| Environmental deterioration and the fossil energy crisis have become important factors restricting the development of the automobile industry,forcing EVs to go back to the historical stage.With the improvement of the battery capacity and quantity of the vehicle,the reliability of the power battery pack tends to be sensitive to temperature changes.Therefore,effective thermal management solutions are extremely weighty.In this paper,theoretical analysis,simulation and experimental study were combined for the research.According to requirements of lithium-ion battery under different conditions,combining with a single lithium-ion cell structure and thermal characteristics,a battery pack with a mini-channel thermal management structure was designed.The work done in this paper is divided into the following aspects:(1)The research progress of many kinds of liquid-cooling thermal management technologies were tracked.It is essential to apply liquid-cooling thermal management in the vehicle.(2)The battery charge and discharge mechanism and characteristic parameters were introduced.Three cooling ways of the battery were analyzed based on the basic theory of heat transfer and computational fluid dynamics.The structured hexahedral mesh and the SST k-omega turbulence model were selected.(3)The basic arrangement of the battery pack was completed depending on the requirements of vehicle performance and space size.Partial parameters were obtained from the equivalent model.The heat source was simplified,and the power density of the battery was calculated.The battery temperature raising under 0.5C and 1C discharge conditions were obtained.According to the requirements in high and low temperature conditions,the thermal management structure of the 2-battery-module was designed and checked,the inlet flow and heating power were determined.The reliability of the simulation results was verified by the comparison with theoretical results.(4)Applying simulation,the liquid-cooling-plate structure was optimized,and the performance was analyzed.Under the the same channel conditions of cross-section and length,the second structure was better with high performance of heat transfer and low pressure drop.When the total heat transfer area was constant,the heat transfer performance of the liquid-cooling-plate with 10-channel structure on one-side was better,the maximum temperature of battery core was lower than the others.For the above 10-channel liquid-cooling-plate,when the width of the outer channel was 2mm on average and decreased by 0.05 mm,the flow uniformity and heat exchange performance were better.The simulation results of liquid-cooling-plate performance in optimal structure were matched with the test results.Under high temperature and the 1C discharge conditions,the heat transfer performance of the liquid-cooling-plate with optimal structure was verified by the test method.(5)When the flow rate of single liquid-cooling-plate was 0.0974L/min,the flow uniformity was better,and temperature difference was much lower within 3℃.When the inlet and outlet were on the side of the battery pack,the internal space was larger and the pressure drop was higher.Under the high temperature condition,the heat transfer performance target could be reached,but under the low temperature condition,there was a certain degree of degradation.The heat exchanger,pump and heating plate were selected to meet the demands of heat exchange and flow cycle. |
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