Air velocities in ducts and pipes should not exceed certain limits to avoid high pressure loss and unacceptable noise generation. The values below can be used as guidelines for some typical applications.
|Air Ducts||Air Velocity|
|Combustion air duct||12 - 20||2400 - 4000|
|Air inlet to boiler room||1 - 3||200 - 600|
|Warm air for house heating||0.8 - 1.0||150 - 200|
|Vacuum cleaning pipe||8 - 15||1500 - 3000|
|Compressed air pipe||20 - 30||4000 - 6000|
|Ventilation ducts in hospitals||5 - 8||1000 - 1500|
|Ventilation ducts in office buildings||7 - 11||1200 - 2000|
Systems for ventilation and air handling - air change rates, ducts and pressure drops, charts and diagrams and more.
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.
Head loss or major loss in air ducts - equations and online calculator for rectangular and circular ducts - Imperial and SI units.
Minor loss coefficient diagrams for air ductwork, bends, expansions, inlets and outlets - SI units.
Required duct area vs. air flow.
Air flow volume, duct size, velocity and dynamic pressure.
The equal friction method for sizing air ducts is easy and straightforward to use.
Calculate velocities in circular and rectangular ducts - imperial and SI-units - online calculator.
The velocity reduction method can be used when sizing air ducts.
Velocity diagram for rectangular air ducts - metric units.