yeah, I know it's not really feasible. But it's done in the production of LN2, theoretically, what would it take to compress and condense nitrogen, as in a single stage (albeit gIANT compresor) system??
Educate me ;)
C
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yeah, I know it's not really feasible. But it's done in the production of LN2, theoretically, what would it take to compress and condense nitrogen, as in a single stage (albeit gIANT compresor) system??
Educate me ;)
C
You'd be better off using Carbon Dioxide...
Think the pressure requirement will be to high...
But... May the force be with you :P
Ok, I dont know if this really answers your question because I didnt 100% understood your question, but anyways....
Nitrogen boiling point is VERY low, around -195C IIRC, but to condense it you would need around a -170C HX. So that would be like a sixth stage refrigerant. To do a refrigeration system the refrigerant HAS to condense. Plus I dont know how the LN2 capacity is, so it would be possible that the sixth stage compressor would be like a 3HP.
And last, I dont even know if it CAN be used as a refrigerant because of its un-ability to easily compress....
Although, I am not a Pro in this subject....
Bleh, you could use a first stage compressor. You'd just need it to be.... well BIG. In fact, you'd have to get specicial wiring into the house, and your power company would surcharge you every time you start it up. :fart:
I understand what you mean, but I was simply curious, because if I'm NOT mistaken, a LN2 generator uses a gi-freekin-gantic compressor to compress/generate LN2. ?? It's just curiousity, not saying I'm gonna build one in my living room, lol...Quote:
Originally Posted by skate2snow
Yeah, like I said. :p
Ideally, it would use a reciprocating compressor. A pretty big one.
I am not denying your Idea or nothing, I just tried to get the facts that I knew on the table:).
A compressor able to compress it would be so big. Like if it was a "normal" gas, but with a low capacity, just there it COULD need a 3HP.... But now a gas hard to compress such as that! I dont know if they manufacture some...lol
Well assuming nitrogen's critical temperature is somewhere near it's evaporating point @ atmospheric pressure, I'd assume it's be a 4th stage gas most likely.
A number of companies make units that aren't super large and use in the 12KW to 16KW range. If you're interesting in learning some about how it's done commercially to get the gist of it and a starting point Charlie, check out Stirling's site here
ps. Their "owner's manuals" have some pretty detailed info in em ;)
very COOL site, hehehe....Quote:
Originally Posted by EMC2
something like this:
Most LN2 generators work on an open loop basis, I think it works like this:
What you have showen is probably something like a stirling cycle, that wouldn't be able to produce any great volume of LN2 and would have little capacity
4th stage refrigerant condenses around -145C....Quote:
Originally Posted by bh2k
It dosnt matter how big your compressor is you will not condese it unless you get its temperature below -145C.
Regards
John.
Yes, but condensing it is not the only problem.... One of the main problem is the compression of the gas that WILL need a big compressor...
Not quite! Lets say you get the gas to -143C you will never condense the gas no matter how big a compressor you find. Compressing nitrogen isnt a problem a 1/10 hp compressor will compress nitrogen. What we need to do is compress it to the pressures required at a given condensor/hx temperature to condense it.
Yes, but thats in direct relation, aint it? We dont want to get it at 1000PSI! At around 200PSI (the "safe" pressure we are normally working with) would need a big compressor....
And I never said condensing it was a problem;)
hp does not relate to preasure that way, a 1/10 hp motor can pump 2000 psi as well as a 10 hp motor, the larger the motor the larger cylinder displacment it can handle.thus pumping to pressure faster.
Yes Yes..... Is my english that bad? :p:....
I didnt say a 10HP would pump 2000PSI more...
The point I'm trying to make is that at any temperature above Nitrogen's critical tamperature of around -145C(Ishould really look that up) it dosnt matter what compressor you use, even at the centre of a black hole you will not be able to create liquid Nitrogen.
And so back to Charlies original question:
"yeah, I know it's not really feasible. But it's done in the production of LN2, theoretically, what would it take to compress and condense nitrogen, as in a single stage (albeit gIANT compresor) system??
Educate me "
Its Impossible Charlie! It can however been done with a single compressor autocascade system.
Regards
John.
Just about spot on there pythagoras, its -146.96ºC :clap:
me confused... with headache.Quote:
Originally Posted by pythagoras
Sometimes they use the 'air cycle' for nitrogen liquefaction.
where normal refrigeration cycles are analagous to the rankine (steam turbine) cycle running in reverse, the air cycle is like the brayton (gas turbine) cycle in reverse. The air cycle can be used to span quite large temperature differences without the need for high compression. The gas isnt limited to evaporating or condensing at certain temps for given pressures. this allows a counterflow heat exchanger to be placed so that the refrigerator will 'draw its own temperature down'. you all probably have no idea what im talking about, I suck at explaining things. look on google, that may clear things up.
What the Pythy one is talking about is the critical point, which is another combination of pressure and temperature of a phase diagram (just like the "normal" boiling and melting points of a substance... "normal" being the temp at 1 atmosphere). Most materials have one. It is a temperature at or above which it becomes physically impossible to cause liquification. For nitrogen it's the aforementioned -146.96C. At any temperature above that, nitrogen will not change phase to a liquid regardless of pressure - not at any pressure, add all the 0's you want. So to generate liquid nitrogen, the temp must be below -146.96C. You need ~300 psi at around -160C to liquify nitrogen, less than -196C to liquify it at atmospheric pressure (14.69595 psi) - which is just below it's boiling point of -195.80C at 1 atmosphere.Quote:
Originally Posted by charlie
There is also a triple point - where a substance can exist in all 3 phases (solid, liquid, gas) at the same time. For nitrogen it's -210 C and 1.807602 psi.
The commercial LN2 generators I pointed you to before use a stirling cycle. Here's a linky that shows in general how it works. This is the section of the overall generator that you put the thumbnail up for.
Peace :toast:
http://lnglicensing.conocophillips.c...tercentury.pdf
You might find that pdf an interesting read if you haven't seen it in that thread i posted the ln2 forum. Basically, phillips used a three stage cascade (R290, ethylene, methane) to liquify air and then remove the n2 by fractional distillation.
OHHHHHHHHHH!!!!!! Now I understand!! Hmmm...300psi AND -160C...Quote:
Originally Posted by EMC2
C