Outdoor unit control device, outdoor unit, heat pump device, and outdoor unit control method

Abstract

Provided is an outdoor unit control device that can minimize leakage of a refrigerant, even in a heat pump device that is provided with a water heat exchanger. This outdoor unit control device controls an outdoor unit (1) that is provided with a compressor (17), an outdoor heat exchanger (30), a water heat exchanger (19), an expansion valve (45), a four-way valve (49), and a water circuit (W) for sending, to an indoor unit, water which has undergone heat exchange in the water heat exchanger (19). The outdoor unit control device has a cooling mode in which the four-way valve (49) is switched, the water heat exchanger (19) is operated as an evaporator, and the outdoor heat exchanger (30) is operated as a condenser, and a heating mode in which the four-way valve (49) is switched, the water heat exchanger (19) is operated as a condenser, and the outdoor heat exchanger (30) is operated as an evaporator. When leakage of a refrigerant to the water circuit (W) is detected, the outdoor unit control device sets the cooling mode and then fully closes the expansion valve (45).

Description

Control device for outdoor unit, outdoor unit, heat pump device, and outdoor unit control method

[0001] The present disclosure relates to a control device for an outdoor unit, an outdoor unit, a heat pump device, and an outdoor unit control method.

[0002] R290, which is propane as a natural refrigerant, has a small GWP (global warming potential), so its use as a refrigerant for heat pump devices is being promoted. However, R290 is classified as a highly flammable refrigerant and there is a risk of ignition when it leaks.

[0003] Patent Document 1 discloses that when a refrigerant leak is detected, the user is notified and the refrigerant is recovered in the outdoor unit. The air conditioner of Patent Document 1 is of a direct expansion type (direct expansion method) in which the refrigerant is led to the indoor unit for indoor air conditioning.

[0004] For the above-mentioned direct expansion type, there is known a heat pump device in which a refrigerant circuit is formed in the outdoor unit and a water heat exchanger for exchanging heat between the refrigerant and water (heat medium) is provided in this refrigerant circuit (see Patent Document 2). The water heat-exchanged by the water heat exchanger is sent to the indoor unit, which is the heat utilization destination, via the water circuit.

[0005] Japanese Patent Application Laid-Open No. 2022-24290 Japanese Patent Application Laid-Open No. 2024-51511

[0006] In Patent Document 1, since it is of the direct expansion type, when the refrigerant leaks indoors, the refrigerant is recovered from the indoor unit to the outdoor unit.

[0007] On the other hand, in the heat pump device of Patent Document 2, the refrigerant circuit and the water circuit are separated by the water heat exchanger, and it is not configured such that the refrigerant flows into the indoor unit. Also, a gas separator for separating and discharging the gas mixed in the water is often provided in the water circuit connecting the water heat exchanger and the indoor unit. This prevents the refrigerant from leaking into the water and being led to the indoor unit via the water circuit.

[0008] However, even if a gas separator is installed, there is still a risk that the refrigerant may leak into the water due to some failure or the like and be led to the indoor unit. Therefore, even in a heat pump device equipped with a water heat exchanger, it is necessary to minimize the leakage of the refrigerant into the water circuit.

[0009] This disclosure has been made in view of these circumstances and aims to provide an outdoor unit control device, an outdoor unit, a heat pump system, and an outdoor unit control method that can minimize refrigerant leakage into the heat transfer medium circuit even in a heat pump system equipped with a heat transfer medium heat exchanger.

[0010] A control device for an outdoor unit according to one aspect of the present disclosure includes: a compressor for compressing a refrigerant; a refrigerant circuit through which the refrigerant discharged from the compressor circulates; an outdoor heat exchanger provided in the refrigerant circuit for exchanging heat between the refrigerant and outside air; a heat exchanger provided in the refrigerant circuit for exchanging heat between the refrigerant and a liquid heat transfer medium; an expansion valve provided in the refrigerant circuit for expanding the refrigerant; a switching valve for switching the flow of the refrigerant discharged from the compressor to the outdoor heat exchanger or the heat exchanger; and heat exchange in the heat exchanger. An outdoor unit control device for controlling an outdoor unit comprising a heat transfer circuit that sends a heated heat transfer medium to a heat utilization destination, having a cooling mode in which the switching valve is switched to operate the heat transfer medium heat exchanger as an evaporator and the outdoor heat exchanger as a condenser, and a heating mode in which the switching valve is switched to operate the heat transfer medium heat exchanger as a condenser and the outdoor heat exchanger as an evaporator, wherein when a leak of refrigerant into the heat transfer circuit is detected, the device switches to the cooling mode and completely closes the expansion valve.

[0011] An outdoor unit according to one aspect of the present disclosure includes a compressor for compressing a refrigerant, a refrigerant circuit through which the refrigerant discharged from the compressor circulates, an outdoor heat exchanger provided in the refrigerant circuit for exchanging heat between the refrigerant and outside air, a heat exchanger provided in the refrigerant circuit for exchanging heat between the refrigerant and a liquid heat transfer medium, an expansion valve provided in the refrigerant circuit for expanding the refrigerant, a switching valve for switching the flow of the refrigerant discharged from the compressor to the outdoor heat exchanger or the heat exchanger, a heat transfer medium circuit for sending the heat transfer medium that has been heat-exchanged in the heat exchanger to a heat utilization destination, and the above-mentioned control device for the outdoor unit.

[0012] A heat pump system according to one aspect of this disclosure comprises the above-mentioned outdoor unit and a heat utilization unit connected to the outdoor unit.

[0013] An outdoor unit control method according to one aspect of the present disclosure includes: a compressor for compressing a refrigerant; a refrigerant circuit through which the refrigerant discharged from the compressor circulates; an outdoor heat exchanger provided in the refrigerant circuit for heat exchange between the refrigerant and outside air; a heat exchanger provided in the refrigerant circuit for heat exchange between the refrigerant and a liquid heat transfer medium; an expansion valve provided in the refrigerant circuit for expanding the refrigerant; a switching valve for switching the flow of the refrigerant discharged from the compressor to the outdoor heat exchanger or the heat exchanger; and heat exchange in the heat exchanger. An outdoor unit control method for controlling an outdoor unit comprising a heat transfer circuit that sends a heated heat transfer medium to a heat utilization destination, comprising: a cooling mode in which the switching valve is switched to operate the heat transfer medium heat exchanger as an evaporator and the outdoor heat exchanger as a condenser; and a heating mode in which the switching valve is switched to operate the heat transfer medium heat exchanger as a condenser and the outdoor heat exchanger as an evaporator, wherein when a leak of refrigerant into the heat transfer circuit is detected, the system is switched to the cooling mode and the expansion valve is fully closed.

[0014] Even in heat pump systems equipped with a heat transfer medium heat exchanger, refrigerant leakage into the heat transfer medium circuit can be minimized.

[0015] This is a perspective view showing an outdoor unit according to one embodiment of the present disclosure. This is a longitudinal cross-sectional view of the outdoor unit in Figure 1. This is a schematic diagram of the refrigeration cycle of the heat pump system. This is a flowchart showing refrigerant leakage suppression control.

[0016] An embodiment of the present disclosure will be described below with reference to the drawings. Figure 1 shows an outdoor unit 1 used in a heat pump system. The outdoor unit 1 in Figure 1 is shown with the panel of the machine room 7 removed.

[0017] The outdoor unit 1 is connected to the indoor unit (heat utilization unit) via a water circuit using water piping (heat transfer piping) not shown. Water circulates between the outdoor unit 1 and the indoor unit through the water piping. As a result, the heat or cold generated by the outdoor unit 1 is sent to the indoor unit via the water piping, providing heat or cold to the room.

[0018] As shown in Figure 1, the outdoor unit 1 has a roughly rectangular prism-shaped housing 3. The bottom of the housing 3 is a sheet metal base 4. The base 4 has base legs 4a provided on each side along the longitudinal direction, and a roughly flat plate portion 4b provided between the upper ends of the base legs 4a on both sides. The flat plate portion 4b extends roughly horizontally, and various devices are installed on top of it. The flat plate portion 4b has irregularities formed by press working.

[0019] As shown in Figure 1, the housing 3 contains a fan room 5 and a machine room 7 located above the base 4, separated to the left and right by a partition wall 9.

[0020] The fan chamber 5 is located on the left side in Figure 1. Inside the fan chamber 5 are an outdoor fan (not shown) and an outdoor heat exchanger 30 (see Figure 2). The outdoor heat exchanger 30 is bent into an L-shape so as to form the side and back of the fan chamber 5. The outside air drawn in by the outdoor fan exchanges heat with the refrigerant circulating in the outdoor heat exchanger 30. After exchanging heat with the refrigerant, the outside air is discharged to the outside through the fan opening 11.

[0021] The machine room 7 is located on the right side in Figure 1. The machine room 7 is provided with a plate-shaped sub-base 13 on top of the base 4 (specifically, the flat plate portion 4b). The sub-base 13 is rectangular in shape when viewed from above and is large enough to cover almost the entire area below the machine room 7. However, a predetermined gap is formed around the four sides of the sub-base 13 between it and the side walls and partition walls 9 of the opposing housing 3.

[0022] As shown in Figure 2, multiple sub-base support members 15 equipped with vibration-damping rubber are provided between the base 4 and the sub-base 13. Each sub-base support member 15 supports the sub-base 13 relative to the base 4.

[0023] As shown in Figure 1, the machine room 7 is equipped with a compressor 17, a water heat exchanger 19, a gas separator 21, a control box 23, and the like, above the sub-base 13.

[0024] The compressor 17 is, for example, a rotary compressor, and compresses a flammable refrigerant such as R290. As shown in Figure 2, the lower part of the compressor 17 is provided with compressor legs 17a equipped with vibration-damping rubber. The compressor legs 17a are mounted on the sub-base 13. The compressor legs 17a equipped with vibration-damping rubber reduce the vibrations of the compressor 17 transmitted to the sub-base 13. The sub-base 13 does not have unnecessary through holes, except for holes for mounting equipment such as the sub-base support member 15 and the compressor legs 17a. Therefore, after the equipment is mounted, there are basically no through holes in the sub-base 13.

[0025] The refrigerant compressed by the compressor 17 is sent to the water heat exchanger 19 or the outdoor heat exchanger 30 via a four-way valve (not shown). The compressor 17, the four-way valve (not shown), the water heat exchanger 19, the outdoor heat exchanger 30, the expansion valve (not shown), and the refrigerant piping connecting them form a refrigerant circuit through which the refrigerant circulates.

[0026] The water heat exchanger 19 exchanges heat between the refrigerant and water (heat transfer medium). After the water has exchanged heat with the refrigerant, the gas (air, refrigerant, etc.) is separated by the gas separator 21, and then the water is guided to the indoor unit through the water supply pipe 25. After the water has exchanged heat with the indoor air in the indoor unit, it is returned to the water heat exchanger 19 through the water return pipe 26. In this way, the water circulates between the water heat exchanger 19 and the indoor unit via the water circuit.

[0027] A water connection pipe 46 is connected to the side of the gas separator to guide water from the water heat exchanger 19, and a water supply pipe 25 is connected to the bottom of the gas separator 21. Water flowing in through the water connection pipe 46 is separated into gas and liquid within the gas separator 21, and the treated water is discharged into the water supply pipe 25.

[0028] The gas separator 21 has an ejection nozzle 21a that protrudes upward from the top of the gas separator 21 to eject the separated gas (such as refrigerant or air). The ejection nozzle 21a is equipped with a check valve, and when the separated gas exceeds a predetermined pressure, the check valve opens and the gas is ejected to the outside. The direction of gas ejection is horizontal, as indicated by arrow A1.

[0029] A water relief outlet 21b is provided on the side of the gas separator, which has a pressure relief valve that opens when the pressure of the incoming water exceeds a predetermined value. A water discharge pipe is connected to the water relief outlet 21b (not shown in the figure) to guide the water to the outside of the outdoor unit 1.

[0030] The control box 23 has a sealed structure that houses electrical equipment such as capacitors and coils inside. Furthermore, a terminal block equipped with electrical terminals for receiving power from the outside is provided inside the control box 23.

[0031] Figure 2 also shows the same compressor 17, water heat exchanger 19, and gas separator 21 as in Figure 1. An accumulator 28 is shown to the side of the compressor 17. An outdoor heat exchanger 30 is also shown on the right side of Figure 2. The outdoor heat exchanger 30 is installed in the fan room 5 (see Figure 1) as described above.

[0032] Although not shown in the diagram, the base 4 is provided with a drain hole in a position corresponding to the fan chamber 5. The drain hole is, for example, circular in shape, with a diameter of, for example, 20 mm. The drain hole is located on the lower surface, which is the lowest position on the flat plate portion 4b of the base 4. The lower surface extends continuously across the machine chamber 7. The lower surface is inclined so that the drain hole faces downwards. This allows condensed water to adhere to equipment such as the outdoor heat exchanger 30 inside the housing 3 and flow downwards, so that the drain water can be discharged to the outside through the drain hole via the lower surface.

[0033] As shown in Figure 2, the base 4 is provided with a refrigerant discharge hole 34 at a position corresponding to the machine room 7. Through the refrigerant discharge hole 34, the refrigerant released into the machine room 7 is discharged to the outside (atmosphere).

[0034] The refrigerant discharge hole 34 is, for example, circular in shape, with a diameter of 30 mm or more, preferably about 60 mm. In other words, the area of ​​the refrigerant discharge hole 34 is larger than the area of ​​the drain hole.

[0035] As shown in Figure 2, a resin mesh 40 is provided at the refrigerant discharge hole 34 to prevent small animals such as insects from entering the inside of the housing 3 from the outside.

[0036] A refrigerant detection sensor 42 is installed below the machine room 7. The refrigerant detection sensor 42 detects refrigerant leaking into the machine room 7. The detection output of the refrigerant detection sensor 42 is transmitted to a control unit (not shown). The control unit determines that a refrigerant leak has occurred when the concentration of refrigerant detected by the refrigerant detection sensor 42 exceeds a predetermined value. The refrigerant detection sensor 42 is installed below the gas separator 21.

[0037] The control unit is an outdoor unit control device that controls each component of the outdoor unit 1, and is provided, for example, in the control box 23. The control unit consists of, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and a computer-readable storage medium. A series of processes for realizing various functions are stored in the storage medium in the form of a program, for example, and the CPU reads this program into the RAM and performs information processing and calculations to realize the various functions. The program may be pre-installed on the ROM or other storage medium, provided in a state where it is stored on a computer-readable storage medium, or distributed via wired or wireless communication means. Computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, semiconductor memory, etc.

[0038] Figure 3 shows a schematic configuration of the refrigeration cycle of a heat pump system using the outdoor unit 1 with the above configuration. Note that the same components shown in Figures 1 and 2 are indicated by the same reference numerals.

[0039] The refrigerant circuit C that constitutes the refrigeration cycle includes a compressor 17, a water heat exchanger 19, an expansion valve 45, and an outdoor heat exchanger 30. A four-way valve (switching valve) 49 is provided downstream of the discharge pipe 47 connected to the discharge port of the compressor 17. An accumulator 28 and a suction pressure sensor 29 are provided upstream of the suction port of the compressor 17. The output of the suction pressure sensor 29 is transmitted to the control unit.

[0040] A liquid refrigerant pipe 51 between the expansion valve 45 and the heat exchanger 19 is provided with a liquid pipe temperature sensor 53 in the immediate vicinity of the heat exchanger 19. The output of the liquid pipe temperature sensor 53 is transmitted to the control unit.

[0041] A water circuit W is connected to the heat exchanger 19. The water circuit W is provided with an indoor unit (heat utilization unit) not shown, a gas separator 21, and a water pump (heat medium pump) 55. The gas separator 21 is provided on the water outlet side of the heat exchanger 19, and the water pump 55 is provided on the water inlet side of the heat exchanger 19. A water inlet temperature sensor 57 is provided on the water inlet side of the heat exchanger 19, and a water outlet temperature sensor 59 is provided on the water outlet side of the heat exchanger 19. The output of each temperature sensor 57 is transmitted to the control unit.

[0042] The heat pump device shown in FIG. 3 operates as follows. <Cooling mode> In the cooling mode, the four-way valve 49 is switched according to the command of the control unit and operates as shown by the solid line arrow. The high-pressure refrigerant discharged from the compressor 17 passes through the four-way valve and is sent to the outdoor heat exchanger 30. In the outdoor heat exchanger 30, heat is released to the outside air and the refrigerant is condensed. The condensed and liquefied refrigerant is sent to the expansion valve 45, and the expansion valve 45 reduces the pressure of the refrigerant to a predetermined pressure. The opening degree of the expansion valve 45 is controlled by the control unit.

[0043] The refrigerant decompressed by the expansion valve 45 is sent to the heat exchanger 19, absorbs heat from the water flowing through the heat exchanger 19, and is evaporated. The refrigerant evaporated in the heat exchanger 19 is guided to the suction side of the compressor 17 through the four-way valve 49 and the accumulator 28.

[0044] The cold water generated by being cooled by the latent heat of evaporation of the refrigerant in the heat exchanger 19 flows to the gas separator 21 by the water pump 55. In the gas separator 21, gases such as the refrigerant and air contained in the cold water are separated, and the separated cold water is sent to the indoor unit. The cold water that has completed cooling in the indoor unit is returned to the water pump 55 and is again guided to the heat exchanger 19.

[0045] <Heating Mode> When in the heating mode, the four-way valve 49 is switched according to the command of the control unit and operates as shown by the dashed arrow. The high-pressure refrigerant discharged from the compressor 17 passes through the four-way valve and is sent to the water heat exchanger 19. In the water heat exchanger 19, heat is released to the water introduced from the water circuit W, and the water is heated to become hot water.

[0046] The refrigerant condensed and liquefied in the water heat exchanger 19 is sent to the expansion valve 45, and the refrigerant is depressurized to a predetermined pressure by the expansion valve 45. The opening degree of the expansion valve 45 is controlled by the control unit.

[0047] The refrigerant depressurized by the expansion valve 45 is sent to the outdoor heat exchanger 30, absorbs heat from the outside air and evaporates. The refrigerant evaporated in the outdoor heat exchanger 30 is guided to the suction side of the compressor 17 through the four-way valve 49 and the accumulator 28.

[0048] The hot water generated by being heated by the latent heat of condensation of the refrigerant in the water heat exchanger 19 flows to the gas separator 21 by the water pump 55. In the gas separator 21, gases such as refrigerant and air contained in the hot water are separated, and the separated hot water is sent to the indoor unit. The hot water that has completed heating in the indoor unit is returned to the water pump 55 and is guided to the water heat exchanger 19 again.

[0049] <Refrigerant Leakage Suppression Control> Next, the operation when refrigerant leaks into the water circuit W will be described. The gas separator 21 separates gases such as refrigerant and air contained in the water introduced from the water heat exchanger 19. When a large amount of gas leaks into the water due to some failure, the pressure of the gas separated by the gas separator 21 rises, and the gas is ejected from the ejection part 21a (see FIG. 2) into the outdoor unit 1. Since the refrigerant contained in the ejected gas has a greater specific gravity than air, it flows downward due to its own weight, passes through the side of the sub-base 13, reaches the base 4, and is discharged to the outside through the refrigerant discharge hole 34 formed in the base 4. When the refrigerant reaches the refrigerant detection sensor 42 while flowing down inside the outdoor unit 1, the refrigerant detection sensor 42 detects the refrigerant concentration and transmits it to the control unit. When the control unit determines that refrigerant leakage has occurred when the refrigerant concentration exceeds a predetermined value, the following refrigerant leakage suppression control is performed.

[0050] As shown in Figure 4, when refrigerant leakage into the water flowing through the water circuit W is detected (step S1), the system switches to cooling mode (step S2). If the system is in heating mode, the four-way valve 49 is switched to change to cooling mode; if it is in cooling mode, the system continues in cooling mode.

[0051] Then, the expansion valve 45 is completely closed (step S3). As a result, the refrigerant in the water heat exchanger 19 is drawn into the compressor 17 and recovered in the outdoor heat exchanger 30, and the refrigerant pressure in the water heat exchanger 19 decreases.

[0052] The refrigerant pressure in the water heat exchanger 19 is controlled to be less than or equal to the water pressure in the water heat exchanger 19 (step S4). Specifically, the refrigerant pressure in the water heat exchanger 19 is calculated based on the measurement value of the suction pressure sensor 29 (see Figure 3), and the rotational speed of the compressor 17 is controlled and / or the compressor 17 is started and stopped to keep it less than or equal to the water pressure flowing through the water circuit W (the set value of the water pressure, for example, 0.1 MPa (gauge pressure)). However, the refrigerant pressure is controlled so that it does not fall below atmospheric pressure so that air does not enter the refrigerant circuit C. Alternatively, a pressure sensor may be installed in the water circuit W and the control may be performed using the measured value of the water pressure.

[0053] After the refrigerant pressure in the water heat exchanger 19 reaches the desired value, the expansion valve 45 may be opened from the fully closed position to maintain that refrigerant pressure, and the degree of opening may be adjusted as appropriate.

[0054] Next, the discharge flow rate of the water pump 55 is reduced (step S5). This reduces the amount of refrigerant supplied to the indoor unit. Furthermore, reducing the water flow rate improves the refrigerant separation efficiency of the gas separator 21. However, to prevent the water in the water heat exchanger 19 from freezing, the water pump 55 is controlled not to stop.

[0055] Next, the refrigerant temperature of the water heat exchanger 19 is calculated based on the liquid pipe temperature sensor 53, and freeze prevention control is performed in the water heat exchanger 19 to prevent the water from freezing (step S6). Specifically, the rotational speed of the compressor 17 is controlled, and / or the compressor 17 is started and stopped to perform the control.

[0056] Then, after a predetermined time has elapsed, the operation of the outdoor unit 1 is stopped (step S7), the user is notified (step S8), and the refrigerant leakage suppression control is terminated.

[0057] The effects of this embodiment described above are as follows. If refrigerant leakage into the water circuit W is detected, it is highly likely that refrigerant has leaked into the water in the water heat exchanger 19. Therefore, by setting the system to cooling mode and completely closing the expansion valve 45, the refrigerant pressure in the water heat exchanger 19, which is used as an evaporator, is reduced. This minimizes the leakage of refrigerant into the water in the water heat exchanger 19.

[0058] The refrigerant separated from the water by the gas separator 21 is detected by the refrigerant detection sensor 42, and the leakage of refrigerant into the water circuit W is determined. This allows for accurate determination of refrigerant leakage into the water.

[0059] Since the refrigerant pressure in the water heat exchanger 19 is controlled to be less than or equal to the water pressure, mixing of the refrigerant with the water can be avoided. While it is preferable to set the target value of the refrigerant pressure lower than the water pressure, it may also be controlled to remain within a predetermined differential pressure range.

[0060] If the expansion valve 45 is fully closed and the cooling mode is operated, the pressure in the water heat exchanger 19 will drop, causing the circulating water to freeze, which may lead to damage in some cases. Therefore, the temperature of the water heat exchanger 19 is controlled to prevent the water from freezing.

[0061] When a refrigerant leak into the water circuit W is detected, the discharge flow rate of the water pump 55 that circulates the water through the water circuit W is reduced. This reduces the amount of refrigerant supplied to the indoor unit. Furthermore, reducing the water flow rate improves the refrigerant separation efficiency in the gas separator 21.

[0062] The outdoor unit control device, outdoor unit, heat pump device, and outdoor unit control method described in each embodiment above can be understood, for example, as follows.

[0063] A control device for an outdoor unit according to a first aspect of this disclosure includes a compressor (17) for compressing a refrigerant, a refrigerant circuit (C) through which the refrigerant discharged from the compressor circulates, an outdoor heat exchanger (30) provided in the refrigerant circuit for exchanging heat between the refrigerant and outside air, a heat transfer medium heat exchanger (19) provided in the refrigerant circuit for exchanging heat between the refrigerant and a liquid heat transfer medium, an expansion valve (45) provided in the refrigerant circuit for expanding the refrigerant, a switching valve (49) for switching the flow of the refrigerant discharged from the compressor to the outdoor heat exchanger or the heat transfer medium heat exchanger, and the heat transfer medium An outdoor unit control device for controlling an outdoor unit (1) which includes a heat transfer medium circuit (W) that sends a heat transfer medium that has been heat-exchanged in a heat exchanger to a heat utilization destination, has a cooling mode in which the switching valve is switched to operate the heat transfer medium heat exchanger as an evaporator and the outdoor heat exchanger as a condenser, and a heating mode in which the switching valve is switched to operate the heat transfer medium heat exchanger as a condenser and the outdoor heat exchanger as an evaporator, and when a leak of refrigerant into the heat transfer medium circuit is detected, the device switches to the cooling mode and completely closes the expansion valve.

[0064] If refrigerant leakage into the heat transfer circuit is detected, it is highly likely that refrigerant has leaked into the heat transfer medium in the heat transfer heat exchanger. Therefore, by switching to cooling mode and completely closing the expansion valve, the refrigerant pressure in the heat transfer heat exchanger, which is acting as the evaporator, is reduced. This minimizes refrigerant leakage into the heat transfer medium in the heat transfer heat exchanger.

[0065] In the first embodiment, the outdoor unit control device according to the second aspect of the present disclosure includes a gas separator (21) provided in the heat transfer medium circuit for separating gaseous refrigerant from the heat transfer medium, and a refrigerant detection sensor (42) capable of detecting the refrigerant separated from the gas separator, wherein the refrigerant detection sensor detects leakage of refrigerant into the heat transfer medium circuit.

[0066] The gas separator separates the refrigerant that has leaked into the heat transfer medium. The refrigerant separated by the gas separator is detected by a refrigerant detection sensor, and the leakage of refrigerant into the heat transfer medium circuit is determined. This allows for accurate determination of refrigerant leakage into the heat transfer medium.

[0067] In the third aspect of the present disclosure, the control device for an outdoor unit controls the refrigerant pressure of the heat exchanger to approach the heat transfer fluid pressure of the heat exchanger, in the first or second aspect.

[0068] By controlling the refrigerant pressure in the heat exchanger to approach the heat transfer medium pressure, the pressure difference between the heat transfer medium and the refrigerant is reduced. This reduces the amount of refrigerant mixed into the heat transfer medium. The target value of the refrigerant pressure is preferably small relative to the heat transfer medium pressure, but it may also be controlled to maintain a differential pressure within a predetermined range. The refrigerant pressure can be controlled, for example, by controlling or starting / stopping the compressor's rotational speed. After the refrigerant pressure in the heat exchanger reaches the desired value, the opening of the expansion valve may be adjusted to maintain that refrigerant pressure.

[0069] In any of the first to third embodiments, the control device for an outdoor unit according to the fourth aspect of this disclosure controls the temperature of the heat exchanger so that the heat transfer medium flowing through the heat exchanger does not freeze.

[0070] If the expansion valve is fully closed and the cooling mode is operated, the pressure in the heat transfer fluid heat exchanger will drop, causing the circulating heat transfer fluid to freeze, which may lead to damage in some cases. Therefore, it was decided to control the temperature of the heat transfer fluid heat exchanger to prevent the heat transfer fluid from freezing. The temperature of the heat transfer fluid heat exchanger is controlled, for example, by controlling the rotation speed of the compressor or by starting and stopping it.

[0071] In the fifth aspect of the present disclosure, the control device for an outdoor unit, in any of the first to fourth aspects, reduces the discharge flow rate of the heat transfer pump (55) that circulates the heat transfer medium through the heat transfer circuit when it detects a leak of refrigerant into the heat transfer circuit.

[0072] When a refrigerant leak into the heat transfer circuit is detected, the discharge flow rate of the heat transfer pump that circulates the heat transfer fluid through the circuit is reduced. This reduces the amount of refrigerant supplied to the heat utilization destination. Furthermore, if a gas separator is provided in the heat transfer circuit, reducing the flow rate of the heat transfer fluid can improve the refrigerant separation efficiency. The heat transfer pump will maintain a discharge flow rate above a predetermined level to prevent the heat transfer fluid from freezing in the heat transfer fluid heat exchanger. Therefore, the heat transfer pump will be controlled to prevent it from stopping.

[0073] An outdoor unit according to a first aspect of this disclosure includes a compressor for compressing a refrigerant, a refrigerant circuit through which the refrigerant discharged from the compressor circulates, an outdoor heat exchanger provided in the refrigerant circuit for exchanging heat between the refrigerant and outside air, a heat exchanger provided in the refrigerant circuit for exchanging heat between the refrigerant and a liquid heat transfer medium, an expansion valve provided in the refrigerant circuit for expanding the refrigerant, a switching valve for switching the refrigerant discharged from the compressor to flow to the outdoor heat exchanger or the heat exchanger, a heat transfer medium circuit for sending the heat transfer medium that has been heat-exchanged in the heat exchanger to a heat utilization destination, and an outdoor unit control device as described in any of the above.

[0074] A heat pump system according to a first aspect of this disclosure comprises the above-mentioned outdoor unit and a heat utilization unit connected to the outdoor unit.

[0075] An outdoor unit control method according to a first aspect of this disclosure includes: a compressor for compressing a refrigerant; a refrigerant circuit through which the refrigerant discharged from the compressor circulates; an outdoor heat exchanger provided in the refrigerant circuit for exchanging heat between the refrigerant and outside air; a heat exchanger provided in the refrigerant circuit for exchanging heat between the refrigerant and a liquid heat transfer medium; an expansion valve provided in the refrigerant circuit for expanding the refrigerant; a switching valve for switching the flow of the refrigerant discharged from the compressor to the outdoor heat exchanger or the heat exchanger; and heat exchange in the heat exchanger. An outdoor unit control method for controlling an outdoor unit comprising a heat transfer circuit that sends a heated heat transfer medium to a heat utilization destination, comprising: a cooling mode in which the switching valve is switched to operate the heat transfer medium heat exchanger as an evaporator and the outdoor heat exchanger as a condenser; and a heating mode in which the switching valve is switched to operate the heat transfer medium heat exchanger as a condenser and the outdoor heat exchanger as an evaporator, wherein when a leak of refrigerant into the heat transfer circuit is detected, the system is switched to the cooling mode and the expansion valve is fully closed.

[0076] 1 Outdoor unit 3 Housing 4 Base 4a Base legs 4b Flat plate section 5 Fan room 7 Machine room 9 Partition wall 11 Fan opening 13 Sub-base 15 Sub-base support member 17 Compressor 17a Compressor legs 19 Water heat exchanger 21 Gas separator 21a Discharge section 21b Water relief outlet 23 Control box 25 Water supply piping 26 Water return piping 28 Accumulator 29 Suction pressure sensor 30 Outdoor heat exchanger 34 Refrigerant discharge hole 40 Mesh 42 Refrigerant detection sensor 45 Expansion valve 47 Discharge pipe 49 Four-way valve (switching valve) 51 Liquid refrigerant piping 53 Liquid pipe temperature sensor 55 Water pump (heat transfer pump) 57 Water inlet temperature sensor 59 Water outlet temperature sensor C Refrigerant circuit W Water circuit (heat medium circuit)

Claims

1. A control device for an outdoor unit comprising: a compressor for compressing a refrigerant; a refrigerant circuit through which the refrigerant discharged from the compressor circulates; an outdoor heat exchanger provided in the refrigerant circuit for heat exchange between the refrigerant and outside air; a heat transfer medium heat exchanger provided in the refrigerant circuit for heat exchange between the refrigerant and a liquid heat transfer medium; an expansion valve provided in the refrigerant circuit for expanding the refrigerant; a switching valve for switching the refrigerant discharged from the compressor to flow to the outdoor heat exchanger or the heat transfer medium heat exchanger; and a heat transfer medium circuit for sending the heat transfer medium, which has been heat-exchanged in the heat transfer medium heat exchanger, to a heat utilization destination, wherein the control device has a cooling mode in which the switching valve is switched to operate the heat transfer medium heat exchanger as an evaporator and the outdoor heat exchanger as a condenser; and a heating mode in which the switching valve is switched to operate the heat transfer medium heat exchanger as a condenser and the outdoor heat exchanger as an evaporator. A control device for an outdoor unit that, upon detecting a refrigerant leak into the heat transfer medium circuit, switches to the cooling mode and completely closes the expansion valve.

2. The control device for an outdoor unit according to claim 1, comprising: a gas separator provided in the heat transfer medium circuit for separating gaseous refrigerant from the heat transfer medium; and a refrigerant detection sensor capable of detecting the refrigerant separated from the gas separator, wherein the refrigerant detection sensor detects leakage of refrigerant into the heat transfer medium circuit.

3. The control device for an outdoor unit according to claim 1 or 2, wherein the refrigerant pressure of the heat exchanger is controlled to approach the heat exchanger pressure of the heat medium.

4. The control device for an outdoor unit according to claim 1 or 2, which controls the temperature of the heat exchanger so that the heat transfer medium flowing through the heat exchanger does not freeze.

5. The control device for an outdoor unit according to claim 1 or 2, wherein when a leak of refrigerant into the heat transfer circuit is detected, the discharge flow rate of the heat transfer pump that circulates the heat transfer medium through the heat transfer circuit is reduced.

6. An outdoor unit comprising: a compressor for compressing a refrigerant; a refrigerant circuit through which the refrigerant discharged from the compressor circulates; an outdoor heat exchanger provided in the refrigerant circuit for exchanging heat between the refrigerant and outside air; a heat exchanger provided in the refrigerant circuit for exchanging heat between the refrigerant and a liquid heat transfer medium; an expansion valve provided in the refrigerant circuit for expanding the refrigerant; a switching valve for switching the flow of the refrigerant discharged from the compressor to the outdoor heat exchanger or the heat exchanger; a heat transfer medium circuit for sending the heat transfer medium, which has undergone heat exchange in the heat exchanger, to a heat utilization destination; and an outdoor unit control device as described in claim 1 or 2.

7. A heat pump device comprising: an outdoor unit as described in claim 6; and a heat utilization unit connected to the outdoor unit.

8. An outdoor unit control method for controlling an outdoor unit comprising: a compressor for compressing a refrigerant; a refrigerant circuit through which the refrigerant discharged from the compressor circulates; an outdoor heat exchanger provided in the refrigerant circuit for exchanging heat between the refrigerant and outside air; a heat transfer medium heat exchanger provided in the refrigerant circuit for exchanging heat between the refrigerant and a liquid heat transfer medium; an expansion valve provided in the refrigerant circuit for expanding the refrigerant; a switching valve for switching the refrigerant discharged from the compressor to flow to the outdoor heat exchanger or the heat transfer medium heat exchanger; and a heat transfer medium circuit for sending the heat transfer medium, which has been heat-exchanged in the heat transfer medium heat exchanger, to a heat utilization destination, wherein the method includes: a cooling mode in which the switching valve is switched to operate the heat transfer medium heat exchanger as an evaporator and the outdoor heat exchanger as a condenser; and a heating mode in which the switching valve is switched to operate the heat transfer medium heat exchanger as a condenser and the outdoor heat exchanger as an evaporator. An outdoor unit control method that, upon detecting a leak of refrigerant into the heat transfer medium circuit, switches to the cooling mode and completely closes the expansion valve.

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