How to Calculate Stack Exit Velocity

The dispersion of smoke and gases depends on stack exit velocity.
••• stack image by John Sfondilias from Fotolia.com

Stack exit velocity measures the speed at which gases leave a stack. This measurement allows us to estimate pollution effects by determining the height and ultimate distance the gases will travel. The calculation is remarkably easy to perform, because it requires nothing more than the gas flow rate and the area of the stack's opening.

    Determine the actual gas flow rate, expressed in ACFM (actual cubic feet per minute), and the diameter of the stack's opening.

    Calculate the area of the stack's cross section, at the opening. As an example, suppose the diameter of the opening is 6 feet, and pi is a known constant at 3.14. You would calculate the area as follows:

    And since:

    Then:

    Therefore:

    Now, we'll repeat the calculation with known variables:

    Therefore:

    Calculate the stack exit velocity using the formula:

    Based on the previous example, assume the actual gas flow rate is 60,000 ACFM:

    Therefore:

Related Articles

How to Calculate Fume Hood Velocity
How to Calculate the Fluid Flow Through a Hole in a...
How to Calculate GPM from PSI for Water
How to Convert Moles to Pressure
Volume Vs. Mass Density
How to Convert the Volume of Co2 Gas to Liquid
How to Calculate Steam Velocity
How to Find Partial Pressures
How to Calculate the Area of a Pipe
How to Convert Vapor Pressure to Concentration
How to Calculate Hydraulic Cylinder Tonnage
How to Calculate the Volume of a Container
How to Calculate the Height of a Cone From the Volume
How to Calculate CFM to MPH
How to Calculate Heat Loss During Pipeline Depressurization
How to Calculate Diffusion Rate
How to Calculate Fume Hood Velocity
How to Calculate the Gas Loss in a Pipe
What Happens When the Pressure and Temperature of a...
How to Find the Number of Moles of Co2