Optimized nanofluid coolants enhance thermal performance in ruffled fin automotive radiators

Nanofluids offer superior heat transfer compared to conventional automotive coolants, with further improvements achievable through particle hybridization and particle shape effects. This study numerically investigates the thermal performance of a ruffled-fin radiator using ternary hybrid nanofluids composed of ZnO, Al₂O₃, TiO₂, MWCNTs, graphene, Fe, Cu, and Ag nanoparticles at varying volume fractions. Combinations such as Fe/Cu/Ag, Fe/Cu/ZnO, and Ag/Al₂O₃/TiO₂ enhanced convective heat transfer, as reflected in increased Nusselt numbers and overall heat transfer coefficients. Increasing the volume fraction reduced outlet coolant temperature, with an optimal nanofluid achieving a 44.6% temperature drop at the engine outlet. The performance index, defined as a composite measure of heat transfer and cooling efficiency, decreased by 5.8-11.7% across the eight ternary nanofluids, with non-metallic oxides exhibiting the smallest reduction. These results demonstrate the role of ternary hybrid nanofluids in improving radiator cooling while indicating efficiency trade-offs at higher volume fractions.