gas compressor temp rise 1

[mielke]

I have been using the following equation for determining rise in temperature for a gas compressor...

To=TiRc^[(k-1)/k]

where Rc is the ratio of the outlet to inlet compressor pressure, k is ratio of spec heats, and the T's are the temp differences.

I just stumble across this online and want to know if anyone uses this to determine temp rise for gas in a compressor or if they can suggest a better equation


Thanks

 

[zdas04]

That equation works very well for adiabatic compression (the adiabatic assumption is almost always close enough). Make sure that all pressures and temperatures are in absolute terms.

The "T's" are not temperature differences. The are the measured temperature at the inlet plenum and the measured temperature at the outlet plenum.

David

 

[mielke]

so just to get this straight if I have a 114.7psia compressor sucking from ambient of 100F and 14.7psia my discharg air temp will be...

To = (100+460)x(114.7/14.7)^[(1.4-1)/1.4]
To = 547 F

seems a little hi just wanted to get some verifaction from people that see this more often than me.

 

[zdas04]

You are doing 7.8 ratios. Doing it all at once would be far too hot for any commercial recip (and the load on the connecting rod would be through the roof). The max temp anywhere on a compressor is usually limited to under 300F.

Generally a recip is limited to less than 4.5 ratios per stage with inter-stage cooling. This means that you go from 14.7 psia to 50 psia (temp is 400F which your compressor can't handle, so you back off). Let's try that again with a 2.8 ratio limitation--first stage discharge is 291F at 37 psia. If your interstage cooler has a 20F approach to ambient, then the second stage suction is 120F and 34 psia. That makes the second stage discharge (at 2.5 ratios) 294F at 92 psia which doesn't quite make your target. Now if you lower your inlet temp to 90F, you can take the first stage to 3 ratios (44 psia). Now the second stage can go 2.6 ratios in the second stage and get to your target without exceeding a temperature limit.

This kind of game playing is often called "engineering".

David