Research On Integrated Thermal Management Technology Of Power Battery Based On High Efficiency Phase Change Heat Transfer Element

As the core component of electric vehicles,the performance of power battery directly affects the reliability and safety of electric vehicles.Too high or too low temperature conditions will lead to the reduction or even failure of the battery performance.Therefore,it is necessary to design and develop a safe and efficient thermal management system for power batteries.Face to the thermal management problems of small and large power battery modules,this paper proposes the integrated thermal management technology of power batteries based on the ultrathin vapor chamber and the three-dimensional heat pipe array,and analyzes the thermal management effect coupled with different heat dissipation methods.In this paper,an ultra-thin vapor chamber with a thickness of 0.8 mm was designed and fabricated,and a composite wick structure of sintered copper powder and copper mesh was proposed.In addition,a three-dimensional heat pipe array was designed and welded for the commercial large battery module.In order to solve the problem of long-distance heat transfer in power battery pack,three different splicing methods of long-distance heat pipes were designed and manufactured.In view of the working condition of the power battery,the heat transfer performance of high efficiency phase change heat transfer elements was tested experimentally.The results show that the vapor chamber with composite wick structure can start rapidly,and the surface thermal resistance is 0.05 ℃/W at 80 W heating power,and the anti-gravity heat transfer stability is better under the bottom cooling mode.In addition,the three-dimensional heat pipe array shows a good temperature uniformity in the anti-gravity heat transfer performance test,and the surface thermal resistance is 0.033 ℃/W at 100 W heating power.Finally,the heat transfer performance of three long-distance splicing heat pipes was analyzed,and the bending splicing method has the best uniform temperature effect.For small power batteries,this paper studies the heat dissipation effect of power batteries integrated thermal management system based on ultra-thin vapor chamber and water cooling under different discharge rates and cyclic charge-discharge conditions.The experimental results show that the maximum temperature drop of the battery surface is 16.2 ℃ and the temperature difference is kept within 5 ℃ under 3C discharge rate.In addition,the integrated cooling structure of the battery module can effectively reduce the internal temperature accumulation during the cycle of charge and discharge,and improve the heating rate of the battery surface at low temperature.For large power battery modules,the surface temperature rises and temperature difference of the thermal management system of power cell based on three-dimensional heat pipe array were compared in the mode of composite air cooling,water cooling and thermoelectric cooling.The heat pipe array composite water-cooling method shows the best temperature uniformity,and the highest surface temperature difference is 3.6 ℃;the combined water-cooling method of the thermoelectric cooler has the best heat dissipation efficiency,and the maximum temperature of the electrode is only 36.7 ℃.The heat transfer array based on bending splicing can transfer heat from the battery pack to the outside quickly for heat dissipation,but the thermal resistance at the splicing leads to the expansion of temperature difference between modules.