"Mike Harrison" wrote in message
...
On 8 Jan 2005 06:15:54 -0800, (N. Thornton) wrote:

I imagine one could make LN2 @home with vortex tubes. As air spins
through the tube it separates into hot and cold streams. Dump the hot
and put the cold through another vortex tube, etc.

Air must be dried for these experiments, otherwise ice will quickly
clog the cooling kit.

I suspect there is a fly somewhere in the ointment with that idea, as I'm
sure someone would be
making & selling an LN2 generator based on vortex tubes if it was
practical. Current LN2 generators
that I've seen are somewhat more complex...

Maybe it's just an issue of efficiency - I suspect such a system would
need a lot of air.
The graph here http://www.visi.com/~darus/hilsch/ suggests about one third
of the air comes out
cold, so each stage would need to have 3 times the airflow of the next.

I'm also wondering how easy these are to make - commercial ones seem quite
expensive if all they are
are is essentially a cast/machined chamber. Some info I saw says that
rotational speeds of the air
were of the order of 1000000RPM,

That's alright then, just up the voltage on one of those new Dysons ;-)