Application of nanofluids for heat transfer enhancement of separated flows encountered in a backward facing step

Numerical investigation of heat transfer over a backward facing step (BFS), using nanofluids is presented. Different volume fractions of nanoparticles are presented in the base fluid besides different type of nanoparticles have been used. The finite volume technique is used to solve the momentum and energy equations. The distribution of Nusselt number at the top and the bottom walls of the BFS are obtained. For the case of Cu nanoparticles, there was an enhancement in Nusselt number at the top and bottom walls except in the primary and secondary recirculation zones where insignificant enhancement is registered. It was found that outside the recirculation zones, nanoparticles having high thermal conductivity (such as Ag or Cu) have more enhancements on the Nusselt number. However, within recirculation zones, nanoparticles having low thermal conductivity (such as TiO2) have better enhancement on heat transfer. An increase in average Nusselt number with the volume fraction of nanoparticles for the whole range of Reynolds number is registered. (C) 2007 Elsevier Inc. All rights reserved.