Head loss and air flow velocity for some common duct sizes and air flow volumes can be taken from the table below:
|Air Volume |
|Head Loss (inches water gauge per 100 feet duct) |
| Air velocity (ft/min) |
|Duct Size (inches)|
Air velocity should not exceed certain limits to avoid unacceptable noise generation.
This pressure loss calculator is based on formula (1) with input and output values modified for SI units.
This Excel template can be used to calculate velocity and friction loss in air ducts.
The chart below can be used to estimate friction loss in air ducts.
The default values are for air flow 400 cfm (680 m 3 /h) , duct size 8 in (200 mm) and friction loss 0.28 inH2O/100ft (2.3 Pa/m) .
Download and print Air Ducts Friction Loss Diagram!
Air Duct Velocity
Systems for ventilation and air handling - air change rates, ducts and pressure drops, charts and diagrams and more.
Typical air duct velocities in applications like ventilation systems or compressed air systems.
A major friction loss diagram for air ducts - Imperial units ranging 10 - 100 000 cfm.
A major friction loss diagram for air ducts - SI units.
Air flow volume, duct size, velocity and dynamic pressure.
The equal friction method for sizing air ducts is easy and straightforward to use.
Duct systems are commonly divided into three pressure classifications.
Calculate velocities in circular and rectangular ducts - imperial and SI-units - online calculator.
The velocity reduction method can be used when sizing air ducts.
Ductwork air leakage classes.
Rectangular equivalent diameter for air flows between 100 - 50000 cfm.
Convert rectangular and oval duct geometry to a equivalent circular diameter - online calculator with imperial and SI-units.
Calculate hydraulic diameter for pipes and ducts.
A rough guide to maximum air volume capacity of circular ducts in comfort, industrial and high speed ventilation systems.
Standard dimensions of spiral ducts - Imperial units.
Recommended air velocities in ventilation ducts
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