As the demand for higher specific energy density in lithium-ion battery packs for electric vehicles rises, addressing thermal stability in abusive conditions becomes increasingly critical in the safety design of battery packs. This is particularly essential to alleviate range anxiety and ensure the overall safety of electric vehicles. A liquid cooling system is a common way in the thermal management of lithium-ion batteries. This article uses 3D computational fluid dynamics simulations to analyze the performance of a water-cooled system with rectangular channels for a cylindrical battery pack. A finite volume method is used, validating the results with experimental data. Firstly, the effects of converging and diverging of channels on the thermal and hydraulic characteristics of the considered cooling system are investigated. Then, the co- and counter-flow pattern strategies of the coolant are studied. The results indicate that converging the channels leads to the Nusselt number enhanced by about 21% compared to the conventional design of the system. However, better hydraulic performance is found for the case with diverging channels. The decrement in the friction loss of the cooling system with diverging channels is about 70%. It is also found that the flow pattern is considerably effective in controlling the temperature uniformity of the battery pack. The counter-flow pattern of the channels provides lower temperatures, and the maximum deviation from the co-flow pattern (~ 5.2 K) can be found for the case with diverging channels.

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