[Stoves] Stoves Digest, Vol 39, Issue 21

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Tue Nov 26 03:27:29 CST 2013 

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2013/11/20 <stoves-request at lists.bioenergylists.org>

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> Today's Topics:
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>    1. Re: Cajun Rocket Pot Tested (Ronal W. Larson)
>    2. Household Burns from cookstoves. (Cookswell Jikos)
>    3. Re: In search for a stove model for the disaster in the
>       Philippines (Joshua Guinto)
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>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Mon, 18 Nov 2013 22:33:37 -0700
> From: "Ronal W. Larson" <rongretlarson at comcast.net>
> To: Discussion of biomass <stoves at lists.bioenergylists.org>,    Dale
>         Andreatta <dandreatta at sealimited.com>
> Subject: Re: [Stoves] Cajun Rocket Pot Tested
> Message-ID: <B73AFDB0-068F-44BB-AF78-C2D2DC0B0E88 at comcast.net>
> Content-Type: text/plain; charset="utf-8"
>
> Dale and Crispin:
>
>    This is to try to close the gap a bit.  Dale reports for his home gas
> range testing two differences in efficiency:  8.8 and 13.5  (the ?knobby
> aluminum? over the steel).  Crispin says the efficiency should be strongly
> modified by the materials and weight differences - which I can see makes
> sense.
>
>    My problem is that playing around with Dale?s stated power levels ("The
> power input to the regular pot was 1128 Watts, while that of the finned pot
> 1227 Watts, or 1.088 times as much."),  I can?t see from the given data,
> how Dale got those power numbers.  I think there should have been some
> water evaporated, but none is stated.  Did the 700 watt number come in some
> way?
>
>    So,  Dale, can you show the computations you used to get 1128 and
> 1227.? Adding in the specific heat of the pots (if you didn?t - and you
> might have) should help with better understanding both this geometry and
> the importance of including what Crispin wants to include.
>
> Ron
>
>
>
>
>
> On Nov 18, 2013, at 4:57 PM, Crispin Pemberton-Pigott <
> crispinpigott at gmail.com> wrote:
>
> > Dear Dale
> >
> > What a welcome report on a promising technology!
> >
> > I have several points that I?d like to raise which probably impact
> materially on your concluding numbers.
> >
> > I am happy to see at the end a discussion of the thermal mass of the
> pots and the fact they have different materials and different masses.
> Because the tests were conducted to check the heat transfer efficiency and
> the overall fuel consumption (two different metrics) at high and low power
> (again, two different metrics) I feel it is important to put the thermal
> mass in context at the beginning then move to the other points.
> >
> > The British, Indian, SeTAR and Indonesian heat transfer efficiency tests
> all consider the mass of the pot in the calculation. There may be many
> others ? I have not read them all, of course. I would like to investigate
> the implications of this.
> >
> > The work done heating the water (and the pot) is measured to the boiling
> point and includes heating the thermal mass of the water and the pot
> together. At the very end you mention the difference in in energy being
> 130,000 for the aluminum and 26,000 for the stainless steel pots. This
> 104,000 Joule difference should be applied to the portion of the test that
> involves changing the temperature, not the whole test because most of the
> time, there is no change in temperature.
> >
> > The answers sought related to portions of the test, which are separately
> reported (good). If we take the change in temperature to be 80? C then the
> energy needed to heat the water (calculated on the same basis as the energy
> needed to heat the pot) is:
> >
> > 5000 g x 4.186 x 80? = 1,674,400 J
> >
> > The pots used respectively 26,000 and 130,000 (from your calculation)
> >
> > Thus the two tests require 1,700,400 and 1,804,400 respectively for a
> difference of 1.061 in the heating work done. This means the improved pot
> was required to (and did) absorb 6.1% more heat during that portion of the
> test. Once the pot is hot, the impact of the pot mass disappears because
> the temperature is pretty much constant.
> >
> > Because the pot mass was not considered in your calculation, the
> ?additional heat gained? number (the claim that all things considered, it
> gains heat more efficiently) drops from 16.1% to about 10%
> >
> > 10/16.1 = 0.62, 1-0.62 = 0.38 = 38% under-reported performance
> >
> > I think recalculating it to include the pot mass would materially affect
> the conclusions ? i.e. that the difference in the calculated result is
> significant with a high degree of confidence.
> >
> > With respect to the determination of thermal efficiency at low power,
> the things being measured ? missing mass of water and energy consumption ?
> are not strongly correlated because, as you clearly explained, the losses
> of heat from the pot by routes other than evaporating water are large
> compared with the energy used for evaporating water. Very small changes in
> the local circumstances strongly affect the calculated result.
> >
> > For this reason, there was some time ago a general agreement that
> ?simmering efficiency? is not really a helpful indicator because the
> calculated efficiency of a perfect simmer is 0% which is counter-intuitive
> to the claim of the method applied. If you changed the low power fuel burn
> rate, you will get a different low power efficiency at each power setting
> because it is a method that does not actually report the low power heat
> transfer efficiency (or the fuel efficiency).
> >
> > I predict, based on your numbers, that if you were to test the same pots
> using cold water on a low power flame, the heat gained by the finned pot
> would be of a similar order of magnitude larger than the standard pot as is
> shown above, i.e. the difference between 10 and 16.1.
> >
> > The work done by the stove in heating the water can most accurately be
> measured when the water is not boiling for all the reasons you stated about
> conductive, convective and radiative losses. As we are testing the pot, not
> the stove or the fuel, it will be most accurate if the water and pot are
> heated from some temperature above ambient such as 30? (to ensure that the
> heat gain rate is continuous and stable) to about 70? above which point
> some evaporation can be expected, complicating the calculation and
> introducing the relative imprecision caused by a changing mass v.s. a
> changing temperature. Heat gain assessed by ?T is about 500 times more
> accurate than assessing it by ?M.
> >
> > The presence of a lid ensures that the heat gained is collected and not
> lost to radiation or small amounts of water evaporating. The result, the
> temperature rise of a 20? pot from 30? to 70?, is a very good reflection of
> the gained by the pot and virtually eliminates errors.
> >
> > I would be really interested to see the difference between these two
> methods reported for that very same pot, taking your set of experiments as
> a baseline. I predict that the improvement in heat gain, calculated from
> 30? to 70? and taking into consideration the pot material and mass, will
> show an improvement of about 16% for a steady state fire of any magnitude
> that you used.
> >
> > Where my estimate will be wrong is the low power comparison because the
> baseline is not really a measure of heat transfer efficiency, but my
> estimate not it will not be as wrong as the baseline number.
> >
> > As the finned pot is claimed to be for cooking with gas (as I understand
> it) only two need be need be performed for high and again for low power
> (one for each pot type).
> >
> > Because the heat transfer efficiency is not dependent on the mass of
> water in the pot, the water does not need to be exactly 5000 g if the pot
> mass is considered. This is important for testers to realise.  This
> mass-independence was recently confirmed again by students at the China
> Agricultural University to a high degree of precision (four nines) across a
> wide range of ?pot fullness?.
> >
> > I find this knowledge really helpful for comparing stoves that do not
> deal well with such a large pot. Putting in 4 litres of 5, or 6 would not
> change the calculated heat transfer efficiency because it doesn?t
> measurably vary. But the pot mass must be considered if there is a change
> in water temperature.
> >
> > If there are other experimenters in Stove Land who have finned pots it
> would be great to hear from them as well, comparing not only the different
> appliances, but the different calculation methods.
> >
> > Best regards
> > Crispin
> >
> >
> > A few months ago we had a discussion of Cajun Rocket Pots, a series of
> pots with heat transfer fins on the bottom meant for cooking seafood in the
> Southern US.  Their claim was that their pots reduce fuel use by 50% and
> reduce time to boil considerably.  (The name ?Rocket Pot? has nothing to do
> with the rocket stove.)  I gave the opinion that their design was excellent
> and that it would revolutionize our cookstove work.  All we had to do was
> test it on some stoves of the type we use and confirm that it works.
> >
> > Alas, reality interfered.    I got one of their pots, the 8 quart size.
>  This is their smallest size and is appropriate for a 5 liter water boiling
> test.  The finned pot performed only marginally better than a regular pot
> of the same size, typically by about 10%.  Very disappointing.  It?s
> possible that for certain types of stoves with certain shapes of gas
> burners the pot really does perform well, but it did not perform
> particularly well on any of the stoves I tested.
> >
> > I?ve attached a report with the test details of a finned and a regular
> pot being tested on 7 different stoves.  Some stoves gave better results
> than others, but the 10% improvement is a typical number.
> >
> > Dale Andreatta
> > <Cajun Rocket Pot
> Report.pdf>_______________________________________________
> > Stoves mailing list
> >
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> >
> > for more Biomass Cooking Stoves,  News and Information see our web site:
> > http://stoves.bioenergylists.org/
>
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> ------------------------------
>
> Message: 2
> Date: Tue, 19 Nov 2013 09:48:28 +0300
> From: Cookswell Jikos <cookswelljikos at gmail.com>
> To: Discussion of biomass cooking stoves
>         <stoves at lists.bioenergylists.org>,      fernyverwiel at gmail.com,
>       Global
>         Alliance for Clean Cookstoves <info at cleancookstoves.org>
> Subject: [Stoves] Household Burns from cookstoves.
> Message-ID:
>         <
> CAA-40HLpX_5TYDKLhXcDOi76ihTxReOyusH5tCYK086+LUXV-w at mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Dear all,
>
> I was contacted by my friend Ferny who does amazing work at local Kenyan
> hospitals, she is very concerned about the number of children coming in
> with serious burns from the cookstoves.
>
> Here is part of the email in which we were discussing this:
> "I have a question or rather suggestion. Can you or maybe you know of
> someone, think about the following.I initiated a project 7 years ago to
> entertain kids in hospitals with clowning, puppetry, storytelling music
> etc. We work in 10 locations. We see a lot of children with severe burns,
> like really bad almost 50% of their body, from falling in hot sufuria's.
> Can someone think of some sort of safety device, a frame to put around or
> anything to protect the kids from falling in. Maybe you could even get
> funding for this so that people don't need to spend a lot of money buying
> it. I don't know if there is a market, I am only thinking out loud to
> prevent the kids from getting burned. And maybe you have nothing with this
> then that is also fine. I am just concerned and thought maybe someone can
> have a very good idea....juts a thought. And maybe you can get some
> business out of it, or if someone wants to sponsor it. Would love to hear
> your thoughts. have a great day salaams,Ferny
> www.sarakasihospitalproject.org""
>
> Please let us know if anyone has any ideas about saftey systems for stoves.
>
> I feel that perhaps it could also be alot of social issues surrounding
> this, i.e. working mom's whose eldest children cook for the rest, lack of
> kitchen saftey training etc.
>
>
> Many thanks in advance.
>
> Teddy
>
> *Cookswell Jikos*
> www.cookswell.co.ke
> www.facebook.com/CookswellJikos
> www.kenyacharcoal.blogspot.com
> Mobile: +254 700 380 009
> Mobile: +254 700 905 913
> P.O. Box 1433, Nairobi 00606, Kenya
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> ------------------------------
>
> Message: 3
> Date: Tue, 19 Nov 2013 16:46:29 +0800
> From: Joshua Guinto <jed.building.bridges at gmail.com>
> To: Discussion of biomass cooking stoves
>         <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] In search for a stove model for the disaster in
>         the     Philippines
> Message-ID:
>         <CABxLnO2JVzb6w5c4F89uW9b6ffwM1gbJPO=
> E8-YiNj-4eYPRLQ at mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Dear All
>
> First of all, i would like to thank everyone who pitched in their ideas,
> references and support in my search for the stove model best fitted to the
> scenarios in the Philippines after the Typhoon Haiyan. To mention a few....
> a new TLUD stove model from Dr. Paul Anderson, the Estufa Finca from Art
> Donelly, the brick institutional rocket stove from Jon, Larry and others,
> the Siliver Fire Stove, the charcoal stove from Gustavo, the Jompy Water
> Boiler and all the rest that i might have failed to mention. I thank you
> all.
>
> Now that i received some initial fund from a friend, i was able to buy the
> plane ticket. Tonight, i leave for Manila from here at my home town and
> then tommorow noon, i will be in Cebu. the first stop is to meet a circle
> of supporters there and evaluate and organize a pilot manufacturing outfit.
> We will see, which stove model we can quickly manufacture and hopefully, on
> the third day, i can already bring to Tacloban for actual tests at the
> evacuation center. I may have to jump back and forth between the
> manufacturing and the actual stove use several times. I will see how it
> goes.
>
> Along with the stoves, i will be working on water filters, rain water
> collectors, container gardening (which is why the biochar making  component
> of the stove is very important) and even toys for the children. There is
> much yet that i do not know so every thing is pretty un structured as this
> moment.
>
> Will tell you more news in a few days.
>
> Good day to all
>
> Jed
> Philppines
> To Cebu and Tacloban
>
>
>
>
>
>
>
> 2013/11/16 neiltm at uwclub.net <neiltm at uwclub.net>
>
> > On 11 Nov 2013 at 12:00, stoves-request at lists.bioenergylists.org wrote:
> >
> > > Tin canium Rocket stoves with say ash insulation would be cheap and
> > > fast but no charcoal.
> >
> > My experience of doing that is that the tin can burnt through after about
> > 3 firings, but uninsulated will last much longer and still be an
> > effective stove.
> >
> > It is also perfectly possible to obtain some char at least from a rocket,
> > especially if the stove is extinguished after use by removing unburnt
> > wood and snuffing it in a tin with a lid along with all the remaining
> > char.  My StoveTech rocket can actually liberate similar amounts,
> > sometimes more char that way then my Reed TLUDs, and mine is not even the
> > char making version.
> >
> > Not so relevant in the Phillipines right now, but by using an old kettle
> > BBQ as a fire bowl with the bottom half filled with earth, after the fire
> > has died down, by placing the lid on and sealing the little vent with
> > earth this liberates a bucket full of char.
> >
> > Neil T
> >
> > _______________________________________________
> > Stoves mailing list
> >
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> >
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> >
> > for more Biomass Cooking Stoves,  News and Information see our web site:
> > http://stoves.bioenergylists.org/
> >
> >
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> ------------------------------
>
> End of Stoves Digest, Vol 39, Issue 21
> **************************************
>



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Chinese agriculture technology network pays tribute to the global peers!
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