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Dear Tami</div>
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I think it is worth my pointing out that when the WBT 'thermal efficiency' metric was created by VITA it was not called 'thermal efficiency'. The most obvious reason for not giving it that label is that it doesn't calculate the thermal efficiency. </div>
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It was called the 'Percentage Heat Utilized'. PHU was in common use until the 2000's and I used the term myself in discussions on this list. </div>
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Two mistakes were made following the change in the name: one was changing the name to a standard term without changing the formulaý to match, and the second was to apply it to the calculation of relative fuel consumption. Because it is not the energy or thermal
efficiency, it gives the wrong answer in the relative fuel consumption calculation. </div>
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The term 'thermal efficiency' has numerous definitions but tends towards the heat transfer efficiency compensated for lossesý. That makes it harder to use because it has to be accompanied by a carefully worded definition. 'energy efficiency' is widely used
to mean the system efficiency or overall efficiency. Good examples are solar cookers and vehicles with regenerative brakes. </div>
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The problem arguing for the WBT 'thermal efficiency' metric is the deduction of only part of the residual char ýinstead of all of it. The 'recoverable' portion in not the whole of the mechanical loss and the result is a non-standard term with no standard name.
It is certainly not 'thermal efficiency' which is common parlance would require deducting all energy in the solid residue. The 'recoverable' portion of it is arbitrary and subject to interpretation. </div>
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We have been discussing this in a sort of 'purist' form. The actual formula used in the WBT considers the mass of char to include the mass of ash accumulated to that point and treats it as if it has char with an energy value of 29 MJ/kg. ýThe WBT protocol does
not require separation of the char as proposed by Ron, but makes the error of considering ash to be char. Separating char is creates a separate error. </div>
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It seems the advocates have not examined how these formulae work. The original claim is that the metric represents the cooking efficiencyý. As Prof Lloyd has pointed out, that is determined by work done divided by energy fed into the system. </div>
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Regards </div>
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Crispin </div>
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<div class="">Dr. Bond, cc List and Dr. Chiang</div>
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<div class=""><span class="Apple-tab-span" style="white-space:pre"></span>1. Because I know you are looking for engineering precedence on the main equation in our dialog, I should have provided the cites for the two books I mentioned in last night’s response,
when I said:</div>
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<div class=""><b class=""><i class=""> ‘As I searched (more coming on the search) I found two (Google- free) boiler books from around 1910 that have this equation. "</i></b></div>
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<div class=""><span class="Apple-tab-span" style="white-space:pre"></span>My search was for “subtract efficiency efficiencies denominator"</div>
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<div class="">They are: </div>
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<div class="">a. On 3 pages as a part of a USGS annual document from 1907. One can move around beyond the 3 pages that show up, without downloading the whole several hundred pages. My search was for “denominator”; one seems to be able to search for other
terms:</div>
<div class=""> <a href="https://books.google.com/books?id=tTRGAQAAMAAJ&pg=RA1-PA137&lpg=RA1-PA137&dq=subtract+efficiency+efficiencies+denominator&source=bl&ots=5C3AgUSOP-&sig=440wVsdeLXYIxMvjrMRPHBSnklw&hl=en&sa=X&ved=0ahUKEwisqa3At4_SAhVolFQKHeapC5Y4ChDoAQghMAI#v=onepage&q= denominator&f=false" class="">https://books.google.com/books?id=tTRGAQAAMAAJ&pg=RA1-PA137&lpg=RA1-PA137&dq=subtract+efficiency+efficiencies+denominator&source=bl&ots=5C3AgUSOP-&sig=440wVsdeLXYIxMvjrMRPHBSnklw&hl=en&sa=X&ved=0ahUKEwisqa3At4_SAhVolFQKHeapC5Y4ChDoAQghMAI#v=onepage&q=%20denominator&f=false</a></div>
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<div class="">b. A book from 1915 <span class="" style="color:rgb(51,51,51); font-family:Arial,sans-serif; font-size:11.869px; orphans:2; widows:2; background-color:rgb(255,255,255)">Engineering Thermodynamics </span><span class="" style="color:rgb(51,51,51); font-family:Arial,sans-serif; font-size:8.9557px; orphans:2; widows:2; background-color:rgb(255,255,255)">By
James Ambrose Moyer, James Park Calderwood </span>Again a page with the idea of subtraction shows up</div>
<div class=""> <a href="https://books.google.com/books?id=fElDAAAAIAAJ&pg=PA144&lpg=PA144&dq=subtract+efficiency+efficiencies+denominator&source=bl&ots=A-tYLgv0zK&sig=ue-L88klNbAhsYOk4bqaJELW0IA&hl=en&sa=X&ved=0ahUKEwisqa3At4_SAhVolFQKHeapC5Y4ChDoAQg1MAk#v=onepage&q=subtract efficiency efficiencies denominator&f=false" class="">https://books.google.com/books?id=fElDAAAAIAAJ&pg=PA144&lpg=PA144&dq=subtract+efficiency+efficiencies+denominator&source=bl&ots=A-tYLgv0zK&sig=ue-L88klNbAhsYOk4bqaJELW0IA&hl=en&sa=X&ved=0ahUKEwisqa3At4_SAhVolFQKHeapC5Y4ChDoAQg1MAk#v=onepage&q=subtract%20efficiency%20efficiencies%20denominator&f=false</a></div>
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<div class=""><span class="Apple-tab-span" style="white-space:pre"></span>My problem with these two is that I think you are looking for examples from other fields. I have no doubt there are dozens of other books using this equation in the succeeding century.</div>
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<div class=""><span class="Apple-tab-span" style="white-space:pre"></span>2. Not mentioned last night, but I also found these: </div>
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<div class="">a. <a href="https://www.ncbi.nlm.nih.gov/pubmed/15109753" class="">https://www.ncbi.nlm.nih.gov/pubmed/15109753</a> on wheel chair efficiencies (2004), where the title says: </div>
<h1 class="articleTitle" style="margin:0px 0px 15px; font-weight:normal; color:rgb(51,51,51); font-size:24px; line-height:normal; font-family:Georgia,serif; orphans:2; widows:2; background-color:rgb(255,255,255)">
Mechanical efficiency during hand–rim wheelchair propulsion: effects of base-line subtraction and power output</h1>
<div class=""> I didn’t choose to pay to buy this one, but there is a (small?) chance it might have what we are looking for, given the word “subtraction”.. </div>
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<div class="">b). Again, not willing to buy a book, but the idea of subtraction in the denominator seems to be present in the signal processing world</div>
<div class=""><a href="https://books.google.com/books?id=6invBwAAQBAJ&pg=PA224&lpg=PA224&dq=subtract+efficiency+efficiencies+denominator&source=bl&ots=HYgiFLLTi6&sig=uJxsCjDgj21PNaHdwfG45HRlKZc&hl=en&sa=X&ved=0ahUKEwisqa3At4_SAhVolFQKHeapC5Y4ChDoAQgfMAE#v=onepage&q=subtract efficiency efficiencies denominator&f=false" class="">https://books.google.com/books?id=6invBwAAQBAJ&pg=PA224&lpg=PA224&dq=subtract+efficiency+efficiencies+denominator&source=bl&ots=HYgiFLLTi6&sig=uJxsCjDgj21PNaHdwfG45HRlKZc&hl=en&sa=X&ved=0ahUKEwisqa3At4_SAhVolFQKHeapC5Y4ChDoAQgfMAE#v=onepage&q=subtract%20efficiency%20efficiencies%20denominator&f=false</a></div>
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<div class="" style="orphans:2; widows:2">c. Also an expensive text (<span class="" style="orphans:2; widows:2; background-color:rgb(255,255,255)"><font color="#333333" face="Arial, sans-serif" class=""><span class="" style="font-size:12px">Exergy</span><span class="" style="font-size:11.869px">:
Energy, Environment and Sustainable Development; </span></font></span><span class="" style="color:rgb(51,51,51); font-family:Arial,sans-serif; font-size:8.9557px; orphans:2; widows:2; background-color:rgb(255,255,255)">By Ibrahim Dincer, Marc A. Rosen)</span></div>
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<div class="">where there is a subtraction in the denominator (p 253); the University of Illinois may still be a main resource on Exergy (with an x - not Energy)</div>
<div class=""> <a href="https://books.google.com/books?id=FrUolHxhGVYC&pg=PA253&lpg=PA253&dq=subtract+efficiency+efficiencies+denominator&source=bl&ots=9Iml913d48&sig=vYovGRUnGhhhl1HrmwqR15xKghc&hl=en&sa=X&ved=0ahUKEwisqa3At4_SAhVolFQKHeapC5Y4ChDoAQgxMAg#v=onepage&q=subtract efficiency efficiencies denominator&f=false" class="">https://books.google.com/books?id=FrUolHxhGVYC&pg=PA253&lpg=PA253&dq=subtract+efficiency+efficiencies+denominator&source=bl&ots=9Iml913d48&sig=vYovGRUnGhhhl1HrmwqR15xKghc&hl=en&sa=X&ved=0ahUKEwisqa3At4_SAhVolFQKHeapC5Y4ChDoAQgxMAg#v=onepage&q=subtract%20efficiency%20efficiencies%20denominator&f=false</a></div>
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<div class="">3. I also found some possible benefit on talk on the differences between “efficiency” and “effectiveness” - with at least one author claiming the latter is to be preferred. Maybe the “denominator equation” is effectiveness. I do support the
concept that it is accurately saying what the efficiency would have been without char. I believe the actual inefficiency giving what I have called e1 and e2 is NOT as bad as this equation implies for the no-char case. Stated alternatively, a char-making
stove is <u class=""><b class="">inherently</b></u> less wasteful than the no-char case.</div>
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<div class="">So, Tami, I am not yet happy with any of these. I am looking to justify the use of the “denominator equation” in a slightly different manner (still using the “denominator equation” - but maybe this above will help a tad). And possibly the
above will bring others into this WBA search/justification topic for Tier allocation.</div>
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<div class="">Again thanks for putting so much time into this.</div>
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<div class="">Ron</div>
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<div class="">On Feb 14, 2017, at 11:52 PM, Ronal W. Larson <<a href="mailto:rongretlarson@comcast.net" class="">rongretlarson@comcast.net</a>> wrote:</div>
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<div class="">Drs. Chiang and Bond, cc List</div>
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<div class=""><span class="Apple-tab-span" style="white-space:pre"></span>I have had a lousy day ridding my computer of a virus Among other things, I could not download this until a few hours ago: <a href="http://www.pciaonline.org/files/ISO-IWA-Cookstoves.pdf" class="">http://www.pciaonline.org/files/ISO-IWA-Cookstoves.pdf</a>.
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<div><span class="Apple-tab-span" style="white-space:pre"></span><snip the rest to save bandwidth></div>
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