How to calculate air volume of a fan using pressure?

• Raphael Gonzalez
In summary, to calculate air volume in cubic feet per minute through a fan, you need information about the pressure drop and the fan diameter. However, this is not enough information to determine the airflow as there is also a pressure jump and changes in air velocity that need to be taken into account. Some NASA articles suggest using the propeller equation to solve for the velocity and volume flow at the fan, but these calculations may be idealized.
Raphael Gonzalez
How can you calculate air volume in cubic feet per minute through a fan when the only data available is pressure drop and fan diameter?

For example, How many cubic feet per minute of air is a fan blowing if it has a diameter of 20" and a pressure drop of -50 pascals?

Welcome to PF!

That's pressure rise you mean, but sorry, that isn't enough information to determine the airflow.

Generally there's a pressure jump (with little change in speed) of the affected air as it passes through the plane of the rotating fan. There are related NASA articles about propellers which should allow you to solve for velocity at the fan (and therefore volume flow at the fan), ... , some what idealized. Assume that V0 is zero, and that density is constant.

http://www.grc.nasa.gov/WWW/K-12/airplane/propanl.html

http://www.grc.nasa.gov/WWW/K-12/airplane/propth.html

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1. How do you determine the pressure of a fan?

The pressure of a fan can be determined by measuring the air velocity at the fan outlet and using a pressure gauge to calculate the pressure.

2. What is the formula for calculating air volume of a fan using pressure?

The formula for calculating air volume of a fan using pressure is: V = (Q x 60) / P, where V is air volume in cubic feet per minute (CFM), Q is air flow rate in cubic meters per hour (m3/h), and P is pressure in inches of water gauge (in. wg).

3. Can the air volume and pressure of a fan change over time?

Yes, the air volume and pressure of a fan can change over time due to factors such as changes in air temperature, changes in fan speed, and changes in the environment.

4. How does the size of a fan affect its air volume and pressure?

The size of a fan can affect its air volume and pressure as larger fans typically have a higher air flow rate and can generate higher pressures, while smaller fans may have a lower air flow rate and generate lower pressures. However, the design and efficiency of the fan also play a significant role in determining its air volume and pressure.

5. Are there any other factors to consider when calculating air volume of a fan using pressure?

In addition to air flow rate and pressure, other factors to consider when calculating air volume of a fan include the fan's efficiency, the type of fan (e.g. centrifugal, axial), and the specific application and environment in which the fan will be used.

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