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</o:shapelayout></xml><![endif]--></head><body lang=EN-CA link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Dear Alexis and Paul<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Thanks so much for the very open discussion and open design of the burners. Alexis, when we met in Thailand you mentioned that you have switched to a premixed flame and if you recall we did talk a bit about the top end of the version of the stove you demonstrated.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Is it correct that you are now using a premixed flame? I have been in extensive conversation with Paul O about the burner for some time and it seems at present to be a blend of premixing with secondary air and as Paul says, some tertiary air for the final burnout.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>The difference in performance that Paul mentioned and which got some much discussion going about heat transfer from the hot dome could have at least three quite different origins and there is a lot of merit in tracking down the difference. The first might be that the structure under the pot on Paul’s present configuration is much more closed than the one I saw in Thailand. That could account for all the difference in the boiling time. A second possibility is the reduction in excess air either through the burner where flames are present or between the flames and the final departure of the pot and stove structure, by which I mean the outer ring. Until the hot gases leave the pot and vent into the room, the air present in that gas stream is technically part of the combustor. If there is a lot of cold air entering the region under the pot, then it is counted as excess air in the heat exchanger.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Paul, thanks for putting the pictures of the development work you are doing. It is helpful for those who would like to work on stoves with minimal equipment to see how things work and what has been tried. It saves a lot of reinventing.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>With regard to the heat transfer from a radiant dome, Marc has been doing some calculations which I hope he will post here when he is confident in the method. That should settle the question as to whether or not a large increase in performance can be obtained by changing hot, relatively non-IR radiant gas into IR emitted from a wide gauze surface.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>It is well worth remembering that because a flame is pale blue in the visible range, that does not tell us what it is emitting in the IR which is invisible to human eyes. Looking through a translucent flame is not really a measure of emissions of heat. If you point an IR gun at a flame it will register a high temperature, even if it is as inaccurate as an unshielded thermocouple.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>I agree with the others that the discussion about heat transfer has been a good exploration of the subject. I appeal to Marc not to hide his light under a bushel. These discussion also need numbers and methods so the reality of things becomes widespread.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Regards<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Crispin<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>++++++</span></b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'><o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;margin-bottom:12.0pt'>Alexis,<br><br>Here is the drawing of your burner:<br><a href="http://dl.dropbox.com/u/22013094/150%20Gasifier/Drawings/005.pdf">http://dl.dropbox.com/u/22013094/150%20Gasifier/Drawings/005.pdf</a><br>Here is the drawing of the burner housing:<br><a href="http://dl.dropbox.com/u/22013094/150%20Gasifier/Drawings/006.pdf">http://dl.dropbox.com/u/22013094/150%20Gasifier/Drawings/006.pdf</a><br>The housing is not easy to make without large pressing equipment.<br><br>The housing is placed over the burner.<br>The two parts are welded together at the four points where they touch.<br><a href="http://dl.dropbox.com/u/22013094/150%20Gasifier/Boiling/IMG_1024a.JPG">http://dl.dropbox.com/u/22013094/150%20Gasifier/Boiling/IMG_1024a.JPG</a><br><br>446 stainless, as the drawings suggest, is too expensive.<br>Making both parts in cast iron could be considered.<br>But cast iron normally involves a considerable thickness.<br><br>I foresee a third part that fits above the burner housing.<br>This part is embedded within the counter-top.<br>This third part restrains the flow of excess air, and it shields the flames from wind.<br><br>Thanks.<br>Paul<o:p></o:p></p><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>On Sat, Mar 17, 2012 at 9:16 AM, alexis belonio <<a href="mailto:atbelonio@yahoo.com">atbelonio@yahoo.com</a>> wrote:<o:p></o:p></p></div></div></body></html>