Heat Transfer Augmentation in a Divergent Duct with Angled Ribs

Heat transfer characteristics in the rectangular divergent duct with parallel angled ribs are experimentally compared with the straight smooth circular duct. The ribs with four different parallel angles ( α = 3 0 ∘ , 45 ∘ , 60 ∘ , and 90 ∘ ) are glued on the duct’s two opposite walls as well as on the duct’s one sided wall only, respectively. The 0.72 ∘ -inclined walls are installed at the two opposite walls of the rectangular divergent duct. The test section of 1000 mm long has the cross section of 1 0 0 × 7 5 mm2 at inlet and 1 0 0 × 1 0 0 mm2 at exit. The ribbed walls are manufactured with a rib height ( e ) = 1 0 mm and the ratio of rib spacing ( p ) to height( e ) = 10. The main findings are summarized that the increase in the dimensionless Nusselt number for the flow attack angles can be seen in the order of 90 ∘ , 30 ∘ , 60 ∘ , and 45 ∘ at the two opposite ribbed divergent wall ducts, in addition, the average Nusselt number in the divergent rectangular duct with two opposite ribbed walls is somewhat greater than in the ribbed straight cross-sectional rectangular duct.