Heat transfer and turbulent flow in a rectangular channel having one roughness rib

Experiments on heat transfer and turbulent flow in a rectangular channel with one roughness rib were performed to investigate effects of roughness shape, Reynolds number, and channel width. Seven types of roughness shape were used, and Reynolds numbers, based on channel hydraulic diameter, varied from 3,300 to 44,000. Water was the working fluid. It is found that the local Nusselt numbers in reattachment region are 1.5 to 4 times as large as those in a smooth channel. The increase of Nusselt number owing to flow reattachment depends on roughness shape, and is accentuated as the Reynolds number decrease. (author)