Design And Numerical Simulation Of Cold Plate For Blade Lithium-ion Battery Thermal Management

In order to reduce greenhouse gas emissions,in response to the national"two-carbon"policy,the development of new energy vehicles has become a hot spot.Lithium-ion battery as the power source of electric vehicle directly affects the service life and safety of electric vehicle.Lithium-ion batteries will generate a lot of heat in the discharge process.If the battery is not dissipated in time,the battery performance will be affected in light,and the fire or explosion will occur in heavy.Therefore,the battery thermal management system（BTMS）to control the battery temperature is very necessary.Compared with traditional lithium-ion batteries,blade lithium-ion batteries have advantages such as high energy density,high space utilization rate and good safety,and are widely used in BYD Han,Skyworth HT-i,Hongqi E-QM5 and other models.In this thesis,the non-uniform runner design is proposed to solve the problem of uneven temperature of blade lithium-ion battery.In order to further reduce the temperature difference,the circuitous runner design is proposed.Finally,the thermal characteristics of blade lithium-ion battery modules are studied.The main contents of this thesis are as follows:（1）The length of blade lithium ion is several times that of ordinary square battery.How to ensure the temperature uniformity of blade lithium ion battery is the first problem solved in this thesis.To solve this problem,a parallel Z-runner design is proposed in this thesis.Compared with Z-channel,the flow rate of each sub-channel in parallel Z-channel is more uniform.Therefore,the maximum temperature of parallel Z-channel battery（302.2K）decreased by 2.1K compared with Z-channel battery,and the maximum temperature difference also decreased by 1.9K.Considering the non-uniform flow of parallel Z-channel,this thesis proposes the non-uniform flow channel design A and B,which further increases the heat dissipation area of the branch pipe with large flow.The maximum temperature of design B is reduced by 1.13K compared with the parallel Z-type design,and the maximum temperature difference is also reduced by 1.43K.In order to further improve the temperature uniformity of the cell,design C was proposed on the basis of design B,where ribs were added between branch pipe 1 and branch pipe 2,and the optimal parameter combination of rib length（l）,number of ribs（n）and width（w）was obtained as l=3 mm,n=4,w=2 mm.（2）The coolant flow direction of each sub-channel in design C is from top to bottom,so the upper temperature of the battery is generally low,while the lower temperature is high.To solve this problem,the design of circuitous runner is proposed to improve the temperature uniformity of the battery.The devious runner design strengthens the heat exchange of hot and cold fluids in different branch pipes,and the maximum temperature difference of the battery is 3.08K,which is 0.79K lower than the design C.Then,the effects of horizontal devious length d1 and vertical devious length d₂ are analyzed.The maximum battery temperature difference decreases with the decrease of horizontal devious length d₁ and increases with the decrease of vertical devious length d₂.When d₁=0 mm and d₂=40mm,the maximum battery temperature difference is the smallest.Finally,the optimum rib length（l）,number of ribs（n）and width（w）were optimized.l=3 mm,n=7,w=2 mm.（3）The circuitous runner design is applied to the battery module to further analyze the thermal management performance of the battery module.The thermal behavior of the battery module under side design of cold plate,co-direction design of both ends and reverse design of both ends is compared.Among the three designs,the maximum temperature difference is the smallest in the reverse design of the battery module at both ends.Therefore,this thesis considers that the reverse design at both ends is the better design among the three designs.Then the influence of aluminum plate thickness on both ends and between batteries is discussed.When the thickness of aluminum plates at both ends of the battery exceeds 3 mm,the maximum temperature and temperature difference are less affected.The maximum temperature difference between battery modules first decreases and then slightly increases with the increase of aluminum plate thickness between cells,so the optimal aluminum plate thickness between cells is 4 mm.