Performance study on a novel hybrid thermal management system for cylindrical lithium-ion battery pack based on liquid cooling and PCM

• Hybrid BTMS can improves the temperature distribution of cylindrical batteries . • Optimized composite PCM balances cooling performance and energy density . • Driving cycle proves hybrid BTMS superior thermal stability under dynamic load. • Phase change temperature is the most sensitive parameter in system optimization. High energy density cylindrical lithium-ion battery packs face severe thermal challenges under high intensity discharge conditions, which significantly reduce the effectiveness of conventional cooling strategies. To address this limitation, a novel hybrid battery thermal management system (BTMS) consist of wave-shaped cold plates with tubular composite phase change materials (PCMs) is proposed in this study. A three-dimensional heat transfer model is developed for optimizing structural parameters and evaluating system performance. The numerical results show that cross-flow configuration can substantially improves temperature uniformity of battery pack compared to single-directional flow. Optimal operating conditions are determined as 0.05 m/s coolant inlet velocity and 2.5 mm composite PCM thickness, achieving balanced temperature distribution without compromising heat dissipation efficiency. The composite PCM incorporating 9 wt% expanded graphite and phase change temperature of 37 ℃ can enhance the thermal conductivity and utilization efficiency of PCM significantly. The hybrid BTMS reduces maximum battery temperature by 22.2 %, liquid fraction by 61.7 %, battery pack temperature difference by 16.8 %, and single-cell temperature difference by 28.5 % relative to baseline configuration. Real-world driving cycle validation shows that the hybrid BTMS reduces peak temperature by 20.89 % and effectively minimizes temperature fluctuations relative to conventional active cooling systems. Parametric sensitivity analysis quantifies relationships between critical design parameters and performance metrics, providing theoretical foundations for advanced lithium-ion battery thermal management optimization.