Effects of natural convection, wall thermal conduction, and thermal radiation on heat transfer uniformity at a heated plate located at the bottom of a three-dimensional rectangular enclosure

A numerical investigation is carried out to understand the effect of natural convection, surface thermal radiation, and wall thermal conduction on the heat transfer from a plate heat source located at the bottom of a three-dimensional rectangular enclosure. The distributions of convective, radiative, and total Nusselt numbers and the average Nusselt number at the surface of the heat source are obtained for the ranges of parameters of 1 × 102 ≤ Ra ≤ 1 × 106, 0 ≤ ϵ ≤ 1, 1 ≤ kr ≤ 15, and 0.5 ≤ AR ≤ 1.5. The increase of thermal radiation restrains the convective heat transfer, but increases the total heat transfer and the overall heat transfer uniformity. Useful correlations have been developed for the average and the standard deviation of the Nusselt numbers at the heat source.