The Prandtl number, Reynolds number and Nusselt number are functions of thermophysical properties of nanofluids and these numbers strongly influence the convective heat transfer coefficient. The pressure loss and the required pumping power for a given amount of heat transfer depend on the Reynolds number of flow. The thermophysical properties vary with temperature and volumetric concentration of nanofluids. Therefore, a comprehensive analysis has been performed to evaluate the effects on the performance of nanofluids due to variations of density, specific heat, thermal conductivity and viscosity, which are functions of nanoparticle volume concentration and temperature. Two metallic oxides, aluminum oxide (Al2O3), copper oxide (CuO) and one nonmetallic oxide silicon dioxide (SiO2), dispersed in an ethylene glycol and water mixture (60:40 by weight) as the base fluid have been studied. (C) 2012 Elsevier Ltd. All rights reserved.