[Beowulf] cooling question: cfm per rack?

[Robert G. Brown]

> if your pressure is reasonably even, the same tiles should flow the 
> same CFM.  I'd LOVE to find some way to measure airflow, since I'd 
> actually consider doing things like adding patches of duct tape to 
> the underside of too-high-flow tiles.  I suppose that the empiricist
> approach is just to sample all your system temperatures, and if some 
> are too high, reduce the airflow to racks which are "too cool".

Relative airflow can probably be measured with a kid's toy -- one of the
little pinwheels -- and counting revolutions with a stopwatch.
Normalizing that to absolute airflow in CFM is a bit tricky (since the
result depends to some extent on the resistance imposed by the measuring
apparatus) but somebody out there may have designed a version of this
with a real fan and magnets set so that the counting is done
electronically.  In fact, I could build something to do this out of OTC
parts if I had any way to normalize the count.

   rgb

-- 
Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at phy.duke.edu