Hi all

There is a vast difference in the "specific heat" and the "thermal
conductivity" values for expanded polystyrene and capped honey.

The wire I used in my first trial was "NiCrome" intended for domestic
"electric fire" elements and very similar to that used for cutting expanded
polystyrene.

There is much confusion between "temperature" and "heat".

In this circumstance the temperature drops rapidly as heat is transferred to
the honey and cappings. If you can maintain the energy input to match the
heat lost then all will be fine.

I envisage a successful version having a "V" shaped stainless steel blade
with individual tubular heating elements mounted in the thick part at the
back of the blade. Each heater would have its own solid state energy
regulator controlled by a thermocouple mounted in the thinner part of the
"V" alongside the heater so that as a particular part of the blade was
cooled the heater cut in to make up the temperature.

You could sort this out by working from the desired rate of uncapping
(frames per minute)
multiplied by the mass of honey and wax involved, the temperature difference
between starting and finishing each frame.

I do not know the specific heat of capped honey, or the amount that would be
melted per frame to achieve uncapping, otherwise I would do some precise
calculations here.

I would suggest we would want to achieve a time of 5 seconds to uncap both
sides of a frame (12 frames per minute seems a sensible possible workrate)
but each uncapping motion takes place in one second, as the rest of the 5
seconds is handling time.

Here are some guessed figures...
say the mass of honey and wax involved is 100 gm per frame (50 gm per side),
that the specific heat of wax and honey is 1 (total guess),
that the temperature shift of the items that are warmed is 30 degrees C,

100 x 30 x 1 x 4.2 (joules equivelent) = 12,600

that is 12,600 joules, which needs to be delivered in two, 1 second bursts
of 6,300 joules. As a Joule is a watt per second that means a maximum energy
input of 6.3 kilowatts.

It may only be guesswork but any 500 mm length of NiCrome wire would
vapourise if you tried to input anything like that energy level!

Regards From:- Dave Cushman, G8MZY
Beekeeping and Bee Breeding, website
http://website.lineone.net/~dave.cushman
Archives of IBList, website http://website.lineone.net/~d.cushman