Effect of non-traditional rib-profiles on heat transfer and friction in turbulent channel flows
1996 by the American Institute of Aeronautics and Astronautics, Inc All rights reserved. An experimental study with computational verification of wall heat transfer and friction characteristics of a fully-developed turbulent air flow in a rectangular channel with transverse ribs of non-traditional profiles is reported. Tests were performed for Reynolds numbers ranging from 14,000 to 90,000. The pitch-to-rib height ratio, P/e, was kept at 10 and rib height-to-channel hydraulic diameter ratio, e/Dh, was kept at 0.125. The channel length-to-hydraulic diameter ratio, L/Dh, was 20. The heat transfer coefficient and friction factor values were enhanced using turbulators of different shapes namely, square, circular, triangular, slant edged, and semicircular. The channel with square ribs produces highest heat transfer augmentation and pressure drop. The friction roughness function, R(e+), was almost constant over the entire range of tests performed and was within comparable limits of the previously published data. The heat transfer roughness function, G(e+), was also compared well with previous work. The computaional analysis was performed and found in close agreement with experimental results and prior computational work. Results of this investigation could be used in various applications of channel turbulent flows involving different shape rib-profiles on roughened walls. The computational aspect can be utilized in predictiing local values of heat and friction characteristics and to locate high temperature regions, or hot spots.