Date: Wed, 14 Sep 94 16:08:24 -0700
Sender: Vanagon Mailing List <vanagon@vanagon.com>
From: riclvw@deety.radiology.arizona.edu
Subject: Re: kooltrons (was Re: STAT...)
sstones wrote:
>Also, they do not have plumbing, They have no moving parts at all. Yes I
>didn't beleive it at first either but appearantly it used Some sort of
>wonderful new semiconductor to transfer heat from the inside out or vice
>versa.
Actually, the Koolatron and other similar coolers use Peltier devices,
which are not really now or semiconductors. Here is an excerpt on the
Peltier effect from my Growler's CD-rom encyclopedia:
Copyright - 1992 Grolier Electronic Publishing, Inc.
thermoelectricity...
Peltier Effect.
... the Peltier effect only occurs at the junction of
dissimilar materials when electric current flows. Heat, called
the Peltier heat, is either emitted or absorbed at the junction,
depending on the direction of current flow. This effect was
discovered by the French physicist Jean C. A. Peltier in 1834.
Once again the basic nature of the effect was misunderstood;
Peltier believed that he had discovered a violation of Ohm's law.
In 1838, Heinrich Lenz demonstrated the true nature of this
effect when he used a bismuth-antimony junction and froze a drop
of water when passing electric current in one direction
(absorbing heat) and then melted the drop by reversing the
current (emitting heat).
Principle.
In the Peltier effect a net motion exists, and thus the charges
transport energy. The energy associated with each charge differs
in the two materials. When a charge moves from one material to
the other, at the junction it emits or absorbs this difference in
energy and causes the Peltier effect.
Uses.
The Peltier effect is used in refrigeration and heating; a modern
single-stage Peltier cooler can reduce temperatures to nearly 70
C degrees (125 F degrees) below room temperature. In comparison
to more conventional systems, Peltier coolers have the advantages
of very local heat transfer (occurring only at the junction) and
no moving parts; however, they also have the disadvantages of
lower efficiencies and higher costs.
Numerous special circumstances have justified the use of a
Peltier cooler. Important factors are its durability, resulting
from the absence of moving parts, and its versatility--by
reversing the current direction, it can be changed from a cooling
to a heating system. A number of electronic systems require very
local cooling or heating to obtain optimum performance; Peltier
systems are ideal in these instances and have been used with
transistors, lasers, microwave amplifiers, and light detectors.
Peltier coolers have also been used to maintain biological
samples during periods of storage and transfer. The largest
Peltier-effect systems built so far are air conditioners used on
U.S. Navy submarines.
So, now you know more than you wanted. :-P
A thermoelectric cooler is not much use here in Aridzona
during the summer, but neither is my ammonia cycle refrigerator
that came with my Weekender. I usually just load it up with ice.
Rich.
riclam@deety.radiology.arizona.edu