From: Bob Higgins * We will probably be able to add only up to 1kW in this coil. It is supplementary to the main heater coil which will be around this one. We believe the main Kanthal coil can supply 2.4kW. The total electrical heater input for the experiment can get to the 3.4kW range.
Bob, if the inner coil - of a double coil set is raised to 1300 0C by the addition of 750 watts, then you have a major problem for the above scenario unless this design turns out to be a much better thermal conductor than can be expected from its nominal composition. This looks to me like this is not going to turn out as planned, but it is encouraging to see that it is being undertaken at all, and ***thank you*** and others for your efforts to understand the thermodynamics of the dog-bone. Since the outer coil - before any power is applied to it – will feel 1100-1200 0C heat from the insert, we have a high incremental starting point for additional power, which seems not to have been adequately considered . Thus, it may be a mistake to imagine that one can add an additional 2.4 kW to the outer coil and not fry the internal coil. Alumina has relatively high thermal conductivity – at least for a ceramic, but too much has been made of this property in the big picture… since it is still a ceramic and is 700% lower than say SiC – the previously used ceramic - which would have been a better choice if heat transfer was the main consideration. IMHO Rossi may have chosen alumina instead of SiC or even nixed the application of a black SiC coating, simply because he does NOT want a blackbody radiator under these circumstances, and an alumina emitter will affect the IR camera differently than SiC. That conclusion is based on Rossi having switched to alumina from SiC in an earlier version. The good news is this - if MFMP were to use the same IR camera setup and the same calculations, then they may see the same apparent gain with the alumina - using only one kW input, even though it is a “dummy”. That will be most interesting. Jones
