Design optimization of Air-Cooled Li-ion battery thermal management system with Step-like divergence plenum for electric vehicles

Abstract

Air-cooled Battery Thermal Management System (BTMS) technology has been proven and is frequently employed to regulate the distribution of temperature in a battery pack of an electric vehicle. In this study, a step-like divergence plenum was introduced to a standard Z-type BTMS to alter its airflow distribution pattern and thus improve its cooling effectiveness. The impacts of the number and length of steps in the divergence plenum on the cooling responses of the BTMS were investigated using a validated Computational Fluid Dynamics (CFD) method. Analysis of 1-step, 3-step, 4-step, and 7-step BTMS models were conducted and findings showed that the step quantity has a significant impact on the battery pack's ability to dissipate heat. For a step length of 30 mm, a 7-step case model offered the best system’s maximum temperature of 324.9 K and cell temperature difference of 1 K which were both 3.94 K and 5.93 K, respectively lower than that of the standard Z-type model. Furthermore, the step case models were optimized by observing the impacts of their step length on system's thermal performance. The outcomes showed that there was a substantial impact of the step length on cooling performance for all case models. For instance, a 4-step case model with a 45 mm step length offered a reduction in maximum temperature of 3.61 K and maximum temperature difference of 6.01 K when compared to the standard Z-type model. Finally, the behaviour of each case model was examined under increasing inlet air velocity and it shows that at higher airflow velocity, the 7-step case model performed substantially well than other investigated cases.