An Inspection of Viscosity Models for Numerical Simulation of Natural Convection of Al2O3-Water Nanofluid with Variable Properties

Abstract

Background: An innovative technique to improve the heat transfer involves dispersing the nanoscale particles in a base fluid, known as nanofluid. In earlier studies, to determine the nanofluid properties, especially the effective viscosity and thermal conductivity, basic models, namely the Brinkman model and Maxwell model have been employed. Yet these models do not take into account the dependency of the viscosity and thermal conductivity on the parameters, say, the mean diameter of the nanoparticles and the temperature. Considering this, recently, some researchers have studied nanofluid with variable properties and proposed new correlations, based on the experimental and theoretical data available in the literature, for calculating the nanofluid properties. The present paper aims to study the effects of uncertainties of different viscosity models of Al2O3–water nanofluid, namely the Brinkman, Abu-Nada, Khanafer and Vafai, and Corcione models on natural convection flow and heat transfer within a differentially heated square enclosure. Employing these models, effects of volume fraction and the mean diameter of nanoparticles, as well as the Rayleigh number, on the characteristics of flow and heat transfer are examined. Keywords: Natural convection, nanofluid, variable properties, viscosity models, numerical study, Nusselt number.