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Compound Freezer too cold? Answered

I have been looking into making liquid nitrogen and I have found one DIY method.  It uses a small cryocooler.  I wondered if it would be possible to use multiple stages of coolers like those used in a freezer.  So basically you take all the stuff off of a two or three freezers, or more, and you use them in a series to get progressively colder.  The first compresses the coolant which is then decompressed cooling the hot side of the next step down to freezing temperatures.  Is this possible with your everyday freon which is already in these systems, or do you need to get a better coolant, and will this even get cold enough to liquify nitrogen? 

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steveastrouk (author)2013-03-02

Two stage refrigeration systems are not uncommon - some commercial refrigerators will use them, beyond that, the thermodynamics of heat engines like that, and the gases that can be used limits the useful minimum to around -70C. regenerative Joule-Thomson cooling is the method to use.

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jj.inc (author)steveastrouk2013-03-02

Thank you, after some more research I got this Joule-Thomson thing figured out. I believe I will use a Hampson-Linde system. I know from my reading that this effect doesn't work on helium, but could it be used to liquefy helium, because who doesn't wan't to take advantage of the chance to build a superconducting magnet with a nail and wire if they can.

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steveastrouk (author)jj.inc2013-03-02

If you have niobium wire, you're all set. I don't think copper exhibits superconductivity

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frollard (author)2013-03-01

I can't say for certain, but I'm pretty confident 'boring old' freon will become solid at the cryogenic temperatures needed to make LN2...but don't take that as gospel, do the research.

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