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

battery thermal management;direct cooling system;numerical simulation;phase transition;flow channel