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Re: Re[2]: Radiant energy cooktops

Westinghouse made a "Cooltop" range with four units, each driven by separate
oscillators operating at about 40kHZ to get above the audible range. This
LF EM field coupled most efficiently with a pan with a core of steel and an
cladding of copper to act as a temperature distribution means, because the
eddy-current pattern tended to be a hollow-circle so pancakes cooked
unevenly without the high conductive cladding. Copper and aluminum pans
were totally useless. Stainless steel pans were also non-effective. As
stated, the response was very much like gas cooking. But in the end this
most was not cost effective. The food was not any better, nor was it cooked
any quicker. It was a marketing gimmick.

Radiant cooktops and induction cooktops are two different devices. The
radiant types which Ken Johnson asked about essentially are lamps which put
out lots of energy at IR frequencies. Most metal pans are absorbers in
this range, so I believe that most will work. On the other hand, inductive
cooktops work by emitting RF frequency EM radiation. Non-ferromagnetic
pans are essentially transparent to this and do not heat. I own one of
these latter devices and shop for new pans with a magnet. Many pans for
sale will not work on this type of cooktop. It's advantage is that the
response time for both starting and stopping is very close to that of gas,
but without the open flame of gas.

This is interesting...I would have guessed that any metallic pan would work
with the RF cook top. I guess the heating is not due to eddy currents but
rather by causing magnetic domains to flip-flop? Hmm...I guess if your pot
boiled dry, the heating mechanism would automatically limit the pot
temperature to the Curie temp for that alloy?

Dewey
--------------------------hbjst@pop.pitt.edu-------------------------------
Homer B. (Jim) James Home: 1636 Jamestown Place
Adjunct Professor of Physics Pittsburgh, PA 15235-4922
Community College of Allegheny County (412) 731-3239 (voice)
Allegheny Campus http://www.pitt.edu/~hbjst/homepage.htm
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