Investigation of thermal properties of phase change materials for novel hybrid thermal management strategies for cylindrical Li-ion cells

This paper introduces two novel hybrid thermal management strategies, which use secondary coolants (air and water) to extract heat from a phase change material (paraffin), resulting in increased heat extraction capability of the paraffin and the overall thermal performance of the battery module. In the first strategy, a novel configuration is designed in which the vertical cylindrical fluid cooling channels are placed between the paraffin, and the air is forced through the duct at the top of the battery module. In the second strategy, a novel cold plate design is developed, which replaces the fluid cooling channels and is placed between the rows and columns of the cells. The cold plate contains a single fluid body to improve the thermal performance of the battery module. Experimental and numerical studies are conducted to analyze the proposed strategies. The experimental studies were conducted to obtain the temperature and heat flux profiles of the battery module. Moreover, a numerical model is developed and validated using the experimental data obtained. At a high discharge rate of 7C, the numerical results showed that the highest cooling was achieved through the second strategy as the maximum temperature was limited to 27.8 °C, and a high temperature uniformity was achieved by the end of the discharge cycle with the temperature difference limited to 0.4 °C. Additionally, various composite phase change materials with performance enhancing materials were investigated. It was found that there is no significant reduction in the maximum temperature beyond the thermal conductivity of ∼ 3 W/m.K (which corresponds to the thermal conductivity of paraffin base with copper foam). Therefore, the proposed strategy eliminates the requirement of a pump and reservoir since there is no liquid flow within the battery module. This reduces the energy required for the operation of the thermal management system, thereby increasing the available energy for propulsion.