Design of air cooled lithium battery thermal management system with Z-step type flow pattern based on electrochemical-thermal coupled model

Air-cooled battery management system (BTMS) is widely used in electric vehicle to regulate temperature of the battery packs, in which the flow pattern dramatically impacts the system cooling performance. In this study, a novel Z-step air-cooled BTMS is proposed to regulate airflow distribution pattern and enhance thermal management efficiency. The heat generation of individual cells was characterized using an electrochemical-thermal coupled model, and a validated computational fluid dynamics (CFD) approach was applied to numerically investigate the effects of the number of steps, battery spacing, and inlet air velocity on system performance. The results indicate that the Z-step configuration provides superior cooling performance, reducing the maximum temperature (Tmax), average temperature (Tavg) and maximum temperature differences (ΔTmax) by 2 K, 1 K and 1.6 K, respectively, compared with the conventional Z-type BTMS. Further analysis shows that the optimal cooling performance occurs with step-8 configuration, where the Tmax, ΔTmax and Tavg are reduced by 1.61–6.08 K, 1.61–6.26 K and 0.79–1.37 K, respectively. The most efficient cooling is achieved with a battery spacing of 6 mm, resulting in reductions of 2.66–10.73 K in Tmax, 0.23–5.84 K in Tavg and 13.54–22.61 K in ΔTmax compared with other spacings. Within the inlet air velocity range of 1.5–7 m/s, the pressure increase remains moderate between 1.5 and 4 m/s, with an optimal airflow velocity of 4 m/s identified. Additionally, as the discharge rates rise, both the maximum and average temperature differences increase significantly, particularly at higher rates. This study provides a valuable guidance for optimizing air-cooled BTMS design.