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Engineering ToolBox > Air Ducts Minor Loss Coefficient Diagrams

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 90^o bends can be estimated with the diagram below.

The minor loss in bends 0 - 180^o can be estimated with the equation

ξ_0-180 = ξ₉₀ α / 90   (1)

where

ξ_0-180 = minor loss coefficient for the bend with the actual angle

ξ₉₀ = minor loss coefficient for the 90^o bend according the diagram above

α = angle of the actual bend

The minor loss coefficient in a 90^o bend like the one below is 1.0.

Minor Loss Coefficients - Expansions

Minor Loss Coefficients - Inlets

Minor Loss Coefficients - Outlets