Optimization and Key Factor Analysis of Immersion Cooling Performance for 18650 Lithium-Ion Batteries in a Serpentine Channel Based on Response Surface Methodology

Efficient thermal management of lithium-ion batteries is crucial for electric vehicle safety and performance. This study investigates immersion cooling in serpentine channels for 18650 batteries, aiming to identify key factors affecting maximum battery temperature (Tmax) and pump power (Pw). A Box-Behnken experimental design is implemented with Computational Fluid Dynamics simulations to analyze responses Tmax and Pw. Five design variables are defined: partition length (Lp), battery charging/discharging rate (Crate), coolant volumetric flow rate (V), coolant inlet temperature (Tin) and ambient temperature (Tamb). Statistical significance is evaluated via Analysis of Variance. The results show that: Tin dominated Tmax, followed by Crate, V, and Lp. Significant interactions (V·Tin and V·Tamb) are observed. For Pw, V and V² show extreme significance, while Lp effects were minor. Interaction Lp·V was significant but secondary. After optimization to minimize Tmax, Tave and Pw, the optimal design values for Lp, Crate, V, Tin, and Tamb were determined to be 89.5 mm, 1.08 C, 0.51 LPM, 20 °C, and 25.62°C respectively. The corresponding optimized values are: Tmax = 22.87°C, Tave = 21.67°C, and Pw = 0.279 mW. Optimal thermal management requires prioritizing Tin control for temperature suppression and V regulation with non-linear compensation for energy efficiency.