▎ 摘　　要

Metals and metallic oxide nanoparticles have been studied extensively for heat transfer applications as compared to functionalized graphene and hybrid nanoparticles. Volume concentrations of nanoparticles studied have been greater than 0.01%. In the present work, an attempt is made to study the effect by adding carboxyl graphene (CG), graphene oxide (GO) and novel hybrid nanoparticles to a conventional hot fluid - 50:50 ethylene-glycol and water - at ultra-low volume concentrations, on the performance of compact heat exchanger (liquid-air, automotive radiator). Effect of Reynolds number of hot fluid, Reynolds number of air, the volume concentration of nanoparticles on the performance parameters such as Nusselt number, effectiveness, pressure drop and friction factor are studied in detail. A maximum of 3.59 and 4.92 times increase in Nusselt number is observed at 0.02 vol % of CG and 0.04 vol% of GO respectively. The same is found to be 11 times at 0.005 vol % of GO and 0.0075 vol % of CG hybrid nanofluid. The results indicate a significant increase in the performance of the compact heat exchanger, both in terms of effectiveness and pressure drop. Study indicates a maximum of 232% improvement in effectiveness with a 66% reduction in pressure drop at a volume concentration of 0.005 vol % of GO and 0.005 vol % of CG. Functionalized graphene and hybrid nanoparticles offer great scope for enhancing compact-heatexchanger-performance and/or reduction in the size.