HEAT-TRANSFER AND FRICTION FACTOR MEASUREMENTS IN DUCTS WITH STAGGERED AND IN-LINE RIBS

The combined effects of rib alignment and channel aspect ratio on the distributions of the local heat transfer coefficient and on the friction factors for developing and fully developed flow in short square and rectangular channels (L/D(H) = 13.5-18) with a pair of opposite rib-roughened walls were determined for Reynolds numbers ranging from 13, 000 to 130, 000. The channel aspect ratios are 1/2 and 1 and the rib alignment configurations are arranged as staggered and in-line types, respectively. The pitch to rib height ratio is 5.31 for all test channels. The local heat transfer distributions on the bottom rib-roughened wall from the channel entrance to the downstream region are presented and discussed. Semi-empirical heat transfer and friction correlations are developed, and the results are compared with those of previous investigations for similarly configured channels, which were roughened by regularly spaced transverse ribs.