Thermal management liquid storage structure of energy storage system, thermal management system and control method

Abstract

The invention relates to a thermal management liquid storage structure of an energy storage system, a thermal management system and a control method, the liquid storage structure is arranged above a battery pack, and the control method comprises the following steps: receiving charge and discharge information, and obtaining pre-cooling time and cooling time matched with charge and discharge duration according to the charge and discharge information; according to the precooling time, a three-way valve is controlled to communicate with a first pipeline and a second pipeline, a third pipeline is turned off, and the liquid cooling unit is controlled to operate, so that cooling liquid in a liquid storage structure is precooled; controlling a three-way valve to communicate with a first pipeline and a third pipeline according to the cooling time, turning off a second pipeline, and controlling the liquid cooling unit to continuously operate so as to efficiently cool the battery pack; and closing the liquid cooling unit and the three-way valve when the cooling time is finished. The problems that the upper temperature and the lower temperature in the energy storage battery cabinet are not uniform, and the short-time heating value is large under the fast charging and fast discharging working conditions can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage systems, and in particular to a thermal management liquid storage structure, a thermal management system and a control method of an energy storage system. Background Art

[0002] The energy storage system has the function of regulating energy storage and release, can efficiently realize the time and space migration of energy, and improve the stability of the power system. It will gradually become a rigid demand and standard configuration. At present, large-scale container-type lithium battery energy storage systems have the characteristics of long life, high energy density, high efficiency, and strong environmental adaptability, and the installed capacity is developing rapidly. However, since the working performance and safety of lithium batteries are greatly related to their operating temperature, excessively high or low temperatures will cause the battery to face great challenges in safety and working performance. In severe cases, thermal runaway or heat spread accidents will occur, which will not only damage the product, but also may lead to safety accidents. In addition, uneven temperature will also increase the difference in the life and capacity of the battery cells in the system, affecting the efficiency of the energy storage system. Therefore, efficient thermal management system design is the key to the safe and reliable operation of lithium battery energy storage systems.

[0003] According to existing test data, the temperature of the top battery pack in each cluster of energy storage battery cabinets is generally 2~4℃ higher than that of other battery packs. Analysis shows that the uneven ambient temperature inside the cabinet is the biggest reason: because the upper part is closer to the top of the cabinet, and the temperature of the top of the cabinet will increase significantly under long-term sunlight, the temperature of the upper area of ​​the cabinet is significantly higher than other areas. For the 1-hour fast charging and discharging condition of the energy storage system, the heat generated by the battery cell has the characteristics of high heat generation but short duration. If the water cooling unit is selected according to the parameters of the peak heating period, it will cause a large design redundancy and have a greater impact on the cost. However, if it is selected according to the lower heat dissipation requirements, the battery cell temperature will be too high during the peak heating period, affecting the system life and safety.

[0004] Therefore, it is necessary to provide a solution to the problem of uneven temperature in the upper and lower parts of the energy storage battery cabinet and high short-term heat generation under fast charging and discharging conditions. Summary of the invention

[0005] Based on the above description, the present invention provides a thermal management liquid storage structure, a thermal management system and a control method for an energy storage system to solve the problem of uneven upper and lower temperatures in the energy storage battery cabinet and high short-term heat generation under fast charging and discharging conditions.

[0006] According to a first aspect of the present invention, a thermal management liquid storage structure of an energy storage system is provided, comprising a liquid cooling box, wherein the liquid cooling box is provided with a liquid inlet and a liquid outlet, and the bottom surface of the liquid cooling box is provided with a concave-convex structure, wherein the concave-convex structure is arranged above a heat source.

[0007] Based on the above technical solution, the present invention can also be improved as follows.

[0008] Preferably, the concave-convex structure includes a plurality of protrusions.

[0009] Preferably, the concave-convex structure includes a plurality of convex ridges and concave grooves spaced apart from each other.

[0010] Preferably, the liquid inlet and the liquid outlet are arranged at two opposite ends of the liquid cooling box.

[0011] Preferably, the liquid inlet and the liquid outlet are arranged close to the bottom surface of the liquid cooling box.

[0012] Preferably, a hoisting structure is provided on the liquid cooling box.

[0013] According to a second aspect of the present invention, a thermal management system of an energy storage system is provided, comprising the aforementioned thermal management liquid storage structure, and further comprising a first pipeline, a second pipeline, a third pipeline, a three-way valve and a liquid cooling unit, wherein one end of the first pipeline, one end of the second pipeline and one end of the third pipeline are connected to three interfaces of the three-way valve in a one-to-one correspondence; the other end of the first pipeline is connected to a liquid outlet of the liquid cooling unit, and the thermal management liquid storage structure is arranged in series in the first pipeline; the other end of the second pipeline and the other end of the third pipeline are both connected to a liquid inlet of the liquid cooling unit; The energy storage system includes a plurality of battery packs arranged in multiple layers, and the bottom surface of the liquid cooling box is arranged adjacent to the top of the uppermost battery pack; the third pipeline includes a plurality of liquid cooling branches, and the plurality of liquid cooling branches correspond one-to-one with the plurality of battery packs.

[0014] Preferably, a plurality of the liquid cooling branches are connected in parallel.

[0015] Preferably, the capacity of the liquid cooling box is compatible with the sum of the capacities of the first pipeline, the second pipeline and the third pipeline.

[0016] According to a second aspect of the present invention, a method for controlling a thermal management system of an energy storage system is provided, based on the aforementioned thermal management system, comprising: Receiving charging and discharging information, and acquiring a precooling time and a cooling time matching the charging and discharging duration according to the charging and discharging information; According to the precooling time, the three-way valve is controlled to connect the first pipeline and the second pipeline, and to shut off the third pipeline, and the liquid cooling unit is controlled to operate; According to the cooling time, the three-way valve is controlled to connect the first pipeline and the third pipeline, and the second pipeline is shut off, and the liquid cooling unit is controlled to continue to operate; When it is determined that the cooling time is over, the liquid cooling unit and the three-way valve are closed.

[0017] Compared with the prior art, the technical solution of this application has the following beneficial technical effects: The present invention provides a thermal management liquid storage structure, thermal management system and control method for an energy storage system. By setting a liquid cooling box above the heat source (such as a battery pack) in the energy storage battery cabinet, the upper part of the energy storage battery cabinet can be cooled by the flow of refrigerant in the liquid cooling box to solve the problem of uneven temperature between the upper and lower parts of the energy storage battery cabinet; and the concave-convex structure on the bottom of the liquid cooling box can increase the heat exchange area and improve the heat exchange efficiency. When the first pipeline and the second pipeline are connected, the upper part of the energy storage battery cabinet can be cooled, and the energy storage battery cabinet can be pre-cooled before rapid charging and discharging; when the first pipeline and the third pipeline are connected, the battery pack can be quickly cooled. Combined with the pre-cooling operation, the cooling efficiency of the battery pack under fast charging and discharging conditions can be improved, and the problem of high short-term heat generation under fast charging and discharging conditions can be solved. By switching between the two pipeline connection methods, different cooling schemes can be switched to improve the thermal management efficiency of the energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of a three-dimensional structure from a bottom-up perspective of a thermal management liquid storage structure of an energy storage system provided by an embodiment of the present invention; Figure 2 A partial cross-sectional view from a front perspective of a thermal management liquid storage structure of an energy storage system provided by an embodiment of the present invention; Figure 3 A schematic diagram of a pipeline structure of a thermal management system of an energy storage system provided by an embodiment of the present invention; Figure 4 A flow chart of a thermal management system control method for an energy storage system provided in an embodiment of the present invention.

[0019] In the accompanying drawings, the components represented by the reference numerals are listed as follows: 1. Liquid cooling box, 101. Liquid inlet, 102. Liquid outlet, 103. Bottom surface, 103a. Concave-convex structure, 104. Lifting structure, 2. Three-way valve, 3. First pipeline, 4. Second pipeline, 5. Third pipeline, 501. Liquid cooling branch, 6. Liquid cooling unit, 7. Battery pack, A. Accommodation space. DETAILED DESCRIPTION

[0020] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0022] It will be appreciated that spatial relationship terms such as "under", "beneath", "below", "under", "above", "above", etc., may be used herein to describe the relationship of an element or feature shown in the figures to other elements or features. It should be understood that in addition to the orientations shown in the figures, spatial relationship terms also include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is flipped, the element or feature described as "under other elements" or "under it" or "under it" will be oriented as "on" the other elements or features. Therefore, the exemplary terms "under" and "under" may include both upper and lower orientations. In addition, the device may also include additional orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptors used herein are interpreted accordingly.

[0023] It should be noted that when an element is considered to be "connected" to another element, it can be directly connected to the other element, or connected to the other element through an intermediate element. The "connection" in the following embodiments should be understood as "electrical connection", "communication connection", etc. if the connected circuits, modules, units, etc. have electrical signals or data transmission between each other.

[0024] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" etc. specify the presence of stated features, wholes, steps, operations, components, parts or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts or combinations thereof.

[0025] This embodiment provides a thermal management liquid storage structure of an energy storage system, such as Figure 1 The three-dimensional structure schematic diagram of the thermal management liquid storage structure is shown in FIG. Figure 2 The figure shows a partial cross-sectional view of the thermal management liquid storage structure. Figure 1 and Figure 2As shown, the thermal management liquid storage structure includes a closed liquid cooling box 1, and a storage space A for accommodating a cooling medium is provided in the liquid cooling box 1. The liquid cooling box 1 is provided with a liquid inlet 101 and a liquid outlet 102 connected to the storage space A, so as to facilitate the cooling medium (such as cooling water or cooling oil) to flow into and out of the storage space A. In the use scenario, the thermal management liquid storage structure is installed at the top of the energy storage cabinet, and its height is designed according to the accommodating space at the top of different cabinets. Generally, the height is set to about 5-15cm, and the length and width are slightly smaller than the cabinet size. The specific size and shape of the liquid cooling box 1 can be adaptively adjusted according to the pipeline system. The liquid cooling box 1 is preferably made of metal, such as aluminum alloy, to ensure the heat exchange efficiency. The bottom surface 103 of the liquid cooling box 1 is provided with a concave-convex structure 103a, and the concave-convex structure 103a is arranged above the heat source. The concave-convex structure 103a can increase the surface area of ​​the bottom surface 103 of the liquid cooling box 1.

[0026] It can be understood that the thermal management liquid storage structure of the energy storage system provided in this embodiment can cool the upper part of the energy storage battery cabinet by arranging a liquid cooling box 1 above the heat source (such as the battery pack 7) in the energy storage battery cabinet, through the flow of refrigerant in the liquid cooling box 1, so as to solve the problem of uneven temperature between the upper and lower parts of the energy storage battery cabinet; and the concave-convex structure 103a of the bottom surface 103 of the liquid cooling box 1 can increase the heat exchange area and improve the heat exchange efficiency.

[0027] Based on the above technical solution, this embodiment can also be improved as follows.

[0028] In one possible embodiment, the concave-convex structure 103a includes a plurality of protrusions, such as cylindrical protrusions, conical protrusions or spherical protrusions (not shown in the figure), so as to increase the heat exchange area of ​​the bottom surface 103 of the liquid cooling box 1 and improve the heat exchange efficiency between the bottom surface 103 of the liquid cooling box 1 and the cabinet environment.

[0029] like Figure 2 As shown, as another embodiment, the concave-convex structure 103a can also be set as a plurality of convex ridges and grooves arranged at intervals from each other. A plurality of convex ridges and grooves arranged at intervals form a continuous or discontinuous wavy curved surface structure, which can also increase the heat exchange area of ​​the bottom surface 103 of the liquid cooling box 1 and improve the heat exchange efficiency between the bottom surface 103 of the liquid cooling box 1 and the cabinet environment.

[0030] In one possible implementation, Figure 2 As shown, the liquid inlet 101 and the liquid outlet 102 are arranged at opposite ends of the liquid cooling box 1, so that the cooling medium can flow from one lateral end of the liquid cooling box 1 to the other lateral end of the liquid cooling box 1 that is farther away, so that the cooling medium has a longer flow path in the liquid cooling box 1, thereby improving the cooling efficiency in the cabinet and making the ambient temperature in the cabinet more evenly regulated.

[0031] In one possible implementation, Figure 2 As shown, the liquid inlet 101 and the liquid outlet 102 are arranged close to the bottom surface 103 of the liquid cooling box 1, so that the cooling medium with a lower temperature can be closer to the position with a higher temperature in the energy storage cabinet, thereby improving the cooling effect.

[0032] In one possible implementation, Figure 1 and Figure 2 As shown, the liquid cooling box 1 is provided with a lifting structure 104, such as a lifting hook ( Figure 1 The liquid cooling box 1 can be reliably installed in the energy storage cabinet through the lifting structure 104.

[0033] like Figure 3 As shown, on the basis of the above embodiments, this embodiment further provides a thermal management system for an energy storage system, which includes the thermal management liquid storage structure of the above embodiments, and also includes a first pipeline 3, a second pipeline 4, a third pipeline 5, a three-way valve 2 and a liquid cooling unit 6. One end of the first pipeline 3, one end of the second pipeline 4 and one end of the third pipeline 5 are connected to the three interfaces of the three-way valve 2 in a one-to-one correspondence; the other end of the first pipeline 3 is connected to the liquid outlet of the liquid cooling unit 6, and the thermal management liquid storage structure is arranged in series in the first pipeline 3. The other end of the second pipeline 4 and the other end of the third pipeline 5 are both connected to the liquid inlet of the liquid cooling unit 6.

[0034] The energy storage system includes a plurality of battery packs 7 arranged in multiple layers, and the bottom surface 103 of the liquid cooling box 1 is arranged adjacent to the top of the uppermost battery pack 7; the third pipeline 5 includes a plurality of liquid cooling branches 501, and the plurality of liquid cooling branches 501 correspond to a plurality of battery packs 7 one by one. The battery pack 7 includes a battery module and a water cooling plate, and the battery module is installed on the water cooling plate. In order to simplify the pipeline system, a plurality of liquid cooling branches 501 can be integrated into the water cooling plate of the battery pack 7 to simplify the pipeline installation and improve the cooling efficiency of the liquid cooling branch 501 on the battery pack 7.

[0035] It is understandable that the three-way valve 2 has three interfaces, and according to its specific type, it is possible to selectively control the connection between two interfaces and perform channel switching. In this embodiment, a three-way solenoid valve is preferably used to achieve control of a remote pipeline system.

[0036] For example Figure 3As shown, the three-way valve 2 has three interfaces, namely, interface 1, interface 2 and interface 3. When the connecting interface 1 and interface 2 and interface 3 are kept closed, the cooling medium is cooled by the liquid cooling unit 6. At this time, when the cooling medium passes through the liquid cooling box 1, the upper environment of the energy storage cabinet can be cooled. When the connecting interface 1 and interface 3 and interface 2 are kept closed, the cooling medium is cooled by the liquid cooling unit 6. At this time, after passing through the liquid cooling box 1, the cooling medium passes through the liquid cooling branch 501 of each battery pack 7 and finally returns to the liquid cooling unit 6. The upper environment of the energy storage cabinet and each battery pack 7 can be cooled to adapt to the fast charging and discharging conditions of the battery pack 7.

[0037] In one possible implementation, Figure 3 As shown, in order to achieve uniform cooling of each battery pack 7, a plurality of liquid cooling branches 501 may be provided in parallel.

[0038] As a preferred embodiment, the capacity of the liquid cooling box 1 is close to the sum of the capacities of the first pipeline 3, the second pipeline 4 and the third pipeline 5, so as to obtain a better cooling effect.

[0039] Based on the thermal management system of the energy storage system provided in the above embodiments, Figure 4 As shown, this embodiment also provides a thermal management system control method for an energy storage system, the method comprising the following steps: Confirm that the thermal management mode is normal mode or charge-discharge mode; A. If it is a normal mode, the three-way valve 2 is controlled to connect the first pipeline 3 and the second pipeline 4, close the third pipeline 5, and control the liquid cooling unit 6 to operate; B. If it is a charge and discharge mode, receive the charge and discharge information, and obtain the precooling time and cooling time matching the charge and discharge duration according to the charge and discharge information; According to the precooling time, the three-way valve 2 is controlled to connect the first pipeline 3 and the second pipeline 4, to shut off the third pipeline 5, and to control the operation of the liquid cooling unit 6; According to the cooling time, the three-way valve 2 is controlled to connect the first pipeline 3 and the third pipeline 5, and to shut off the second pipeline 4, and the liquid cooling unit 6 is controlled to continue to operate; When it is determined that the cooling time is over, confirm whether to end the thermal management mode. If the result is that the thermal management mode is not ended, reconfirm the specific thermal management mode type, otherwise close the liquid cooling unit 6 and the three-way valve 2 to end the entire thermal management process.

[0040] It is understandable that in the thermal management mode where the heat dissipation of the battery pack 7 is not required, the first pipeline 3, the liquid cooling box 1, the second pipeline 4 and the liquid cooling unit 6 can be connected through the three-way valve 2 to form a loop, and the third pipeline 5 does not need to be connected. In this mode, the surface of the liquid cooling box 1 can be heat-exchanged with the upper environment of the upper battery in the energy storage cabinet, thereby cooling the upper environment in the energy storage cabinet, solving the problem of uneven upper and lower ambient temperatures in the energy storage cabinet. The temperature reduction range can be adjusted by controlling the operating power of the liquid cooling unit 6.

[0041] Under the condition of short-time rapid charging and discharging, the thermal management mode selects the charging and discharging mode. In this mode, since the battery pack 7 will generate a lot of heat during short-time charging and discharging, the battery pack 7 needs to be cooled down quickly in a short time. In this case, in order to improve the heat exchange efficiency, the time to start the chiller in advance can be determined according to the charging and discharging time, so as to pre-cool the liquid cooling box 1 and the cooling medium in the pipeline before charging and discharging begins. During specific operations, the charging and discharging information of the energy storage battery cabinet is received in advance. The charging and discharging information includes at least the charging and discharging time and the charging and discharging time point. Different charging and discharging time lengths are preset with matching precooling time and cooling time.

[0042] For example, if continuous charging and discharging for 1 hour is required, the chiller needs to be turned on 1 hour in advance, that is, the charging and discharging time is 1 hour, and the precooling time is 1 hour. Since a large amount of heat is generated during the charging and discharging process, in order to ensure a better cooling effect, it is necessary to set a period of cooling after the charging and discharging is completed, so the cooling time after precooling needs to be set longer than the charging and discharging time. In specific operation, in the precooling stage, the interfaces 1 and 2 of the three-way valve 2 are controlled to be connected at the same time, and the interface 3 is closed. At this time, the liquid cooling unit 6 cools the cooling medium (such as cooling water or cooling oil) in the liquid cooling box 1 alone. Until the start of charging and discharging, the interface 2 of the three-way valve 2 is closed, the interface 1 and the interface 3 are connected, and the liquid cooling box 1, the liquid cooling branch 501 of the battery pack 7 and the liquid cooling unit 6 constitute a cooling circuit. At this time, the low-temperature coolant stored in the liquid cooling box 1 in advance can cool the battery pack 7 in time, and the liquid cooling unit 6 can also share part of the cooling capacity, which can make up for the disadvantage that the real-time cooling capacity of the liquid cooling unit 6 is lower than the cooling capacity required for the heat dissipation of the battery pack 7.

[0043] The present invention provides a thermal management liquid storage structure, thermal management system and control method for an energy storage system. By arranging a liquid cooling box 1 above a heat source (such as a battery pack 7) in an energy storage battery cabinet, the top area of ​​the energy storage battery cabinet with a higher temperature due to sunlight and floating hot air can be cooled down through the flow of refrigerant in the liquid cooling box 1, thereby improving the excessive temperature difference between the top battery pack 7 and the remaining battery packs 7 at the bottom. The concave-convex structure 103a of the bottom surface 103 of the liquid cooling box 1 can increase the heat exchange area and improve the heat exchange efficiency. The liquid cooling box 1 is installed at the top of the energy storage cabinet, which can not only reduce the top temperature of the box, but also serve as a refrigeration buffer container for the cooling circuit. When the first pipeline 3 and the second pipeline 4 are connected, the upper part of the energy storage battery cabinet can be cooled, and the energy storage battery cabinet can be pre-cooled before rapid charging and discharging; when the first pipeline 3 and the third pipeline 5 are connected, the battery pack 7 can be quickly cooled. Combined with the pre-cooling operation, the cooling efficiency of the battery pack 7 under rapid charging and discharging conditions can be improved, solving the problem of high short-term heat generation under rapid charging and discharging conditions. By switching between the two pipeline connection methods, different cooling schemes can be switched to improve the thermal management efficiency of the energy storage system.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A thermal management liquid storage structure for an energy storage system, characterized in that: The liquid cooling box (1) comprises a liquid cooling box (1), wherein a liquid inlet (101) and a liquid outlet (102) are provided on the liquid cooling box (1), and a concave-convex structure (103a) is provided on the bottom surface (103) of the liquid cooling box (1), and the concave-convex structure (103a) is arranged above a heat source.

2. The thermal management liquid storage structure of an energy storage system according to claim 1, characterized in that: The concave-convex structure (103a) comprises a plurality of convex parts.

3. The thermal management liquid storage structure of an energy storage system according to claim 1, characterized in that: The concave-convex structure (103a) comprises a plurality of convex ridges and concave grooves which are arranged at intervals from each other.

4. The thermal management liquid storage structure of an energy storage system according to claim 1, characterized in that: The liquid inlet (101) and the liquid outlet (102) are arranged at two opposite ends of the liquid cooling box (1).

5. A thermal management liquid storage structure for an energy storage system according to any one of claims 1 to 4, characterized in that: The liquid inlet (101) and the liquid outlet (102) are arranged close to the bottom surface (103) of the liquid cooling box (1).

6. The thermal management liquid storage structure of an energy storage system according to claim 1, characterized in that: The liquid cooling box (1) is provided with a hoisting structure (104).

7. A thermal management system for an energy storage system, characterized in that: The thermal management liquid storage structure comprises the thermal management liquid storage structure according to any one of claims 1 to 6, and further comprises a first pipeline (3), a second pipeline (4), a third pipeline (5), a three-way valve (2) and a liquid cooling unit (6), wherein one end of the first pipeline (3), one end of the second pipeline (4) and one end of the third pipeline (5) are connected to the three interfaces of the three-way valve (2) in a one-to-one correspondence; the other end of the first pipeline (3) is connected to the liquid outlet of the liquid cooling unit (6), and the thermal management liquid storage structure is arranged in series in the first pipeline (3); The other end of the second pipeline (4) and the other end of the third pipeline (5) are both connected to the liquid inlet end of the liquid cooling unit (6); The energy storage system comprises a plurality of battery packs (7) arranged in multiple layers, the bottom surface (103) of the liquid cooling box (1) being arranged adjacent to the top of the uppermost battery pack (7); the third pipeline (5) comprises a plurality of liquid cooling branches (501), and the plurality of liquid cooling branches (501) are matched with the plurality of battery packs (7) in a one-to-one correspondence.

8. The thermal management system of an energy storage system according to claim 7, characterized in that: The plurality of liquid cooling branches (501) are connected in parallel.

9. The thermal management system of an energy storage system according to claim 7, characterized in that: The capacity of the liquid cooling box (1) is compatible with the sum of the capacities of the first pipeline (3), the second pipeline (4) and the third pipeline (5).

10. A method for controlling a thermal management system of an energy storage system, characterized in that: The thermal management system according to any one of claims 7 to 9 comprises: Receiving charging and discharging information, and acquiring a precooling time and a cooling time matching the charging and discharging duration according to the charging and discharging information; According to the precooling time, the three-way valve (2) is controlled to connect the first pipeline (3) and the second pipeline (4), to shut off the third pipeline (5), and to control the operation of the liquid cooling unit (6); According to the cooling time, the three-way valve (2) is controlled to connect the first pipeline (3) and the third pipeline (5), to shut off the second pipeline (4), and to control the liquid cooling unit (6) to continue to operate; When it is determined that the cooling time has ended, the liquid cooling unit (6) and the three-way valve (2) are closed.

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