- I am building a Ruben's tube from aluminum tubing (100 mm diameter, 1.2 m long). I expect it to get very hot (say >200C), so for safety in a classroom I want it to be as cool as possible. I would like it to run for about 20 minutes on natural gas. Its raw alumium surface now (grey/silver), should I leave it or paint it black.
My thinking is that a paint coating will slow down heat loss due to an insulation effect, but at the same time speed up radiative heat loss from the outside black paint surface. I am unsure though which effect may be the greatest and therefore the net effect on tube temperature. Many thanks