Numerical evaluation of different cooling strategies for cylindrical battery packs: from air natural convection to topology-optimized cold plates

When lithium-ion batteries operate under demanding conditions, excessive heat generation can lead to degradation or failure. An efficient battery thermal management system (BTMS) is therefore crucial for safety and optimal performance. To keep temperatures within safe limits and reduce weight, this study investigates the design of advanced BTMS for an 18650 cylindrical lithium nickel manganese cobalt oxide (Li-NMC) battery pack subjected to charge/discharge rates up to 5C. Both air and liquid cooling methods are evaluated in different configurations – natural and forced air convection, and direct and indirect liquid cooling. The integration of phase change materials (PCMs) to enhance efficiency, and topology optimization (TO) techniques to reduce the cold plate weight are also explored. Computational fluid dynamic (CFD) approaches are employed to simulate coupled heat transfer, fluid flow, and phase change phenomena starting from Bernardi's battery electro-thermal model with temperature-and state of charge (SoC)-dependent parameters. Results show that the benchmark case with air natural convection leads to temperatures above 100 °C, while forced air at 1 m/s maintains temperatures below 60 °C, though with a severe non-uniformity. Cross-flow liquid cooling keeps cell temperatures below 30 °C and improves uniformity (maximum temperature difference around 4.80 °C) with reduced pressure drop. PCM systems stabilize temperature during melting but lose effectiveness afterward, while adding aluminum fins enhances uniformity. Finally, the cross-flow cold plate TO-based design reduces system mass by 79.5% (from 127 g to 26 g) with a minimal temperature penalty of 6 °C compared to the standard configuration, that does not compromise the battery pack operation. • Various BTMS architectures are numerically evaluated under high thermal loads. • Battery thermal models capture heat generation and cell-level temperature dynamics. • Cross-flow liquid cooling ensures temperature uniformity and T max < 30 °C up to 5C. • Aluminum fins improve PCM temperature uniformity. • Topology optimization cuts system mass by 79.5% with minor temperature penalties.