Convective heat transfer in the flow of viscous Ag-water and Cu-water nanofluids over a stretching surface

An analysis is carried out to study the convective heat transfer in a nanofluid flow over a stretching surface. In particular, we focus on Ag-water and Cu-water nanofluids, and investigate the effects of the nanoparticle volume fraction on the flow and heat transfer characteristics under the influence of thermal buoyancy and temperature dependent internal heat generation or absorption. The numerical results indicate that an increase in the nanoparticle volume fraction will decrease the velocity boundary layer thickness while increasing the thermal boundary layer thickness, even in the presence of free convection currents and internal heat generation. Meanwhile, the presence of nanoparticles results in an increase in the magnitude of the skin friction along the surface and a decrease in the magnitude of the local Nusselt number. Such effects are found to be more pronounced in the Ag-water solution than in the Cu-water solution; indeed, the Ag-water solution decreases the boundary layer thickness more than that of the Cu-water solution. (C) 2011 Elsevier Masson SAS. All rights reserved.