[Stoves] Stove ID please - 2-pot stoves - testing needed

[Dean Still]

Dear Crispin,

Rocket stoves are defined by Dr.Winiarski's 10 design principles. Using a
grate is common and found in many Rocket type stoves that can range from
single pot to griddle stoves to bread ovens to dryers, etc.

I agree that the aim is to have all the gases and smoke go into the flame
which is easier in a TLUD because the flame rises evenly from below filling
a space. Another part of designing a clean stove is to only make the right
amount of gas and smoke that will enter the right amount of flame. In many
ways, successful TLUDs and Rockets can be described by a shared set of
design principles. Be interesting to get together and discuss at ETHOS!

Best,

Dean

On Sun, Dec 30, 2012 at 4:03 PM, Crispin Pemberton-Pigott <
crispinpigott at gmail.com> wrote:

> Dear Paul****
>
> ** **
>
> Some interesting suggestions.****
>
> ** **
>
> >And I am sure that there are other 2-pot stoves, but just not being
> stamped out and with such smooth edges.   Many of us have made such units.
> ****
>
> Yes there are lots of two or three pot stoves. The overall efficiency of
> even a crummy one is pretty good because…two pots are better than one.****
>
> >What is needed is some serious study of these useful features, whether
> built into the stove or as an attachment.   Issues to be studied include:
> heat transfer to EACH pot
> types of pots used (sit on top or inserted)
> insulation
> temperatures of the outside surfaces
> fuel efficiencies attributed to the second pot****
>
> The reporting of the performance is of course important so that
> prospective buyers can consider the aspects that related to their needs.
> Cecil Cook is working on a modernised social impact assessment methodology
> that will make it easier to decide what to report and how to conduct an
> acceptability ‘test’.****
>
> And of course, the ways of supplying heat to the 2-pot stove structure.
> The fact that both the Prakti and Envirofit units use Rocket combustion
> structures does not exclude use with other combustors, such as TLUDs and
> even fossil-fuel burners.****
>
> I have a quibble here about what is and is not a ‘rocket’ stove. A Rocket
> stove does not have a grate and there is, provided by Dean, a fairly tight
> definition of what conforms and does not conform to a Rocket stove design.
>  As he pointed out (re the Uganda stoves) that some people do and some
> people do not make Rocket Stoves. Side-fed stoves have been around forever.
> Are they all Rocket stoves? Looking at the design from the 90’s it seems
> not.****
>
> Important note:  These 2-pot structures both (virtually all of them?) have
> a chimney because horizontal flow of the hot gases must eventually have
> some upward movement to maintain the draft (exceptions if there are fans in
> use).   For the TLUD combustors, the chimney is a nice enhancement of the
> draft.****
>
> There are several stoves that do not use a chimney but have cross drafting
> of the fire. Provided the total draft is adequate to move the gases, it
> works. There are ‘improved’ versions with elevated second pots.  The Anagi
> is one but there are many others. The advantage of not having a chimney is
> higher heat transfer efficiency because of slow moving gases and more
> residence time. Putting on a chimney can greatly reduce the efficiency due
> to too much excess air being drawn in. As most people to not have a
> combustion analyser available, they do not know what the excess air level
> is and have to guess as to whether it is improved or not. Adding a damper
> is usually a hit-and-miss affair because we never know what is really going
> on. Of course the chimney removes all the smoke but maintenance is then
> needed as chimneys get clogged if the combustion is not good in the first
> place. In Indonesia chimneys added to unimproved stoves have to be cleaned
> as frequently as every 1-2 months.****
>
> I did not understand Crispin's comment about keeping the smoke and flames
> together.****
>
> Yes you do – the concentrating disk idea!****
>
> >>It seems to me to be worth investigation the % of smoke that can be
> burned by keeping the smoke and flames together for a while. ****
>
> >That is true for "stick-burners" like the Rockets.   But TLUDs are
> "gas-burners" (that make their own gases in the close-coupled gasifier
> reactors.)   What would be the best ways to get the best results with
> Rockets, TLUDs, or other heat sources?
>
> ****
>
> All smoke should be burned. End of short story. If the smoke can evade the
> flames, it gets away.****
>
>
> >But the question is:   who will pay for these tests, and who will
> release the results?   ****
>
> ** **
>
> It is likely that the easiest funding are projects that need the
> information. To do that the product has to past first inspection for having
> a chance. The Indonesian stove programme is likely to do this. The roadmap
> calls for this. Product descriptions and performance expectations will be
> generated by the recipient communities and products evaluated against them.
> ****
>
> ** **
>
> Regards****
>
> Crispin****
>
> ** **
>
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