Research On Direct-cooling And Liquid Cooling Thermal Management Of Power Battery

As the power source of electric vehicle,power battery has been widely concerned.In recent years,users’ requirements for the range of electric vehicles have been increasing,and the energy density of batteries has also increased.Subsequently,the battery thermal management system faces greater challenges.Direct cooling technology is an emerging thermal management technology.Compared with the traditional liquid cooling and air cooling technology,it has the advantages of strong cooling capacity and less influence by external temperature.At present,it has formed a certain degree of commercialization.However,the disadvantage of direct cooling technology is high energy consumption and poor economy,which has a negative impact on the range of electric vehicles.In view of the coolant circulation usually exists in electric vehicles for cooling the motor and electronic control,this study proposed a dual-cooling thermal management control system based on direct cooling technology,aiming to retain the advantages of direct cooling technology while adding liquid cooling to improve operation economy.In order to explore the heat transfer characteristics and operation mechanism of direct liquid dual cooling and heat management,this paper studies the structure,rheological parameters and adjustment scheme under variable working conditions of dual-cooling thermal management.In this study,3d models of block battery module and cold plate were established and experimental verification was completed.The verification results show that the numerical research method is reliable.After that,for the configuration design of the dual-cooling cold plate,two basic configurations of the single layer cold plate and the laminated cold plate are proposed.After comparing the single layer cold plate and the laminated cold plate,it is found that the single layer cold plate can better play the cooling capacity of liquid cooling and direct cooling,and is more common in the use environment.The results show that the snake-shape cold plate has obvious advantages in both temperature drop rate and temperature uniformity.On this basis,the structural parameters of the snake-shape cold plate are further optimized,and the cold plate structure with 5 flows,flow passage width of 8mm,flow passage spacing of 50 mm is finally determined.The cold plate structure has good temperature drop and moderate liquid flow pressure drop,which can ensure the cold plate has good heat transfer characteristics and flow resistance characteristics.Based on the optimized cold plate structure,the effects of coolant and refrigerant flow rate,inlet temperature and initial battery temperature on the temperature field of the battery were investigated under different discharge rate and temperature consistency level as evaluation objectives.In terms of temperature drop ability,both of them have strong temperature control ability at low discharge rate.Under the condition of high discharge rate,direct cooling can ensure the cooling capacity,while liquid cooling can maintain the temperature level and reduce the temperature rise rate.By comparing different inlet parameters,it is found that flow rate regulation plays a major role in the direct cooling capacity,while the change of liquid flow temperature plays a major role in the liquid cooling capacity.From the point of view of temperature consistency,the temperature fluctuation is larger in the case of direct cooling,and the temperature fluctuation is smaller in the case of liquid cooling.Reducing the liquid flow rate,increasing the inlet liquid flow temperature and decreasing the initial cooling temperature of the battery can reduce the temperature difference between the top and bottom of the battery,reduce the temperature fluctuation of the battery and improve the temperature consistency.For different battery temperature thresholds in different cooling modes,it is recommended that the direct cooling temperature be higher than 40 ° C and the liquid cooling temperature be between 30 ° C and 40 ° C.Based on the research on the cooling capacity of different liquid flow under constant working conditions,the cooling schemes of variable liquid flow rate and variable cooling mode were proposed for the regulation and control method of double liquid flow cooling under linear variable working conditions.The results show that comparing different variable flow rate schemes,it can be found that adopting the flow rate regulation method of first fast and then slow can effectively improve the temperature consistency on the basis of ensuring the temperature drop ability.By comparing the adjustment scheme of variable liquid flow cooling mode,it can be found that the cooling mode of liquid cooling first and then direct cooling has better cooling effect.Through reasonable coordinated adjustment of cooling mode and flow change,the temperature drop can be ensured,while the uniformity of battery temperature can be improved,and the temperature fluctuation of battery can be reduced.Based on the direct cooling and heat management technology,this paper proposes a dual-liquid flow heat management system.On the basis of direct cooling,liquid cooling is introduced to reduce the energy loss in the heat management process.The research on the structure design and flow parameter control of direct liquid dualcold plate is carried out,which provides a new scheme to reduce energy consumption on the basis of ensuring the thermal safety of the battery.