An efficient immersion cooling of lithium-ion battery for electric vehicles

An Electric Vehicles (EVs) have several advantages over the conventional Internal Combustion Engine (ICE) vehicles, such as improved energy efficiency, good performance, zero-emission of combustion pollutants and being environmentally friendly. The EVs performance is mainly dependent on the efficient thermal management system of battery pack. The major issues that arise in the lithium-ion battery (LIB) for EVs are longer charging time, anxiety of range, battery overheating due to high discharge rate at peak conditions, expensive battery packs, thermal runaway or even explosive due to overheating or short-circuit, limited battery cycle life, reliability and safety. LIB is widely used in EVs due to its high energy density, high voltage platform, low discharge rate and longer battery cycle life at optimum temperature of 20 °C to 40 °C. The imbalance in the battery pack occurs due to the individual cells within the battery pack having different states of charge or SOC and state of health or SOH. Factors that contribute to battery imbalance are variations of cells from different manufacturers with differences in capacity, internal resistance and voltage characteristics; battery age and usage may experience different levels of degradation; inadequate cell balancing; overcharge/discharge; and faulty battery thermal management system. Detailed study of the BTMS with single and multiphase flow with phase change heat transfer is experimentally expensive and numerically challenging due to the requirements of the smaller spatial and temporal scales. Accurate capturing of experimental flow physics and heat transfer required a high-precision measurement techniques and numerical simulation requires a super-computing facility. In the present numerical study, a detailed investigation of direct liquid cooling or immersion cooling using splitter hole arrangements are considered. The characteristics of Li-Ion Battery pack cooling system is evaluated based on conjugate heat transfer solver of chtMultiRegionFoam in open source OpenFOAM®. Effect of two different splitter hole diameters of 2 mm and 3 mm are considered. Based on the numerical study, it is found that 2 mm hole size having better performance than 3mm hole due to higher velocity magnitude at uniform flow rate of the working fluid. Based on the effect of the splitter holes number reduction in the battery packs shows good agreement with smaller deviation. Overall performance of the battery pack is found in Case-3 with reduction of holes in row-wise direction is slightly effective than Case-1 and Case-4 proposed in the simulations.