Hello boys !A very quick answer between two meetings. Paradigmoia, nice that you have found that reference but I presume that you have not understood it very well.Emittance and Emissivity are two different concepts. Emittance is an extensive property of the material that depends also on the thickness of the layer considered while Evissivity is intensive property of surface.When trying to measure the temperature of a surface we must consider Emissivity that, in simple terms, indicates how much power is radiated at a certain temperature from the surface respect the radiated power of a Black Body.Quantum Mechanics states that at a certain temperature nothing can radiate more power then a Black Body (also known as perfect absorber) at any wave length. So emissivity is defined by the ratio of the integrated power spectrum radiated by a body and the integrated power spectrum of the Black Body and have values always <1 and is a non dimensional quantity. Factory calibration of the infrared camera, optris provide calibration files for each single camera and IR optics, ensures that Is the emissivity value that must be used in the setup. Not surely the emittance. As a proof look first at your graph, noting that there is not much variation from 300K to 1050k, so if we accept your statesment the group shuold have used a 0.9 value even for the rods, BUT from the IR images we note that the reference dot (which has an emissivity 0.95) looks as bright spot . This meas that the alumina pipe has an emissivity much lower then the dot !Nevertheless the authors in fact have forgotten a detail, that doesn't create a real problem but should be noted. In the case of the reactor Alumina is put on the Kanthal wires and becoming partially transparent to IR at high temperatures part of the radiation to the camera comes directly from the wire. Because the actual material of the wire was unknown so also the alumina thickness it was impossible to make a correct calculus of the actual emissivity that was a convolution of three functions on T: wire emissivity, alumina transparency, alumina emissivity.Data of emissivity Alumina on Inconel is commonly available for IR measurements:http://www.scigiene.com/pdfs/4…erEmissivitytablesrev.pdf
As you see from the table the range given .69 at 427 °C and .45 at 1093 °C match quite well the values actually used by the Authors.Finally even if we suppose that a slightly higher figure for the emissivity parameter was a better choice for the reactor body during the run we should note that the actual measured emitted Energy has a very weak dependency on that parameter.That because IR camera use the emissivity in the inverse of the Stefen Boltzmann law to obtain the temperature and when we recalculate the energy the two factors cancel.The reported result seems correct and we estimated that in the most pessimistic and unrealistic scenario they should be 30% higher then real tacking the COP to 2.57. The rest of the analysis remains valid and due to the long amount of time of the run the energy produced seems far beyond any chemical source.This was a quick answer..... CU next time.... pardon me if there was any Typo.
LOL Come ON !!!!! They forget this "detail"
