[Beowulf] Rear-door heat exchangers and condensation

Nifty Tom Mitchell niftyompi at niftyegg.com
Wed Dec 10 15:08:12 EST 2008


On Wed, Dec 10, 2008 at 10:21:42AM +0100, Kilian CAVALOTTI wrote:
> 
> Hi Gerry,
> 
> On Tuesday 09 December 2008 16:26:29 Gerry Creager wrote:
> > Our p575 has cool doors.  Our campus chill water temp is spec'd at 42F
> > but ranges up as high as 48F.  We are seeing no condensation I'm aware
> > of, but I'll ask the operations guys.
> 
> Thanks, that's helpful. I was afraid that a low temp for chilled water would 
> generate condensation on the pipes, or even on the doors themselves.
> 

Watch dew point numbers in the room.
Dew point is dominantly a function of humidity...
  http://en.wikipedia.org/wiki/Dew_point

If the dew point is higher than the chilled water temp condensation is
possible if the heat exchanger surface cools that much.  Condensation on
normal cold water pipes and chillers in the large and small construction
like home or office is common so the correct insulation materials are
easy to find and install.

Many frost free home refrigerators solve this problem by running the
heated exhaust air over the catch pan so any frost/ condensation is promptly
evaporated.  With clever airflow management drains may not be needed but
water rots wood, breeds bacteria and attracts bugs and may be problematic.
The bacteria issue is important.... see  Legionella pneumophila.

Right now the outside air dew point in Bryan, Texas is about 19F and
historically gets as high as 69F in December.  So yes condensation from
42F cooling pipes is possible and should be part of the management/
monitoring process.  I suspect that the campus AC manages the dew point
to the high end of a comfort range  that might be about 50 - 54°F in the
US keeping things all OK.  i.e. If the building AC manages humidity you
may not have to if they have the capacity to control it at the building
air inlets.

Of course the weather in France is not the same as Texas... looks nice ;-)
something like.
 52 °F  / 11 °C Light Rain Humidity: 82% Dew Point:  46 °F  / 8 °C 


-- 
	T o m  M i t c h e l l 
	Found me a new hat, now what?


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