Rayleigh-benard convection of cu-water and cuo-water nanofluids in rectangular enclosure

Abstract

The heat transfer by natural convection of nanofluid inside a horizontal cavity heated from below (Rayleigh–Bénard problem) was numerically investigated. Two different nanofluids are con-sidered: Cu-Water and CuO-Water nanofluids, for which viscos-ity and thermal conductivity were determined using Brownian motion models. We supposed that nanofluid is mono-constituent fluid. In this work, simulations have been carried out for different cavity aspect ratios (width/height) and Rayleigh number and na-noparticle volume fraction are taken up to 0.04 to ensure a New-tonian behavior of the mixture. It is found that the presence of nanoparticles affects the flow and thermal boundary layer and that is due to the high viscosity and thermal conductivity in the nanofluids. The nanofluid Nusselt number exhibits a slight increase as function of aspect ratio comparing to that in pure fluid. That enhancement is strongly influenced by Rayleigh number and the cavity aspect ratio.