Thermal Performance Test of a Coaxial Double-Tube Hot-Gas Duct

A coaxial double-tube hot-gas duct with an internal insulation layer is to be used for the High-Temperature Engineering Test Reactor (HTTR), a gas-cooled reactor designed by the Japan Atomic Energy Research Institute. A full-scale simulation of part of the hot-gas duct was constructed to verify its structural integrity. No hot spot was detected on the inner tube under HTTR operation conditions after 7700 h. Natural convection was negligible in the internal insulation layer. An experimental correlation of the effective thermal conductivity for the internal insulation layer was also obtained.