Heat transfer and pressure drop measurements were conducted to study the thermal-hydraulics in a square, round-edged channel roughened by ribs (e/D-h=0.0638, p/e=10) on one wall at Reynolds numbers ranging from 5.0x10(4) to 2.5x10(5). Three variously shaped ribs were investigated: Transverse ribs with square cross sections, transverse ribs, and upstream directed 60 degrees V-shaped ribs with round-edged rib front and rear surfaces. Friction factors, Nusselt number ratios, roughness functions, and the thermal performance were presented. The highest heat transfer and best thermal performance is reached by the upstream directed V-shaped ribs.