Thermo-fluid and structural optimization of hybrid air-assisted CPCM battery thermal management for electric vehicles

• Developed a fully coupled conjugate heat-transfer model for hybrid air-assisted CPCM BTMS • Systematically optimized PCM thickness (2–4 mm) for thermal–structural balance • Conductivity-enhanced CPCM significantly suppressed peak temperature at 3C discharge • Experimental results validated CFD predictions within ±1°C deviation • Integrated thermo-mechanical assessment confirmed structural reliability of optimized design Batteries are the core of Electric Vehicles and must function under extreme conditions, requiring effective heat recovery systems for optimal performance. This work explores a hybrid air-assisted Composite Phase Change Material (CPCM) battery thermal management system to extract heat from battery modules (BM). Paraffin wax is placed around the battery pack with various thicknesses 2 mm, 3 mm and 4 mm respectively. A detailed computational fluid dynamics investigation was carried out at various discharge conditions (1C, 2C, and 3C) with an air inlet velocity of 4 m/s. After implementing PCM into the battery modules, a maximum temperature of approximately 29.04°C was observed for 2 mm thickness PCM at 3C conditions. Similarly, for BMs with 3mm and 4mm thickness PCM, the higher temperature of about 34.6°C and 35.9°C is recorded. To further enhance the heat transfer rate, expanded graphite (EG) was added to the PCM and thermal analysis is carried out. After adding EG, it is found the temperature of the battery pack further reduces to 27.7°C for 2 mm thickness PCM. Finally, an experimental investigation is conducted by running this BM 3C discharge rate conditions. The maximum BM temperature of about 30.7°C is recorded and it is aligned perfectly with computational results. Across all thicknesses under 3C through structural simulations, displacement remained essentially unchanged, reflecting dominance of thermal expansion effects. The inclusion of EG reinforcement enhanced both thermal conductivity and structural rigidity, while increasing the case thickness effectively reduced stress levels. The 2 mm CPCM configuration is recommended for lightweight and thermally efficient EV applications, while the 4 mm CPCM configuration is preferable where enhanced structural stability is prioritized over weight reduction.