Impacts of nanofluid flow on skin friction factor and Nusselt number in curved tubes with constant mass flow

Three-dimensional elliptic governing equations were solved to investigate laminar mixed convection of a nanofluid consists of water and Al2O3, buoyancy-affected and heat transfer of a curved tube. Simultaneous effects of the buoyancy force, centrifugal force and nanoparticles concentration on the fluid flow developing and heat transfer along the pipe is investigated in this paper. The nanoparticles concentration does not have any significant effect on the secondary flow, while the axial velocity, Nusselt number, skin friction factor as well as fluid temperature have been affected considerably. In this paper, some important new results are obtained. Firstly, for a given flow rate; nanoparticles concentration have positive effects on the axial velocity and skin friction factor. Secondly, buoyancy force has negative effect on the Nusselt number and skin friction factor. (C) 2007 Elsevier Inc. All rights reserved.