High rotation number heat transfer of a 45° rib-roughened rectangular duct with two channel orientations

An experimental study of heat transfer in a radially rotating rectangular channel of aspect ratio 1/2 with two opposite walls roughened by 45 degrees staggered ribs is performed. Heat transfer distributions along centerlines of two rib-roughened surfaces are measured for the radially outward airflow at test conditions of Reynolds number (Re), rotation number (Ro) and density ratio (Delta rho/rho) in the ranges of 5000-15,000, 0-2 and 0.07-0.28. The rotating test rig permits the generation of heat transfer data with Ro considerably higher than previous data ranges. A selection of experimental data illustrates the individual and interactive influences of Re, Ro and buoyancy number (Bit) oil local heat transfer with two channel orientations of 0 degrees and 45 degrees. With Ro varying from 0. 1 to 2, heat transfer ratios between rotating and static channels on the stable and unstable rib-roughened surfaces with 0 degrees (45 degrees) of channel orientation are in the ranges of 0.5-1.42 (0.5-1.49) and 1.08-2.73 ( 1.06-2.21) respectively. A set of heat transfer correlations for the test geometry with channel orientations of 0 degrees is derived to evaluate the local Nusselt number (Nu) in the periodically developed region with Re, Ro and Bit as the controlling flow parameters. (C) 2007 Elsevier Ltd. All rights reserved.