Turbulent topology optimization of liquid cooling plates for lithium-ion battery energy storage systems considering constant and temperature-dependent coolant properties

The thermal runaway risk and poor temperature adaptability of lithium-ion batteries under wide-temperature conditions limit the application of battery energy storage systems in extreme environments. Although existing studies on topology optimization of liquid cooling plates have considered both constant-property and variable-property assumptions for the coolant, a systematic quantitative comparison between the two in terms of cold plate design and performance has not yet been conducted. In this paper, a turbulent topology optimization model considering temperature-dependent properties is established with 50% ethylene glycol/water mixture as the coolant. The channel structures obtained from two-dimensional topology optimization are mapped into a three-dimensional module model, enabling the evaluation of cooling plate performance under realistic battery heat generation conditions. Combined with Pareto multi-objective optimization, entropy generation analysis and field synergy theory, the way variable-property effects regulate optimization evolution and thermo-flow coupling is systematically elucidated. The results reveal that under low pumping power constraints, the variable-property scheme improves heat transfer by 21.9% with nearly identical flow resistance, benefiting from a thermally induced self-acceleration effect caused by temperature-dependent viscosity reduction. Within the environment temperature range of 278.15–318.15 K, the optimized variable-property configuration maintains more uniform temperature distribution and eliminates the abnormal peak temperature difference of 10.52 K in constant-property structures. Meanwhile, the pressure drop is reduced by up to 6% at low temperatures, significantly enhancing the robustness of wide-temperature operation. An entropy-weighted TOPSIS evaluation confirms that the variable-property design delivers better overall thermo-hydraulic performance at 283.15–308.15 K, satisfying the operational demands of energy storage batteries in temperate regions.