An experimental investigation was conducted to study the heat transfer and friction characteristics of a rectangular channel roughened by arrays of staggered detached ribs. The rectangular channel (with aspect ratio equal to four) having two opposite-walls (lower and upper) heated at uniform heat flux. The aluminum ribs are of rectangular cross section with (H) = 6 mm and (w) = 3 mm, with H/Dh= 0.091. The ribs are positioned at a small distance from the two opposite walls of the channel (clearance C). The face-to-face distance (pitch, Pi) between any two consecutive ribs is 60 mm (Pi/H=10). The experiments were conducted with clearance ratios (C/H = 0, 0.17, 0.33, 0.67, 1, and 1.5) from the two opposite walls of the channel and Reynolds number ranged from 14480 to 31850. Friction factor, local and averaged Nusselt number were measured for the ribbed (detached and non-detached) channel as well as for the non-ribbed channel. Results showed that the measured local Nusselt number distributions for ribbed channel were non-uniform along streamwise channel direction. The friction factor for the ribbed channel with detached ribs (C/H =1) was increased, up to 45 times the corresponding values for fully developed smooth channel flows. Under the same mass flow rate constraint, the highest values of Nuav/Nuo obtained for the detached-rib channel with C/H = 0.17, are between 2.9 and 3.5, followed by the detached-rib channel with C/H = 1.0, with Nuav/Nuo between 2.8 and 3.25. A thermal performance under constant pumping power constraints improvements as high as 55% (1.55 times), relative to a smooth channel, was obtained for detached-rib channel with C/H = 0.17. A poorer thermal performance (Nuav/Nuo*< 1.0) was obtained for the detached-rib channel with C/H =1.5 for the test ranges of Reynolds number.