Geometric optimization of inter-cell spacing for enhanced phase-change cooling in a dual-evaporator loop heat pipe battery thermal management system

This research aimed to investigate the role of geometric factor, inter-cell spacing, in determining the efficiency of phase-change-based cooling in a battery thermal management system (BTMS) with a dual-evaporator Loop Heat Pipe (LHP). Compared to traditional research that primarily considers working fluid selection or system design, this study investigates inter-cell spacing as a design parameter in phase-change-based cooling. The objective was to determine the geometric design that optimizes phase-change heat transfer in high-temperature conditions. Five inter-cell spacing configurations (13, 15, 18, 20, and 25 mm) were tested, and the thermal behavior of the battery module and evaporator surfaces was measured with multiple temperature sensors. The results showed that LHP system was more effective at heat removal than the passive system and had the potential to lower peak temperature as well as thermal runaway. The best inter-cell spacing of 18 mm was determined based on thermal performance, achieving the most balanced thermal performance of 40.94% and 32.30% in Evaporators 1 and 2, respectively. This optimum was characterized by a balance between conductive heat transfer of battery cells and efficient phase-change heat transfer in LHP system. Reduced spacing constrained airflow and limited the contribution of convective heat transfer. Meanwhile, excessive spacing increased thermal resistance and weakened thermal coupling, reducing overall cooling effectiveness. The results confirmed the spacing between cells as a key design factor in regulating the cooling effectiveness of phase-change cooling in LHP-based battery thermal management systems (BTMS), offering insights for designing compact and energy-efficient BTMS for high-power applications in electric vehicles.