[Stoves] radiant heat capture, total heat measurement
Paul Olivier
paul.olivier at esrla.com
Wed Mar 14 18:36:53 CDT 2012
There are problems with what I have written below.
Let me again.
Without the dome, the probe encounters hot gases and registers a
temperature of 563 C.
It turns red hot and starts emitting thermal radiation.
With the dome, the probe encounter hot gases as well as thermal radiation.
But it only registers a temperature of 500 C.
It does not turn red hot.
Therefore the probe does not absorb thermal radiation from the dome very
well.
Thanks.
Paul
On Thu, Mar 15, 2012 at 5:57 AM, Paul Olivier <paul.olivier at esrla.com>wrote:
> Is it possible that the probe is not efficiently absorbing thermal
> radiation when the dome is in place?
> With the dome, the color of the probe is the same as when it is cool.
> But without the dome, the probe turns red hot.
>
> With the dome, the temperature of the probe (first measurement) is 500 C.
> At this temperature, the probe does not absorb and emit very much thermal
> radiation.
> But without the dome, the temperature rises to 563 C (first measurement).
> Here the probe absorbs and emits much more thermal radiation, evidenced by
> the fact that it turns red hot.
>
> So at 500 C the probe is mostly measuring the temperature of the gas.
>
> Thanks.
> Paul
>
>
>
> On Wed, Mar 14, 2012 at 11:08 PM, Frank Shields <frank at compostlab.com>wrote:
>
>> Dear Stovers,****
>>
>> ** **
>>
>> This is all very interesting. I think the goal is to make the flame
>> uniform with the hottest temperature of the flame on an even plane.
>> Therefore the bottom of the pot can be placed in the even hot spot. The
>> dome seems to do just that. Without the dome the flame is much more three
>> dimensional. Hot spots at all vertical levels. With the dome the heat
>> measured may be less than without the dome but I’m thinking the overall
>> average heat hitting the pot bottom will be higher. ****
>>
>> ** **
>>
>> Regards****
>>
>> ** **
>>
>> Frank****
>>
>> ** **
>>
>> ** **
>>
>> Frank Shields****
>>
>> 42 Hangar Way****
>>
>> Watsonville, CA 95076****
>>
>> (831) 724-5244 tel****
>>
>> (831) 724-3188 fax****
>>
>> frank at biomasslab.com****
>>
>> ** **
>>
>> ** **
>>
>> ** **
>>
>> ** **
>>
>> ** **
>>
>> *From:* stoves-bounces at lists.bioenergylists.org [mailto:
>> stoves-bounces at lists.bioenergylists.org] *On Behalf Of *Kevin
>> *Sent:* Tuesday, March 13, 2012 11:18 PM
>>
>> *To:* Discussion of biomass cooking stoves
>> *Subject:* Re: [Stoves] radiant heat capture, total heat measurement****
>>
>> ** **
>>
>> Dear Paul****
>>
>> ----- Original Message ----- ****
>>
>> *From:* Paul Olivier <paul.olivier at esrla.com> ****
>>
>> *To:* Discussion of biomass cooking stoves<stoves at lists.bioenergylists.org>
>> ****
>>
>> *Sent:* Wednesday, March 14, 2012 1:38 AM****
>>
>> *Subject:* Re: [Stoves] radiant heat capture, total heat measurement****
>>
>> ** **
>>
>> Alex,
>>
>> I took three sets of temperature readings with and without the dome.
>>
>> With Without
>> Reading 1 - 500 C 563 C
>> Reading 2 - 473 C 578 C
>> Reading 3 - 470 C 571 C
>>
>> All measurements were taken at the same height above the burner.
>> With the dome, the probe remained its normal color.
>> Without the dome, the probe got red hot.
>>
>> The burner that I am using is a Belonio burner.
>> In a first step I added a burner housing to the Belonio burner.
>> In a second step I added the dome.
>> I can't imagine that the burner housing alone accounts
>> for the much better boiling time that I get in comparison to Belonio.
>> I am totally at loss in explaining these temperature readings.****
>>
>> ****
>>
>> # The above results seem consistent with the hypothesis I presented in my
>> posting of 13 March, 8:37 AM ADT. Basically: The Belonio blue flame has low
>> luminosity, while with the dome, it is heated by the non luminous blue
>> flame gases, and the "loss by radiadiation from the dome" cools the gases.
>> You seem to have missed the posting or it point. Accordingly, I include a
>> copy below.****
>>
>> Best wishes,****
>>
>> ****
>>
>> Kevin****
>>
>>
>>
>> Paul
>>
>>
>>
>> *****************************************************************************
>> ****
>>
>> ****
>>
>> ----- Original Message ----- ****
>>
>> From: "Kevin" <kchisholm at ca.inter.net>****
>>
>> To: "Discussion of biomass cooking stoves" <
>> stoves at lists.bioenergylists.org>****
>>
>> Sent: Tuesday, March 13, 2012 8:36 AM****
>>
>> Subject: Re: [Stoves] radiant heat capture, total heat measurement****
>>
>> ** **
>>
>> > Dear Andrew
>> >
>> > I think your very last comment is very important, and that its
>> importance is
>> > being overlooked.
>> > "Yes the glowing dome will radiate more power than the blue flame."
>> >
>> > 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.
>> >
>> > 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.
>> >
>> > 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
>> >
>> > 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.
>> >
>> > In other words, "Heat Transfer capability to the Pot" would be:
>> > 1: Blue flame: 1500 x .2 = 300
>> > 2: Blue + Yellow" flame conditions = 1300 x .6 = 780
>> >
>> > For a "Blue Flame + Radiation Dome, conditions might be
>> > 1300 x .4 = 510
>> >
>> > (NOTE: All these numbers are arbitrary and purely illustrative, to
>> explain
>> > the concepts)
>> >
>> > 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).
>> >
>> > Does that "hang together for you?
>> >
>> > Best wishes,
>> >
>> > Kevin
>> > ****
>>
>>
>> _______________________________________________
>> Stoves mailing list
>>
>> to Send a Message to the list, use the email address
>> stoves at lists.bioenergylists.org
>>
>> to UNSUBSCRIBE or Change your List Settings use the web page
>>
>> http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org
>>
>> for more Biomass Cooking Stoves, News and Information see our web site:
>> http://www.bioenergylists.org/
>>
>>
>>
>
>
> --
> 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/
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20120315/6811a046/attachment.html>
More information about the Stoves
mailing list