Enhanced Thermal Management of Li‐Ion Batteries Using Forced Flow Immersion Cooling With Natural Ester Fluids for Electric Vehicles

ABSTRACT The growing adoption of electric vehicles (EVs) has heightened the demand for efficient thermal management in Li‐ion battery packs to ensure safety, performance, and longevity. Conventional liquid cooling techniques often fall short, prompting the use of sustainable alternatives like biodegradable dielectric fluids and advanced immersion cooling techniques. This study evaluates 1 kWh Li‐ion battery pack used in two‐wheeler EVs cooled via forced flow immersion cooling (FFIC) technique using natural ester fluids: sunflower oil (SFO), cottonseed oil (CSO), and canola oil (CAO), benchmarked against nonbiodegradable mineral oil (MO). A novel flow‐field design featuring triangular fins and modified wall structures is proposed to enhance heat dissipation and reduce pressure drop. Among the tested coolants, CSO in the modified design achieved the best thermal performance, reaching maximum pack temperature (MPT) of 35.3°C (≤ 5°C) and pressure drop of 981.25 Pa at 25 L/min—outperforming the standard design, which required 40 L/min and showed a higher pressure drop of 1767.03 Pa. The modified system also enhanced heat transfer coefficient to 102.40 W/m 2 K, compared to 86.12 W/m 2 K in the baseline case. The results highlight CSO as a superior eco‐friendly coolant and emphasize the significance of design optimization and fluid selection in advancing battery cooling for sustainable electric mobility.