[Stoves] Designs

[AJH]

On Sat, 05 Aug 2006 17:56:19 +0100, Steve Taylor wrote:

>I seem to have touched something useful off, with another lurker
>emerging from the woodwork with me (Hi Ian) and a useful discussion
>setting off ! 

I think so and my view is that it IS relevant to cooking for the
developing world, even if only for the fact that we in the comfortable
world know full well the consequences of breathing in unhealthy
environments, so solutions acceptable to us are also likely to be more
healthy.


>I have had a couple of private emails from list members,
>not quite telling me to bugger off, but almost, not very helpful.

This is the big wide internet, you know as well as I that people are
here for all sorts of reasons and point scoring often comes before
being helpful. A lot of this sort of problem stems from the way the
list is set up to reply to sender rather than list, also from the way
the thread you started developed you can see how dominance of billy
goat's software for lemmings has caused people to leap to the wrong
conclusions. Feel free to discuss this offlist I can send you a dxf of
something that will probably work with a bit of fettling and a small
12V air bed blower.

>Andy, are long sticks as the fuel source  desirable ? 

For the developing world I suspect they are, also historically this is
how cooking fires in UK developed from the iron age. If you look at
the "firewood" that seems to be available it is often carried in as
bundles, in UK we called them bavins and faggots. I suspect the reason
is that they could easily be harvested with a lightweight edge cutting
tool, to have to further comminute them is unnecessary effort. So they
were fed into the fire lengthwise and from differing angles, radiation
and heat loss effects meaning that they only burned in the centre of
the fire. You see a similar effect with andirons in an inglenook
fireplace.

>What happens when
>you don't have any ? Can you still fuel stoves with offcuts ?

Yes but as Kevin points out you need to look at the proposed fuel
resource before deciding on how to burn it. Woodchip and pellets lend
themselves to being trickled into the fire from the top to provide an
almost continuously metered fuel supply, this then is easier to
control and tune the air supply for optimum efficiency. Batch loaded
stoves use different principles to get the best out of the wood,
masonry stoves use their high thermal mass to absorb the heat from a
short, clean, powerful burn and then dissipate it over a long period.
TLUD batch loaded stoves use a unique characteristic of the pyrolysis
of a dry batch of wood to steadily produce a fuel rich gas,
downdraught burners use a similar phenomena to control the heat
feedback to the incoming batch of fuel to control its rate of burning.
The sort of fire you're probably used to seeing in a rural pub where a
big lump of part seasoning wood is sizzling away on a grate with only
sporadic leaps into flame is just how it shouldn't be done.

AJH