On Sun, 23 Dec 2007 18:42:00 +0000, The Natural Philosopher wrote:

Some types of woodburner, masonry stoves, actually use a massive fireplace
to absorb heat and then release it into the room slowly, these burn at a
very high power and wouldn't work with an insulated flue as they depend on
the flue passage as a heat exchanger, a bit like roman hypercausts.


Odd that. as the aga which is essentially that, was specified for an
insulated flue. Albeit of a lower spec than the wood burner.

The aga is massive but its flue is just a means of exhausting the gases,
there's no scope for getting more heat out of the flue gases so they
should not be cooled further, and as they are already quite cool they can
use a cheaper liner if fired on smokeless fuel, gas or oil. The aga I
mentioned earlier that would not draw simply did not have enough heat in
the flue gases to warm the massive chimney it was exhausting into, as well
as the other problems I mentioned.

The masonry fire is actually built into the chimney breast that then
becomes a "radiator" and thermal store, so the flue reaches high
combustion temperatures but is cooled by the massive structure. I'm not
familiar with them but I would expect the flue gases to actually leave the
top at a similar temperature to a conventional wood stove 150C.

AJH