Hybrid nanofluids were prepared using nanocomposites (G/A1209) with various graphene concentrations (550 wt%) to investigate the dispersion stability and the optimum concentration of graphene in nanocomposite (50/50 wt/o). The thermophysical properties were studied as a function of particle loading (0-0.3 vol%) at the temperature range (20-70 "C). Results show that the thermal conductivity enhances to a maximum of 45% ( 3%) compared to base fluid -DI water. The heat transfer performance was investigated by varying the Reynolds number (150-650) at nanofluid concentrations (0-02 vol%). The heat transfer coefficient and Nusselt number for 02 vol% were found to be higher than Dl water by 51.73% ( 2%) and 16% (-1.5%) respectively with a maximum rise in pressure drop of 5% ( 0.5%). The enhancement in the thermal transport properties with a low penalty in pumping power requirement indicates the potential ability of (C A1505) hybrid nanofluid in the cooling of heat-generating electronic systems. C 2020 Elsevier B.V. All rights reserved.