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Fan Velocity Calculator

Formula

To calculate the Fan Velocity (Vfan):

$V_{fan} = \frac{CFM}{\left(\pi \left(\frac{D}{12}\right)^2 / 4\right) / 60}$

Where:

$V_{fan}$ is the fan velocity (ft/s)
$CFM$ is the rated cubic feet per minute of the fan (ft³/min)
$D$ is the diameter of the fan (in)

What is Fan Velocity?

Fan velocity describes the speed at which a fan moves air through its blades. It is a crucial parameter in the design and selection of fans for various applications, including ventilation, cooling, and air circulation. Higher fan velocity indicates a more powerful fan capable of moving air faster, which can be essential in environments requiring efficient air movement.

Example Calculation 1

Let's assume the following values:

Rated Cubic Feet per Minute ( $CFM$ ) = 2000 ft³/min
Diameter of the Fan ( $D$ ) = 24 inches

Using the formula:

Step 1: Calculate the area of the fan:

$\text{Area} = \pi \left(\frac{D}{12}\right)^2 / 4 = \pi \left(\frac{24}{12}\right)^2 / 4 = \pi \times 4 / 4 = \pi$

Step 2: Calculate the fan velocity:

$V_{fan} = \frac{2000}{\pi} / 60 \approx 10.61 \text{ ft/s}$

The Fan Velocity is approximately 10.61 ft/s.

Example Calculation 2

Let's assume the following values:

Rated Cubic Feet per Minute ( $CFM$ ) = 1500 ft³/min
Diameter of the Fan ( $D$ ) = 18 inches

Using the formula:

Step 1: Calculate the area of the fan:

$\text{Area} = \pi \left(\frac{D}{12}\right)^2 / 4 = \pi \left(\frac{18}{12}\right)^2 / 4 = \pi \times 2.25 / 4 = \pi / 1.7778$

Step 2: Calculate the fan velocity:

$V_{fan} = \frac{1500}{\pi / 1.7778} / 60 \approx 7.96 \text{ ft/s}$

The Fan Velocity is approximately 7.96 ft/s.