[Stoves] radiant heat capture, total heat measurement

ajheggie at gmail.com ajheggie at gmail.com
Wed Mar 14 16:46:07 CDT 2012


[Default] On Tue, 13 Mar 2012 08:36:41 -0300,"Kevin"
<kchisholm at ca.inter.net> wrote:

>
>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.

Yes
>
>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)
>1: Blue Flame temperature by radiation measurement: 1000
>2: Gas temperature above dome (radiation)                1000
>3: Thermometer temperature of both gases                 1500
>4: Flame Emissivity of 1: and 2:                                    .2
>5: Flame emissivity for luminous flame:                         .8

it looks like Paul has done thios now
>
>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.

The trouble is that could increase PICs leaving the flame unburnt.

>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).

Having got a good, short, premixed flame I wouldn't advocate going
back to a diffusion flame. 

There is an example from the past where a chamical was added to town
gas to make a yeallow flame, I think it was called carburetted gas,
and a sall amount of petrol vapour was added to the CO+H2 mixture but
this was before gas manteles were available. I think gas mantles t=do
a better job as the light radiator because of the excitation
characteristics of thorium being better than glowing sooty particles.

AJH




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