wolit@rabbit.UUCP (Jan Wolitzky) (10/23/84)
I'm not sure that "thermal diodes" is the correct term, but I recall hearing a few years ago about the development of semiconductor devices that acted as heat pumps or refrigerators. Pass a current through them and one end got hot, while the other got cold. I think some company actually tried marketing a portable refrigerator using these. Does anybody know where I could get some specs on these devices, or buy some of them? -- Jan Wolitzky, AT&T Bell Laboratories, Murray Hill, NJ; (201) 582-2998
bottom@katadn.DEC (10/26/84)
Cambion makes them. They are, if I remember right, called Thermonic devices. We used them at the Pittsfield NH plant (cambion) to keep kapthon material cool as it was being attached to IC sockets. They take a bit of current and need to be heatsinked as the hot side gets quite hot. Cambion used to have a applications manual. Good luck! Dave Bottom Digital Equip Augusta, Me. (207)-623-6935 DNEAST::KATADN::BOTTOM
sleat@aat.UUCP (10/28/84)
[Apologies if this is a duplicate. Local evidence suggests the first posting never made it out of this system.] >I'm not sure that "thermal diodes" is the correct term, but I recall >hearing a few years ago about the development of semiconductor devices >that acted as heat pumps or refrigerators. Pass a current through >them and one end got hot, while the other got cold. I think some >company actually tried marketing a portable refrigerator using these. >Does anybody know where I could get some specs on these devices, or >buy some of them? >-- >Jan Wolitzky, AT&T Bell Laboratories, Murray Hill, NJ; (201) 582-2998 You might try: Cambridge Thermionic Corporation 445 Concord Ave. Cambridge, MA 02238 617-491-5400 I have an old data sheet (ca. 1979) for their model 801-1029-01-00-00 "Ceramic Module". Basic spec's are: Max Temp Difference >60degC Max Current 9 Amps Nominal Voltage 0.7Vdc Hot Side Temperature 50degC (max?) Max Heat Pumping Cap >3.3 Watts Max operating Temp 125degC The unit is a rectangular block approx .2 x .3 x 1 inches, with two 18awg pigtail leads. Heat is transferred across the .2 inch dimension (i.e., from one .3" x 1" surface to the other). The energy transfer rate, at a fixed current, is of course inversely proportional to the temperature difference. The given transfer capacity of 3.3 Watts is at 9 Amps with a delta-T of 0. From the rather cryptic performance curves given, it looks like you get about 0.2W across with 9 Amps at a delta-T of 50degC. Below 5 Amps, transfer rate is approxi- mately linear with current. Above that it begins to fall off (as resistance effects begin to dominate, I suspect), the slope reaching zero at about 9 Amps. Above 9 Amps, the slope goes negative. Nowhere on the data sheet does it mention that this is a semiconductor device, though the leads are color coded for polarity and the 0.7V suggests a semiconductor junction breakdown voltage. I believe that this exploits a phenomenon other than the Peltier effect, though my recollection on such matters is hazy at best. Any denizens of net.physics care to elucidate? Michael Sleator Ann Arbor Terminals {aatpdx, cbosgd, mb2c, psu-cs, uofm-cv}!aat!sleat
scott@wuphys.UUCP (Scott Barthelmy) (10/29/84)
[] A better name for these devices is "thermoelectric coolers" or more technically they work on the principle of the "Peltier effect". When an electric current flows across a junction of dissimilar materials heat is absorbed or released. The heat flow is a result of the different "electronic" heat capacities of the materials. The opposite of a thermocouple device. See also Seebeck and Thompson effects. The formula is: Q = pi * I where 'pi' (the Peltier coefficient) is of order 0.003 for metals 0.03 for highly doped semiconductors 0.3 for lightly doped semiconductors In practical units: 2 BTU/hour ~= 1 Volt*Amp*hour Junction temperature differentials can get up to 50 degrees centigrade. For a supplier of these devices, try: MELCOR (Materials Electronics Products Corp) 990 Spruce St Trenton, New Jersy 08648 (I am looking at their 1981 catalog so bewarned of changes.) There must be other suppliers; try EEM. These things have been aailable on the consumer product market for awhile. My parents had one of these "electronic ice chests" back in 1978. The ice chest was 3cuft and would keep a full load at ~40 using about 4-5 amps at 12 volts. The coooling unit was about 4"x4"x1". It could counter balance heat inflow through the chest insolation, but was terrible if you put a freashly roasted turkey in it. These devices can be used to heat things as well as cool. Simple joule heating is about 50% more efficent. Scott Barthelmy ihnp4!wuphys!scott "I am a child of the unixverse."
jeffw@tekecs.UUCP (Jeff Winslow) (11/01/84)
I could reply to this by mail, but this newsgroup doesn't get enough activity (only 30 articles here!) so ----- I think what you are talking about is called a thermoelectric refrigerator, based on the Peltier effect. If you put current through a junction of certain dissimilar metals or semiconductors (say bismuth and tellurium), the junction area gets cold. I think there are some beer-cooler type things to run off of a car battery that use this principle. One vendor of thermoelectric modules is Cambion, 1 Alewife Place, Cambridge, MA (02140). I can't speak for or against them, as I just happened to get a catalog of theirs, but it's a start. Jeff Winslow Switching supply designer An analog man in a digital world...
wls@astrovax.UUCP (William L. Sebok) (11/02/84)
The CCD (charge-coupled device) light detectors on the Wide-angle camera of the
space telescope will be cooled with such thermo-electric devices. There the
vacuum of space helps quite a bit in the thermal insulation.
--
Bill Sebok Princeton University, Astrophysics
{allegra,akgua,burl,cbosgd,decvax,ihnp4,noao,princeton,vax135}!astrovax!wls