[Beowulf] Innovative liquid cooling

Mark Hahn hahn at mcmaster.ca
Thu Feb 28 18:12:26 PST 2013


> Actually, since the thermal conductivity of the liquid is so much better
>than air, you probably don't need finned heat sinks. Heat transfer rates is

well, you don't need AS MUCH surface area and/or can tolerate lower flow.
even given better conductivity, and acknowledging greater heat capacity 
as well, can you really just cool one wall of a tank and expect everything
immersed in it to be well-cooled?

actually, does anyone have numbers on this 3M fluid?

if the following table is to be believed, 1000x would be quite impressive:

http://upload.wikimedia.org/wikipedia/commons/1/1e/Thermal_conductivity.svg

(if I'm reading it right, it shows water about 30x higher W/(m*K) vs air.


> Boiling at these temperatures would require a relatively volatile liquid,
>which would probably flammable (explosive), or bad for you in other ways

pages around here:
http://solutions.3m.com/wps/portal/3M/en_US/3MNovec/Home/Applications/HeatTransfer/Semiconductor/

seem not to be too alarmed about boiling.  I'm guessing we might be talking
about the novec 7300, which claims to have "low toxicity" as well as 
being nonflammable.

I was thinking of boiling just because such a cycle moves a lot of heat
and has some natural engineering advantages (bubbles, as you mention).
even there, you'd obviously want to design your system to keep components
out of the CPU's heat plume...

I guess my main point is that you can't take a current air design,
remove the fans and have an efficiently-operating fluid-cooled design.


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