Research Of Miniature Flat Loop Heat Pipe On The Heat Dissipation Of Electric Vehicle Battery

Owing to the rapid development of vehicle industry, the environmental pollution andenergy shortage caused by vehicles has become much more evidence. Having the remarkableadvantage of high efficiency, energy saving, low noise, zero exhaust-emission, electric vehiclebehave outstandingly in the environmental protection and energy saving area. The energy andenvironment issues would be solved efficiently if the electric vehicle technology be fullydeveloped. As a critical one among the electric vehicle technology, the battery performancehas somewhat restricted the development of electric vehicle industry. Non-uniformity and toohigh of battery temperature have a negative effect on the vehicle efficiency and battery life.A series of experiments have been conducted to investigate the influence of differentfilling ratios on the start-up and heat transfer characteristics of Miniature flat loop heat pipe(MFLHP). The work is helpful for choosing an optimum filling ratio for a specific MFLHP.Furthermore, an innovative thermal management system using MFLHP coupled with Phasechange material has been applied to the temperature control of electric vehicle battery. Theinfluence of this new heat dissipation system on the maximum temperature and temperaturedistribution of battery have been researched. We can conclude from the experimental resultsand theoretical analysis that:(1) As for the Miniature flat loop heat pipe with pure water as working fluid I designed,the operating temperatures of MFLHP with inventory ratio of58.3%、63.6%and68.0%isrelatively lower and more stable at the same heat load. Below60W the MFLHP with fillingratio of58.3%showed a lowest operating temperature, above60W the one with68.0%waslowest.(2) At the same heat load, the loop thermal resistance of MFLHP with filling ratio of58.3%was lowest. Below60W the system thermal resistance of the one with58.3filling ratioshowed lowest. While above60W,63.6%’s showed lowest. The thermal resistance decreasedwith the heat load increasing. For the same MFLHP, the loop thermal resistance accounted forabout50%of the system thermal resistance. The hysteresis phenomena was not so apparent athigh heat load than that of low heat load.(3) At the same heat load under horizontal operation, the maximum temperature ofbattery based on the MFLHP plus PCM system was substantially lower than that of MFLHPonly system, and the temperature distribution was more uniform. The difference between thistwo systems under the vertical operation was less obvious than that of horizontal operation.The maximum operating temperature could be kept under55℃under vertical operation, and the temperature difference at the surface of battery could be kept under a safe range.(4) Under the condition of same orientation operation and heat load, as for the time spanof battery maximum temperature arriving at50℃, the coupled system took the longest,MFLHP system took the second longest, natural air cooling took the shortest. Under thecondition of same thermal dissipation system and same heat load, it took longer under verticaloperation than that of horizontal operation.