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Compressor Equation

by spiraltooth
Tags: compressor, equation
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spiraltooth
#1
Apr7-07, 02:54 PM
P: 2
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.
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FredGarvin
#2
Apr7-07, 03:06 PM
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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
quark
#3
Apr9-07, 11:07 PM
P: 230
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.

spiraltooth
#4
Apr11-07, 11:03 PM
P: 2
Compressor Equation

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?
FredGarvin
#5
Apr12-07, 06:08 AM
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P: 5,095
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.
powerpsy
#6
Nov1-07, 06:44 AM
P: 1
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.
fmiranda
#7
Aug12-09, 11:30 AM
P: 1
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.
ank_gl
#8
Aug13-09, 09:15 AM
P: 733
Quote Quote by spiraltooth View Post
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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