Experimental thermal and hydrolic behavior of <scp>CuO</scp> /water and <scp>Cr</scp> /water nanofluids in a production passenger‐car radiator

Abstract Improving the efficiency of automotive cooling systems is crucial for enhancing fuel economy and engine performance. This study experimentally investigated the performance of CuO/water and Cr/water nanofluids in a radiator at three Reynolds numbers (Re) and nanoparticle concentrations of 0.5%, 0.75%, and 1.0%. The highest improvements were observed with 1.0% Cr/water, achieving a 20.95% increase in the Nusselt number (Nu), an 18.99% increase in the heat transfer coefficient, and an 18.36% increase in the heat transfer rate. The highest heat transfer rate ( Q ) of 67.81 W was obtained with 1.0% CuO/water. Maximum heat transfer coefficients reached 17.95 W/m 2 K for CuO/water and 18.65 W/m 2 K for Cr/water, with corresponding maximum Nu values of 7.39 and 8.22, respectively. The Re−( h nf / h bf ) ratios were 1.14 for CuO/water and 1.18 for Cr/water, while the Re−( Q nf / Q bf ) ratios reached 1.18 and 1.15, respectively. These results indicate that 1.0% Cr/water nanofluid is particularly effective in improving radiator performance without structural modifications, with enhancements more pronounced at lower Reynolds numbers. Overall, nanofluid (n f ) technology shows significant potential for enhancing automotive cooling efficiency, although long‐term system evaluations are recommended before industrial application. In conclusion, the results of this study demonstrate that n f technology can be applied to automotive cooling systems as an effective method to improve thermal performance without requiring any structural modifications. However, before industrial implementation, detailed evaluations of system dynamics and long‐term performance are essential to ensure operational safety and reliability.