@Wyttenbach
If you really want to go down the rabbit hole of real physics, consider this:
If a resistor is considered to convert power 100% to heat, why does Kanthal A1 have an (basically greybody) ε of 0.7, and Nichrome an ε of 0.88?
Where does the remainder of ε of 1.0 (perfect blackbody) minus the ε of 0.7 or 0.88 go?
In other words, why is not a calibrated resistance wire not a perfect blackbody, when it should, as a resistor, convert power to heat perfectly?
Paradigmnoia
Member
- Member since Oct 23rd 2015
Posts by Paradigmnoia
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Here is some newer food for thought (published 2013, but articles seem to be from 1994).
These ceramics have high Si contents, and specimen E has the highest Al.
Surprise! They are rather close to the "pure" alumina ε numbers used many times here in various comments.
Notice both spectral ε and total ε plots, side by side.
Enjoy! (Google Book link, pages 159 - 174, especially the last two pages if you are in a hurry)The Institute of Energy's Second International Conference on CERAMICS IN ENERGY APPLICATIONS: Proceedings of the Institute of Energy Conference Held in London, UK, on 20-21 April 1994
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It seems to me that when a high V is applied across a powder, quite often the result is that the particles align in the potential, creating a circuit with less overall resistance.
I have seen a pencil align itself in a very high potential towards the shortest route to ground. It nearly killed me.
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Just for the record, I don't think that 100's of watts of power actually were transmitted out of the reactor without heating it. Maybe it could happen, which is good to keep in mind.
But the spectrally selective emitter-absorber and selective IR transmissivity are very important. Otherwise there could be no IR camera.
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Not really. The spectral transparency of alumina is pretty much it. Notice how it sounds so much different when said that way, rather than selective emitter.
Quartz glass is more obvious, because it is also transparent to visible light. But not so greatly different than alumina in the IR region.The trick is that transparent materials are more efficient radiators than blackbodies. Blackbodies get hotter, because they absorb heat, delay, even out frequencies by multiple emission-absorption-emission, then emit into space. This heating up of the object requires some energy. It does not heat up for "free". In steady state, this spectral redistribution delay and heating energy loss is not obvious.
But perfect transmitters will not heat up. The IR simply passes through, unimpeded. With no frequency conversion.
A blackbody therefore is as much a radiator as is possible at that temperature. But a selective transmitter can output more power in total than a blackbody, with the same input power, but the boundary temperature will be lower.I think I have that right.
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After all the fuss and bluster, there are NO real Rossi replications.
No Fluid Heater
No Lugano
No low-T E-CatLots of sort-of replications. A real Lugano replication would be very expensive....
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Ockham did not suggest "that the hypothesis that is simplest is better". He asked, what is the minimum number of assumptions needed to make a a hypothesis consistent and testable". A hypothesis with a hundred variables could easily be true, but how can one narrow that down to something that can be either invalidated or demonstrated to require more detail? The hypothesis that is simpler is easier to test.
The razor shaves, it is not Ockham's Cleaver. -
Why this application matters is that it disseminated plenty of IP to the whole world. The whole world can look at it, and build a Lugano device almost perfectly. And a couple of other ones.
Of course, no one has done an exact three phase copy of the Lugano device, at least publicly.
IH did not have to hand any instructions from Rossi to its other investments secretly. They did it in front of the whole planet. -
ε(sub)λ refers to the emissivity of a given wavelength, λ, and is known as spectral emissivity. When it averaged over all wavelengths it is known as total emissivity.
ε(sub)θ refers to the emissivity in a given direction, θ, and is known as directional emissivity. When ε(sub)θ is averaged over all directions, it is known as hemispherical emissivity.
Therefore the total hemispherical emissivity (ε) is the average emissivity over all wavelengths and all directions.
Normal of course, means perpendicular to, as in: "The IR light was focused to the hit the microbolometer at an angle normal to the array, which could only detect the λ in 7.5 to 13 μm range, even though the device was broadcasting IR in many other wavelengths (at least to some degree), and in almost all possible directions (ie: not in a beam).
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@Alan Smith
Interesting to note the coating of cement on wires. Alumina ceramic has been used to increase emissivity of some heater wire types, notably Kanthal, since it has the highest heat handling ability, but a fairly low emissivity compared to other heater wires. The coating increases the surface area, which can improve convection also. Of course, these coated wires need to be open to the air to do their convection magic. Careful critical radius calculations need to be made, to prevent insulating and therefore overheating, rather than help cool the wires or improve emissivity.
(Cooling the wire faster increases total heat generating capacity). -
@Wyttenbach
We actually know a lot about the Lugano materials, thanks to a patent application and the Lugano report.
The ribbed cement and caps are surfaced with Durapot 810 alumina base thermal conductive cement, and the rods are commercial tight grain 99.9% alumina.
Surface roughness, porosity, and ribs all increase the emissivity to some degree.I agree there is a fair bit of wiggle room.
For example, in theory, a high percentage (maybe even 100's of watts) of coherent short wave IR caused by a reaction could exit the alumina almost unimpeded in some wavelengths, depending on optical thickness, and not heat the alumina or appear in the IR spectral view band.
The wires would capture some of this, due to a broadband ε of 0.7 for Kanthal to an ε of up to 0.88 of Nichrome, and heat up anyways. This could reduce current input...
But that is of course both speculative and very complicated to model. -
@Alan Smith
What did you use to heat the alumina to 1600°C? -
In the other science thread, I have linked the MFMP Lugano thermal validation video. The thermocouple had something like 100°C variance, depending on the position relative to to a rib. The Optris will level that out by averaging over a larger area than a thermocouple can measure.
Attaching thermocouples has its own problems, in that the attachment method, like sticking under ceramic pieces or gluing the TC down with a blob of ceramic paste, will change the local temperature. Probably, IMO, the slightly detached TC in MFMP tests is closer to the real surface temperature than when held tightly to the ceramic under some ceramic material. The ceramic piece or blob will reduce heat transfer to the surface at that point, increasing the local temperature to some degree.
As far as the court case, I have no desire to comment on it. We have not seen the IH response, and the court will sort out whatever it will, whenever it will. No amount of jabber here will do much to change that.
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MFMP ε test.
Skip to about 54:40 and run to at least 58:00 to see the best part.External Content youtu.beContent embedded from external sources will not be displayed without your consent.Through the activation of external content, you agree that personal data may be transferred to third party platforms. We have provided more information on this in our privacy policy. -
I was just thinking that crap steel those shelving brackets holding up the reactor is made of probably has a lower melting point than the thermocouple. A little dab of insulation between the reactor and the metal won't help much. If Galvanized, then sure must stink like danger.
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some limited thermocouple data was captured by IH observers during the Lugano test
"observers", so more than one.
Then for the magician trick ash swap hypothesis, Rossi had to do the swap with maybe 9* people watching? (And be totally ready for it.)
*(six main authors, Bianchini, and (at least) IH two observers)
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@andrea.s
The remaining problem with the 1400°C external temperature is that the internal temperature will be higher, maybe 1500°C, perhaps more.The end of the skinny thermocouple wire (see the image I posted earlier) would probably fail. Type K melts at 1380°C, and will usually fail before that in small diameters.
Possibly even the coil windings might melt. Kanthal A1 melts at 1500°C, and is not recommended to be used above 1400°C or the oxide protection layer fails. Inconel wire melts at a lower temperature; I think 1430°C is the maximum for any Inconel alloy.(Maybe a very short burst of 1400°C external could be done, but would be very sketchy)
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Gotcha.
Then in this scenario, they simply do not calibrate the Optris while at or on the way up to from 380°C to 1400°C. Plausible.I do hope we get to find out more about what they did, and were thinking at the time.
The long-awaited update and Q&A session is long overdue. -
The problem(s) with putting 3 kW into the reactor is:
That requires another error, in that they report 1/3 that much power going in. (Flipped clamp, etc.)
At 3 kW, it would not be unlikely that the reactor actually could reach 1400 °C