Combined natural convection and thermal radiation in a square cavity with a nonuniformly heated plate

• Effect of surface radiation on natural convection in a cavity containing a nonuniformly heated thin plate is investigated.
• The surface radiation makes the entire cavity a thermally active one with a good homogenization of temperature field.
• The heat transfer rate for a vertically placed plate is always higher than that of a horizontally oriented one.
• The nonuniform heating results in a dual effect depending on the plate length and emissivity.

The present investigation deals with the combined effect of natural convection and surface radiation in an air filled square cavity with a nonuniformly heated thin plate placed horizontally or vertically at its center. The non-uniform heating is due to the non-linearly varying temperature of the plate. The vertical walls of the two dimensional cavity are cooled while the horizontal ones are insulated. The resulting coupled equations were solved using the finite volume method on a uniformly staggered grid system. Numerical simulations were carried out for a wide range of values of non-uniform heating, plate length and surface emissivity at a Rayleigh number of Ra=107Ra=107. It is found that the surface radiation makes the entire cavity thermally active with a good homogenization of the temperature field for both uniform and nonuniform heating of the plate. The heat transfer rate for a vertically placed plate is always higher than that of a horizontally oriented one. The increase of emissivity always enhances the heat transfer within the cavity, while the plate length can have both augmenting and dampening effects. The non-uniform heating results in a dual effect depending on the plate length and emissivity. The effect of uniform and non-uniform heating of the plate on the total and convective heat transfer rates is presented and discussed.