Crispin In your three-sentence final paragraph, the first two sentences seem to contradict each other.
Can you give an example of a metric which is invalidated? Ron On May 7, 2013, at 1:35 PM, "Crispin Pemberton-Pigott" <[email protected]> wrote: > Dear Paul > > I think there are excellent questions. I think we have a responsibility to > ‘bring the group’ along on this because there are a lot of people reading the > list who are able to do the calculations. > > It is through these thought experiments that we find out whether or not the > metrics being used are valid (or not). > > It would be more helpful to know the heat transfer efficiency at low power > than that turns out to be invalid. Getting the low power efficiency is easy > to find out, though not by simmering a pot. > > To give you a brief answer regarding heat transfer, the quantity of heat > transferred during simmering is not affected by the volume of water in the > pot (unless there is nearly none left). Heat transfer is a relationship > between the pot and the stove, not what is in the pot. This fact invalidates > several WBT metrics. > > Regards > Crispin > > > > > From: Paul Anderson [mailto:[email protected]] > Sent: Tuesday, May 07, 2013 12:39 PM > To: Discussion of biomass cooking stoves > Cc: Crispin Pemberton-Pigott; Jim Jetter; Tami bond > Subject: Re: [Stoves] Conceptioal Errors and possible pitfals. > > Dear all, > > Further thoughts about just one of Crispin's examples below: > > 3. How about giving us ONE paragraph in 4.2.2 to look at - and with > > especially new language on how you would change that paragraph? Even if > > that has to be a year or two from now. > > Crispin wrote: > > How is this: > > I give you 5 litres of water in a pot and ask you to bring it to a boil. > > You put it in a fire and bring it to what we agree is ‘a boil’ by which time > 100 cc has evaporated. > > I ask you how many litres of water you have just boiled. > > What is your answer? > > That is an example of a conceptual difference. The WBT says you boiled 4.9. > An engineering will say you boiled 5.0. > > Is this cognitive dissonance or conceptual error? > > And take this to the simmer stage, which typically is for 45 minutes in the > WBT. If the pot has not lid (and it does not have a lid in the official > testing), additional water will be boiled away. Assume two cases, one with > a very low fire and one with very high fire (a common result of not having > much of a turn-down ratio on powerful stoves). > > In the low fire case, assume that there are still 4.5 liters in the pot. > In the high fire case, assume that there are only 3 liters in the pot. > > In the final minutes, the difference in the amount of water in the two pots > is 1.5 liters, which is 33% of 4.5 liters and 50% of 3 liters. So, are you > actually "simmering" 5 or 4.5 or 3 liters? And how much actual ENERGY is > needed to accomplish that task if the amounts of water are so different? > > And which stove has the "advantage" (that is, looks the best in the reported > results) depending on what number(s) are used in the analyses? (Will > someone please do the math using the formulae, just changing the number of > liters from 5 to 4.5 to 3 so that we can see the impact.) This is > hypothetical, but educational. > > I think that this is the type of stuff that Erin was mentioning about issues > not well understood. If you have the answer WITHOUT doing the 6 > calculations, then you are quite special. But I will still ask you to give > me the numbers. > > Topic Stove type > Results 5 L 4.5 L 3 L Comments: > (L or H heat) > > Results of > A. Efficiency??? for LOW heat stove: ________ ______ > _______ _______.......... > > B. dito HIGH > ________ ______ _______ _______.......... > > > C. Result ??? for LOW heat stove: ________ > ______ _______ _______.......... > > D. dito HIGH > ________ ______ _______ _______.......... > > And more??? > > Sorry, I do not know the answers, and I am not qualified to do the > calculations. But I would like to know the results. Maybe more than one > "result" is correct and should be reported in the results of the stove > testing? If this is meaningless, I want to know why. > > Note: If the results of the above are NOT of interest to you, then perhaps > none of the discussion about testing protocols is of interest to you. All > of us will be grateful for these types of questions being resolved. > > Paul > > > _______________________________________________ > Stoves mailing list > > to Send a Message to the list, use the email address > [email protected] > > to UNSUBSCRIBE or Change your List Settings use the web page > http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org > > for more Biomass Cooking Stoves, News and Information see our web site: > http://stoves.bioenergylists.org/ >
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