Soo-Whan Ahn

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=30∘, 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 1000mm long has the cross section of 100×75mm2 at inlet and 100×100mm2 at exit. The ribbed walls are manufactured with a rib height (e)=10mm 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.

Heat Transfer and Frictions in the Rectangular Divergent Channel with Ribs on One Wall

An investigation of ribbed divergent channel was undertaken to determine the effect of rib pitch to height ratio on total friction factor and heat transfer results in the fully developed regime. The ribbed divergent rectangular channel with the channel exit hydraulic diameter (D ho ) to inlet channel hydraulic diameter (D hi ) ratio of 1.16 with wall inclination angle of 0.72 deg, at which the ratios (p/e) of 6,10, and 14 are considered. The ribbed straight channel of D ho /D hi =1.0 were also used. The ribbed divergent wall is manufactured with a fixed rib height (e) of 10 mm and the ratio of rib spacing (p) to height 6, 10, and 14. The measurement was run with range of Reynolds numbers from 24,000 to 84,000. The comparison shows that the ratio of p/e=6 has the greatest thermal performance in the divergent channel under two constraints; identical mass flow rate and identical pressure drop.