[Beowulf] Innovative liquid cooling

[Mark Hahn]

> consumption from 41 kW (electricity, probably same amount again for cooling)

I really doubt it.  there is something profoundly wrong if an
  HPC-type datacenter, with completely conventional servers, air/DX cooling 
runs at a PUE of more than about 1.3-1.4.

immersion cooling sounds appealingly unconventional, but if you think
about the heatflow, you've still got to move it around.  you still need
a heatsink on the CPU with fins, some way to move the fluid past these
fins and get them to the secondary heat exchanger.  as with airflow
management in a conventional DC, surely one has to ensure that cool 
fluid gets to the CPU fins and heated fluid finds its way to the 
rejection exchanger.  surely convection wouldn't be good enough without
some serious re-engineering.  or do these systems rely on boiling?

so I wonder what the effective thermal resistance is for such a 
fluid system (assuming some fishtank-like pumping).  risk-wise,
I'm pretty sure I'd be more comfortable with a heatpipe inside 
the chassis mating to a coldplate/exchanger built into the rack
running the water loop.