Refrigeration cycle device, control method, and program

Abstract

In an operation to recover refrigerant from a leaking user-side circuit to a heat source-side circuit, the amount of refrigerant remaining on the user-side circuit is minimized. [Solution] The refrigeration cycle device includes a refrigerant circuit (10) including a heat source side circuit (20a) to which shut-off mechanisms (26, 28) are connected, and a utilization side circuit (40a) to which a utilization side heat exchanger (42) is connected; a refrigerant leak sensor (70) for detecting refrigerant leakage in the utilization side circuit (40a); and a control unit (100) that, when the refrigerant leak sensor (70) detects refrigerant leakage, performs a first operation to recover the refrigerant from the utilization side circuit (40a) to the heat source side circuit (20a). The first operation includes a first operation to reduce the opening of the shut-off mechanisms (26, 28) to a predetermined degree; a second operation to stop the compressor (22) if a first condition is met after the first operation; and a third operation to fully close the shut-off mechanisms (26, 28) if a first condition is met after the first operation.

Description

Technical Field

[0001] The present disclosure relates to a refrigeration cycle device, a control method, and a program.

Background Art

[0002] Patent Document 1 discloses a refrigeration system that, when refrigerant leakage is detected from a certain utilization unit among a plurality of utilization units, stops the use of the utilization unit and performs refrigerant recovery control to recover the refrigerant from the utilization unit targeted for stoppage to a heat source unit. In the refrigerant recovery control, the compressor is temporarily operated with the heat source side expansion valve closed, so that the refrigerant present in the utilization unit targeted for stoppage is recovered to the heat source unit.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the refrigerant recovery control described in Patent Document 1, there is a possibility that refrigerant remains in the communication piping or the like connected to the utilization unit, and the refrigerant recovery is not sufficient.

[0005] An object of the present disclosure is to suppress the amount of refrigerant remaining on the utilization unit side during the operation of recovering the refrigerant from the utilization unit where the refrigerant has leaked.

Means for Solving the Problems

[0006] The first aspect is a refrigerant circuit ( A utilization unit (40) having the aforementioned utilization-side heat exchanger (42) and air conditioning the target space (S), A refrigerant leak sensor (70) for detecting refrigerant leaks in the user-side circuit (40a), The system includes a control unit (100) that, when the refrigerant leak sensor (70) detects a refrigerant leak, performs a first operation to recover the refrigerant from the utilization circuit (40a) to the heat source circuit (20a), The above first operation is, A first operation to reduce the opening of the aforementioned shut-off mechanism (26, 28) to a predetermined opening, If the first condition is met after the first operation, a second operation is performed to stop the compressor (22), If the first condition is met after the first operation, a third operation is performed to completely close the shut-off mechanism (26, 28). It is a refrigeration cycle device.

[0007] In the first operation, if the shut-off mechanisms (26, 28) are fully closed, the refrigerant in the user-side circuit (40a) is recovered to the heat source-side circuit (20a), but some of the refrigerant may remain in the connecting pipe, which is the refrigerant piping connecting the user unit (40) and the heat source unit. In the first embodiment, by reducing the opening of the first shut-off valve (28) to a predetermined degree during the first operation, the refrigerant in the connecting pipe can be sent to the heat source-side circuit (20a). As a result, the refrigerant can be recovered to the heat source-side circuit (20a) without any remaining in the connecting pipe. In addition, the second and third operations suppress the flow of refrigerant from the heat source-side circuit (20a) to the connecting pipe and evaporator.

[0008] A second aspect is, in the first aspect, The user-side circuit (40a) has a second shut-off valve (43) whose valve opening degree can be adjusted. In the first operation described above, after stopping the compressor (22), the shut-off mechanisms (26, 28) and the second shut-off valve (43) are completely closed.

[0009] According to the second embodiment, after the compressor (22) is stopped by the second operation, leakage (flow) of refrigerant into the user-side circuit (40a) can be suppressed.

[0010] A third aspect is, in the first aspect, The user-side circuit (40a) has a second shut-off valve (43) whose valve opening degree can be adjusted. The first operation includes a fourth operation in which, if the first condition is met after the first operation, the second shut-off valve (43) is fully closed.

[0011] According to the third embodiment, after the compressor (22) is stopped by the second operation, it is possible to suppress the leakage (flow) of refrigerant into the user-side circuit (40a).

[0012] The fourth aspect is one of the first to third aspects, The first condition is met when the high pressure reaches a predetermined value, when a predetermined time has elapsed, or when the low pressure reaches a predetermined value.

[0013] According to the fourth embodiment, the rise in high voltage during the first operation can be suppressed.

[0014] The fifth aspect is one of the first to fourth aspects, The shut-off mechanism (26, 28) includes a first shut-off valve (28) with adjustable valve opening, The predetermined opening degree of the first shut-off valve (28) in the first operation is such that the refrigerant on the outlet side of the first shut-off valve (28) becomes saturated.

[0015] In the fifth embodiment, the rise in high pressure during the first operation can be suppressed. This makes it possible to avoid abnormal high pressure in the refrigerant circuit (10).

[0016] The sixth aspect is as described in the fifth aspect. A supercooled heat exchanger (29) connected to the heat source side circuit (20a), The aforementioned shut-off mechanism (26, 28) further comprises a heat source side shut-off valve (26), The supercooled heat exchanger (29) has a first flow path (29a) and a second flow path (29b) through which a refrigerant that cools the refrigerant in the first flow path (29a) flows. The heat source side shut-off valve (26) is provided on the downstream side of the refrigerant flow when the heat source side heat exchanger (23) functions as a radiator rather than the first flow path (29a). The first shut-off valve (28) is an expansion valve and is provided on the downstream side of the heat source side shut-off valve (26).

[0017] In the sixth aspect, even in a refrigeration device having a subcooling heat exchanger (29), the same effects as those of the first and second aspects can be obtained. Also, when performing the third operation, it is only necessary to fully close either the first shut-off valve (28) or the heat source side shut-off valve (26).

[0018] The seventh aspect is a control method for a refrigeration cycle device including a refrigerant circuit (10) including a heat source side circuit (20a) to which a compressor (22), a heat source side heat exchanger (23), and a shut-off mechanism (26, 28) are connected, and a utilization side circuit (40a) to which a utilization side heat exchanger (42) is connected, a utilization unit (40) having the utilization side heat exchanger (42) and air-conditioning a target space (S), a refrigerant leak sensor (70) for detecting a leak of the refrigerant in the utilization side circuit (40a), and a control unit (100), the control method comprising: the control unit when a refrigerant leak is detected by the refrigerant leak sensor (70), executing a first operation to recover the refrigerant in the utilization side circuit (40a) to the heat source side circuit (20a), the first operation includes a first operation of reducing the shut-off mechanism (26, 28) to a predetermined opening degree, a second operation of stopping the compressor (22) when a first condition is satisfied after the first operation, and a third operation of fully closing the shut-off mechanism (26, 28) when the first condition is satisfied after the first operation. In the seventh aspect, the same effect as that of the first aspect can be obtained. [[ID=3i]]

[0019] [[ID=3i]] In the seventh aspect, the same effect as that of the first aspect can be obtained.

[0020] The eighth aspect is a program that causes the control method described in the seventh aspect to be executed.

[0021] In the eighth embodiment, the same effect as in the first embodiment can be obtained. [Brief explanation of the drawing]

[0022] [Figure 1] Figure 1 is a schematic piping diagram of a refrigeration cycle system. [Figure 2] Figure 2 is a block diagram showing the main components of a refrigerant cycle system. [Figure 3] Figure 3 is a flowchart showing a series of operations of the control unit. [Figure 4] Figure 4 is a flowchart showing a series of operations of the control unit according to Modification 1. [Figure 5] Figure 5 is a flowchart showing a series of operations of the control unit according to the modified example 2. [Modes for carrying out the invention]

[0023] The embodiments of this disclosure will be described in detail below with reference to the drawings. However, this disclosure is not limited to the embodiments shown below, and various modifications are possible without departing from the technical idea of ​​this disclosure. Since the drawings are for conceptual explanation of this disclosure, dimensions, ratios, or numbers may be exaggerated or simplified as necessary for ease of understanding.

[0024] (1) Overall configuration of the refrigeration cycle system The refrigeration cycle device (1) of this embodiment cools the air in the target space, which is the interior space (S). The interior space (S) of the refrigeration cycle device (1) is formed inside, for example, a refrigerated or frozen display case or a warehouse.

[0025] The refrigeration cycle device (1) shown in Figure 1 has an outdoor unit (20), a cooling unit (40), and two connecting pipes (5, 6) that connect them. The refrigeration cycle device (1) of this embodiment is a pair type having one outdoor unit (20) and one cooling unit (40). The outdoor unit (20) constitutes a heat source unit installed outdoors. The cooling unit (40) constitutes a utilization unit that air-conditions the target space. More precisely, the cooling unit (40) cools the air in the storage space (S), which is the target space. The two connecting pipes (5, 6) consist of a liquid-side connecting pipe (5) and a gas-side connecting pipe (6). The outdoor unit (20) has a heat source side circuit (20a). The cooling unit (40) has a utilization side circuit (40a). In the refrigeration cycle device (1), the heat source side circuit (20a) and the utilization side circuit (40a) are connected via the liquid side connecting pipe (5) and the gas side connecting pipe (6) to form the refrigerant circuit (10). The refrigerant circuit (10) performs the refrigeration cycle by circulating the refrigerant that is being filled. In the following, the terms "upstream" and "downstream" may be used to refer to the direction of refrigerant flow in the refrigerant circuit (10) during normal operation, as described later.

[0026] The refrigerant circuit (10) is filled with R32, a mildly flammable refrigerant. However, the refrigerant filled in the refrigerant circuit (10) is not limited to this; for example, it may be R1234yf or R454C, both mildly flammable refrigerants. Alternatively, the refrigerant filled in the refrigerant circuit (10) may be propane (R290), a highly flammable natural refrigerant, or carbon dioxide (CO2), a natural refrigerant.

[0027] (2) Outdoor unit The outdoor unit (20) has an outdoor fan (21) and a heat source side circuit (20a). Heat source side equipment, including a compressor (22), an outdoor heat exchanger (23), a four-way switching valve (24), a receiver (25), a subcooling heat exchanger (29), a heat source side shut-off valve (26), and an outdoor expansion valve (28), is connected to the heat source side circuit (20a).

[0028] The compressor (22) compresses the low-pressure refrigerant and discharges the compressed refrigerant as high-pressure refrigerant. A discharge pipe (31) is connected to the discharge side of the compressor (22), and a suction pipe (32) is connected to the suction side of the compressor (22). The compressor (22) can be composed of scroll type, swing type, turbo type, screw type, etc. The compressor (22) is a variable-speed displacement type.

[0029] The outdoor heat exchanger (23) exchanges heat between the refrigerant and the outdoor air. The outdoor heat exchanger (23) is constructed in a fin-and-tube configuration. The outdoor heat exchanger (23) is an example of a heat source-side heat exchanger. The outdoor fan (21) transports the air passing through the outdoor heat exchanger (23).

[0030] The four-way directional control valve (24) has a first port (P1), a second port (P2), a third port (P3), and a fourth port (P4). The first port (P1) is connected to the discharge pipe (31), and the second port (P2) is connected to the suction pipe (32). The third port (P3) is connected to the gas side end of the outdoor heat exchanger (23), and the fourth port (P4) is connected to the gas side connecting pipe (6). The four-way directional control valve (24) switches between a first state in which the first port (P1) and the third port (P3) are in communication and the second port (P2) and the fourth port (P4) are in communication, and a second state in which the first port (P1) and the fourth port (P4) are in communication and the second port (P2) and the third port (P3) are in communication. The four-way switching valve (24) is in the first state during normal cooling operation and in the second state during defrost operation.

[0031] The heat source circuit (20a) has a liquid pipe (33) between the liquid side end of the outdoor heat exchanger (23) and the liquid side connecting pipe (5). The receiver (25) is installed in the middle of the liquid pipe (33). The receiver (25) stores the liquid refrigerant of the refrigerant circuit (10).

[0032] The heat source circuit (20a) has an injection channel (27). The inlet end of the injection channel (27) is connected to the liquid pipe (33). Specifically, the inlet end of the injection channel (27) is connected to the downstream side of the receiver (25) in the liquid pipe (33). The outlet end of the injection channel (27) is connected to the compressor (22) so as to communicate with the space in the compressor (22) where the refrigerant in the process of being compressed is present. An expansion valve (30) is connected to the injection channel (27). The expansion valve (30) reduces the pressure of the high-pressure refrigerant flowing through the injection channel (27) to an intermediate pressure. The expansion valve (30) is composed of, for example, an electronic expansion valve.

[0033] The subcooled heat exchanger (29) has a first flow path (29a) and a second flow path (29b) through which a refrigerant that cools the refrigerant in the first flow path (29a) flows. The subcooled heat exchanger (29) is positioned between the receiver (25) and the liquid end of the heat source side circuit (20a). Specifically, the first flow path (29a) is connected downstream of the connection at the inlet end of the injection flow path (27) of the liquid pipe (33). The second flow path (29b) is connected downstream of the expansion valve (30) of the injection flow path (27).

[0034] A portion of the refrigerant flowing out of the receiver (25) through the liquid pipe (33) flows into the injection channel (27), is depressurized by the expansion valve (30), and then flows into the second channel (29b). The high-pressure refrigerant flowing through the first channel (29a) is cooled by heat exchange with the refrigerant flowing through the second channel (29b). The intermediate-pressure refrigerant in the second channel (29b) exchanges heat with the refrigerant in the first channel (29a) and is then introduced into the space where the refrigerant in the compressor (22) is being compressed.

[0035] The heat source side shut-off valve (26) is connected in the middle of the liquid pipe (33). The heat source side shut-off valve (26) is located downstream of the first flow path (29a). The heat source side shut-off valve (26) is located near the liquid end, which is the connection point between the liquid pipe (33) and the liquid side connecting pipe (5). In other words, the heat source side shut-off valve (26) is located between the first flow path (29a) and the liquid end of the heat source side circuit (20a). The heat source side shut-off valve (26) is composed of an electromagnetic shut-off valve. The heat source side shut-off valve (26) is an electromagnetic valve. The heat source side shut-off valve (26) may also be an electrically operated valve. The heat source side shut-off valve (26) shuts off the heat source side circuit (20a) when it is closed. The heat source side shut-off valve (26) is included in the shut-off mechanism (26, 28) of this disclosure.

[0036] The external expansion valve (28) reduces the pressure of the refrigerant. The valve opening of the external expansion valve (28) is adjustable. The external expansion valve (28) is composed of, for example, an electronic expansion valve. The external expansion valve (28) is connected in the middle of the liquid pipe (33). The external expansion valve (28) is located near the liquid end of the heat source side circuit (20a). The external expansion valve (28) is located between the heat source side shut-off valve (26) and the liquid end of the heat source side circuit (20a). The external expansion valve (28) is located near the heat source side shut-off valve (26). Specifically, the external expansion valve (28) is located downstream of the heat source side shut-off valve (26). The external expansion valve (28) is an example of the first shut-off valve (28) of this disclosure. The external expansion valve (28) is included in the shut-off mechanism (26,28) of this disclosure.

[0037] (3) Cooling unit The cooling unit (40) is an example of a user unit. The cooling unit (40) provides air conditioning to the interior space (S). In this case, the cooling unit (40) cools the interior space (S). The cooling unit (40) has an interior fan (41) and a user-side circuit (40a). The user-side circuit (40a) has user-side equipment including an interior heat exchanger (42) and an interior expansion valve (43).

[0038] The internal heat exchanger (42) exchanges heat between the refrigerant and the air inside the refrigerator. The internal heat exchanger (42) is constructed in a fin-and-tube configuration. The internal heat exchanger (42) is an example of a heat exchanger on the user side. The internal fan (41) transports the air inside the refrigerator that passes through the internal heat exchanger (42).

[0039] The internal expansion valve (43) reduces the pressure of the refrigerant. The valve opening of the internal expansion valve (43) is adjustable. The internal expansion valve (43) is composed of, for example, an electronic expansion valve. The internal expansion valve (43) is installed upstream of the internal heat exchanger (42). The internal expansion valve (43) is installed between the internal heat exchanger (42) and the connection between the liquid side connecting pipe (5) and the user side circuit (40a). The internal expansion valve (43) is an example of a second shut-off valve (43).

[0040] The utilization-side circuit (40a) of this embodiment includes a drain pan heater (44). The drain pan heater (44) is positioned in the utilization-side circuit (40a) between the liquid end of the utilization-side circuit (40a) and the internal expansion valve (43). The drain pan heater (44) melts ice and frost that has peeled off the surface of the internal heat exchanger (42) with the refrigerant flowing through it.

[0041] (4) sensor The refrigeration cycle device (1) has a plurality of sensors. The plurality of sensors in this embodiment include a high-pressure sensor (61) and a low-pressure sensor (62).

[0042] The high-pressure sensor (61) is installed in the discharge pipe (31). The high-pressure sensor (61) detects the high pressure of the refrigerant circuit (10). The low-pressure sensor (62) is installed in the suction pipe (32). The low-pressure sensor (62) detects the low pressure of the refrigerant circuit (10).

[0043] The refrigerant leak sensor (70) is positioned around the user-side circuit (40a). The refrigerant leak sensor (70) is positioned, for example, in the internal space (S). Preferably, the refrigerant leak sensor (70) is positioned in an air passage circulating within the internal space (S). The refrigerant leak sensor (70) is a semiconductor type sensor that detects refrigerant. The refrigerant leak sensor (70) outputs a detection signal with increasing intensity (e.g., current value) as the concentration of leaked refrigerant increases. The refrigerant leak sensor (70) is not limited to a semiconductor type, but may also be of other types, such as an infrared type.

[0044] (5) Control Unit As shown in Figures 1 and 2, the refrigeration cycle device (1) has a control unit (100). The control unit (100) controls the refrigerant circuit (10) of the refrigeration cycle device (1). Detection signals from the various sensors described above are input to the control unit (100).

[0045] The control unit (100) includes a heat source controller (110) and a utilization controller (120). The heat source controller (110) is installed in the outdoor unit (20). The utilization controller (120) is installed in the cooling unit (40). The heat source controller (110) and the utilization controller (120) are connected to each other by wire or wireless.

[0046] The heat source controller (110) controls the heat source equipment installed in the outdoor unit (20). Specifically, the heat source controller (110) controls the ON / OFF status of the compressor (22), the rotational speed of the compressor (22), the ON / OFF status of the outdoor fan (21), the rotational speed of the outdoor fan (21), the state of the four-way switching valve (24), and the opening and closing of the heat source side shut-off valve (26). The utilization controller (120) controls the utilization equipment installed in the cooling unit (40). Specifically, the utilization controller (120) controls the ON / OFF status of the internal fan (41), the rotational speed of the internal fan (41), and the opening degree of the internal expansion valve (43).

[0047] As shown in Figure 2, the heat source controller (110) has a first processing unit (111), a first storage unit (112), and a first communication interface (113). The utilization controller (120) has a second processing unit (121), a second storage unit (122), and a second communication interface (123).

[0048] The first processing unit (111) and the second processing unit (121) are implemented by a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), or processing circuitry, which consist of one or more processor cores.

[0049] The first storage unit (112) and the first processing unit (111) are implemented by non-volatile memory and volatile memory. Non-volatile memory includes HDD (Hard Disk Drive), SSD (Solid State Drive), flash memory, ROM (Read Only Memory), etc. Volatile memory includes DRAM (Dynamic Random Access Memory) and SRAM (Solid State Drive), etc.

[0050] The first communication interface (113) and the second communication interface (123) are implemented by communication circuits that perform wired or wireless communication processing.

[0051] (6) Remote controller As shown in Figures 1 and 2, the refrigeration cycle device (1) has a remote controller (130). In this embodiment, the remote controller (130) is connected to the user controller (120) by wire or wireless connection. The remote controller (130) has an operation unit (131) and a display unit (132).

[0052] The control unit (131) consists of buttons, a touch panel, a mouse, etc., which are operated by the user. By operating the control unit (131), the user can switch the operating mode of the refrigeration cycle device (1), change various setting values ​​(judgment values) described later, and switch the screen of the display unit (132).

[0053] The display unit (132) is a display that displays various information on its screen. The display is composed of a liquid crystal panel or an organic EL display. The display may also be a touch panel that doubles as an operation unit. The display unit (132) constitutes a notification unit that notifies the results of a judgment operation. Specifically, the display unit (132) displays first information regarding an abnormality of the shut-off valve on its screen and notifies the operator of the first information. The operator includes users, contractors, maintenance companies, management companies, manufacturers, etc.

[0054] (7) Operating The refrigeration cycle unit (1) switches between normal operation and defrost operation. Figure 1 shows the refrigerant flow in normal operation with solid arrows and the refrigerant flow in defrost operation with dashed arrows.

[0055] In normal operation, the control unit (100) operates the compressor (22), outdoor fan (21), and interior fan (41), sets the four-way switching valve (24) to the first state, opens the heat source side shut-off valve (26), and adjusts the opening of the interior expansion valve (43) and expansion valve (30). In the refrigerant circuit (10), a refrigeration cycle is performed in which the outdoor heat exchanger (23) functions as a heat radiator (condenser) and the interior heat exchanger (42) functions as an evaporator. Specifically, the refrigerant compressed by the compressor (22) dissipates heat in the outdoor heat exchanger (23), some of the refrigerant flows into the injection channel (27), and the remaining refrigerant flows through the first channel (29a) of the subcooled heat exchanger (29). In the subcooled heat exchanger (29), the refrigerant flowing through the first channel (29a) is cooled by heat exchange with the refrigerant flowing through the second channel (29b). The refrigerant that flows out of the subcooled heat exchanger (29) is depressurized by the internal expansion valve (43), evaporates in the internal heat exchanger (42), and is drawn into the compressor (22). In the cooling unit (40), the air in the internal space (S) is cooled by the internal heat exchanger (42).

[0056] In defrost operation, the control unit (100) operates the compressor (22), the outdoor fan (21), and the internal fan (41), sets the four-way switching valve (24) to the second state, opens the heat source side shut-off valve (26), and adjusts the opening degree of the internal expansion valve (43). In the refrigerant circuit (10), a refrigeration cycle is performed in which the internal heat exchanger (42) functions as a heat radiator (condenser) and the outdoor heat exchanger (23) functions as an evaporator. Specifically, the refrigerant compressed by the compressor (22) dissipates heat in the internal heat exchanger (42), is depressurized by the internal expansion valve (43), evaporates in the outdoor heat exchanger (23), and is drawn back into the compressor (22). The refrigerant flowing inside the internal heat exchanger (42) melts the frost on the surface of the internal heat exchanger (42).

[0057] (8) First operation When the refrigerant leak sensor (70) detects a refrigerant leak, the control unit (100) executes a first operation to recover the refrigerant from the user-side circuit (40a) into the heat source-side circuit (20a). Specifically, in the above normal operation, if refrigerant leaks from inside the user-side circuit (40a) to the outside, the concentration of refrigerant around the user-side circuit (40a) increases. When the refrigerant leak sensor (70) detects a refrigerant leak, the control unit (100) acquires a signal indicating this. Upon acquiring the signal, the control unit (100) executes the first operation.

[0058] The first operation of this embodiment includes a first operation to reduce the opening of the shut-off mechanisms (26, 28) to a predetermined degree, a second operation to stop the compressor (22) when a first condition is met after the first operation, a third operation to completely close the shut-off mechanisms (26, 28) when a first condition is met after the first operation, and a fourth operation to completely close the internal expansion valve (43) when a first condition is met after the first operation. In the third operation, it is sufficient for either the external expansion valve (28) or the heat source side shut-off valve (26), which are the shut-off mechanisms (26, 28), to be completely closed. In the third operation of this embodiment, the external expansion valve (28) is completely closed.

[0059] The control flow, including the first operation of the refrigeration cycle device (1) of this embodiment, will be described below with reference to Figure 3.

[0060] (9) Control flow In step ST11, the control unit (100) switches the four-way switching valve (24) to the first state and performs normal operation.

[0061] In step ST12, the control unit (100) determines whether the refrigerant leak sensor (70) has detected a refrigerant leak. If a refrigerant leak is detected (YES in step ST12), step ST13 is executed. If no refrigerant leak is detected (NO in step ST12), step ST12 is executed again.

[0062] In step ST13, the control unit (100) performs the first operation. Specifically, the control unit (100) reduces the opening of the external expansion valve (28) to a predetermined degree. The predetermined degree is, for example, the degree to which the refrigerant on the outlet side of the external expansion valve (28) becomes saturated. In this case, the operation of the compressor (22) is controlled so that the refrigerant becomes saturated, for example, based on the detected value of the low-pressure sensor (62). The outlet side of the external expansion valve (28) is the downstream side of the refrigerant flow of the external expansion valve (28). Step ST13 corresponds to the first operation.

[0063] In step ST14, the control unit (100) determines whether the first condition is met. In this embodiment, the first condition is met when the high pressure reaches a predetermined value. The predetermined value is, for example, a value indicating a high pressure abnormality. If it is determined that the first condition is met (YES in step ST14), step ST15 is executed. If it is determined that the first condition is not met (NO in step ST14), step ST14 is executed again.

[0064] In step ST15, the control unit (100) reduces the rotational speed of the compressor (22) to a predetermined number of rotational speeds. This suppresses the rise in high pressure.

[0065] In step ST16, the control unit (100) completely closes the internal expansion valve (43). At this time, the compressor (22) is in operation, so the refrigerant downstream (secondary side) of the internal expansion valve (43) in the user-side circuit (40a) is drawn in by the compressor (22) and sent to the heat source-side circuit (20a). As a result, even if refrigerant leaks in part A on the secondary side of the internal expansion valve (43) in the user-side circuit (40a), leakage of refrigerant from this part A can be suppressed. The refrigerant sent to the heat source-side circuit (20a) is recovered by the receiver (25). Step ST16 corresponds to the fourth operation.

[0066] In step ST17, the control unit (100) determines whether the low pressure has dropped to a predetermined value. If it is determined that the low pressure has reached the predetermined value (YES in step ST17), step ST17 is executed again. If it is determined that the low pressure has not reached the predetermined value (NO in step ST17), step ST17 is executed again.

[0067] In step ST18, the control unit (100) stops the operation of the compressor (22). By operating the compressor (22) until the low pressure drops to a predetermined value, the refrigerant remaining in the low-pressure line is recovered to the heat source side circuit (20a). Step ST18 corresponds to the second operation.

[0068] In step ST19, the control unit (100) completely closes the external expansion valve (28). Step ST19 corresponds to the third operation. By completely closing the external expansion valve (28) and the internal expansion valve (43) in this way, leakage of refrigerant from the heat source side circuit (20a) to the utilization side circuit (40a) is suppressed. Therefore, even if refrigerant leaks in part B on the upstream side (primary side) of the internal expansion valve (43) in the utilization side circuit (40a), leakage of refrigerant from the heat source side circuit (20a) from this part B can be suppressed.

[0069] (10) Features (10-1) The refrigeration cycle device (1) of this embodiment includes a control unit (100) that, when a refrigerant leak sensor (70) detects a refrigerant leak, performs a first operation to recover the refrigerant from the utilization side circuit (40a) to the heat source side circuit (20a). The first operation includes a first operation to reduce the external expansion valve (28) to a predetermined opening, a second operation to stop the compressor (22) if a first condition is met after the first operation, and a third operation to completely close the external expansion valve (28) if a first condition is met after the first operation.

[0070] According to this embodiment, in the first operation, reducing the external expansion valve (28) to a predetermined opening degree by the first operation allows for the recovery of refrigerant in the connecting pipes (5,6) into the heat source side circuit (20a) compared to fully closing the external expansion valve (28). This suppresses the remaining refrigerant in the connecting pipes (5,6). Furthermore, the second and third operations suppress the flow of refrigerant from the heat source side circuit (20a) to the connecting pipes (5,6) and the internal heat exchanger (42) after the compressor (22) has stopped.

[0071] (10-2) The first operation of this embodiment includes a fourth operation in which the internal expansion valve (43) is fully closed after the first operation. This makes it possible to suppress the leakage (flow) of refrigerant into the user-side circuit (40a) after the compressor (22) has been stopped.

[0072] (10-3) The first condition of this embodiment is met when the high pressure reaches a predetermined value. This makes it possible to suppress the rise in high pressure during the first operation.

[0073] (10-4) In this embodiment, the predetermined opening degree of the external expansion valve (28) in the first operation is such that the refrigerant on the outlet side of the external expansion valve (28) becomes saturated. This suppresses the rise in high pressure during the first operation, thereby preventing abnormal high pressure.

[0074] (10-5) The refrigeration cycle device (1) of this embodiment includes a subcooled heat exchanger (29) connected to a heat source side circuit (20a) and a heat source side shut-off valve (26). The heat source side shut-off valve (26) is provided downstream of the first flow path (29a) of the subcooled heat exchanger (29). The external expansion valve (28) is an expansion valve and is provided downstream of the heat source side shut-off valve (26). In this way, even with a refrigeration cycle device (1) equipped with a subcooled heat exchanger (29), performing a first operation can suppress the residual refrigerant in the connecting pipes (5,6) and suppress the leakage of refrigerant from the heat source side circuit (20a) to the utilization side circuit (40a) after the compressor (22) has been stopped.

[0075] (11) Variant The first operation may operate as follows: (11-1) Torture 1 The control flow of Modification 1 of the refrigeration cycle device (1) will be explained with reference to Figure 4.

[0076] Steps ST21 to ST24 are the same as steps ST11 to ST14 of the control flow in the above embodiment, so their explanation is omitted.

[0077] In step ST25, the control unit (100) completely closes the external expansion valve (28). At this time, the compressor (22) is in operation, so the refrigerant in the liquid side connecting pipe (5), the utilization side circuit (40a), and the gas side connecting pipe (6), which are downstream of the external expansion valve (28), is drawn in by the compressor (22) and sent to the heat source side circuit (20a). Step ST25 corresponds to the third operation.

[0078] In step ST26, the control unit (100) stops the operation of the compressor (22). Step ST26 corresponds to the second operation. By stopping the compressor (22), the circulation of the refrigerant is stopped, and the flow of refrigerant from the heat source side circuit (20a) into the utilization side circuit (40a) can be suppressed.

[0079] (11-2) Variation 2 The control flow of modified example 2 of the refrigeration cycle device (1) will be explained with reference to Figure 5.

[0080] Steps ST31 to ST34 are the same as steps ST11 to ST14 of the control flow in the above embodiment, so their explanation is omitted.

[0081] In step ST35, the control unit (100) stops the operation of the compressor (22). Steps ST34 and ST35 correspond to the second operation.

[0082] In step ST36, the control unit (100) stops the compressor (22) and then completely closes the external expansion valve (28) and the internal expansion valve (43). Step ST34 and the operation of completely closing the external expansion valve (28) correspond to the third operation. Step ST34 and the operation of completely closing the internal expansion valve (43) correspond to the fourth operation.

[0083] (12) Other embodiments The above embodiments and each of the above modifications may be configured as follows.

[0084] The control unit (100) may be located in the remote controller (130). The control unit (100) may also be located in a terminal device connected to the refrigeration cycle device (1) via wired or wireless connection. The terminal device may include a server device, a central monitoring device, or a worker's communication terminal. The communication terminal may include a smartphone, tablet, or personal computer.

[0085] The first condition described above may be met when a predetermined time has elapsed after the execution of the first operation. The predetermined time can be any time; for example, it may be the time it takes for the high pressure to rise to a certain level. Alternatively, the first condition may be met when the low pressure reaches a predetermined value.

[0086] The third action may be an action to completely close the heat source side shut-off valve (26). Alternatively, in the third action, it is sufficient that at least one of the heat source side shut-off valve (26) and the external expansion valve (28) is completely closed, and both the heat source side shut-off valve (26) and the external expansion valve (28) may be completely closed.

[0087] The refrigerant circuit (10) of the refrigeration cycle device (1) does not necessarily have a heat source side shut-off valve (26). In this case, in the third operation, the control unit (100) completely closes the external expansion valve (28).

[0088] The refrigerant circuit (10) of the refrigeration cycle device (1) does not necessarily have a subcooling heat exchanger (29) and an injection flow path (27).

[0089] (13) Additional remarks The control method of this disclosure includes any of the steps of the embodiments and variations described above.

[0090] The programs of this disclosure are used to cause a computer to perform a control method which includes steps of any of the embodiments and variations described above.

[0091] While embodiments and modifications have been described above, it will be understood that a variety of changes in form and details are possible without departing from the spirit and scope of the claims. Furthermore, these embodiments and modifications may be combined or substituted as appropriate, as long as they do not impair the functions of the subject matter of this disclosure. The terms “First,” “Second,” etc., used above are used to distinguish the phrases to which these terms are attached, and do not limit the number or order of such phrases. [Industrial applicability]

[0092] As described above, this disclosure is useful for refrigeration cycle devices, control methods, and programs. [Explanation of Symbols]

[0093] 1. Refrigeration cycle system 10 Refrigerant Circuit 20a Heat source side circuit 22 Compressor 23 Outdoor heat exchanger (heat source side heat exchanger) 26. Heat source side shut-off valve (shut-off mechanism) 28. External expansion valve (first shut-off valve, shut-off mechanism) 29 Subcooling heat exchanger 29a First channel 29b Second channel 30 Expansion valve 40 Cooling Unit (Unit Used) 40a User-side circuit 42 Internal heat exchanger (user side heat exchanger) 43. Internal expansion valve (second shut-off valve) 70 Refrigerant leak sensor 100 Control Unit S Interior space (target space)

Claims

1. A refrigerant circuit (10) includes a heat source side circuit (20a) to which a compressor (22), a heat source side heat exchanger (23), and a shut-off mechanism (26, 28) are connected, and a utilization side circuit (40a) to which a utilization side heat exchanger (42) is connected, A utilization unit (40) having the aforementioned utilization-side heat exchanger (42) and air conditioning the target space (S), A refrigerant leak sensor (70) for detecting refrigerant leaks in the user-side circuit (40a), The system includes a control unit (100) that, when the refrigerant leak sensor (70) detects a refrigerant leak, performs a first operation to recover the refrigerant from the utilization side circuit (40a) to the heat source side circuit (20a), The first operation described above is A first operation to reduce the opening of the aforementioned shut-off mechanism (26, 28) to a predetermined opening, If the first condition is met after the first operation, a second operation is performed to stop the compressor (22), If the first condition is met after the first operation, a third operation is performed to completely close the shut-off mechanism (26, 28). The second operation is performed either before or after the third operation. The first condition is met when the high pressure reaches a predetermined value, when a predetermined time has elapsed, or when the low pressure reaches a predetermined value. Refrigeration cycle device.

2. The user-side circuit (40a) has a second shut-off valve (43) whose valve opening degree can be adjusted. In the first operation described above, after stopping the compressor (22), the shut-off mechanisms (26, 28) and the second shut-off valve (43) are fully closed. The refrigeration cycle apparatus according to claim 1.

3. The user-side circuit (40a) has a second shut-off valve (43) whose valve opening degree can be adjusted. The first operation includes a fourth operation in which, if the first condition is met after the first operation, the second shut-off valve (43) is completely closed. The refrigeration cycle apparatus according to claim 1.

4. The shut-off mechanism (26, 28) includes a first shut-off valve (28) with adjustable valve opening, The predetermined opening degree of the first shut-off valve (28) in the first operation is such that the refrigerant on the outlet side of the first shut-off valve (28) becomes saturated. A refrigeration cycle apparatus according to any one of claims 1 to 3.

5. A supercooled heat exchanger (29) connected to the heat source side circuit (20a), The aforementioned shut-off mechanism (26, 28) further comprises a heat source side shut-off valve (26), The supercooled heat exchanger (29) has a first flow path (29a) and a second flow path (29b) through which a refrigerant that cools the refrigerant in the first flow path (29a) flows. The heat source side shut-off valve (26) is provided downstream of the first flow path (29a) in the refrigerant flow when the heat source side heat exchanger (23) functions as a heat radiator. The first shut-off valve (28) is an expansion valve and is provided downstream of the heat source side shut-off valve (26). The refrigeration cycle apparatus according to claim 4.

6. A refrigerant circuit (10) includes a heat source side circuit (20a) to which a compressor (22), a heat source side heat exchanger (23), and a shut-off mechanism (26, 28) are connected, and a utilization side circuit (40a) to which a utilization side heat exchanger (42) is connected, A utilization unit (40) having the aforementioned utilization-side heat exchanger (42) and air conditioning the target space (S), A refrigerant leak sensor (70) for detecting refrigerant leaks in the user-side circuit (40a), A control method for a refrigeration cycle device comprising a control unit (100), The control unit, When a refrigerant leak is detected by the refrigerant leak sensor (70), a first operation is performed to recover the refrigerant from the user-side circuit (40a) to the heat source-side circuit (20a). The first operation described above is A first operation to reduce the opening of the aforementioned shut-off mechanism (26, 28) to a predetermined opening, If the first condition is met after the first operation, a second operation is performed to stop the compressor (22), If the first condition is met after the first operation, a third operation is performed to completely close the shut-off mechanism (26, 28). The second operation is performed either before or after the third operation. The first condition is met when the high pressure reaches a predetermined value, when a predetermined time has elapsed, or when the low pressure reaches a predetermined value. Control method.

7. A program for causing the control method described in claim 6 to be executed.

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