Numerical Study of Natural Convection in Vertical Enclosures Utilizing Nanofluid

Abstract

Enhancement of buoyancy-driven convection heat transfer within vertical cavities containing nanofluids subjected to different side wall temperatures and various aspect ratios is investigated. The computations are based on an iterative, finitevolume numerical procedure (SIMPLE) that incorporates the Boussinesq approximation to simulate the buoyancy term. With the base fluid being water, three different nanoparticles (Cu, TiO 2 , and Al 2 O 3 ) are considered as the nanofluids. This study has been carried out for the pertinent parameters in the following ranges: the Rayleigh number, Ra f = 10 5 –10 7 and the volumetric fraction of nanoparticle between 0 and 5 percent. The results are presented for different length-to-height ratios varying from 0.1 to 1.0. The comparisons show that the mean Nusselt numbers and velocity magnitudes increase with volume fraction for the whole range of the Rayleigh numbers. The predictions show a noticeable heat transfer enhancement compared to pure fluid. It is also found that the heat transfer enhancement utilizing nanofluid is more pronounced at low aspect ratios than high aspect ratios. Moreover, the results depict that the addition of nanoparticles to the pure fluid has more effects at lower Rayleigh numbers.