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?

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?

• A. 600 fpm
• B. 764 fpm
• C. 800 fpm
• D. 900 fpm

Answer: (B)

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: \[ \text{Velocity} = \frac{600 \times 144}{0.785} \] \[ \text

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}

]

[

\text