[Stoves] radiant heat capture, total heat measurement

[ajheggie at gmail.com]

On Sun, 11 Mar 2012 07:30:24 +0700, Paul Olivier wrote:

>>
>
>It is impossible to light the burner with the strainer in place.
>So in lighting a burner, I have to run it for a short while without the
>strainer.
>And when I put the strainer on the burner, I always have to turn down the
>fan.

Does the fan simultaneously supply primary air ( for the gasifier) and
the secondary air to burn the offgas? You mention the initial flame
pyrolysis/gasification in the primary chamber migrates to the burner
holes after some time.
>
>To get full and uniform ignition at all burner holes without the strainer,
>a certain fan speed is required.
>But to get full and uniform ignition at all burner holes with the strainer,
>a lesser fan speed is required.

Difficult to judge without seeing things but my guess this is to do
with air:fuel mixture rather than flame speeds. Initially the burn in
the primary chamber using more air than necessary for gasification
(secondary burn happening to some extent in the primary chamber}.

>With the strainer the flames are far more consistent and stable.
>The flames acquire structure and are not easily influenced by the wind.
>This gives me reason to believe that the transfer of convective heat is
>much more efficient when a dome is present.
>So with a more efficient transfer of heat by convective means
> and with the whole new dimension of thermal radiation that comes into play,
> a lot more heat makes it into the pot.

We'd need comparative (i.e. they don't need to be exact, given the
problems with thermocouples in a gas stream) temperature readings both
above and below the dome and in the same positions with the dome
removed.

I can see the strainer/dome acting as a means of shielding, mixing and
providing turbulence.

I can't see what effect it would have in changing the flue gas
characteristic to change the way the gases reaching the pot are
transferred to it. The fact that you lower the fan rate when the dome
is in position makes me think that with the fan dome you supply less
excess air, this increases the flue gas temperature and thus the delta
T twixt flue gas and pot increases heat transfer.

AJH