Experimental results of the flow resistance offered by modern, round, galvanized sheet-metalducts are presented in this paper. The experimental program is also described. Tests were done on ducts having nominal diameters of 6, I0, 14, 18, 24, 30, and 36 inches, all being of longitudinally welded seam construction with nominal joint spacing of 4 feet. Tests were also done on 10-inch diameter spiral duct of Unribbed, single-, double-, and triple-ribbed construction and on a 14-inch diameter triple-ribbed duct, all having nominal joint spacing of 12 feet. Joint types of beaded slip, Vanstone, drawband, and welded were examined for the 6-inch and 10-inch welded-seam ducts. All other tests involved only beaded slip joints. Experimental results were cast in terms of an absolute roughness, which in each case was less than the 0.0005 feet currently used as the basis for ASHRAE’s duct design chart.

Units: I-P