Heat transfer and friction characteristics for artificially roughened ducts with compound turbulators

An experimental investigation on heat and fluid flow characteristics of fully developed turbulent flow in a rectangular duct having repeated integral transverse chamfered rib-groove roughness on one broad wall has been carried out. Experiments encompassed the Reynolds number range of 3000–21,000; relative roughness pitch of 4.5–10, chamfer angle of 5°–30°, relative groove position of 0.3–0.6 and relative roughness height of 0.022–0.04. The effect of roughness parameters on Nusselt number and friction factor have been discussed and the results are compared with the results of square rib-grooved and smooth duct under similar flow conditions. The conditions for the best performance have been determined. Correlations for the Nusselt number and friction factor have been developed as a function of roughness parameters and flow Reynolds number.