/me dons ex-chemical-engineer hat :)
On Sun, 21 Apr 2002, Mike Wroughton wrote:
> How cold do you have to have nitrogen to stay liquid?
Very - it liquefies (or boils, conversely) at -195.8C (about 77 Kelvin)
under atmospheric pressure so there's a challenge there to keep it cool.
> And could you pressurise it to keep it liquid instead?
Yep. But that requires pretty high pressures and some serious cooling
also. The liquefaction pressure varies according to temperature, so the
colder it is, the lower the pressure needed. And there's the tricky bit -
the more you squeeze, the hotter it gets...
Liquid N2 is pretty cheap, so if it's just spot cooling you're after for a
short period you can just let it boil off to atmosphere as the more
serious benchmarking overclockers do. Otherwise you need to keep it in a
closed refrigerant loop, in which case you'd be better off in the first
place using a commercial refrigerant instead - they need much less in the
way of pressure to remain liquid, and have better heat capacity
properties.
To be perfectly honest, you'll probably have better performance if you buy
a small freezer and put your system inside it, or simply move a lot more
air over whatever heatsink you have. Consider a ducted system, where the
normal system fan is removed and you have a much larger one with a duct
which sits over the CPU heatsink.
Alternatively, I give you:
http://cp-geek.servepics.com/waterwww/
or
http://www.muropaketti.com/artikkelit/cpu/northwood2200/ln2/index.phtml
And remember, liquid N2 can seriously damage your (or your pooter's)
health :)
G
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