چكيده به لاتين
Lithium-ion battery (LIB) cells are responsible for powering most electric vehicles. Lithium-ion batteries are considered the best available on the market due to their high energy density, specific power, and long cycle life. However, these batteries face challenges such as thermal management because they are highly sensitive to temperature. Among the different cooling methods, direct liquid cooling, also known as immersion cooling, can provide a high cooling rate due to complete contact with the heat source. Single-phase liquid immersion cooling with dielectric fluids (DELC) ensures safety and effective cooling performance while reducing parasitic power consumption and space requirements.
In this study, the comparison of two dielectric fluids is conducted using both experimental and numerical methods on four 18650 lithium cobalt oxide (LCO) cells arranged in a 4-series-1-parallel configuration. To achieve this, computational fluid dynamics (CFD) tools and the NTGK electrochemical battery simulation model are utilized, along with the construction of an experimental battery immersion setup to validate the obtained results.
In this study, the use of deionized water and mineral oil improved the temperature difference between the inlet fluid and the average temperature of each cell. However, compared to mineral oil, deionized water showed better temperature improvement. For instance, in cell number 1, at a 1.5C discharge rate, temperature improvement at a fluid flow rate of 0.3 liters per minute was 42.34%, at 0.4 liters per minute it was 46.7%, and at 0.5 liters per minute it was 44.85%.
Furthermore, as the volumetric flow rate of both fluids increased, the temperature of the cells decreased at each stage, but the rate of temperature improvement decreased with increasing flow rate. Additionally, as the fluid flow rate increased, the temperature difference between the cells near the inlet of the battery chamber and the cells in the next row decreased.
Deionized water has advantages over mineral oil, such as being cheaper, more accessible, having better performance, and requiring less pumping effort. However, the main drawback of deionized water, as observed in the experiments, is the formation of sulfate on the battery cells and circulating fluid, which eventually leads to their long-term failure.
