Comparative analysis of optimum thermal management systems for battery modules comprising 32700 and 18650 LFP cells at equivalent power capacity level

Abstract

This study evaluates the immersion cooling performance of optimized modules consisting of forty-five 1.6 Ah 18650 cells and twelve 6 Ah 32700 LFP cells (total 230.4 Wh), using the corner-enhanced Latin Hypercube Sampling (LHS)-Multi-Objective Genetic Algorithm (MOGA) optimization under varying C-rates and flow rates based on thermal–flow criteria. A validated single-cell model provides the basis for module-level simulations. The results indicate that the optimized 18650 module achieves an 88.08 % reduction in pressure drop compared to its base design, accompanied by a slight increase in average temperature. The optimized 32700 module exhibits an 84.66 % decrease in pressure drop and provides a more uniform temperature distribution, despite a modest temperature rise. When compared directly, the 18650 module manages heat more effectively, while the 32700 module stands out with lower pressure losses and a smaller volume for the same power capacity. Under a 4C discharge rate and 0.1 kg/s flow rate, the average temperature in the optimized 18650 module reaches 303.18 K, whereas it stabilizes at 302.54 K under 1C and 0.001 kg/s. Corresponding pressure drops are 143.39 Pa and 1 Pa, respectively. For the optimized 32700 module, the average temperature under 4C and 0.1 kg/s is 307.03 K, decreasing to 304.11 K at 1C and 0.001 kg/s. Pressure drop values for this module are obtained as 64.73 Pa at 0.1 kg/s and 0.48 Pa at 0.001 kg/s. The findings confirm that cell and optimized design influence thermal behavior and flow resistance in immersion-cooled battery modules.