Prediction of turbulent flow and heat transfer within rotating U-shaped passages

Numerical predictions of three-dimensional flow and heat transfer in the rotating serpentine passages with and without rib turbulators were presented. The coolant air is pressurized and its operating conditions are selected to closely match with the real turbine operating parameters. Two different arrangements of rib turbulators were studied: (1) transverse ribs on the leading and trailing walls; (2) transverse ribs on all four walls. The rib height to hydraulic diameter ratio (h/D_h) is 0.143; the rib pitch to height ratio (s/e) is 7. Results for the roughened rib serpentine passages were compared with those of smooth ones found in the literature. It is disclosed that a significant enhancement is achieved by means of rib turbulators in a serpentine passage in steady state as well as in rotating state. In the radially-outward flow passages, effect of rotation on heat transfer is relatively prominent. The secondary flows induced by the Coriolis forces are most intensive in the channel with four ribbed surfaces. The heat transfer after 180° sharp turn in the smooth channel is influenced more by the sharp-turn induced flow than in the roughened rib ones.