Influence of Refrigerant Phase Transition on the Temperature Control of Large Capacity Lithium-ion Battery

A numerical simulation model was used to investigate the impact of refrigerant phase change on the temperature control of lithium-ion batteries. A direct cooling system was designed, and an electro-thermal coupled model was established to simulate heat generation in batteries. The Lee model was used for the phase-change simulation. The model reliability was confirmed through experiments, with deviations under 3%. Simulations were conducted under various conditions to analyze the effects of different boundary conditions on the cooling performance of a harmonica-style cold plate and flow channel structures of parallel and serpentine cold plates. The results indicated that at a 2 C rate, the maximum temperature and temperature difference of a direct cooling system were 7.12% and 58.86% lower than those of a liquid cooling system. When the evaporation temperature increased from 10 ℃ to 20 ℃, the pressure difference of the direct cooling plate decreased from 45.74 Pa to 39.48 Pa. A lower evaporation temperature promoted the refrigerant phase transition. An increased liquid phase fraction at the inlet can lower the highest temperature of the battery module, but may lead to greater temperature differences and excess liquid refrigerant. Increasing the effective contact area of the flow channel with the battery bottom aids cooling, and extending the channel length promotes a complete refrigerant phase change.