Bert - 24-11-2016 at 19:35
After looking at the hot air bath/repurposed heat gun thread-
How about radiant heat rather than convection?
If you have seen a quartz halogen lamp tube heated rotary pizza oven? Radiant heating is fast/quickly responds to current changes and is not limited
by characteristics of combustion or heat transfer capability of a working fluid (air, combustion gasses). It IS limited by color and reflectivity of
the target, and wavelength of the emmiter.
See here:
http://www.deltat.com/quartz_tube.html
Manufacturer claims these quartz halogen lamps can achieve process temperatures as high as 4,000 F.
Any one tried placeing a ring of quartz halogen lamps (with reflectors focussed inwards) around a borrosilicate or quartz tube containing a very high
temperature process, such as that used to distill SO3 from sulfates when making oleum or 100% sulfuric acid, or producion of elemental phosphorous?
https://www.sciencemadness.org/whisper/viewthread.php?tid=54...
m1tanker78 - 24-11-2016 at 21:29
I don't know about 4,000 *F but I've used radiant heating for small volumes where using a hotplate or heat gun is awkward. I've used both the conical
reflector types (like floodlights) and 500W quartz-jacketed types.
You almost need an off-axis parabola type of reflector with the quartz lamps. I fashioned a half ass reflector from polished stainless sheet. The only
advantage of doing this, as opposed to wrapping the test tube in foil and torching, is that you can see the reaction taking place through brazing
goggles.
An array of quartz lamps with reflector(s) will likely overheat and have very short service. An arc furnace works wonderfully for obtaining SO3 from
sulfates..
Bert - 24-11-2016 at 21:57
The manufacturers pdf linked here:
http://www.deltat.com/pdf/quartz_duo_tube_infrared_heater.pd...
Has purpose built tubes with the reflector built into one side of the tube. Probably rather expensive, compared to the cheap-o 500 Watt quartz halogen
tubes, of which I have a few dozen laying around.
Agreed, 4000 F. seems optimistic. Only 1,700 F. claimed for the self reflected tubes.
Arc furnace... Mmmm. Toasty.
[Edited on 25-11-2016 by Bert]
aga - 25-11-2016 at 09:27
A really small arc funace is great fun !
Melting blobs from the amlumino-silicate block (1560 C rated) kinds shows how hot the arc plasma gets.
Had a near miss yesterday - someone <i>almost</i> gave me a TIG welding rig.
They work on the basis of super hot plasma between the tungsten electrode and the workpiece, which would have been Big Fun to play with. Heigh ho.
Fulmen - 25-11-2016 at 13:57
A closed box is the definition of a black body, so you need reflective walls to keep the heat generation "off the walls" so to speak. That should be
the limiting factor for an empty radiant furnace. And you need filaments that can withstand the temperature and atmosphere, if not the need for
transparent high-temperature materials becomes a problem. I'm sure it could be useful in some applications, but for high temperatures there are many
limiting factors to consider.