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</o:shapelayout></xml><![endif]--></head><body lang=EN-CA link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoPlainText>Dear Andrew<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>That is a very sensible idea. <o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>If the exhaust had some secondary preheating function (on the way down) it could arrive in the lower end cool enough to do some good.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>A major problem with simple stoves is they have way too much excess air mostly because people have no way to measure it and don't know what target to choose.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>If it was low in CO2 and high in O2 <i>and</i> it is going to arrive slightly heated, it will make things worse.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>I think there are a couple of ways to use natural draft to run some back. It got me to thinking about how much it might have to be ….15%? 10%? The secondary would have to be increased, not so?<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Regards<br>Crispin<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>>How is it used to lower the temperature? By interfering with the O2 supply thus reducing the burn rate? Or the efficiency of combustion? <o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Mostly it's from CO2 in the exhaust gas reacting with any char above 850C and being reduced to CO, this is highly endothermic and quenches the hot coals which in 21% oxygen would reach 1200C. I cannot see it being possible with natural draught.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>AJH<o:p></o:p></p></div></body></html>