AIR-CONDITIONING APPARATUS

Abstract

An air-conditioning apparatus includes: a refrigerant circuit; a branch circuit branching off from the refrigerant circuit at a first connection point that is located between the outdoor heat exchanger and the expansion unit in the refrigerant circuit and is closer to the outdoor heat exchanger than the expansion unit, and joining the refrigerant circuit at a second connection point that is located between the outdoor heat exchanger and the expansion unit and is closer to the expansion unit than the outdoor heat exchanger; and a refrigerant heat exchanger configured to cause heat exchange to be performed between refrigerant that flows in a first flow passage in the refrigerant circuit and refrigerant that flows in a second flow passage in the branch circuit, the first flow passage being located between the compressor and the indoor heat exchanger.

Description

TECHNICAL FIELD

The present disclosure relates to an air-conditioning apparatus including a refrigerant circuit.

BACKGROUND ART

In the past, an air-conditioning apparatus has been known which includes a refrigerant circuit in which a compressor, an outdoor heat exchanger, an expansion unit, and an indoor heat exchanger are sequentially connected by pipes and refrigerant flows. In the air-conditioning apparatus, liquid back can occur. Thus, the liquid back will be described. If refrigerant to be sucked into the compressor is not completely evaporated and is then returned as liquid refrigerant to the compressor, the refrigerant re-expands in the compressor and thus damages the compressor, thus lowering the air-conditioning efficiency of the air-conditioning apparatus. Furthermore, if the air-conditioning apparatus continues to be used in a state in which liquid back occurs, the amount of gas refrigerant that is sucked into the compressor is reduced. Accordingly, the amount of gas refrigerant that can be compressed by the compressor is reduced.

As a structure that prevents occurrence of the liquid back in order to solve the above problem. Patent Literature 1 discloses a structure of a refrigeration apparatus in which at regular intervals, hot gas discharged from a compressor is made to pass through an ejector and flow into the compressor, whereby liquid refrigerant is evaporated.

CITATION LIST

Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2005-24163

SUMMARY OF INVENTION

Technical Problem

However, in the refrigeration apparatus disclosed in Patent Literature 1, in a cooling operation, if foreign matter enters an expansion unit or is caught in the expansion unit, the expansion unit is not completely closed. If the expansion unit is not completely closed, refrigerant leaks from the expansion unit, and flows into an accumulator. Then, if the refrigerant leaking from the expansion unit overflows from the accumulator as liquid refrigerant, it may cause a liquid back in which the liquid refrigerant flows into the compressor.

The present disclosure is applied to solve the above problem, and relates to an air-conditioning apparatus that reduces occurrence of liquid back even if an abnormality occurs in an expansion unit.

Solution to Problem

An air-conditioning apparatus according to an embodiment of the present disclosure includes: a refrigerant circuit in which a compressor, an outdoor heat exchanger, an expansion unit, and an indoor heat exchanger are successively connected by refrigerant pipes, and refrigerant is circulated; a branch circuit branching off from the refrigerant circuit at a first connection point that is located between the outdoor heat exchanger and the expansion unit in the refrigerant circuit and is closer to the outdoor heat exchanger than the expansion unit, and joining the refrigerant circuit at a second connection point that is located between the outdoor heat exchanger and the expansion unit and is closer to the expansion unit than the outdoor heat exchanger; and a refrigerant heat exchanger configured to cause heat exchange to be performed between refrigerant that flows in a first flow passage in the refrigerant circuit and refrigerant that flows in a second flow passage in the branch circuit, the first flow passage being located between the compressor and the indoor heat exchanger.

Advantageous Effects of Invention

According to the present disclosure, the refrigerant heat exchanger causes heat exchange to be performed between refrigerant that flows in the first flow passage and refrigerant that flows in the second flow passage. Thus, in a cooling operation, the refrigerant that flows in the first flow passage is heated by the refrigerant that flows in the second flow passage. As a result, even if liquid refrigerant is present in the first flow passage, it is changed into gas refrigerant. It is therefore possible to reduce occurrence of liquid back even if an abnormality occurs in the expansion unit.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a circuit diagram illustrating an air-conditioning apparatus according to Embodiment 1.

FIG. 2 is a schematic view illustrating an accumulator in Embodiment 1.

FIG. 3 is a circuit diagram illustrating an air-conditioning apparatus according to Embodiment 2.

FIG. 4 is a flowchart indicating an operation of a controller according to Embodiment 2.

DESCRIPTION OF EMBODIMENTS

An air-conditioning apparatus according to each of embodiments of the present disclosure will be described with reference the drawings. It should be noted that in the present disclosure, descriptions concerning the embodiments are not limiting. Furthermore, in figures including FIG. 1 that will be referred to below, relationships in size between components may be different from actual ones. In addition, in the following descriptions, although terms related to directions are used as appropriate in order that the present disclosure be easily understood, they are used to explain the embodiments of the present disclosure; that is, they are not intended to limit the embodiments of the present disclosure. As the terms related to directions, for example, “upper”, “lower”, “right”, “left”, “front”, and “rear” are present.

Embodiment 1

FIG. 1 is a circuit diagram illustrating an air-conditioning apparatus 100 according to Embodiment 1. The air-conditioning apparatus 100 is an apparatus that conditions air in an air-conditioning target space, and as illustrated in FIG. 1, includes an outdoor unit 20, indoor units 30, and a controller 40. In the outdoor unit 20, for example, a compressor 1, a flow switching device 2, an outdoor heat exchanger 3, an outdoor fan 11, an accumulator 7, and a refrigerant heat exchanger 14 are provided. In each of the indoor units 30, for example, an expansion unit 5, an indoor heat exchanger 6, and an indoor fan 12 are provided.

The compressor 1, the flow switching device 2, the outdoor heat exchanger 3, the expansion unit 5, and the indoor heat exchanger 6 are connected by refrigerant pipes 4, whereby a refrigerant circuit 100a is formed. The compressor 1 sucks low-temperature and low-pressure refrigerant, compresses the sucked refrigerant to change it into high-temperature and high-pressure refrigerant, and discharges the high-temperature and high-pressure refrigerant. The compressor 1 is, for example, an inverter compressor whose capacity can be controlled. On a discharge side of the compressor 1, a high pressure sensor 8 is provided. The high pressure sensor 8 detects the pressure of high-pressure refrigerant discharged from the compressor 1. On a suction side of the compressor 1, a low pressure sensor 9 is provided. The low pressure sensor 9 detects the pressure of low-pressure refrigerant that is sucked into the compressor 1.

The flow switching device 2 switches the flow direction of refrigerant that flows in the refrigerant circuit 100a between a plurality of flow directions, and is, for example, a four-way valve. In FIG. 1, solid lines indicate a flow passage for the refrigerant in the flow switching device 2 in a cooling operation, and broken lines indicate a flow passage for the refrigerant in the flow switching device 2 in a heating operation. The outdoor heat exchanger 3 causes heat exchange to be performed between, for example, outdoor air and the refrigerant. The outdoor heat exchanger 3 is, for example, a fin-and-tube type heat exchanger including heat transfer tubes through which the refrigerant flows. The outdoor heat exchanger 3 operates as a condenser in the cooling operation, and operates as an evaporator in the heating operation. The outdoor fan 11 is a device that sends outdoor air to the outdoor heat exchanger 3.

FIG. 2 is a schematic view illustrating the accumulator 7 in Embodiment 1. The accumulator 7 is connected between the flow switching device 2 and the suction side of the compressor 1. The accumulator 7 is provided to store surplus refrigerant that is generated due to a change in an operation mode and an operation condition. As illustrated in FIG. 2, the accumulator 7 includes an inflow pipe 21 into which the refrigerant flows and an outflow pipe 22 from which gas refrigerant flows out toward the compressor 1. The inflow pipe 21 and the outflow pipe 22 are connected to refrigerant pipes 4, whereby a refrigerant circuit 100a is formed.

The accumulator 7 divides refrigerant that flows out from the inflow pipe 21 into gas refrigerant and liquid refrigerant. At a bottom portion of the accumulator 7, the liquid refrigerant is stored. From the outflow pipe 22 of the accumulator 7, the gas refrigerant is let out. In the accumulator 7, refrigeration machine oil that circulates in the refrigerant circuit 100a flows together with the refrigerant into the accumulator 7 and is stored at the bottom portion of the accumulator 7. The refrigeration machine oil stored in the accumulator 7 is returned to the compressor 1 through a all hole formed in the accumulator 7.

It suffices that the capacity of the accumulator 7 is set such that the accumulator 7 is capable of storing a fluid whose maximum volume is estimated as the volume of a fluid that is a combination of surplus refrigerant generated due to a change in the operation mode and the operation condition and refrigeration oil from the compressor 1. The inlet of the outflow pipe 22 for suction of the refrigerant is located such that the level of the inlet is higher than the level of the surface of a fluid that is stored in the accumulator 7. The fluid stored in the accumulator 7 is prevented from leaking from the accumulator 7 and flowing into the compressor 1 from the inlet of the outflow pipe 22.

A branch circuit 100b that branches off from the refrigerant circuit 100a will be described. To be more specific, the branch circuit 100b branches off from the refrigerant circuit 100a at a first connection point 51 that is located between the outdoor heat exchanger 3 and the expansion unit 5 and closer to the outdoor heat exchanger 3 than the expansion unit 5 in the refrigerant circuit 100a, and joins the refrigerant circuit 100a at a second connection point 52 that is located between the outdoor heat exchanger 3 and the expansion unit 5 and closer to the expansion unit 5 than the outdoor heat exchanger 3. In the branch circuit 100b, a check valve 13 is provided.

The check valve 13 is provided in the branch circuit 100b, allows the refrigerant to flow from a first connection point side where the first connection point 51 is located to a second connection point side where the second connection point 52 is located, in the branch circuit 100b, and shuts off the flow of the refrigerant from the second connection point side to the first connection point side in the branch circuit 100b.

The refrigerant heat exchanger 14 is provided between the flow switching device 2 and the indoor heat exchanger 6. The refrigerant heat exchanger 14 causes heat exchange to be performed between refrigerant that flows in a first flow passage 14a located between the compressor 1 and the indoor heat exchanger 6 in the refrigerant circuit 100a and refrigerant that flows in a second flow passage 14b in the branch circuit 100b.

The expansion unit 5 is a pressure reducing valve or an expansion valve. The expansion unit 5 is, for example, an electronic expansion valve whose opening degree is adjusted. The indoor heat exchanger 6 causes heat exchange to be performed between indoor air and the refrigerant, for example. The indoor heat exchanger 6 is, for example, a fin-and-tube type heat exchanger including heat transfer tubes through which the refrigerant flows. The indoor heat exchanger 6 operates as an evaporator in the cooling operation and operates as a condenser in the heating operation. The opening degree of the expansion unit 5 is adjusted such that the difference between the temperature of refrigerant that flows on an inlet side of the indoor heat exchanger 6 and that of refrigerant that flows on an outlet side of the indoor heat exchanger 6 depends on an air-conditioning load. The indoor fan 12 is a device that sends indoor air to the indoor heat exchanger 6. An indoor-unit pipe temperature sensor 10 is provided close to the indoor heat exchanger 6, and detects the temperature of refrigerant that flows in the indoor heat exchanger 6.

The controller 40 is dedicated hardware or a central processing unit (which is also called a CPU, a processing unit, an arithmetic device, a microprocessor, a microcomputer, or a processor) that runs a program stored in a storage device. In the case where the controller 40 is dedicated hardware, the controller 40 corresponds to, for example, a single-component circuit, a composite circuit, an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a combination of these circuits. Function parts of the controller 40 may be implemented by respective hardware or single hardware.

In the case where the controller 40 is a CPU, the functions of the controller 40 are fulfilled by software, firmware or a combination of software and firmware. The software and the firmware are written as programs and stored in the storage device. In order to fulfill each of the functions, the CPU reads out an associated program from the storage device and runs the program. It should be noted that some of the functions of the controller 40 may be fulfilled by dedicated hardware, and others of the functions may be fulfilled by software or firmware. The storage device may be a hard disk or a volatile storage device such as a random access memory (RAM), which can temporarily store data. Alternatively, the storage device may be a non-volatile storage device such as a flash memory, which can store data for a long time period. It should be noted that in Embodiment 1, it is illustrated by way of example that the controller 40 is provided in the outdoor unit 20; however, the controller 40 may be provided in any of the indoor units 30 or an external unit.

Operation Mode, Cooling Operation

Next, an operation mode of the air-conditioning apparatus 100 will be described. First of all, the cooling operation will be described. In the cooling operation, refrigerant sucked into the compressor 1 is compressed by the compressor 1 to change into high-temperature and high-pressure gas refrigerant, and the high-temperature and high-pressure gas refrigerant is then discharged from the compressor 1. The high-temperature and high-pressure gas refrigerant discharged from the compressor 1 passes through the flow switching device 2, flows into the outdoor heat exchanger 3 operating as a condenser, and exchanges at the outdoor heat exchanger 3, heat with outdoor air sent by the outdoor fan 11 to condense and liquefy. The refrigerant that has condensed and liquefied branches into refrigerant streams at the first connection point 51. The refrigerant stream that has flowed into the branch circuit 100b at the first connection point 51 passes through the check valve 13, reaches the refrigerant heat exchanger 14, and then joins refrigerant that flows in the refrigerant circuit 100a, at the second connection point 52. The refrigerant stream that has not flowed into the branch circuit 100b at the first connection point 51 passes through the second connection point 52, flows into the expansion unit 5, and is expanded and reduced in pressed at the expansion unit 5 to change into low-temperature and low-pressure two-phase gas-liquid refrigerant.

Then, the two-phase gas-liquid refrigerant flows into the indoor heat exchanger 6 operating as an evaporator, and exchanges at the indoor heat exchanger 6, heat with indoor air sent by the indoor fan 12 to evaporate and gasify. At this time, the indoor air is cooled and cooling is performed in an indoor space. The low-temperature and low-pressure gas refrigerant that has evaporated flows into the refrigerant heat exchanger 14, and exchanges heat with refrigerant that flows in the branch circuit 100b to further evaporate and gasify. After that, the refrigerant that has sufficiently gasified passes through the flow switching device 2 and the accumulator 7, and is sucked into the compressor 1.

Operation Mode, Heating Operation

Next, the heating operation will be described. In the heating operation, refrigerant sucked into the compressor 1 is compressed by the compressor 1 to change into high-temperature and high-pressure gas refrigerant, and the high-temperature and high-pressure gas refrigerant is then discharged from the compressor 1. The high-temperature and high-pressure gas refrigerant discharged from the compressor 1 passes through the flow switching device 2 and the refrigerant heat exchanger 14, flows into the indoor heat exchanger 6 operating as a condenser, and exchanges, at the indoor heat exchanger 6, heat with indoor air sent by the indoor fan 12 to condense and liquefy. At this time, the indoor air is heated, and heating is performed in the indoor space. The refrigerant that has condensed and liquefied flows into the expansion unit 5, and is expanded and reduced in pressured at the expansion unit 5 to change into low-temperature and low-pressure two-phase gas-liquid refrigerant.

Then, the two-phase gas-liquid refrigerant reaches the second connection point 52. Since the check valve 13 is provided in the branch circuit 100b, the refrigerant that has reached the second connection point 52 does not flow into the branch circuit 100b. The refrigerant that has passed through the second connection point 52 passes through the first connection point 51, flows into the outdoor heat exchanger 3 operating as an evaporator, and exchanges at the outdoor heat exchanger 3, heat with outdoor air sent by the outdoor fan 11 to evaporate and gasify. The low-temperature and low-pressure gas refrigerant that has evaporated passes through the flow switching device 2 and the accumulator 7, and is sucked into the compressor 1.

Flow and Change of Refrigerant in Case where Clogging Occurs in Expansion Unit 5

In the cooling operation, in the case where any of the indoor units 30 is stopped, the compressor 1 is kept operating, the refrigerant flows into the refrigerant circuit 100a, and in addition, by control by the controller 40, the expansion unit 5 in the above stopped indoor unit 30 is closed and the indoor fan 12 in the stopped indoor unit 30 is stopped. If the expansion unit 5 is clogged with foreign matter caught in the expansion unit 5, high-temperature liquid refrigerant that has flowed out of the outdoor heat exchanger 3 is not blocked by the expansion unit 5, and leaks from the expansion unit 5. The refrigerant that has leaked from the expansion unit 5 is changed into low-pressure two-phase refrigerant by the expansion unit 5, and the low-pressure two-phase refrigerant then flows to reach the indoor heat exchanger 6.

In the above case, since the indoor fan 12 is in the stopped state, and heat exchange is not performed at the indoor heat exchanger 6, the low-pressure two-phase refrigerant cannot receive heat from the indoor air, and thus does not change into gas refrigerant. Accordingly, the low-pressure two-phase refrigerant flows out of the indoor heat exchanger 6 while being kept in the two-phase state. Then, the low-pressure two-phase refrigerant passes through the first flow passage 14a in the refrigerant heat exchanger 14. In this process, the low-pressure two-phase refrigerant exchanges heat with high-temperature liquid refrigerant that flows in the second flow passage 14b in the branch circuit 100b.

As a result, the low-pressure two-phase refrigerant evaporates to change into gas refrigerant, then flows into the accumulator 7 through the flow switching device 2, and is subsequently sucked into the compressor 1. Even if high-temperature liquid refrigerant unintentionally leaks from the expansion unit 5 due to clogging that occurs in the expansion unit 5, the high-temperature liquid refrigerant flows into the refrigerant heat exchanger 14 and is thus changed into gas refrigerant, and the gas refrigerant is then sucked into the compressor 1. In such a manner, because of provision of the refrigerant heat exchanger 14, liquid refrigerant is hardly sucked into the compressor 1. It is therefore possible to prevent occurrence of liquid back in the compressor 1 without using a specific device such as an ejector.

According to Embodiment 1, the refrigerant heat exchanger 14 causes heat exchange to be performed between refrigerant that flows in the first flow passage 14a and refrigerant that flows in the second flow passage 14b. Thus, in the cooling operation, the refrigerant that flows in the first flow passage 14a is heated by the refrigerant that flows in the second flow passage 14b. Accordingly, even if the liquid refrigerant is present in the first flow passage 14a, it is changed into gas refrigerant. It is therefore possible to reduce occurrence of liquid back even if an abnormality occurs in the expansion unit 5.

Embodiment 2

FIG. 3 is a circuit diagram illustrating an air-conditioning apparatus 200 according to Embodiment 2. In Embodiment 2, the refrigerant heat exchanger 14 and the check valve 13 of Embodiment 1 are not provided, and a refrigerant flow control valve 13a is provided. In this regard, Embodiment 2 is different from Embodiment 1. Regarding Embodiment 2, components that are the same as those in Embodiment 1 will be denoted by the same reference signs, and their descriptions will thus be omitted. The following description is made by referring mainly to the differences between Embodiments 1 and 2.

As illustrated in FIG. 3, the refrigerant flow control valve 13a is connected to the branch circuit 100b. The refrigerant flow control valve 13a adjusts the flow rate of refrigerant that flows in the branch circuit 100b.

The air-conditioning apparatus 200 further includes a temperature detector 15. The temperature detector 15 is provided on a suction side of the compressor 1 and detects the temperature of refrigerant that flows on the suction side of the compressor 1.

When the temperature detected by the temperature detector 15 is higher than or equal to a threshold temperature determined in advance, the controller 40 increases the opening degree of the refrigerant flow control valve 13a. Ordinarily, the temperature of liquid refrigerant is higher than that of gas refrigerant. Thus, in Embodiment 2, when the temperature of the refrigerant that flows on the suction side of the compressor 1 is higher than or equal to the threshold temperature, in many cases, the refrigerant is liquid refrigerant. Thus, in this case, it is determined that there is a possibility that liquid back will occur. Then, when it is determined that there is a possibility that liquid back will occur, the opening degree of the refrigerant flow control valve 13a is increased, thereby adjusting the flow rate of refrigerant that flows in the branch circuit 100b and that of refrigerant that flows in the refrigerant circuit 100a. As a result, liquid refrigerant is hardly sucked into the compressor 1, and it is therefore possible to prevent occurrence of liquid back in the compressor 1 without using a specific device such as an ejector.

Operation of Controller 40

FIG. 4 is a flowchart indicating an operation of the controller 40 according to Embodiment 2. Next, an operation of the controller 40 will be described. As illustrated in FIG. 4, in the case where the air-conditioning apparatus 200 is in the cooling operation, the controller 40 determines whether or not the temperature detected by the temperature detector 15 is higher than or equal to the threshold temperature (step ST01). When the detected temperature is lower than the threshold temperature (No in step ST01), the controller 40 determines that there is a small possibility that liquid back will occur, and causes the opening degree of the refrigerant flow control valve 13a to be zero (step ST02). In contrast, when the detected temperature is higher than or equal to the threshold temperature (Yes in step ST01), the controller 40 determines that there is a possibility that liquid back will occur, and increases the opening degree of the refrigerant flow control valve 13a (step ST03). As a result, liquid refrigerant is hardly sucked into the compressor 1, and it is therefore possible to prevent occurrence of liquid back in the compressor 1.

After that, the controller 40 determines whether the temperature detected by the temperature detector 15 is lower than the threshold temperature or not (step ST04). When the temperature is higher than or equal to the threshold temperature (No in step ST04), the controller 40 determines that there is still a possibility that liquid back will occur, and the processing returns to step ST04. In contrast, when the temperature is lower than the temperature threshold (Yes in step ST04), the controller 40 determines that there is a small possibility that liquid back will occur, and causes the opening degree of the refrigerant flow control valve 13a to be zero (step ST05).

According to Embodiment 2, when the temperature detected by the temperature detector 15 is higher than or equal to the threshold temperature determined in advance, the controller 40 increases the opening degree of the refrigerant flow control valve 13a. As a result, liquid refrigerant is hardly sucked into the compressor 1, and it is therefore possible to prevent occurrence of liquid back in the compressor 1.

Regarding Embodiment 2, although the above description refers to by way of example the case where neither the refrigerant heat exchanger 14 nor the check valve 13 is provided, the refrigerant heat exchanger 14 and the check valve 13 may be provided. In this case, control of the refrigerant flow control valve 13a and that of the refrigerant heat exchanger 14 can be both exerted based on the possibility that liquid back will occur.

REFERENCE SIGNS LIST

1: compressor, 2: flow switching device, 3: outdoor heat exchanger, 4: refrigerant pipe, 5: expansion unit, 6: indoor heat exchanger, 7: accumulator, 8: high pressure sensor, 9: low pressure sensor, 10: indoor-unit pipe temperature sensor, 11: outdoor fan, 12: indoor fan, 13: check valve, 13a: refrigerant flow control valve, 14: refrigerant heat exchanger, 14a: first flow passage, 14b: second flow passage, 15: temperature detector, 20: outdoor unit, 21: inflow pipe, 22: outflow pipe, 23: small hole, 30: indoor unit, 40: controller, 51: first connection point, 52: second connection point, 100: air-conditioning apparatus, 100a: refrigerant circuit, 100b: branch circuit, 200: air-conditioning apparatus

Claims

1. An air-conditioning apparatus comprising: a refrigerant circuit in which a compressor, an outdoor heat exchanger, an expansion unit, and an indoor heat exchanger are successively connected by refrigerant pipes, and refrigerant is circulated;a branch circuit branching off from the refrigerant circuit at a first connection point that is located between the outdoor heat exchanger and the expansion unit in the refrigerant circuit and is closer to the outdoor heat exchanger than the expansion unit, and joining the refrigerant circuit at a second connection point that is located between the outdoor heat exchanger and the expansion unit and is closer to the expansion unit than the outdoor heat exchanger;a refrigerant heat exchanger configured to cause heat exchange to be performed between refrigerant that flows in a first flow passage in the refrigerant circuit and refrigerant that flows in a second flow passage in the branch circuit, the first flow passage being located between the compressor and the indoor heat exchange;a refrigerant flow control valve connected to the branch circuit and configured to adjust a flow rate of refrigerant that flows in the branch circuit;a temperature detector configured to detect a temperature of refrigerant that flows on a suction side of the compressor; anda controller configured to increase an opening degree of the refrigerant flow control valve when the temperature detected by the temperature detector is higher than or equal to a threshold temperature determined in advance.

2. The air-conditioning apparatus of claim 1, further comprising a check valve provided at the branch circuit, and configured to allow the refrigerant to flow from a first connection point side where the first connection point is located to a second connection point side where the second connection point is located, and shut off a flow of the refrigerant from the second connection point side to the first connection point side.

3. (canceled)

4. An air-conditioning apparatus comprising: a refrigerant circuit in which a compressor, an outdoor heat exchanger, an expansion unit, and an indoor heat exchanger are successively connected by refrigerant pipes and refrigerant is circulated, the outdoor heat exchanger and the expansion unit being directly connected to each other:a branch circuit branching off from the refrigerant circuit at a first connection point that is located between the outdoor heat exchanger and the expansion unit and is closer to the outdoor heat exchanger than the expansion unit, and joining the refrigerant circuit at a second connection point that is located between the outdoor heat exchanger and the expansion unit and is closer to the expansion unit than the outdoor heat exchanger;a refrigerant flow control valve connected to the branch circuit and configured to adjust a flow rate of refrigerant that flows in the branch circuit;a temperature detector configured to detect a temperature of refrigerant that flows on a suction side of the compressor, anda controller configured to increase an opening degree of the refrigerant flow control valve when the temperature detected by the temperature detector is higher than or equal to a threshold temperature determined in advance.