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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 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><div><div><p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:#1F497D'>></span></b>But if the secondary air is hot as it enters the burner and if there is not too much of it,<br>should there not be a relatively high flame temperature from such a blue flame?<br><br><span style='color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>There <i>can</i> be a high temperature. That does not mean it <i>will</i> be, of course. The greatest enemy of temperature is excess air which directly impacts heat transfer efficiency. The heat transfer efficiency of a crummy stove (one no better than an open fire) can be tripled by perfecting the excess air alone, with no change in combustion efficiency.<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'>In the case of your present stove and the central fire prototype you should test it with a pot on, because it will be very different. In fact the flame temperature is not a particularly good measure of a stove because if it is really hot in one spot, and cool 15mm away from it, there is nothing one can know about how it will perform. As a thermocouple in a flame is only an indicator, not a meaure of flame temperature, it rapidly becomes an academic exercise.<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'>Something helpful is the temperature of the gases just after the flame finished burning, and at the gas exit where the gases move into the open air away from the pot (at the exit point with no ambient air diluting it). That is also a good place to measure the excess air and CO/CO<sub>2</sub> ratio because from those number you can calculate the system’s heat transfer efficiency and CO mass emitted without using a hood.<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></div></div></div></body></html>