Fan Flowrate from Pressure Readings

[BillKapri]

Hi, would it be possible to get a rough estimate for a fans flowrate by taking pressure measurements and using the fan curve. So for example, something like measuring the pressure differential across the pump to get the TDH and cross comparing it to the pump curve.

How many and where would I need to take the pressure measurements?

This is for an ID fan with a 'suction pressure' fan curve. The fan is pulling air through a series of ducts and equipment.

Thank you very much in advance.

 

[LittleInch]

Yes.

Take the pressure more than 5D from the fan.

Fan dp is usually very small so accuracy is important.

Also depends on how steep your curve is.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[pierreick]

Hi,
Why don't you use a simple pitot tube to measure the velocity and get the flow rate?
Pierre

 

[BillKapri]

Take the pressure more than 5D from the fan.

So to reiterate is this a pressure differential? So inlet and outlet, or just the auction side?

What confuses me a bit is the physical meaning of 'suction pressure' on the fan curve, which I guess is actually my question.

Thanks for your answer

 

[LittleInch]

Yes differential pressure. Unless the exit is basically atmospheric. Then you only need to know suction pressure relative to atmospheric pressure.

What it means is that it is designed to be atmospheric pressure on the exit, I.e very small or no exit ducting, but it is basically an extraction fan.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[georgeverghese]

Abstract from Perry in the chapter on fluid transport, subsection on fan performance:

"When the density of air or gas varies, horsepower and pressure vary
directly as the density, speed and capacity being constant."

So dp developed varies as suction density varies.