JP7224480B2 - Outdoor unit and refrigeration cycle equipment - Google Patents

Description

The present invention relates to an outdoor unit and a refrigerating cycle device.

Japanese Patent Laying-Open No. 2014-01917 (Patent Document 1) discloses a refrigeration system having an intermediate injection channel and a suction injection channel. In this refrigeration system, part of the refrigerant flowing from the condenser to the evaporator can be combined with the intermediate pressure refrigerant in the compressor using the intermediate injection channel, or the suction injection channel can be used to join the suction channel. It is also possible to join the low-pressure refrigerant sucked into the compressor at . Therefore, when the use of the intermediate injection flow path deteriorates the operating efficiency, the suction injection flow path can be used to lower the discharge temperature of the compressor.

JP 2014-01917 A

In the main refrigerant circuit, an on-off valve is installed in the pipe through which the liquid refrigerant flows, and the compressor is operated with the pipe cut off to move the refrigerant from the load device to the outdoor unit and store it in the pump-down operation. .

In the refrigeration system described in Japanese Patent Application Laid-Open No. 2014-01917 (Patent Document 1), the operation of the load device is stopped, etc., and the flow of the refrigerant is interrupted on the indoor unit side, and the load device side performs the pump-down operation. Once started, refrigerant in the load device is collected in the outdoor unit. At this time, as refrigerant recovery progresses and the amount of refrigerant in the high-pressure section decreases, the condensation temperature approaches the outside air temperature, making it difficult for the condenser to liquefy. There is a problem of storage.

SUMMARY OF THE INVENTION An object of the present invention is to provide an outdoor unit and a refrigeration cycle apparatus in which the refrigerant recovery time during pump-down operation is shortened.

The present disclosure relates to an outdoor unit of a refrigeration cycle apparatus configured to be connected to a load device including a first expansion device and an evaporator. The outdoor unit includes a first flow path forming a circulation flow path in which the refrigerant circulates by being connected to a load device, a compressor and a condenser arranged in the first flow path, and a direction in which the refrigerant circulates. , a second flow path branched from a branch point of the first flow path downstream of the condenser and configured to return the refrigerant that has passed through the condenser to the compressor, and from the branch point to the second flow path in order a second expansion device, a liquid receiver and a flow control valve disposed thereon; a first passage and a second passage; and a heat exchanger configured to A first passage of the heat exchanger is disposed between the condenser and the branch point of the first flow path. A second passageway of the heat exchanger is disposed between the flow control valve in the second flowpath and the compressor. The flow control valve is configured to adjust the discharge flow rate of the liquid refrigerant from the liquid receiver. When the pump-down operation for collecting the refrigerant in the liquid receiver is started, the control state of the compressor and the flow control valve is the first state in which the compressor is operated and the flow control valve is closed at the first time point. . At a second point in time after the first point in time during the pump-down operation, the control state transitions from the first state to a second state in which the flow control valve is opened while operating the compressor.

According to the outdoor unit of the present disclosure, the efficiency of the heat exchanger is maintained and the refrigerant is condensed even when the refrigerant recovery proceeds and the condensing temperature approaches the outside air temperature during the pump-down operation. Therefore, the time required for refrigerant recovery can be shortened.

1 is an overall configuration diagram of a refrigeration cycle apparatus according to an embodiment; FIG. 7 is a flow chart for explaining control of the second expansion valve 71. FIG. 7 is a flowchart for explaining control of a flow rate adjustment valve 72; 4 is a flowchart for explaining control during pump-down operation;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. A plurality of embodiments will be described below, but appropriate combinations of the configurations described in the respective embodiments have been planned since the filing of the application. The same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated.

FIG. 1 is an overall configuration diagram of a refrigeration cycle apparatus according to this embodiment. Note that FIG. 1 functionally shows the connection relationship and arrangement configuration of each device in the refrigeration cycle apparatus, and does not necessarily show the arrangement in a physical space.

Referring to FIG. 1, the refrigeration cycle device 1 includes an outdoor unit 2, a load device 3, and pipes 84,88. The outdoor unit 2 has a refrigerant outlet port PO2 and a refrigerant inlet port PI2 for connecting with the load device 3 . The load device 3 has a refrigerant outlet port PO3 and a refrigerant inlet port PI3 for connecting with the outdoor unit 2 . A pipe 84 connects the refrigerant outlet port PO2 of the outdoor unit 2 and the refrigerant inlet port PI3 of the load device 3 . A pipe 88 connects the refrigerant outlet port PO3 of the load device 3 and the refrigerant inlet port PI2 of the outdoor unit 2 .

The outdoor unit 2 of the refrigeration cycle device 1 is configured to be connected to the load device 3 . The outdoor unit 2 includes a compressor 10 having an intake port G1, a discharge port G2 and an intermediate pressure port G3, a condenser 20, a fan 22, a heat exchanger 30, and pipes 80-82 and 89. The heat exchanger 30 has a first passage H1 and a second passage H2, and is configured to exchange heat between the refrigerant flowing through the first passage H1 and the refrigerant flowing through the second passage H2.

The load device 3 includes a first expansion valve 50 , an evaporator 60 , pipes 85 , 86 and 87 and an on-off valve 28 . Evaporator 60 is configured to exchange heat between the air and the refrigerant. In the refrigeration cycle device 1, the evaporator 60 evaporates the refrigerant by absorbing heat from the air in the space to be cooled. The first expansion valve 50 is, for example, a temperature expansion valve controlled independently of the outdoor unit 2 . Note that the first expansion valve 50 may be an electronic expansion valve capable of reducing the pressure of the refrigerant. The on-off valve 28 is closed to shut off the refrigerant when the load device 3 stops operating.

The compressor 10 compresses the refrigerant sucked from the pipe 89 and discharges it to the pipe 80 . Compressor 10 can arbitrarily change the driving frequency by inverter control. In addition, the compressor 10 is provided with an intermediate pressure port G3, and the refrigerant from the intermediate pressure port G3 can flow into the intermediate portion of the compression process. Compressor 10 is configured to adjust its rotational speed according to a control signal from control device 100 . By adjusting the rotational speed of the compressor 10, the circulation amount of the refrigerant is adjusted, and the capacity of the refrigeration cycle device 1 can be adjusted. Various types can be adopted for the compressor 10, for example, a scroll type, a rotary type, a screw type, etc. can be adopted.

Condenser 20 is configured such that the high-temperature, high-pressure gas refrigerant discharged from compressor 10 exchanges heat (radiates heat) with the outside air. This heat exchange causes the refrigerant to condense and change to a liquid phase. Refrigerant discharged from compressor 10 to pipe 80 is condensed and liquefied in condenser 20 and flows out to pipe 81 . A fan 22 is attached to the condenser 20 to send outside air to increase the efficiency of heat exchange. The fan 22 supplies outside air to the condenser 20 with which the refrigerant exchanges heat in the condenser 20 . By adjusting the rotational speed of the fan 22, the pressure of the refrigerant on the discharge side of the compressor 10 (high-pressure side pressure) can be adjusted.

Here, the refrigerant used in the refrigerant circuit of the refrigeration cycle device 1 is CO ₂ , but other refrigerants may be used when a state occurs in which it is difficult to secure the degree of supercooling.

In this specification, for ease of explanation, the condenser 20 is also used when cooling a refrigerant such as CO ₂ in a supercritical state. Further, in this specification, for ease of explanation, the amount of decrease from the reference temperature of the refrigerant in the supercritical state is also referred to as the degree of supercooling.

A first flow path F1 from the refrigerant inlet port PI2 to the refrigerant outlet port PO2 via the first passage H1 of the compressor 10, the condenser 20, and the heat exchanger 30 is connected to the first expansion valve 50 of the load device 3 and the evaporator. Together with the flow path in which the container 60 is arranged, a circulation flow path through which the coolant circulates is formed. Hereinafter, this circulation flow path is also referred to as the "main refrigerant circuit" of the refrigeration cycle.

The outdoor unit 2 includes pipes 91, 92, and 94 for flowing the refrigerant from the portion between the outlet of the first passage H1 of the circulation flow path and the refrigerant outlet port PO2 to the inlet of the second passage H2, and the second passage H2. A pipe 96 for flowing the refrigerant from the outlet to the intermediate pressure port G3 of the compressor 10 is further provided. Hereinafter, the second flow path F2 that branches from the main refrigerant circuit and sends the refrigerant to the compressor 10 via the second passage H2 is also referred to as an "injection flow path".

The outdoor unit 2 further includes a liquid receiver (receiver) 73 that is arranged in the second flow path F2 and stores the refrigerant. The second expansion valve 71 is arranged between a pipe 91 branched from a portion between the outlet of the first passage H1 of the circulation flow path and the refrigerant outlet port PO2 and a pipe 92 connected to the inlet of the liquid receiver 73. be done. The outdoor unit 2 further includes a gas vent pipe 93 that connects the gas discharge port of the liquid receiver 73 and the second passage H2 and discharges the refrigerant gas in the liquid receiver 73, the gas vent pipe 93 and the second passage H2. and a flow control valve 72 for adjusting the flow rate of the refrigerant in the pipe 94 connected to the liquid refrigerant discharge port of the liquid receiver 73 .

A pipe 91 is a pipe that branches off from the main refrigerant circuit and allows the refrigerant to flow into the liquid receiver 73 . The second expansion valve 71 is an electronic expansion valve capable of reducing the pressure of the refrigerant in the high pressure section of the main refrigerant circuit to an intermediate pressure. The liquid receiver 73 is a container capable of separating the vapor phase and the liquid phase of the pressure-reduced two-phase refrigerant in the container, storing the refrigerant, and adjusting the circulation amount of the refrigerant in the main refrigerant circuit. A degassing pipe 93 connected to the upper part of the liquid receiver 73 and a pipe 94 connected to the lower part of the liquid receiver 73 separate the gas refrigerant and the liquid refrigerant in the liquid receiver 73 from each other. It is a pipe for taking out. The flow control valve 72 can adjust the amount of refrigerant in the liquid receiver 73 by adjusting the amount of liquid refrigerant discharged from the pipe 94 .

By providing the liquid receiver 73 in the injection flow path in this way, it becomes easy to ensure the degree of supercooling in the pipes 82 and 83 which are liquid pipes. This is because gas refrigerant generally exists in the liquid receiver 73, and the temperature of the refrigerant reaches the saturation temperature.

Further, if the liquid receiver 73 is provided in the intermediate pressure portion, even when the pressure in the high pressure portion of the main refrigerant circuit is high and the refrigerant is in a supercritical state, the intermediate pressure liquid refrigerant can be stored inside the liquid receiver 73. It becomes possible. Therefore, the design pressure of the container of the liquid receiver 73 can be made lower than that of the high-pressure part, and cost reduction can be achieved by making the container thinner.

The outdoor unit 2 further includes pressure sensors 110 and 111, temperature sensors 120 to 123, and a controller 100 that controls the compressor 10, the second expansion valve 71, and the flow control valve 72.

Pressure sensor 110 detects pressure PL at the suction port of compressor 10 and outputs the detected value to control device 100 . Pressure sensor 111 detects the discharge pressure PH of compressor 10 and outputs the detected value to control device 100 .

Temperature sensor 120 detects a discharge temperature TH of compressor 10 and outputs the detected value to control device 100 . Temperature sensor 121 detects refrigerant temperature T<b>1 in piping 81 at the outlet of condenser 20 and outputs the detected value to control device 100 . Temperature sensor 122 detects refrigerant temperature T<b>2 at the outlet of first passage H<b>1 on the cooled side of heat exchanger 30 and outputs the detected value to control device 100 . Temperature sensor 123 detects outside air temperature TA, which is the ambient temperature of outdoor unit 2 , and outputs the detected value to control device 100 .

In the present embodiment, the second flow path F2 controls the discharge temperature TH of the compressor 10 by causing the two-phase refrigerant to flow into the compressor 10 after being decompressed. In addition, the amount of refrigerant in the main refrigerant circuit can be adjusted by the liquid receiver 73 installed on the second flow path F2. Furthermore, the second flow path F2 also ensures supercooling of the refrigerant in the main refrigerant circuit by heat exchange by the heat exchanger 30 .

The control device 100 includes a CPU (Central Processing Unit) 102, a memory 104 (ROM (Read Only Memory) and RAM (Random Access Memory)), an input/output buffer (not shown) for inputting and outputting various signals, and the like. Consists of The CPU 102 expands a program stored in the ROM into the RAM or the like and executes it. The program stored in the ROM is a program in which processing procedures of the control device 100 are described. The control device 100 controls each device in the outdoor unit 2 according to these programs. This control is not limited to processing by software, and processing by dedicated hardware (electronic circuit) is also possible.

(Control during normal operation)
The control device 100 feedback-controls the second expansion valve 71 so that the discharge temperature TH of the compressor 10 matches the target temperature.

FIG. 2 is a flow chart for explaining the control of the second expansion valve 71. As shown in FIG. When the discharge temperature TH of the compressor 10 is higher than the target temperature (YES in S21), the control device 100 increases the degree of opening of the second expansion valve 71 (S22). As a result, the amount of refrigerant flowing into the intermediate pressure port G3 via the liquid receiver 73 increases, so the discharge temperature TH decreases.

On the other hand, when the discharge temperature TH of the compressor 10 is lower than the target temperature (NO in S21 and YES in S23), the control device 100 reduces the opening of the second expansion valve 71 (S24). As a result, the amount of refrigerant flowing into the intermediate pressure port G3 via the liquid receiver 73 is reduced, and the discharge temperature TH rises.

If the discharge temperature TH=the target temperature (NO in S21 and NO in S23), the control device 100 maintains the current opening of the second expansion valve 71 .

In this manner, the control device 100 controls the degree of opening of the second expansion valve 71 so that the discharge temperature TH of the compressor 10 approaches the target temperature.

In order to ensure the subcooling degree SC of the refrigerant at the outlet of the condenser 20 during normal operation, the control device 100 feeds back the flow control valve 72 so that the refrigerant temperature T1 at the outlet of the condenser 20 matches the target temperature. Control.

FIG. 3 is a flow chart for explaining the control of the flow regulating valve 72. As shown in FIG. If the degree of supercooling SC determined by the refrigerant temperature T1 at the outlet of the condenser 20 and the pressure (approximate by PH) of the condenser 20 is greater than the target value (YES in S31), the control device 100 closes the flow regulating valve 72 is decreased (S32). As a result, the amount of liquid refrigerant discharged from the liquid receiver 73 decreases and the amount of liquid refrigerant in the liquid receiver 73 increases, so the amount of refrigerant circulating in the main refrigerant circuit decreases and the refrigerant temperature T1 rises. Therefore, the degree of supercooling SC decreases.

On the other hand, when the degree of supercooling SC determined by the refrigerant temperature T1 at the outlet of the condenser 20 and the pressure (approximate by PH) of the condenser 20 is smaller than the target value (NO in S31 and YES in S33), the control device 100 , the opening degree of the flow control valve 72 is increased (S34). As a result, the amount of liquid refrigerant discharged from the liquid receiver 73 increases and the amount of liquid refrigerant stored in the liquid receiver 73 decreases. Since it decreases, the degree of supercooling SC increases.

If the degree of supercooling SC=the target value (NO in S31 and NO in S33), the control device 100 maintains the opening degree of the flow control valve 72 at the current state.

Thus, the control device 100 controls the degree of opening of the flow control valve 72 so that the refrigerant temperature T1 at the outlet of the condenser 20 approaches the target temperature.

(Control during pump-down operation)
In order to ensure the subcooling degree SC of the refrigerant at the outlet of the condenser 20 during normal operation, the control device 100 feeds back the flow control valve 72 so that the refrigerant temperature T1 at the outlet of the condenser 20 matches the target temperature. In the pump-down operation, the flow control valve 72 is closed and the liquid refrigerant is collected in the liquid receiver 73 .

An on-off valve 28 or the like is installed in the pipe 85 through which the liquid refrigerant flows in the main refrigerant circuit, and the compressor 10 is operated with the pipe 85 cut off to move the refrigerant from the load device 3 to the outdoor unit 2 and store it. This is called pump-down operation. The pump-down operation is performed by, for example, operating the compressor 10 after closing the first expansion valve 50 or closing the on-off valve 28 before stopping the operation.

In general, the signal instructing the start of the pump-down operation is not particularly transmitted from the load device 3 side to the outdoor unit 2, and in the outdoor unit 2, the pressure PL of the low pressure portion detected by the pressure sensor 110 is the threshold value. A pump-down operation is executed by continuing normal operation when the pressure drops to PA.

In the pump-down operation, when the on-off valve 28 is closed and the pressure PL of the low-pressure portion detected by the pressure sensor 110 drops to the threshold value PB, the controller 100 stops the compressor 10 to stop the pump-down. It has become. Since the compressor 10 is configured so that the refrigerant does not pass through it in the stopped state, the refrigerant does not flow back to the load device 3 .

FIG. 4 is a flowchart for explaining control during pump-down operation. First, in step S41, control device 100 determines whether or not pressure PL of the low pressure portion detected by pressure sensor 110 is lower than threshold value PA. If PL<threshold value PA is established (YES in S41), the pump down operation is executed in step S42 and subsequent steps. On the other hand, when PL<threshold PA does not hold (NO in S41), the control returns to normal operation processing in step S47 without executing the pump-down operation.

In step S42, control device 100 determines whether refrigerant temperature T1 in condenser 20 is lower than TA+α. Here, α represents the temperature difference at which the efficiency of condensing the refrigerant in the condenser 20 significantly decreases if the temperature difference between the refrigerant and the outside air becomes smaller, and is a value that is appropriately determined.

If not T1<TA+α (NO in S42), the control device 100 closes the flow control valve 72 in step S43. As a result, the gas refrigerant is discharged from the liquid receiver 73 through the degassing pipe 93 , and the liquid refrigerant is recovered in the liquid receiver 73 .

On the other hand, if T1<TA+α (YES in S42), control device 100 slightly increases the opening of flow rate control valve 72 in step S44. Thereby, the liquid refrigerant stored in the liquid receiver 73 flows into the second passage H2 of the heat exchanger 30 . When the flow regulating valve 72 is closed, the gas refrigerant is flowing through the second passage H2 of the heat exchanger 30 from the degassing pipe 93 . When the gas refrigerant flows, the heat transfer coefficient between the refrigerant and the heat exchanger in the second passage H2 is low.

Here, if the liquid refrigerant is mixed by slightly opening the flow control valve 72, the heat transfer coefficient between the refrigerant and the heat exchanger in the second passage H2 is improved tenfold or more. As a result, the refrigerant, which is difficult to be condensed in the condenser 20 when the recovery of the liquid refrigerant has progressed to a certain extent, is condensed in the heat exchanger 30, so that the recovery of the liquid refrigerant can be advanced. If the opening of the flow rate control valve 72 is too large, the amount of liquid refrigerant recovered will not increase. within the range of

Although not necessarily performed, preferably, control device 100 further increases the rotational speed of compressor 10 in step S45 . This makes it possible to shorten the recovery time of the remaining refrigerant that has progressed in recovery and has become difficult to condense.

Subsequently, in step S46, control device 100 determines whether or not pressure PL of the low pressure portion detected by pressure sensor 110 has decreased to threshold value PB. Threshold PB is a value lower than threshold PA, and is a determination value for determining that recovery of the refrigerant in load device 3 has been completed. Until pressure PL has decreased to threshold value PB (NO in S46), control device 100 continues the operation of compressor 10 to continue the pump-down operation.

On the other hand, when pressure PL has decreased to threshold value PB (YES in S46), control device 100 stops compressor 10 in step S47 to complete pump-down.

By controlling in this way, the control device 100 closes the flow control valve 72 to store the liquid refrigerant in the liquid receiver 73 at the first point in time when the pump-down operation is started. Then, at the second point in time when the amount of liquid refrigerant in the liquid receiver 73 increases and the efficiency of the condenser 20 decreases, the control device 100 slightly opens the flow control valve 72 to improve the efficiency of the heat exchanger 30. to promote condensation of the refrigerant in the first passage H1. As a result, it is possible to shorten the time until the pump-down operation is completed.

Finally, the present embodiment will be summarized with reference to the drawings again. As shown in FIG. 1, the present disclosure provides an outdoor unit of a refrigeration cycle device 1 configured to be connected to a load device 3 including a first expansion valve 50 and an evaporator 60 corresponding to a "first expansion device". 2. The outdoor unit 2 is connected to the load device 3 to include a first flow path F1 that forms a circulation flow path in which the refrigerant circulates, and a compressor 10 and a condenser 20 that are arranged in the first flow path F1. , a second flow path F2 branched from a branch point of the first flow path F1 downstream of the condenser 20 in the direction in which the refrigerant circulates, and configured to return the refrigerant that has passed through the condenser 20 to the compressor 10. , a second expansion valve 71, a liquid receiver 73, a flow control valve 72, a first passage H1 and a second passage, which correspond to a "second expansion device" and are arranged in the second flow path F2 in order from the branch point. H2 and configured to exchange heat between the refrigerant flowing through the first passage H1 and the refrigerant flowing through the second passage H2;

The first passage H1 of the heat exchanger 30 is arranged between the condenser 20 and the branch point of the first flow path F1. The second passage H2 of the heat exchanger 30 is arranged between the flow control valve 72 of the second flow passage F2 and the compressor 10 . The flow control valve 72 is configured to adjust the flow rate of liquid refrigerant discharged from the liquid receiver 73 .

Controller 100 is configured to control compressor 10 and flow control valve 72 . When starting the pump-down operation for recovering the refrigerant in the liquid receiver 73, the control device 100 sets the control states of the compressor 10 and the flow rate adjustment valve 72 at the first point of time to adjust the flow rate while operating the compressor 10. Control the first state in which the valve 72 is closed. The control device 100 is configured to transition from the first state to the second state in which the flow control valve 72 is opened while operating the compressor 10 at a second time point after the first time point during the pump-down operation. be.

As the pump-down operation progresses, recovery of the refrigerant to the liquid receiver 73 progresses, so the amount of liquid refrigerant in the liquid receiver 73 gradually increases. Therefore, the amount of liquid refrigerant in the liquid receiver 73 at the second time is greater than the amount of liquid refrigerant in the liquid receiver 73 at the first time.

Preferably, control device 100 changes the control state of compressor 10 and flow control valve 72 to the second state when the difference between the condensation temperature of the refrigerant in condenser 20 and the outside air temperature becomes smaller than a threshold value. Control. As a result, even if the difference between the refrigerant temperature T1 in the condenser 20 and the outside air temperature TA becomes small and the efficiency of the condenser 20 is lowered at the stage where the recovery of the liquid refrigerant to the liquid receiver 73 has progressed, the heat is The efficiency of the exchanger 30 can be improved to further promote the recovery of the liquid refrigerant.

If the opening degree of the flow control valve 72 in the second state is fully opened for a long time, the amount of liquid refrigerant in the liquid receiver 73 will decrease. Therefore, in the second state, it is sufficient to open the flow control valve 72 with a slight degree of opening such that an annular flow of the liquid refrigerant is generated in the second passage H2 of the heat exchanger 30, or to repeat opening and closing for a short period of time. . As a result, the heat exchange efficiency of the heat exchanger 30 is improved, and the refrigerant passing through the first passage H1 is condensed in the heat exchanger 30, thereby facilitating recovery of the liquid refrigerant.

More preferably, control device 100 is configured to make the rotation speed of compressor 10 in the second state higher than the rotation speed of compressor 10 in the first state. As a result, it is possible to shorten the recovery time of the remaining refrigerant that has progressed in recovery and has become difficult to condense.

Although the refrigerator including the refrigerating cycle device 1 has been described above as an example, the refrigerating cycle device 1 may be used in an air conditioner or the like.

The embodiments disclosed this time should be considered as examples and not restrictive in all respects. The scope of the present invention is indicated by the scope of the claims rather than the description of the above-described embodiments, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

Reference Signs List 1 refrigerating cycle device 2 outdoor unit 3 load device 10 compressor 20 condenser 22 fan 28 on-off valve 30 heat exchanger 71 second expansion valve 50 first expansion valve 60 evaporator 70 Expansion device 72 Flow control valve 73 Receiver 8 0, 81, 82, 83, 84, 85, 88, 89, 91, 92, 94, 96 Piping 93 Degassing piping 100 Control device 104 Memory , 110, 111 pressure sensor 120, 121, 122, 123 temperature sensor F1 first flow path F2 second flow path G1 suction port G2 discharge port G3 intermediate pressure port H1 first passage H2 second second aisle.

Claims (5)

An outdoor unit of a refrigeration cycle device configured to be connected to a load device including a first expansion device and an evaporator,
a first flow path forming a circulation flow path in which a coolant circulates by being connected to the load device;
a compressor and a condenser disposed in the first flow path;
a second flow path branched from a branch point of the first flow path downstream of the condenser in the direction in which the refrigerant circulates and configured to return the refrigerant that has passed through the condenser to the compressor; ,
a second expansion device, a receiver, and a flow control valve arranged in the second flow path in order from the branch point;
a heat exchanger having a first passage and a second passage and configured to exchange heat between the refrigerant flowing through the first passage and the refrigerant flowing through the second passage;
the first passage of the heat exchanger is disposed between the condenser and the branch point of the first flow path;
the second passage of the heat exchanger is arranged between the flow control valve of the second flow path and the compressor;
The flow rate adjustment valve is configured to adjust the discharge flow rate of the liquid refrigerant from the liquid receiver,
When starting the pump-down operation for collecting the refrigerant in the liquid receiver, the control state of the compressor and the flow control valve is such that the flow control valve is closed while the compressor is operated at a first time point. becomes the first state,
At a second time point after the first time point during the pump-down operation, the control state transitions from the first state to a second state in which the flow control valve is opened while operating the compressor. unit. 2. The apparatus according to claim 1, wherein when a difference between a condensation temperature of said refrigerant in said condenser and an outside air temperature becomes smaller than a threshold value, said compressor and said flow control valve are controlled in said second state. Outdoor unit as described. The outdoor unit according to claim 2, wherein the rotation speed of the compressor in the second state is higher than the rotation speed of the compressor in the first state. 2. The outdoor unit according to claim 1, wherein the amount of liquid refrigerant in said liquid receiver at said second time point is greater than the amount of liquid refrigerant in said liquid receiver at said first time point. A refrigeration cycle apparatus comprising the outdoor unit according to any one of claims 1 to 4 and the load device.

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