High temperature transparent furnace development

A prototype transparent furnace was designed, fabricated, and tested at temperatures up to 1473K. Radiation containment using an outer infrared mirror tube and convection elimination using vacuum insulation reduce electrical power consumption and heat loads on critical components. High vacuum was necessary to eliminate convection; even 0.001% atmosphere pressure caused large convective heat losses. A heat transfer model was developed to predict the behavior of the transparent furnace and permit projection of performance improvements resulting from design changes. The mirror tube that reflects infrared radiation and transmits some visible radiation was modified to eliminate radiation absorption in the mirror tube itself. Radiation shields were added to the ends of the furnace to further reduce radiative heat losses. Conductive heat losses were minimized by minimizing solid connections to the cooled furnace ends and by using quartz supports. All components were designed to survive high temperature operation. Extensive experiments were performed with a succession of preliminary prototypes, leading to a final prototype successfully tested at 1473K.