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Duct Roughness Factors Table

Fluids Engineering Table of Contents
Hydraulic and Pneumatic Engineering

Roughness factors listed in Table 1, are recommended for use with Colebrook Formula.

Duct Roughness Factors Table

Duct Type/Material	Absolute Roughness ε, ft
	Range	Roughness Category
Drawn tubing (Madison and Elliot 1946)	0.0000015	Smooth 0.0000015
PVC plastic pipe (Swim 1982)	0.00003 to 0.00015	Medium smooth 0.00015
Commercial steel or wrought iron (Moody 1944)	0.00015
Aluminum, round, longitudinal seams, crimped slip joints, 3 ft spacing (Hutchinson 1953)	0.00012 to 0.0002
Galvanized steel, round, longitudinal seams, variable joints (Vanstone, drawband, welded. Primarily beaded coupling), 4 ft joint spacing (Griggs et al. 1987)	0.00016 to 0.00032	Average 0.0003
Galvanized steel, spiral seams, 10 ft joint spacing (Jones 1979)	0.0002 to 0.0004
Galvanized steel, spiral seam with 1, 2, and 3 ribs, beaded couplings, 12 ft joint spacing (Griggs et al. 1987)	0.00029 to 0.00038
Galvanized steel, spiral seams, 10 ft joint spacing (Jones 1979)	0.0002 to 0.0004
Galvanized steel, spiral seam with 1, 2, and 3 ribs, beaded couplings, 12 ft joint spacing (Griggs et al. 1987)	0.00029 to 0.00038
Galvanized steel, rectangular, various type joints (Vanstone, drawband, welded. Beaded coupling), 4 ft spacinga (Griggs and Khodabakhsh-Sharifabad 1992)	0.00027 to 0.0005
Phenolic duct, aluminum foil on the interior face, sections connected with a four-bolt flange and cleat joint (Idem and Paruchuri 2018)
5 ft spacing:	0.00049 to 0.00128
10 ft spacing	0.00025 to 0.00098
Wright Friction Chart: Galvanized steel, round, longitudinal seams, 2.5 ft joint spacing,	0.0005	-
Flexible duct, nonmetallic and wire, fully extended (Abushakra et al. 2004; Culp 2011)	0.0003 to 0.003	Medium rough 0.003
Galvanized steel, spiral, corrugated,b Beaded slip couplings, 10 ft spacing (Kulkarni et al. 2009)	0.0018 to 0.0030
Fibrous glass duct liner, air side with facing material (Swim 1978)	0.005
Fibrous glass duct liner, air side spray coated (Swim 1978)	0.015	Rough 0.01
Flexible duct, metallic corrugated, fully extended	0.004 to 0.007
Concrete (Moody 1944)	0.001 to 0.01

^a Griggs and Khodabakhsh-Sharifabad (1992) showed that ε values for rectangular duct construction combine effects of surface condition, joint spacing, joint type, and duct construction (cross breaks, etc.), and that the ε-value range listed is representative.
^b Spiral seam spacing was 4.65 in. with two corrugations between seams. Corrugations were 0.75 in. wide by 0.23 in. high (semicircle).

Reference:

ASHRAE Handbook of Fundamentals - 2021