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 degrees-30 degrees, 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. (c) 2007 Elsevier Ltd. All rights reserved.