NUMERICAL STUDY OF NATURAL CONVECTION OVER DISCRETE ROUGHNESS ELEMENTS ON A VERTICAL HEATED WALL OF AN ENCLOSURE.
Date of Presentation
A numerical analysis of two-dimensional natural convection flow over two-dimensional single and repeated roughness elements attached to the heated wall of an enclosure is reported. The objective is to study the influence of these roughness elements, which are on the order of the boundary layer thickness, on the laminar natural convection heat transfer. Quantitative predictions of fluid flow and heat transfer are obtained by a finite-difference method for a wide range of parameters. The predicted results show that the effect of these roughness elements on heat transfer is only confined to a small region of the surface. It is also found that the average Nusselt number for a vertical wall in the presence of roughness is slightly higher than that for a smooth wall. This is attributed to the increase in the surface area when roughness elements are employed. However, this increase in heat transfer is not proportional to the increase in the surface area because there are stagnant fluid regions just below and above each of the roughness elements which tend to inhibit the heat transfer locally.
Loehrke, R. I.
NUMERICAL STUDY OF NATURAL CONVECTION OVER DISCRETE ROUGHNESS ELEMENTS ON A VERTICAL HEATED WALL OF AN ENCLOSURE..