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</o:shapelayout></xml><![endif]--></head><body lang=EN-CA link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal>Dear Stove designers<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I am forwarding a short paper on the subject of heat transfer between air flow and metal plates. When thinking of how to heat a perforated skirt the formulas can be used directly. Some recent discussion on preheating air for stoves shows the contents may be relevant but the heat transfer direction will be reversed.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>There are various approaches taken to determining the effectiveness of heating air with hot metal where that metal is heated by convective and radiated heat from the fire within. Bejan’s <i>Convective Heat Transfer</i> (2005) also has a section on the subject.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>The flow velocity range discussed here is from 17-60mm per second but the pressure starts at 4 Pa which is a little high for some short stoves (Jiko and many charcoal stoves, for example) which have pressure gradients of 1-2 Pa. So, this is not an all-encompassing set of formulas because of these limitations. It may however by useful for TLUD design and counter-draft preheaters (downward heating) applications where the velocity is low and there is an intention to heat the air or to capture heat from a hot gas stream (check the Reynolds numbers against the gas composition).<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>