Design And Optimization Of Liquid Cooling System For Battery Pack Of Electric Bus

With the development of economy and urbanization,vehicles have become the first choice for people to travel,but with the shortage of oil and the pollution of traditional fuel vehicles to the environment,it is necessary to develop electric vehicles.The core component of electric vehicle is power battery,and temperature is the main factor affecting the performance of power battery,so it is necessary to design battery thermal management system,maintaining temperature is at 25℃～45℃.In this paper,Yutong E10 pure electric bus power battery pack as the research object,according to the design requirements of battery thermal management,research and optimize the cooling structure of the battery pack.This paper mainly focuses on the thermal management of the battery,and the battery will generate heat,so it can meet the requirements of cooling in summer and heating in winter.Considering the cost and cooling effect,this paper adopts the method of liquid-cooled cooling,designs and analyzes the cooling system of the battery pack of electric bus.This paper analyzes the physical model and working principle of lithium-ion battery and the heat generation and heat transfer principle of lithiumion battery;Besides,calculating the thermal parameters of lithium-ion battery and the rate of heat generation at different multiply,and laying the foundation for the subsequent simulation operation.Geometric modeling and thermal modeling of the battery for the electric bus and simulating the battery pack by ANSYS Fluent.And experiments to verify the simulation,the experimental values and simulation data for comparative analysis,to prove the correctness of the simulation.This paper mainly designs and optimizes the heat dissipation structure of the battery pack,so that the battery pack can meet the design requirements of the battery thermal management,and studies the influence of different cooling factors on the heat dissipation effect of the battery pack.To study the effect of different charging multiply,different ambient temperature and different rate of the charge influence the temperature of the battery pack.The study found that the higher the charging rate,the higher the battery temperature;The higher the ambient temperature,the higher the temperature of the battery.This paper studies the effect of single battery pack on the temperature of battery pack under different ambient temperature and different charging ratio.The results show that the higher the charging ratio,the higher the battery temperature;The higher the ambient temperature,the higher the battery temperature;The heat dissipation model of the battery pack was designed,and the temperature distribution of the battery pack under 1C,3C and 5C was simulated.According to the simulation results,the structure of the battery pack was optimized,and the single-in-and-single-out pipeline was changed into a double-in-anddouble-out pipeline.At the same time,a cold plate was placed on the side to simulate the temperature of the battery after the structure optimization.The temperature of the battery pack with optimized structure can meet the requirements of thermal design in working state.The influence of different cooling factors on the battery temperature was studied in the improved battery pack heat dissipation model.The results show that the increase of coolant flow rate has almost no effect on the battery temperature.The lower the coolant temperature,the lower the maximum battery temperature,but too low coolant temperature will make the battery pack temperature too low;The air convective heat transfer coefficient has little effect on the temperature of the battery pack.