The present work submits an experimental Work on the heat transfer and friction loss characteristic, employing a tube finned heating surface kept at a constant temperature in a rectangular channel. The tube fins attached on the surface (o.d. = 29 mm) were arranged as either in-line or staggered. The parameters for the study were Reynolds number (3700-30000), depending on hydraulic diameter, the distance between the tube fins in the flow direction (S-y/D = 1.72-3.45) and the fin arrangement. The change in the Nusselt number with these parameters was determined. For both tube fin arrangements, it was observed that increasing Reynolds number increased Nusselt number, and maximum heat transfer occurred at S-y/D = 2.59. Thermal performances for both arrangements were also determined and compared with respect to heat transfer from the same surface without fins. With staggered array, a heat transfer enhancement up to 25 per cent for S-y/D = 3.45 in staggered array was achieved in constant pumping power. Copyright (C) 2002 John Wiley Sons, Ltd.