Combined Effect of Turbulent Natural Convection and Radiation from a Horizontal Cylinder

Abstract

The present study deals with a computational investigation on the effect of surface radiation for a buoyancy-induced flow and heat transfer from a horizontal cylinder suspended in air. The numerical simulations have been performed in the turbulent regime by changing the Rayleigh number from to , surface emissivity of the cylinder surface within the ranges of 0.2–1, and considering temperature dependent fluid properties. The closure issues in the Reynolds-averaged Navier–Stokes equation have been taken care of by the standard model in conjunction with the standard wall function to resolve the near-wall turbulence. The discrete ordinate method has been implemented for solving the radiation equations. The effects of the and surface emissivity on the heat transfer have been depicted graphically to provide a more detailed insight into the physical phenomena through the normalized temperature contours and the velocity vectors. The relative strength of the radiation has been calculated and compared with the strength of the convection under different operating conditions. The relative magnitude of the radiation diminishes with an increase in the at a particular surface emissivity for the range of parameters considered in this study. In addition to that, an empirical correlation for the average Nusselt number has been proposed that will be helpful for industrial and academic purposes.