So the heater coils in the 2013 test were embedded in ceramic sheath which covered a steel vessel. I was recalling the 2013 test as if the coils were inside the steel vessel. It all makes sense now.
Harry On Tue, Oct 14, 2014 at 11:24 AM, Alan Fletcher <a...@well.com> wrote: > Yes, sorry -- I was referring back to the 2013 test. > > For that we had a picture of the ceramic frame holding the resistor wires, > which was cast in two (I recall, without looking it up) sections. > > For a small area, we have a solid plate (complicated by fins), and then a > cog-like structure with the gap towards the outside. > Presuming that this makes good thermal contact to the outer cylinder we > can approximate it as a rectangular block with a rectangular hole, with the > wire in the center. > > The wire itself is mostly in poor contact with the holder, so it supplies > heat by thermal radiation (or induction, though I think that's less likely). > > There are two pathways from the inner hot zone: by conduction through the > solid part of the gear, and by radiation through the gap. (It's probably > close to thermal equilibrium.) > > Given that Alumina is an insulator, I don't know which wins, but there is > definitely a possibility of a temperature difference, which may persist. > > I don't have the tools (comsol etc) to model the radiation in and across > the gap. > > ------------------------------ > >
