Immersion cooling performance of nanofluid in a cylindrical cell battery pack using two-phase numerical simulations for varying discharge rates: A comparative study

Immersion cooling is gaining attention as it does not involve complex flow channels within the battery, making it easier to manufacture a compact battery thermal management system (BTMS) for high-discharge cells that could limit the operation of the battery pack within the optimal temperature range. Initially, forced air cooling performance is studied for various cell arrangements, such as aligned, staggered, and diamond, to arrive at the optimal cylindrical cell battery pack arrangement. The staggered configuration provided the best overall performance with a reduction in maximum temperature and enhancement in Nusselt number of 3.6 and 20 %, respectively, for an increase in pumping power of 25 % at higher discharge rates than aligned. Further, the cooling performance of air is compared to de-ionized water and its nanofluid with Al₂O₃ nanoparticles for varying volume fractions (0.1% and 0.4%) and discharge rates (5.8 C, 3.9 C, and 1.9 C) for similar coolant volume and flow rate. At discharge rates of 5.8 C, a maximum reduction of 30 K and 12 K is obtained with nanofluid compared to air and de-ionized water, respectively, at a lower flow rate. A temperature homogeneity of 5 K is obtained with nanofluid even for a higher discharge rate (5.8 C).