An Experimental and Numerical Investigation of Heat Transfer Enhancement Using Annular Ribs in a Tube

In this study, heat transfer and fluid flow features were numerically and experimentally studied in a circular steel passage of length 50 cm with an outer diameter of 40 mm and inner diameter of 37 mm under a constant surrounding temperature of 673 K for Reynolds numbers Re=10,800, 12,900, and 15,700, in order to simulate a gas turbine blade cooling passage. Turbulence was simulated using ANSYS - FLUENT (version 16.1), and the (k-epsilon) turbulence model was utilised. The rib constructions (of 5 x 10 mm equilateral triangular cross-section) were fixed inside the circular passage and diverged by 5 cm. The results of temperature and velocity distribution along the circular passage's centreline for the smooth passage were compared with those of a circular passage fitted with these enclosed ribs. An improvement in the rate of heat transfer, especially at Re=12,900, was observed in the tube with ribs, with a rate of heat transfer increase of 84.3% compared to the smooth case; the ribbed tube was also observed to have a greater performance factor for turbulent flow.