[Beowulf] Re: Cooler room or cooler servers?

[David Mathog]

On Mon, 11 Apr 2005 joelja at darkwing.uoregon.edu wrote:

> On Mon, 11 Apr 2005 award at andorra.ad wrote:
> 
> > Some time ago, I was thinking of using an inert liquid such as 3M's
> > Fluorinert  for refrigeration.

> 
> also you'd be helping keep the ozone hole large for the next 50 years...
> 

According to the product information:

Fluorinert liquid FC-40 has zero ozone depletion potential. The
material is exempt from the U.S. EPA and most State definitions
of a volatile organic compound (VOC), and does not contribute to
ground-level smog formation.

Fluorinert liquid FC-40, a perfluorocarbon (PFC), has a high global
warming potential and a long atmospheric lifetime. As such, it
should be carefully managed so as to minimize emissions.

3M recommends that users of FC-40 liquid further limit emissions by
employing good conservation practices, and by implementing
recovery, recycling and/or proper disposal procedures. 3M offers
a program for used fluid return.

The stuff is nonreactive but that doesn't mean it's completely
safe.  I recall studies of freon type liquids as a liquid
breathing medium for mice.  Once it got into
their bodies it destroyed their livers.  The mechanism was
interesting - since their bodies had absolutely no way to
eliminate this teflon like material it just piled up inside the
liver cells.  If memory serves massive cirrhosis was the result.
Here'a another study with a similar liquid:

http://www.chestjournal.org/cgi/content/full/118/5/1436

In this one they let dogs breathe various fluids for a while and
then followed them for years.  The most relevant part, to my mind, was:

...However, in the whole lungs of four dogs killed at 5 years,
vacuolated macrophages were still present in all lobes, but in greatly
reduced numbers compared with earlier years. Concurrent analysis of the
lung samples for Caroxin-F by gas chromatography revealed an exponential
decrease in residual values over the years from 0.31 mg/100 g of tissue
at 6 months, to 0.16 mg/100 g at 1 year, and approximately 0.11 mg/100 g
at 5 years. Importantly, in no case was there any evidence of fibrosis
or other permanent damage associated even with the heaviest macrophage
burden. By chance, the two dogs that survived 10 years, although equally
exposed to Caroxin-F and having the same postventilatory effects on
pulmonary function and blood gas values as the others in their group,
appeared to have the lightest fluorocarbon load as judged by the numbers
of macrophages in their earlier biopsy specimens.

Translation - the body is not good at clearing this sort of material.
Caroxin-F was the best material these researchers found and
simpler Freon like substances should have much longer half lives
in the body.  In this context it might be a good safety measure
to use a fluid for cooling computers which has a boiling point
sigificantly below human body temperature.  That should greatly
reduce retention of the material, since these tend not to be
very soluble in water.

Regards,

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