| Power battery is the core of new energy vehicles.Its performance restricts the improvement of new energy vehicles' quality.Battery temperature is an important factor in battery performance.When the battery temperature is too high,the electrochemical reaction may will risk out of control.When the temperature is too low,its performance is difficult to fully realize.When the battery temperature uniform is poor,battery life-span gets shortened and battery is easily damaged.Therefore,the efficient battery pack thermal management system is the key to the development of new-energy vehicles.First of all,the research on battery thermal management system by domestic and foreign scholars was learned to provide a reference for this study.Liquid-based thermal management system has high heat transfer coefficient and specific heat capacity.It can fully promote the battery temperature uniform.Therefore,this paper designed five kinds of indirect liquid-based heat transfer structure for flat and cylindrical battery with consideration of the lightweight,battery safety and temperature uniformity.The liquid flew in channel attaching to the battery pack.The design of fins indeed enhanced heat transfer between batteries and the liquid were used to transfer heat between these.This article studied heat transfer performance with influence of the flow paths,the fins geometrical structure and the material.By reducing the number of fins and using 0.5mm Thermal Conductor Graphite Strip(TCGS)to replace the fins and adding thermal conduction overlapping bushing structure with 0.025 mm TCGS,the heat transfer structure had been optimized.The charging and discharging system were selected for the battery pack.The liquid cooling experiment system was designed.The experimental bench was built.The evaluation index was put forward.To meet the experimental demands of data collection,matching,controlling and output,the Lab VIEW virtual system was applied to programming.This testing and monitoring system can achieve the function of experimental physical quantity real-time acquisition,displaying,processing,and storage and so on.As for exploring the sheet battery module performance,this article tested the battery heat generation and cooling performance at variable discharge rates and analyzed the temperature and rate influence of liquid inlet.To improve the thermal shock,the Cascade Cooling Method(CCM)has been raised.Then,the optimum selection of cooling fins has also been raised.The experimental results indicated that with the discharge rate increase the heat generation raised quickly,the cell cooling equilibrium temperature gained simultaneously,but the equilibrium time cost less.The balance performance and temperature consistency of battery at medium and low discharge rates behaved better than the high discharge rate.With the increase of inlet temperature,the cooling equilibrium time consumed less,the equilibrium temperature raised gradually and temperature consistency gained improvement.As the growth of liquid flow rate,the cooling equilibrium time cost a lot and equilibrium temperature descended.The light-weight upgrading of reduce the cooling fins number from 9 to 5,realized the mass and spatial conservation of nearly 45%.It could be concluded that the cooling performance and temperature consistency of battery at medium and low discharge rates behaved better than the high discharge rate.The cascade cooling method can efficiently improved the thermal shock and battery temperature consistency.With cooling fins replacement of the 0.5mm TCGS,the cell temperature difference,battery temperature consistency and the cooling equilibrium time consuming got promoted.The thermal conduction overlapping bushing structure with 0.025 mm TCGS can not only reduce thermal resistance,but also enhance the battery temperature consistency even at high discharge rates. |
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