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re: wood burning stoves
7 mar 1998
frank ("mr creosote") duffy wrote:
>nicksanspam@ece.vill.edu writes
>>...why not use a double wall chimney with cool outside air flowing down
>>the outside to act as an air-air heat exchanger and cool the flue gases
>>below their boiling point deliberately causing condensation, which runs
>>down the fluepipe back into the stove. why further heat and pollute the
>>outdoors?
why not, in fact, control the incoming cold air fan at the woodstove so
the outgoing flue gas temperature is, say, 150 f, using a cooling snap-
action thermostat attached to the outside of the inner pipe at the top?
>your choice but the trouble is that it just won't do that. the tar and
>creosote will build up inside the flue pipe, choke it so that you risk
>poisonous fumes escaping into your home and if it catches fire then you
>risk the building burning down...
doom, doom, doom.
i wonder why tar and creosote won't do that, ie condense in liquid form and
run back down into the stove at some lowish temperature, vs building up in
solid form inside chimney walls. surely there is a liquid temperature range
for these materials, between gas and solid. an insulated stovepipe can keep
them (mostly) in gaseous form until they leave the pipe, which seems ok but
thermally wasteful and polluting. an uninsulated masonry chimney with cooler
walls might condense them into a liquid which rapidly cools to a solid.
is there a mr in-between?
perhaps this would work better with greener wood, whose combustion products
contained more moisture, or with some fancy stove using water injection. if
the water vapor condenses inside the chimney, and never leaves the house,
green wood might heat a house as efficiently as seasoned wood, with a cleaner,
more thermally efficient chimney.
nick
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