Minor loss coefficient diagrams for air ductwork, bends, expansions, inlets and outlets - SI units
Minor loss in air ducts based on a summarized minor loss coefficient and air flow velocity can be estimated with the diagram below:
- 1 Pa = 1 N/m2 = 1.4504x10-4 lb/in2 = 1x10-5 bar = 4.03x10-3 in water = 0.336x10-3 ft water = 0.1024 mm water = 0.295x10-3 in mercury = 7.55x10-3 mm mercury = 0.1024 kg/m2 = 0.993x10-5 atm
Minor loss for some common ductwork components like bends, expansions, inlets and outlets can be estimated with the diagrams below.
Minor Loss Coefficients - Bends
The minor loss coefficients in 90o bends can be estimated with the diagram below.
The minor loss in bends 0 - 180o can be estimated with the equation
ξ0-180 = ξ90 α / 90 (1)
ξ0-180 = minor loss coefficient for the bend with the actual angle
ξ90 = minor loss coefficient for the 90o bend according the diagram above
α = angle of the actual bend
The minor loss coefficient in a 90o bend like the one below is 1.0.
Minor Loss Coefficients - Expansions
Minor Loss Coefficients - Inlets
Minor Loss Coefficients - Outlets