[Stoves] radiant heat capture, total heat measurement

Thu Mar 15 13:12:00 CDT 2012

Kevin,

You say:
*# OK!! A 50% reduction in boiling time is very significant.
What can you now tell us that will enable us to apply it to other stoves
and combustion conditions?*

I once did an experiment in which I made the 150 Belonio about half its
original height.
I then filled it with chunks of wood and put a Belonio burner on top.
This was a natural draft unit without a fan.
This is what it looked like:
http://dl.dropbox.com/u/22013094/150%20Burner/Image2097.jpg
But looking back on this, I see that there were so many problems with this
burner,
 even aside from the fact that it had no burner housing.

You raise an interesting question, though, which has always led me to wonder
 why the Belonio burner hole pattern was not adopted on natural draft units.
If a burner housing were added, I think the unit I experimented with would
work much better.
The central problem that I see with a natural draft unit is an uneven
upward flow of primary air.
At times too much CO2 is created, and some burner holes lose their flames.
Also I would imagine that the inlet of primary air has to be strictly
control to get a consistent outlet of gas at the burner.

A natural draft TLUD is very complicated,
 and I truly marvel at those who get them to work on such a broad variety
of fuels.

Thanks.
Paul

On Fri, Mar 16, 2012 at 12:36 AM, Kevin <kchisholm at ca.inter.net> wrote:

> **
> Dear Paul
>
> ----- Original Message -----
> *From:* Paul Olivier <paul.olivier at esrla.com>
> *To:* Discussion of biomass cooking stoves<stoves at lists.bioenergylists.org>
> *Sent:* Thursday, March 15, 2012 3:31 AM
> *Subject:* Re: [Stoves] radiant heat capture, total heat measurement
>
> As you all recall, Belonio and I, using the same reactor and the same
> burner,
>  report a difference in boiling times.
> I was bringing a liter of water to a boil in about half the time that
> Belonio was reporting.
> I assumed this was because of the dome.
> But this assumption now appears to be completely wrong.
>
> The dome does not reduce in any way the amount of time it takes to bring a
> liter of water to a boil.
> In an experiment this morning, I took the dome off the burner
>  and put the pan of water at exactly the same height as if the dome were
> in place.
> I did a second experiment with the dome in place.
> The boiling times were exactly the same with or without the dome.
> I apologize to you all in leading you to think that thermal radiation was
> making a big difference.
>
> # No problem!! You raised some interesting questions relating to stove
> operation and improvement.
>
>
> So now the only thing that remains to account for the difference
>  in boiling times between Belonio and me is the burner housing that I put
> around the burner.
>
> # OK!! A 50% reduction in boiling time is very significant. What can you
> now tell us that will enable us to apply it to other stoves and combustion
> conditions?
>
>  Thanks!
>
> Kevin
>
>
> The burner housing feeds secondary to the burner holes.
> What you see here:
> http://www.youtube.com/watch?v=nZDt8DfgSls
>  appears to be just as efficient as what you see here:
> http://www.youtube.com/watch?v=yO3jcbQj-GI
>
> Here is a picture of the burner with burner housing:
> http://dl.dropbox.com/u/22013094/150%20Gasifier/Boiling/IMG_1024a.JPG
> The two parts are welded together.
>
> Also I did another test in which I boiled water without the dome -
>  but this time at about one inch lower than the dome pan height.
> This put the pan one inch closer to the flames.
> Again there was no difference at all in boiling times.
>
> Also I took several temperature readings:
>
>
>    1. with the probe as close as possible to the blue flames: 646 C
>    (probe turned red)
>    2. with the dome in place and at the top of the dome: 463 C
>    3. with the dome removed but with the probe at the same height as if
>    the dome were there: 532 C (probe turned red)
>    4. with the dome and with a pan of water above it: 390 C (probe
>    situated in between the two)
>
> Thanks.
>
> Paul
>
>
> On Thu, Mar 15, 2012 at 9:26 AM, Tom Miles <tmiles at trmiles.com> wrote:
>
>> Alex, Paul,
>>
>> One option is to use a suction pyrometer in which you pull the hot gas
>> past
>> the thermocouple in a tube. The tube limits the radiation so you get a
>> better picture of the true temperature. Temperatures can be about 90C
>> (200F)
>> higher in the suction pyrometer than in a boiler or free air. A simple
>> version can be made with compressed air venture drawing air through a pipe
>> with a thermocouple inside it.
>>
>> Tom
>>
>> -----Original Message-----
>> From: stoves-bounces at lists.bioenergylists.org
>> [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Alex
>> English
>> Sent: Wednesday, March 14, 2012 6:18 PM
>> To: Discussion of biomass cooking stoves
>> Subject: Re: [Stoves] radiant heat capture, total heat measurement
>>
>>  Paul,
>> So this makes sense. The screen radiates away heat leaving a cooler gas
>> beyond.
>> If your thermocouple were smaller or shielded the difference would likely
>> be
>> even greater because the thermocouple looses  more heat from radiation
>> when
>> it is hotter.
>>
>> Or are there other reasons, too?
>> Alex
>>
>>
>>
>> On 14/03/2012 7:36 PM, Paul Olivier wrote:
>> > 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
>> >
>>
>>
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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/
>
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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/
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