[Stoves] Examples of results of simmer efficiency Re: [Ethos] Additional presentations at ETHOS 2015
Paul Anderson
psanders at ilstu.edu
Mon Feb 16 01:09:20 CST 2015
Kirk,
There are two separate issues. One is the temperature of the water,
and the other is the amount of evaporation (steam) caused by the heat.
The temperature cannot go above the local boiling point (we say 100 C
for our discussion). Physically impossible.
And the test procedures do not allow the water temperature to be less
than 6 deg C lower than BP. So there is relatively little temperature
variation allowed.
The steam (evaporation) issues can be discussed separately, with some
stoves evaporating more water than do others. That is a measurable
variable that may or may not need to be in the calculations. But
measured water temperature is held quite stable.
Paul
Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
Email: psanders at ilstu.edu
Skype: paultlud Phone: +1-309-452-7072
Website: www.drtlud.com
On 2/15/2015 11:23 PM, kgharris wrote:
> Paul,
> I respectfully disagree. Two stoves are burning at the same fire
> power and one has better heat transfer to the pot. The water in
> the better heat transfer stove will be hotter because less heat is
> lost, producing more steam and lower scores. The better heat
> transfer stove will have to be turned down to a lower power level to
> keep the pot the same temperature as the worse heat transfer stove.
> That is the whole reason for improving heat transfer into the pot, to
> allow a lower power level for the same cooking ability.
> The thing which has been shown about the WB simmering test is that it
> does not work if each stove has it's own seperate simmering
> temperature and steam production. It will work if all stoves
> are adjusted to a fire power that produces the same simmering
> temperature and steam production for all tests. Then the lower a
> stoves fire power and fuel use the better the score, and no punishment
> for a more efficient stove. Keeping the simmering temperature and
> steam production the same for all stove tests allows meaningful
> comparisons between stoves and good protocol for tier ratings. The
> results of keeping the temperature the same will help the stove
> designer because different designs can then be compared with each
> other on equal basis, and the more efficient design, balanced with
> cost, can be chosen.
> I must agree with Dean Still on this.
> Kirk Harris
>
> ----- Original Message -----
> *From:* Paul Anderson <mailto:psanders at ilstu.edu>
> *To:* Discussion of biomass cooking stoves
> <mailto:stoves at lists.bioenergylists.org>
> *Sent:* Sunday, February 15, 2015 7:30 PM
> *Subject:* Re: [Stoves] Examples of results of simmer efficiency
> Re: [Ethos] Additional presentations at ETHOS 2015
>
> Kirk,
>
> Your comment contains one incorrect statement:
>> The stove which gets more transfer of the heat into the pot may
>> cause more steam if it cannot turn down to a lower power level
>> than the lesser stove, but that means that the two simmering
>> temperatures are different.
> Essentially there is only one simmering temperature that is
> allowed, which is to be never more than 6 deg C lower than the
> boiling point. If local boiling point is 100 C, then never less
> than 94 C, and probably best to keep the temperature of the water
> at about 97 C.
>
> But even a roaring fire cannot raise the temperature above the
> boiling point. So the difference in the TEMPERATURE OF THE WATER
> is of little consequence, being about 3 deg C. And remember that
> _the purpose or objective of simmering_ is to maintain the
> temperature. The purpose is NOT to minimize the amount of
> evaporated water, which is only a poor reflection of how much fuel
> is used.
>
> Please also see my next message, that is addressed to Phillip and
> Dean who have exchanged messages recently.
>
> Paul
>
> Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
> Email:psanders at ilstu.edu
> Skype: paultlud Phone: +1-309-452-7072
> Website:www.drtlud.com
>
> On 2/15/2015 6:41 PM, kgharris wrote:
>> All,
>> I am not understanding why the WBT is invalid if the simmer
>> temperature is held the same for all stoves. The stove which
>> gets more transfer of the heat into the pot may cause more steam
>> if it cannot turn down to a lower power level than the lesser
>> stove, but that means that the two simmering temperatures are
>> different. Dean is talking about the test simmering
>> temperature being the same for all stoves. The stove that gets
>> more heat transfer into the pot will need more turn-down than the
>> lesser stove in order to simmer at the pre-choosen test
>> temperature. That is the whole reason for improving the heat
>> transfer into the food. To be able to use lower power levels,
>> less fuel, and fewer emmissions to cook with. The two
>> capabilities need to evolve together, and both are improvements
>> which can enhance a good field usable stove. Also simplicity of
>> construction and ease of use are important qualities which need
>> consideration and perhaps some kind of metrics for measurements.
>> Kirk Harris
>> Santa Rosa, CA. USA
>> ----- Original Message -----
>>
>> *From:* Dean Still <mailto:deankstill at gmail.com>
>> *To:* Discussion of biomass cooking stoves
>> <mailto:stoves at lists.bioenergylists.org>
>> *Sent:* Sunday, February 15, 2015 1:35 PM
>> *Subject:* Re: [Stoves] Examples of results of simmer
>> efficiency Re: [Ethos] Additional presentations at ETHOS 2015
>>
>> Dear Philip,
>>
>> The Low Power test works well when the fuel use is normalized
>> using a set simmering temperature.
>>
>> Sam and I are writing up some characteristics of the WBT and
>> I'll post the paper here. Lots of work to do and I look
>> forward to our continued collaboration.
>>
>> Best,
>>
>> Dean
>>
>> On Sun, Feb 15, 2015 at 11:43 AM, Philip Lloyd
>> <plloyd at mweb.co.za <mailto:plloyd at mweb.co.za>> wrote:
>>
>> Dear Dean
>>
>> Crispin said it well:
>> “The three low power metrics are invalid. The variables
>> selected are inappropriately chosen. The calculated
>> results are misleading and contrary to any claim [that]
>> they provide guidance for product development or
>> selection. We have to move on.”
>>
>> I have looked at the simmering metrics in WBT 4.3.2 and
>> can only concur. That is why I do not think we should
>> waste much more time arguing about them – they are
>> fundamentally wrong. Yes, stove designers need to be
>> concerned with simmering and turndown; no, the WBT
>> simmering metrics do not provide them with guidance, and
>> can be positively misleading, which is worse.
>>
>> Kind regards
>>
>> Philip Lloyd
>>
>> *From:*Stoves
>> [mailto:stoves-bounces at lists.bioenergylists.org
>> <mailto:stoves-bounces at lists.bioenergylists.org>] *On
>> Behalf Of *Dean Still
>> *Sent:* 15 February 2015 06:38
>> *To:* Discussion of biomass cooking stoves
>> *Subject:* Re: [Stoves] Examples of results of simmer
>> efficiency Re: [Ethos] Additional presentations at ETHOS 2015
>>
>> Dear Prof Loyd,
>>
>> As I pointed out, when the stoves do the same work (hold
>> the water at 97 C, for example) the stove with greater
>> heat transfer efficiency scores better. Simmering tests
>> are important and simmering is an important part of cooking.
>>
>> The ISO process is creating new history and approaches to
>> old problems. Whatever emerges will certainly be
>> defensible as the new approaches are forged by consensus.
>>
>> Best,
>>
>> Dean
>>
>> On Sun, Feb 15, 2015 at 12:58 AM, Philip Lloyd
>> <plloyd at mweb.co.za <mailto:plloyd at mweb.co.za>> wrote:
>>
>> I am concerned that this is turning into a very fruitless
>> discussion.
>>
>> On fundamental grounds the simmering test does not
>> provide anything meaningful. Crispin has demonstrated
>> that rigorously, and others have pointed out that the
>> test can score an efficient stove poorly and an
>> inefficient stove well, so it does not provide any useful
>> measure. To go on defending the indefensible does not
>> make sense, even if it did accentuate the need for
>> turndown – but that need was always there, it was not the
>> product of the WBT.
>>
>> We need defensible measures of stove performance. Can we
>> please turn our attention to developing those, and leave
>> the indefensible to history?
>>
>> Prof Philip Lloyd
>>
>> Energy Institute
>>
>> Cape Peninsula University of Technology
>>
>> PO Box 652, Cape Town 8000
>>
>> Tel:021 460 4216
>>
>> Fax:021 460 3828
>>
>> Cell: 083 441 5247
>>
>> *From:*Stoves
>> [mailto:stoves-bounces at lists.bioenergylists.org
>> <mailto:stoves-bounces at lists.bioenergylists.org>] *On
>> Behalf Of *Paul Anderson
>> *Sent:* 15 February 2015 02:26
>> *To:* Discussion of biomass cooking stoves
>> *Subject:* Re: [Stoves] Examples of results of simmer
>> efficiency Re: [Ethos] Additional presentations at ETHOS 2015
>>
>> Dear Dean, my reply is below:
>>
>> Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
>>
>> Email:psanders at ilstu.edu <mailto:psanders at ilstu.edu>
>>
>> Skype: paultlud Phone:+1-309-452-7072 <tel:%2B1-309-452-7072>
>>
>> Website:www.drtlud.com <http://www.drtlud.com>
>>
>> On 2/14/2015 1:06 PM, Dean Still wrote:
>>
>> Dear Paul,
>>
>> To do well on the Low Power Specific Consumption
>> metrics the stove has to have a good Turn Down Ratio.
>> In other words, the stove has to have high power and
>> low power.
>>
>> I totally agree with this. But it is not the whole
>> story of LPSC. Other factors influence LPSC, especially
>> concerning the measurement of the variables that are used
>> to make the calculation. These can include the
>> insulation of the pot (incl. skirts), lid on pot, pot
>> characteristics such as size, quantity of water in the
>> pot at the start, and at the finish.
>>
>> Specific Consumption is based on how much energy was used
>> to create simmered water.
>>
>> Simmered water is not created. It was already hot at
>> the start of the simmer phase of testing. We are
>> interested in how much energy is used to MAINTAIN the
>> required temperature near boiling, but preferable about 3
>> degrees C lower than that boiling temperature. In fact,
>> a super-insulative pot could need barely a flicker of a
>> flame, and therefore even a well turned-down stove could
>> cause the water to boil and evaporate.
>>
>> If the stove only operates at high power there is more
>> steam made and [at the end of testing] less simmered
>> water remains....
>>
>> that is true. but continue.
>>
>> ..... so energy was used to create less product.
>>
>> Stove simmering is not creating a product. It is
>> maintaining a temperature. The steam that is driven off
>> does not represent loss of "product" which should be
>> understood to be "cooked food" (and not meaning water
>> that can be added to the pot by any attentive cook in a
>> household.)
>>
>> I like Specific Consumption because it forces stove
>> designers to make stoves that simmer successfully, not
>> just boil water.
>>
>> I agree. But the measurement procedures need to
>> accurately document the ability to have that strong
>> turn-down ratio, without calculations that can yield
>> ambiguous or mis-leading results.
>>
>> For example, new TLUDs are better stoves because they
>> have both high power and low power. In my opinion, the
>> WBT 4.2.3 helped to create these more successful TLUDs.
>>
>> The cause-and-effect relationship is not totally clear.
>> We have wanted turn-down capabilities in TLUDs for many
>> years.
>>
>> As Sam says, we are working on a paper showing
>> characteristics of the WBT 4.2.3 for the ISO work.
>> Knowing the characteristics lets folks evolve a perfect
>> test.
>>
>> I question the above wording to "evolve a perfect test"
>> (which is a test run, not the test procedures.) Maybe
>> the statement should be that "knowing the characteristics
>> let's folks operate their stoves in special ways to
>> obtain superior results that are not realistic for
>> average users." OR "... let's folks 'game the metrics' to
>> present 'perfected' test-results BASED ON OPERATIONAL
>> PROCEDURES AND NOT ON IMPROVEMENTS TO THE STOVES
>> THEMSELVES."
>>
>> OR it could be that flawed protocols /procedures (such as
>> dividing by the volume of remaining water after
>> simmering) can yield numerical results that are
>> questionable and perhaps disadvantageous to the
>> development of clean cookstoves.
>>
>> Sam is doing great work as he crunches all the data....
>>
>> absolutely. But we are questioning if the numbers are
>> as valid and useful as claimed.
>>
>> and gives ISO real numbers to work with in their
>> discussions.
>>
>>
>> Concluding statement: The topic of Low Power Specific
>> Consumption is too important to just brush aside the
>> stated issues. More "expert testimony" would be useful,
>> including a mathematical analysis of the impact of the
>> parts of the calculations.
>>
>> Paul
>>
>>
>> Best,
>>
>> Dean
>>
>> On Sat, Feb 14, 2015 at 8:18 AM, Paul Anderson
>> <psanders at ilstu.edu <mailto:psanders at ilstu.edu>> wrote:
>>
>> Dear Tom H., and to all who are interested in
>> proper testing of stoves.
>>
>> Your reply about your experiences is helpful. Sounds like
>> you had qualified testing center do the testing, in
>> accordance with the procedures that Crispin is
>> questioning. Please send to me the full details. Could
>> be off-list, but this is sufficiently important that we
>> will want the full results known.
>>
>> I have a specific case of official testing of one of my
>> stoves with unfavorable results for Low-Heat Efficiency
>> (simmering). I will add that into the list of examples
>> and provide the details very soon.
>>
>> I invite anyone else who has something to report about
>> simmering efficiency to also send details of their
>> experiences, either favorable or unfavorable or neutral.
>>
>> The examination of the questionable methods about simmer
>> efficiency might take some days, maybe weeks. But not the
>> months or years that this debate has been "simmering".
>>
>> Remember: A testing center that properly conducts
>> testing using an endorsed but possibly flawed procedure
>> is NOT a culprit. The culprit is the testing protocols,
>> _IF found to be faulty. _And we hope that the testing
>> center people (employees and leaders) who understand the
>> technical aspects of the calculations will be among those
>> who can help resolve these serious issues.
>>
>> Even those who developed protocols that are eventually
>> shown to be faulty are not culprits. Mistakes can be
>> made. However, the culprits can include those who
>> advocate a protocol that he or she knows (or reasonably
>> suspects) to be faulty.
>>
>> Paul
>>
>> Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
>>
>> Email:psanders at ilstu.edu <mailto:psanders at ilstu.edu>
>>
>> Skype: paultlud Phone:+1-309-452-7072 <tel:%2B1-309-452-7072>
>>
>> Website:www.drtlud.com <http://www.drtlud.com>
>>
>>
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