PERTANIKA JOURNAL OF SCIENCE AND TECHNOLOGY

Rib turbulators are largely utilized for enhancement of heat transfer in cooling channels of gas turbine blades. The present study focuses on the heat transfer, fluid flow and pressure drop study of perforated ribs fixed to the bottom wall of a two-pass square channel. The turbulent flow details for heat transfer and fluid flow for perforated ribs are simulated by using commercial software Comsol 5.3a with an established turbulence model i.e. Standard k-ε. The assiduity is towards analyzing the possible effects of varying inclination angle (0 to 30°) and shape of hole (cylinder to square) on heat transfer and friction factor characteristics for turbulent flow. The studied Reynolds number varies from 10000 to 50,000. Computations are carried out to determine inter-rib distribution of local heat transfer coefficient over the bottom ribbed wall. The phenomenon responsible for the heat transfer enhancement by perforated ribs is delineated. The results reveal that perforated ribs lead to enhancement of local heat transfer distribution (Nu/Nu_o) on the end wall downstream the ribs. Perforated ribs develop longitudinal vortices. These vortices cause an increase in flow mixing and turbulent kinetic energy. The square perforated ribs provide a 37.1-57.3% higher normalized average Nusselt number relative to the solid ribs, however induce high pressure drop. Overall, square perforated ribs (Case-3) provide the best thermal-hydraulic performance.