Duct Fan Flow Calculation

It's easier to use a Pitot Tube and a Manometer!

You could estimate it if you know

- motor actual output power (measure current and voltage and assume efficiency if you don't know)

- allow for efficiency of drive arrangement, ~ 100% for coupling, less if it's V-belt, to get fan input power.

- pressure rise across the fan. Measure static pressure each side preferably in same diameter duct. If different dias need to take account of velocity pressure.

- fan efficiency from manufacturer's data, or if you don't have this, make an assumption.

Cheers.......Codey

Good day,

Air flow through a blower is readily determined using fan laws and fan performance curves. If you measure fan RPM and static pressure drop across the fan you can find the flowrate of air from the fan curve. It is good practice to confirm your results by measuring the motor current and finding horsepower from the motor performance curve readily available from the manufacturer. It should be in reasonable agreement with the pressure readings.

This New York Blower website has excellent literature on how to determine the flow.

Good luck,

http://www.nyb.com/Catalog/Bulletins/651.pdf

Thanks guys,

All your inputs are very helpful, I thank you for them.

The problem is that I cannot find any mauals or information from manufacturer on the Fan or the motor. All I have is the Motor Data Sheet. no performance curves what so ever. I guess I will have to measure the pressure accross the fan and try to work something out. If any more Ideas please dont hesitate to share. Thanks again :)