Design Of Electric Vehicle Power Battery Thermal Management Liquid Cooling System

The report of the 19th National Congress of the Communist Party of China points out that the major social contradictions in the new era have been transformed into the contradictions between the people’s growing needs for a better life and unbalanced and inadequate development.With the improvement of people’s living standards,people’s demand for cars has increased sharply.In recent years,the problem of environmental pollution and energy shortage has become increasingly prominent.In order to make cars use cleaner energy,the electric vehicles,which came out in the 19th century,have been favored by people and developed vigorously.However,the key technical problem of electric vehicle is its core component,power battery.The energy density,cycle life and service performance of power battery restrict the performance of electric vehicle and affect the development and application of electric vehicle.The decisive factor that affects the performance of the power battery is its working temperature.When the power battery works under low or high temperature for a long time,its chemical performance,service life and endurance mileage will be greatly reduced,and even thermal runaway will occur in serious cases,leading to electric vehicle fire.Therefore,it is of great theoretical and practical significance to study the thermal management of the power(lithium ion)battery module,in which the study of the heat pipe channel structure has a key impact on the temperature control and temperature consistencyThis paper takes lithium iron phosphate battery as the research object,and adopts liquid cooling system to dissipate heat.According to the working principle and heat transfer characteristics of the power battery,the thermal model of the battery is established,and the temperature field of the battery module is simulated.The influence of the cooling plate structure,size and position distribution on the temperature of the battery module was studied,and the effectiveness of the cooling effect was verified through experimental and theoretical analysis.On this basis,a new type of cooling plate with flow channel variable structure was designed,which could effectively improve the cooling capacity and temperature uniformity.Its main contents are as follows:(1)The working principle,structural characteristics and heat transfer characteristics of lithium iron phosphate batteries were studied in detail.The characteristics related to the internal resistance of lithium iron phosphate batteries were summarized according to a large number of previous experimental conclusions.Then the software Fluent was used to establish the thermal model of the battery module,set the relevant boundary conditions and thermal physical parameters,and carry out simulation calculation.The surface temperature distribution of the battery module under different discharge rates was obtained.The research results showed that the higher the discharge rate,the higher the temperature of the battery surface.(2)The design and research of the key cooling parts(cooling plate)of the liquid cooling system are carried out.On the basis of the traditional cooling plate channel structure,a new variable structure channel design is adopted,and then the liquid cooling simulation model of lithium iron phosphate battery is established for six different cooling plate structures.The cooling effect of different channel structures is analyzed through simulation comparison,and the outlet width of the channel and the symmetry of the channel and position of the cooling plate are simulated.The results show that the new variable structure channel has better heat dissipation effect than the traditional channel structure,and can make the lithium iron phosphate battery work in the appropriate temperature range,and ensure the maximum temperature difference of the battery module is not more than 3℃;in addition,reasonable channel outlet width,reasonable cooling plate channel and location layout can further enhance the heat dissipation capacity of the liquid cooling system.(3)Set up the experimental platform of liquid cooling system.Firstly,the heat dissipation effect of the battery thermal management liquid cooling system with variable structure runner design and symmetrical layout of cooling plate was experimentally studied Secondly,the feasibility analysis and performance evaluation of the control strategy of the thermal management liquid cooling system are carried out.The experimental results show that the experimental data is similar to the simulation data,and the design of flow channel structure and control strategy is reasonable and feasible.