CFD Analysis of Sequential Dual-Layer PCM Thermal Management for a Cylindrical Li-Ion Battery Using RT-35 and RT-42

Abstract

Lithium-ion batteries are widely used in electric vehicles; however, their performance and safety are extremely sensitive to temperature increases during operation. Excessive heating can lead to thermal instability and thermal runaway, making effective thermal management critical. In this study, a transient Computational Fluid Dynamics (CFD) simulation of a dual-layer phase change material (PCM) cooling system for a cylindrical lithium-ion battery was performed using ANSYS Fluent 2024 R1. The model used the solidification and melting technique. RT-42 was employed as the inner PCM layer while RT-35 formed the outer layer in a concentric design. The battery core generated 726,000 W/m³ of heat during a continuous discharge of 12 W. Simulations were run for 1800 seconds. The creative element of this work is the sequential arrangement of dual layer PCMs with distinct melting ranges to achieve staged thermal regulation. The new aspect of this study is the unique dual-layer PCM arrangement, in which RT-42 is placed directly around the battery surface and RT-35 forms the outer annular layer. This arrangement allows sequential heat regulation during battery utilization. The temperature-time profile revealed two unique inflection points, representing the melting of RT-42 and RT-35, respectively. CFD-Post contour plots at t = 1800 s showed an active mushy zone near the battery-RT-42 interface, confirming latent heat absorption during phase change. A temperature drop of about 30 K was obtained between the battery core (435 K) and the outer RT-35 wall (405 K). This research demonstrated the effectiveness of the multi-stage passive thermal resistance concept for cylindrical lithium-ion cells under continuous discharge conditions.