Effect of inclined ribs on heat transfer behavior in a square channel

The research work presents the study of heat transfer in a heat exchanger channel inserted with 45° inclined ribs. The test channel has a square section with a uniform wall heat flux condition. The fluid flow and heat transfer characteristics are presented for Reynolds numbers based on the hydraulic diameter of the channel ranging from 4000 to 40,000. Two rib arrangements, namely, in-line and staggered arrays, a single pitch equal to three times of channel height (=3H), and three rib to channel height ratios, e/H=0.1, 0.15, and 0.2 are introduced. The experimental result of heat transfer in terms of Nusselt number and pressure drop in terms of friction factor are compared between the ribbed channel and the smooth channel. The inclined rib with e/H=0.2 gives higher heat transfer and friction factor than the e/H=0.15, 0.1 and the smooth channel. It is worth nothing that the heat transfer and pressure drop for the in-line arrangement provides the higher value of Nusselt number and friction factor than the staggered one for all rib height ratios.