I recall something about liquid (something, could be nitrogen, or perhaps
even mercury) that was chilled; PC Boards were then submersed in the
liquid to keep cool.Maybe on Crays?
Flourinert. very odd Lime green transparent liquid. in our cray, it was
in a tank with a toilet float to keep the fluid topped up.
the pipe bend radii for the cray fluid was *more* than the IBM waterpipes.
our floor was raised to meet IBM. we had to sweat blood to get the cray in
because of a 10-12mil difference. 
the 400hz voltage genset was deeply scary. circuit breakers that smoke
when they blow, fuzes like those in 'bil(l) the galactic hero'
-George