Paul (cc Andrew P, list ) 1. I think the solution to the apparent (low temperature) conflict here lies in thinking in two dimensions rather than one dimension (no interesting variations in the angular 3rd direction). The radiant dome surface is sending energy off in a wide range of angles - some even away well from the cookpot. I think if you take additional measurements at radial positions away from the axis of symmetry, there will be a radius beyond which the measured "with-dome" temperatures will exceed the "without-dome" measurement.
2. One way to boost the on-axis "with-dome" measurement is to add a conical (better paraboloidal) reflector. Too much energy is (I think) being sent off away from the thermocouple (and cookpot). If conical, I suggest (based on my solar cooker experience) an interior angle of about 80 degrees (half angle of 40). You may be able to find some spotlight reflectors (probably quasi-paraboloidal) of suitable dimensions, that can be used directly or will require minimum modifications. 3. Questions. a. While the measurements were being made, was there a cookpot in place? b. If so, did it seem that the rate of boiling was higher for the "with-dome" geometry? c. An interesting test could be with a thin (black) flat (large diameter - or a range of diameters) plate replacing the cookpot - and using the thermocouple to measure that plate temperature. Possible? Best of luck Ron ----- Original Message ----- From: "Paul Olivier" <[email protected]> To: "Discussion of biomass cooking stoves" <[email protected]> Sent: Wednesday, March 14, 2012 5:01:25 AM Subject: Re: [Stoves] radiant heat capture, total heat measurement See comments. On Wed, Mar 14, 2012 at 1:54 PM, Andrew C. Parker < [email protected] > wrote: Are you measuring the temperature of the gas or the radiant temperature or both? I am supposed to be measuring both. The temperature with the dome normally should not be be less than without the dome. This, though, is what's happening. This means, perhaps, that the probe is not absorbing thermal radiation very well. <blockquote> The gas temperature should go down with the dome and the radiant energy should go up. </blockquote> It makes perfect sense that the gas temperature should go down. I think that my probe, though, is not picking up the thermal radiation very well when the dome is present. But, then, without the dome, the probe turns red hot. With the dome, it does not. <blockquote> In reading the patents I posted earlier, the point appears to be to convert as much heat into IR as possible. Infraconic purports to convert 70% or more, which seems a reasonable goal, since the heaters are pointed down. </blockquote> I like very much the funnel that surrounds the infraconic heater. http://www.infraconic.com/ What is the funnel made from? <blockquote> If you want to measure the total radiant heat from the dome, it might be more complex than a single temperature probe. Both commercial heater patents burn the gas in/on the porous layer. Both use diffuser(s)/flame suppressor(s) before the combustion layer. I think that the gas diffusers in both designs also serve to reflect radiant energy back to the combustion layer. The Infraconic adds an amplifying layer after the combustion layer. Have you tried using the mesh dome as your primary gas burner (be careful of backfires)? </blockquote> Yes, if I turn the gas very low, I only get combustion of the gas in the apex of the dome. No backfires occur. <blockquote> The two chimney designs convert heat from a primary heat source and convert it into IR or visible light. There may be some secondary combustion in/on the porous layer. For Rocket stovers, the first thing that came to mind when I read the Infraconic patents and, more particularly after reading the chimney patent, was Aprovecho's study on controlling chimney draft. Andrew Parker (Not AJH, so feel free to take my comments with a sack of salt.) On Tue, 13 Mar 2012 22:38:02 -0600, Paul Olivier < [email protected] > wrote: <blockquote> 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. Paul </blockquote> ______________________________ _________________ Stoves mailing list to Send a Message to the list, use the email address [email protected]. 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/ </blockquote> -- 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/
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