[Stoves] Effect of ambient temperature on stove testing at lowpower
Ingelore Kahrens
tutaonana at onlinehome.de
Tue May 31 11:26:09 CDT 2016
Hello all,
I have been following your discussions for some time with great
interest. And I would like to add my experiences with retained-heat
cookers.In our organization in Kenya we promote them along with improved
stoves and solar box cookers. Women make the retained-heat cookers with
baskets and like them very much. As far as your opinion about cooking
ugali in these basket cookers is concerned, I have to object seriously.
You start cooking the ugali on a fire and as soon as it is hot you
transfer it to a basket cooker. The finished product is very tasty. This
is what the women we have worked with have confirmed. Besides, the same
holds for solar-cooked ugali.
Cheers,
Ingelore Kahrens
Am 31.05.2016 um 17:15 schrieb Cookswell Jikos:
> Dear Kirk -
>
> ''Dieter has brought up the concept of retained heat cooking in an
> insulated container. Would anybody even need turn-down in a cook
> stove? Is retained heat cooking the better solution, or is it good to
> have both?''
>
> I think it would very much depend on what is being cooked and in what
> type of kitchen setting. If this question of ambient
> air temperature has more than noticeable effects on the
> stove performance, then it is something I imagine a cook would approve
> or disapprove of and that can make or break a sale (or a 'user' using
> in the case of a free stove).
>
> Say you sell the same stove to be used in an igloo as for a maasai
> manyatta...would your customer notice any differences that
> would affect the quality of making dinner etc.? Retained heat works
> for some foods, but for staples like fufu, (sima or ugali) that need
> to be boiled, and then vigorously stirred and then simmered it gets
> tricky as does stir-frying.
>
> There is (a simmering?) demand in Kenya for simmering cookstoves in
> SME settings, the popular one right now is a smokey sawdust stove that
> is basically a metal cylinder with a door tube that you pack with saw
> dust around two glass bottles stacked like a rocket stove - you
> then remove the bottles and fill with firewood and light the bottom
> side. This lets the water boil on the firewood phase and then the slow
> burn of the saw dust keeps the water simmering. They are used by
> 1000's of small eatery joints around Kenya for keeping goats head soup
> warm and also keeping ugali (like polenta) warm wrapped
> in polythene plastic bags!
>
> I would like to know more about all these different tests Crispin
> mentions - how many cookstove tests are there in total? Between the
> VITA the ProBEC and the StarSOP, who uses which tests...do the various
> Govts. and Donors agree on one test for the most part? I do suppose
> though that given the phenomenal variations in global cooking and fuel
> type that an equally complex set of testing procedures would be
> needed. My only concern is how does the end user of the stove make use
> of this information in their day to day life? Do any of them provide
> for a simple energy star style of rating for ease of laymans
> understanding? What would the 'stars' be for,
> emissions, efficiency, durability, safety?
>
> Many thanks,
>
> Teddy
>
> On post note:
> In regards to cooking in igloos - Wiki says a Quilliq
> <https://en.wikipedia.org/wiki/Kudlik#/media/File:Qulliq_1999-04-01.jpg>
> is used to burn seal or whale fat...I wonder what tier these would
> fall under? But could lard as a cooking energy source though? Would it
> count as biomass? We once tried to make a jiko with Dad that used the
> falling fat from the goat ribs to flare up with enough heat to cook
> another set of ribs...but they were so tasty we never managed to
> finish the experiment ;)
>
>
>
>
>
>
> *
> *
> *
> *
> *Cookswell Jikos*
> www.cookswell.co.ke <http://www.cookswell.co.ke>
> www.facebook.com/CookswellJikos <http://www.facebook.com/CookswellJikos>
> www.kenyacharcoal.blogspot.com <http://www.kenyacharcoal.blogspot.com>
> Mobile: +254 700 380 009
> Mobile: +254 700 905 913
> P.O. Box 1433, Nairobi 00606, Kenya
>
> Save trees - think twice before printing.
>
>
>
>
>
>
> On Tue, May 31, 2016 at 11:34 AM, kgharris <kgharris at sonic.net
> <mailto:kgharris at sonic.net>> wrote:
>
> Prof Lloyd,
> This is great! The heat loss from the pot is less because the
> room temperature is higher. Thus I can't keep the water
> temperature down. I will definately think this one through and
> try some experiments.
> Dieter has brought up the concept of retained heat cooking in an
> insulated container. Would anybody even need turn-down in a cook
> stove? Is retained heat cooking the better solution, or is it
> good to have both?
> Thank You,
> Kirk
>
> ----- Original Message -----
> *From:* Philip Lloyd <mailto:plloyd at mweb.co.za>
> *To:* 'Discussion of biomass cooking stoves'
> <mailto:stoves at lists.bioenergylists.org>
> *Sent:* Tuesday, May 31, 2016 12:59 AM
> *Subject:* Re: [Stoves] Effect of ambient temperature on stove
> testing at lowpower
>
> Dear Kirk
>
> I have lurked during this discussion – forgive me for entering
> it now.
>
> You believed “the increase in ambient room temperature had
> changed the turn-down performance of the stove.”
>
> You may have been mistaken. I think what happened was that the
> ambient room temperature changed the measurement you were
> attempting to make. At the higher ambient temperature there
> was less rate of heat loss from the cooking pot, so it took
> less fuel to keep it hot and the turndown ratio – as you
> define it – changed. So the problem may lie with your
> definition of the turndown ratio. I use the minimal
> sustainable firepower, determined from the rate of fuel feed
> which just keeps the fire going, as my lower measure, and the
> maximum firepower I can achieve without significant oxygen
> starvation as the upper one, and have yet to see the sort of
> effect of ambient temperature on the ratio of the upper to the
> lower that you report with your definition of the ratio.
>
> In a word, you may be picking up a change in the heat transfer
> from the pot as the ambient temperature changes, rather than
> anything fundamental about the stove performance.
>
> I hope that suggestion assists.
>
> Kind regards
>
> Prof Philip Lloyd
>
> Energy Institute, CPUT
>
> SARETEC, Sachs Circle
>
> Bellville
>
> Tel 021 959 4323
>
> Cell 083 441 5247
>
> PA Nadia 021 959 4330
>
> *From:*Stoves [mailto:stoves-bounces at lists.bioenergylists.org
> <mailto:stoves-bounces at lists.bioenergylists.org>] *On Behalf
> Of *kgharris
> *Sent:* Tuesday, May 31, 2016 8:08 AM
> *To:* Discussion of biomass cooking stoves
> *Subject:* Re: [Stoves] stove test
>
> Crispin,
>
> My original statement was to point out how the increase in
> ambient room temperature had changed the turn-down performance
> of the stove. This is an important topic if the stove
> principles are going to have any effect in hot tropical
> countries. If you can comment on this I would be happy to
> learn from your experience, but please stop hijacking my posts
> and misdirecting attention to cater to your agenda against the
> current test methods. Start your own thread if that is what
> you want to talk about.
>
> All,
>
> I will be happy to answer questions about the burning
> abilities and tecniques of our stove and combustor.
>
> Kirk
>
> ----- Original Message -----
>
> *From:*Crispin Pemberton-Pigott
> <mailto:crispinpigott at outlook.com>
>
> *To:*'Discussion of biomass cooking stoves'
> <mailto:stoves at lists.bioenergylists.org>
>
> *Sent:*Monday, May 30, 2016 9:40 PM
>
> *Subject:*Re: [Stoves] stove test
>
> Dear Kirk
>
> >With the support of Aprovecho Research Center, I (actually
> we) have developed a very good, clean burning TLUD-ND.
>
> I think you have done exactly that. Good on you.
>
> There is no misdirection at all here. You are past the
> verge of changing the stove’s superior performance in
> order to get a better rating on an invalid metric. It is
> that simple. Don’t get sucked into that trap. When you are
> getting results as good as you are, there are new
> opportunities to go wrong.
>
> The only ‘misdirection’ has been supplied for years by
> test methods that guided people to edit their stoves to
> meet spurious requirements that did not bear directly on
> performance, or worse, actually penalised stoves for their
> superior performance. A good example is attached.
>
> This is not something new in the stove community. Here is
> a quote from the attached Aprovecho document from 2003:
>
> /“Why was the good advice, by established experts in the
> field, represented in the VITA International Standard
> test, the result of several well funded international
> conferences, obscure in 2003? Both the Indian and Chinese
> governments developed tests of their own widening the
> scope of PHU to include power, rate of evaporation, time.
> Visser (2003) published a version of a water boiling test
> based on efficiency and appropriate power for boiling and
> simmering. What motivated this parallel activity? Why
> isn’t the VITA test in more general use?”/
>
> One reason the VITA test was not more popular was it had
> several conceptual errors and a few really poor metrics
> that gave mis-directing outputs. One is the efficiency of
> simmering, another is the concept of specific fuel
> consumption for simmering. Another was the idea of an
> ‘average efficiency’ meaning an ‘average thermal
> efficiency’. I believe from my research that the specific
> fuel consumption for simmering and the average efficiency
> were both introduced by Baldwin in 1986 or so, before his
> book came out. Neither are acceptable metrics.
>
> The document refers to the VITA test the ‘international
> standard’ which is not supported by the evidence. Three or
> four minor parties agreed to it and it was never used by
> the major markets in India and China. Even Eindhoven
> University didn’t use it and they were a party to drafting
> it. India pretty much adopted the minority position taken
> by KK Prasad from Eindhoven and built that into their 1991
> test. The Chinese test from that era was very similar.
> India, interestingly, produced a list of 28 standard sizes
> of cooking pot which is a record, I believe!
>
> The long-forgotten organisation Bois de Feu had a clear
> understanding of these issues and had a test method in
> 1982 that didn’t have these problems. They treated the
> simmering phase very carefully (and differently). Prasad
> (and Visser who was his student) developed multiple test
> methods over the years. Piet Visser and I created one in
> Malawi in about 2007 which later evolved into the ProBEC
> Test for heat transfer efficiency which is now a SeTAR
> SOP, currently v1.05 (SeTAR is an independently managed
> continuation of the 13 year long GIZ/ProBEC project). It
> doesn’t really predict performance, it gives a real-time
> heat transfer efficiency report under varying conditions.
> It is very easy to perform and it supports pot-swapping,
> similar to the Indian protocol.
>
> So, ladies and gentlemen, there are no Tier 4 stoves. That
> achievement will have to wait for the development of
> appropriate, valid low power metrics and one will need an
> equipment set capable of quantifying the result.
>
> Kirk: don’t be bamboozled. You are doing good work.
> Nothing is perfectly correct. Independent investigation of
> truth is still required.
>
> Best wishes
>
> Crispin
>
> All,
>
> With the support of Aprovecho Research Center, I (actually
> we) have developed a very good, clean burning TLUD-ND.
> This is real and proven and no amount of misdirection can
> change that. It will be at Aprovecho for stove camp for
> all to examine, and I will be giving a presentation on how
> it burns so clean.
>
> Respectfully,
>
> Kirk
>
> Santa Rosa, CA. USA
>
> ------------------------------------------------------------------------
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