Duct Velocity
Air Duct Velocity - Imperial Units
Air velocity in a ventilation duct can be calculated in imperial units as
v i = q i / A i
= q i / [ π (d f / 2) 2 )]
= q i / [ π ((d i / 12) / 2) 2 )]
= (576 / π) ( q i / d i 2 )
= 144 q i / (a i b i ) (1)
where
v i = air velocity (ft/min)
q i = air flow (ft 3 /min)
A i = area of duct (ft 2 )
d f = diameter of duct (ft)
d i = diameter of duct (in)
a i = width of duct (in)
b i = width of duct (in)
Example - Air Flow Velocity in a Duct
The velocity in a 12 inch duct with air flow 1000 cfm can be calculated as
v i = (576 / π ) (1000 cfm) / (12 in) 2 )
= 1273 (ft/min)
Air Flow Velocity Calculator - Imperial Units
Air velocity can be calculated with the calculator below. Add air volume - q - and diameter - d - (or length a and b ).
or alternatively
Related Mobile Apps from The Engineering ToolBox
- free apps for offline use on mobile devices
Air Duct Velocity - SI Units
Air velocity in a duct can be calculated in SI units
v m = q m / A m
= q m / (π (d m / 2) 2 )
= 4 q m / (π d m 2 )
= q m / (a m b m ) (2)
where
v m = air velocity (m/s)
q m = air flow (m 3 /s)
A m = area of duct (m 2 )
d m = diameter of duct (m)
a m = width of duct (m)
b m = width of duct (m)
Example - Air Flow Velocity in a Duct
The velocity in a rectangular 0.5 m x 0.5 m duct with air flow 1 m 3 /s can be calculated as
v m = (1 m 3 /s) / ((0.5 m) (0.5 m))
= 4 (m/s)
Air Flow Velocity Calculator - SI Units
Air velocity can be calculated with the calculator below. Add air volume - q - and diameter - d - (or length a and b ).
or alternatively
Air Ducts - Velocity Diagram
The chart below can be used to estimate velocities in air ducts.
The default values are for air flow 400 cfm (680 m 3 /h) , duct size 8 in (200 mm) and velocity 1150 fpm (5.8 m/s) .
Download and print Air Ducts - Velocity Diagram!
- make 3D HVAC models with the Engineering ToolBox Sketchup Extension
Related Topics
• Ventilation
Systems for ventilation and air handling - air change rates, ducts and pressure drops, charts and diagrams and more.
Related Documents
Air Duct Velocities
Typical air duct velocities in applications like ventilation systems or compressed air systems.
Air Ducts - Friction Loss Diagram
A major friction loss diagram for air ducts - Imperial units ranging 10 - 100 000 cfm.
Air Ducts - Friction Loss Diagram
A major friction loss diagram for air ducts - SI units.
Air Ducts - Major Friction Head Loss, Online Calculator
Head loss or major loss in air ducts - equations and online calculator for rectangular and circular ducts - Imperial and SI units.
Air Ducts - Sizing
Required duct area vs. air flow.
Air Ducts - Velocity Diagram
Air flow volume, duct size, velocity and dynamic pressure.
Circular Ducts - Dimensions
Standard size of circular ventilation air ducts.
Colebrook Equation
Friction loss coefficients in pipes, tubes and ducts.
Duct Sizing - the Equal Friction Method
The equal friction method for sizing air ducts is easy and straightforward to use.
Ducts - Cross-Sectional Area vs. Diameter
Circular ducts sross-sectional areas.
Ducts - Sheet Metal Gauges
Thickness of sheet metal used in ductwork.
Ducts or Pipes through Steel Joists - Maximum Sizes
Maximum sizes of ducts or pipes through K series joists.
Ducts Sizing - the Velocity Reduction Method
The velocity reduction method can be used when sizing air ducts.
Ductwork - Seal Classes
Ductwork air leakage classes.
Exhaust Outlets - Capturing Air Velocities
Capturing air velocity in front of an exhaust outlet - online exhaust outlet velocity calculator.
Fluid Flow - Hydraulic Diameter
Calculate hydraulic diameter for pipes and ducts.
HVAC Ducts - Air Velocities
Recommended air velocities in HVAC ducts.
Sizing Circular Ducts
A rough guide to maximum air volume capacity of circular ducts in comfort, industrial and high speed ventilation systems.
Spiral Ducts - Dimensions
Standard dimensions of spiral ducts - Imperial units.
Velocity Classification of Ventilation Ducts
Recommended air velocities in ventilation ducts
Velocity Units Converter
Convert between speed and velocity units like m/s, km/h, knots, mph and ft/s.