Steady and transient sensitivity investigations on a passive battery thermal management system coupling with phase change materials and heat pipes: Full numerical modeling and orthogonal tests

For safety reasons, the temperature distribution of the battery pack should be kept within a reasonable range. Therefore, in the present research, a passive battery thermal management system (BTMS) coupling with phase change material (PCM) and heat pipes (HP) was proposed. Full CFD (Computational Fluid Dynamics) models validated well by the experimental results were adopted for this research. Firstly, the sensitivity of parameters such as PCM type, PCM thickness and ambient temperature on the thermal performance of BTMS was obtained by orthogonal tests. Numerical results show that the greatest influence on the maximum temperature is the ambient temperature. In the variance analysis showed that the PCM thickness has a significant effect on decay the battery temperature difference. Furthermore, operational range and variance analysis confirmed the optimal BTMS, i.e., with PCM3 thickness of 3 mm and ambient temperature of 30 °C. Subsequently, transient modeling and analysis of the battery discharge process were carried out. Unsteady results showed that the maximum temperature of the battery was reduced from 68.90 °C to 43.19 °C, and simultaneously, the maximum temperature difference dropped from 16.58 °C to 3.66 °C. In the process of battery discharge, PCM was properly adjusted regarding of its thickness; whereas, its melting temperature should be kept approaching to the ambient temperature, which was beneficial to the operational safety of the battery. In addition, temperature distribution of the battery has a linear relationship to the ambient temperature; when every 5 °C increase was observed in ambient temperature, the maximum temperature of the battery was boosted by 2.3 °C and the temperature difference was reduced by 1.2 °C, separately. Present research, straightforwardly maintaining the temperature distribution of the power battery in a safe and efficient range, could be significant for improving energy utilization and reducing extra energy consumption of the power battery, simultaneously.