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burner behaviour + why chimneys work - ivor's mention, or,

updated sun 25 mar 07


pdp1@EARTHLINK.NET on sat 24 mar 07

respecting an aside within it...

Hi Ivor,

You mention -

"By the way, logically, a down draft kiln should not draw because the entry
point and exit points for air movement are at the same elevation. Just a

It should draw fine if they were lower, or higher, for that matter, if one
is deferential to it's requirements to do so in how one tend the matter.

Things tend to 'do' exactly what we ask them TO do, and, they will always do
so reliably, and in their terms of it.

The question always, is "what" are we asking them to do? in their terms of
it? How are we co-operating with them?

Certainly in any situation with Wood Burning Stoves or their likes, one can
run the Chimney horizontally and from the bottom, then down, then up, then
down, then around, or even lower than the lowest otherwise, then over, and
around, then where-ever, then 'up' , or not 'up' but have a Fan there at the
end...and so on, and the Stove will draw fine so long as one make a fire of
some sort first IN the exhaust end of the Chimney TO encourage and initiate
the flow of the desired Draft...or other places along the way also if need
be, or lets the Chimney be hot enough in it's length, or having a Fan either
'pulling' or pushing from a "Y", and so long as nothing is interfering with
the egress at the one deferentially let the main Fire increase
to find it's Legs...and not outrun the rate at which the egress is
progressing or the peak to which it shall function.

This should be no different in a Kiln...

And this seems entirely 'Logical" and to be Logically anticipated, to me.

Things of whatever sort will wish to behave according to the conditions
defering to, or impedeing them....and, always, in their terms of it...

And, one can count on it.

Best wishes...

l v

----- Original Message -----
From: "Ivor and Olive Lewis"

Dear John Baymore,

Given the equation you provide and allowing for my modest ability with
elementary mathematics, could you provide some help with a worked example.

p = p0 exp(-Mgy/RT)


p = corrected pressure (mb)
p0 = Sea level pressure (about 1013mb)
y = Altitude (in metres above sea level)
R = Gas constant (J/mole/K)
M = Molar mass, air
T = Temperature (Kelvin)
g = Gravitational constant

I can cope with sea level pressure and altitude. I have a value of 8.31441
for R. I am unsure about the molar mass of air, where does this value come
from? Deg K is no worry, just add 273 to Deg C.And the tables book tells me
the Gravitational Constant G is 6.672 .

So what is exp and how do I use it. There is a button on my calculator EXP
. My barometer reads 1015 hectopascals today, how do I correct it. We are
about 100m metres above sea level.

I would appreciate your help.

By the way, logically, a down draft kiln should not draw because the entry
point and exit points for air movement are at the same elevation. Just a

Best regards,

Ivor Lewis.
South Australia.