CFD-Based Performance Evaluation of Immersion Cooling Fluids for Lithium-Ion Battery Modules

Lithium-ion batteries (LIBs) are critical components in electric vehicles (EVs) and renewable energy systems. However, conventional cooling techniques for LIBs often struggle to efficiently dissipate heat during fast charging and discharging, potentially compromising performance and safety. This study investigates the thermal performance of immersion cooling applied to an Electric Vehicle (EV) battery module comprised of NMC-chemistry-based cylindrical 21700 format Lithium-ion cells. The effectiveness of immersion cooling in reducing maximum cell temperature, temperature gradient, cell-to-cell temperature differential, and pressure drop within the battery module is evaluated on a detailed 3D model of a 360-cell immersion-cooled battery module that was developed, incorporating a well-established heat generation model based on theoretical analysis and experimental data to simulate the thermal characteristics of the battery system . The effects of the different fluid properties are first assessed, resulting in higher heat transfer coefficients with lower fluid viscosity values and high specific heats. Density and thermal conductivity effects are also obtained. Subsequently, a set of different fluids are introduced into the model to obtain which one returned the best thermal performance. Results demonstrate that under transient operating conditions, such as a WLTP driving cycle, the temperature increase of the cells remains limited, resulting in minimal differences in performance between the tested fluids. However, under more demanding scenarios, such as fast charging and high C-rate, significant differences in thermal performance among the fluids emerge. These findings enhance our understanding of battery immersion cooling technology and provide novel insights for optimizing battery thermal management systems through computational fluid dynamics (CFD).