Optimization Of Thermal Management Structure For Battery Pack In Pure Electric Logistics Vehicles

In recent years,the domestic pure electric vehicle industry as a whole has developed rapidly,but battery performance,one of the most important technical bottlenecks,restricts the development of pure electric vehicles.Temperature is one of the main factors of battery performance.Too low battery temperature can make the resistance of battery increased and the battery capacity significantly reduced,and excessive battery temperature can cause to spontaneous combustion or even explode of the battery pack.Therefore,in order to ensure the power and safety performance of pure electric vehicles,a set of effective power battery group and thermal management system must be designed for the battery pack.In this paper,taking a type of square lithium-ion battery produced by a company as an example,the thermal characteristics of single cell and battery pack were investigated with the methods of theoretical analysis,numerical simulation and actual experiment.A new structure of temperature-controlled plate is proposed and optimized for better temperature uniformity of battery pack.The main contents are as follows:Based on the domestic and foreign researches related to battery thermal management,the research and application status of thermal management were analyzed,the advantages and disadvantages of various thermal management methods were summarized and the goal of thermal management was determined.The mechanism of heat generation of the battery was analyzed,and its structure,thermo physical parameters and heat generation characteristics were studied.The resistance of each part of the battery was obtained by the HPPC test of single cell and the impedance test of positive and negative electrodes.And the corresponding numerical model of battery was established by using CFD software.By comparing the results between simulation and experiment,the maximum temperature difference at the same measuring points did not exceed 0.7?,which verified the validity of this numerical model.In consideration of the existing battery pack structure,a set of thermal management system based on parallel temperature-controlled plates of multi-port extruded tubes was designed.The experimental platform of the battery pack was built,where batteries were replaced with silicone rubber heating sheets,and the corresponding numerical model was established.Since the error of simulation and experiment was less than 5%,the validity of numerical analysis was verified.Through the simulation of the heating and cooling conditions of the thermal management system,it was found that the overall temperature difference of the battery pack exceeded the thermal management target and the system needs to be optimized.In order to optimize the thermal management system,a new parallel-channel temperature-controlled plate was designed.The temperature-controlled plate in the length of the channel was divided into three sections,and the channel number s in the direction of flow increased in turn.A short channel and block were set up on the inlet side of plate to enhance flow uniformity.Moreover,the channel numbers of each section was optimized by numerical simulation,so that the temperature difference along the temperature-controlled plate decreased.Finally,the overall battery pack temperature difference was less than 5?,which achieved the thermal management of the design goals.