[Beowulf] oil immersion cooled blades

[Eugen Leitl]

On Wed, Mar 14, 2012 at 08:12:47PM -0700, Lux, Jim (337C) wrote:

> The Cray-2 used Fluorinert(tm) FC-74 as the coolant, which is very nice to
> work with, although expensive.

I've worked with a few 3M fluorinerts for blood substitutes (nothing
kills quite like liberated fluoride during sonickating) and for cooling/partial 
liquid ventilation purposes. Heavy stuff, twice the density of water.
Seems to do havoc to your immune system at long-term exposures.

> It doesn't wet things very well, so when you pull something out of the
> bath, it doesn't bring much fluid with it. The Cray used it as a heat
> transfer medium to water coolant.  I think they had a way to drain it into
> a tank quickly for servicing.
> 
> 
>  It can be used for ebullient (boiling) cooling by picking the right vapor
> pressure/BP grade (the Cray didn't use this). Ebullient cooling is quite

The Cray X1 used evaporative spray cooling at least
http://www.cse.ohio-state.edu/~panda/875/class_slides/cray-jaguar.pdf

> efficient at moving the heat away because it's a phase change, and the
> bubbling causes good circulation, but it does require careful design so
> you don't get film boiling/Leidenfrost effect (the phenomenon that
> protects your feet when walking across burning coals barefoot)

There's a K/Na eutectic which is cheap (unlike Ga eutectics) and 
is liquid at RT. Extreme fire hazard if you'll get a leak in air, though.