Effects of Nanoparticles Shape and Concentration on Natural Convection of Al2O3-Water Nanofluid in a Cubic Enclosure

Abstract

Three-dimensional numerical simulations of natural convection heat transfer of Al₂O₃-water nanofluid in a differentially-heated, cubic enclosure is performed considering nanoparticles shape. The effects of nanoparticles shape, nanoparticles volume fraction and Rayleigh number on natural convection heat transfer of Al₂O₃-water nanofluid are analysed. The results show that the thermal conductivity of nanofluid increases with the addition of Al₂O₃ rod-shaped nanoparticles, and the increasing degree of viscosity of nanofluid is higher than that of thermal conductivity. When Al₂O₃ spherical nanoparticles are dispersed in water, the strength of flow and heat transfer increases with increasing nanoparticles volume fraction. The average Nusselt number increases with the increase of nanoparticles volume fraction at Ra=10³ for Al₂O₃-water nanofluid with different nanoparticles shape. When Ra≥10⁴, the average Nusselt number decreases with the increasing volume fraction of Al₂O₃ rod-shaped nanoparticles, and the average Nusselt number increases with the increase of spherical nanoparticles volume fraction. The heat transfer rate increases with increasing Rayleigh number for nanofluid with different nanoparticles shape.