Coupled thermal radiation and natural convection heat transfer in a cavity with a heated plate inside

This paper reports a fundamental theoretical study made to understand the interaction of surface radiation and natural convection in an air filled cavity with a centrally placed thin heated plate. The vertical walls of the cavity are cooled while the horizontal ones are insulated. The thin plate is assumed to be isothermal and is placed horizontally or vertically. The governing equations were solved using a finite volume method on a uniformly staggered grid system. The effects of the pertinent parameters, viz., Rayleigh number (105 ⩽ Ra ⩽ 107), plate length (0.25 ⩽ D ⩽ 0.75) and emissivity (0 ⩽ ε ⩽ 1) are investigated in detail. In general the results indicate a better homogenization of temperature field within the cavity by radiation. It is also found that the contribution of the convective mechanism to the overall heat transfer increases with emissivity when the plate is horizontally placed whereas decreases when it is vertically placed. This study demonstrates that any model representing a situation of this kind that ignores surface radiation leads to erroneous predictions.

► We study the effect of radiation on natural convection in a cavity with a heated plate. ► The heated plate is placed horizontally or vertically at the center of the cavity. ► The surface radiation makes the temperature distribution uniform inside the cavity. ► The average Nusselt number increases with the emissivity and the Rayleigh number. ► The heat transfer rate is higher when the plate is oriented vertically.