I believe the ends, between the central tube and the outer 2 cm hot tube, are filled in with a refractory cement. In fact, that whole space, and maybe not the ends could be filled in to help improve the thermal conductivity. Most importantly it should keep out the air that could oxidize the heater wire. It would not have to be hydrogen tight or anything - just keep out the air. If you look at the photo, the ends don't look beautifully finished, nor need they be.
The central tube is probably a cast tube with one end having a cast in closure. The open end, as the report says, is plugged with an alumina tube having in its center a thermocouple. When the plug is glued into place (available nearly line-to-line fit from Coorstek), it will seal the end of the central tube. On Wed, Oct 15, 2014 at 12:08 PM, ChemE Stewart <cheme...@gmail.com> wrote: > Me too, good job. Tube in a tube reminds of the model rockets I used to > build. Fin supports between tubes might explain the wider dark band seen > as a spiral?. Do you think a lot of the heat might be discharged in a > space between tubes and out the ends? Or are the ends completely sealed? > > On Wednesday, October 15, 2014, Jed Rothwell <jedrothw...@gmail.com> > wrote: > >> You & Alan have done an amazing job sleuthing out the details of this >> thing. I suppose you are right, although I cannot tell. If you are right it >> is a great job and if you are wrong you have a vivid imagination! >> >> - Jed >> >>
