An experimental program was initiated to determine the friction factor in circular corrugated galvanized spiral ducts. The tests were performed in accordance with ASHRAE Standard 120-1999. The average absolute roughness was 0.74-mm (0.0024-ft), which places them in the “medium rough” duct roughness category as defined by ASHRAE (2005). An analysis was performed to calculate the required diameter of corrugated ducts required to convey the same volumetric flow rate of air at the same pressure loss per unit length as non-corrugated spiral ducts.

Units: Dual