Linda Ferzoco on wed 24 may 06
If youse guys keep this up, you'll have me making my
own kiln! Now, if I knew anything about electricity.
Thanks Michael. What you do for us on Clayart is
quite generous.
Cheers,
Linda Ferzoco
--- Michael Wendt wrote:
> The MadSci Network has several excellent
> articles on this subject.
Michael Wendt on wed 24 may 06
The MadSci Network has several excellent
articles on this subject.
The question asked was how in the world could
a manufacturer claim that for low fire work, a thick
walled kiln would fire slower and use more energy?
The answer lies is thermal conductivity.
Brick is about 160 times better conductor of heat than
air. If you add 2" of brick on the outside of a kiln,
you
almost double the mass of the kiln. Heating due to
direct conduction is a much more efficient transfer
mechanism than convection into air so this combined
with the fact that the specific heat for brick is about
0.35 that of water, it takes more energy to heat the
kiln.
What to do?
Make the brick walls as thin as possible.
Back those up with graduated density of
Kaowool or Fiberfrax, 12 lb to 8 lb to 6 lb
per cubic foot densities respectively from the
hot face to the cool face.
Coat each layer's hot face with either a
titanium or zirconium wash to make them more
opaque to radiation.
Such a kiln solves many problems at once.
Lower dead mass means lower energy consumption.
Better insulation means slower, more uniform cooling.
Opacifier layers remedy the main weakness of fiber
refractories: at high temperatures the main mode of
thermal loss is radiation, not conduction through the
fiber.
For more reading, I have placed a link to the
MadSci Network at the end of this post.
Try it, you'll like it ;-)
Regards,
Michael Wendt
Wendt Pottery
2729 Clearwater Ave
Lewiston, Idaho 83501
USA
wendtpot@lewiston.com
www.wendtpottery.com
http://www.madsci.org/results.html?domains=madsci.org&q
=thermal+conductivity+of+air&sitesearch=madsci.org&sa=S
earch&client=pub-1458446060997439&channel=7471188999&sa
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99%3BALC%3A0000FF%3BLC%3A0000FF%3BBGC%3AFFFFFF%3BT%3A00
000%0D%0A0%3BGFNT%3A0000FF%3BGIMP%3A0000FF%3BS%3Ahttp%3
A%2F%2Fmadsci.org%3BFORID%3A9%3B
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