Investigating the influence of nano particle's radius on thermophysical properties of al2o3-water nanofluids under brownian motion effect

Abstract

In the past two decades, numerous studies and experiments have been conducted by several researchers around the world in the field of nanofluids. In most of these studies, CuO-water base, SiC-water base, and Al2O3-water base nanofluids have been utilized. As industry has shown a promising and increasing application of Al2O3-water nanofluids, a comparative numerical investigative study on the effect of nanoparticle’s radius of Al2O3-water base nanofluid in a 2-D square shape enclosure is presented. This study has considered a Brownian motion effect in a single-phase flow regime. Saghir et al. [International Thermal Sciences, Vol. 100, 2016] have shown that single-phase approach predicts Nusselt number with a better accuracy when a range of Rayleigh numbers and particle concentrations is investigated. This study examined volumetric fraction of Al2O3 nanoparticles from 1vol% to 5vol% within a system in which input temperature variation is from ΔT=25°K to 75°K. It was revealed that thermal conductivity and dynamic viscosity are mostly influenced by the nanoparticle size (radius) among all the thermophysical properties of the nanofluid under this study. It was also shown that; as the radius of nanoparticles is increased the thermal conductivity and dynamic viscosity are decreased respectively. This reduction is more noticeable as the volumetric fraction of nanoparticles is increasing in the nanofluid.