Power battery thermal management system of large flat plate heat pipe coupling topological optimization cold plate

Abstract

The invention provides a power battery thermal management system of a large flat plate heat pipe coupling topological optimization cold plate, which belongs to the technical field of power battery thermal management systems, and comprises a battery pack formed by connecting a plurality of batteries in series, a large flat plate heat pipe group and a topological optimization cold plate group, the large flat plate heat pipe set is in contact with the battery pack and the topological optimization cold plate set, and heat conduction silica gel gaskets are arranged between the large flat plate heat pipe set and the battery pack and between the large flat plate heat pipe set and the topological optimization cold plate set. The contact face of the large flat plate heat pipe set and the battery pack is the evaporation end of the large flat plate heat pipe set, the contact face of the large flat plate heat pipe set and the topological optimization cold plate set is the condensation end of the large flat plate heat pipe set, and the large flat plate heat pipe set is not provided with a heat insulation end. Efficient heat dissipation can be achieved, it is ensured that the battery pack temperature is stabilized in a reasonable interval, the battery pack temperature difference is reduced, and the battery pack consistency is improved; meanwhile, the space utilization rate is improved, the system power consumption and the voltage drop are reduced, and the overall performance and the safety of the battery are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power battery thermal management systems, and in particular to a power battery thermal management system of a large flat heat pipe coupled with a topology optimized cold plate. Background Art

[0002] At a time when electric vehicles are widely popularized and energy storage power stations are developing rapidly, battery performance is directly related to the safety, endurance and stability of electric vehicles and energy storage power stations. The ideal operating temperature range of the battery is 25℃-40℃, and the temperature difference of the battery pack must be controlled within a range of no more than 5℃. When the temperature is below -40℃, the internal resistance of the battery increases, the reaction speed slows down, and it cannot be charged normally; and excessively high temperatures can easily cause thermal runaway, which seriously threatens battery safety. At the same time, temperature differences can also cause the consistency of the battery pack to deteriorate, and some single cells may be overcharged or over-discharged, greatly affecting the overall performance and service life of the battery pack.

[0003] At present, common battery thermal management technologies mainly include air cooling, liquid cooling and phase change material (PCM) cooling. Although air cooling technology has a simple structure, due to the limited heat transfer capacity of air, there are problems such as slow heat exchange speed and large temperature difference between inlet and outlet, which makes it difficult to meet the needs of efficient heat dissipation and is gradually replaced by other technologies. Although liquid cooling technology has a high heat exchange efficiency, current research mainly focuses on microchannels, optimized flow channel structure, improved control strategies, and the use of nanofluids and other enhanced heat transfer methods, but liquid cooling plates have the safety hazard of leakage. PCM has the advantages of low cost, large latent heat, and non-corrosiveness. However, it is a passive heat transfer method and usually needs to be used in conjunction with other cooling methods, which may result in a large space occupation and a risk of leakage during the melting process.

[0004] Therefore, there is an urgent need for a more efficient, safe and space-efficient power battery thermal management system to solve the technical problems existing in the prior art. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a power battery thermal management system with a large flat heat pipe coupled with a topology optimized cold plate, which can achieve efficient heat dissipation, ensure that the battery pack temperature is stable within a reasonable range, reduce the temperature difference of the battery pack, and improve the consistency of the battery pack; at the same time, it improves space utilization, reduces system power consumption and voltage drop, and improves the overall performance and safety of the battery.

[0006] To achieve the above object, the present invention provides the following solutions: A power battery thermal management system of a large flat heat pipe coupled with a topology optimized cold plate, wherein the power battery heat pipe system is a symmetrical structure as a whole, comprising: A battery pack consisting of several 70Ah ternary lithium batteries connected in series; A large flat heat pipe group, the inner wall of the large flat heat pipe group is in contact with the outer wall of the battery group, and a thermally conductive silicone gasket is provided on the contact surface between the large flat heat pipe group and the battery group; A topology optimized cold plate group, wherein the topology optimized cold plate group is in contact with the large flat plate heat pipe group, and a thermally conductive silicone gasket is provided on the contact surface between the topology optimized cold plate group and the large flat plate heat pipe group; The contact surface between the large flat heat pipe group and the battery group is the evaporation end of the large flat heat pipe group, the contact surface between the large flat heat pipe group and the topology optimized cold plate group is the condensation end of the large flat heat pipe group, and the large flat heat pipe group is not provided with an insulating end.

[0007] Preferably, the large flat heat pipe group consists of a first flat heat pipe and a second flat heat pipe, the first flat heat pipe and the second flat heat pipe are symmetrically arranged, the first flat heat pipe is arranged on one side of the battery pack, and the second flat heat pipe is arranged on the other side of the battery pack, and the first flat heat pipe and the second flat heat pipe are both provided with a liquid wick, a support column and a fixed structure inside, the support column is used to enhance the structural strength of the large flat heat pipe group, and the fixed structure is used to stabilize the liquid wick.

[0008] Preferably, the preparation process of the liquid absorbent core is: selecting a core material after chemical oxidation as the material of the liquid absorbent core, and then placing the liquid absorbent core in a reducing environment containing hydrogen or ammonia at 200°C for 2 hours to form a firm oxidation layer of a plurality of strip-shaped worm aggregates on the skeleton surface of the liquid absorbent core, and the size of the strip-shaped worm aggregates is 10μm~20μm.

[0009] Preferably, the topology optimized cold plate group consists of a first topology optimized liquid cooling plate and a second topology optimized liquid cooling plate, the first topology optimized liquid cooling plate and the second topology optimized liquid cooling plate are symmetrically arranged, and the first topology optimized liquid cooling plate and the second topology optimized liquid cooling plate are respectively in contact with the condensation ends of the corresponding flat heat pipes.

[0010] Preferably, the first topology optimized liquid cooling plate and the second topology optimized liquid cooling plate have the same structure, the outlet of the first topology optimized liquid cooling plate and the outlet of the second topology optimized liquid cooling plate are both arranged at the bottom end of the corresponding liquid cooling plate, and the inlet of the first topology optimized liquid cooling plate and the inlet of the second topology optimized liquid cooling plate are both arranged at the top of the opposite surface of the corresponding outlet or at the same side of the corresponding outlet.

[0011] Preferably, the first topology optimized liquid cooling plate and the second topology optimized liquid cooling plate are both prepared by topology optimization, and the specific process is as follows: First, the variable density method is used to introduce virtual materials of different densities into the design domain of the liquid cooling plate. By adjusting the density value of the virtual material γ , change the regional flow resistance to optimize the flow path of the fluid in the liquid cooling plate and improve the heat dissipation efficiency, where 0≤ γ ≤1; the composite objective function obtained by weighted summation of the heat transfer performance index of the liquid cooling plate and the fluid power dissipation index is used as the optimization target; wherein the composite objective function is: ; In the formula, J is the composite objective function, and are the initial values ​​of fluid power dissipation and heat transfer performance index, is the weight factor, ranging from 0 to 1; in, is the fluid power dissipation index, and the calculation formula is: ; in, μ is the viscosity, u is the fluid velocity; α ( γ ) is the reverse permeability, and the calculation formula is: ; In the formula, q is the penalty factor, and are the reverse osmosis rates of solid and fluid, respectively; is the heat transfer performance index, and the calculation formula is: ; in, T is the design domain unit temperature, is the density value, is the design domain area; Secondly, set the volume fraction is the constraint condition for topology optimization, which represents the maximum proportion of the fluid area in the entire liquid cooling plate and meets the requirements: ; The optimal value of the volume fraction is determined through multiple simulations and experiments; Next, determine the weight factor The optimal value of balances the emphasis of heat transfer performance index and fluid power dissipation index in the composite objective function to achieve comprehensive performance optimization of the liquid cooling plate; Finally, the composite objective function is iteratively calculated, and the density value of the virtual material is continuously adjusted during the iteration process to determine the minimum value of the composite objective function: ; In the formula, is the minimum value of the composite objective function, which is used to achieve structural optimization of the first topology optimized liquid cooling plate and the second topology optimized liquid cooling plate.

[0012] Preferably, the volume fraction is the maximum proportion of the fluid area in the entire liquid cooling plate, and the optimal value of the volume fraction is determined by numerical simulation and experimental research, specifically: first, numerical simulation is performed, and a liquid cooling plate model is established using finite element analysis software, different volume fractions are set, and the flow channel pressure distribution, coolant flow rate, and battery pack average temperature are simulated and recorded; then, experimental research is performed to manufacture liquid cooling plate specimens with different volume fraction flow channels, and the specimens are tested under simulated power battery charging and discharging conditions to monitor the coolant flow rate, pressure loss, and battery pack temperature changes; finally, the numerical simulation results and experimental research results are combined. When the volume fraction is 0.5, the overall average temperature of the liquid cooling plate reaches the minimum value, so the optimal value of the volume fraction is determined to be 0.5.

[0013] Preferably, the weight factor is the proportion of the heat exchange performance index and the fluid power dissipation index in the composite objective function. The optimal value of the weight factor is determined by combining simulation and experiment, specifically: first, a simulation is performed, using software to simulate the performance of the liquid cooling plate under different weight factors, and recording the data of the average temperature of the battery pack and the pressure drop of the liquid cooling plate; then an experiment is performed to produce liquid cooling plate prototypes with different weight factors, and the tests are performed under a simulated power battery working environment to monitor the battery pack temperature, coolant flow and pressure changes; finally, the simulation data and experimental data are combined. When the weight factor is 0.6, the pressure drop change tends to be stable, and when the weight factor is 0.75, the average temperature of the battery pack reaches the minimum value, so the optimal value of the weight factor is 0.75.

[0014] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: (1) The present invention can quickly conduct and dissipate the heat generated by the battery pack through the coordinated work of the large flat heat pipe group and the topology optimized cold plate group, effectively reducing the average temperature and maximum temperature of the battery pack. Compared with the traditional straight channel cold plate, at a flow rate of 0.15m / s, the topology optimized optimal cold plate of the present invention can reduce the average temperature of the battery by 4.52℃ and the maximum temperature by 4.63℃, greatly improving the temperature uniformity of the battery pack and reducing the battery performance degradation caused by temperature differences.

[0015] (2) The present invention uses topology optimization to optimize the flow channel of the liquid cooling plate, effectively reducing the system pressure drop. When the flow rate is 0.15m / s, the pressure drop is reduced by 30.28% compared with the traditional straight channel liquid cooling plate. Under the condition that the maximum temperature of the battery does not exceed 40°C, the required pressure drop is reduced by 77.36% compared with the traditional straight channel liquid cooling plate, reducing the system operating power consumption and improving energy utilization efficiency.

[0016] (3) The large flat heat pipe group and battery group of the present invention adopt a staggered layout structure, which makes the overall thermal management system structure more compact and effectively improves the space utilization compared to the common method of attaching the heat pipe between two batteries. At the same time, the coupling design of the large flat heat pipe group and the topology optimized liquid cooling plate group further optimizes the system structure and achieves a more efficient heat dissipation function in a limited space.

[0017] (4) The support column inside the large flat heat pipe group of the present invention enhances the structural strength, and the fixed structure stabilizes the liquid absorption core, ensuring the reliable operation of the large flat heat pipe group under complex working conditions. The specially treated liquid absorption core enhances the capillary force and ensures smooth circulation of the working fluid. In addition, it avoids the leakage problem that may occur when the topology optimized liquid cooling plate group is used alone, and improves the reliability and safety of the entire thermal management system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0019] Figure 1 A schematic diagram of the overall structure provided in Embodiment 1 of the present invention; Figure 2 A schematic diagram of the structure of a large flat heat pipe group provided in Embodiment 1 of the present invention; Figure 3 A schematic diagram of the structure of a topology optimized liquid cooling plate group provided in Embodiment 1 of the present invention; Figure 4 The schematic diagram of the structure of two liquid cooling plates provided in the first embodiment of the present invention; wherein, Figure 4 (a) is a schematic diagram of the b7 cold plate structure. Figure 4 (b) is a schematic diagram of the straight cold plate structure; Figure 5 Two battery pack temperature cloud diagrams provided in Example 1 of the present invention; wherein, Figure 5 (a) is the temperature cloud diagram of the battery pack under the straight cold plate. Figure 5 (b) is the temperature cloud diagram of the battery pack under the b7 cold plate; Figure 6 Another overall structural diagram provided for the second embodiment of the present invention; Figure 7 This is a schematic diagram of the structure of another topology optimized liquid cooling plate group provided in Embodiment 2 of the present invention.

[0020] Reference numerals: 1. Battery pack; 2. Large flat heat pipe group; 21. First flat heat pipe; 22. Second flat heat pipe; 3. Topology optimized cold plate group; 31. First topology optimized liquid cold plate; 32. Second topology optimized liquid cold plate; 4. Upper cover plate; 5. Liquid suction core; 6. Liquid filling port; 7. Support column; 8. Bottom plate; 9. Inlet; 10. Outlet. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Embodiment 1 like Figure 1 As shown, the present invention provides a power battery thermal management system of a large flat heat pipe coupled with a topology optimized cold plate. The power battery heat pipe system is a symmetrical structure as a whole, including: A battery pack 1 is composed of a plurality of 70Ah ternary lithium batteries connected in series; in this embodiment, the number of ternary lithium batteries used is 12, and the battery pack 1 is numbered in the manner of battery I, battery II, battery III, battery IV, battery V, battery VI, battery VII, battery VIII, battery IX, battery X, battery XI, and battery XII according to the left and right sides and the battery positions; A large flat heat pipe group 2, the inner wall of the large flat heat pipe group 2 is in contact with the outer wall of the battery group 1, and a thermally conductive silicone gasket is provided on the contact surface between the large flat heat pipe group 2 and the battery group 1; A topology optimized cold plate group 3, the topology optimized cold plate group 3 is in contact with the large flat plate heat pipe group 2, and a thermally conductive silicone gasket is provided on the contact surface between the topology optimized cold plate group 3 and the large flat plate heat pipe group 2; The contact surface between the large flat heat pipe group 2 and the battery group 1 is the evaporation end of the large flat heat pipe group 2, and the contact surface between the large flat heat pipe group 2 and the topology optimized cold plate group 3 is the condensation end of the large flat heat pipe group 2, and the large flat heat pipe group 2 is not provided with an insulating end.

[0024] The large flat heat pipe group 2 and the battery group 1 are arranged in a staggered manner to improve the space utilization of the overall system. The large flat heat pipe group 2 consists of a first flat heat pipe 21 and a second flat heat pipe 22. The first flat heat pipe 21 and the second flat heat pipe 22 are symmetrically arranged. The first flat heat pipe 21 is arranged on one side of the battery group 1, and the second flat heat pipe 22 is arranged on the other side of the battery group 1. Figure 2 The first flat plate heat pipe 21 and the second flat plate heat pipe 22 are both provided with a liquid wick 5, a support column 7 and a fixed structure. The support column 7 is used to enhance the structural strength of the large flat plate heat pipe group 2, and the fixed structure is used to stabilize the liquid wick 5. In addition, the large flat plate heat pipe group 2 also includes an upper cover plate 4 and a bottom plate 8. The support column 7 is arranged on the inner side of the bottom plate 8, and a liquid injection port 6 is also arranged at one end of the bottom plate 8. The upper cover plate 4 is arranged above the liquid wick 5.

[0025] Secondly, the preparation process of the above-mentioned liquid absorbent core 5 is: select the core material after chemical oxidation as the material of the liquid absorbent core, and then place the liquid absorbent core 5 at 200°C and in a reducing environment containing hydrogen or ammonia for 2 hours, so that a firm oxidation layer of several strip-like worm aggregates is formed on the skeleton surface of the liquid absorbent core 5, and the size of the strip-like worm aggregates is 10μm~20μm.

[0026] In this embodiment, the topology optimized cold plate group 3 is composed of a first topology optimized liquid cold plate 31 and a second topology optimized liquid cold plate 32, the first topology optimized liquid cold plate 31 and the second topology optimized liquid cold plate 32 are symmetrically arranged, and the first topology optimized liquid cold plate 31 and the second topology optimized liquid cold plate 32 are respectively in contact with the condensation ends of the corresponding flat heat pipes, and the first topology optimized liquid cold plate 31 and the second topology optimized liquid cold plate 32 have the same structure. Figure 3 The outlet 10 of the first topology optimized liquid cooling plate 31 and the outlet 10 of the second topology optimized liquid cooling plate 32 are both arranged at the bottom end of the corresponding liquid cooling plate, and the inlet 9 of the first topology optimized liquid cooling plate 31 and the inlet 9 of the second topology optimized liquid cooling plate 32 are both arranged at the top of the opposite surface of the corresponding outlet 10.

[0027] The first topology optimized liquid cooling plate 31 and the second topology optimized liquid cooling plate 32 are both prepared by topology optimization, and the specific process is as follows: First, the variable density method is used to introduce virtual materials of different densities into the design domain of the liquid cooling plate. By adjusting the density value of the virtual material γ , change the regional flow resistance to optimize the flow path of the fluid in the liquid cooling plate and improve the heat dissipation efficiency, where 0≤ γ ≤1; the composite objective function obtained by weighted summation of the heat transfer performance index of the liquid cooling plate and the fluid power dissipation index is used as the optimization target; wherein the composite objective function is: ; In the formula,J is the composite objective function, and are the initial values ​​of fluid power dissipation and heat transfer performance index, is the weight factor, ranging from 0 to 1; in, is the fluid power dissipation index, and the calculation formula is: ; in, μ is the viscosity, u is the fluid velocity; α ( γ ) is the reverse permeability, and the calculation formula is: ; In the formula, q is the penalty factor, which is 0.02 in this embodiment. and are the reverse osmosis rates of solid and fluid respectively; =0, ; Da is the Darcy number, which is 0.0001, and Re is the Reynolds number, which is calculated from the inlet flow velocity.

[0028] is the heat transfer performance index, and the calculation formula is: ; in, T is the design domain unit temperature, γ is the density value, is the design domain area; Secondly, set the volume fraction is the constraint condition for topology optimization, which represents the maximum proportion of the fluid area in the entire liquid cooling plate and meets the requirements: ; The optimal value of the volume fraction is determined through multiple simulations and experiments; Next, determine the weight factor The optimal value of balances the emphasis of heat transfer performance index and fluid power dissipation index in the composite objective function to achieve comprehensive performance optimization of the liquid cooling plate; Finally, the composite objective function is iteratively calculated, and the density value of the virtual material is continuously adjusted during the iteration process to determine the minimum value of the composite objective function: ; In the formula, is the minimum value of the composite objective function, which is used to achieve structural optimization of the first topology optimized liquid cooling plate and the second topology optimized liquid cooling plate.

[0029] In the above content, the volume fraction is the maximum proportion of the fluid area in the entire liquid cooling plate. The larger the volume fraction, the thicker the flow channel and the smaller the pressure drop, but the overall average temperature first decreases and then increases; the optimal value of the volume fraction is determined through numerical simulation and experimental research, specifically: first, numerical simulation is performed, and a liquid cooling plate model is established using finite element analysis software, different volume fractions are set, and the flow channel pressure distribution, coolant flow rate, and battery pack average temperature are simulated and recorded; then, experimental research is performed to manufacture liquid cooling plate specimens with different volume fraction flow channels, and the specimens are tested under simulated power battery charging and discharging conditions to monitor coolant flow, pressure loss, and battery pack temperature changes; finally, the numerical simulation results and experimental research results are combined. When the volume fraction is 0.5, the overall average temperature of the liquid cooling plate reaches the minimum value, so the optimal value of the volume fraction is determined to be 0.5. Reference Figure 4 (a) and Figure 4 (b) in the figure provides the structural schematic diagrams of the b7 cold plate and the straight cold plate respectively. Then, under the same working conditions, the heat dissipation effect of the battery pack of the two cold plates is intuitively demonstrated. The results are as follows Figure 5 (a) and Figure 5 As shown in (b) in the figure. Figure 5 In (a), the temperature distribution of the battery pack is relatively uneven, and the high temperature area accounts for a large proportion, indicating that the heat dissipation effect of the battery pack under the straight cold plate is limited. Figure 5 In (b), the overall temperature of the battery pack is reduced, the color distribution is more uniform, and the area of ​​the high-temperature area is significantly reduced. This shows that the b7 cold plate is the optimal topology optimized liquid cold plate. At a flow rate of 0.15 m / s, the maximum temperature is 4.63°C lower than that of the traditional straight cold plate, the average temperature is 4.52°C lower, and the pressure drop is reduced by 30.82%.

[0030] The weight factor is the proportion of the heat exchange performance index and the fluid power dissipation index in the composite objective function. The larger the value of the weight factor, the stronger the heat exchange performance in the composite objective function, but the pressure drop of the liquid cooling plate gradually increases; the smaller the value of the weight factor, the greater the proportion of the fluid power dissipation index in the composite function, and the flow channel design is relatively simple; the optimal value of the weight factor is determined by combining simulation and experiment, specifically: first, a simulation is performed, using software to simulate the performance of the liquid cooling plate under different weight factors, and recording the data of the average temperature of the battery pack and the pressure drop of the liquid cooling plate; then an experiment is conducted to produce liquid cooling plate prototypes with different weight factors, test them in a simulated power battery working environment, and monitor the battery pack temperature, coolant flow and pressure changes; finally, combining the simulation data and experimental data, when the weight factor is 0.6, the pressure drop change tends to be stable, and when the weight factor is 0.75, the average temperature of the battery pack reaches the minimum value, so the optimal value of the weight factor is 0.75.

[0031] Working principle: When the battery pack is discharged at a high rate, the generated heat is quickly transferred to the condensation end of the large flat heat pipe group 2 in a symmetrical direction. Since the condensation end is tightly fitted with the topology optimized cold plate group 3, and a high thermal conductivity silicone thermal pad is added to the interface between the two, the heat can be smoothly transferred to the low-temperature working fluid in the liquid cold plate. Subsequently, the low-temperature working fluid takes away the heat through the circulation system, thereby achieving efficient cooling of the battery pack 1, so that the power battery always maintains good temperature uniformity and rapid response characteristics, ensuring its efficient and safe operation.

[0032] Embodiment 2 like Figure 6 As shown, this embodiment also provides a power battery thermal management system with a large flat heat pipe coupled with a topology optimized cold plate, which is different from the first embodiment in that: Figure 7 The outlet 10 of the first topology optimized liquid cooling plate 31 and the outlet 10 of the second topology optimized liquid cooling plate 32 are both arranged at the bottom of the corresponding liquid cooling plate, the inlet 9 of the first topology optimized liquid cooling plate 31 and the inlet 9 of the second topology optimized liquid cooling plate 32 are both arranged on the same side of the corresponding outlet 10, and the rest are the same as in Example 1.

[0033] Therefore, the power battery thermal management system using the above-mentioned large flat heat pipe coupled topology optimized cold plate can achieve efficient heat dissipation, ensure that the battery pack temperature is stable in a reasonable range, reduce the temperature difference of the battery pack, and improve the consistency of the battery pack; at the same time, it improves space utilization, reduces system power consumption and voltage drop, and improves the overall performance and safety of the battery.

[0034] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0035] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A power battery thermal management system with a large flat heat pipe coupled with a topology optimized cold plate, characterized in that: The power battery heat pipe system is a symmetrical structure as a whole, including: A battery pack consisting of several batteries connected in series; A large flat heat pipe group, the inner wall of the large flat heat pipe group is in contact with the outer wall of the battery group, and a thermally conductive silicone gasket is provided on the contact surface between the large flat heat pipe group and the battery group; A topology optimized cold plate group, wherein the topology optimized cold plate group is in contact with the large flat plate heat pipe group, and a thermally conductive silicone gasket is provided on the contact surface between the topology optimized cold plate group and the large flat plate heat pipe group; The contact surface between the large flat heat pipe group and the battery group is the evaporation end of the large flat heat pipe group, the contact surface between the large flat heat pipe group and the topology optimized cold plate group is the condensation end of the large flat heat pipe group, and the large flat heat pipe group is not provided with an insulating end.

2. A power battery thermal management system of a large flat heat pipe coupled with a topology optimized cold plate according to claim 1, characterized in that: The large flat heat pipe group consists of a first flat heat pipe and a second flat heat pipe, which are symmetrically arranged. The first flat heat pipe is arranged on one side of the battery pack, and the second flat heat pipe is arranged on the other side of the battery pack. The first flat heat pipe and the second flat heat pipe are both provided with a liquid wick, a support column and a fixed structure inside. The support column is used to enhance the structural strength of the large flat heat pipe group, and the fixed structure is used to stabilize the liquid wick.

3. A power battery thermal management system of a large flat heat pipe coupled with a topology optimized cold plate according to claim 2, characterized in that: The preparation process of the liquid absorbent core is as follows: a core material after chemical oxidation is selected as the material of the liquid absorbent core, and then the liquid absorbent core is placed in a reducing environment at 200°C and containing hydrogen or ammonia for 2 hours to form a firm oxidation layer of a plurality of strip-shaped worm aggregates on the skeleton surface of the liquid absorbent core, wherein the size of the strip-shaped worm aggregates is 10 μm to 20 μm.

4. The power battery thermal management system of a large flat heat pipe coupled with a topology optimized cold plate according to claim 1 is characterized in that: The topology optimized cold plate group consists of a first topology optimized liquid cooling plate and a second topology optimized liquid cooling plate, the first topology optimized liquid cooling plate and the second topology optimized liquid cooling plate are symmetrically arranged, and the first topology optimized liquid cooling plate and the second topology optimized liquid cooling plate are respectively in contact with the condensation ends of the corresponding flat plate heat pipes.

5. A power battery thermal management system of a large flat heat pipe coupled with a topology optimized cold plate according to claim 4, characterized in that: The first topology optimized liquid cooling plate and the second topology optimized liquid cooling plate have the same structure, the outlet of the first topology optimized liquid cooling plate and the outlet of the second topology optimized liquid cooling plate are both arranged at the bottom end of the corresponding liquid cooling plate, and the inlet of the first topology optimized liquid cooling plate and the inlet of the second topology optimized liquid cooling plate are both arranged at the top of the opposite surface of the corresponding outlet or at the same side of the corresponding outlet.

6. A power battery thermal management system of a large flat heat pipe coupled with a topology optimized cold plate according to claim 5, characterized in that: The first topology optimized liquid cooling plate and the second topology optimized liquid cooling plate are both prepared by topology optimization, and the specific process is as follows: First, the variable density method is used to introduce virtual materials of different densities into the design domain of the liquid cooling plate. By adjusting the density value of the virtual material γ , change the regional flow resistance to optimize the flow path of the fluid in the liquid cooling plate and improve the heat dissipation efficiency, where 0≤ γ ≤1; the composite objective function obtained by weighted summation of the heat transfer performance index of the liquid cooling plate and the fluid power dissipation index is used as the optimization target; wherein the composite objective function is: ； In the formula, J is the composite objective function, and are the initial values ​​of fluid power dissipation and heat transfer performance index, is the weight factor, ranging from 0 to 1; in, is the fluid power dissipation index, and the calculation formula is: ； in, μ is the viscosity, u is the fluid velocity; is the reverse permeability, and the calculation formula is: ； In the formula, q is the penalty factor, and are the reverse osmosis rates of solid and fluid, respectively; is the heat transfer performance index, and the calculation formula is: ； in, T is the design domain unit temperature, γ is the density value, is the design domain area; Secondly, set the volume fraction is the constraint condition for topology optimization, which represents the maximum proportion of the fluid area in the entire liquid cooling plate and meets the requirements: ； The optimal value of the volume fraction is determined through multiple simulations and experiments; Next, determine the weight factor The optimal value of balances the emphasis of heat transfer performance index and fluid power dissipation index in the composite objective function to achieve comprehensive performance optimization of the liquid cooling plate; Finally, the composite objective function is iteratively calculated, and the density value of the virtual material is continuously adjusted during the iteration process to determine the minimum value of the composite objective function: ； In the formula, is the minimum value of the composite objective function, which is used to achieve structural optimization of the first topology optimized liquid cooling plate and the second topology optimized liquid cooling plate.

7. A power battery thermal management system of a large flat heat pipe coupled with a topology optimized cold plate according to claim 6, characterized in that: The volume fraction is the maximum proportion of the fluid area in the entire liquid cooling plate. The optimal value of the volume fraction is determined by numerical simulation and experimental research, specifically: first, numerical simulation is performed, and a liquid cooling plate model is established using finite element analysis software. Different volume fractions are set to simulate and record the flow channel pressure distribution, coolant flow rate, and battery pack average temperature; then, experimental research is performed to manufacture liquid cooling plate specimens with different volume fraction flow channels, and the specimens are tested under simulated power battery charging and discharging conditions to monitor the coolant flow rate, pressure loss, and battery pack temperature changes; finally, the numerical simulation results and experimental research results are combined. When the volume fraction is 0.5, the overall average temperature of the liquid cooling plate reaches the minimum value, so the optimal value of the volume fraction is determined to be 0.

5.

8. The power battery thermal management system of a large flat heat pipe coupled with a topology optimized cold plate according to claim 6, characterized in that: The weight factor is the proportion of the heat exchange performance index and the fluid power dissipation index in the composite objective function. The optimal value of the weight factor is determined by combining simulation and experiment, specifically: first, a simulation is performed, using software to simulate the performance of the liquid cooling plate under different weight factors, and the data of the average temperature of the battery pack and the pressure drop of the liquid cooling plate are recorded; then an experiment is performed to produce liquid cooling plate prototypes with different weight factors, and the tests are performed in a simulated power battery working environment to monitor the battery pack temperature, coolant flow and pressure changes; finally, the simulation data and experimental data are combined. When the weight factor is 0.6, the pressure drop change tends to be stable, and when the weight factor is 0.75, the average temperature of the battery pack reaches the minimum value, so the optimal value of the weight factor is 0.75.

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