transfer tube 21a of the economizer heat exchanger 21, exchanges heat with the refrigerant passing through the second heat transfer tube 21b of the economizer heat exchanger 21, and flows out of the first heat transfer tube 21a.

[0120] Since the second valve 23 is in the closed state, the refrigerant flowing out of the first heat transfer tube 21a flows into the fourth portion 19d of the injection pipe 19 without flowing into the third portion 19c of the injection pipe 19. The refrigerant flowing into the fourth portion 19d is again sucked into the compressor 11 from the second suction portion 11f.

[0121] The refrigerant flowing into the branch pipe 18 flows into the second heat transfer tube 21b of the economizer heat exchanger 21, exchanges heat with the refrigerant passing through the first heat transfer tube 21a of the economizer heat exchanger 21, and flows out of the second heat transfer tube 21b.

[0122] The refrigerant flowing out of the second heat transfer tube 21b flows into the second heat transfer tube 17b of the liquid-gas heat exchanger 17 through the branch pipe 18. The refrigerant flowing into the second heat transfer tube 17b exchanges heat with the refrigerant passing through the first heat transfer tube 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 portion 18b.

[0123] The refrigerant flowing into the liquid pipe 16 is decompressed to the low pressure when passing through the first expansion mechanism 14, becomes the refrigerant in the gas-liquid two-phase state, and flows into the first heat exchanger 13 from the first end 13aa. The refrigerant flowing into the first heat exchanger 13 exchanges heat with the outdoor air at the installation place of the first heat exchanger 13, evaporates to be the low-pressure gas refrigerant, and flows out from the second end 13ab. In other words, the first heat exchanger 13 functions as the evaporator.

[0124] The low-pressure refrigerant flowing out of the first heat exchanger 13 flows into the first heat transfer tube 17a of the liquid-gas heat exchanger 17 through the switching mechanism 12 through the fourth port P4 and the third port P3 in this order. The refrigerant flowing 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 flows out of the first heat transfer tube 17a. The refrigerant flowing out of the first heat transfer tube 17a passes through the accumulator 26 and is again sucked from the first suction portion 11e into the compressor 11.

[0125] As described above, the liquid-gas heat exchanger 17 and the economizer heat exchanger 21 are configured such that the refrigerant flows during the heating operation.(3-2-2) Water Circuit

[0126] When the pump 31 starts operation, the water filled in the water circuit 30 is sucked from a suction portion of the pump 31 and then discharged from a discharge portion of the pump 31.

[0127] The water flowing out of the pump 31 flows into the water flow path 15b of the second heat exchanger 15. The water flowing into the water flow path 15b exchanges heat (is heated) with the low-pressure refrigerant flowing through the refrigerant flow path 15a, and flows out.

[0128] The water flowing out of the second heat exchanger 15 flows into the gas-liquid separator 32. The gas-liquid separator 32 recovers the refrigerant in a case where the refrigerant leaks to the water side in the second heat exchanger 15.

[0129] 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 at an installation place of the third heat exchanger 33. Thus, the air in the air conditioning target space is heated.

[0130] The water having exchanged heat with air at an installation place of the third heat exchanger 33 is again sucked into the pump 31.(3-3) Defrosting Operation

[0131] In the refrigeration cycle apparatus 1, the defrosting operation is performed when the index related to the frosting satisfies the first condition during the heating operation. Hereinafter, an operation of the refrigeration cycle apparatus 1 during the defrosting operation will be described with reference to FIGS. 2 and 5.

[0132] As illustrated in FIG. 5, the control unit 4 determines whether the index related to the frosting of the first heat exchanger 13 satisfies the first condition (step S1). Here, the control unit 4 acquires the outside air temperature detected by the outdoor temperature sensor 41, and compares the acquired outside air temperature with the first condition.

[0133] When determining in step S1 that the first condition is not satisfied, the control unit 4 continues the heating operation (step S2). On the other hand, when determining in step S1 that the first condition is satisfied, the control unit 4 determines that the frost is formed on the first heat exchanger 13, and starts the defrosting operation (step S3).

[0134] In step S3, the control unit 4 switches the switching mechanism 12 to the second state to make the flow of the refrigerant in the refrigerant circuit 10 similar to that during the cooling operation illustrated in FIG. 3. Note that the control unit 4 stops the first fan 13a.

[0135] Specifically, in the refrigerant circuit 10, the low-pressure gas refrigerant in the refrigeration cycle is compressed to the high pressure in the refrigeration cycle by the compressor 11, passes through the switching mechanism 12, and flows into the first heat exchanger 13. The high-pressure refrigerant flowing into the first heat exchanger 13 supplies heat to the first heat exchanger 13. Thus, the frost adhering to the first heat exchanger 13 melts, and the first heat exchanger 13 is defrosted.

[0136] The high-pressure refrigerant flowing out of the first heat exchanger 13 passes through the first expansion mechanism 14 to be the low-pressure refrigerant in the gas-liquid two-phase state, and flows into the refrigerant flow path 15a of the second heat exchanger 15. The low-pressure refrigerant flowing into the refrigerant flow path 15a exchanges heat with the water flowing through the water flow path 15b to be the low-pressure gas refrigerant, and flows out of the second heat exchanger 15. The low-pressure gas refrigerant flowing out of the second heat exchanger 15 passes through the switching mechanism 12 and is again sucked into the compressor 11.

[0137] In the water circuit 30, the water flowing 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 flows out. Thus, the water in the water flow path 15b is cooled. Therefore, an operation time of the defrosting operation has the maximum duration as an upper limit. Therefore, the control unit 4 determines whether duration of the defrosting operation has reached the maximum duration (step S4).

[0138] When determining in step S4 that a predetermined time has elapsed, the control unit 4 ends the defrosting operation (step S5) and restarts the heating operation (step S2). In this case, the control unit 4 switches the switching mechanism 12 to the first state.

[0139] On the other hand, when determining in step S4 that the maximum duration has not been reached, the control unit 4 continues the defrosting operation. Note that when determining that the frost has melted in the first heat exchanger 13 before reaching the maximum duration, the control unit 4 may end the defrosting operation and restart the heating operation (step S2).(3-4) Capacity Reduction Operation

[0140] In the refrigeration cycle apparatus 1, the capacity reduction operation is performed when the index related to the frosting satisfies the second condition during the heating operation. Hereinafter, an operation of the refrigeration cycle apparatus 1 during the capacity reduction operation will be described with reference to FIG. 6.

[0141] First, as illustrated in FIG. 6, similarly to an operation of the frosting operation, the control unit 4 determines whether the index related to the frosting satisfies the first condition (step S1). When the first condition is satisfied, the defrosting operation is started (step S3).

[0142] Next, the control unit 4 determines whether the index related to the frosting satisfies the second condition (step S11). Here, the control unit 4 acquires the outside air temperature detected by the outdoor temperature sensor 41, and compares the acquired outside air temperature with the second condition.

[0143] When determining in step S11 that the second condition is not satisfied, the control unit 4 continues the heating operation (step S2).

[0144] On the other hand, when determining in step S11 that the second condition is satisfied, the control unit 4 starts the capacity reduction operation because the frost is likely to form on the first heat exchanger 13 (step S12). In this step S3, the flow of the refrigerant in the refrigerant circuit 10 is maintained as in the heating operation.

[0145] In step S12, the capacity of the refrigeration cycle apparatus 1 is reduced. Here, the control unit 4 reduces the capacity of compressor 11 or lowers the target hot water outflow temperature of the water. Thus, a decrease in the temperature of the first heat exchanger 13 is suppressed.

[0146] In addition, in step S12, the control unit 4 operates the heat source 34 to heat the water in the water circuit 30. In this state, the control unit 4 determines whether the heating amount of the water by the refrigeration cycle apparatus 1 is larger than the heating amount of the water by the heat source 34 (step S13).

[0147] When determining in step S13 that the heating amount of the water by the refrigeration cycle apparatus 1 is equal to or less than the heating amount of the water by the heat source 34, the control unit 4 switches to the defrosting operation (step S3). On the other hand, when determining in step S13 that the heating amount of the water by the refrigeration cycle apparatus 1 is larger than the heating amount of the water by the heat source 34, the control unit 4 continues the capacity reduction operation (step S14).

[0148] Then, during the capacity reduction operation, the process returns to step S1 of determining whether the first condition is satisfied at a predetermined timing. Therefore, when the first condition is satisfied (step S1) during the capacity reduction operation, the control unit 4 switches to the defrosting operation. When the first condition and the second condition are no longer satisfied during the capacity reduction operation, the control unit 4 restarts the heating operation (step S2).

[0149] As described above, in the refrigeration cycle apparatus 1 of the present embodiment, there are a case where the operation is switched to the defrosting operation after the capacity reduction operation is performed and a case where the defrosting operation is performed without performing the capacity reduction operation.(4) Characteristics(4-1)

[0150] The refrigeration cycle apparatus 1 of the present embodiment includes the refrigerant circuit 10 and the control unit 4. The refrigerant circuit 10 includes the first heat exchanger 13. The first heat exchanger 13 exchanges heat between the outdoor air and the refrigerant. A refrigerant circulates in the refrigerant circuit 10. The control unit 4 performs the defrosting operation and the capacity reduction operation. The defrosting operation is an operation of melting frost adhering to the first heat exchanger 13. The capacity reduction operation is an operation for reducing the capacity. The control unit performs the capacity reduction operation when an index related to frosting satisfies a second condition, and performs the defrosting operation when the index related to the frosting satisfies a first condition during the capacity reduction operation.

[0151] According to the refrigeration cycle apparatus 1 of the present embodiment, before the defrosting operation of melting the frost adhering to the first heat exchanger 13 that exchanges heat with outdoor air, when the index related to the frosting satisfies the second condition, the capacity reduction operation of reducing the capacity of the refrigeration cycle apparatus 1 is performed. In other words, when the second condition under which the frost is likely to form on the first heat exchanger 13 is satisfied, the capacity reduction operation is performed. By performing the capacity reduction operation, it is possible to suppress the frosting on the first heat exchanger 13. Therefore, the refrigeration cycle apparatus 1 can reduce frequency of the defrosting operation, so that comfort can be improved.(4-2)

[0152] In the refrigeration cycle apparatus 1 of the present embodiment, the refrigerant preferably includes R290.

[0153] Since R290 is a low-pressure refrigerant, a size of the first heat exchanger 13 is large, and thus the defrosting operation takes time. However, in the refrigeration cycle apparatus 1 of the present embodiment, even when the refrigerant containing R290 is used, the frosting of the first heat exchanger 13 can be suppressed by performing the capacity reduction operation. Therefore, even when the refrigerant containing R290 is used, the frosting of the first heat exchanger 13 can be suppressed by performing the capacity reduction operation, so that the frequency of the defrosting operation can be reduced. Therefore, efficiency of the refrigeration cycle apparatus 1 using the refrigerant containing R290 can be improved.(4-3)

[0154] In the refrigeration cycle apparatus 1 of the present embodiment, the first heat exchanger 13 is preferably the microchannel heat exchanger.

[0155] The microchannel heat exchanger is more likely to have frost than the plate heat exchanger or the like. However, in the refrigeration cycle apparatus 1 of the present embodiment, even when such a microchannel heat exchanger is used as the first heat exchanger 13 that exchanges heat with the outdoor air, the frosting of the first heat exchanger 13 can be suppressed by performing the capacity reduction operation. Therefore, in the refrigeration cycle apparatus 1 of the present embodiment, the microchannel heat exchanger can be suitably used as the first heat exchanger 13.(4-4)

[0156] In the refrigeration cycle apparatus 1 of the present embodiment, the refrigerant circuit 10 preferably further includes the second heat exchanger 15. The second heat exchanger 15 exchanges heat between the refrigerant and the water. The refrigeration cycle apparatus 1 further includes the water circuit 30 and the heat source 34. The water flowing through the second heat exchanger 15 circulates in the water circuit 30. The heat source 34 heats the water.

[0157] Here, the heat source 34 can heat the water when the temperature of the water in the water circuit 30 is lower than the target hot water outflow temperature due to a decrease in the heating amount of the water by the refrigerant during the capacity reduction operation or the like. Therefore, it is possible to suppress a decrease in the temperature of the water while suppressing the frosting.(4-5)

[0158] In the refrigeration cycle apparatus 1 of the present embodiment, the refrigerant circuit 10 preferably further includes the compressor 11. The control unit 4 performs the capacity reduction operation by reducing the capacity of the compressor 11 or lowering the target hot water outflow temperature of the water.

[0159] Here, the capacity of the refrigeration cycle apparatus 1 is reduced by reducing the capacity of the compressor 11 or lowering the target hot water outflow temperature. Therefore, the refrigeration cycle apparatus 1 that suppresses the frosting can be easily realized.(4-6)

[0160] In the refrigeration cycle apparatus 1 of the present embodiment, the control unit 4 preferably operates the heat source 34 during the capacity reduction operation.

[0161] Here, the heat source 34 heats the water even when the temperature of the water heated by the refrigerant in the second heat exchanger 15 is lower than the target hot water outflow temperature due to the decrease in the capacity of the refrigeration cycle apparatus 1 during the capacity reduction operation. In this manner, the heat source 34 supplements for the capacity that is insufficient in the capacity reduction operation. Therefore, it is possible to easily realize the refrigeration cycle apparatus 1 that suppresses the decrease in the temperature of the water while suppressing the frosting.(4-7)

[0162] In the refrigeration cycle apparatus 1 of the present embodiment, the heating amount of the water by the refrigeration cycle apparatus 1 is larger than the heating amount of the water by the heat source during the capacity reduction operation.

[0163] Here, the heating amount of the water by the heat source 34 does not reverse to the heating amount of the water by the refrigeration cycle apparatus 1 during the capacity reduction operation, so that a decrease in efficiency of the refrigeration cycle apparatus 1 can be suppressed.(4-8)

[0164] In the refrigeration cycle apparatus 1 of the present embodiment, the second condition is preferably that the outside air temperature is −10° C. or higher and 7° C. or lower.

[0165] Here, since control is performed using a temperature of the outdoor air as the second condition, the capacity reduction operation is easily controlled.(4-9)

[0166] In the refrigeration cycle apparatus 1 of the present embodiment, the maximum duration of the defrosting operation is preferably shorter than the maximum duration of the capacity reduction operation.

[0167] Here, by continuously performing the capacity reduction operation, the frequency of the defrosting operation is reduced, and the maximum duration is shortened even when the defrosting operation is performed. Therefore, it is possible to reduce time during which the comfort decreases due to the defrosting operation.(4-10)

[0168] In the refrigeration cycle apparatus 1 of the present embodiment, the control unit 4 preferably switches to the defrosting operation when the first condition is satisfied during the capacity reduction operation.

[0169] Here, the control unit 4 performs the defrosting operation when the first condition is satisfied even during the capacity reduction operation. Thus, the decrease in efficiency of the refrigeration cycle apparatus 1 can be suppressed.(5) Modifications(5-1) First Modification(5-1-1) Overview

[0170] In the above embodiment, the control unit 4 operates the heat source only during the capacity reduction operation, but the present invention is not limited thereto. In the present modification, the control unit 4 operates the heat source 34 during the defrosting operation and the capacity reduction operation. Specifically, the control unit 4 may operate the heat source 34 at a start of the defrosting operation, or may operate the heat source 34 after a predetermined time has elapsed from the start of the defrosting operation.(5-1-2) Characteristics

[0171] As described above, in the refrigeration cycle apparatus 1 of the present modification, the control unit 4 operates the heat source 34 during the defrosting operation. Here, even when the temperature of the water decreases during the defrosting operation, the heat source 34 heats the water, so that a decrease in comfort can be suppressed.(5-2) Second Modification

[0172] In the above embodiment, the heat source 34 is a heater that selects on and off, but is not limited thereto. In the present modification, an output of the heat source 34 is variable. Specifically, the heat source 34 is a heater capable of outputting two or more stages.

[0173] Furthermore, here, the control unit 4 performs control such that the output of the heat source 34 during the capacity reduction operation is larger than the output of the heat source 34 during the defrosting operation. Then, when the heating amount of the water by the heat source 34 reverses to the heating amount of the water by the refrigeration cycle apparatus 1, the control unit 4 may switch from the capacity reduction operation to the defrosting operation regardless of the first condition.(5-3) Third Modification

[0174] Although the water circuit 30 includes the heat source 34 in the above embodiment, the heat source 34 may not constitute the water circuit 30. In this case, the heat source 34 may be provided in the utilization device 3 or in the heat source device 2.

[0175] The number of heat sources 34 included in the refrigeration cycle apparatus 1 is not limited to one, and may be plural. In this case, a plurality of heat sources 34 may be respectively disposed in the utilization device 3 and the heat source device 2, or may be disposed only in one of the utilization device 3 and the heat source device 2.(5-4) Fourth Modification(5-4-1) Overview

[0176] In the above embodiment, the second condition being a predetermined outside air temperature has been described as an example, but the present invention is not limited thereto. In the present modification, the second condition is a state where capacity required based on the outside air temperature exceeds the capacity of the first heat exchanger 13 to operate without frosting. The “capacity of the first heat exchanger 13 to operate without frosting” is a maximum capacity to perform the heating operation without frosting on the first heat exchanger 13. Hereinafter, description will be given with reference to FIG. 7.

[0177] FIG. 7 illustrates an example of a relationship between the outside air temperature and the capacity of the refrigeration cycle apparatus 1. In FIG. 7, a line L1 is the capacity of the refrigeration cycle apparatus 1 required based on the outside air temperature, and a line L2 is the capacity of the refrigeration cycle apparatus 1 that can operate without frosting on the first heat exchanger 13. As illustrated in FIG. 7, an inclination of line L1 indicating the capacity required based on the outside air temperature is different from an inclination of line L2 indicating the capacity of the first heat exchanger 13 to operate without frosting.

[0178] The second condition of the present modification is a state where the capacity of the line L1 exceeds the capacity of the line L2. This state is a state where the frost is likely to form on the first heat exchanger 13 because the first heat exchanger 13 is cooled due to the capacity of the refrigeration cycle apparatus 1 regardless of low outside air temperature. Here, the second condition is that the outside air temperature is equal to or lower than the predetermined outside air temperature (−3° C. in FIG. 7) and the capacity exceeds a certain capacity (7 kW in FIG. 7).

[0179] In addition, in the present modification, the control unit 4 operates the heat source 34 so as to supplement a capacity in a region R1 in FIG. 7. Specifically, the control unit 4 controls the heat source 34 such that the heat source 34 bears a difference between the capacity of the line L1 and the capacity of the line L2 for the predetermined outside air temperature.(5-4-2) Characteristics

[0180] In the refrigeration cycle apparatus 1 of the present modification, the second condition is the state where the capacity required based on the outside air temperature exceeds the capacity of the first heat exchanger 13 to operate without frosting.

[0181] In a state where the capacity required based on the outside air temperature exceeds the capacity of the first heat exchanger 13 to operate without frosting, the outside air temperature is low, so that the capacity of the refrigeration cycle apparatus 1 is large. In this case, since the first heat exchanger 13 is cooled, the frosting is likely to occur. Therefore, here, since the second condition is satisfied in such a state, the frosting can be effectively suppressed by performing the capacity reduction operation.(5-5) Fifth Modification(5-5-1) Overview

[0182] In the above embodiment, the second condition being a predetermined outside air temperature has been described as an example, but the present invention is not limited thereto. In the present modification, the second condition is that the evaporation temperature of the refrigerant in the first heat exchanger 13 is lower than a dew point temperature by a predetermined temperature or more and the outside air temperature is 2° C. or lower. Hereinafter, description will be given with reference to FIG. 8.

[0183] FIG. 8 illustrates an example of a relationship between the outside air temperature and the dew point temperature and the evaporation temperature of the refrigeration cycle apparatus 1. In FIG. 8, a line L3 represents the dew point temperature under a standard temperature condition with respect to the outside air temperature, and a line L4 represents a lower limit of the evaporation temperature at which the heating operation can be performed without frosting on the first heat exchanger 13. The evaporation temperature is the evaporation temperature of the refrigerant flowing out of the second end 13ab of the first heat exchanger 13. The standard temperature condition is a condition that a wet-bulb temperature is lower than a dry-bulb temperature by 1° C.

[0184] The second condition of the present modification is a state that the evaporation temperature of the line L4 is lower than the dew point temperature of the line L3 by the predetermined temperature or more when the outside air temperature is 2° C. or lower. This state is a state where the frost is likely to form on the first heat exchanger 13 because the first heat exchanger 13 is cooled since the outside air temperature is low and the evaporation temperature of the first heat exchanger 13 is low. Here, the second condition is that the outside air temperature is 2° C. or lower and the evaporation temperature is lower than the dew point temperature by the predetermined temperature (2° C. in FIG. 8) or more.

[0185] In addition, in the present modification, the control unit 4 operates the heat source 34 so as to supplement the evaporation temperature in a region R2 in FIG. 8. Specifically, the control unit 4 controls the heat source 34 such that the heat source 34 bears the evaporation temperature (2° C. from the dew point temperature in FIG. 8) of the line L3 for a predetermined outside air temperature. In other words, the control unit 4 controls the heat source 34 such that the evaporation temperature of the first heat exchanger 13 falls within a range of 2° C. or less from the dew point temperature.(5-5-2) Characteristics

[0186] As described above, in the refrigeration cycle apparatus 1 of the present 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 the predetermined temperature or more and the outside air temperature is 2° C. or lower.

[0187] When the evaporation temperature is lower than the dew point temperature by the predetermined temperature or more and the outside air temperature is as low as 2° C. or less, since the first heat exchanger 13 is cooled, the frosting is likely to occur. Therefore, here, since the second condition is satisfied in such a state, the frosting can be effectively suppressed by performing the capacity reduction operation.(5-6) Sixth Modification

[0188] In the above embodiment, the capacity reduction operation is performed by reducing the capacity of the compressor or lowering the target hot water outflow temperature of the water, but the capacity reduction operation is not limited thereto. In the capacity reduction operation, during the heating operation, the capacity may be reduced by performing another control or performing a plurality of controls. In the present modification, the capacity reduction operation is performed by control for reducing the evaporation temperature of the first heat exchanger 13.(5-7) Seventh Modification

[0189] In the above embodiment, circulation of the refrigerant in the refrigerant circuit 10 during the defrosting operation is similar to that during the cooling operation, however, the present invention is not limited to this as long as the refrigerant flows from the compressor 11 to the first heat exchanger 13 during the defrosting operation and the first heat exchanger 13 functions as the radiator. The flow of the refrigerant in the refrigerant circuit 10 during the defrosting operation may be different from that during the cooling operation.(5-8) Eighth Modification

[0190] In the above embodiment, the refrigeration cycle apparatus 1 including one third heat exchanger 33 has been described as an example, but the present invention is not limited thereto. The refrigeration cycle apparatus 1 may include a plurality of third heat exchangers 33.

[0191] In the present modification, the plurality of third heat exchangers 33 are connected to the second heat exchanger 15 in parallel with each other. Then, there are also a plurality of utilization devices 3 including the third heat exchanger 33. The plurality of utilization devices 3 may or may not be able to individually perform the cooling operation or the heating operation.(5-9) Ninth Modification

[0192] 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 the present invention is not limited thereto. In the present 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.(5-10) Tenth Modification

[0193] In the above embodiment, the refrigeration cycle apparatus 1 includes the refrigerant circuit 10 and the water circuit 30, but the present invention is not limited thereto. In the present modification, the refrigeration cycle apparatus includes a medium circuit in which a medium circulates instead of the water circuit in which the water circulates. The medium includes the refrigerant and a heat medium. Here, carbon dioxide circulates in the medium circuit. Therefore, the carbon dioxide having 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.(5-11) Eleventh Modification

[0194] In the above embodiment, the flammable refrigerant is used as the refrigerant, but the present invention is not limited thereto. In the present modification, a low-pressure refrigerant having a pressure of more than 0.08 MPa and 0.8 MPa or less at a condensation temperature of 25° C. is used as the refrigerant.

[0195] Although 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 described in the claims.REFERENCE SIGNS LIST1 Refrigeration cycle apparatus

[0197] 4 Control unit

[0198] 10 Refrigerant circuit

[0199] 11 Compressor

[0200] 13 First heat exchanger

[0201] 15 Second heat exchanger

[0202] 30 Water circuit

[0203] 31 Pump

[0204] 32 Gas-liquid separator

[0205] 33 Third heat exchanger

[0206] 33a Second Fan

[0207] 34 Heat sourceCITATION LISTPatent Literature

[0208] Patent Literature 1: JP 2018-091579 A

Claims

1. A refrigeration cycle apparatus comprising:a refrigerant circuit including a first heat exchanger that exchanges heat between outdoor air and a refrigerant, the refrigerant circulates in the refrigerant circuit; andcircuitry configured tocontrol a defrosting operation to melt frost adhering to the first heat exchanger, andcontrol a capacity reduction operation to reduce capacity when an index related to frosting satisfies a second condition, and performs control of the defrosting operation when the index related to the frosting satisfies a first condition during the capacity reduction operation.

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

3. The refrigeration cycle apparatus according to claim 1, whereinthe first heat exchanger is a microchannel heat exchanger.

4. The refrigeration cycle apparatus according to claim 2, whereinthe first heat exchanger is a microchannel heat exchanger.

5. The refrigeration cycle apparatus according to claim 1, whereinthe refrigerant circuit further includes a second heat exchanger that exchanges heat between the refrigerant and water, andthe refrigeration cycle apparatus further comprises:a water circuit in which the water that flows through the second heat exchanger circulates; anda heat source that heats the water.

6. The refrigeration cycle apparatus according to claim 2, whereinthe refrigerant circuit further includes a second heat exchanger that exchanges heat between the refrigerant and water, andthe refrigeration cycle apparatus further comprises:a water circuit in which the water that flows through the second heat exchanger circulates; anda heat source that heats the water.

7. The refrigeration cycle apparatus according to claim 3, whereinthe refrigerant circuit further includes a second heat exchanger that exchanges heat between the refrigerant and water, andthe refrigeration cycle apparatus further comprises:a water circuit in which the water that flows through the second heat exchanger circulates; anda heat source that heats the water.

8. The refrigeration cycle apparatus according to claim 5, whereinthe refrigerant circuit further includes a compressor, andthe control unit performs the capacity reduction operation by reducing capacity of the compressor or lowering a target hot water outflow temperature of the water.

9. The refrigeration cycle apparatus according to claim 5, whereinthe circuitry is further configured to control the heat source during the capacity reduction operation.

10. The refrigeration cycle apparatus according to claim 8, whereinthe circuitry is further configured to control the heat source during the capacity reduction operation.

11. The refrigeration cycle apparatus according to claim 10, whereina heating amount of the water by the refrigeration cycle apparatus is larger than a heating amount of the water by the heat source during the capacity reduction operation.

12. The refrigeration cycle apparatus according to claim 5, whereinthe circuitry is further configured to control the heat source during the defrosting operation.

13. The refrigeration cycle apparatus according to claim 8, whereinthe circuitry is further configured to control the heat source during the defrosting operation.

14. The refrigeration cycle apparatus according to claim 11, whereinthe circuitry is further configured to control the heat source during the defrosting operation.

15. The refrigeration cycle apparatus according to claim 1, whereinthe second condition is that an outside air temperature is −10° C. or higher and 7° C. or lower.

16. The refrigeration cycle apparatus according to claim 1, whereinthe second condition is a state where capacity required based on an outside air temperature exceeds capacity of the first heat exchanger to operate without frosting.

17. The refrigeration cycle apparatus according to claim 14, whereinthe second condition is a state where capacity required based on an outside air temperature exceeds capacity of the first heat exchanger to operate without frosting.

18. The refrigeration cycle apparatus according to claim 1, whereinthe second condition is that an evaporation temperature of the refrigerant in the first heat exchanger is lower than a dew point temperature by a predetermined temperature or more and an outside air temperature is 2° C. or lower.

19. The refrigeration cycle apparatus according to claim 1, whereina maximum duration of the defrosting operation is shorter than a maximum duration of the capacity reduction operation.

20. The refrigeration cycle apparatus according to claim 1, whereinthe circuitry is further configured to switch to the defrosting operation when the first condition is satisfied during the capacity reduction operation.

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