Effect of surface radiation on RBC in cavities heated from below

Numerical investigations of combined free convection and surface radiation in enclosures for Rayleigh–Benard configuration of air are carried out using FLUENT 6.3, with a view to determine the onset of convection and to propose correlations for convection and radiation Nusselt numbers based on a detailed parametric study. The onset of Rayleigh–Benard convection is delayed with an increase in the emissivity of the sidewalls. The effect of surface radiation on the onset of convection however diminishes with aspect ratio (AR) and for AR = 8, the effect of surface radiation ceases. Post-onset, the effect of surface radiation on the convection heat transfer becomes insignificant beyond an aspect ratio of 5.