Flat tube heat exchange assembly and battery thermal management system

Abstract

The application provides a flat tube heat exchange assembly and a battery thermal management system. The flat tube heat exchange assembly comprises a liquid header, a liquid distribution pipe, a liquid passage pipe, heat exchange flat tubes, an air passage pipe, a gas distribution pipe and a gas header, the liquid header is connected with the liquid distribution pipe through the liquid passage pipe, the heat exchange flat tubes are multiple, the multiple heat exchange flat tubes are arranged along a transverse direction and a longitudinal direction in sequence to form multiple rows of cooling pipe groups, an installation space for installing batteries is arranged between adjacent cooling pipe groups, the liquid header is connected with a first end of the cooling pipe group, the gas header is connected with a second end of the cooling pipe group, the air passage pipe is connected between the gas distribution pipe and the gas header, and the liquid header gradually increases in cross-sectional area along a direction from bottom to top. According to the flat tube heat exchange assembly, the distribution uniformity of the refrigerant can be improved, and the heat exchange effect is enhanced.

Description

Technical Field

[0001] This invention relates to the field of battery thermal management technology, and more specifically, to a flat tube heat exchange assembly and a battery thermal management system. Background Technology

[0002] The power battery is one of the core components of an electric vehicle. Power batteries are generally encapsulated in a sealed casing. During charging and discharging, the battery generates heat due to its internal resistance. If this heat is not dissipated in time, it will accumulate and, when it reaches a certain temperature, will severely affect the battery's charging and discharging efficiency and lifespan. Power batteries have poor adaptability to low and high temperature environments. After being placed in a low-temperature environment, the battery needs to be heated to its operating temperature before use. During rapid charging in a high-temperature environment, the battery pack needs to be cooled to prevent overheating and damage to the battery or causing safety accidents. In low-temperature environments, the battery pack needs to be heated to prevent rapid capacity degradation caused by excessively low battery temperatures.

[0003] Currently, electric vehicle batteries are primarily cooled and heated using water within cold plates, but water has relatively low heat exchange efficiency. A small number of power batteries use refrigerant for heating and cooling within cold plates, but this suffers from problems such as uneven refrigerant distribution within the flow channels leading to insufficient heat exchange. Summary of the Invention

[0004] The main objective of this invention is to provide a flat tube heat exchange component and a battery thermal management system, which can improve the uniformity of refrigerant distribution and enhance the heat exchange effect.

[0005] To achieve the above objectives, according to one aspect of the present invention, a flat tube heat exchange assembly is provided, comprising a liquid manifold, a liquid distribution pipe, a liquid passage pipe, a heat exchange flat tube, a vent pipe, a gas distribution pipe, and a gas manifold. The liquid manifold is connected to the liquid distribution pipe via the liquid passage pipe. There are multiple heat exchange flat tubes arranged sequentially in the transverse and longitudinal directions to form multiple rows of cooling tube groups. Adjacent cooling tube groups are configured with mounting spaces for installing batteries. The liquid manifold is connected to a first end of the cooling tube group, and the gas manifold is connected to a second end of the cooling tube group. The vent pipe is connected between the gas distribution pipe and the gas manifold. The cross-sectional area of ​​the liquid manifold gradually increases from bottom to top.

[0006] Furthermore, the liquid manifold is tapered.

[0007] Furthermore, the internal channels of the liquid manifold are stepped, and the internal channels include multiple stages. Each stage corresponds to a heat exchange flat tube connected to the cooling tube group, and the cross-sectional area of ​​the stage increases from bottom to top.

[0008] Furthermore, the vent pipe extends into the bottom of the gas manifold, and the vent pipe is sealed at the end of the gas manifold. The vent pipe is provided with an air outlet, and each heat exchange flat tube of the cooling tube assembly corresponds to at least one air outlet.

[0009] Furthermore, the diameter of the vent is 1 / 4 to 1 / 3 of the diameter of the vent pipe.

[0010] Furthermore, a support structure is provided inside the heat exchange flat tube, and the support structure is supported between the two heat exchange side plates of the heat exchange flat tube.

[0011] Furthermore, the support structure is an elastic element, and the support structure abuts against both heat exchange side plates, or the distance between the support structure and the two heat exchange side plates is less than a preset value.

[0012] Furthermore, in the cross-section of the support structure, the support structure includes intermediate supports and end supports, with end supports connected to both ends of the intermediate supports. Both the intermediate supports and the end supports can provide independent support for the heat exchange side plate.

[0013] Furthermore, the end support includes an arc-shaped support segment.

[0014] Furthermore, the cross-section of the supporting structure is shaped like a 3, a 8, a W, an Ω, an X, an H, an M, a U, or an E.

[0015] Furthermore, the length of the support structure is the same as or less than the length of the heat exchange flat tube it is located on.

[0016] According to another aspect of the present invention, a battery thermal management system is provided, including a battery and a flat tube heat exchange assembly, wherein the flat tube heat exchange assembly is the aforementioned flat tube heat exchange assembly, and the battery is disposed within the mounting space of the flat tube heat exchange assembly.

[0017] Furthermore, the battery thermal management system also includes a refrigerant pump, an intermediate heat exchanger, a cooling pipe, and a heating pipe. The refrigerant pump, the flat tube heat exchange assembly, and the intermediate heat exchanger are connected in sequence to form a cooling cycle. The cooling pipe and the heating pipe are respectively connected to the intermediate heat exchanger for heat exchange.

[0018] According to the technical solution of this invention, the flat tube heat exchange assembly includes a liquid manifold, a liquid distribution pipe, a liquid passage pipe, a heat exchange flat tube, a vent pipe, a gas distribution pipe, and a gas manifold. The liquid manifold is connected to the liquid distribution pipe through the liquid passage pipe. There are multiple heat exchange flat tubes, which are arranged sequentially in the transverse and longitudinal directions to form multiple rows of cooling tube groups. The space between adjacent cooling tube groups is configured as an installation space for installing batteries. The liquid manifold is connected to the first end of the cooling tube group, and the gas manifold is connected to the second end of the cooling tube group. The vent pipe is connected between the gas distribution pipe and the gas manifold. The cross-sectional area of ​​the liquid manifold gradually increases from bottom to top. This flat tube heat exchange assembly optimizes the liquid manifold, making its cross-sectional area gradually increase from bottom to top. This reduces the refrigerant flow resistance at the top and increases the refrigerant flow resistance at the bottom, ensuring that the refrigerant flow rate distributed to each heat exchange flat tube is basically the same. This improves the heat exchange uniformity of each heat exchange flat tube in the cooling tube group, enhances the heat exchange performance and effect of the flat tube heat exchange assembly, and improves the overall temperature uniformity of the battery. Attached Figure Description

[0019] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0020] Figure 1 A three-dimensional structural schematic diagram of a flat tube heat exchange assembly according to an embodiment of the present invention is shown;

[0021] Figure 2 A side view of the flat tube heat exchange assembly according to an embodiment of the present invention is shown.

[0022] Figure 3 A partial cross-sectional view of the flat tube heat exchange assembly according to an embodiment of the present invention is shown.

[0023] Figure 4 It shows Figure 3 A partially enlarged structural diagram of the flat tube heat exchanger assembly;

[0024] Figure 5 A top view of the flat tube heat exchange assembly according to an embodiment of the present invention is shown;

[0025] Figure 6 A schematic diagram illustrating the structural principle of the battery thermal management system according to an embodiment of the present invention is shown;

[0026] Figure 7 It shows Figure 6 A partially enlarged schematic diagram of the left side of the battery thermal management system; and

[0027] Figure 8 It shows Figure 6 A partially enlarged schematic diagram of the right side of the battery thermal management system.

[0028] The above figures include the following reference numerals:

[0029] 1. Liquid manifold; 2. Liquid distribution pipe; 3. Liquid passage pipe; 4. Heat exchange flat tube; 5. Battery; 6. Vent pipe; 7. Gas distribution pipe; 8. Gas manifold; 9. Support structure; 10. Refrigerant pump; 11. Heating tube; 12. Intermediate heat exchanger; 13. Cooling tube; 14. Intermediate support; 15. End support; 16. Gas outlet. Detailed Implementation

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] See Figures 1 to 8 As shown, according to an embodiment of the present invention, the flat tube heat exchange assembly includes a liquid manifold 1, a liquid distribution pipe 2, a liquid passage pipe 3, a heat exchange flat tube 4, a vent pipe 6, a gas distribution pipe 7, and a gas manifold 8. The liquid manifold 1 is connected to the liquid distribution pipe 2 through the liquid passage pipe 3. There are multiple heat exchange flat tubes 4, which are arranged sequentially in the transverse and longitudinal directions to form multiple rows of cooling tube groups. The space between adjacent cooling tube groups is configured as an installation space for installing the battery 5. The liquid manifold 1 is connected to the first end of the cooling tube group, and the gas manifold 8 is connected to the second end of the cooling tube group. The vent pipe 6 is connected between the gas distribution pipe 7 and the gas manifold 8. The cross-sectional area of ​​the liquid manifold 1 gradually increases from bottom to top.

[0032] The flat tube heat exchange assembly optimizes the liquid manifold 1, making its cross-sectional area gradually increase from bottom to top. This reduces the refrigerant flow resistance at the top of the liquid manifold 1 and increases the refrigerant flow resistance at the bottom, ensuring that the refrigerant flow rate in each heat exchange flat tube 4 distributed to the same cooling tube group is basically the same. This improves the heat exchange uniformity of each heat exchange flat tube in the cooling tube group, enhances the heat exchange performance and effect of the flat tube heat exchange assembly, and improves the overall temperature uniformity of the battery.

[0033] In this embodiment, each liquid manifold 1 can correspond to a cooling tube group, that is, each liquid manifold 1 is connected to all heat exchange flat tubes 4 of a cooling tube group, so that each liquid manifold 1 can simultaneously deliver refrigerant to each heat exchange flat tube 4 of the same cooling tube group.

[0034] In other embodiments, a cooling tube group may also be provided with two or more liquid manifolds 1. The two or more liquid manifolds 1 are arranged sequentially along the arrangement direction of the heat exchange flat tubes 4 in the cooling tube group, and each liquid manifold 1 is connected to at least two heat exchange flat tubes 4.

[0035] In one embodiment, the liquid manifold 1 is tapered. In this embodiment, the liquid manifold 1 has a smooth, continuous outer surface, such as a tapered tube, or it can be any other structure with a continuously varying cross-sectional area.

[0036] In one embodiment, the internal channel of the liquid manifold 1 is stepped, and the internal channel includes multiple steps. Each step corresponds to a heat exchange flat tube 4 connected to the cooling tube group, and the cross-sectional area of ​​the steps increases from bottom to top.

[0037] In this embodiment, the internal channels of the liquid manifold 1 are stepped, with the smallest cross-section at the bottom and gradually increasing in cross-section from bottom to top. When liquid refrigerant flows into the liquid manifold 1, the flow rate of liquid refrigerant is the highest at the bottom and the lowest at the top due to gravity. Therefore, designing the bottom cross-section to be the smallest increases flow resistance and reduces the refrigerant flow rate at the bottom, while designing the top cross-section to be the largest reduces flow resistance and increases the refrigerant flow rate at the top, thus achieving a uniform flow distribution effect. This improves the heat exchange efficiency and heat exchange rate of the flat tube heat exchange assembly and also reduces the overall volume of the flat tube heat exchange assembly, making it more compact and lightweight.

[0038] In one embodiment, the vent pipe 6 extends into the bottom of the gas manifold 8, and the vent pipe 6 is sealed at the end of the gas manifold 8. The vent pipe 6 is provided with an air outlet 16, and each heat exchange flat tube 4 of the cooling tube assembly corresponds to at least one air outlet 16.

[0039] One end of the vent pipe 6 extends into the gas manifold 8, and an outlet 16 is provided on the section of the vent pipe 6 that is inserted into the gas manifold 8. Without the outlet 16, the refrigerant gas density is low, resulting in a large flow rate at the top of the gas manifold 8 and a small flow rate at the bottom. Therefore, an outlet 16 is provided on the vent pipe 6 at the opposite position of each heat exchange flat tube 4, allowing the refrigerant gas to be ejected from the outlet 16 and flow directly into the heat exchange flat tube 4, thus achieving a uniform flow distribution.

[0040] In one embodiment, the diameter of the vent hole 16 is 1 / 4 to 1 / 3 of the diameter of the vent pipe 6. This can avoid the vent hole 16 being too large, which would result in insufficient structural strength of the vent pipe 6, and can also ensure that the gaseous refrigerant has sufficient flow area to meet the heat exchange requirements of the heat exchange flat tube 4.

[0041] In one embodiment, a support structure 9 is provided inside the heat exchange flat tube 4, and the support structure 9 is supported between the two heat exchange side plates of the heat exchange flat tube 4.

[0042] In this embodiment, a support structure 9 is provided inside the heat exchange flat tube 4. The support structure 9 is used to support the heat exchange side plate located between the two batteries 5. When the batteries expand during use and squeeze the heat exchange flat tube 4, the support structure 9 can be used to support the heat exchange flat tube 4, thereby preventing the heat exchange flat tube 4 from being squeezed and damaged, improving the structural strength of the heat exchange flat tube 4, and increasing the durability of the heat exchange flat tube 4.

[0043] In one embodiment, the support structure 9 is an elastic element. When the support structure 9 is elastic, it will undergo elastic deformation when subjected to the expansion and compression of the battery 5. The greater the expansion and compression force of the battery, the greater the elastic force of the support structure 9, and the greater the support effect on the sidewall of the heat exchange flat tube 4. Therefore, it can well adapt to the expansion force of the battery 5 and form a better support for the heat exchange flat tube 4. In addition, since the support force formed by the support structure 9 on the heat exchange flat tube 4 changes accordingly with the expansion force of the battery 5, it can support the heat exchange flat tube 4 while avoiding damage to the heat exchange flat tube 4.

[0044] The support structure 9 should have a certain degree of elasticity and stiffness, so that the support structure 9 has a certain degree of elasticity and recovery ability, can elastically deform when subjected to external force, and can resist external force of a certain intensity without breaking.

[0045] In one embodiment, the support structure 9 abuts against both heat exchange side plates, thus forming a more adequate and effective support.

[0046] In one embodiment, the distance between the support structure 9 and the two heat exchange side plates is less than a preset value. This preset value cannot be too large, otherwise it will not be able to provide timely and effective support for the heat exchange flat tube 4. This preset value is, for example, 2 mm.

[0047] In one embodiment, the support structure 9 includes an intermediate support 14 and an end support 15 in its cross-section. The two ends of the intermediate support 14 are respectively connected to the end support 15. Both the intermediate support 14 and the end support 15 can provide independent support for the heat exchange side plate.

[0048] The width of the support structure 9 should be adapted to the width of the heat exchange flat tube 4, that is, it should be the same as or slightly smaller than the width of the heat exchange flat tube 4, so as to provide more effective support for the heat exchange flat tube 4. Dividing the support structure 9 into three sections allows for three-section support of the heat exchange flat tube 4, resulting in more support points, more uniform support force, more effective support for the heat exchange flat tube 4, and more balanced stress distribution.

[0049] In one embodiment, the end support 15 includes an arc-shaped support segment. In this embodiment, the middle support is V-shaped, and both end supports include an arc-shaped support segment and a planar support segment. The arc-shaped support segment is connected to the middle support via the planar support segment to form an integral structure, supporting the two heat exchange side plates of the heat exchange flat tube 4. The arc-shaped support segment has better elastic contraction and expansion effects, thus providing a support effect to the heat exchange flat tube 4 that better conforms to the expansion pressure changes of the battery 5.

[0050] In one embodiment, the cross-section of the support structure 9 is shaped like a 3, 8, W, Ω, X, H, M, U, or E. The cross-section of the support structure 9 can also be other shapes, as long as it can effectively support the two heat exchange side plates of the heat exchange flat tube 4.

[0051] In one embodiment, the length of the support structure 9 is the same as or less than the length of the heat exchange flat tube 4 to which it is located.

[0052] In one embodiment, the support structure 9 has a certain degree of elasticity and is W-shaped in cross-section, with the radius of the arc support section being approximately 8-10 mm. When the battery 5 expands during use, the expansion of the battery 5 will compress the heat exchange flat tube 4, potentially causing damage to the heat exchange flat tube 4 in severe cases. With the support structure 9 in place, when the battery 5 expands and compresses the heat exchange flat tube 4, the elastic support structure 9 extends vertically, providing support and reducing the stress on the heat exchange flat tube 4, thus preventing damage. Simultaneously, the support structure 9 forms a flow channel inside the heat exchange flat tube 4, allowing the refrigerant to flow within the channel and reducing the possibility of gas-liquid stratification within the refrigerant.

[0053] In one embodiment, the battery pack consists of 4 rows and 12 columns of batteries 5. Each column of batteries 5 has 5 heat exchange flat tubes 4 on its side. The heat exchange flat tubes 4 are approximately 6 mm wide and 25 mm high, with a height interval of approximately 15 mm. Liquid manifolds 1 and gas manifolds 8 are arranged at the left and right ends of the heat exchange flat tubes 4, respectively. Liquid passage pipes 3 and vent pipes 6 are respectively arranged at the center of the top of the liquid manifolds 1 and vent pipes 8. The liquid passage pipes 3 are connected to the liquid manifolds 1, and the vent pipes 6 are connected to the gas manifolds 8. Five liquid passage pipes 3 are connected to liquid distribution pipes 1, and five vent pipes 6 are connected to liquid distribution pipes 7.

[0054] See also Figures 6 to 8 As shown, the battery thermal management system includes a battery 5 and a flat tube heat exchange assembly, which is the same as the flat tube heat exchange assembly described above. The battery 5 is disposed within the installation space of the flat tube heat exchange assembly.

[0055] In one embodiment, the battery thermal management system further includes a refrigerant pump 10, an intermediate heat exchanger 12, a cooling pipe 13, and a heating pipe 11. The refrigerant pump 10, the flat tube heat exchange assembly, and the intermediate heat exchanger 12 are connected in sequence to form a cooling cycle. The cooling pipe 13 and the heating pipe 11 are respectively connected to the intermediate heat exchanger 12 for heat exchange.

[0056] Using a refrigerant pump 10 to drive the refrigerant circulation is less energy-consuming, quieter, and safer than using a compressor.

[0057] When battery 5 needs cooling in the summer, refrigerant pump 10 drives the refrigerant circulation according to... Figure 6 The solid line arrow indicates the direction of operation. Refrigerant pump 10 provides energy to the liquid refrigerant. Under the uniform distribution effect of liquid distribution pipe 2, the liquid refrigerant enters the liquid manifold 1 through liquid pipe 3. Under the flow equalization effect of liquid manifold 1, the liquid refrigerant flows into heat exchange flat tube 4, absorbing the heat released by battery 5, and the liquid refrigerant evaporates into gaseous refrigerant. The gaseous refrigerant enters the intermediate heat exchanger 12 through gas manifold 8, vent pipe 6, and gas distribution pipe 7. At this time, cooling pipe 13 is turned on, and heating pipe 11 is turned off. The gaseous refrigerant is condensed into liquid refrigerant by cooling pipe 13 in intermediate heat exchanger 12, completing one cycle.

[0058] When battery 5 needs heating in winter, refrigerant pump 10 reverses its operating direction, and the refrigerant circulation follows... Figure 6 The dashed arrow indicates the direction of operation. Refrigerant pump 10 provides energy to the liquid refrigerant, which enters the intermediate heat exchanger 12. At this time, heating pipe 11 is turned on, and cooling pipe 13 is turned off. Heating pipe 11 can collect waste heat from the engine or exhaust to heat the liquid refrigerant, turning it into gaseous refrigerant. The gaseous refrigerant enters the vent pipe 6 under the uniform distribution of gas distribution pipe 7. Under the injection action of vent pipe 6, the gaseous refrigerant is injected into the heat exchange flat tube 4, where it condenses and releases heat to heat the battery 5. The condensed refrigerant then passes through liquid manifold 1, liquid passage pipe 3, and liquid distribution pipe 2 into refrigerant pump 10, completing one cycle. By adjusting the speed of refrigerant pump 10, the battery load and refrigerant heating / cooling capacity can be matched in real time, avoiding waste of heat / cooling capacity.

[0059] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A flat tube heat exchange assembly, characterized in that, The system includes a liquid manifold (1), a liquid distribution pipe (2), a liquid passage pipe (3), a heat exchange flat tube (4), a vent pipe (6), a gas distribution pipe (7), and a gas manifold (8). The liquid manifold (1) is connected to the liquid distribution pipe (2) through the liquid passage pipe (3). There are multiple heat exchange flat tubes (4), which are arranged sequentially in the horizontal and vertical directions to form multiple rows of cooling tube groups. The space between adjacent cooling tube groups is configured to accommodate the battery (5). The liquid manifold (1) is connected to the first end of the cooling tube group, and the gas manifold (8) is connected to the second end of the cooling tube group. The vent pipe (6) is connected between the gas distribution pipe (7) and the gas manifold (8). The cross-sectional area of ​​the liquid manifold (1) gradually increases from bottom to top to reduce the refrigerant flow resistance at the top of the liquid manifold (1) and increase the refrigerant flow resistance at the bottom of the liquid manifold (1), so that the refrigerant flow rate in each heat exchange flat tube (4) distributed to the same cooling tube group is basically the same. A support structure (9) is provided inside the heat exchange flat tube (4), and the support structure (9) is supported between the two heat exchange side plates of the heat exchange flat tube (4). The support structure (9) is an elastic element.

2. The flat tube heat exchange assembly according to claim 1, characterized in that, The liquid manifold (1) is tapered.

3. The flat tube heat exchange assembly according to claim 1, characterized in that, The internal channel of the liquid manifold (1) is stepped, and the internal channel includes multiple steps. Each step corresponds to a heat exchange flat tube (4) connected to the cooling tube group. The cross-sectional area of ​​the step increases from bottom to top.

4. The flat tube heat exchange assembly according to any one of claims 1 to 3, characterized in that, The vent pipe (6) extends into the bottom of the gas manifold (8), and the vent pipe (6) is sealed at the end of the gas manifold (8). The vent pipe (6) is provided with an air outlet (16), and each heat exchange flat tube (4) of the cooling tube group corresponds to at least one air outlet (16).

5. The flat tube heat exchange assembly according to claim 4, characterized in that, The diameter of the vent (16) is 1 / 4 to 1 / 3 of the diameter of the vent pipe (6).

6. The flat tube heat exchange assembly according to claim 1, characterized in that, The support structure (9) abuts against both of the heat exchange side plates, or the distance between the support structure (9) and the two heat exchange side plates is less than a preset value.

7. The flat tube heat exchange assembly according to claim 6, characterized in that, On the cross-section of the support structure (9), the support structure (9) includes an intermediate support (14) and an end support (15). The two ends of the intermediate support (14) are respectively connected to the end support (15). Both the intermediate support (14) and the end support (15) can form independent support for the heat exchange side plate.

8. The flat tube heat exchange assembly according to claim 7, characterized in that, The end support (15) includes an arc support segment.

9. The flat tube heat exchange assembly according to claim 1, characterized in that, The cross-section of the support structure (9) is shaped like a figure 3, figure 8, W, Ω, X, H, M, U or E.

10. The flat tube heat exchange assembly according to claim 1, characterized in that, The length of the support structure (9) is the same as or less than the length of the heat exchange flat tube (4) to which it is located.

11. A battery thermal management system, comprising a battery (5) and a flat tube heat exchange assembly, characterized in that, The flat tube heat exchange assembly is the flat tube heat exchange assembly according to any one of claims 1 to 10, and the battery (5) is disposed in the installation space of the flat tube heat exchange assembly.

12. The battery thermal management system according to claim 11, characterized in that, The battery thermal management system further includes a refrigerant pump (10), an intermediate heat exchanger (12), a cooling pipe (13), and a heating pipe (11). The refrigerant pump (10), the flat tube heat exchange assembly, and the intermediate heat exchanger (12) are connected in sequence to form a cooling cycle. The cooling pipe (13) and the heating pipe (11) are respectively connected to the intermediate heat exchanger (12) for heat exchange.

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