An experimental investigation of heat transfer and fluid flow in a rectangular duct with broken V-shaped ribs

An experimental investigation of heat transfer and fluid flow in a rectangular duct roughened by broken V-shaped ribs pointing upstream was carried out. The rectangular duct had art aspect ratio of 1/8, and the Reynolds number range was from 1000 to 6000. Liquid Crystal Thermography (LCT) was used to obtain the detailed heat transfer distributions on the ribbed wall. The main observed characteristics include spanwise variation, local maxima, and saw-tooth fashion along the streamwise direction. These features were correlated and explained by the detailed velocity structures, observed by Particle Image Velocimetry (PIV). The flow characteristics introduced by ribs include altered spanwise profile of the mean flow velocity, a complicated secondary flow over the cross section, and flow separation and reattachment along the streamwise direction. In addition, a comparison of overall thermal and hydraulic performance with previously tested continuous ribs was conducted It was found that the broken ribs had better overall performance in the high Reynolds number range.