Static pressure losses in nonmetallic flexible duct
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This study measured airflow static pressure losses through nonmetallicflexible ducts in compliance with ANSI/ASHRAE Standard 120-1999, Method of Testing to Determine Flow Resistance of HVAC Ducts and Fittings. Duct sizes of 6, 8, and 10 in. (15.2, 20.3, and 25.4 cm) were tested in a positive pressure, blow-through configuration. An "as-built" test protocol expands the test configurations specified by Standard 120. Previous work by researchers at Lawrence Berkeley National Laboratories (LBNL) using draw-through configurations showed that the existing data for flexible duct losses exhibit errors greater than 70% from previously published data. Results of the current tests extend the existing ASHRAE/A CCA data for flexible duct, which do not include pressure loss data for flexible ducts that are compressed beyond approximately 4%. This study measured pressure loss at fully stretched, 4% compression, 15% compression, 30% compression, and 45% compression. The data exhibit higher pressure losses than prior ACCA or ASHRAE data. Compression ratios above 15% compression can exceed ten times the pressure loss found in fully stretched flexible duct of the same diameter. © 2007 ASHRAE.
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