Oscillatory natural convection of Al2O3-water nanofluid near its density maximum in a narrow horizontal annulus

Abstract

In order to reveal the oscillatory characteristics of the natural convection of nanofluid, this paper presents a comprehensive numerical work on the oscillatory natural convection of Al2O3-water nanofluid near its density maximum in a narrow horizontal annulus. The influences of nanoparticle volume fraction, Rayleigh number and density inversion parameter on the flow pattern evolution and heat transfer ability are analyzed. Results show that the density inversion of the working fluid affects the velocity and temperature distributions of the natural convection of Al2O3-water nanofluid significantly. Adding nanoparticles is beneficial to stabilizing the flow of nanofluid and keeping the symmetry of the flow structure. The convective heat transfer is enhanced with the increase of the volume fraction of nanoparticles. Furthermore, the evolution of the flow regime with the Rayleigh number at different volume fractions of nanoparticles is summarized.