[Beowulf] Innovative liquid cooling
hahn at mcmaster.ca
Thu Feb 28 20:16:30 PST 2013
> Though I'm not certain, it seems reasonable to think that the key
> temperature is the junction temperature, which is much higher than
> the air temperature. With more efficient cooling, that is,
intel/amd spec chips as "Tcase", which makes sense, since they don't
really wanting you removing the heat-spreader.
it's all about delta-T and thermal resistance. immersion means lower TR,
so for a given max Tcase (say, 70C), your ultimate heatsink (atmosphere)
can run warmer. in the video, they were dissipating into the room, which
probably means about 50C.
for an air-cooled system, you need intake temperatures of 15-20C to
stay under Tcase at normal fan speeds. hot side will be around 35C,
so it's up to your CRAC to get that back to 15C.
warm-water systems are also based on the idea of reducing TR, so that
the heat rejection side can run closer to Tcase. after all, if your
cluster produces a megawatt of 60C water, that's pretty useful...
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