What is Darcy-Weisbach?

ΔP=f×L/D×ρv²/2. Friction factor f from Colebrook equation.

Recommended duct velocity?

Main: 5-8 m/s. Branch: 3-5 m/s. Noise-sensitive: 2-4 m/s.

Sheet metal: 0.03mm. Galvanized: 0.15mm. Spiral: 0.9mm. Flex: 3mm.

Add equivalent lengths. 90° elbow ≈ 10-15D. Or use loss coefficient method.

Convert to equivalent round: d_eq=1.3(ab)^0.625/(a+b)^0.25.

Free Engineering Tool — #159

ΔP=f×L/D×ρv²/2 for round ducts. Shows velocity and Reynolds number.

Darcy-WeisbachRound Duct

Total Pressure Drop

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ΔP per Meter

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Air Velocity

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Reynolds Number

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