Effects of Cu and Ag nano-particles on flow and heat transfer from permeable surfaces

Consideration is given to flow and heat transfer of nano-fluids over a permeable flat plate with convective boundary condition. The governing partial differential equations are transformed into ordinary differential equations using similarity solutions, before being solved numerically. Two types of nano-fluids, Cu-water and Ag-water are considered. The effects of nano-particles volume fraction, the type of nano-particles and permeability parameter on skin friction and convection heat transfer coefficient are studied and discussed. It is shown that the increment in skin friction is a considerable drawback imposed by Cu-water and Ag-water nano-fluids, especially in case of injection. In the cases of injection and impermeable surface, increasing the nano-particles volume fraction results in augmentation of convection heat transfer rate. However, in the case of suction, adding Cu and Ag particles reduces the convection heat transfer coefficient at the surface in spite of thermal conductivity enhancement imposed by the nanoparticles. (C) 2014 The Society of Powder Technology Japan. Published by Elsevier B. V. and The Society of Powder Technology Japan. All rights reserved.