| With the emergence of energy crisis and environmental pollution problems,as large industry of global carbon emissions,emission reduction and sustainable development of the automotive industry has been attracted more and more attention.The development of new energy vehicles with low energy consumption and low emission has become the way to realize the sustainable development of the automobile industry.However,the safety performance of the power battery is an important factor that restricts the development of electric vehicles.Based on the influence of thermal safety of power batteries on vehicle performance,the thermal characteristics of Li-ion batteries are studied by numerical simulation and experimental research in this paper,The heat transfer characteristics of the system with mini-channel liquid cooling,phase change material cooling and mini-channel/phase change material cooling are also studied.The main contents and conclusions of are as follows:?1?Aiming at the heat production characteristics of LiFePO4 Li-ion battery,the temperature change of battery at different discharge rate is studied experimentally.Then,the internal resistance of LiFePO4 Li-ion battery is tested by hybrid pulse method.So,the heat generation model of LiFePO4 Li-ion battery is established and the heat transfer and distribution are studied.The results show that the temperature increases with the increase of discharge current.When the discharge rate increases from 1C to 2C and 3C,the maximum temperature of lithium-ion battery increases from 38.8? to 47.2? and52.3?,respectively.The main reason is that the discharge rate of LiFePO4 Li-ion battery increases,and the heat production increases due to the discharge current of the battery.At the same time,LiFePO4 Li-ion battery produce more heat in the initial and final stages of discharge,which is due to the larger resistance of the batteries in these two stages.?2?Aiming at the problem of high temperature rise of LiFePO4 Li-ion battery in natural convection environment,a thermal management system based on liquid cooling is designed and the influence of the number of cold plate channels on the battery thermal management system is studied.The results show that when the number of cold plate channels are 3,6 and 9,and the mass flow rate is 7.2×10-3 kg/s,the corresponding maximum temperature of the battery are 38.95?,38.87? and 39.90? at 3C discharging,respectively.At the same time,the temperature and temperature difference of the battery can be controlled within 40 C and 3 C respectively when the mass flow rate of the battery is 1.8×10-3 kg/s and 3.6×10-3 kg/s at discharge rate of 1C and 2C under 6 channel.?3?In order to further reduce the energy consumption of pumps in liquid cooling system,a thermal management system based on phase change material cooling and phase change material/mini-channel cooling was designed.The thermal management characteristics of phase change material cooling and coupled cooling were studied respectively.The results show that the maximum temperature and the maximum temperature difference of the battery module can be controlled within 40.5? and2.4? by using the thermal management system of phase change material in a single charge-discharge cycle.When the battery pack is charged and discharged in multiple cycles,phase change material coupled with mini-channel has the best cooling performance when the the mass flow rate is 2×10-3 kg/s and the number of channels is6.The maximum temperature and the maximum temperature difference of the battery pack can be controlled within 40.1? and 1.4? during the whole charge-discharge cycle. |
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