very low temperature compressor

[nrgy]

I have searched the web to no avail to locate a small
(1 to 2 hp) compressor for compressing nitrogen at  -150 C(-240F) with a compression ratio of about 4.
I would appreciate any information on compressor design limitations at very low temperatures.

Thanks for your help

 

[zdas04]

nrgy,
"Compression ratio of about 4" isn't enough information to help. If you want to go from 0.2 bar(a)to 0.8 bar(a) you'll be looking at a different machine then if you want to go from 1 bar(a) to 4 bar(a) or 100 bar(a) to 400 bar(a), etc.

For any compression application you need to know: (1) what is your target suction and discharte pressure and temperature (the heat of compression for 4 ratios would raise the temperature to -92C, is that too warm?); (2) how tolerent are your downstream processes to oil contamination?; and (3) what is your desired compression volume (different required capacities point you toward different technologies)? Many manufacturers make cryo compressors in various technologies.

At -150C you are only 45C away from the boiling point, it might be less expensive for a small volume to "compress it" by cooling it to a liquid and pumping it.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

The harder I work, the luckier I seem

 

[nrgy]

Thanks muleshoe.

The system is for a liqN2 powered engine with vaporization of the liqN2 by a secondary gas(N2 or air).
The compressor is to pressurize the cooled secondary gas from 1 atm. to 4 atm., thus economizing the liqN2 and using minimal compression work.

Hope this makes sense

 

[zdas04]

Not really, please see the three questions I asked above.

David

 

[nrgy]

David,

1. compression is from 1 atm. to 4 atm, Outlet of -92 C is acceptable.

2. oil should be tolerable downstream but probably not good to discharge to atmosphere.

3. not sure what you mean by compression volume. Volume flow is about 6 cfm at outlet conditions.

Thanks for your help,
Steve Kaufman