Rib shape and nanoparticle diameter effects on natural convection heat transfer at low turbulence two-phase flow of AL2O3-water nanofluid inside a square cavity: Based on Buongiorno’s two-phase model

Abstract

In this study, the effects of the rib shape with constant height, width and pitch and nanoparticle diameter on natural convection heat transfer of low turbulence flow of AL2O3-water nanofluid inside a square cavity is numerically simulated based on Buongiorno’s model. Two rib-ed vertical walls are with different constant temperatures (Th>Tc), while the top and bottom walls are insulated. Heat transfer of nanofluid in rib-ed square cavity is investigated at Rayleigh numbers107, 108 and 109 for various Prandtl numbers 7.0659, 7.3593 and 7.8353. The CFD simulation of AL2O3-water nanofluid is studied for 1–3% volume fractions ranges. Also, the effect of the various diameters of nanoparticle 50, 100 and 150 nm on natural convection heat transfer performance is analyzed. The comparison of present numerical and experimental results shows that due to the thermophoresis and the Brownian motion effects, obtained numerical results are acceptable. Results indicate that at high Rayleigh number, low volume fraction has better performance and trapezoidal rib is the best. Also, by reducing nanoparticle diameter, nanofluid heat transfer and NBT increase considerably. However, by increasing nanoparticle diameter, convection heat transfer decreases greatly and even gets less than base fluid and smooth walls.