Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B47/00—Arrangements for preventing or removing deposits or corrosion, not provided for in another subclass
  • F25B47/02—Defrosting cycles

Definitions

• This disclosure relates to a refrigeration cycle device.
• a refrigeration cycle device has a heat exchanger.
• the heat exchanger functions as a condenser, for example, mounted in the indoor unit.
• the liquid refrigerant condensed in the heat exchanger is reduced in pressure by a throttling device, resulting in a two-phase gas-liquid state in which gas refrigerant and liquid refrigerant are mixed.
• the two-phase gas-liquid refrigerant then evaporates in a heat exchanger mounted in the outdoor unit, functioning as an evaporator, where the liquid refrigerant becomes low-pressure gas refrigerant.
• the low-pressure gas refrigerant sent out from the heat exchanger then flows into a compressor, where it is compressed to become high-temperature, high-pressure gas refrigerant, which is then discharged from the compressor again. This cycle is repeated in the refrigeration cycle device.
• the circuit connected to the indoor heat exchanger is also connected to a circuit that defrosts the outdoor heat exchanger.
• the refrigerant pressure in the indoor heat exchanger during heating operation is higher than the refrigerant discharge pressure from the compressor during defrost operation. Therefore, when switching from heating operation to defrost operation, the high-pressure liquid refrigerant present in the indoor heat exchanger flows into the defrost circuit, driven by the pressure difference with the refrigerant discharge pressure from the compressor during defrost operation. This means that liquid refrigerant is drawn into the compressor, making it more susceptible to compressor failure.
• This disclosure has been made to solve the problems described above, and aims to provide a refrigeration cycle device that can reduce compressor failures.
• the refrigeration cycle device disclosed herein comprises a refrigerant circuit having a compressor, an indoor heat exchanger, a first outdoor heat exchanger, and a second outdoor heat exchanger, and a control device.
• the refrigerant circuit has a first path and a second path as refrigerant paths during heating operation in which the indoor heat exchanger functions as a condenser.
• the first path is a path from the compressor, passing through a flow control valve, the indoor heat exchanger, a first throttling device, a second throttling device, the first outdoor heat exchanger, and a first flow path switching device, and returning to the compressor.
• the second path is a path from the compressor, passing through the flow control valve, the indoor heat exchanger, the first throttling device, a third throttling device, the second outdoor heat exchanger, and a second flow path switching device, and returning to the compressor.
• the refrigerant circuit is configured to operate in a first defrosting operation in which the first outdoor heat exchanger functions as a condenser and the second outdoor heat exchanger functions as an evaporator.
• the refrigerant circuit has a third path as a refrigerant path during a second defrost operation in which the second outdoor heat exchanger functions as a condenser and the first outdoor heat exchanger functions as an evaporator, and the third path runs from the compressor through the first flow switching device, the first outdoor heat exchanger, the second throttling device, the third throttling device, the second outdoor heat exchanger, and the second flow switching device, and returns to the compressor.
• the refrigerant circuit has a fourth path as a refrigerant path during a second defrost operation in which the second outdoor heat exchanger functions as a condenser and the first outdoor heat exchanger functions as an evaporator, and the fourth path runs from the compressor through the second flow switching device, the second outdoor heat exchanger, the third throttling device, the second throttling device, the first outdoor heat exchanger, and the first flow switching device, and returns to the compressor.
• the control device fully closes the flow control valve and the first throttling device during the first defrost operation and the second defrost operation.
• This disclosure makes it possible to reduce compressor failures.
• the refrigeration cycle device 200 has a heat source unit 201 and a heat load unit 202.
• the heat source unit 201 and the heat load unit 202 are connected via a gas pipe 203 and a liquid pipe 204.
• the heat source unit 201 is equipped with a compressor 10, a flow path switching device 11, a flow control valve 12, flow path switching devices 13a and 13b, expansion devices 32a and 32b, outdoor heat exchangers 40a and 40b, and outdoor blowers 41a and 41b.
• the heat load unit 202 is equipped with an indoor heat exchanger 20, an indoor blower 21, and an expansion device 31.
• the outdoor heat exchanger 40a and the outdoor heat exchanger 40b are arranged in parallel.
• the refrigerant circuit has, as its main circuits, a first path passing through the outdoor heat exchanger 40a and a second path passing through the outdoor heat exchanger 40b.
• the refrigerant circuit of the refrigeration cycle device 200 has, as paths during defrosting operation, a third path for defrosting the outdoor heat exchanger 40a and a fourth path for defrosting the outdoor heat exchanger 40b.
• the third path passes through the compressor 10, flow path switching device 11, flow path switching device 13a, outdoor heat exchanger 40a, expansion device 32a, expansion device 32b, outdoor heat exchanger 40b, flow path switching device 13b, and flow path switching device 11 in this order, before returning to the compressor 10.
• the fourth path passes through the compressor 10, flow path switching device 11, flow path switching device 13b, outdoor heat exchanger 40b, expansion device 32b, expansion device 32a, outdoor heat exchanger 40a, flow path switching device 13a, and flow path switching device 11 in this order, before returning to the compressor 10.
• the compressor 10 draws in refrigerant, compresses it, and discharges it in a high-temperature, high-pressure state.
• the refrigerant compressed by the compressor 10 is discharged and sent to the flow path switching device 11.
• the compressor 10 is configured, for example, as a rotary compressor, scroll compressor, screw compressor, or reciprocating compressor.
• the compressor 10 may be either a high-pressure shell type or a low-pressure shell type, but the oil outflow suppression effect of this embodiment is particularly significant when the compressor 10 is a high-pressure shell type.
• the flow rate adjustment valve 12 is provided between the branch portion 14b and the indoor heat exchanger 20.
• the flow rate adjustment valve 12 is an on-off valve that can be fully closed.
• the flow rate adjustment valve 12 is controlled by the control device 210.
• Both the branch portion 14a and the branch portion 14b are provided between the flow path switching device 11 and the flow rate adjustment valve 12.
• the flow path switching device 13a is, for example, a three-way valve.
• the flow path switching device 13a is provided in the first path between the outdoor heat exchanger 40a and the branching section 42.
• the flow path switching device 13a has a first port P1, a second port P2, and a third port P3.
• the first port P1 is connected to the branching section 42 side of the first path.
• the second port P2 is connected to the outdoor heat exchanger 40a side of the first path.
• the third port P3 is connected to the branching section 14a via a refrigerant piping.
• the flow path switching device 13a is controlled by the control device 210.
• the flow path switching device 13a can be set to at least a state C in which the first port P1 and the second port P2 are connected and the third port P3 is blocked, and a state D in which the second port P2 and the third port P3 are connected and the first port P1 is blocked.
• the flow path switching device 13a is set to state C.
• the flow path switching device 13a is set to state D.
• the flow path switching device 13b is, for example, a three-way valve.
• the flow path switching device 13b is provided in the second path between the outdoor heat exchanger 40b and the branching section 42.
• the flow path switching device 13b has a first port P1, a second port P2, and a third port P3.
• the first port P1 is connected to the branching section 42 side of the second path.
• the second port P2 is connected to the outdoor heat exchanger 40b side of the second path.
• the third port P3 is connected to the branching section 14b via a refrigerant piping.
• the flow path switching device 13b is controlled by the control device 210.
• the flow path switching device 13b can be set to at least a state C in which the first port P1 and the second port P2 are connected and the third port P3 is blocked, and a state D in which the second port P2 and the third port P3 are connected and the first port P1 is blocked.
• the flow path switching device 13b is set to state C.
• the flow path switching device 13b is set to state D.
• the indoor heat exchanger 20 is a heat exchanger that exchanges heat between the refrigerant flowing through the refrigerant circuit and the air supplied by the indoor blower 21.
• the indoor blower 21 is controlled by the control device 210.
• the expansion device 31 is provided between the indoor heat exchanger 20 and the branch section 33.
• the expansion device 31 is a fully closable expansion valve.
• an electronic expansion valve is used as the expansion device 31.
• the expansion device 31 is controlled by the control device 210.
• Expansion device 32a is provided between branch section 33 and outdoor heat exchanger 40a.
• Expansion device 32b is provided between branch section 33 and outdoor heat exchanger 40b.
• Expansion devices 32a and 32b are each fully closable expansion valves. Electronic expansion valves, for example, are used for expansion devices 32a and 32b. Expansion devices 32a and 32b are controlled by control device 210.
• the outdoor heat exchanger 40a is a heat exchanger that exchanges heat between the refrigerant flowing through the refrigerant circuit and the air supplied by the outdoor blower 41a.
• the outdoor heat exchanger 40b is a heat exchanger that exchanges heat between the refrigerant flowing through the refrigerant circuit and the air supplied by the outdoor blower 41b.
• the outdoor blowers 41a and 41b are controlled by the control device 210.
• the control device 210 is configured to control the entire refrigeration cycle device, including the compressor 10, flow path switching device 11, flow control valve 12, throttling device 31, throttling device 32a, throttling device 32b, indoor blower 21, and outdoor blowers 41a and 41b. These controls may be realized by a microcomputer equipped with a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc., or may be realized by dedicated hardware.
• the control device 210 may be provided in the heat source unit 201 or in the heat load unit 202.
• FIG. 2 is a diagram showing the control details of each operation mode by the control device of the refrigeration cycle device according to this embodiment.
• the flow path switching device 11 is set to state A. This connects the discharge side of the compressor 10 to the indoor heat exchanger 20, and connects the suction side of the compressor 10 to the outdoor heat exchangers 40a and 40b.
• the flow path switching devices 13a and 13b are both set to state C.
• the flow control valve 12 is set to fully open.
• the expansion device 31 is set to fully open.
• the expansion device 32a is controlled, for example, so that the degree of superheat of the outlet refrigerant of the outdoor heat exchanger 40a is constant.
• the expansion device 32b is controlled, for example, so that the degree of superheat of the outlet refrigerant of the outdoor heat exchanger 40b is constant.
• the outdoor blowers 41a and 41b are set to on.
• the indoor heat exchanger 20 functions as a condenser. That is, in the indoor heat exchanger 20, heat is exchanged between the refrigerant circulating inside and the indoor air blown by the indoor blower 21, and the refrigerant's heat of condensation is dissipated to the indoor air. As a result, the refrigerant that flows into the indoor heat exchanger 20 condenses into high-pressure liquid refrigerant. In addition, the indoor air blown by the indoor blower 21 is heated by the heat dissipation effect of the refrigerant.
• the high-pressure liquid refrigerant flowing out of the indoor heat exchanger 20 flows into the throttling device 32a and the throttling device 32b via the throttling device 31 and the liquid pipe 204, where it is decompressed and becomes a low-pressure two-phase refrigerant.
• the low-pressure two-phase refrigerant flows into the outdoor heat exchangers 40a and 40b.
• the outdoor heat exchangers 40a and 40b function as evaporators. That is, in the outdoor heat exchangers 40a and 40b, heat is exchanged between the refrigerant circulating therein and the outdoor air blown by the outdoor fans 41a and 41b, and the refrigerant's heat of evaporation is absorbed from the outdoor air.
• the refrigerant flowing into the outdoor heat exchangers 40a and 40b evaporates and becomes a low-pressure gas refrigerant or two-phase refrigerant.
• the low-pressure gas refrigerant or two-phase refrigerant flowing out of the outdoor heat exchanger 40a passes through the flow path switching device 13a and the flow path switching device 11 and is drawn into the compressor 10.
• the gas refrigerant or two-phase refrigerant flowing out of the outdoor heat exchanger 40b passes through the flow path switching device 13b and the flow path switching device 11 and is drawn into the compressor 10. During heating operation, the above cycle is continuously repeated.
• defrosting operation is performed periodically to defrost the outdoor heat exchangers 40a and 40b.
• Defrosting operation includes a first defrosting operation to defrost one outdoor heat exchanger, 40a, and a second defrosting operation to defrost the other outdoor heat exchanger, 40b.
• the refrigerant flows through the third path, and in the second defrosting operation, the refrigerant flows through the fourth path.
• the first defrost operation and the second defrost operation are performed alternately, for example, after the heating operation. That is, the first defrost operation is performed after the heating operation or after the second defrost operation.
• the second defrost operation is performed after the heating operation or after the first defrost operation. After defrosting is completed by the first defrost operation and the second defrost operation, the system returns to heating operation.
• FIG. 3 is a circuit diagram showing the schematic configuration of the refrigeration cycle apparatus according to this embodiment during the first defrost operation.
• the flow path switching device 11 is set to state B.
• the flow path switching device 13a is set to state C.
• the flow path switching device 13b is set to state D. This connects the discharge side of the compressor 10 to the outdoor heat exchanger 40a, and the suction side of the compressor 10 to the outdoor heat exchanger 40b.
• the flow control valve 12 is set to fully closed.
• the expansion device 31 is set to fully closed.
• the expansion devices 32a and 32b are controlled so that a pressure difference is created between the outdoor heat exchanger 40a and the outdoor heat exchanger 40b.
• the outdoor blower 41a is set to off or on.
• the outdoor blower 41b is set to on.
• the high-temperature, high-pressure gas refrigerant discharged from the compressor 10 flows into the outdoor heat exchanger 40a via the flow path switching device 11 and the flow path switching device 13a.
• the outdoor heat exchanger 40a functions as a condenser. That is, in the outdoor heat exchanger 40a, heat is exchanged between the refrigerant circulating inside and the frost on the surface of the outdoor heat exchanger 40a, and the frost melts due to the heat of condensation of the refrigerant. This defrosts the outdoor heat exchanger 40a.
• the refrigerant flows out of the outdoor heat exchanger 40a as a high-pressure two-phase refrigerant or liquid refrigerant.
• the high-pressure two-phase refrigerant or liquid refrigerant flowing out of the outdoor heat exchanger 40a is decompressed by the throttling device 32a and the throttling device 32b, becoming low-pressure two-phase refrigerant and flowing into the outdoor heat exchanger 40b.
• the outdoor heat exchanger 40b functions as an evaporator. That is, in the outdoor heat exchanger 40b, heat is exchanged between the refrigerant circulating inside and the outdoor air blown by the outdoor blower 41b. The refrigerant absorbs heat from the outdoor air and evaporates, becoming low-pressure gas refrigerant.
• the low-pressure gas refrigerant flowing out of the outdoor heat exchanger 40b is drawn into the compressor 10 via the flow path switching device 13b and the flow path switching device 11.
• the flow control valve 12 and the throttling device 31 are switched from fully open to fully closed.
• the liquid refrigerant that was present in the indoor heat exchanger 20 during heating operation is trapped between the flow control valve 12 and the throttling device 31 and remains in the indoor heat exchanger 20 during first defrost operation. Therefore, even if the refrigerant pressure inside the indoor heat exchanger 20 is higher than the refrigerant discharge pressure of the compressor 10 during first defrost operation, the amount of liquid refrigerant flowing from the indoor heat exchanger 20 into the compressor 10 can be reduced. Therefore, breakdowns in the compressor 10 can be suppressed.
• the outdoor blower 41b operates, which promotes evaporation of the refrigerant in the outdoor heat exchanger 40b. This further reduces the amount of liquid refrigerant flowing into the compressor 10. Furthermore, by operating the outdoor heat exchanger 40b, which is not subject to defrosting, as an evaporator, the latent heat of the refrigerant can be used for defrosting, shortening the defrosting time. This allows for an earlier return to heating operation from defrost operation, improving heating capacity.
• the second defrost operation is performed.
• the second defrost operation may be performed after the first defrost operation is completed, with a heating operation in between.
• the refrigerant circuit is not shown, the second defrost operation is performed in the same way as the first defrost operation.
• the flow path switching device 11 is set to state B.
• the flow path switching device 13a is set to state D.
• the flow path switching device 13b is set to state C. This connects the discharge side of the compressor 10 to the outdoor heat exchanger 40b, and also connects the suction side of the compressor 10 to the outdoor heat exchanger 40a.
• the flow control valve 12 is set to fully closed.
• the throttling device 31 is set to fully closed.
• the throttling devices 32a and 32b are controlled so that a pressure difference is created between the outdoor heat exchanger 40a and the outdoor heat exchanger 40b.
• the outdoor blower 41a is set to on.
• the outdoor fan 41b can be set to either off or on.
• the compressor 10, flow path switching device 11, flow path switching device 13b, outdoor heat exchanger 40b, expansion device 32b, expansion device 32a, outdoor heat exchanger 40a, flow path switching device 13a, flow path switching device 11, and compressor 10 are connected in this order.
• the flow control valve 12 and the throttling device 31 are set to fully closed.
• the liquid refrigerant that was present in the indoor heat exchanger 20 during heating operation is trapped between the flow control valve 12 and the throttling device 31 and remains in the indoor heat exchanger 20 during the second defrost operation. Therefore, even if the refrigerant pressure inside the indoor heat exchanger 20 is higher than the refrigerant discharge pressure of the compressor 10 during the second defrost operation, the amount of liquid refrigerant flowing from the indoor heat exchanger 20 into the compressor 10 can be reduced. This makes it possible to prevent breakdowns in the compressor 10.
• Flow path switching device 13a can be set to at least state C in which the first port P1 and the second port P2 are connected and the third port P3 and the fourth port P4 are connected, and state D in which the second port P2 and the third port P3 are connected and the fourth port P4 is connected to the first port P1.
• Flow path switching device 13b has the same configuration as flow path switching device 13a. In this modified example, it can be operated in the same manner as in Figures 1 to 3.
• the refrigeration cycle apparatus 200 includes a refrigerant circuit having a compressor 10, an indoor heat exchanger 20, a first outdoor heat exchanger 40a, and a second outdoor heat exchanger 40b, and a control device 210.
• the refrigerant circuit has a first path and a second path as refrigerant paths during heating operation when the indoor heat exchanger 20 functions as a condenser.
• the first path is a path from the compressor 10, passing through the flow control valve 12, the indoor heat exchanger 20, the first throttling device 31, the second throttling device 32a, the first outdoor heat exchanger 40a, and the first flow switching device 13a, before returning to the compressor 10.
• the refrigerant circuit has a third path as a refrigerant path during first defrost operation, in which the first outdoor heat exchanger 40a functions as a condenser and the second outdoor heat exchanger 40b functions as an evaporator.
• the third path is a path that runs from the compressor 10, through the first flow path switching device 13a, the first outdoor heat exchanger 40a, the second throttling device 32a, the third throttling device 32b, the second outdoor heat exchanger 40b, and the second flow path switching device 13b, and returns to the compressor 10.
• the refrigerant circuit has a fourth path as a refrigerant path during second defrost operation, in which the second outdoor heat exchanger 40b functions as a condenser and the first outdoor heat exchanger 40a functions as an evaporator.
• the fourth path runs from the compressor 10 through the second flow switching device 13b, the second outdoor heat exchanger 40b, the third throttling device 32b, the second throttling device 32a, the first outdoor heat exchanger 40a, and the first flow switching device 13a before returning to the compressor 10.
• the control device 210 fully closes the flow control valve 12 and the first throttling device 31.
• FIG. 7 is a circuit diagram showing a schematic configuration of the refrigeration cycle apparatus according to this embodiment during the second defrosting operation. As shown in Fig. 7, the refrigeration cycle apparatus of this embodiment has a circuit configuration similar to that shown in Fig. 1.
• the high-temperature, high-pressure gas refrigerant discharged from the compressor 10 flows into the outdoor heat exchanger 40b via the flow path switching device 11 and the flow path switching device 13b.
• the outdoor heat exchanger 40b functions as a condenser. That is, in the outdoor heat exchanger 40b, heat is exchanged between the refrigerant circulating inside and the frost on the surface of the outdoor heat exchanger 40b, and the frost melts due to the heat of condensation of the refrigerant. This defrosts the outdoor heat exchanger 40b.
• the refrigerant flows out of the outdoor heat exchanger 40b as a high-pressure two-phase refrigerant or liquid refrigerant.
• the high-pressure two-phase refrigerant or liquid refrigerant flowing out of the outdoor heat exchanger 40b is decompressed by the throttling device 32b and the throttling device 32a, becoming low-pressure two-phase refrigerant and flowing into the outdoor heat exchanger 40a.
• the outdoor heat exchanger 40a functions as an evaporator. That is, in the outdoor heat exchanger 40a, heat is exchanged between the refrigerant circulating inside and the outdoor air blown by the outdoor blower 41a. The refrigerant absorbs heat from the outdoor air and evaporates, becoming low-pressure gas refrigerant.
• the low-pressure gas refrigerant flowing out of the outdoor heat exchanger 40a is drawn into the compressor 10 via the flow path switching device 13a and the flow path switching device 11.
• the compressor 10, flow path switching device 11, flow path switching device 13b, outdoor heat exchanger 40b, expansion device 32b, expansion device 32a, outdoor heat exchanger 40a, flow path switching device 13a, flow path switching device 11, and compressor 10 are connected in this order. This forms the path for the second defrost operation.
• the first defrost operation is also performed in the same way as the second defrost operation.
• the refrigerant circuit further includes a flow path switching device 11.
• the flow path switching device 11 is a four-way valve that switches the flow path between heating operation and cooling operation.
• the flow path of the flow path switching device 11 cannot be switched between heating operation and first defrost operation, or between heating operation and second defrost operation.
• This configuration shortens the time that the compressor 10 is stopped when transitioning from heating operation to first defrost operation or second defrost operation. Therefore, the time until heating operation resumes can be shortened.
• FIG. 9 is a circuit diagram showing a schematic configuration of the refrigeration cycle apparatus according to this embodiment during the second defrosting operation.
• the refrigeration cycle apparatus 200 includes a compressor-mounted unit 205 and one or more outdoor heat exchanger units 206a and 206b as outdoor-side units.
• the compressor-mounted unit 205, the outdoor heat exchanger unit 206a, and the outdoor heat exchanger unit 206b are formed separately from one another.
• the compressor-mounted unit 205 is connected to the outdoor heat exchanger unit 206a and the outdoor heat exchanger unit 206b via refrigerant piping.
• the substantial circuit configuration of the refrigeration cycle apparatus 200 is similar to the circuit configurations shown in FIGS. 1 and 7.
• the compressor mounting unit 205 is equipped with a compressor 10, a flow path switching device 11, flow path switching devices 13a and 13b, and a flow control valve 12.
• the outdoor heat exchanger unit 206a is equipped with a throttling device 32a, an outdoor heat exchanger 40a, and an outdoor blower 41a.
• the outdoor heat exchanger unit 206b is equipped with a throttling device 32b, an outdoor heat exchanger 40b, and an outdoor blower 41b.
• the compressor 10 and the outdoor heat exchangers 40a and 40b are mounted in separate units, ensuring a large piping volume from each of the outdoor heat exchangers 40a and 40b to the compressor 10.
• Figure 10 is a circuit diagram showing the general configuration of a refrigeration cycle device according to Variation 1 of this embodiment during second defrost operation.
• Figure 11 is a circuit diagram showing the general configuration of a refrigeration cycle device according to Variation 2 of this embodiment during second defrost operation.
• Figure 12 is a circuit diagram showing the general configuration of a refrigeration cycle device according to Variation 3 of this embodiment during first defrost operation.
• the refrigeration cycle apparatus 200 has, as outdoor units, a compressor-mounted unit 205, a relay unit 207, and one or more outdoor heat exchanger units 206a, 206b.
• the substantial circuit configuration of Figure 10 is similar to the circuit configurations shown in Figures 1 and 7.
• the substantial circuit configuration of Figure 11 is similar to the circuit configuration shown in Figure 4.
• the substantial circuit configuration of Figure 12 is similar to the circuit configuration shown in Figure 5.
• the compressor mounting unit 205 is equipped with a compressor 10 and a flow path switching device 11.
• the relay unit 207 is equipped with flow path switching devices 13a and 13b and a flow control valve 12.
• the outdoor heat exchanger unit 206a is equipped with a throttling device 32a, an outdoor heat exchanger 40a, and an outdoor blower 41a.
• the outdoor heat exchanger unit 206b is equipped with a throttling device 32b, an outdoor heat exchanger 40b, and an outdoor blower 41b.
• heat is retained in the piping from the compressor-mounted unit 205 to the relay unit 207, which can be installed closer to the heat load unit 202, during heating operation. This heat can be used for defrosting during defrosting operation, shortening the defrosting time and shortening the time until heating is restored.
• the refrigeration cycle apparatus 200 further includes a compressor mounting unit 205 and one or more outdoor heat exchanger units 206a, 206b.
• the compressor mounting unit 205 is equipped with a compressor 10.
• the outdoor heat exchanger unit 206a and the outdoor heat exchanger unit 206b are equipped with a first outdoor heat exchanger 40a and a second outdoor heat exchanger 40b, respectively.
• the compressor 10 and the first and second outdoor heat exchangers 40a and 40b are mounted in separate units, ensuring a large piping volume from each of the first and second outdoor heat exchangers 40a and 40b to the compressor 10. Therefore, even if the capacity of the outdoor heat exchanger acting as an evaporator decreases during the first and second defrosting operations, the amount of liquid refrigerant flowing from the outdoor heat exchanger to the compressor 10 can be reduced.
• Embodiment 4 A refrigeration cycle apparatus according to a fourth embodiment will be described.
• a refrigeration cycle apparatus having the same configuration as that shown in Fig. 7 is used.
• Fig. 13 is a diagram showing the control contents of each operation mode by the control device of the refrigeration cycle apparatus according to this embodiment.
• the refrigeration cycle device of this embodiment can perform first heating defrost operation and second heating defrost operation in addition to heating operation, first defrost operation, and second defrost operation.
• first heating defrost operation and second heating defrost operation the flow control valve 12 and the throttling device 31 are open.
• the flow control valve 12 is fully open, and the throttling device 31 is controlled to the required opening degree.
• the first heating defrost operation is an operation in which high-temperature, high-pressure refrigerant discharged from the compressor 10 is supplied to both the outdoor heat exchanger 40a and the indoor heat exchanger 20, and heating is performed while defrosting the outdoor heat exchanger 40a.
• refrigerant flows through both the second and third paths.
• the second heating defrost operation is an operation in which high-temperature, high-pressure refrigerant discharged from the compressor 10 is supplied to both the outdoor heat exchanger 40b and the indoor heat exchanger 20, and heating is performed while defrosting the outdoor heat exchanger 40b.
• the refrigerant flows through both the first and fourth paths.
• the first heating defrost operation and the second heating defrost operation are permitted to be performed only when the outdoor air temperature is higher than the threshold temperature T.
• the outdoor air temperature is detected, for example, by a temperature sensor provided in the heat source unit 201.
• the threshold temperature T is pre-stored in the memory of the control device 210.
• the threshold temperature T is set, for example, to a temperature within the range of -10°C or higher and -2°C or lower. This makes it possible to suppress a decrease in average heating capacity relative to the outdoor air temperature.
• the first heating defrosting operation and the second heating defrosting operation will be executed alternately. If the conditions for starting defrosting are met during heating operation and the outdoor air temperature is higher than the threshold temperature T, the first defrosting operation and the second defrosting operation will be executed alternately.
• the control device 210 executes the first heating defrost operation and the second heating defrost operation only when the outdoor air temperature is higher than the threshold temperature T.
• the first heating defrost operation is an operation in which the flow control valve 12 and the first throttling device 31 are set to an open state, refrigerant flows through the second and third paths, and heating is performed while defrosting the first outdoor heat exchanger 40a.
• the second heating defrost operation is an operation in which the flow control valve 12 and the first throttling device 31 are set to an open state, refrigerant flows through the first and fourth paths, and heating is performed while defrosting the second outdoor heat exchanger 40b.
• the first outdoor heat exchanger 40a and the second outdoor heat exchanger 40b can be defrosted while heating continues.
• the amount of frost formed per hour is large, performing the first heating defrosting operation and the second heating defrosting operation would result in insufficient defrosting capacity and a decrease in heating capacity, so the first heating defrosting operation and the second heating defrosting operation are not performed.
• control device 210 executes the first defrosting operation and the second defrosting operation when the outdoor air temperature is below 0°C.
• the outdoor heat exchangers 40a, 40b can be defrosted without supplying heat to the indoor heat exchanger 20. This ensures sufficient defrosting capacity while shortening the defrosting time, thereby improving the average heating capacity per hour.

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