Design And Analysis Of Thermal Management System For Lithium Battery In Hybrid Electric Vehicle

In today’s increasingly severe energy consumption,the application of new energy technologies is the mainstream of the development of the times.For the vehicle industry,new energy vehicles to replace traditional fuel vehicles is also imperative.No matter which form of new energy vehicles,all need power batteries as the core components of new energy vehicles.Power batteries made up of lithium-ion batteries have many advantages and are widely used.However,lithium-ion batteries must work at the right temperature to give the best performance and are not easily generated safety problems.Therefore,it is critical to design an effective thermal management system to ensure that the lithium battery is in the proper operating temperature range.In this project,numerical simulation of a single ternary lithium battery,design of a battery pack and design of a battery thermal management scheme with multifield coupling numerical calculations are carried out for a PHEV plug-in hybrid passenger vehicle.The main study and conclusion of the paper are as follows:(1)By establishing the electrochemical-thermal coupling model of lithium battery,the thermal characteristics of the monolithic ternary lithium battery under different ambient temperatures are analyzed,and the variation law of the heat generation rate of the monolithic lithium battery under different discharge multipliers is obtained.(2)The electrical design of the power pack is carried out based on the performance parameters of the PHEV hybrid vehicle and the requirements of the power performance.The number of batteries required,the form of series and parallel connections are determined,and the dimensions of the battery box and the internal battery modules are selected according to the international requirements.(3)The design of a typical battery module liquid cooling system is carried out,including the selection of materials for the liquid cooling plate,the selection of coolant,and the design of coolant flow channels.The multi-field coupling model of the battery liquid cooling system is established,the temperature distribution of the battery pack is analyzed,the cooling flow channel is improved,and finally the cooling flow channel is designed in the form of dual flow channels.The heat transfer characteristics of the liquid cooling system under different coolant types and different cooling flow rates are analyzed,and the results show that propylene glycol is the better coolant,and the more suitable coolant flow rate is 0.14 m/s.At this time,the maximum temperature of the battery pack is 29.14 ℃,and the temperature difference is 3.95 ℃.(4)The design of a new heat pipe cooling based thermal management system is proposed,and the design of the heat pipe type thermal management system,including the design of the heat pipe,the design of the cooling plate and the design of the fins.A multi-field coupling model of the battery heat pipe thermal management system is established,and the temperature distribution of the system and the battery pack is analyzed.where the space occupied by the heat pipe is considered as an isotropic solid with an equivalent thermal conductivity of 15700 W/(m?K).The results show that the number of fins is more suitable at 20,the fin spacing is better at 6 mm,and the inlet air temperature at the fin inlet is more suitable at 25 °C.At this time,the maximum temperature of the cell is 31.03 °C and the temperature difference is 3.67 °C.Comparing the two thermal management schemes,the results show that although the temperature rise of the battery pack under the liquid cooling scheme is smaller,the temperature difference of the battery pack under the heat pipe scheme is smaller,with better temperature homogeneity and more reasonable temperature distribution.In summary,this paper provides a novel heat pipe based thermal management scheme for PHEV hybrid vehicles and evaluates the performance of the heat pipe thermal management system through a detailed multi-field coupled numerical simulation study.The novel thermal management scheme and model evaluation method proposed in this paper can provide a reference for future research on the thermal management of Li-ion battery packs for hybrid electric vehicles.