Effects of angled ribs on turbulent heat transfer and friction factors in a rectangular divergent channel

Abstract

Heat transfer and friction factors of fully developed turbulent flows in the stationary rectangular divergent channel with parallel angled ribs have been investigated experimentally. Four different parallel angled ribs (α = 30°, 45°, 60°, and 90°) are placed to the channel's two opposite walls as well as to the channel's one sided wall only, respectively. The ribbed rectangular divergent channel has the inclination angle of 0.72° at the left and right walls, corresponding to Dho/Dhi = 1.16. The divergent channel has the cross sections of 100 × 75 mm2 at inlet and 100 × 100 mm2 at exit. The ribbed walls are manufactured with a fixed rib height (e) = 10 mm and the ratio of rib spacing (p) to height (e) = 10. The measurement was conducted within the range of Reynolds numbers from 15,000 to 89,000. Thermal performances of the ribbed rectangular divergent channel with different flow attack angles of ribs are compared with the smooth straight circular channel under three constraints: identical mass flow rate, identical pumping power, and identical pressure drop.