| As a clean, efficient, and low-pollution new energy vehicle, electric vehicle has a greatdevelopment all over the word. However, when compared with conventional vehicles, thereare big challenges for the limitation of power battery technology, such as driving range,acceleration and climbing performances, etc. Therefore, high power, high capacity and highsecurity are development direction of power battery nowadays.The technology breakthrough of power battery has a lot of limitation from externalconditions, especially temperature condition. Good operation temperature is the promise forbattery to work safely and efficiently. This paper mainly researches three aspects of thethermal management of power battery: battery cell, battery module and battery pack. Thesubjects range from the internal structure simplification of battery cell to the liquid coolingstructure design of battery module and the whole model construction of battery pack.The model simplification and thermal characteristics analysis of battery cell consists ofdismantling experiment and simplify model of actual battery cell, and summarization of thematerial property of each section and thermal power of heat source parts at differentdischarge rate. The correctness and practicability of simplified model was validated byexperimental data. The error between simulation data and experimental data was below10%at the stage of charge and discharge. The temperature variation of battery cell was calculatedby CFD software in different situations, and the results indicated that the maximumtemperature point inside battery located in the lower part of battery internal center, while thesurface temperature is far below the internal maximum temperature. The maximumtemperature and surface heat transfer-coefficiency increased differently with the incrementof the discharge rate. The maximum temperature of the battery cell can reach40℃whendischarge rate greater than1.93C，and which can also reach40℃if the discharge rate is5Cand environment temperature is10℃.The maximum temperature can reach60℃if theenvironment temperature is30℃and the discharge rate is5C.The influence of radiation heat transfer and thermal contact resistance to battery thermal characteristics was analyzed in thispaper, and the results indicated that the influence from the radiation heat transfer isinconspicuous at low discharge, but the influence of thermal contact resistance toheat-producing capability of battery cell can’t be ignored. The results indicated the maximumtemperature inside the battery cell can increase39.03℃with5C discharge rate comparedwith the condition that without considering the contact thermal resistance。For the battery module liquid cooling structure design, prototype liquid cooling modelwas constructed according to the original air cooling model. The heat dissipation effects oftwo different cooling models at constant discharge rate were compared accordingly. Theresult shown that the liquid cooling model can control the maximum temperature of theoriginal model below40℃and the maximum temperature difference inside module below5℃，while the air cooling model can’t realize the ideal cooling performance, the maximumtemperature and temperature difference inside modules are beyond the ideal operation range.Four structures were designed to optimize the cooling effect, and the flow and heat transfercharacteristics of the four liquid cooling structure models were compared and analyzed. Theresults showed that, in the constant inlet velocity condition, the inlet and outlet pressure dropof whole cooling system of parallel structure was the1/9of the prototype or so, and themaximum temperature was controlled at40℃or so, and the maximum temperaturedifference was below3℃. The practical model was built based on the parallel coolingstructure, and was optimized according to the inner space size of battery pack, eventually,the best performance structure model was obtained.In the process of the whole model building of battery pack, the whole model based onthe size of electric vehicle trunk was designed, which expounded the advantages of eachsection inside module. Finally, the internal flow characteristics of the dual-battery andfour-battery module group inside battery pack were analyzed. |
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