If a system is using a 12" round flexible duct with an air velocity of 600 CFM, what is the air velocity measurement expressed in feet per minute?

To determine the air velocity measured in feet per minute, you need to understand the relationship between cubic feet per minute (CFM) and the cross-sectional area of the duct.

The formula to calculate air velocity is:

[

\text{Velocity (fpm)} = \frac{\text{CFM} \times 144}{\text{Area (sq ft)}}

]

First, calculate the cross-sectional area of a 12” round duct. The radius of the duct is half of the diameter, so:

[

\text{Radius} = \frac{12}{2} = 6 \text{ inches} = 0.5 \text{ feet}

]

The area can be calculated using the formula for the area of a circle:

[

\text{Area} = \pi r^2

]

[

\text{Area} = \pi (0.5)^2 = \pi \times 0.25 \approx 0.785 \text{ sq ft}

]

Now, using the CFM value of 600:

[

\text{Velocity} = \frac{600 \times 144}{0.785}

]

[

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