| In recent years,automobiles have increased rapidly in China,and the atmospheric environment has also been seriously polluted by automobile exhaust.To solve the crisis of energy and environment,electric vehicles have been vigorously promoted and developed rapidly as a substitute for traditional fuel vehicles.Driven by electricity,EV(Electric vehicle)contains a big amount of lithium-ion batteries,which are the core energy supply for electric vehicles.If the heat generated during charging and discharging cannot disspate in time,it will accumulate in the battery pack,leading to rapid temperature increase,reducing the endurance mileage,shortening cycle life and increasing the potential safety hazards.Therefore,the battery thermal management is the key to solve those problems.In this paper,the li-ion power battery thermal management has been studied in depth.The main contents are summarized as follows:(1)The current battery thermal management scheme and cooling effect for electric vehicle are summarized.The battery thermal models proposed by domestic and foreign scholars are summarized.The lithium-ion battery structure and working principle are studied.The DC internal resistance of lithium-ion battery at different rates and ambient temperature was tested by experiments.The dynamic internal resistance of the lithium battery was obtained.Combined with the battery heat generation model and experimental data,the simulated heat source function was obtained(2)According to the basic theories of heat transfer and computational fluid dynamics,a three-dimensional model of lithium-ion battery cells was established.The relevant thermal properties of lithium-ion batteries were obtained by consulting the literature.The battery discharge process was simulated by CFD software using the numerical simulation method,and the temperature distribution at the end of the battery discharge under different convection conditions and magnification was obtained.The results show that the peak temperature of the battery will exceed the optimal operating temperature range without cooling systerm.When used in groups,the battery performance will be reduced and the cycle life will be shortened.(3)A heat pipe-liquid cooling composite heat dissipation battery module is designed.The heat pipe is an L-shaped plate micro-heat pipe array.Through the fluid-solid thermal coupling simulation,the effects of air cooling and water cooling were compared.The influence of heat pipe distribution and contact area on temperature field was studied.The parameters of coolant type,coolant flow rate and number of cooling pipes were taken as variables.Setting module temperature difference as evaluation standard,the optimal parameter combination is obtained through orthogonal experimental analysis.The results show that there is a balance between economy and effect of coolant flow rate and number of heat pipes;The coolant temperature and the number of runners are the main factors affecting the maximum temperature and maximum temperature difference of the module;The use of an aluminum soaking plate between the heat pipe and the battery can effectively reduce the uneven temperature distribution.(4)According to the battery pack box size in practical application,the optimized battery module is composed into a battery pack,and the battery circuit connection scheme in the package is proposed.The structure and cooling scheme of the cooling module are designed.The temperature field distribution under different cooling schemes is obtained through simulation.By changing the heat pipe structure,the size of the soaking plate,the temperature of the coolant,the cooling effect is further optimized,and the temperature difference is reduced.Finally,the optimized discharge temperature field of the battery pack shows the effect of the cooling structure. |
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