Performance Improvement Of Thermal Management Systems Based On Phase Change Materials For Lithium-ion Battery

With the energy crisis threatening and environment pollution outstanding,the researching and development of electric vehicle is very important to enhance the energy utilization rate and decrease environment pollution.As the key component of electric vehicle’s power plant,lithium-ion battery is receiving more and more attention.However,when the battery is working,the heat that comes along can warm the battery and batteries’ temperature will varies in the pack,and which can reduce the batteries’ operational performance and life,more serious,can cause security incidents.So it is meaningful for improving the battery usability to analyse the battery temperature distribution in the working conditions by the way of numerical simulation,and design the thermal management system,optimize the performance of dissipate heat.The main content of this dissertation was summarized as follows:(1)The lithium-ion battery’s structural,working principle,and how to produce heat were analysed.Via the Bernardi-based model of heat generation rate,it is received that the heat generation of lithium-ion battery is related to the ohmic resistance and entropy heat coefficient.Then the battery was taken to do Peak Power and HPPC test,and it can received the curve about battery SOC-dependent the ohmic resistance and entropy heat coefficient.(2)Based on the heat transfer theory of battery,the battery thermal model was built.The thermal properties was calculated,and the UDF was written to realize the heat produce rate’s dynamic change in software of Fluent.The method of computational fluid mechanics was used to simulating the heat generation about battery’s discharge in 1C in natural convection.The results showed that the highest temperature of battery was surpassed the range in which the battery can keep the best working performance,and the difference in the temperature of battery is not small.When the batteries is applied in company,the thermal management system should be designed.(3)The phase change material(PCM)was applied to design thermal management system.Considering the influence of natural convection when the phase change material is melt,the thermal management system was simulated by the software of Fluent.The results showed that the thermal management system satisfied the demandsof battery in temperature.But there was still space to optimize.(4)Aim at the PCM influence on temperature of battery pack,the thermal management system was designed.An optimization design method based on CFD virtual experiments and orthogonal experiment theory,was used to optimize the five design factors,including porosity β and the other.It discovers the influence about the five factors to four test index,and the best thermal management system was received.