Compressor Equation

  • #1
Please give me the equation with a link if possible for determining power for a compressor. I know volume x pressure differential / efficiency but I think the gas being compressed also is a factor. Thank you.
 

Answers and Replies

  • #2
FredGarvin
Science Advisor
5,066
9
From my old thermo notes, a non-isentropic compressor has a power of:

[tex]\dot{W} = \frac{\dot{m}C_pT_1}{\eta_c} \left[\left(\frac{P_2}{P_1}\right)^{(\frac{\gamma-1}{\gamma})}-1\right][/tex]

You can see the same equation here:
http://www.grc.nasa.gov/WWW/K-12/airplane/compth.html
 
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  • #3
231
1
The site seems to be down at the moment but there are online calculators for recips and centrifs at www.processassociates.com

To to process tools section.
 
  • #4
Fred, from your equation a vacuum pump that has a 1bar/.01bar pressure ratio needs more power than a compressor that has a ratio of 10bar/1bar? Is m the molecular weight or the volume?
 
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  • #5
FredGarvin
Science Advisor
5,066
9
m is mass flow rate.

I'll have to look around a bit, but a vacuum pump most likely will not be applicable here. I'm not sure, I don't deal with them.
 
  • #6
1
0
Hello, I'm working on a model of a fan and I have the characteristic curves Flow/impelled power and flow/total pressure.

I also have the relation of adiabatic compression you have written but it concerns the Head (in meters) and not the mass flowrate. Therefore, my question is : how do you get the outlet pressure of a fan knowing the characteristic curves and the formula with the head ?

More clearly that possible to convert the Head (m) into a differential pressure (Pout-Pin) or even the outlet Pressure of the fan (Pout) ?

Thank you for any idea.
 
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  • #7
1
0
Hi, somebody knows this formula???

HP= Q * 63 * Ln(Pd/Ps)

Is a rare formula that are been used in a pipeline gas.

Thanks.

Felipe

PD: Sorry if I make a mistake in the english, I speak spanish.
 
  • #8
738
0
Fred, from your equation a vacuum pump that has a 1bar/.01bar pressure ratio needs more power than a compressor that has a ratio of 10bar/1bar? Is m the molecular weight or the volume?
[tex]\dot{m}[/tex] is the mass flow rate, & is equal to [tex]\rho[/tex][tex]\dot{V}[/tex]

ie. work required also depends upon the inlet density.
 

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