An experimental and numerical study of turbulent heat transfer in orthogonally rotating two-pass ducts

Abstract

A heat transfer study from rotating two-pass ducts is presented. A rotating two-pass duct simulates the conditions in a serpentine coolant passage of a turbine blade. This work is mostly experimental with support from numerical predictions. The experiment is carried with two cross-sectional geometries, namely square and triangular cross-sections. In rotation, the Coriolis and rotational buoyancy forces cause different heat transfer patterns from the leading and trailing surfaces. Numerical computations with two equation turbulence models predict the complicated flow structure in rotation. Results show that secondary flow develops in rotation. This secondary flow redistributes the core flow and turbulence in an asymmetric fashion inside the coolant channel. The heat transfer from the first pass trailing and the second pass leading surfaces are augmented by rotation. However, the first pass leading and the second pass trailing surfaces show a decrease in heat transfer coefficient in rotation. The model orientation of the coolant channel has significant effect on the secondary flow and heat transfer pattern. Ribs placed oblique to the bulk flow generate secondary flows of their own. This secondary flow from ribs interacts with the secondary flow from rotation and creates new characteristic processes in heat transfer.