On Jun 11, 11:42*am, Roger wrote:
The message

from NT contains these words:

go watch a balanced flue boiler burn on a windy day.

I have but conditions are rather different when the boiler is firing.
When the boiler isn't firing there is no gas flow out of the
combustion
chamber, only an essentially static air mass with marginal pressure
changes as the outlet is buffeted by the wind.
think turbulence, the wind blowing across the open-ish ends creates it
Yes but it is *not* turbulent flow and does nothing to promote air flow
out of the combustion chamber.
you dont say what you mean by 'it' there.

Funnily enough it is the same 'it' that immediately precedes my 'Yes' above.

I think anyone would know
that air blown across the ends of a wide tube causes turbulence in the
tube, and the resulting churning causes slow exchange of internal with
external air. If you dont... I dunno.

In the mouth of the tube, not along it for any significant distance if
the far end is sealed. All you get further down the tube are slight
fluctuations in pressure which are not driving anything anywhere.

You could of course rely on the random movement of the air molecules to
eventually clear all the original contents of the combustion chamber but
I think you would find that the time scale for that is weeks, if not
months or years. Would fit your claim to "low exchange of internal with
external air" though.

Air exchange by random molecular motion _in gases_ is fairly fast. In
liquid it would take days.


NT