Enhanced cooling of Lithium-ion battery modules using Al₂O₃ Nanofluid: A numerical study of thermal–hydraulic trade-offs

Lithium-ion batteries are widely utilized as efficient energy storage devices due to their ability to operate at high power levels while maintaining stability and reliability. However, a significant limitation in practical applications is the heat generation that occurs during both charging and discharging processes, which can adversely affect performance, safety, and lifespan. The implementation of nanofluid coolants is a well-established method for enhancing thermal performance in cooling systems. Unlike most previous studies, in which the thermophysical properties of the base fluid were assumed to be temperature-independent, this study employed a three-dimensional computational fluid dynamics (CFD) model developed in ANSYS Fluent to investigate the effectiveness of immersion cooling for the thermal management of a 12-cell battery module using a single-phase oil-based Al ₂O₃ nanofluid, while considering temperature-dependent thermophysical properties of the base fluid. Pure oil and Oil/Al 2 O 3 nanofluid were compared to evaluate the impact of nanoparticle concentration. Three distinct volume fractions were tested. Immersion cooling was also assessed. Three maximum Reynolds numbers were considered: 100, 200, and 300. The findings demonstrated that an increase in nanoparticle concentration from 0% to 4% significantly enhanced heat transfer, yielding an approximate 37% improvement in both the average convective heat transfer coefficient and the average Nusselt number. While higher nanoparticle volume fractions resulted in an increase of approximately 93% and 150% in pressure drop and hydraulic power requirements, respectively, regardless of the maximum Reynolds number, Performance Evaluation Criterion showed an approximately 11% increase at Re D , max = 200 and φ = 0.04. These results indicate that although the use of nanofluids as coolants can be an effective strategy for enhancing battery thermal regulation, it may not be the most effective strategy.