Heat pipes?

[Bob Drzyzgula]

I suppose that there's always mineral oil...

http://www.drffreeze.com/

That site hasn't been updated in years, but it's
kind of an interesting idea.

Nonetheless, I think that there's one aspect to all
this that may be missing from this discussion. The
big problem, as I see it, is not how to get the heat
out of the enclosure, but rather how to get it out
of the building. 

Suppose that you had a rack filled with 40 1U cluster
nodes, and that each node burned juice at about 100W;
In this case, your rack will be burning up about 4000W,
or around 13,600 BTU/hr. One ton of chiller capacity
can remove 12,000 BTU/hr, so just for that rack you'll
need over a ton of air conditioning. If you *don't* have
more than a spare ton of AC, the temperature in your
rack is going to go up steadily. It doesn't matter
how good your heat sink, heat pipe or whatever, is --
if the heat generated by your cluster isn't removed
from the data center, no amount of forced airflow through
the rack will do any good. 

I think that most 1U cases will do OK as long as
the ambient temperature stays within tolerable levels.
But feed them hot air to cool with and you have
problems. Somewhere I read -- perhaps it was on this
list? -- that some entrepreneurs were proposing to
set up a massive web hosting facility on the North
Slope of Alaska, largely to reduce cooling costs...

--Bob