Temperature control system

Abstract

There are times when water is not discharged depending on the outdoor temperature conditions when a water-draining means of a heat exchanger is manually opened when there is a risk of freezing. This temperature control system (1) sends temperature-adjusted water to a first water pipe (201), which is a water pipe on the use side. The temperature control system (1) is provided with a first unit (400). The first unit (400) has: a refrigerant circuit (100) through which a highly flammable refrigerant circulates; a second water pipe (202); and a first heat exchanger (120). The second water pipe (202) is a water pipe on the heat source side connected to the first water pipe (201). The first heat exchanger (120) exchanges heat between water and the refrigerant. The first unit (400) also has an automatic on-off valve (230) that automatically discharges the water in the first heat exchanger (120) at low temperatures.

Description

Temperature Control System

[0001] Regarding temperature control systems.

[0002] A heat pump air conditioner is known that includes a refrigerant circuit using a flammable HC refrigerant, a water circulation circuit with an indoor heat exchanger, and a plate heat exchanger that exchanges heat between the refrigerant circuit and the water circulation circuit. In such a heat pump air conditioner, if it is used in an environment where the outdoor temperature meets certain conditions, the plate heat exchanger may freeze and malfunction.

[0003] Patent Document 1 (Japanese Patent Laid-Open Publication No. 2001-201107) discloses a heat pump device in which, when there is a risk of the plate heat exchanger freezing, water is discharged from the plate heat exchanger and the water circulation circuit by manually opening a water draining means installed in the water circulation circuit.

[0004] When the draining means of the heat exchanger is manually opened when there is a risk of the heat exchanger freezing, depending on the outdoor temperature conditions, the water around the draining means may already be frozen, and the water may not be released.

[0005] A temperature control system according to a first aspect is a temperature control system that sends temperature-controlled water to a first water pipe, which is a user-side water pipe, and includes a first unit. The first unit has a refrigerant circuit through which a highly flammable refrigerant circulates, a second water pipe, and a first heat exchanger. The second water pipe is a heat source-side water pipe connected to the first water pipe. The first heat exchanger exchanges heat between the water and the refrigerant. The first unit further includes an automatic on-off valve that automatically releases water from the first heat exchanger when the temperature is low.

[0006] In this temperature control system, if there is a risk of the first heat exchanger freezing, the water inside the first heat exchanger is automatically released, thereby preventing a situation in which the water is not released when there is a risk of the first heat exchanger freezing.

[0007] A temperature control system of a second aspect is a temperature control system of the first aspect, wherein the automatic opening / closing valve automatically opens when the temperature of the water flowing through the first heat exchanger falls below a first threshold value, and automatically closes when the temperature of the water flowing through the first heat exchanger exceeds a second threshold value that is higher than the first threshold value.

[0008] In this temperature control system, the automatic on-off valve senses the water temperature and opens and closes automatically, preventing the water from not being discharged if there is a risk of the first heat exchanger freezing.

[0009] A temperature regulation system according to a third aspect is the temperature regulation system according to the first or second aspect, wherein the automatic on-off valve is a mechanical on-off valve whose opening degree changes in accordance with the temperature of the water flowing through the first heat exchanger.

[0010] In this temperature control system, the automatic on-off valve is a mechanical valve that senses the water temperature and opens and closes automatically, so no special control is required, which helps keep costs down.

[0011] A fourth aspect of the present invention is a temperature control system according to any one of the first to third aspects, wherein the first unit further includes a casing that houses the refrigerant circuit, the second water pipe, and the first heat exchanger. The automatic on-off valve is disposed in the casing.

[0012] This temperature control system can prevent the automatic on-off valve from being directly exposed to snow, wind, and rain, thereby preventing the automatic on-off valve from opening and closing accidentally due to environmental conditions outside the automatic on-off valve, and preventing the automatic on-off valve from freezing.

[0013] A fifth aspect of the present invention relates to a temperature control system according to any one of the first to fourth aspects, wherein the first unit further includes a second heat exchanger that exchanges heat between the refrigerant and outdoor air. The temperature control system further includes a control unit. The control unit controls a reverse cycle defrosting operation that melts frost that has adhered to the second heat exchanger. The control unit stops the reverse cycle defrosting operation when the temperature of the water flowing through the first heat exchanger falls below a third threshold during the reverse cycle defrosting operation.

[0014] In this temperature control system, the reverse cycle defrosting operation is stopped based on the detected water temperature, thereby preventing the first heat exchanger from freezing and the automatic on-off valve from opening during the reverse cycle defrosting operation.

[0015] A sixth aspect of the present invention relates to the temperature control system of the fourth aspect, wherein the casing has a bottom plate. The bottom plate has an opening that leads to the outside of the casing. Water in the first heat exchanger that is released from the automatic on-off valve is discharged to the outside of the casing through the opening.

[0016] This temperature control system can prevent water from accumulating inside the casing.

[0017] A seventh aspect of the present invention is a temperature control system according to the sixth aspect, wherein the first unit further includes a second heat exchanger for exchanging heat between the refrigerant and the outdoor air. Drain water from the second heat exchanger is discharged to the outside of the casing through an opening.

[0018] In this temperature control system, the opening in the bottom plate serves both as a drain outlet for water in the first heat exchanger and as a drain outlet for drain water from the second heat exchanger, which reduces the number of openings and maintains the strength of the bottom plate.

[0019] It is a schematic configuration diagram of a temperature adjustment system. It is a block diagram of a control unit. It is a perspective view of a first unit seen from the bottom (lower) side. It is a flowchart showing the operation of the control unit. It is a flowchart showing the operation of the control unit according to Modification D.

[0020] <First Embodiment> (1) Overall Configuration FIG. 1 is a schematic diagram of a temperature adjustment system 1 according to one embodiment. The temperature adjustment system 1 is a refrigeration cycle device that sends temperature-adjusted water to a first water pipe 201, which is a user-side water pipe. The temperature adjustment system 1 includes a first unit 400 and a control unit 300. The first unit 400 includes a refrigerant circuit 100, a second water pipe 202, which is a heat source-side water pipe connected to the first water pipe 201, an automatic on-off valve 230, and a casing 410. The first water pipe 201 and the second water pipe 202 are connected via connectors 200a and 200b to form a water circuit 200. The casing 410 houses the refrigerant circuit 100, the second water pipe 202, and the first heat exchanger 120.

[0021] The temperature adjustment system 1 performs cooling and heating operations. More specifically, the temperature adjustment system 1 causes the refrigerant filled in the refrigerant circuit 100 to perform a refrigeration cycle, heats or cools the water filled in the water circuit 200, and uses this water to perform cooling and heating operations in a user-side space to be air-conditioned (not shown).

[0022] (2) Detailed Configuration (2-1) Refrigerant Circuit The refrigerant circuit 100 includes a compressor 110, a first heat exchanger 120, a second heat exchanger 130, a switching mechanism 140, and an expansion mechanism 150. The components of the refrigerant circuit 100 are connected by pipes. The refrigerant circuit 100 is filled with a highly flammable refrigerant. The highly flammable refrigerant is a refrigerant that has high flammability and is classified as highly flammable (A3) according to ISO 817. In this embodiment, the refrigerant is R290 (propane).

[0023] (2-1-1) Compressor The compressor 110 compresses a low-pressure refrigerant in the refrigeration cycle to a high-pressure refrigerant using a compression mechanism (not shown). The compressor 110 has a suction portion 110a and a discharge portion 110b.

[0024] The suction section 110a draws low-pressure refrigerant from the refrigerant circuit 100 and supplies it to the compression mechanism. The discharge section 110b discharges the refrigerant compressed to high pressure by the compression mechanism to the refrigerant circuit 100. The compression capacity of the compressor 110 is controlled by the control section 300.

[0025] (2-1-2) First Heat Exchanger The first heat exchanger 120 exchanges heat between the refrigerant filling the refrigerant circuit 100 and the water filling the water circuit 200. The first heat exchanger 120 has a refrigerant flow path 121 and a water flow path 122.

[0026] The refrigerant flowing through the refrigerant circuit 100 passes through the refrigerant flow path 121. The refrigerant flow path 121 has a first end 121a and a second end 121b. The first end 121a and the second end 121b function as an inlet and an outlet for the refrigerant to and from the refrigerant flow path 121.

[0027] Water flowing through the water circuit 200 passes through the water flow path 122. The refrigerant flow path 121 has a first end 122a and a second end 122b. The first end 122a functions as an outlet for water from the water flow path 122. The second end 122b functions as an inlet for water to the water flow path 122. A first temperature sensor 123 that detects the temperature of water flowing through the first end 122a and a second temperature sensor 124 that detects the temperature of water flowing through the second end 122b are disposed in the water flow path 122. The first temperature sensor 123 and the second temperature sensor 124 are, for example, thermistors.

[0028] Without limitation, the first heat exchanger 120 is a plate-type heat exchanger.

[0029] (2-1-3) Second Heat Exchanger The second heat exchanger 130 exchanges heat between the refrigerant filling the refrigerant circuit 100 and the air in the location where the second heat exchanger 130 is installed. The second heat exchanger 130 has a first end 130a and a second end 130b. The first end 130a and the second end 130b function as an inlet for the refrigerant to the second heat exchanger 130 and an outlet for the refrigerant from the second heat exchanger 130. A third temperature sensor 131 is disposed in the second heat exchanger 130 to detect the temperature of the outside air that has passed through the second heat exchanger 130. The third temperature sensor 131 is, for example, a thermistor.

[0030] The second heat exchanger 130 is installed, for example, outside the space to be air-conditioned, such as outdoors. The second heat exchanger 130 is, but is not limited to, a microchannel type heat exchanger.

[0031] (2-1-4) Switching Mechanism The switching mechanism 140 switches the direction of refrigerant flow in the refrigerant circuit 100 between two states. The switching mechanism 140 is a four-way switching valve. The switching mechanism 140 has a first port P1, a second port P2, a third port P3, and a fourth port P4.

[0032] The first port P1 is connected to the discharge portion 110b of the compressor 110. The second port P2 is connected to the second end 130b of the second heat exchanger 130. The third port P3 is connected to the suction portion 110a of the compressor 110. The fourth port P4 is connected to the second end 121b of the refrigerant flow path 121 of the first heat exchanger 120.

[0033] The switching mechanism 140 switches between a first state (a state indicated by a solid line in FIG. 1 ) and a second state (a state indicated by a dashed line in FIG. 1 ). In the first state, the switching mechanism 140 connects the first port P1 to the second port P2 and connects the third port P3 to the fourth port P4. In the second state, the switching mechanism 140 connects the first port P1 to the fourth port P4 and connects the second port P2 to the third port P3. The state of the switching mechanism 140 is controlled between the first state and the second state by the control unit 300.

[0034] (2-1-5) Expansion Mechanism The expansion mechanism 150 reduces the pressure of the refrigerant flowing between the first end 130a of the second heat exchanger 130 and the first end 121a of the refrigerant flow path 121 of the first heat exchanger 120. One end of the expansion mechanism 150 is connected to the first end 130a of the second heat exchanger 130, and the other end is connected to the first end 121a of the refrigerant flow path 121 of the first heat exchanger 120.

[0035] Although not limited to this, the expansion mechanism 150 is an electric expansion valve. The opening degree of the expansion mechanism 150 is controlled by the control unit 300.

[0036] (2-2) Water Circuit The water circuit 200 has a pump 210, a third heat exchanger 220, and an automatic on-off valve 230. The water circuit 200 is filled with water, which is a heat medium. The water circuit 200 includes a first water pipe 201, which is a water pipe on the user side, and a second water pipe 202, which is a water pipe on the heat source side connected to the first water pipe 201. The first water pipe 201 and the second water pipe 202 are connected via connectors 200a and 200b. The various parts of the water circuit 200 are connected by pipes.

[0037] (2-2-1) Pump The pump 210 circulates the water filled in the water circuit 200 through the water circuit 200. The pump 210 has a suction portion 210a and a discharge portion 210b.

[0038] The pump 210 applies a predetermined pressure to the water drawn into the water circuit 200 from the intake port 210a, and discharges the water from the discharge port 210b back into the water circuit 200.

[0039] The suction port 210a is connected to a second end 220b (described later) of the third heat exchanger 220. The discharge port 210b is connected to the connection port 200b. The pump 210 is controlled by the control unit 300.

[0040] (2-2-2) Third Heat Exchanger The third heat exchanger 220 is installed in the space to be air-conditioned, and exchanges heat between the water filled in the water circuit 200 and the air in the location where the third heat exchanger 220 is installed. The third heat exchanger 220 has a first end 220a and a second end 220b. The first end 220a functions as an inlet for water flowing into the third heat exchanger 220. The second end 220b functions as an outlet for water flowing out of the third heat exchanger 220. The first end 220a is connected to the connection portion 200a. The second end 220b is connected to the suction portion 210a of the pump 210.

[0041] (2-2-3) Automatic On-Off Valve The automatic on-off valve 230 is provided in the water pipe 203 branching off from the water circuit 200, downstream of the first end 122a in the water circuit 200. The automatic on-off valve 230 is also disposed inside the casing 410.

[0042] The automatic on-off valve 230 is a mechanical on-off valve whose opening changes depending on the temperature of the water flowing through the first heat exchanger 120, and automatically releases the water from the first heat exchanger 120 when the temperature is low. The temperature of the water flowing through the first heat exchanger 120 is the temperature of the water flowing through the second water pipe 202 at the location where the automatic on-off valve 230 is located. Here, because the first end 122a and the automatic on-off valve 230 are connected by a short pipe, there is almost no temperature difference. Therefore, the temperature of the water flowing through the first heat exchanger 120 is also the temperature of the water flowing out from the first end 122a, which functions as a water outlet from the water flow path 122.

[0043] The automatic on-off valve 230 automatically opens when the temperature of the water flowing through the first heat exchanger 120 falls below a first threshold, and automatically closes when the temperature of the water flowing through the first heat exchanger 120 exceeds a second threshold that is higher than the first threshold. In this embodiment, the first threshold is 4°C, and the second threshold is 5°C. In this case, the automatic on-off valve 230 begins to open when the temperature of the water flowing through the first heat exchanger 120 is 4°C, and becomes fully open when the temperature is below 3°C. Furthermore, the automatic on-off valve 230 becomes fully closed when the temperature of the water flowing through the first heat exchanger 120 exceeds 5°C.

[0044] (2-3) Casing Figure 3 is a perspective view of the first unit 400 as seen from the bottom (lower) side. In the following description, unless otherwise specified, "upper," "lower," "left," "right," "front," and "rear" refer to the directions shown in Figure 3. These refer to the directions when the first unit 400 is installed and in normal use. In this embodiment, the up-down direction is the vertical direction.

[0045] The first unit 400 has a casing 410 in the shape of a substantially rectangular parallelepiped box. The casing 410 accommodates the refrigerant circuit 100, the second water pipe 202, and the first heat exchanger 120. The automatic on-off valve 230 is disposed inside the casing 410.

[0046] The casing 410 has a bottom plate 420, which is a horizontally elongated, approximately rectangular plate-like member that forms the bottom (lower) portion of the casing 410. The bottom plate 420 is provided with an opening 430 that leads to the outside of the casing 410. The water discharged from the automatic on-off valve 230 is configured to be discharged to the outside of the casing 410 through the opening 430. Drain water generated in the second heat exchanger 130 is also discharged to the outside of the casing 410 through the opening 430. In other words, the opening 430 of the bottom plate 420 serves both as a drain port for the water discharged from the automatic on-off valve 230 and as a discharge port for the drain water generated in the second heat exchanger 130.

[0047] (2-4) Control Unit FIG. 2 is a block diagram of the control unit 300. The control unit 300 is electrically connected to the compressor 110, the switching mechanism 140, the expansion mechanism 150, the pump 210, the first temperature sensor 123, the second temperature sensor 124, and the third temperature sensor 131 so as to be able to send and receive signals. The control unit 300 acquires information such as the operating state of each device and the measured values ​​of each sensor. Based on the acquired information, the control unit 300 controls each device in the refrigerant circuit 100 to cause the refrigerant circuit 100 to perform a refrigeration cycle, thereby realizing cooling operation and heating operation in the space to be air-conditioned.

[0048] The control unit 300 is realized by a computer. The control unit 300 includes a control and arithmetic unit and a storage device (both not shown). The control and arithmetic unit can be a processor such as a CPU or a GPU. The control and arithmetic unit reads a program stored in the storage device and performs predetermined arithmetic processing in accordance with the program. Furthermore, the control and arithmetic unit can write the results of calculations to the storage device and read information stored in the storage device in accordance with the program.

[0049] (3) Overall Operation The control unit 300 controls each device in the cooling operation, heating operation, and reverse cycle defrosting operation as described below.

[0050] (3-1) Cooling Operation When the temperature adjustment system 1 is instructed to perform cooling operation, the control unit 300 causes the compressor 110 and the pump 210 to start operating, sets the switching mechanism 140 to the first state, and controls the opening degree of the expansion mechanism 150.

[0051] (3-1-1) Refrigerant Circuit When the compressor 110 starts operation, low-pressure gas refrigerant in the refrigeration cycle is drawn in through the suction port 110a, compressed to the high-pressure state in the refrigeration cycle, and then discharged as gas refrigerant from the discharge port 110b.

[0052] The high-pressure gas refrigerant flowing out from the discharge port 110b passes through the switching mechanism 140, in this order, via the first port P1 and the second port P2, and flows into the second heat exchanger 130 from the second end 130b. The high-pressure gas refrigerant that has flowed into the second heat exchanger 130 exchanges heat with the air in the installation location of the second heat exchanger 130, condenses, and becomes high-pressure liquid refrigerant, which flows out from the first end 130a. In other words, the second heat exchanger 130 functions as a radiator.

[0053] The high-pressure liquid refrigerant flowing out of the second heat exchanger 130 passes through the expansion mechanism 150 and flows from the first end 121a into the refrigerant flow path 121 of the first heat exchanger 120. The refrigerant that has passed through the expansion mechanism 150 is decompressed to a low pressure and becomes a gas-liquid two-phase refrigerant.

[0054] The low-pressure refrigerant that has flowed into the refrigerant flow path 121 exchanges heat with the water flowing through the water flow path 122 and evaporates, becoming a low-pressure gas refrigerant that flows out from the second end 121b. In other words, the refrigerant flow path 121 of the first heat exchanger 120 functions as an evaporator.

[0055] The low-pressure gas refrigerant flowing out of the first heat exchanger 120 passes through the switching mechanism 140 via the fourth port P4 and the third port P3 in this order, and is again drawn into the compressor 110 via the suction section 110a.

[0056] (3-1-2) Water Circuit When the pump 210 starts operating, the water filled in the water circuit 200 is drawn in through the intake port 210a and then discharged from the discharge port 210b.

[0057] The water flowing out from the discharge port 210b flows into the water flow path 122 of the first heat exchanger 120 from the second end 122b. The water that has flowed into the water flow path 122 exchanges heat with (is cooled by) the low-pressure refrigerant flowing through the refrigerant flow path 121, and then flows out from the first end 122a.

[0058] The water flowing out of the first heat exchanger 120 flows into the third heat exchanger 220 from the first end 220a. The water flowing into the third heat exchanger 220 exchanges heat with the air in the location where the third heat exchanger 220 is installed. This cools the air in the space to be air-conditioned.

[0059] The water that has exchanged heat with the air in the location where the third heat exchanger 220 is installed flows out from the second end 220b and is then sucked into the pump 210 again from the suction port 210a.

[0060] (3-2) Heating Operation When the temperature adjustment system 1 is instructed to perform heating operation, the control unit 300 causes the compressor 110 and the pump 210 to start operating, sets the switching mechanism 140 to the second state, and controls the opening degree of the expansion mechanism 150.

[0061] (3-2-1) Refrigerant Circuit When the compressor 110 starts operation, low-pressure gas refrigerant in the refrigeration cycle is drawn in through the suction port 110a, compressed to the high-pressure state in the refrigeration cycle, and then discharged as gas refrigerant from the discharge port 110b.

[0062] The high-pressure gas refrigerant flowing out from the discharge port 110b passes through the switching mechanism 140, in this order, via the first port P1 and the fourth port P4, and flows into the refrigerant flow path 121 of the first heat exchanger 120 from the second end 121b. The high-pressure gas refrigerant that has flowed into the first heat exchanger 120 exchanges heat with the water flowing through the water flow path 122, condenses, and becomes high-pressure liquid refrigerant, which flows out from the first end 121a. In other words, the refrigerant flow path 121 of the first heat exchanger 120 functions as a radiator.

[0063] The high-pressure liquid refrigerant flowing out of the first heat exchanger 120 passes through the expansion mechanism 150 and flows into the second heat exchanger 130 from the first end 130a. The refrigerant that has passed through the expansion mechanism 150 is reduced in pressure to a low level and becomes a gas-liquid two-phase refrigerant.

[0064] The low-pressure refrigerant that flows into the second heat exchanger 130 exchanges heat with the air in the location where the second heat exchanger 130 is installed, evaporating, and becomes low-pressure gas refrigerant, which flows out from the second end 130b. In other words, the second heat exchanger 130 functions as an evaporator.

[0065] The low-pressure gas refrigerant flowing out of the second heat exchanger 130 passes through the switching mechanism 140 via the second port P2 and the third port P3 in this order, and is again drawn into the compressor 110 via the suction section 110a.

[0066] (3-2-2) Water Circuit When the pump 210 starts operating, the refrigerant filled in the water circuit 200 is drawn in through the suction port 210a and then discharged from the discharge port 210b.

[0067] The water flowing out from the discharge port 210b flows into the water flow path 122 of the first heat exchanger 120 from the second end 122b. The water that has flowed into the water flow path 122 exchanges heat with (is heated by) the high-pressure refrigerant flowing through the refrigerant flow path 121, and then flows out from the first end 122a.

[0068] The water flowing out of the first heat exchanger 120 flows into the third heat exchanger 220 from the first end 220a. The water flowing into the third heat exchanger 220 exchanges heat with the air in the location where the third heat exchanger 220 is installed. This heats the air in the space to be air-conditioned.

[0069] The water that has exchanged heat with the air in the location where the third heat exchanger 220 is installed flows out from the second end 220b and is then sucked into the pump 210 again from the suction port 210a.

[0070] (3-3) Reverse Cycle Defrosting Operation The reverse cycle defrosting operation is an operation for removing frost that has adhered to the second heat exchanger 130. The flow of the reverse cycle defrosting operation by the control unit 300 will be described with reference to FIG.

[0071] (3-3-1) Start of Reverse Cycle Defrosting Operation During heating operation, the control unit 300 acquires the temperature detected by the third temperature sensor 131 at predetermined intervals (step S11). If the acquired temperature is less than a predetermined value, the control unit 300 determines that frost has formed on the second heat exchanger 130 (step S12).

[0072] When the control unit 300 determines that frost has formed on the second heat exchanger 130, it stops the operation of the compressor 110 to stop the heating operation (step S13). In addition, the control unit 300 reduces the output of the pump 210 or stops the operation of the pump 210.

[0073] In step S12, if the control unit 300 determines that no frost has formed on the second heat exchanger 130, the process returns to step S11, and the control unit 300 acquires the temperature detected by the third temperature sensor 131 at predetermined intervals.

[0074] If it is determined in step S12 that frost has formed on the second heat exchanger 130, the control unit 300 switches the flow direction of the refrigerant in the refrigerant circuit 100 to the same direction as during cooling operation, and starts reverse cycle defrosting operation (step S14). In other words, the control unit 300 starts operation of the compressor 110, sets the switching mechanism 140 to the first state, and controls the opening degree of the expansion mechanism 150. The control unit 300 also controls operation of the pump 210.

[0075] When the compressor 110 starts operating, in the refrigerant circuit 100, low-pressure gas refrigerant in the refrigeration cycle is drawn in through the suction port 110a, compressed to the high-pressure state in the refrigeration cycle, and then discharged as gas refrigerant from the discharge port 110b. The high-pressure gas refrigerant flowing out from the discharge port 110b passes through the switching mechanism 140, in this order, via the first port P1 and the second port P2, and flows into the second heat exchanger 130 from the second end 130b. The high-pressure refrigerant flowing into the second heat exchanger 130 supplies heat to the second heat exchanger 130. This melts frost adhering to the second heat exchanger 130, defrosting the second heat exchanger 130.

[0076] The high-pressure refrigerant flowing out of the second heat exchanger 130 passes through the expansion mechanism 150 and flows from the first end 121a into the refrigerant flow path 121 of the first heat exchanger 120. The refrigerant that has passed through the expansion mechanism 150 is reduced in pressure to a low level and becomes a gas-liquid two-phase refrigerant. The low-pressure refrigerant that has flowed into the refrigerant flow path 121 exchanges heat with water flowing through the water flow path 122, becomes a low-pressure gas refrigerant, and flows out from the second end 121b.

[0077] The low-pressure gas refrigerant flowing out of the first heat exchanger 120 passes through the switching mechanism 140 via the fourth port P4 and the third port P3 in this order, and is again drawn into the compressor 110 via the suction section 110a.

[0078] In the water circuit 200, the water filled in the water circuit 200 flows into the water flow path 122 of the first heat exchanger 120 from the second end 122b. The water that has flowed into the water flow path 122 exchanges heat with (is cooled by) the low-pressure refrigerant flowing through the refrigerant flow path 121, and then flows out from the first end 122a. As a result, the water in the water flow path 122 is cooled.

[0079] (3-3-2) Stopping the Reverse Cycle Defrosting Operation If the temperature of the water flowing through the water flow path 122 drops too much due to the reverse cycle defrosting operation, the first heat exchanger 120 may freeze.

[0080] Therefore, the control unit 300 acquires the temperatures detected by the first temperature sensor 123 and the second temperature sensor 124 at predetermined intervals during the reverse cycle defrosting operation (step S15). If either of the detected temperatures is below a third threshold, the control unit 300 determines that there is a possibility that the first heat exchanger 120 will freeze if the reverse cycle defrosting operation is continued (step S16). In this embodiment, the third threshold is 6°C.

[0081] If the control unit 300 determines that there is a possibility that the first heat exchanger 120 will freeze, the control unit 300 stops the reverse cycle defrosting operation and restarts the heating operation (steps S17 and S18). In other words, the control unit 300 stops the operation of the compressor 110 to stop the reverse cycle defrosting operation, then starts the operation of the compressor 110 and the pump 210, sets the switching mechanism 140 to the second state, and controls the opening degree of the expansion mechanism 150.

[0082] In step S16, if the control unit 300 determines that there is no possibility of the first heat exchanger 120 freezing, it returns to step S15 and acquires the temperatures detected by the first temperature sensor 123 and the second temperature sensor 124 at predetermined intervals.

[0083] As described above, the automatic on-off valve 230 begins to open when the temperature of the water flowing through the first heat exchanger 120 is 4°C and fully opens when the temperature is below 3°C. The automatic on-off valve 230 fully closes when the temperature of the water flowing through the first heat exchanger 120 exceeds 5°C. The temperature of the water flowing through the first heat exchanger 120 is the temperature of the water flowing out from the first end 122a, which functions as a water outlet from the water flow path 122, and is the temperature of the water flowing through the second water pipe 202 at the location where the automatic on-off valve 230 is located. The control unit 300 stops the reverse cycle defrosting operation when the temperature detected by the first temperature sensor 123 or the second temperature sensor 124 falls below 6°C. During the reverse cycle defrosting operation, the temperature of the water flowing out from the first end 122a is approximately the same as the temperature detected by the first temperature sensor 123 but lower than the temperature detected by the second temperature sensor 124.

[0084] Therefore, the control unit 300 stops the reverse cycle defrost operation before the automatic on-off valve 230 starts to open due to a drop in the temperature of the water flowing through the water flow path 122. As a result, the water filled in the water circuit 200 can be prevented from being released from the automatic on-off valve 230.

[0085] When the heating operation is resumed, as described above, the high-pressure gas refrigerant flowing out from the discharge port 110b flows into the refrigerant flow path 121 of the first heat exchanger 120 from the second end 121b. The water that has flowed into the water flow path 122 exchanges heat with the high-pressure refrigerant flowing through the refrigerant flow path 121 (is heated), and flows out from the first end 122a. As a result, the water in the water flow path 122 is heated.

[0086] Therefore, the temperature of the water flowing through the water flow path 122 increases, and the water filled in the water circuit 200 can be prevented from being released from the automatic on-off valve 230.

[0087] (4) Features (4-1) The temperature adjustment system 1 according to this embodiment is a temperature adjustment system 1 that sends temperature-adjusted water to a first water pipe 201, which is a water pipe on the user side. The temperature adjustment system 1 includes a first unit 400. The first unit 400 includes a refrigerant circuit 100 in which a highly flammable refrigerant circulates, a second water pipe 202, and a first heat exchanger 120. The second water pipe 202 is a water pipe on the heat source side that is connected to the first water pipe 201. The first heat exchanger 120 exchanges heat between the water and the refrigerant. The first unit 400 further includes an automatic on-off valve 230 that automatically releases water from the first heat exchanger 120 when the temperature is low.

[0088] In this temperature adjustment system 1, if there is a risk of the first heat exchanger 120 freezing, the water in the first heat exchanger 120 is automatically released. This prevents a situation in which water is not released when there is a risk of the first heat exchanger 120 freezing. As a result, it is possible to prevent the first heat exchanger 120 from failing due to freezing. Therefore, it is possible to prevent the highly flammable refrigerant from leaking due to a failure of the first heat exchanger 120 and the leaked highly flammable refrigerant from circulating through the first water piping 201 on the user side.

[0089] (4-2) In the temperature control system 1 according to this embodiment, the automatic on-off valve 230 automatically opens when the temperature of the water flowing through the first heat exchanger 120 falls below a first threshold, and automatically closes when the temperature of the water flowing through the first heat exchanger 120 exceeds a second threshold that is higher than the first threshold.

[0090] In this temperature adjustment system 1, the automatic on-off valve 230 senses the water temperature and automatically opens and closes, thereby preventing a situation in which water is not discharged when there is a risk of the first heat exchanger 120 freezing. As a result, it is possible to prevent the first heat exchanger 120 from failing due to freezing. Therefore, it is possible to prevent the highly flammable refrigerant from leaking due to a failure of the first heat exchanger 120 and the leaked highly flammable refrigerant from circulating through the first water piping 201 on the user side.

[0091] (4-3) In the temperature adjustment system 1 according to this embodiment, the automatic on-off valve 230 is a mechanical on-off valve whose opening degree changes depending on the temperature of the water flowing through the first heat exchanger 120 .

[0092] This temperature adjustment system 1 does not require any special control, which reduces costs.

[0093] (4-4) In the temperature adjustment system 1 according to this embodiment, the first unit 400 further includes a casing 410 that houses the refrigerant circuit 100, the second water pipe 202, and the first heat exchanger 120. The automatic on-off valve 230 is disposed in the casing 410.

[0094] In this temperature adjustment system 1, it is possible to prevent the automatic on-off valve 230 from being directly exposed to snow, wind, and rain. As a result, it is possible to prevent the automatic on-off valve 230 from opening and closing accidentally due to environmental conditions outside the automatic on-off valve 230, and to prevent the automatic on-off valve 230 from freezing.

[0095] (4-5) In the temperature adjustment system 1 according to this embodiment, the first unit 400 further includes a second heat exchanger 130 that exchanges heat between the refrigerant and the outdoor air. The temperature adjustment system 1 further includes a control unit 300. The control unit 300 controls a reverse cycle defrosting operation that melts frost that has adhered to the second heat exchanger 130. During the reverse cycle defrosting operation, the control unit 300 stops the reverse cycle defrosting operation when the temperature of the water flowing through the first heat exchanger 120 falls below a third threshold value.

[0096] In this temperature adjustment system 1, the reverse cycle defrosting operation is stopped based on the detected water temperature, thereby preventing the first heat exchanger 120 from freezing and the automatic on-off valve 230 from opening during the reverse cycle defrosting operation.

[0097] (4-6) In the temperature adjustment system 1 according to this embodiment, the casing 410 has a bottom plate 420. The bottom plate 420 has an opening 430 that leads to the outside of the casing 410. The water in the first heat exchanger 120 that is released from the automatic on-off valve 230 is discharged to the outside of the casing 410 through the opening 430.

[0098] In this temperature adjustment system 1, water can be prevented from accumulating inside the casing 410.

[0099] (4-7) In the temperature adjustment system 1 according to this embodiment, the first unit 400 further includes a second heat exchanger 130 that exchanges heat between the refrigerant and the outdoor air. Drain water from the second heat exchanger 130 is discharged to the outside of the casing 410 through an opening 430.

[0100] In this temperature adjustment system 1, the openings 430 in the bottom plate 420 serve both as drain ports for water in the first heat exchanger 120 and as outlets for drain water from the second heat exchanger 130. This allows the number of openings 430 to be reduced, thereby maintaining the strength of the bottom plate 420.

[0101] (5) Modifications The specific configuration of the embodiment of the present invention can be modified without departing from the spirit of the present invention. Modifications applicable to the embodiment of the present invention will be described below.

[0102] (5-1) Modification A In this embodiment, the automatic on-off valve 230 is provided in the water piping 203 branching off from the water circuit 200, downstream of the first end 122a in the water circuit 200. However, the automatic on-off valve 230 may also be provided upstream of the second end 122b in the water circuit 200.

[0103] In this case, the temperature of the water flowing through the first heat exchanger 120 is the temperature of the water flowing in from the second end 122b, which functions as a water inlet to the water flow path 122, and is the temperature of the water flowing through the second water piping 202 at the position where the automatic opening / closing valve 230 is located.

[0104] In the configuration according to this modification, when there is a risk of the first heat exchanger 120 freezing, the water filled in the water circuit 200 is released from the automatic on-off valve 230 before flowing into the first heat exchanger 120. This prevents the first heat exchanger 120 from failing due to freezing, prevents the highly flammable refrigerant from leaking due to a failure of the first heat exchanger 120, and prevents the leaked highly flammable refrigerant from circulating through the first water piping 201 on the user side.

[0105] (5-2) Modification B In this embodiment, during reverse cycle defrost operation, the control unit 300 acquires, at predetermined intervals, the temperatures detected by the first temperature sensor 123 and the second temperature sensor 124. However, the control unit 300 may acquire only the temperature detected by the first temperature sensor 123.

[0106] In this temperature adjustment system 1, the first heat exchanger 120 can be prevented from freezing and the automatic on-off valve 230 can be prevented from opening during the reverse cycle defrosting operation.

[0107] (5-3) Modification C In this embodiment, the control unit 300 determines that frost has formed on the second heat exchanger 130 when the temperature detected by the third temperature sensor 131 is below a predetermined value. However, the method for detecting frost is not limited to this. The control unit 300 may detect frost formation on the second heat exchanger 130, for example, using the temperature of the refrigerant flowing through the second heat exchanger 130 and the temperature of the air passing through the second heat exchanger 130.

[0108] (5-4) Modification D In this embodiment, the control unit 300 detects frost formation on the second heat exchanger 130 during heating operation. However, the control unit 300 may also detect frost formation on the second heat exchanger 130 while the temperature adjustment system 1 is not operating.

[0109] FIG. 5 is a diagram showing the flow of reverse cycle defrosting operation by the control unit 300 when the reverse cycle defrosting operation is performed during a shutdown.

[0110] The control unit 300 acquires the temperature detected by the third temperature sensor 131 at predetermined intervals while the operation is stopped (step S21). If the acquired temperature is less than a predetermined value, the control unit 300 determines that frost has formed on the second heat exchanger 130 (step S22).

[0111] If the control unit 300 determines that no frost has formed on the second heat exchanger 130, the control unit 300 returns to step S21 and acquires the temperature detected by the third temperature sensor 131 at predetermined intervals.

[0112] If it is determined in step S22 that frost has formed on the second heat exchanger 130, the control unit 300 switches the flow direction of the refrigerant in the refrigerant circuit 100 to the same direction as during cooling operation, and starts reverse cycle defrosting operation (step S23). In other words, the control unit 300 starts the operation of the compressor 110 and the pump 210, sets the switching mechanism 140 to the first state, and controls the opening degree of the expansion mechanism 150.

[0113] During the reverse cycle defrosting operation, the control unit 300 acquires the temperatures detected by the first temperature sensor 123 and the second temperature sensor 124 at predetermined intervals (step S24). If either of the detected temperatures is below the third threshold, the control unit 300 determines that continuing the reverse cycle defrosting operation may cause freezing of the first heat exchanger 120 (step S25).

[0114] If it is determined that there is a possibility that the first heat exchanger 120 will freeze, the control unit 300 stops the operation of the compressor 110 and stops the reverse cycle defrost operation (step S26).

[0115] In step S25, if the control unit 300 determines that there is no possibility of the first heat exchanger 120 freezing, it returns to step S24 and acquires the temperatures detected by the first temperature sensor 123 and the second temperature sensor 124 at predetermined intervals.

[0116] The control unit 300 may continue to operate the pump 210 for a predetermined period after stopping the reverse cycle defrost operation. By preventing water from accumulating in the water flow path 122 of the first heat exchanger 120, it is possible to prevent the first heat exchanger 120 from freezing.

[0117] In the configuration according to this modification, the control unit 300 stops the reverse cycle defrost operation before the automatic on-off valve 230 starts to open due to a drop in the temperature of the water flowing through the water flow path 122. As a result, the water filled in the water circuit 200 can be prevented from being released from the automatic on-off valve 230.

[0118] <Other Embodiments> Although the embodiments of the present disclosure have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the present disclosure as defined in the claims.

[0119] REFERENCE SIGNS LIST 1 Temperature control system 100 Refrigerant circuit 110 Compressor 120 First heat exchanger 121 Refrigerant flow path 122 Water flow path 130 Second heat exchanger 140 Switching mechanism 150 Expansion mechanism 200 Water circuit 201 First water pipe 202 Second water pipe 210 Pump 220 Third heat exchanger 230 Automatic on-off valve 300 Control unit 400 First unit 410 Casing 420 Bottom plate 430 Opening

[0120] Japanese Patent Application Laid-Open No. 2001-201107

Claims

1. A temperature control system (1) that sends temperature-controlled water to a first water pipe (201) that is a user-side water pipe, a first unit (400) having a refrigerant circuit (100) through which a highly flammable refrigerant circulates, a second water pipe (202) which is a water pipe on a heat source side connected to the first water pipe, and a first heat exchanger (120) which exchanges heat between the water and the refrigerant; Equipped with The first unit further includes an automatic on-off valve (230) for automatically releasing water from the first heat exchanger when the temperature is low. Temperature control system.

2. The automatic on-off valve automatically opens when the temperature of the water flowing through the first heat exchanger falls below a first threshold, and automatically closes when the temperature of the water flowing through the first heat exchanger exceeds a second threshold that is higher than the first threshold. The temperature control system according to claim 1 .

3. The automatic on-off valve is a mechanical on-off valve whose opening degree changes depending on the temperature of the water flowing through the first heat exchanger. The temperature control system according to claim 1 or 2.

4. The first unit further includes a casing (400) that houses the refrigerant circuit, the second water pipe, and the first heat exchanger, The automatic on-off valve is disposed in the casing. The temperature control system according to claim 1 or 2.

5. The first unit further includes a second heat exchanger (130) for exchanging heat between the refrigerant and outdoor air, a control unit (300) for controlling a reverse cycle defrosting operation for melting frost adhering to the second heat exchanger; Furthermore, The control unit stops the reverse cycle defrosting operation when the temperature of the water flowing through the first heat exchanger falls below a third threshold during the reverse cycle defrosting operation. The temperature control system according to claim 1 or 2.

6. The casing has a bottom plate (420), The bottom plate has an opening (430) that leads to the outside of the casing; The water in the first heat exchanger released from the automatic on-off valve is discharged to the outside of the casing through the opening. The temperature control system according to claim 4 .

7. The first unit further includes a second heat exchanger (130) for exchanging heat between the refrigerant and outdoor air, Drain water from the second heat exchanger is discharged to the outside of the casing through the opening. The temperature control system according to claim 6 .