On Wed, 09 Feb 2005 11:22:47 GMT, "Karl Vorwerk"
wrote:

Anyone know anything about Peltier coolers. A friend of mine wants to cool
12"x15"x30" glass vivarium a maximum of 20-30 degrees farienhieght below
ambient temperature. It's long term for a salamander. A friend of hers got
her a surplus Peltier cooler. Which I installed. It didn't drop the
temperature very much inside the vivarium. After doing some research I don't
think it's powerful enough. As far as I know she doesn't have any specs on
it.
So the questions a
Is this a good way of cooling in this situation? Got any better suggestions?
Would house insulation sheet foam on 5 sides make an appreciable difference?
My first suggestion was air-condition the room but she doesn't like
air-conditioning. I'm in Hawaii so ambient temperatures are 59-90
farienhieght.
Thanks for any thoughts or suggestions.

Just one 15" x 30" pane of 1/8" glass will conduct about 730 watts
(4992 BTU/hr) if one side is 30 degF different than the other. That
seems like a lot, but I checked my math several times. I used k for
glass of 0.96 K/(W*m).

However, air is a pretty good insulator. I think if you could create
a "cool region" that is perhaps 6" lower than insulated surroundings,
a little depression, then a cold plate at the bottom of that region
could cool it by 30 deg. With no turbulence, cooled air would stay in
the depression and insulate the region. If the region were 12"
square and 6" deep, the heatflow necessary to maintain a gradient of
30 degF from bottom to top of that air volume would only be about 0.25
watt. A Peltier can easily do that. I'm looking at a Peltier 1.6"
square that can pump about 35 watts with a coldsurface temp of 40F and
a heatsink temp of 80F -- assuming you can keep the warm side of the
Peltier that cool.

If you use a small dorm-size fridge, the best way would probably be to
have a water heat exhanger comprised of a little pump, a coil in the
fridge and plastic water lines to a cold plate in the valley in the
vivarium.