[Stoves] Mewar Angithi: An In Situ Modification of the TSH as a Solution to the Problem

Francesco Tortorici francescot at gmail.com
Mon Dec 14 10:42:45 MST 2015


Dear Crispin,

Thank you for your response and examples.

Francesco
On Dec 13, 2015 6:16 PM, "Crispin Pemberton-Pigott" <
crispinpigott at outlook.com> wrote:

> Dear Francesco
>
>
>
> This device was discussed earlier this year (late last year?) on this
> list. Perhaps you did not see those messages.
>
>
>
> In terms of function, it is very similar to the grate added to the
> traditional Keren Stove from Java which is produced in the millions each
> year by artisans.
>
>
>
> The Keren was improved significantly, particularly in terms of fuel
> efficiency, by adding a sloped grate under the fire and admitting air at
> the back instead of all coming from the front. Another change was
> increasing the height of the cylindrical portion of the body above the fuel
> entrance which had the effect of lowering the fuel door height. Another
> modification was reducing the pot rest height from 25 to 7mm in order to
> cap t he total gas flow rate past the pot. This is the poor man’s
> alternative to controlling air entry.
>
>
>
> Here is the original:
>
>
>
> And here is the Keren Super
>
>
>
>
>
> And here is the Keren Super 2 which is in an insulated metal bucket:
>
>
>
>
>
> The other air entry holes (which were random, really) are all removed,
> with air entering only with the fuel and under the rear of the grate.
>
>
>
> The grate bar gap is important. It should be 4 to 5 mm (only) and the bars
> should be 12mm round or reinforcing bars. It is cheaper to use a smaller
> diameter but there is a difference in performance in that the air flow
> through the grate is spread over a larger area and the effectiveness at
> burning the charcoal is reduced.
>
>
>
> The stoves look almost exactly the same at a glance, but the performance
> is very different. The energy efficiency (fuel consumed energy to pot
> energy) for the traditional layout is about 16-17%.  The Keren Super is
> 27-28%. The main contributor is the taller top and lower pot rests.  The CO
> is reduced by the grate and air supply.
>
>
>
> The fuel saving is pretty large (1-old %/new %)*100% = 40% for such a
> simple set of changes.
>
>
>
> Anything that produces the same result will work, including the metal
> grate inserted under the fire.
>
>
>
> Here is a cast iron version of the Keren Super grate.
>
>
>
>
>
> Note that the legs on the left are taller than the right. The left side
> goes at the back and the short ones at the front. The casting pattern has
> all the legs the same length. The two sides are identical and the legs
> shortened afterwards. It is in two parts so it can fit through the hole.
>
>
>
> Care should be taken with the shape of the top of the stove so the
> different pot profiles all sit in such a way that the gap is 7mm. The gap
> is related to the circumference and the firepower. It does not scale
> linearly. If you change the pot and fire size a lot, check each gap 1mm at
> a time until you fine that it is optimised. If the gas flow rate is too
> low, smoke will emerge from the fuel door. It should *almost* do that.
>
>
>
> The Indian Chula can be improved by applying theses three adaptions: check
> the pot rest height, increase the cylinder height (reducing the door height
> as much as you an depending on the fuel that must get into it), add a grate
> with air enter at the back (to push the fire towards the centre, not
> against the back wall).
>
>
>
> The orientation of the grate bars should be front to back, not left to
> right. This allows the air entry to do a better job of pushing the fire and
> when fuel it fed in, it is more likely to push the ash through the grate
> and the charcoal to the back where the rear air will burn it cleanly.
>
>
>
> Have fun!
>
> Crispin
>
>
>
>
>
> Has anyone seen this addition to a traditional stone heart?  It is has been
>
> developed in collaboration with the University of Iowa.
>
>
>
> http://www.thesolutionsjournal.com/node/237379
>
>
>
> Francesco
>
>
>
>
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>
>
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