Investigations of two packed fiber insulations in a horizontal pressure tube

A fiber insulation material was tested in a horizontal pressure tube of a high pressure gas tunnel. Pressure and temperature of the test gases air helium were up to about 40 bar and 400 C. Temperatures and heat fluxes in the different sectors indicated satisfactory results. Natural convection, which would have caused a modification of the insulation, appeared to be only weak. Fiber densities of 280 kg/cu meter and 400 kg/cu meter respectively prevented gas movements, though the cohering gas volume in the insulation was rather big. Pressure gradients caused by the flowing gas did not influence the insulation effect.