Dear Marc-Antoine Pare, Thank you for sharing this online tool. It is quite useful to get the estimate overroll thermal efficiency, like a simplified version of spreadsheet. But after I entered the data, it was not shown in the later cells and there was no calculation or results produced, maybe it did not work in my computer. In the eyes of most Chinese experts, the WBT protocol is a lab based, complicated, and cumbersome testing protocol instead of a quick-and-dirty test for the field. I am not totally agree with them, but I have to say, compared with WBT, the Chinese protocol is much more simply and "dirty". There are two concerns about this tool, the amount of water evaporated and the charcoal produced in the test were both omitted. For the water evaporated, the lid can reduce the water evaporated, but that part of energy could not omitted from the Energy Absorbed. 3 L water in the 28 cm diameter pot with lid is heated by electrical stove (1550±30 W) from 22.2 C to about 95 C in about 19 min, the water evaporated is 14 grams which is 14*2260=31640 J. If the temp. rise to boiling, the water evaporated will be more. For the charcoal produced, there would be not that much charcoal left in the rocket type stove, most of the time less than 10 g. But for the TLUD stove, it is a lot. Sometimes the mass fraction is up to 30% of the initial amount of fuel (pellet fuel with moisture of 5%). The difference of the overall thermal efficiency will be more than 10%. The online tool is a good idea. In the situation that estimated results are enough during the evaluation, the spreadsheet with lots of options is too much. Actually during my data process, I build my own spreadsheet with simple equations to get thermal efficiency. Best wishes --
Huangfu Yibo Master degree student Beijing University of Chemical Technology (BUCT) Biomass Energy and Environmental Engineering Research Center No.15, North 3rd Ring East Road, Chaoyang District, Beijing 100029 Tel: 18810621934 At 2013-11-21 13:25:41,"Marc-Antoine Pare" <[email protected]> wrote: Hi everyone, I've just published an online tool for simple water boiling tests: http://smallredtile.com/stove/wbt-buddy/ This is a sort of experiment, so let me know what you think. Is it useful? What would make it more useful? Did I make any mistakes in the model? I was driving at a few things with the experiment. Is it possible to make the Water Boiling Test calculation simpler and easier to follow? Can we make the steps of the calculation more visible? (to help newcomers, to help identify problems with the calculation) I find that, even with an engineering background, the WBT Excel sheet is not easy to use. The equation for finding thermal efficiency is buried in one cell and looks like this: =IF(W26=0,0,(4.186*SUM((W12-$N15)*(AA8-W8),(W13-$N16)*(AA9-W9),(W14-$N17)*(AA10-W10),(W15-$N18)*(AA11-W11))+2260*W27)/(W26*$E20)) Also, some of the steps of the calculation (moisture content, char energy content) aren't necessary for many use-cases of the WBT. For example, if I'm trying out a new design, all I want to know if the general range of efficiency: 10-20%, 40-50%, etc. I think there may be some benefit to emphasizing that the WBT is an estimate. Wasn't it originally designed as a quick-and-dirty test for the field? So, I simplified the engineering model, tried to build a user friendly interface, and laid out the step of the calculation as clearly as I could. I think that I'm going to build something for TLUDs next. So do send me any suggestions for this right away, if you like. marc
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