Abstract
A brief study of pressure loss in flexible ducts was undertaken to provide a suitable basis for judging the adequacy of presently published data provided by the duct manufacturers, and to evaluate the need for further research on the subject. For the 2 1/2-, 4-, and 6-inch-diameter brand A ducts tested, losses measured in the laboratory in perfectly straight ducts were approximately 55%, 30%, and 45% higher, respectively, than those shown in the manufacturers’ friction chart. Losses in bends of various R/D ratios in the three duct sizes at a velocity of 3000 fpm were found to average approximately 60%, 380%, and 235% greater than those given by the manufacturer. For the 4- and 6-inch-diameter brand B ducts tested, losses given for straight duct by the manufacturer were approximately 50% and 25% higher, respectively, than those determined by test. The average losses in bends at an air velocity of 3000 fpm were found to be approximately 100% and 120% higher than those given by the manufacturer.