@kuru I don't see, how a carbon fibre shell shall be usefull then. If you want it structurally strong, the fibers need to go along the shell shape, but then it's insulation. If you want it to be a good conductor, the fibers need to be perpendicular to the shell shape, but then it loses its strength. Plus, it won't reach 800 W/mK, since a wide bundle of very short fibers would be more like a dust than a solid form. I.e. they need to be embeded in a matrix like an epoxy, which surely won't be as good a conductor. Plus, the heat couldn't spread throughout the shell shape very well. Making it a copper shell on the other hand, ...