Andrew,<br><br>I am sorry: I do not understand what you have written below.<br><br>Yesterday I bought a thermocouple that can measure up to 1,000 C.<br>This morning I will use it to measure temperature with and without the dome.<br>
Both measurements will be taken at the same height above the burner (the height of the pot).<br><br>Any suggestions?<br><br>Paul<br><br><div class="gmail_quote">On Tue, Mar 13, 2012 at 6:36 PM, Kevin <span dir="ltr"><<a href="mailto:kchisholm@ca.inter.net">kchisholm@ca.inter.net</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Dear Andrew<br>
<br>
I think your very last comment is very important, and that its importance is being overlooked.<div class="im"><br>
"Yes the glowing dome will radiate more power than the blue flame."<br>
<br></div>
A "blue flame" has very poor flame radiation characteristics. A yellow or red flame has very superior flame radiation characteristics. "Flame Luminosity" basically equals better radiation characteristics.<br>
<br>
One way to look at it is that "Blue Flames are too smart by half." :-) There is a gain in completeness of combustion, and probably higher temperature for "products of combustion", and reduced sooting of pots, BUT there is a significant loss in luminosity, and heat transfer to the pot by radiation. The Mesh Dome, heated by direct convection of the "blue flame" then is in a position to add a "radiation contribution" to heat transfer capability.<br>
<br>
It would be a very interesting experiment to take a "flame temperature" of Paul Oliver's system, with, and without the dome. My guess is that the "flame temperature" of the "Blue Flame", and the gases leaving the dome would be similar, and relatively low, even though the actual thermocouple measured temperature of the gases would be high. In very simplistic terms (for illustrative purposes only)<br>
1: Blue Flame temperature by radiation measurement: 1000<br>
2: Gas temperature above dome (radiation) 1000<br>
3: Thermometer temperature of both gases 1500<br>
4: Flame Emissivity of 1: and 2: .2<br>
5: Flame emissivity for luminous flame: .8<br>
<br>
Thus, if some of the pyrolysis gases were diverted away from the "blue flame conditions", and were allowed to increase the flame luminosity, there could potentially be an opportunity to "have your cake and eat it." More specifically, the addition of some "luminous fractions" to the flame could, for example increase flame luminosity to say .6. but with a drop in actual gas temperature to say 1300 because of incompleteness of combustion.<br>
<br>
In other words, "Heat Transfer capability to the Pot" would be:<br>
1: Blue flame: 1500 x .2 = 300<br>
2: Blue + Yellow" flame conditions = 1300 x .6 = 780<br>
<br>
For a "Blue Flame + Radiation Dome, conditions might be<br>
1300 x .4 = 510<br>
<br>
(NOTE: All these numbers are arbitrary and purely illustrative, to explain the concepts)<br>
<br>
So.... if the concepts are correct, then it would seem that the best way to make a stove would be to make one with a burner that produced BOTH yellow flame(for luminosity) and a blue flame (for completeness of combustion).<br>
<br>
Does that "hang together for you?<br>
<br>
Best wishes,<br>
<br>
Kevin<br>
<br>
<br>
<br>
----- Original Message ----- From: <<a href="mailto:ajheggie@gmail.com" target="_blank">ajheggie@gmail.com</a>><div class="im"><br>
To: "Discussion of biomass cooking stoves" <<a href="mailto:stoves@lists.bioenergylists.org" target="_blank">stoves@lists.bioenergylists.<u></u>org</a>><br></div>
Sent: Monday, March 12, 2012 6:58 PM<div class="im"><br>
Subject: Re: [Stoves] radiant heat capture, total heat measurement<br>
<br>
<br>
</div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div class="h5">
On Mon, 12 Mar 2012 06:18:14 +0700, Paul Olivier wrote:<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
More primary air means more gas.<br>
</blockquote>
<br>
Yes<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
It does not necessarily mean more excess or secondary air.<br>
</blockquote>
<br>
No but it the primary gas stream acts as an ejector or aspirator to<br>
entrain the secondary air.<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
My simple understanding of what is happening here is that<br>
wind does not disturb what is happening within the dome.<br>
</blockquote>
<br>
I think so too.<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Wind does not dissipate heat so easily.<br>
</blockquote>
<br>
I cannot see this once outside the dome.<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
This gives a better transfer of convective heat,<br>
</blockquote>
<br>
Nor this.<br>
<br>
The only single thing that increases the transfer to the pot from the<br>
rising gases is if they are at a higher temperature.<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
and it also gives more thermal radiation.<br>
</blockquote>
<br>
Yes the glowing dome will radiate more power than the blue flame.<br>
<br>
AJH<br>
<br>
<br>
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</div></div></blockquote></div><br><br clear="all"><br>-- <br>Paul A. Olivier PhD<br>27C Pham Hong Thai Street<br>Dalat<br>Vietnam<br><br>Louisiana telephone: 1-337-447-4124 (rings Vietnam)<br>Mobile: 090-694-1573 (in Vietnam)<br>
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