In recent years, thermal management of Lithium-ion batteries has been taken into consideration due to their high heat generation rate. Passive thermal management systems using Phase Change Materials (PCM) can control the temperature excursions and maintain temperature uniformity in Li-ion batteries without using active cooling. These materials are widely used for cooling electrical elements and batteries. In this project, the mechanism of heat transfer, material properties, convection coefficient, and ambient temperature are studied. To understand the effect of each property on cooling, models with different properties are simulated. The heat capacity, the thermal heat conductivity coefficient and latent heat of PCM are studied in this project. The most effective one is conductivity. When the amount of this property exceed from 1 , PCM can control the temperature during melting process. After that, the amount of latent heat increase the time duration of melting and absorb more energy form battery for constant volume of PCM. The results of simulation with various heat capacities almost similar. The results show this property is not effective as that of conductivity or latent heat. For understanding the effect of air convection coefficient on cooling, a model with various coefficients (from adiabatic to convection coefficient equal to 30 ) was simulated and subsequent simulations in this work were performed using 10 . The rectangular, trapezius, quadratic and three-part quadratic profiles are tried to find the best one. The criterion for choosing best profile was the maximum temperature of system. Also, in each simulation the percentage of liquid fraction has been considered for comparison. At first, one volume for PCM must be chosen and during changing the profile, this amount must be fixed. For rectangular profile the thickness of PCM in side edges change and subsequently the upper edge change. In these simulations, PCM in upper corner of enclosure melt in final moments. So, the trapezius profile was selected and simulations with fix volume have been performed. Then the quadratic profiles were selected. The results of these simulations did not produce appropriate maximum temperature. So, the three-part quadratic profile chose for next step. This profile was like trapezius one with quadratic edges. These simulations had better results. All of these simulations have been done for two materials with different properties. It could be seen that in low conductive materials, PCM must be placed monotonous around battery. But for materials such as graphite composite with high conductivity, it’s better to place more PCM around adiabatic boundary. In the end, modeling of PCM with variable properties relative to temperature has been taken. In this model, convection heat transfer has been considered and contour of velocity, density have been display. Because of considering convection heat transfer, this model obtains more suitable thermal performance with lower temperature. Key Words: Thermal management, Phase Change Material (PCM), Suitable profile, Lithium-ion battery.
