EP4749206A1

EP4749206A1 - Refrigeration device

Info

Publication number: EP4749206A1
Application number: EP25746539.3A
Authority: EP
Inventors: Kei Takenaka; Takashi Tsuchino; Kento OKUZAWA
Original assignee: Daikin Industries Ltd
Current assignee: Daikin Industries Ltd
Priority date: 2024-08-23
Filing date: 2025-05-23
Publication date: 2026-05-27
Also published as: WO2026042353A1; JP2026038370A; EP4749206A4

Abstract

Provided is a refrigeration apparatus capable of reliable refrigerant recovery after a heating operation is stopped. This refrigeration apparatus performs a heating operation. The refrigeration apparatus includes a refrigerant circuit, a heat source fan, and a control unit. The refrigerant circuit has a compressor and a heat source heat exchanger. The heat source fan supplies air to the heat source heat exchanger. The control unit controls the compressor and the heat source fan. The control unit, upon detecting an instruction to stop the heating operation, starts a first operation to recover a refrigerant into the compressor or the heat source heat exchanger by driving the heat source fan while keeping the compressor stopped. When a termination condition where the refrigerant is in a predetermined state in the refrigerant circuit is satisfied, the control unit stops the heat source fan and terminates the first operation.

Description

TECHNICAL FIELD

The present disclosure relates to a refrigeration apparatus.

BACKGROUND ART

Patent Literature 1 ( JP 2000-28210 A ) discloses an air conditioner that performs a refrigerant recovery operation to recover a refrigerant to an outdoor unit after an operation is stopped using a temperature difference between inside and outside of the room in order to reduce a risk in the event of refrigerant leakage.

SUMMARY OF THE INVENTION

In Patent Literature 1, termination conditions of the refrigerant recovery operation are not clear. For this reason, in the air conditioner according to Patent Literature 1, there is a possibility that, with the refrigerant remaining in an indoor unit and no refrigerant recovery, the refrigerant recovery operation is terminated, which may result in failure of reliable refrigerant recovery.
The purpose of the present disclosure is to provide a refrigeration apparatus capable of reliable refrigerant recovery after a heating operation is stopped.

A refrigeration apparatus according to a first aspect performs a heating operation. The refrigeration apparatus includes a refrigerant circuit, a heat source fan, and a control unit. The refrigerant circuit has a compressor and a heat source heat exchanger. The heat source fan supplies air to the heat source heat exchanger. The control unit controls the compressor and the heat source fan. The control unit, upon detecting an instruction to stop the heating operation, starts a first operation to recover a refrigerant into the compressor or the heat source heat exchanger by driving the heat source fan while keeping the compressor stopped. When a termination condition where the refrigerant is in a predetermined state in the refrigerant circuit is satisfied, the control unit stops the heat source fan and terminates the first operation.
By driving the heat source fan to supply air to the heat source heat exchanger, the refrigerant in the heat source heat exchanger is cooled and condensation is promoted. As a result, the refrigerant in the refrigerant circuit is recovered into the heat source heat exchanger from the relatively high-pressure utilization unit side. In addition, since the heat source fan is stopped and the first operation, which is the refrigerant recovery operation, is terminated after the termination condition where the refrigerant is in the predetermined state in the refrigerant circuit is satisfied, it is suppressed that the first operation is terminated before sufficient refrigerant recovery is completed. Therefore, this refrigeration apparatus is capable of reliable refrigerant recovery after the operation is stopped.
A refrigeration apparatus according to a second aspect is the refrigeration apparatus according to the first aspect, in which the termination condition is that a pressure of the refrigerant in the refrigerant circuit is equal to or lower than a predetermined first pressure, or a temperature of the refrigerant in the refrigerant circuit is equal to or lower than a predetermined first temperature.
This refrigeration apparatus determines a refrigerant recovery state on the basis of the pressure or temperature of the refrigerant in the refrigerant circuit, thereby allowing reliable refrigerant recovery after the operation is stopped.
A refrigeration apparatus according to a third aspect is the refrigeration apparatus according to the second aspect, in which the termination condition is that the pressure of the refrigerant in a gas pipe of the refrigerant circuit is equal to or lower than the first pressure, or the temperature of the refrigerant in the gas pipe of the refrigerant circuit is equal to or lower than the predetermined first temperature.
This refrigeration apparatus determines a refrigerant recovery state on the basis of the pressure or temperature of the refrigerant in the refrigerant circuit, thereby allowing reliable refrigerant recovery after the operation is stopped.
A refrigeration apparatus according to a fourth aspect is the refrigeration apparatus according to the second or third aspect, in which the first temperature is equal to or lower than an outside air temperature.
This refrigeration apparatus determines a refrigerant recovery state on the basis of the temperature of the refrigerant in the refrigerant circuit, thereby allowing reliable refrigerant recovery after the operation is stopped.
A refrigeration apparatus according to a fifth aspect is the refrigeration apparatus according to the second or third aspect, in which the first pressure is the pressure of the refrigerant when an outside air temperature is an evaporation temperature.
This refrigeration apparatus determines a refrigerant recovery state on the basis of the pressure of the refrigerant in the refrigerant circuit, thereby allowing reliable refrigerant recovery after the operation is stopped.
A refrigeration apparatus according to a sixth aspect is any one of the refrigeration apparatuses according to the first to fifth aspects, in which the control unit, in the first operation, rotates the heat source fan at a minimum rotational speed or more in the heating operation.
Since the heat source fan is rotated at the minimum rotational speed or more in the heating operation, the condensation of the refrigerant is promoted. Therefore, this refrigeration apparatus is capable of reliable refrigerant recovery after the operation is stopped.
A refrigeration apparatus according to a seventh aspect is any one of the refrigeration apparatuses according to the first to sixth aspects, in which the refrigerant circuit further includes an expansion mechanism. The control unit fully opens the expansion mechanism in the first operation.
Since the expansion mechanism is fully opened, the expansion mechanism is prevented from hindering the inflow of the refrigerant from the utilization unit to the heat source heat exchanger. Therefore, this refrigeration apparatus is capable of reliable refrigerant recovery after the operation is stopped.
A refrigeration apparatus according to an eighth aspect is any one of the refrigeration apparatuses according to the first to seventh aspects, in which upon detecting the termination condition in the first operation, the control unit stops the heat source fan after a lapse of a predetermined time.
Since the heat source fan continues to be driven even after the detection of the termination condition, this refrigeration apparatus is capable of reliable refrigerant recovery after the operation is stopped.
A refrigeration apparatus according to a ninth aspect is any one of the refrigeration apparatuses according to the first to eighth aspects, in which the refrigerant circuit further has an shut-off valve. In the first operation, the control unit closes the gas-side shut-off valve before stopping the heat source fan.
Thus, even if the temperature difference between the refrigerant in the utilization heat exchanger and the refrigerant in the heat source heat exchanger decreases after the first operation due to, for example, a decrease in the temperature in the space to be air-conditioned, this refrigeration apparatus can prevent the refrigerant recovered in the heat source heat exchanger from returning to the utilization unit side.
A refrigeration apparatus according to a tenth aspect is the refrigeration apparatus according to the ninth aspect, in which in the first operation, the control unit closes the gas-side shut-off valve after detecting the termination condition.
Thus, even if the temperature difference between the refrigerant in the utilization heat exchanger and the refrigerant in the heat source heat exchanger decreases after the first operation due to, for example, a decrease in the temperature in the space to be air-conditioned, the refrigerant recovered in the heat source heat exchanger is prevented from returning to the utilization unit side.
A refrigeration apparatus according to an eleventh aspect is any one of the refrigeration apparatuses according to the first to tenth aspects, in which the instruction to stop the heating operation is output in response to a room temperature approaching a set temperature during the heating operation.
A refrigeration apparatus according to a twelfth aspect is any one of the refrigeration apparatuses according to the first to eleventh aspects, in which the refrigerant includes a flammable refrigerant.
This suppresses leakage of the flammable refrigerant into the space to be air-conditioned after this refrigeration apparatus is stopped.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration diagram of a refrigeration apparatus 100 according to an embodiment of the present disclosure.
FIG. 2 is a block diagram of a control unit 60.
FIG. 3 is a flowchart illustrating a control flow of a refrigerant recovery operation executed by the control unit 60.
FIG. 4 is a time chart illustrating the operation of each unit in the refrigerant recovery operation.

DESCRIPTION OF EMBODIMENT

(1) Overall configuration

FIG. 1 is a schematic configuration diagram of a refrigeration apparatus 100 according to an embodiment of the present disclosure. The refrigeration apparatus 100 achieves air conditioning operation for a space to be air-conditioned (not illustrated), by executing a vapor compression refrigeration cycle operation in a refrigerant circuit 10. The air conditioning operation includes a cooling operation and a heating operation. Furthermore, although described in detail later, the refrigeration apparatus 100 executes a refrigerant recovery operation. The refrigeration apparatus 100 mainly includes one heat source unit 20, one utilization unit 50, a liquid refrigerant connection pipe 2, a gas refrigerant connection pipe 4, and a control unit 60.
The refrigerant circuit 10 is configured by connecting the respective devices of the heat source unit 20 and the utilization unit 50 to the liquid refrigerant connection pipe 2 and the gas refrigerant connection pipe 4 via refrigerant pipes. More specifically, the refrigerant circuit 10 has a compressor 21, a flow direction switching mechanism 22, a heat source heat exchanger 23, an expansion mechanism 24, an shut-off valve 29, a utilization heat exchanger 51, the liquid refrigerant connection pipe 2, and the gas refrigerant connection pipe 4, and is configured by connecting these via refrigerant pipes. A refrigerant is sealed in the refrigerant circuit 10. The refrigerant sealed in the refrigerant circuit 10 is a flammable refrigerant such as propane.

(2) Detailed Configuration

(2-1) Utilization Unit 50

The utilization unit 50 has the utilization heat exchanger 51 and a utilization fan 52. The utilization unit 50 is installed, for example, in a space to be air-conditioned.

(2-1-1) Utilization Heat Exchanger 51

The utilization heat exchanger 51 causes heat exchange between the refrigerant flowing inside and air in the space to be air-conditioned. The utilization heat exchanger 51 has a liquid-side end 51a and a gas-side end 51b.
The liquid-side end 51a is connected to the liquid refrigerant connection pipe 2 via a refrigerant pipe. The gas-side end 51b is connected to the gas refrigerant connection pipe 4 via a refrigerant pipe.

(2-1-2) Utilization Fan 52

The utilization fan 52 supplies air to the utilization heat exchanger 51. The utilization fan 52 is driven by a motor 52a. The rotational speed of the motor 52a is controlled by the control unit 60.

(2-2) Heat Source Unit 20

The heat source unit 20 has the compressor 21, the flow direction switching mechanism 22, the heat source heat exchanger 23, the expansion mechanism 24, an accumulator 25, a shutoff valve 26, a heat source fan 27, a pressure sensor 28, and the shut-off valve 29. The heat source unit 20 is disposed outside the space to be air-conditioned, for example.

(2-2-1) Compressor 21

The compressor 21 draws in a low-pressure refrigerant in a refrigeration cycle from the suction pipe 21a, compresses the refrigerant with a compression mechanism (not illustrated), and discharges the refrigerant as a high-pressure refrigerant in the refrigeration cycle to a discharge pipe 21b. The capacity of the compressor 21 is controlled by the control unit 60. The operating capacity of the compressor 21 is controlled by controlling the rotational speed of a motor (not illustrated) that drives the compression mechanism.

(2-2-2) Flow Direction Switching Mechanism 22

The flow direction switching mechanism 22 switches between a first state and a second state to switch the direction in which the refrigerant flows. The flow direction switching mechanism 22 is switched between the first state and the second state by the control unit 60. In the present embodiment, the flow direction switching mechanism 22 is a four-way switching valve.
In the first state, the flow direction switching mechanism 22 causes an inflow port 25a of the accumulator 25 to communicate with the gas refrigerant connection pipe 4, and causes the discharge pipe 21b of the compressor 21 to communicate with a gas-side end 23b of the heat source heat exchanger 23 (see a solid line in the flow direction switching mechanism 22 in FIG. 1). In the second state, the flow direction switching mechanism 22 causes the inflow port 25a of the accumulator 25 to communicate with the gas-side end 23b of the heat source heat exchanger 23, and causes the discharge pipe 21b to communicate with the gas refrigerant connection pipe 4 (see a broken line in the flow direction switching mechanism 22 in FIG. 1).

(2-2-3) Heat Source Heat Exchanger 23

The heat source heat exchanger 23 causes heat exchange between the refrigerant flowing inside and air (heat source air) at the location where the heat source unit 20 is installed. The heat source heat exchanger 23 has a liquid-side end 23a and the gas-side end 23b.
The liquid-side end 23a is connected to the liquid refrigerant connection pipe 2 via a refrigerant pipe. The gas-side end 23b is connected to the gas refrigerant connection pipe 4 via a refrigerant pipe.

(2-2-4) Expansion Mechanism 24

The expansion mechanism 24 adjusts the pressure and/or flow rate of the refrigerant flowing through the refrigerant circuit 10. The expansion mechanism 24 is provided in a refrigerant pipe that connects the liquid refrigerant connection pipe 2 to the liquid-side end 23a of the heat source heat exchanger 23. The expansion mechanism 24 is an electric expansion valve having a variable opening degree and capable of being fully closed. The opening degree of the expansion mechanism 24 is controlled by the control unit 60.

(2-2-5) Accumulator 25

The accumulator 25 separates the flowing refrigerant into a gas refrigerant and a liquid refrigerant. Furthermore, the accumulator 25 stores therein surplus refrigerant generated in response to, for example, fluctuations in the operation load of the utilization unit 50. The accumulator 25 has the inflow port 25a and an exhaust port 25b.
The inflow port 25a is connected to the flow direction switching mechanism 22. The exhaust port 25b is connected to the suction pipe 21a of the compressor 21.

(2-2-6) Shutoff Valve 26

The shutoff valve 26, when in a closed state, blocks the flow of the refrigerant flowing through the refrigerant pipe. The shutoff valve 26 includes a liquid-side shutoff valve 26a and a gas-side shutoff valve 26b. The shutoff valve 26 is, for example, a manually operated valve.
The liquid-side shutoff valve 26a is provided between the expansion mechanism 24 and the liquid refrigerant connection pipe 2 in the refrigerant pipe that connects the liquid-side end 23a of the heat source heat exchanger 23 to the liquid refrigerant connection pipe 2.
The gas-side shutoff valve 26b is provided in the refrigerant pipe that connects the flow direction switching mechanism 22 to the gas refrigerant connection pipe 4.

(2-2-7) Heat Source Fan 27

The heat source fan 27 supplies air to the heat source heat exchanger 23. The heat source fan 27 is driven by a motor 27a. The rotational speed of the motor 27a is controlled by the control unit 60.

(2-2-8) Pressure Sensor 28

The pressure sensor 28 detects a pressure P of the refrigerant in the refrigerant circuit 10. The pressure sensor 28 is provided in the refrigerant pipe that connects the gas-side shutoff valve 26b to the gas refrigerant connection pipe 4. As a result, the pressure sensor 28 detects the pressure of the refrigerant in a gas pipe 10a (refrigerant pipe that connects the flow direction switching mechanism 22 to the gas refrigerant connection pipe 4) of the refrigerant circuit 10.
The control unit 60 receives the pressure detected by the pressure sensor 28.

(2-2-9) Isolation Valve 29

The shut-off valve 29, when in a closed state, blocks the flow of the refrigerant flowing through the refrigerant pipe. The shut-off valve 29 is provided between the gas-side shutoff valve 26b and the pressure sensor 28 in the refrigerant pipe that connects the gas-side shutoff valve 26b to the gas refrigerant connection pipe 4.
The opening and closing of the shut-off valve 29 is controlled by the control unit 60. Specifically, the shut-off valve 29 is controlled to open during the cooling operation and the heating operation, and is controlled to close partway through the refrigerant recovery operation, which will be described later, and when the refrigeration apparatus 100 is out of operation.

(2-3) Liquid Refrigerant Connection Pipe 2 and Gas Refrigerant Connection Pipe 4

The liquid refrigerant connection pipe 2 and the gas refrigerant connection pipe 4 connect the heat source unit 20 to the utilization unit 50.

(2-4) Control Unit

The control unit 60 controls the operation of the respective devices of the heat source unit 20 and the utilization unit 50 to achieve the refrigeration cycle operation and the refrigerant recovery operation. FIG. 2 is a block diagram of the control unit 60. As illustrated in FIG. 2, the control unit 60 is electrically connected to the compressor 21, the flow direction switching mechanism 22, the expansion mechanism 24, the motor 27a of the heat source fan 27, the shut-off valve 29, and the motor 52a of the utilization fan 52 so as to enable transmission and reception of control signals, and controls the operation of these components. The control unit 60 is also electrically connected to the pressure sensor 28 so as to enable reception of the pressure P. The user of the refrigeration apparatus 100 instructs the control unit 60 via a remote controller (not illustrated) to cause the refrigeration apparatus 100 to start or terminate the refrigeration cycle operation. The control unit 60 may be accommodated in either the utilization unit 50 or the heat source unit 20, may be accommodated in both the utilization unit 50 and the heat source unit 20, or may be installed separately from the utilization unit 50 and the heat source unit 20.
The control unit 60 is implemented by a computer. The control unit 60 includes a control calculation device and a storage device (both are not illustrated). Examples of the control calculation device can include a processor such as a CPU or a GPU. The control calculation device reads a program stored in the storage device and performs predetermined calculation processing in accordance with the program. Further, the control calculation device can write the calculation results in the storage device and read information stored in the storage device, in accordance with the program. The control unit 60 may be implemented by a plurality of computers.

(2-5) Operation of Refrigeration Apparatus

The control of the operation of the refrigeration apparatus 100 in the cooling operation, the heating operation, and the refrigerant recovery operation will be described.

(2-5-1) Cooling Operation

Upon detecting an instruction to start the cooling operation sent from the remote controller or the like, the control unit 60 brings the flow direction switching mechanism 22 into the first state and starts the operation of the compressor 21, the heat source fan 27, and the utilization fan 52.
The control unit 60 controls the rotational speed of the motor 27a of the heat source fan 27 and the rotational speed of the motor 52a of the utilization fan 52 to predetermined rotational speeds. For example, the control unit 60 controls the rotational speed of the motor 27a to the maximum rotational speed. The control unit 60 controls the rotational speed of the motor 52a as appropriate on the basis of an airflow instruction or the like input to the remote controller.
The control unit 60 controls the opening degree of the expansion mechanism 24 so that the degree of superheating of the refrigerant approaches a predetermined target degree of superheating. The control unit 60 controls the operating capacity of the compressor 21 so that the evaporation temperature approaches a predetermined target evaporation temperature. The control unit 60 fully opens the shut-off valve 29.
When the operation of the compressor 21 is started, the low-pressure gas refrigerant in the refrigeration cycle is drawn into the compressor 21 from the suction pipe 21a and compressed to become the high-pressure gas refrigerant in the refrigeration cycle. When discharged from the discharge pipe 21b, the high-pressure gas refrigerant is sent to the heat source heat exchanger 23 via the flow direction switching mechanism 22. The refrigerant flowing into the heat source heat exchanger 23 exchanges heat with the heat source air supplied by the heat source fan 27, and condenses into a high-pressure liquid refrigerant. The high-pressure liquid refrigerant leaving the heat source heat exchanger 23 is decompressed by the expansion mechanism 24 to become a refrigerant in a gas-liquid two-phase state, and is sent to the liquid refrigerant connection pipe 2. The refrigerant in the gas-liquid two-phase state that has passed through the liquid refrigerant connection pipe 2 and flowed into the utilization unit 50 is sent to the utilization heat exchanger 51. The refrigerant having flowed into the utilization heat exchanger 51 exchanges heat with air in the space to be air-conditioned, supplied to the utilization heat exchanger 51 by the utilization fan 52, and evaporates into a low-pressure gas refrigerant. The air supplied to the utilization heat exchanger 51 is cooled by heat exchange with the refrigerant flowing through the utilization heat exchanger 51, and then is blown out into the space to be air-conditioned. The low-pressure gas refrigerant leaving the utilization heat exchanger 51 is sent to the gas refrigerant connection pipe 4. The refrigerant having passed through the gas refrigerant connection pipe 4 and flowed into the heat source unit 20 flows into the accumulator 25 through the inflow port 25a via the flow direction switching mechanism 22. The low-pressure gas refrigerant flowing into the accumulator 25 leaves the accumulator 25 through the exhaust port 25b, and is then drawn into the compressor 21 again.

(2-5-2) Heating Operation

Upon detecting an instruction to start the heating operation sent from the remote controller or the like, the control unit 60 brings the flow direction switching mechanism 22 into the second state and starts the operation of the compressor 21, the heat source fan 27, and the utilization fan 52.
The control unit 60 controls the rotational speed of the motor 27a of the heat source fan 27 and the rotational speed of the motor 52a of the utilization fan 52 to predetermined rotational speeds. For example, the control unit 60 controls the rotational speed of the motor 27a to the maximum rotational speed. The control unit 60 controls the rotational speed of the motor 52a as appropriate on the basis of an airflow instruction or the like input to the remote controller.
The control unit 60 controls the opening degree of the expansion mechanism 24 so that the degree of subcooling of the refrigerant approaches a predetermined target degree of subcooling. The control unit 60 controls the operating capacity of the compressor 21 so that the condensation temperature approaches a predetermined target condensation temperature. The control unit 60 fully opens the shut-off valve 29.
When the operation of the compressor 21 is started, the low-pressure gas refrigerant in the refrigeration cycle is drawn into the compressor 21 from the suction pipe 21a and compressed to become the high-pressure gas refrigerant in the refrigeration cycle. When discharged from discharge pipe 21b, the high-pressure gas refrigerant is sent to utilization heat exchanger 51 via the flow direction switching mechanism 22. The refrigerant that has flowed into the utilization heat exchanger 51 exchanges heat with air in the space to be air-conditioned, supplied by the utilization fan 52, and condenses into a high-pressure liquid refrigerant. The air supplied to the utilization heat exchanger 51 is heated by heat exchange with the refrigerant flowing through the utilization heat exchanger 51, and then is blown out into the space to be air-conditioned. The high-pressure liquid refrigerant leaving the utilization heat exchanger 51 is sent to the liquid refrigerant connection pipe 2. The refrigerant that has passed through the liquid refrigerant connection pipe 2 and flowed into the heat source unit 20 is decompressed by the expansion mechanism 24 to become a refrigerant in a gas-liquid two-phase state, and is sent to the heat source heat exchanger 23. The refrigerant that has flowed into the heat source heat exchanger 23 exchanges heat with the heat source air supplied to the heat source heat exchanger 23 by the heat source fan 27, and evaporates into a low-pressure gas refrigerant. The low-pressure gas refrigerant leaving the heat source heat exchanger 23 flows into the accumulator 25 through the inflow port 25a via the flow direction switching mechanism 22. The low-pressure gas refrigerant flowing into the accumulator 25 leaves the accumulator 25 through the exhaust port 25b, and is then drawn into the compressor 21 again.

(2-5-3) Refrigerant Recovery Operation

(2-5-3-1) Outline

The refrigerant recovery operation is intended to recover the refrigerant into the refrigerant circuit 10 on the heat source unit 20 side after an instruction to stop the heating operation is detected. Specifically, upon detecting an instruction to stop the heating operation during the refrigerant recovery operation, the control unit 60 drives the heat source fan 27 while keeping the compressor 21 stopped. Thus, the refrigerant is recovered into the compressor 21 or the heat source heat exchanger 23. When a termination condition where the refrigerant is in a predetermined state in the refrigerant circuit 10 is satisfied, the control unit 60 stops the heat source fan 27 to terminate the refrigerant recovery operation. The refrigerant recovery operation is an example of the first operation.

(2-5-3-2) Control Flow

FIG. 3 is a flowchart illustrating a control flow of a refrigerant recovery operation executed by the control unit 60. FIG. 4 is a time chart illustrating the operation of each unit in the refrigerant recovery operation. The control unit 60 starts (initiates) the refrigerant recovery operation simultaneously with the start of the heating operation.
In step S100, the control unit 60 determines whether or not an instruction to stop the heating operation sent from the remote controller or the like is detected, and advances the processing to step S100 or step S110. Specifically, the control unit 60 advances the processing to step S110 upon detecting an instruction to stop the heating operation (Yes), and advances the processing to step S100 if there is no instruction to stop the heating operation (No). In other words, the control unit 60 repeats the processing in step S100 until an instruction to stop the heating operation is detected.
In step S110, the control unit 60 stops the operation of the compressor 21, fully opens the expansion mechanism 24, sets the rotational speed of the motor 27a of the heat source fan 27 to a predetermined first rotational speed r1, stops the motor 52a of the utilization fan 52, and advances the processing to step S120 (T1 in FIG. 4). The first rotational speed r1 may be equal to or higher than the minimum rotational speed of the motor 27a in the heating operation.
By driving the motor 27a of the heat source fan 27 to supply air to the heat source heat exchanger 23, the refrigerant in the heat source heat exchanger 23 is cooled and condensation is promoted. As a result, the refrigerant in the refrigerant circuit 10 is recovered from the utilization unit 50 side, which is at high pressure, into the heat source heat exchanger 23, which is at low pressure. As the recovery of the refrigerant progresses, as illustrated in FIG. 4, the pressure P (in other words, the pressure of the refrigerant in the refrigerant circuit 10) detected by the pressure sensor 28 decreases with time.
In step S120, the control unit 60 determines whether or not the pressure P detected by the pressure sensor 28 is equal to or lower than a predetermined first pressure P1, and advances the processing to step S120 or step S30. Specifically, the control unit 60 advances the processing to step S120 if the pressure P is equal to or lower than the first pressure P1 (Yes), and advances the processing to step S130 if the pressure P is not equal to or lower than the first pressure P1 (No). In other words, the control unit 60 repeats the processing in step S120 until the pressure P becomes equal to or lower than the first pressure P1.
The first pressure P1 is used to determine that a sufficient amount of refrigerant has been recovered on the heat source unit 20 side. The first pressure P1 is, for example, the pressure of the refrigerant when the outside air temperature is the evaporation temperature. The pressure P being equal to or lower than the first pressure P1 is an example of the termination condition where the refrigerant is in a predetermined state.
In step S130, the control unit 60 fully closes the expansion mechanism 24, fully closes the shut-off valve 29, and advances the processing to step S140 (T2 in FIG. 4).
By fully closing the expansion mechanism 24 and the shut-off valve 29, the refrigerant recovered in the heat source heat exchanger 23 is prevented from returning to the utilization unit 50 side.
In step S140, the control unit 60 determines whether or not a predetermined first time t1 has elapsed since the end of step S130, and advances the processing to step S140 or step S150. Specifically, the control unit 60 advances the processing to step S140 upon determining that the first time t1 has elapsed (Yes), and advances the processing to step S150 if the first time t1 has not elapsed (No). In other words, the control unit 60 repeats the processing in step S140 until the first time t1 elapses. The first time t1 is, for example, about 20 to 30 seconds.
In step S150, the control unit 60 stops the motor 27a of the heat source fan 27, and terminates the refrigerant recovery operation (T3 in FIG. 4).
By stopping the motor 27a of the heat source fan 27 after second time t2 has elapsed since the expansion mechanism 24 and the shut-off valve 29 are fully closed, the refrigerant can be more reliably recovered on the heat source unit 20 side.

(3) Modifications

(3-1) Modification A

In step S120, instead of determining whether or not the pressure P is equal to or lower than the first pressure P1, the control unit 60 may determine whether or not the temperature of the refrigerant in the refrigerant circuit 10 is equal to or lower than a predetermined first temperature. In other words, the termination condition where the refrigerant is in the predetermined state may be that the temperature of the refrigerant in the refrigerant circuit 10 is equal to or lower than the predetermined first temperature. The first temperature may be an outside air temperature (for example, a temperature at which a predetermined margin is allowed for the outside air temperature).
In this case, the temperature of the refrigerant in the refrigerant circuit 10 may be detected by a temperature sensor (not illustrated) provided in the refrigerant circuit 10.

(3-2) Modification B

The pressure sensor 28 may be provided in locations other than the gas pipe 10a as long as it can detect the pressure of the refrigerant in the refrigerant circuit 10.

(3-3) Modification C

The instruction to stop the heating operation may be an instruction for operation (referred to as thermo-off or the like) to stop the heating operation, output in response to the room temperature approaching a set temperature during the heating operation.

(4) Features

(4-1)
The refrigeration apparatus 100 performs a heating operation. The refrigeration apparatus 100 includes the refrigerant circuit 10, the heat source fan 27, and the control unit. The refrigerant circuit 10 has the compressor 21 and the heat source heat exchanger 23. The heat source fan 27 supplies air to the heat source heat exchanger 23. The control unit 60 controls the compressor 21 and the heat source fan 27. Upon detecting an instruction to stop the heating operation, the control unit 60 starts the refrigerant recovery operation to recover the refrigerant into the compressor 21 or the heat source heat exchanger 23 by driving the heat source fan 27 while keeping the compressor 21 stopped. When a termination condition where the refrigerant is in a predetermined state in the refrigerant circuit 10 is satisfied, the control unit 60 stops the heat source fan 27 to terminate the refrigerant recovery operation.
By driving the heat source fan 27 to supply air to the heat source heat exchanger 23, the refrigerant in the heat source heat exchanger 23 is cooled and condensation is promoted. As a result, the refrigerant in the refrigerant circuit 10 is recovered into the heat source heat exchanger 23 from the utilization unit 50 side, which is at relatively high pressure. In addition, since the heat source fan 27 is stopped and the refrigerant recovery operation is terminated after the termination condition where the refrigerant is in the predetermined state in the refrigerant circuit 10 is satisfied, it is suppressed that the refrigerant recovery operation is terminated before sufficient refrigerant recovery is completed. Therefore, the refrigeration apparatus 100 is capable of reliable refrigerant recovery after the operation is stopped.
(4-2)
The termination condition is that the pressure of the refrigerant in the refrigerant circuit 10 is equal to or lower than a predetermined first pressure or the temperature of the refrigerant in the refrigerant circuit 10 is equal to or lower than a predetermined first temperature.
The refrigeration apparatus 100 determines a refrigerant recovery state on the basis of the pressure or temperature of the refrigerant in the refrigerant circuit 10, thereby allowing reliable refrigerant recovery after the operation is stopped.
(4-3)
The termination condition is that the pressure of the refrigerant in the gas pipe 10a of the refrigerant circuit 10 is equal to or lower than the first pressure, or the temperature of the refrigerant in the gas pipe 10a of the refrigerant circuit 10 is equal to or lower than the predetermined first temperature.
The refrigeration apparatus 100 determines a refrigerant recovery state on the basis of the pressure or temperature of the refrigerant in the refrigerant circuit 10, thereby allowing reliable refrigerant recovery after the operation is stopped.
(4-4)
The first temperature is equal to or lower than an outside air temperature.
The refrigeration apparatus 100 determines a refrigerant recovery state on the basis of the temperature of the refrigerant in the refrigerant circuit 10, thereby allowing reliable refrigerant recovery after the operation is stopped.
(4-5)
The first pressure is the pressure of the refrigerant when an outside air temperature is an evaporation temperature.
The refrigeration apparatus 100 determines a refrigerant recovery state on the basis of the pressure of the refrigerant in the refrigerant circuit 10, thereby allowing reliable refrigerant recovery after the operation is stopped.
(4-6)
In the refrigerant recovery operation, the control unit 60 rotates the heat source fan 27 at a minimum rotational speed or more in the heating operation.
Since the heat source fan 27 is rotated at the minimum rotational speed or more in the heating operation, the condensation of the refrigerant is promoted. Therefore, the refrigeration apparatus 100 is capable of reliable refrigerant recovery after the operation is stopped.
(4-7)
The refrigerant circuit 10 further includes the expansion mechanism. The control unit 60 fully opens the expansion mechanism 24 in the refrigerant recovery operation.
Since the expansion mechanism 24 is fully opened, the expansion mechanism 24 is prevented from hindering the inflow of the refrigerant from the utilization unit 50 to the heat source heat exchanger 23. Therefore, the refrigeration apparatus 100 is capable of reliable refrigerant recovery after the operation is stopped.
(4-8)
Upon detecting the termination condition in the refrigerant recovery operation, the control unit 60 stops the heat source fan 27 after a lapse of a predetermined time.
Since the heat source fan 27 continues to be driven even after the detection of the termination condition, the refrigeration apparatus 100 is capable of reliable refrigerant recovery after the operation is stopped.
(4-9)
The refrigerant circuit 10 further has the shut-off valve. In the refrigerant recovery operation, the control unit 60 closes the gas-side shut-off valve before stopping the heat source fan 27.
Thus, even if the temperature difference between the refrigerant in the utilization heat exchanger 51 and the refrigerant in the heat source heat exchanger 23 decreases after the refrigerant recovery operation due to, for example, a decrease in the temperature in the space to be air-conditioned, the refrigeration apparatus 100 can prevent the refrigerant recovered in the heat source heat exchanger 23 from returning to the utilization unit 50 side.
(4-10)
In the refrigerant recovery operation, the control unit 60 closes the shut-off valve 29 after detecting the termination condition.
Thus, even if the temperature difference between the refrigerant in the utilization heat exchanger 51 and the refrigerant in the heat source heat exchanger 23 decreases after the refrigerant recovery operation due to, for example, a decrease in the temperature in the space to be air-conditioned, the refrigerant recovered in the heat source heat exchanger 23 is prevented from returning to the utilization unit 50 side.
(4-11)
The instruction to stop the heating operation is output in response to a room temperature approaching a set temperature during the heating operation.
(4-12)
The refrigerant includes a flammable refrigerant.
This suppresses leakage of the flammable refrigerant into the space to be air-conditioned after the refrigeration apparatus 100 is stopped.

While the embodiment according to the present disclosure has been described above, it will be understood that various changes in forms and details can be made without departing from the gist and scope of the present disclosure recited in the claims.

REFERENCE SIGNS LIST

10: refrigerant circuit
10a: gas pipe
21: compressor
23: heat source heat exchanger
24: expansion mechanism
27: heat source fan
29: shut-off valve
60: control unit
100: refrigeration apparatus
P: pressure
P1: first pressure

CITATION LIST

PATENT LITERATURE

Patent Literature 1: JP 2000-28210 A

Claims

A refrigeration apparatus (100) that performs a heating operation, the refrigeration apparatus (100) comprising:
a refrigerant circuit (10) having a compressor (21) and a heat source heat exchanger (23);

a heat source fan (27) that supplies air to the heat source heat exchanger (23); and

a control unit (60) that controls the compressor (21) and the heat source fan (27), wherein

the control unit (60),

upon detecting an instruction to stop the heating operation, starts a first operation to recover a refrigerant into the compressor (21) or the heat source heat exchanger (23) by driving the heat source fan (27) while keeping the compressor (21) stopped, and

when a termination condition where the refrigerant is in a predetermined state in the refrigerant circuit (10) is satisfied, the heat source fan (27) is stopped to terminate the first operation.
The refrigeration apparatus (100) according to claim 1, wherein
the termination condition is that

a pressure (P) of the refrigerant in the refrigerant circuit (10) is equal to or lower than a predetermined first pressure (P1), or a temperature of the refrigerant in the refrigerant circuit (10) is equal to or lower than a predetermined first temperature.
The refrigeration apparatus (100) according to claim 2, wherein
the termination condition is that

the pressure (P) of the refrigerant in a gas pipe (10a) of the refrigerant circuit (10) is equal to or lower than the first pressure (P1), or the temperature of the refrigerant in the gas pipe (10a) of the refrigerant circuit (10) is equal to or lower than the predetermined first temperature.
The refrigeration apparatus (100) according to claim 2 or 3, wherein
the first temperature is

equal to or lower than an outside air temperature.
The refrigeration apparatus (100) according to claim 2 or 3, wherein
the first pressure (P1) is

the pressure (P) of the refrigerant when an outside air temperature is an evaporation temperature.
The refrigeration apparatus (100) according to any one of claims 1 to 5, wherein
the control unit (60),

in the first operation, rotates the heat source fan (27) at a minimum rotational speed or more in the heating operation.
The refrigeration apparatus (100) according to any one of claims 1 to 6, wherein
the refrigerant circuit (10) further includes

an expansion mechanism (24), and

the control unit (60)

fully opens the expansion mechanism (24) in the first operation.
The refrigeration apparatus (100) according to any one of claims 1 to 7, wherein
the control unit (60),

upon detecting the termination condition in the first operation, stops the heat source fan (27) after a lapse of a predetermined time.
The refrigeration apparatus (100) according to any one of claims 1 to 8, wherein
the refrigerant circuit (10) further has

an shut-off valve (29),

the control unit (60),

in the first operation, closes the shut-off valve (29) before stopping the heat source fan (27).
The refrigeration apparatus (100) according to claim 9, wherein
the control unit (60),

in the first operation, closes the shut-off valve (29) after detecting the termination condition.
The refrigeration apparatus (100) according to any one of claims 1 to 10, wherein
the instruction to stop the heating operation

is output in response to a room temperature approaching a set temperature during the heating operation.
The refrigeration apparatus (100) according to any one of claims 1 to 11, wherein
the refrigerant comprises

a flammable refrigerant.