calculating cfm

[JoeSenihcam]

Does anyone have a formula for calculating the cfm of air using the line diameter and the air pressure.
Any help would be appreciated.
Joe

 

[smckennz]

Hey Joe
thats a sticky question.
Could take a while to explain properly.

Problem is that its not the pressure that moves the air.
Are you in a postition to explain what you are trying to do in a little more detail?

Would make the answers a lot more useful to you.

Cheers

Steve

 

[ChrisConley]

There is a way to calculate flow if you know pressure drop through a known obstruction. An orifice plate with a known Cv will allow you to calculate flow if you have a way to measure pressure up and downstream.

 

[25362]

Air is a compressible fluid. Thus you need pressure (given) and temperature (missing) to determine its density.
Besides, CFM is a rate, meaning a time factor is included. If you have a bulk average linear velocity (also a rate) you'd be able to estimate the CFM.

Otherwise one should proceed by installing a Pitot tube, or any known obstruction measuring the friction drop, as ChrisConley suggests, which, in effect, is a step meant to estimate the bulk linear subsonic velocity of the fluid, or by the introduction of a tracer and its detection at two fixed points.