This research aims to study the numerical investigation of heat transfer and fluid flow characteristics of multiple cylinder v-rib with combined staggered rib in a rectangular duct. The conventional heat exchangers were usually used as flat plate rib shape leading to increase pressure drop from obstructive flow. Therefore, the inclined cylinder V-shaped rib was modified to use in this work. The cylinder shape rib increases pressure drop (less than flat plate rib) because of the rounded shape of cylinder v-rib creating the smooth flow of the fluid. The heat transfer and the pressure drop are represented in term of Nusselt number (Nu) Friction factor (f), respectively. The relation of Nu with f values was analysed to obtain the Thermal performance enhancement factor (TEF). The velocity vector and temperature contours were examined by the Computational Fluid Dynamics (CFD). The data was compared with the experimental result. The channel size was simulated at the rectangular duct height (H) of 30 mm and width (W) of 300 mm with rib-to channel-height ratios (e/H) at 0.1, 0.2, 0.3 and the angle of attack (α) at 30°. Air was used as the test fluid. Reynolds number (Re) was varied from 12,681 to 35,000 with constant heat flux on the bottom wall of the tested section. Simulation results represented the velocity vectors and temperature contours. It was found that the increasing of e/H leading to provide high co-rotating of the flow. The highest TEF (TEF = 2.05) was observed at 30(, e/H 0.3 and Re 12,618.