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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 = 10 7 . 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. [ABSTRACT FROM AUTHOR]

An internal natural convective flow arising in a closed square cavity due to the presence of two orthogonal and differentially heated plates is studied numerically. The flow is assumed to be laminar and two-dimensional. The Alternating Direction Implicit technique in association with the Successive Over Relaxation method is used to solve the coupled nonlinear governing equations. The heat and fluid flow interactions are studied for various combinations of plate–plate and plate–wall temperature ratios and different positions of the heated plates. When there are two plates with high temperature contrast the heat transfer mechanism inside the cavity is mainly ruled by the hotter one. In general convection heat transfer becomes strengthened when the vertical plate is hotter. [ABSTRACT FROM AUTHOR]