Dynamic-static composite immersion cooling for improving thermal equalization behavior in lithium-ion battery packs

Ensuring stable thermal equalization behavior is critical for extending the operational lifespan of lithium-ion batteries (LIBs). To address this challenge, a multimodal dynamic-static composite immersion thermal management system based on micro-heat pipe arrays (MHPAs) is proposed, which utilizes natural convection in the static region to enhance the thermal equalization behavior, while forced convection in the dynamic region is utilized to improve the cooling efficiency. Four cooling strategies—forced air cooling (FAC), static immersion cooling (SIC), dynamic immersion cooling (DIC), and composite immersion cooling (CIC)—were systematically evaluated through numerical simulations using fluctuation effect analysis. The results demonstrated that CIC outperformed the other strategies by combining the superior heat dissipation capabilities of DIC with the stable thermal equalization performance of SIC. Furthermore, an in-depth analysis of the factors influencing CIC revealed that the integration of fins significantly enhanced the cooling performance and thermal equalization behavior of the module. Specifically, the inclusion of fins led to a 57.76 % reduction in the maximum temperature and a 75 % decrease in the temperature difference within the module, compared to scenarios without fins. The study also investigated the effects of coolant flow rate and battery spacing on the battery thermal management system (BTMS), balancing the trade-offs between thermal performance, energy consumption, and grouping efficiency. Additionally, the design of fluid combinations with varying physical properties was analyzed, aiming to improve cooling performance by leveraging the unique capabilities of each fluid. The research results provide theoretical insights for the design of advanced BTMS with enhanced thermal equalization characteristics.