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:

References

About the Author

C. Taylor embarked on a professional writing career in 2009 and frequently writes about technology, science, business, finance, martial arts and the great outdoors. He writes for both online and offline publications, including the Journal of Asian Martial Arts, Samsung, Radio Shack, Motley Fool, Chron, Synonym and more. He received a Master of Science degree in wildlife biology from Clemson University and a Bachelor of Arts in biological sciences at College of Charleston. He also holds minors in statistics, physics and visual arts.

Photo Credits

stack image by John Sfondilias from Fotolia.com