What is the velocity of air in a duct measuring 20" x 20" that is supplying 2000 CFM?

To determine the velocity of air in a duct, the formula used is:

[ Velocity (FPM) = \frac{CFM \times 144}{Area (square inches)} ]

In this case, the duct size is 20" x 20", which allows us to calculate the cross-sectional area of the duct. The area can be calculated as follows:

[ Area = Width \times Height = 20 , in \times 20 , in = 400 , square , inches ]

Next, we input the values into the velocity formula. The airflow is given as 2000 CFM:

[ Velocity = \frac{2000 , CFM \times 144}{400 , square , inches} ]

This simplifies to:

[ Velocity = \frac{288000}{400} ]

[ Velocity = 720 , FPM ]

This confirms that 720 FPM is the correct velocity of air in the duct supplying 2000 CFM. Understanding the relationship between airflow (CFM), cross-sectional area of the duct, and the resulting air velocity is essential for tasks involving HVAC systems and duct design.