Dear Paul ----- Original Message ----- From: Paul Olivier To: Discussion of biomass cooking stoves 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 <[email protected]> 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: [email protected] [mailto:[email protected]] 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 > _______________________________________________ Stoves mailing list to Send a Message to the list, use the email address [email protected] 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/ _______________________________________________ Stoves mailing list to Send a Message to the list, use the email address [email protected] 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/ ------------------------------------------------------------------------------ _______________________________________________ Stoves mailing list to Send a Message to the list, use the email address [email protected] 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/ ------------------------------------------------------------------------------ No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.1913 / Virus Database: 2114/4870 - Release Date: 03/14/12
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