A NEW TYPE OF ROUGHENED HEAT TRANSFER SURFACE SELECTED BY FLOV VISUALIZATION TECHNIQUES
The flow of air around various types of roughness placed on a smooth surface has been studied in a small wind tunnel using flow visualization methods. The shapes of roughness considered were a cube in parallel and "diamond" orientations, a cylinder, and a transverse square rib. From the flow patterns alone it was possible to suggest the design of a good heat transfer surface having spaced out individual roughnesses. This surface consisted of cubes in the "diamond" orientation, i.e. their diagonals parallel to the flow, and spaced at 6.5 times their height. The performance of this surface with 0.047 ins. high "diamonds" was measured accurately, and found to equal the performance of a highly developed ribbed surface.