[Beowulf] A/C to water cooling, considering the transition

[David Mathog]

Just for the sake of argument, let's say one has today
6 x 10kW racks cooled via an A/C that runs off a chilled
water line.  

Two years from now water cooled racks become widely available.

How would the transition from A/C to water cooling be handled?

Could the same cooled water line (2" or whatever it is) be
split and partially fed into the racks, partially into the
A/C?  Naively this would seem like it might be an option
because the heat that would have gone out through the A/C 
for the air cooled rack would instead go directly into the
chilled water for the water cooled rack.

Would it make sense in designing new rooms to use a larger
diameter chilled water line now?

Should a capped T or two be put in the line to facilitate this
transition?  (If nothing else, it would make adding more A/C
floor units easier.)

Or is chilled water  too cold for direct use in cooling
computer equipment?  (For nstance, causing condensation
problems.)

Regards,

David Mathog
mathog at caltech.edu
Manager, Sequence Analysis Facility, Biology Division, Caltech