[Stoves] radiant heat capture, total heat measurement

[Paul Olivier]

Ron,

This is not a very good video clip, but it does show the entire 150
gasifier:
http://youtu.be/8IcXDAK37gA
This is a rough prototype made by hand.
The mass-produced product should look better.

Also I do not envision that this gasifier be operated as a stand-alone
device.
For safety reasons it should be set within a counter-top enclosure, as seen
here:
http://dl.dropbox.com/u/22013094/150%20Gasifier/Jpegs/008.jpg

Thanks.
Paul

On Sun, Mar 11, 2012 at 2:48 AM, Paul Olivier <paul.olivier at esrla.com>wrote:

> Ron,
>
> I did yesterday an experiment with aluminum foil to reflect back up the
> thermal radiation emitted from the dome.
> The aluminum starts to wrinkle and crack well before the burn is complete.
>
> Also I tried yesterday a wire mesh of an aperture of 30 mesh.
> This did not work as well as what I am using now (a stainer that I bought
> in the market).
> I have yet to find the factory that makes this strainer,
>  and I do not have the instrument that is needed to measure its aperture.
>
> Ron, I think that the foam that you have found offers the most promise.
> I am sure that this foam will deliver more radiant energy than stainless
> steel wire mesh.
> Also I hope to employ a type of funnel that would surround the dome and
>  focus the laterally emitted thermal radiation toward the pot.
> Finally the pot has to absorb and not reflect.
>
> Thanks.
> Paul
>
>
>
> On Sun, Mar 11, 2012 at 1:58 AM, <rongretlarson at comcast.net> wrote:
>
>> Andrew, Paul, Crispin, list:
>>
>>    1.   The last several paragraphs below are coming out more negatively
>> on radiant heat capture than I think are appropriate.  Remember, the
>> initial information provided by Paul Olivier on March 2, when he said:
>>
>> "When a wire mesh dome is placed on top of the burner and burner housing,
>>  this roughly doubles the amount of heat being transferred to a pot:"
>>
>>    2.  I think this doubling has little to do with the exchange below
>> (and a few earlier that are similar).  Radiant heaters are  widely sold
>> because of their efficiency in heat transfer - in many cases involving zero
>> convection.  Given we have only one (above) piece of data for one stove,
>> the chances are that a doubling is not the maximum we can achieve.
>>
>>    3.  I would look at this as a conservation of energy problem. We know
>> that we can transfer more energy to the pot if the radiator is hotter.
>> There may be catalysts that we can employ.   We know how to use reflectors
>> and obtain high absorption (and sometimes simultaneously low emissivity)
>>      In my reading on ceramic foam, I found that some foam is being
>> employed so as to have gas combustion take place inside the foam!.
>>
>>    4.   I hope that others can perform some experiments along these lines.
>>
>> Ron
>>
>> ------------------------------
>> *From: *ajheggie at gmail.com
>> *To: *"Discussion of biomass cooking stoves" <
>> stoves at lists.bioenergylists.org>
>> *Sent: *Saturday, March 10, 2012 3:31:17 AM
>>
>> *Subject: *Re: [Stoves] radiant heat capture, total heat measurement
>>
>> On Fri, 9 Mar 2012 12:25:49 +0200, Crispin Pemberton-Pigott wrote:
>>
>> >>...and passes visible light and higher frequency infra red from hot
>> bodies,
>> >like the sun,
>> >
>> >
>> >
>> >Most of it, the rest makes it warmer (absorbs).
>>
>> Yes that which it absorbs make it warmer but equally as a warm body at
>> equilibrium it will be re emitting longer wavelength IR.
>> >
>> >
>> >
>> >>but absorbs the lower energy infra red from cooler bodies like earth and
>> >our bodies.
>> >
>> >
>> >
>> >Yes, and because it is warm, and active in the IR, it also emits IR but
>> with
>> >a low emissivity. In other words if you know the emissivity, you can read
>> >the temperature with an IR gun.
>>
>>  it is emitting a different (lower) frequency from which it has
>> absorbed.
>> >
>> >
>> >
>> >But more to the point I was saying that at a lower (non 90°) angle, it
>> >starts to reflect radiation from the top of the surface. Look at glass
>> at a
>> >low angle and it looks like a mirror.
>>
>> Agreed
>> >
>> >
>> >
>> >The point is that when reflecting heat, if the incident angle is past a
>> >critical value, it reflects pretty much all of it so the issues Kevin
>> >mentioned about the mirroring on the back don’t come into play.
>>
>> This depends on the refractive index of the two materials, going from
>> a lower to higher there is always some light transmission, the other
>> way round and you have total reflection, this is how a light fibre
>> works.
>> >
>> >
>> >
>> >Paul’s question was about reflecting the heat. So the principles are the
>> >reflectivity, surface finish, incident angle and emissivity. While a
>> stove
>> >may be good at sending IR radiation towards the pot, pots are not all
>> that
>> >good at picking it up, actually. Stainless steel pots are quite
>> reflective
>> >and do better picking up heat by convection.
>>
>> The major salient point is that radiation from heating something by
>> flame/flue gases is only ever going to extract a minor portion of the
>> heat in the gas stream. Consider a black body in the gas flow, it can
>> never be hotter than the gas flow downstream of it, as you make it
>> hotter it radiates more heat but the rejected gas flow is also hotter,
>> either way you still need to have the convection do most of the work.
>> AJH
>>
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>>
>
>
> --
> Paul A. Olivier PhD
> 27C Pham Hong Thai Street
> Dalat
> Vietnam
>
> Louisiana telephone: 1-337-447-4124 (rings Vietnam)
> Mobile: 090-694-1573 (in Vietnam)
> Skype address: Xpolivier
> http://www.esrla.com/
>



-- 
Paul A. Olivier PhD
27C Pham Hong Thai Street
Dalat
Vietnam

Louisiana telephone: 1-337-447-4124 (rings Vietnam)
Mobile: 090-694-1573 (in Vietnam)
Skype address: Xpolivier
http://www.esrla.com/
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