[Stoves] Lots of primary air

Anand Karve adkarve at gmail.com
Thu Aug 20 22:40:41 CDT 2015


Dear Crispin,
thanks for enlightening me.
Yours
A.D.Karve
***
Dr. A.D. Karve

Chairman, Samuchit Enviro Tech Pvt Ltd (www.samuchit.com)

Trustee & Founder President, Appropriate Rural Technology Institute (ARTI)


On Thu, Aug 20, 2015 at 4:57 PM, Crispin Pemberton-Pigott
<crispinpigott at outlook.com> wrote:
> Dear AD
>
>
>
>>your statement that the smoke might have become invisible due to its being
>> diluted by too much air, admits the fact that there was less smoke per cubic
>> meter of air, which is what all of us are aiming at.
>
>
>
> How about this:
>
>
>
> Consider a kitchen with an air turnover of 1 cubic metre per minute. You
> have a stove that emits 5 g of PM2.5 per minute.  It creates 1 cubic metre
> of emissions per minute. The PM2.5 level will stabilise at some level in the
> room depending on where the air exits, but usually through some point above
> the stove.
>
>
>
> Introduce another stove that has a higher excess air level emitting the same
> mass of PM per minute but in 2 cubic metres of air. That air cannot leave
> the room at 1 cu m per minute so it gets distributed further throughout the
> room. Because air is not moving around to distribute the PM evenly, and
> never will, the contaminated portion of the room increases, extending
> further from the stove.
>
>
>
> Some of the PM even goes back into the stove – maybe to be burned, who
> knows?  So the result of the lower concentration is not that it helps reduce
> exposure, it nearly all cases of real kitchens it will increase the general
> pollution in the room because the room has more ‘stirring’, in a way.
>
>
>
> In order to simulate this the WHO has two models of exposure calculated to
> give a more realistic result. One is a single box model which assumes all PM
> is evenly dispersed through the room and everyone in it breathes it. This is
> obviously far from reality.  A second model assumes a three-box approach
> which models a strong concentration between the stove and the outlet, an
> upper portion near the ceiling and a lower portion away from the stove. This
> is more realistic, but does not actually deal with the idea of dilution by
> circulating more air through the stove – it assumes all stoves have the same
> amount of excess air passing through. So it is going to misrepresent the
> exposure as well, but less badly.
>
>
>
> In order to calculate the exposure as a model of reality, the excess air
> level has to be incorporated into the model to deal with the expansion of
> the concentrated and upper level boxes into the ‘less polluted’ zone. The EA
> is not a reported metric so no one knows what the volume of pollutants is,
> and it cannot be realistically represented by the model.
>
>
>
> Generally speaking, reducing the concentration by increasing the gas flow
> rate through the stove increases the exposure by the cook to PM emitted from
> a chimney-less stove.
>
>
>
> Regards
>
> Crispin
>
>>
>
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