| New energy electric vehicles do not consume fossil energy and have no exhaust emissions,which is an important way to effectively solve the two major problems of energy shortage and environmental pollution.As one of the three major components of new energy electric vehicles,the performance of the power battery directly affects the range and safety of electric vehicles.If the heat cannot be transferred to the external environment in a timely and effective manner,the power battery capacity will be irreversibly lost and the risk of internal short circuit will be increased,or the power battery will suffer from thermal runaway and cause fire and explosion.Therefore,the research of efficient thermal management system plays an active role in the performance,service life and safety of power battery.In this paper,an efficient thermal management system with coupled liquid cooling and composite phase change material is proposed,and the thermal performance of the thermal management system is mainly studied from different design parameters.(1)The structure,working principle,heat production mechanism and heat transfer mechanism of the single cell battery are analyzed theoretically,and the internal resistance and open circuit voltage temperature coefficient combined with the heat production rate equation in the literature experiments are cited to establish the three-dimensional heat production model of the single cell power battery.The differences between the numerical simulation results and experimental results are compared and analyzed to ensure the accuracy and reliability of the numerical simulation of the three-dimensional heat production model of the single cell battery and to provide a basis for the subsequent design of the battery pack.(2)The simplified three-dimensional model of the battery pack is established based on the assumptions,the coolant and phase change material applicable to the thermal management system are selected,and the flow rate of the coolant and the amount of phase change material are initially determined.The finite element model of the battery pack is established,and the parameter settings and mesh size for numerical simulation calculation are determined to prepare for the numerical simulation.(3)Numerical simulation analyzes the influence of different design parameters on the heat dissipation performance of the thermal management system.The conclusions that are of reference value for the design of the battery pack cooling system are drawn:when the thickness(d)increases from 1 mm to 4 mm,the maximum temperature decreases by 7 K,the temperature difference decreases to 3 K and the liquid phase rate decreases to 59%,and the composite phase decreases.The increase in the thickness(d)of the composite phase change material(CPCM)can improve the temperature uniformity of the battery pack;the increase in the number of cooling pipes(n)expands the contact area with the CPCM,which is beneficial to the use of the CPCM in the liquid cooling system.For heat exchange,the liquid phase rate decreases from 90%to 70%;when the inlet flow rate increases from 0.01 m/s to 0.06 m/s,the effect on the temperature rise of the battery pack is small,and the control of the liquid phase rate is more Significantly,it decreased from 93.49%to 74.16%;the temperature difference between the alternating flow of coolant in adjacent cooling pipes was reduced to 4.86 K,which significantly improved the temperature unevenness at the inlet and outlet sides of the battery pack;the lower the inlet temperature,the stronger the heat dissipation performance of the battery pack,and the appropriate The increase of the inlet coolant temperature can improve the temperature uniformity of the battery pack and improve the latent heat utilization rate of the CPCM.(4)The four factors of CPCM thickness(d),number of cooling tubes(n),flow rate(v)and inlet temperature(Tin)were analyzed based on fuzzy gray correlation on the degree of influence on the maximum temperature,temperature difference and liquid phase rate.The results show that the thickness of CPCM(d)has the largest values of 0.8154,0.8004,and 0.807 for the three,respectively,indicating the greatest degree of influence,followed by the number of cooling tubes(n)and inlet temperature(Tin),with the lowest influence of flow rate(v).Therefore,for liquid cooling system,the flow rate(v)can be reduced appropriately to reduce the energy consumption.In this paper,the study of liquid-cooled-CPCM coupled thermal management system can meet the heat dissipation demand of the battery pack at 5C discharge rate,showing the powerful heat dissipation performance of the liquid-cooled-CPCM coupled system.To realize the new energy electric vehicles fully charged in a short time,it becomes possible to slow down the congestion of charging stations.It also responds quickly to the heat dissipation needs of nextgeneration higher-capacity and higher-energy-density power batteries,ensuring that the power batteries operate in the appropriate temperature range. |
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