Fluid Flow and Heat Transfer of Natural Convection over Upward-Facing, Horizontal, Heated Plate Shrouded by a Parallel Insulated Plate

摘要

The present paper describes experimenta results on the fluid flow and heat transfer of natural convection between a horizontal, heated plate facing upward and an insulated cover plate. The experiments were carried out with water. The width of the test plates W and their gaps H were changed from W = 50 to 250 mm and H = l0 to 30 mm and ∞ (no cover plate). The visualization studies with dye and liquid crystal thermometry revealed that the roll cells whose axes are perpendicular to the flow direction appear and become dominant over the heated plate on decreasing the gap. These roll cells inhibit the heat transfer, and thus, the heat transfer coefficients become smaller than those without a cover plate. It was found that the flow and heat transfer in the region near the plate edges are unaffected by the cover plate. The conditions of the above reduced heat transfer were determined empirically. Moreover, nondimen- sional correlations for the local and the overall heat transfer coefficients of the heated plates are proposed based on the present heat transfer results.