| In today’s world,energy shortage and environmental degradation are becoming more and more serious.Promoting sustainable energy revolution has been quickly put on the agenda.During the period,the development of sustainable green energy as the center of the goal requires the establishment of a more sustainable,efficient and environmental protection of the new energy system,new energy vehicles as a key link of its development system gradually attracted attention.According to the development status of new energy vehicles,the power battery,as its core component,has been curbing the development of new energy vehicles due to problems such as safety,stability and energy density.In terms of power batteries,lithium-ion batteries are widely used in electric vehicles due to their advantages of high energy density,long cycle life and low self-discharge rate compared with other batteries.However,the electrochemical performance of lithium batteries is severely constrained by the operating temperature,and it is easy to accumulate heat in the rapid charging and high intensity discharge,which leads to thermal runaway.In view of this problem,the thermal management system based on forced air cooling can provide a feasible cooling scheme for the pure electric/hybrid electric vehicles with moderate energy density or equipped with lithium iron phosphate batteries when the vehicle design space is tight or the lightweight requirements are high.Therefore,it is very important to design an efficient thermal management system to control the temperature of batteries.In this paper,the lithium-ion battery pack as the research object,combined with experimental methods and numerical analysis,in order to solve the problems of high temperature and poor temperature uniformity of vehicle Lithium-ion battery pack,a T-type battery thermal management system based on forced air cooling is designed.Firstly,a commercial square lithium iron phosphate battery was selected,and the charging and discharging test platform of the single battery was built according to the heat generation and heat transfer mechanism of the battery.The voltage and temperature rise characteristics of the battery under different charging and discharging rates and ambient temperature were experimentally studied,and the key thermophysical parameters of the battery were obtained from the single heat generation experiment,and the thermal simulation model of the battery was established.Then,the concept design of symmetrical T-type system based on parallel air cooling is proposed,and the air cooling experiment of T-type system is designed to explore the influence of different discharge rate and air inlet speed on the temperature rise and temperature uniformity of battery pack.Based on the experimental process,the CFD numerical model of lithium battery pack is established,and the reliability of CFD model method is verified by comparing the experimental results.In addition,natural convection and forced air cooling are compared to highlight the heat dissipation efficiency of forced air cooling.After confirming that the cooling performance of T-box is better than Z-type and U-type box,the influence of the structure parameters of the T-type heat dissipation system on the thermal performance of the battery pack is studied.Five optimization schemes of the top inclination of the box are designed to discuss the heat dissipation effect of different schemes.Then,the optimal model with good comprehensive performance is obtained by orthogonal test,taking the maximum temperature,maximum temperature difference and power consumption of the battery as the optimization target,taking the structure parameters of the inlet and outlet as the design factors.Finally,the internal heat dissipation optimization of T-type system after the optimization of the box is carried out,the thermal characteristics of different battery layout directions and battery quantity are analyzed,and the two parallel optimization schemes are analyzed.Scheme 1 obtains the optimal strategy of outer channel to install diaphragm and adjust the spacing of the middle channel after analyzing the cooling channel;scheme 2 uses multi-objective optimization algorithm to find the best parameters of 4 baffles for the baffle.In conclusion,the research results of this paper can provide an effective reference for the battery thermal management system under the forced air cooling strategy. |
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