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Crispin,<br>
<br>
Playing with words. FUEL is not the same as ENERGY. You and I
have discussed this before. And I accept that wood that has been
turned into gases and charcoal is no longer wood. But the Char is
still with significant ENERGY, and that is what needs to be stated.<br>
<br>
If CREEC is following the same terminology as the other testing
centers, so be it. The line should be labeled "energy
efficiency." <br>
<br>
You wrote:
<blockquote type="cite">The appropriate metric for that [cooking] is
the 'cooking efficiency', which considers the amount of fuel
needed and the cooking accomplished. </blockquote>
Why would you say FUEL????? We all know that people do not cook
with FUEL. They cook with the ENERGY that comes from the fuel.
TLUD stoves (char making stoves) do not release all of the energy
from the fuel. <br>
<br>
You have not convinced me at all. As I said, "playing with
words." I refer ONLY to the topic of char that needs to be taken
into account.<br>
<br>
And you said that I would agree that knowing "heat transfer
efficiency" woud not be helpful to me. I disagree. It is
certainly useful to know how well a stove gets the heat transferred
into the pot. We add pot skirts, bring the flame closer or further
away, whatever it takes to get improvement. And whether or not a
stove has made charcoal or not is not part of that discussion
because we are talking about energy, not fuel. <br>
<br>
Concerning all of your <u>other </u>contentions about problems
with the WBT, I cerrtainly hope that your arguements are not based
on playing with words. <br>
<br>
Paul<br>
<pre class="moz-signature" cols="72">Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
Email: <a class="moz-txt-link-abbreviated" href="mailto:psanders@ilstu.edu">psanders@ilstu.edu</a>
Skype: paultlud Phone: +1-309-452-7072
Website: <a class="moz-txt-link-abbreviated" href="http://www.drtlud.com">www.drtlud.com</a></pre>
<div class="moz-cite-prefix">On 1/23/2017 7:40 AM, Crispin
Pemberton-Pigott wrote:<br>
</div>
<blockquote
cite="mid:YTOPR01MB0235F370410B99F99A049605B1720@YTOPR01MB0235.CANPRD01.PROD.OUTLOOK.COM"
type="cite">
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Dear Paul</div>
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You are not trying to find the heat transfer efficiency. If you
knew what it was, you will agree it will not help you. </div>
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<br>
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Consider: you have hot gases passing the pot. You quantify (by
subtraction) how much energy is in the hot gases. You determine
how much heat is transferred to the pot. Divide the latter by
the former and you get the heat transfer efficiency. </div>
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<br>
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Now what do you do with the number? That is the metric stove
designers chase to improve. But there are other considerations
for the designer. </div>
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<br>
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The Big Consideration is how much fuel is needed to achieve the
cooking. The appropriate metric for that is the 'cooking
efficiency', which considers the amount of fuel needed and the
cooking accomplished. Not too surprisingly, fuel consumption is
a popular metric to use when selecting a stove to buy, same as
buying a car. </div>
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<br>
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The popular metric name is 'fuel consumption'. If you look at
the bottom of the Quad II test report from CREEC Lab you will
see that is the name of the metric. It says the stove used 636 g
of fuel. But the stove used about 1200 g of fuel! That is not
636. Why? What's going on? Why isn't the dry fuel mass consumed
per test reported as the dry fuel mass consumed? Bit of an
obvious error, eh?</div>
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<br>
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They have reported an imperfectly calculated heat transfer
efficiency as the fuel efficiency. That is what a WBT does, and
why the observed field performance is
<i>always</i><span> worse than the WBT lab test, even if the
cooking in the field exactly matches the test sequence of the
WBT. </span></div>
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<span><br>
</span></div>
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<span>I have previously discussed what that 636 number actually
is, but it certainly is not the mass of dry fuel consumed,
which is what the number is called. Anyone who uses that
number to calculate the relative fuel consumption of two or
more stoves will be misled because it does not represent the
fuel consumption. </span></div>
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<span><br>
</span></div>
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<span>Unfortunately the 'Stove Comparison Chart' uses that
number to report the fuel efficiency. Obviously the ratings
are in error, each by a different amount depending on how much
char they happened to produce that day. This leads to
misunderstandings and mis-belief about what people are getting
and what they paying for. </span></div>
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<span><br>
</span></div>
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<span>Regards </span></div>
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<span>Crispin </span></div>
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<span><br>
</span></div>
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<span><br>
</span></div>
<br>
<div>Crispin,<br>
<br>
I have not yet had time to read your lengthy response to me
(very busy today). But I did read your response to Ron
(below).<br>
<br>
I find part of it to be astonishing.
<blockquote type="cite">
<pre>What I cannot do is subtract anything from the denominator, unless I am trying to determine the heat transfer efficiency, which so far no one has claimed to be trying to do. </pre>
</blockquote>
I certain have been terribly stupid. All along I thought we
were talking about the same thing. Obviously not. I accept
the blame for my lack of precision in my use of terminology.
That is why I am not on the ISO or other technical committees.
Someday (when we have more time) we can put all of the
terminolgy into a list and show how each one is different.<br>
<br>
So, as long as we discuss the "heat transfer efficiency", I now
believe that we three (you, Ron and me) are in complete
agreement.<br>
<br>
Thank you. <br>
<br>
Paul<br>
<br>
<pre class="moz-signature" cols="72">Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
Email: <a moz-do-not-send="true" class="moz-txt-link-abbreviated" href="mailto:psanders@ilstu.edu">psanders@ilstu.edu</a>
Skype: paultlud Phone: +1-309-452-7072
Website: <a moz-do-not-send="true" class="moz-txt-link-abbreviated" href="http://www.drtlud.com">www.drtlud.com</a></pre>
<div class="moz-cite-prefix">On 1/23/2017 1:58 AM, Crispin
Pemberton-Pigott wrote:<br>
</div>
<blockquote type="cite">
<pre>Dear Ron
Nearly everything you ask is answered in the message to Paul
“This is a 2013 EPA webinar (achieved by GACC) devoted to batch stoves - principally char-making.”
The presentations makes a fundamental mistake of making two calculations and calling them both ‘thermal efficiency’. You can’t just go subtracting and adding things willy-nilly and assume that the result has meaning.
The presentation from the EPA takes the incomplete WBT heat transfer efficiency formula (defective because it does not include all the necessary variables) and extends the application of it to claim it is considering the benefit of the energy in the char. It is not.
It is also stated that the energy in the pot cannot be added to the energy in the char! Rubbish! They are both forms of energy, one sensible and the other stored chemical energy. I can added them without even using a calculator. They are both benefits of the operation of the stove, benefits derived from the consumption of the fuel. So is space heating, or operating a TEG to generate electricity. I can easily add all the energy in those benefits and arrive at an overall efficiency for the stove. Or, I can report them individually as if the other benefits were not needed or wanted.
What I cannot do is subtract anything from the denominator, unless I am trying to determine the heat transfer efficiency, which so far no one has claimed to be trying to do. Were I to subtract numbers correctly, I could get the heat transfer efficiency to the TEG, the heat exchange, or the pot. But no one asked for that. They asked for the fuel consumption, the cooking efficiency and Paul want the char energy retention efficiency. No problem. Please see the response to Paul.
Explain to me why you would want the cooking+char production efficiency of 37.5% reported as 16.66%. I look forward to that.
Regards
Crispin
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