Fin structure and liquid cooling to enhance heat transfer of composite phase change materials in battery thermal management system

In order to improve the performance of a battery thermal management system (BTMS) based on phase change material (PCM), expanded graphite (EG) is added to paraffin to form composite PCM (CPCM), and embedded aluminum fins are coupled with liquid cooling to enhance heat transfer. A heat generation model for lithium-ion batteries (LIBs) is established and verified by experiments. The cooling performances of four BTMS designs were simulated. The effects of the thermal characteristics of LIBs were investigated at various velocities and directions of coolant flow as well as EG fractions in CPCMs. The simulation results indicate that Design IV shows a good cooling effect at a coolant flow rate of 0.06 m s(-1) and an EG fraction of 12 wt%. Under ambient temperatures of 26 degrees C, 35 degrees C and 40 degrees C, the maximum battery temperatures are 28.14 degrees C, 37.15 degrees C and 42.09 degrees C, respectively, and the maximum temperature difference over the battery module is 1.88 degrees C, 1.89 degrees C and 1.92 degrees C, respectively. The charge-discharge cycle performances of the four BTMS designs were further investigated. In Design IV, the maximum temperature and the maximum temperature difference in the battery module remain unchanged during five cycles under 1, 2 and 3 C discharge rates. The new BTMS has significantly improved the secondary heat storage problem of PCMs and the temperature uniformity of LIBs. The fin structure combined with liquid cooling is efficient in enhancing the heat transfer of CPCM for battery thermal management.