Thermal analysis of electric vehicle battery cooled using nanofluid

This doctoral thesis investigates the efficiency of a liquid-cooled electric vehicle battery module through theoretical and numerical analyses. The theoretical section involves the development of comprehensive correlations to calculate heat generation in a cylindrical 18650 battery based on state of charge, discharge rate, and temperature. These correlations have been tested on lithium-ion batteries with commonly preferred cathode materials such as LCO, NMC, NCA, showing good agreement with experimental results from literature except for batteries with LFP cathode material. In the first part of the numerical analyses, the cooling system is optimized by examining the effects of the number of cooling channels and the contact width of aluminum blocks. The critical impact of precise adjustments on the contact width of aluminum blocks is emphasized as a significant inference, highlighting the need for optimization in the thermal performance of the battery module. In the second part of the numerical investigations, the study explores the impact of different cooling fluids (water, EGW, EGW-nanoparticles) under different discharge rates (1C and 2C) using the best cooling configuration. Nanofluid studies are enriched with three nanoparticle kinds (Al2O3, CuO, and TiO2), two different sizes (30 nm and 75 nm), and four different mixing ratios (1%, 2%, 3%, and 4%). The studies conclude that nanofluids are thermally more advantageous but disadvantageous in view of pressure drop. Particularly, the nanofluid containing 30 nm CuO nanoparticles at a 4% mixing ratio exhibit temperature control similar to traditional water-based cooling system for battery modules but considering the increased pressure drop is essential. The findings suggest a positive correlation between using nanoparticles in smaller-sized or in higher fractions and overall thermal efficiency. Despite improvements, nanofluids cannot exceed an 11% improvement compared to traditional ethylene glycol-water.