[Stoves] Why doesn't charcoal burn in the Champion TLUD?

[Julien Winter]

Dear Huck;

Charcoal from pellets burn slowly in a Champion-type TLUD, because there is
not enough primary air movement.  The resistance to gas movement in the
charcoal bed is too high.  Also, there isn't the draft from a strong
pyrogas flame.

If you burn wood chips or sticks, the gas permeability of the char bed is
high, and the charcoal will burn off quite well.

It would be nice, however, if one can get the charcoal fire closer to the
bottom of the pot so that there is better transmission of radiant heat.
Paul has a TLUD for that which breaks in half when the pyrolysis phase is
complete.  Otherwise the path between the char fire and the pot should be
well insulated.

Some people mention how good it is to have a fan to force the primary air.
That is true for pellets, but not so much for sticks and chips, because
their permeability is already high and their bulk density is low (so you
will burn off your batch of fuel is 10 minutes if you force the air).

(I should note that the gas permeability of a bed of fine wood chips (< 10
mm)  is also low).

I keep promising data to show this.  Its coming soon.

Cheers,
Julien.

-- 
Julien Winter
Cobourg, ON, CANADA
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