Thermal energy management in the automobile industry has been a growing challenge to ensure effective engine cooling and increase performance. The objective of this study is to investigate the heat transfer characteristics of nanofluids with different concentrations. The study focuses on the effect of thermophysical properties such as density, viscosity, and thermal conductivity on the thermal performance of the flat tube. Al₂O₃ and CuO nanoparticles concentrations of 0.05 to 0.3 per cent by volume were added into the mixture of the base fluid. CATIA V5 was used to design the flat tube, and the model was further simulated using ANSYS Fluent, a computational fluid dynamics (CFD) software. The base fluid consisting of 20% ethylene glycol and 80% water was observed to have a thermal conductivity of 0.415 W/m.K. The thermal conductivity, however, increases with the addition of 0.3% volume concentration of Al₂O₃ and CuO nanofluid, which are 0.9285 W/m.K and 0.9042 W/m.K, respectively. Under the same operating condition, the Nusselt number was observed to increase from 94.514 for the base fluid to 101.36 and 130.46 for both Al₂O₃ and CuO nanofluid, respectively. It can thus be concluded that CuO with a 0.3% concentration has the highest heat transfer rate compared to others. The heat transfer coefficient was recorded at 22052.200 W/m² K, and the thermal conductivity obtained was 0.9042 W/mK, Nusselt number was 130.459, and the rate of heat transfer was at 66.71 W. There was a 10% increase in heat transfer coefficient at 0.3% nanofluid concentration when compared to 0.05%.

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