Unidirectional flow and heat transfer optimization of pin-fin cold plates for power battery thermal management: Integrated experimental, simulation and multi-objective optimization study

• The large‑dimension cold plates with over 20 battery cells are investigated. • Multi-objective optimization for cold plate design is demonstrated. • The optimal design realizes a high Nusselt number of 40.7 with relatively high heat‑handling capacity of 0.18 W/Pa. To address the thermal management challenges of high-power battery packs, a novel hybrid cold plate integrating straight channels and pin fins is proposed in this study. The structural and operational parameters of the cold plate are systematically optimized through a combined approach incorporating multi-objective optimization, numerical simulations, and experimental validation. Results indicate that the circular pin-fin (C-Pin-fin) configuration achieves the optimal thermo-hydraulic performance. At a mass flow rate of 0.03 kg/s, compared with conventional straight-channel designs, the maximum temperature is reduced by 2.9 K and the temperature difference is decreased by 0.7 K. Sensitivity analysis shows that channel height is the dominant factor affecting pressure drop (with a sensitivity of 44.2%), while mass flow rate primarily influences temperature uniformity (with a sensitivity of 53 %). Compared to the baseline model, the optimized design improves temperature uniformity by 23.1 %, reduces pressure drop by 43.2 %, achieves a maximum reduction in thermal resistance of 16 %, and attains a maximum cooling efficiency factor of 15,452. Furthermore, a channel height of 1.5 mm is identified as optimal for balancing performance and structural compactness. The superior performance of the proposed design is experimentally validated, demonstrating its potential for application in advanced battery thermal management systems.