compressor CFM 1

[ajs83]

I used a sonic nozzle to measure the flow rate of a compressor. The nozzle was located at the discharge of the compressor. I have found my flow rate in CFM with respect to the pressure drop and temperature at the nozzle. To my understanding this is CFM (not ICFM, ACFM, or SCFM). I want to convert this back to inlet conditions. Is there an equation to convert CFM to ICFM.

 

[BigInch]

Supposedly you got the ACFM at your ambient pressure and temperature conditions. Assume Z apx = 1.0, convert to SCFM by multiplying your Qacfm x (your standard pressure)/(your actual atmospheric pressure absolute psi) x (459+ your Std Temp F)/ (459+ your actual temp F)

http://virtualpipeline.spaces.msn.com

 

[sailoday28]

From gas tables or compressibility charts, obtain Z from the known pressure and temperature. pdv/dt=ZRdm/dt where dv/dt is for volumetric flow. With value dm/dt use procedure of BigInch at standard conditions where Z=1.

 

[sailoday28]

OOPs! pdv/dt=ZRdm/dt should be
pdv/dt=ZRTdm/dt

 

[mbeychok]

To convert a gas volume from one set of temperature and pressure to another set of temperature and pressure, the combined gas law applies:

V₂/V₁ = (Z₂/Z₁)(P₁/P₂)(T₂/T₁)

T = temperature
P = pressure
V = volume
Z = compressibility factor

It doesn't matter in the slightest what you call each of the two volumes ... CFM, ICFM, ACFM, or SCFM. The only thing that matters is the pressure and temperature of each of the two volumes.

Milton Beychok
(Visit me at www.air-dispersion.com)
.

 

[Latexman]

I agree mbeychok, the acronymns and words lead to confusion. A volumrtic flow rate should be followed by something like @ 60 F and 14.7 psia. That nails it! A star for you!

Good luck,
Latexman

 

[sailoday28]

All of the above is true, ---on the basis that the mass flow rate is conserved in states 1 and 2.

 

[katmar]

I have written a free utility program that does this conversion, but first make sure that you use the reference given by Milton to understand the process. Also take heed of Sailoday's caveat and do not use the program in the proximity of black holes.

Click the link in my signature below and follow the links to the freeware program Uconeer - it does general engineering unit conversions in addition to the gas flow conversions.

Harvey


Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[sailoday28]

katmar (Chemical
My real point is that we are not using an equation of state of PV=MRT but P dVdt=RT dMdt
For example in unsteady/transient flow, relating to scfm would be difficult and confusing?

 

[ajs83]

I am not sure that I can apply the ideal gas law in high temperature and pressure conditions. I will be around 1000 psi.

 

[sailoday28]

For the given gas, you should be able to obtain the compressibility factor.

What is the gas?