Performance Analysis of Fin Geometry in Battery Thermal Management System

Effective thermal management is a critical prerequisite for ensuring the safety, performance, and operational longevity of lithium-ion batteries deployed in electric vehicles (EVs). This paper presents a computational investigation into the passive cooling of an 18650 cylindrical lithium-ion battery using axial fin structures under natural convection conditions. Five configurations are analysed: a baseline battery without fins, and four finned variants incorporating rectangular, I-shaped, trapezoidal, and T-shaped axial fins fabricated from aluminium. Three-dimensional geometric models were developed in CATIA and imported into ANSYS Fluent for transient Computational Fluid Dynamics (CFD) simulation under a 1C discharge heat generation rate. Thermal performance is evaluated based on battery temperature distribution, surrounding air temperature, and convective heat transfer coefficient. Results demonstrate that the T-shaped axial fin configuration achieves the lowest steady-state battery temperature of approximately 309 K — a reduction of 6 K relative to the unfinned baseline — and the lowest stabilised air temperature of 309.6 K. A subsequent material study on the best-performing geometry confirms copper as the superior fin material due to its higher thermal conductivity. The findings provide quantitative design guidance for passive, lightweight fin-based battery thermal management systems.