[Stoves] ventillation

[Crispin Pemberton-Pigott]

Dear Rajan

>> There is a significant risk with these devices and that is the problem 
>> of controlling the air flow through them once the fire dies down. The 
>> amount of heat lost up the chimney can be very significant when the 
>> wall is hot and there are open holes. It is not possible to close the 
>> chimney completely because it is never certain that a fire is 
>> completely out so CO would get into the home if the ventilation of the
wall is blocked.

>Will it be possible to close the air entry into the combustion area ( after

>the fire dies down ), leaving the chimney passage open ?   If possible ( if

>at all it is practicable ) this will maintain a very small amount of vacuum
( ie. partial vacuum ) 
>inside the fire-chamber, thus preventing any CO or combustion gases getting
into the home. 
>Of course there may be some minor leakage of heat through the chimney.

That is the best of all designs because it is inherently safe instead of
inherently risky. The idea of banning closures on the outlet of stoves was
considered by the World Bank in Mongolia in order to qualify for large scale
rollout. When combustion is bad, there is not so much of an issue because
stinky smoke immediately tells you things are not going well (in the room).
But super-clean burners are so smell-free that it is difficult to know when
they are leaking into the room. One of the consequences of advances in
combustion!

The closing of the air entry pretty much guarantees that the combustion will
be poor from that point on which is itself a loss (usually = high CO).

On another note, please pick up my earlier point, everyone, that there is a
two-bin TLUD available in Ulaanbaatar that allows for continuous operation
of an inherently batch-cycled stove. It can be arranged that one batch
automatically lights the next. At any point after the second one has
started, the first can be reloaded and the 'fuse' set to be lit by the
completion of the burn in the second.

It turns a batch stove into a continuous heat-output stove.

Regards
Crispin