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Subject: Heat pipes

Heat pipes

From: Jerry Shiner <70252.763>
Date: Friday, November 25, 1994
Just a note on the use of heat pipes for removing humidity.

One problem when running air conditioners is matching the cooling power
of the unit to the changing needs of the area to be cooled and
dehumidified.  From what I understand, the cooling power of an air
conditioner is "fixed", and although fan speed, etc, can be changed, the
compressor (the heart of the cooling section) must cycle off when the
appropriate temperature has been reached.

An air conditioner dehumidifies only when the compressor is running and
the coils are cold, therefore, unless the unit is operating at full
capacity (removing as much heat as it can) it will not be removing
moisture at all times. It follows that if the air is humid, but not
warm, the air conditioner will not be very useful as a dehumidifier.

To increase the dehumidifying efficiency of our cooling systems in fur
storage vaults, we sometimes added heating units (baseboard heaters or
radiators) in the vaults.  This was done just to increase the heat load
on the cooling units, forcing them to cycle on for longer periods of
time.  Longer cooling cycles meant the units were taking out as much
moisture as possible from the vaults. This was especially needed in the
spring and fall.

One other trick we used was to have our refrigeration man set up a
special coil outside the cooling unit to recycle the "waste" heat from
the compressed freon. This was by far less expensive to operate,
(although a little more difficult to set up), as the heat was "paid for"
already.  This could be controlled by a humidistat.

The heat pipe technology sounds like it would be useful as part of this
kind of "reheat" system, but the theory behind it is not new, and must
be standard in the HVAC engineering world for large systems.  It might
be interesting, however, if used for a small space, which is using a
large "off the shelf" unit.  A caution however: if the cooling coils on
an air conditioner remain too cold for a long period of time, they can
sometimes ice-up.  Check with a good air conditioning man before playing
with your system, as I've seen some nasty damage in fur vaults from
misbehaving units.

I would be interested in hearing how the heat pipe manufacturers
recommend using their products.

Jerry Shiner,
Keepsafe Systems

                  Conservation DistList Instance 8:40
                Distributed: Tuesday, November 29, 1994
                        Message Id: cdl-8-40-001
Received on Friday, 25 November, 1994

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