Natural convection and surface radiation in an insulated square cavity with inner hot and cold square bodies

Abstract

A numerical investigation of laminar natural convective heat transfer and surface radiation around two square isothermal cylinders maintained at a temperature difference was carried out. These cylinders are placed inside a square cavity whose walls are perfectly adiabatic. The governing equations were iteratively solved using the control volume and the discreet ordinate approaches. The Rayleigh number (103≤Ra≤107), the walls emissivity (0≤ε≤1), the sides-ratio (1≤ζ≤5), the active area (0.02≤S≤0.2), the horizontal (0.25≤Dh≤0.75) and the vertical (0.2≤DV≤0.8) positions are the governing parameters. The effect of the mentioned governing parameters on the streamlines, isotherms and the convective and radiative Nusselt number are presented. The present results show that surface radiation considerably affects the flow structure in the annulus especially at high Rayleigh numbers. The effect of the locations of the inner square cylinders, the sides-ratio and their sizes are found to play a significant role in radiative and convective heat transfers.