On Jan 15, 1:16*pm, "Dave Liquorice"
wrote:
On Mon, 14 Jan 2013 23:07:25 -0800 (PST), harry wrote:
Looking at images of stovepipe thermometers it seems that the "ideal"
flue temperature is between 120 to 250C.

It depends on what sort of stove your have.

Carry on.
The combustion gases need a certain buoyancy to overcome the
resistance of the chimney and stove.
The bouyancy depends on the temperature difference between inside and
outside temperatures.

The bouyancy required depends on how convoluted the gas passages/
chimney is, the size of the passages, the length of the passages and
the hieght of the chimney..
It varies too on how warm the chimney is and how much energy it takes
to warm up the chimney and maintain that temperature.

Conversly, to be efficient the flue gas temperature need to be as low
as possible.
But not so low as the cause condensation.

So your flue gas temperature needs to be as low as possible so long as
the chimney is still functioning/drawing and there is no white smoke
which indicates condensation is taking place in the chimney. It's
hard to achieve this under all conditions.
In practice, natural draught chimneys are bound to be inefficient
because they only work well over a narrow range of conditions and they
are upset by the outside air/wind conditions.