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</o:shapelayout></xml><![endif]--></head><body lang=EN-CA link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>Dear Friends<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>This is a classic demonstration of what happens when there is a dwindling fire in a hot stove and suddenly the flame goes out (usually making a lot of smoke).<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='mso-fareast-language:EN-CA'><img width=469 height=233 id="Picture_x0020_1" src="cid:image001.jpg@01CDFA4B.2EBDBC10"></span><o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>The vertical yellow bar indicates when the water in the pot reached 30 C and the blue when it reached 70 C. The black line is the CO/CO2 ratio. It goes from wonderful (much less than 1%) to 9% in a few seconds.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Looking at the excess air (green line) you can see that it was creeping up as the fire got smaller. That is a bad sign and can be prevented (well, considerably delayed) by using counter-flowing preheated primary and secondary air as discussed a couple of days ago. Marc, this is a good lesson. If the EA had not risen so much the flame would have kept going a lot longer. Because it went out, the average COr for this pot heating efficiency test was 6.5% instead of perhaps 1.5%. When the EA jumps up like that (as the air is no longer being used by the flames) the heat transfer efficiency takes a big knock.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>The stove’s air is supplied to the fire from below and the fuel was black wattle, though this late in the fire it was mostly char.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Regards<o:p></o:p></p><p class=MsoNormal>Crispin<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>