# Air Ducts Minor Loss Coefficient Diagrams

## Minor loss coefficient diagrams for air ductwork, bends, expansions, inlets and outletsĀ - SI units

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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/m*^{2}= 1.4504x10^{-4}lb/in^{2}= 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/m^{2}= 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}= ξ_{90}α / 90 (1)

where

ξ_{0-180}= minor loss coefficient for the bend with the actual angle

ξ_{90}= 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

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