Immersed liquid cooling energy storage battery system

Abstract

The utility model discloses an immersion type liquid cooling energy storage battery system, it includes: holding frame, a plurality of battery packs and refrigeration device, battery packs are installed in holding frame, each battery pack includes box body, a plurality of battery modules and ventilation device, box body is provided with liquid inlet interface and liquid return interface, the plurality of battery modules are arranged in the box body at interval, and the refrigeration device is arranged in the box body. The ventilation device is used for balancing air pressure inside and outside the battery pack; the refrigerating device is provided with a plurality of first connecting pipes and second connecting pipes which are communicated with the liquid inlet interface and the liquid return interface, the refrigerating device conveys the cooling liquid to each battery pack through the first connecting pipes and recycles the cooling liquid from each battery pack through the second connecting pipes, and the refrigerating device is used for controlling the temperature of the cooling liquid respectively. The immersed liquid-cooled energy storage battery system can provide an independent liquid-cooled circulation loop for a plurality of battery packs, so that the battery cells of the battery packs can meet the temperature uniformity requirement, the problem of overhigh air pressure of the battery packs is solved, and the occurrence of thermal runaway of the battery cells is effectively inhibited.

Description

Technical Field

[0001] The utility model relates to the technical field of an immersion type liquid-cooled energy storage battery, in particular to an immersion type liquid-cooled energy storage battery system. Background Art

[0002] With the widespread application of energy storage battery systems and the need for current energy storage battery systems to continuously improve energy density and power density to meet actual usage needs, their safety has received increasing attention.

[0003] The increase in the power density of the energy storage battery system will cause the battery cells to generate more heat and consume more power. If the temperature of the battery cells cannot be effectively controlled in a timely manner, it may cause thermal runaway of the battery cells, resulting in fire in the energy storage battery system or even an explosion.

[0004] However, most of the battery PACK packages of existing energy storage battery systems adopt air cooling or cold plate liquid cooling to control the battery temperature, while some energy storage battery systems adopt immersion liquid cooling in which multiple battery modules are placed in the same box and the inside of the box is filled with coolant to achieve battery temperature control. However, the above temperature control methods cannot make the battery cells of the battery module meet the temperature uniformity requirements and solve the thermal runaway problem of the battery cells. Utility Model Content

[0005] The purpose of the utility model is to provide an immersion-type liquid-cooled energy storage battery system, which can provide a separate liquid cooling circulation loop for multiple battery packs, which is beneficial for the battery cells of the battery pack to meet the temperature uniformity requirements and solve the problem of excessive pressure in the battery pack, thereby effectively suppressing the occurrence of thermal runaway of the battery cells and ensuring the safety of the energy storage battery system.

[0006] In order to achieve the above-mentioned purpose, the utility model discloses an immersion liquid-cooled energy storage battery system, which includes: a accommodating rack, a plurality of battery packs and a refrigeration device, the accommodating rack is provided with a plurality of accommodating positions; the plurality of battery packs are respectively installed in the corresponding accommodating positions, each of the battery packs includes a box body, a plurality of battery modules and a ventilation device, the box body is provided with a liquid inlet interface and a liquid return interface penetrating its box wall, the plurality of battery modules are arranged in the box body at intervals, the ventilation device is arranged on the box wall of the box body and is used to balance the air pressure inside and outside the battery pack; the refrigeration device is provided with a plurality of first connecting pipes and a plurality of second connecting pipes, each of the first connecting pipe and the second connecting pipe is respectively connected to the liquid inlet interface and the liquid return interface of a battery pack, the refrigeration device transports cooling liquid to each of the battery packs through the first connecting pipe and recovers cooling liquid from each of the battery packs through the second connecting pipe, and the refrigeration device is used to control the temperature of the cooling liquid flowing to each of the battery packs respectively.

[0007] Optionally, the battery pack is provided with a liquid inlet duct connected to the liquid inlet interface and a liquid return duct connected to the liquid return interface, the liquid inlet duct and the liquid return duct are respectively arranged on two inner sides of the box body in the horizontal direction, and a plurality of through holes are longitudinally spaced apart on one side of the liquid inlet duct and the liquid return duct close to the battery module.

[0008] Optionally, a plurality of the battery modules extend longitudinally and are arranged side by side transversely, a plurality of first flow channels are formed between two adjacent battery modules, a plurality of second flow channels are formed between the inner side wall of the box body and the battery module, a third flow channel is formed between the top wall of the box body and the battery module, and both sides of the first flow channel are respectively connected to the two second flow channels arranged longitudinally, so that the coolant flows through the four outer side walls of each of the battery modules through the first flow channel and the second flow channel, and the third flow channel is connected to the first flow channel and the second flow channel, so that the coolant flows through the upper surface of each of the battery modules through the third flow channel.

[0009] Optionally, the box body is provided with a pressure relief port penetrating through the box wall, and the ventilation device comprises a ventilation valve, which is provided at the pressure relief port and is used to control the gas in the box body to be discharged from the box body in one direction.

[0010] Optionally, each of the battery modules includes a plurality of battery cells arranged longitudinally and a plurality of connectors, the plurality of battery cells of the plurality of battery modules are connected in series through the plurality of connectors, the box wall of the box body is provided with a positive connector and a negative connector, and the positive connector and the negative connector are electrically connected to both ends of the battery modules connected in series, respectively.

[0011] Optionally, the refrigeration device includes multiple sets of coolant circulation modules and multiple coolant cooling devices, each of the coolant circulation modules includes a heater and an electronic water pump, the two ends of the heater are respectively connected to the first connecting pipe and the first output end of the corresponding coolant cooling device, the heater is used to heat the coolant output by the coolant cooling device to a set temperature and output it through the first connecting pipe, the two ends of the electronic water pump are respectively connected to the second connecting pipe and the first input end of the corresponding coolant cooling device, and the electronic water pump is used to extract the coolant refluxed from the battery pack through the second connecting pipe.

[0012] Optionally, each of the battery packs is provided with a first temperature sensor, which is used to detect the temperature of the battery module. The refrigeration device is provided with multiple second temperature sensors corresponding to the multiple second connecting tubes, and the second temperature sensors are used to detect the temperature of the coolant returning through the second connecting tubes. The refrigeration device is used to adjust the temperature of the coolant flowing to the corresponding first connecting tube according to the detection information of the first temperature sensor or the second temperature sensor.

[0013] Optionally, the refrigeration device includes multiple sets of heat exchange modules and refrigerant circulation modules, each of the heat exchange modules includes a heat exchanger and an expansion valve, the heat exchanger is connected to the corresponding first connecting pipe and the second connecting pipe, the refrigerant circulation module includes a compressor and a condenser, the input end of the compressor is connected to the second output end of each heat exchanger, the two ends of the condenser are respectively connected to the output end of the compressor and the input end of each expansion valve, the output end of each expansion valve is respectively connected to the second input end of the corresponding heat exchanger, the compressor is used to compress the refrigerant output by each heat exchanger into a high-temperature and high-pressure gaseous refrigerant, the condenser is used to condense the gaseous refrigerant into a liquid refrigerant, and each expansion valve is used to throttle the inflowing liquid refrigerant into a low-temperature and low-pressure two-phase refrigerant, and each heat exchanger is used for heat exchange between the two-phase refrigerant and the coolant to absorb the heat of the coolant.

[0014] The utility model provides separate liquid cooling circulation loops for multiple battery packs respectively. The multiple battery packs are respectively installed on the accommodating positions of the accommodating rack. Multiple battery modules are arranged at intervals in the box of the battery pack. The box wall of the box is provided with a penetrating liquid inlet interface and a liquid return interface and a ventilation device for balancing the air pressure inside and outside the battery pack, so as to effectively solve the problem of excessive pressure in the battery pack and ensure the safety of the energy storage battery system. The liquid inlet interface and the liquid return interface of each battery pack are respectively connected to the refrigeration device through the first connecting tube and the second connecting tube. The refrigeration device transports cooling liquid to each battery pack through the first connecting tube and recovers cooling liquid from each battery pack through the second connecting tube, and controls the temperature of the cooling liquid flowing to each battery pack respectively, which is conducive to the battery cells of the battery pack to meet the temperature uniformity requirement and effectively suppresses the occurrence of thermal runaway of the battery cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a front view of the immersed liquid-cooled energy storage battery system according to an embodiment of the utility model.

[0016] Figure 2 It is a three-dimensional structural diagram of a battery pack in an immersion liquid-cooled energy storage battery system according to an embodiment of the utility model.

[0017] Figure 3This is a three-dimensional structural diagram from another angle of the battery pack in the immersed liquid-cooled energy storage battery system of an embodiment of the utility model.

[0018] Figure 4 It is a schematic structural diagram of an immersion liquid-cooled energy storage battery system according to an embodiment of the utility model. DETAILED DESCRIPTION

[0019] In order to explain the technical content, structural features, achieved objectives and effects of the present invention in detail, the following is a detailed description in conjunction with the implementation modes and the accompanying drawings.

[0020] See also Figures 1 to 4 The utility model discloses an immersion liquid-cooled energy storage battery system, which comprises: a accommodating rack 1, a plurality of battery packs 2 and a refrigeration device 3, wherein the accommodating rack 1 is provided with a plurality of accommodating positions 11; the plurality of battery packs 2 are respectively installed in the corresponding accommodating positions 11, each battery pack 2 comprises a box body 21, a plurality of battery modules 22 and a ventilating device 23, the box body 21 is provided with a liquid inlet interface 211 and a liquid return interface 212 penetrating the box wall, the plurality of battery modules 22 are arranged at intervals in the box body 21, and the ventilating device 23 is arranged in the box body 21 is on the box wall and is used to balance the air pressure inside and outside the battery pack 2; the refrigeration device 3 is provided with a plurality of first connecting tubes 31 and a plurality of second connecting tubes 32, each of the first connecting tube 31 and the second connecting tube 32 is respectively connected to the liquid inlet interface 211 and the liquid return interface 212 of a battery pack 2, the refrigeration device 3 transports cooling liquid to each battery pack 2 through the first connecting tube 31 and recovers cooling liquid from each battery pack 2 through the second connecting tube 32, and the refrigeration device 3 is used to control the temperature of the cooling liquid flowing to each battery pack 2 respectively.

[0021] The utility model provides a separate liquid cooling circulation loop for each of the plurality of battery packs 2. The plurality of battery packs 2 are respectively installed on the accommodating positions 11 of the accommodating rack 1. A plurality of battery modules 22 are arranged at intervals in the box body 21 of the battery pack 2. The box wall of the box body 21 is provided with a penetrating liquid inlet interface 211 and a liquid return interface 212 and a ventilating device 23 for balancing the air pressure inside and outside the battery pack 2, so as to effectively solve the problem of excessive pressure in the battery pack 2 and ensure the safety of the energy storage battery system. The liquid inlet interface 211 and the liquid return interface 212 of each battery pack 2 are respectively connected to the refrigeration device 3 through the first connecting tube 31 and the second connecting tube 32. The refrigeration device 3 transports cooling liquid to each battery pack 2 through the first connecting tube 31 and recovers cooling liquid from each battery pack 2 through the second connecting tube 32, and controls the temperature of the cooling liquid flowing to each battery pack 2, so as to help the battery cells of the battery pack 2 meet the temperature uniformity requirement and effectively suppress the occurrence of thermal runaway of the battery cells.

[0022] See also Figures 1 to 4The battery pack 2 is provided with a liquid inlet conduit 241 connected to the liquid inlet interface 211 and a liquid return conduit 242 connected to the liquid return interface 212. The liquid inlet conduit 241 and the liquid return conduit 242 are respectively arranged on the two inner sides of the box body 21 in the horizontal direction. A plurality of through holes 243 are arranged at intervals in the longitudinal direction on one side of the liquid inlet conduit 241 and the liquid return conduit 242 close to the battery module 22, which is conducive to the coolant quickly entering the box body 21 and taking away the heat generated by the battery module 22 in time, so as to avoid thermal runaway of the battery as much as possible.

[0023] Optionally, multiple battery modules 22 extend longitudinally and are arranged side by side transversely, multiple first flow channels 213 are formed between two adjacent battery modules 22, multiple second flow channels 214 are formed between the inner wall of the box body 21 and the battery module 22, and a third flow channel 210 is formed between the top wall of the box body 21 and the battery module 22. The two sides of the first flow channel 213 are respectively connected to the two second flow channels 214 arranged longitudinally, so that the coolant flows through the four outer walls of each battery module 22 through the first flow channel 213 and the second flow channel 214, and the third flow channel 210 is connected to the first flow channel 213 and the second flow channel 214, so that the coolant flows through the upper surface of each battery module 22 through the third flow channel 210, so that the battery module 22 is completely immersed in the coolant, thereby cooling the battery module 22 in all directions, thereby improving the heat dissipation effect, heat dissipation efficiency and reliability of the energy storage battery system.

[0024] Specifically, in this embodiment, the coolant flows into the box body 21 from the through hole 243 of the liquid inlet conduit 241, and quickly flows into the first flow channel 213, and flows into the second flow channel 214 through the first flow channel 213, and flows into the third flow channel 210 through the first flow channel 213 and the second flow channel 214, so that the surroundings and upper surface of each battery module 22 are filled with coolant, which is beneficial for the battery module 22 to fully contact with the coolant and achieve the effect of rapid heat exchange, and then the coolant flows out from the through hole 243 of the liquid return conduit 242 in the first flow channel 213.

[0025] See also Figures 1 to 4 The box body 21 is provided with a pressure relief port 215 penetrating through the box wall. The ventilation device 23 includes a ventilation valve 231, which is arranged at the pressure relief port 215. The ventilation valve 231 is used to control the gas in the box body 21 to be discharged from the box body 21 in one direction, so as to effectively balance the pressure difference between the inside and outside of the box body 21.

[0026] Specifically, in the present embodiment, the pressure relief port 215 is arranged at a height higher than the liquid level of the coolant in the box body 21. When the battery cell 221 has thermal runaway due to a short circuit or other reasons, a large amount of gas will be generated. The air valve 231 can discharge the gas generated by the battery cell 221 through the pressure relief port 215 in a timely manner, and cooperate with the coolant to quickly cool down the battery cell 221 that has thermal runaway, effectively ensuring that there will be no explosion or fire in the battery pack 2, thereby improving the overall safety performance of the energy storage battery system.

[0027] See also Figures 1 to 4 Each battery module 22 includes a plurality of battery cells 221 arranged longitudinally and a plurality of connectors 222. The plurality of battery cells 221 of the plurality of battery modules 22 are connected in series through the plurality of connectors 222. The box wall of the box body 21 is provided with a positive connector 216 and a negative connector 217. The positive connector 216 and the negative connector 217 are electrically connected to the two ends of the battery modules 22 connected in series, respectively.

[0028] Specifically, in the present embodiment, the box body 21 includes a frame body 218 provided with a placement groove 2181 and a detachable cover body 219 sealed and assembled on the top of the frame body 218. A plurality of battery modules 22 are arranged in the placement groove 2181 of the frame body 218 along the lateral intervals. The two ends of the connector 222 are respectively electrically connected to the positive electrode of one of the two adjacent battery cells 221 and the negative electrode of the other battery cell 221. The front side wall of the frame body 218 is provided with a liquid inlet interface 211, a liquid return interface 212, a pressure relief port 215, a positive connector 216 and a negative connector 217. The liquid inlet interface 211 and the liquid return interface 212 are respectively provided with a bent pipe 201 connected to the liquid inlet conduit 241 and the liquid return conduit 242. The positive connector 216 and the negative connector 217 are respectively provided with a bent electrical connector 202 electrically connected to the connectors 222 at both ends of the battery modules 22 connected in series, but are not limited thereto.

[0029] See also Figures 1 to 4 The refrigeration device 3 includes multiple sets of coolant circulation modules 31 and coolant cooling devices 32. Each coolant circulation module 31 includes a heater 311 and an electronic water pump 312. The two ends of the heater 311 are respectively connected to the first connecting pipe 31 and the first output end of the coolant cooling device 32. The heater 311 is used to heat the coolant output by the coolant cooling device 32 to a set temperature and output it through the first connecting pipe 31. The two ends of the electronic water pump 312 are respectively connected to the second connecting pipe 32 and the first input end of the coolant cooling device 32. The electronic water pump 312 is used to extract the coolant refluxed from the battery pack 2 through the second connecting pipe 32. In the entire energy storage battery system, the refrigeration device 3 is provided with an independent coolant circulation system corresponding to each battery pack 2. In conjunction with the liquid cooling circuit provided for each battery pack 2, the coolants between the battery packs 2 do not affect each other, effectively solving the problem of excessive pressure in the battery pack 2.

[0030] Specifically, in this embodiment, the accommodating rack 1 is vertically provided with a plurality of accommodating positions 11, and a refrigeration device 3 is installed on one side of the accommodating position 11, and the refrigeration device 3 is vertically connected with a plurality of first connecting pipes 31 and a plurality of second connecting pipes 32, and each coolant circulation module 31 is connected to the liquid inlet interface 211 and the liquid return interface 212 of a corresponding battery pack 2 through the first connecting pipe 31 and the second connecting pipe 32, and then the coolant with higher temperature is sucked back through the electronic water pump 312, and the coolant is cooled by the coolant cooling device 32 and then re-delivered to the battery pack 2, so as to form a plurality of independent coolant circulation loops, but not limited to this.

[0031] Optionally, each battery pack 2 is provided with a first temperature sensor 223, the first temperature sensor 223 is used to detect the temperature of the battery module 22, the refrigeration device 3 is provided with multiple second temperature sensors 313 corresponding to the multiple second connecting tubes 32, the second temperature sensors 313 are used to detect the temperature of the coolant returning through the second connecting tubes 32, and the refrigeration device 3 is used to adjust the temperature of the coolant flowing to the corresponding first connecting tube 31 according to the detection information of the first temperature sensor 223 or the second temperature sensor 313.

[0032] Specifically, in this embodiment, the refrigeration device 3 is provided with a controller 33, and the controller 33 is communicated with the heater 311 of each coolant circulation module 31, and is communicated with each first temperature sensor 223 and each second temperature sensor 313 to obtain their temperature detection information, and adjust the set temperature of the heater 311 in the corresponding coolant circulation module 31 according to this information, so that the heater 311 heats the coolant with a lower temperature to a suitable temperature, and the coolant with a suitable temperature enters the corresponding battery pack 2 to exchange heat with the battery module, which is beneficial to keep the battery cells 221 of the battery module 22 at the optimal temperature for charging and discharging, but is not limited to this.

[0033] Optionally, the refrigeration device 3 includes multiple sets of heat exchange modules 34 and multiple refrigerant circulation modules 35, each heat exchange module 34 includes a heat exchanger 341 and an expansion valve 342, the heat exchanger 341 is connected to the corresponding first connecting pipe 31 and the second connecting pipe 32, the refrigerant circulation module 35 includes a compressor 351 and a condenser 352, the input end of the compressor 351 is connected to the second output end of each heat exchanger 341, and the two ends of the condenser 352 are respectively connected to the output end of the compressor 351 and the expansion valve 34 2, the output end of each expansion valve 342 is respectively connected to the second input end of the corresponding heat exchanger 341, the compressor 351 is used to compress the refrigerant output by each heat exchanger 341 into a high-temperature and high-pressure gaseous refrigerant, the condenser 352 is used to condense the gaseous refrigerant into a liquid refrigerant, each expansion valve 342 is respectively used to throttle the inflowing liquid refrigerant into a low-temperature and low-pressure two-phase refrigerant, and each heat exchanger 341 is used for the two-phase refrigerant to exchange heat with the coolant to absorb the heat of the coolant.

[0034] Specifically, in this embodiment, after the refrigerant passes through the refrigeration process of the compressor 351, the condenser 352 and the expansion valve 342, it enters the heat exchanger 341 of the corresponding heat exchange module 34 respectively, and exchanges heat with the coolant to absorb the heat of the coolant. Then the refrigerant in each heat exchanger 341 is sucked into the compressor 351 again, completing a refrigeration cycle and starting a new refrigeration cycle again, but not limited to this.

[0035] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. Therefore, equivalent changes made according to the scope of the patent application of the present invention are still within the scope covered by the present invention.

Claims

1. An immersion liquid-cooled energy storage battery system, characterized in that: include: A accommodating rack, wherein the accommodating rack is provided with a plurality of accommodating positions; A plurality of battery packs, each of which is installed in the corresponding accommodation positions, each of which comprises a box body, a plurality of battery modules and a ventilating device, the box body is provided with a liquid inlet interface and a liquid return interface penetrating the box wall, the plurality of battery modules are arranged in the box body at intervals, and the ventilating device is provided on the box wall of the box body and is used to balance the air pressure inside and outside the battery pack; A refrigeration device, wherein the refrigeration device is provided with a plurality of first connecting tubes and a plurality of second connecting tubes, each of the first connecting tube and the second connecting tube is respectively connected to the liquid inlet interface and the liquid return interface of a battery pack, the refrigeration device transports cooling liquid to each battery pack through the first connecting tube and recovers cooling liquid from each battery pack through the second connecting tube, and the refrigeration device is used to control the temperature of the cooling liquid flowing to each battery pack respectively.

2. The immersion liquid-cooled energy storage battery system according to claim 1, characterized in that: The battery pack is provided with a liquid inlet conduit connected to the liquid inlet interface and a liquid return conduit connected to the liquid return interface. The liquid inlet conduit and the liquid return conduit are respectively arranged on the two inner sides of the box body in the horizontal direction. A plurality of through holes are longitudinally spaced apart on one side of the liquid inlet conduit and the liquid return conduit close to the battery module.

3. The immersion liquid-cooled energy storage battery system according to claim 1, characterized in that: The plurality of battery modules extend longitudinally and are arranged side by side transversely, a plurality of first flow channels are formed between two adjacent battery modules, a plurality of second flow channels are formed between the inner side wall of the box body and the battery module, a third flow channel is formed between the top wall of the box body and the battery module, both sides of the first flow channel are respectively connected with the two second flow channels arranged longitudinally, so that the coolant flows through the four outer side walls of each of the battery modules through the first flow channel and the second flow channel, and the third flow channel is connected with the first flow channel and the second flow channel, so that the coolant flows through the upper surface of each of the battery modules through the third flow channel.

4. The submerged liquid-cooled energy storage battery system according to claim 1, characterized in that: The box body is provided with a pressure relief port penetrating through the box wall, and the ventilation device comprises a ventilation valve, which is arranged at the pressure relief port and is used to control the gas in the box body to be discharged from the box body in one direction.

5. The submerged liquid-cooled energy storage battery system according to claim 1, characterized in that: Each of the battery modules includes a plurality of battery cells arranged longitudinally and a plurality of connectors. The plurality of battery cells of the plurality of battery modules are connected in series through the plurality of connectors. The box wall of the box body is provided with a positive connector and a negative connector. The positive connector and the negative connector are electrically connected to the two ends of the battery modules connected in series, respectively.

6. The submerged liquid-cooled energy storage battery system according to claim 1, characterized in that: The refrigeration device includes multiple sets of coolant circulation modules and multiple coolant cooling devices, each of the coolant circulation modules includes a heater and an electronic water pump, the two ends of the heater are respectively connected to the first connecting pipe and the first output end of the corresponding coolant cooling device, the heater is used to heat the coolant output by the coolant cooling device to a set temperature and output it through the first connecting pipe, the two ends of the electronic water pump are respectively connected to the second connecting pipe and the first input end of the corresponding coolant cooling device, and the electronic water pump is used to extract the coolant refluxed from the battery pack through the second connecting pipe.

7. The submerged liquid-cooled energy storage battery system according to claim 1, characterized in that: Each of the battery packs is provided with a first temperature sensor, which is used to detect the temperature of the battery module. The refrigeration device is provided with multiple second temperature sensors corresponding to the multiple second connecting tubes, and the second temperature sensors are used to detect the temperature of the coolant returning through the second connecting tubes. The refrigeration device is used to adjust the temperature of the coolant flowing to the corresponding first connecting tube according to the detection information of the first temperature sensor or the second temperature sensor.

8. The submerged liquid-cooled energy storage battery system according to claim 1, characterized in that: The refrigeration device includes multiple sets of heat exchange modules and refrigerant circulation modules, each of the heat exchange modules includes a heat exchanger and an expansion valve, the heat exchanger is connected to the corresponding first connecting pipe and the second connecting pipe, the refrigerant circulation module includes a compressor and a condenser, the input end of the compressor is connected to the second output end of each heat exchanger, the two ends of the condenser are respectively connected to the output end of the compressor and the input end of each expansion valve, the output end of each expansion valve is respectively connected to the second input end of the corresponding heat exchanger, the compressor is used to compress the refrigerant output by each heat exchanger into a high-temperature and high-pressure gaseous refrigerant, the condenser is used to condense the gaseous refrigerant into a liquid refrigerant, and each expansion valve is used to throttle the inflowing liquid refrigerant into a low-temperature and low-pressure two-phase refrigerant, and each heat exchanger is used for heat exchange between the two-phase refrigerant and the coolant to absorb the heat of the coolant.

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