Effect of Surface Radiation on Free Convection in Vertical Cylinders Partially Annular

Abstract

The coupled of free convection with surface radiation in an annular region of two concentric vertical cylinders filled with air has been numerically investigated. The steady-state continuity, Navier–Stokes and energy equations were carried out by the finite volume method, and the Discrete Ordinates Method (DOM) was used to solve the radiative heat transfer equation (RTE). The computations have been performed for 103 ≤Ra≤ 106, with the emissivity coefficient of all the walls varying between 0 and 1. The influence of the both, Rayleigh numbers and emissivity coefficient of the wall for fixed height ratio X=0.5 on natural convection and radiation heat transfer in enclosure have been solved. The result shows that surface radiation significantly altered the temperature distribution and the flow patterns, especially at higher Rayleigh numbers. The average Nusselt number has also been discussed for different emissivity through the enclosure.