Roberto Escardo wrote:
"I was today with a geologist in our
University and she eplained me that TUFFA is CONSOLIDATED PUMICE !!!
(In fact they are the same material)
I hope to get some samples and try it for
combustion chambers. Looks promising.
Un abrazo
Roberto
I also get some values for thermal
conductivity of pumice: about
0.2 kcal/mh °C. It corresponds to a coefficient of thermal transmittance
K=0.58 Kcal/m2 h °C. ( When I find my table I will give you
an R equivalent) It depends on
granulometry."
Both Tom and Kevin wonder
about clay near the fire in combustion chambers and suggested alternatives.
Aprovecho is investigating two recipes for combustion chambers, both to be fired
by local brickmakers:
1.) 50% clay plus 50%
sawdust or other fine burnable material
2.) 85% perlite or pumice plus 15%
clay
Both recipes seem to make
durable insulative refractory materials. The second recipe is about .4 the
weight of water by volume. We are doing tests of durability and so far the first
recipe has been fired more than 100 times without much degradation. The second
recipe has withstood 50 heating and cooling cycles without apparent damage. BUT,
classes at the University of Dayton, directed by Dr. Margaret Pinnell, are
coming up with much more quantified data.
So far, clay seems to be
doing ok on it's own without a harder inner liner but everyone here agrees that
a hard refractory inside liner should protect the softer insulation from sticks
being pushed against the lower portion of the back inner wall.
I'll send samples
to Stuart Conway so the Colorado group can check it out at the November CO/CO2
meeting...
Best,
Dean
