EVALUATION OF SOLAR FURNACE APPLICATION TO PRODUCE HIGH TEMPERATURE SECONDARY REFERENCE POINTS IN THE RANGE 2000-3000 K

摘要

The expansion of industrial processes to ever higher temperatures has created the related need for precise measurements of physical phenomena in previously unexplored temperature regimes. These temperature measurements are commonly performed with optical devices, particularly optical pyrometers, and secondary temperature reference points have been established above 2000°C based on the melting of several refractory oxides. But temperature measurement using an optical device is a function of the optical properties of the material being used. One approach, that can be used successfully both to eliminate the effect of the material emissivity and to create the high temperatures required, is highly-concentrated solar energy focussed on a rotating cavity reactor filled with the melted reference material, referred to as self-crucible melting. Four refractory oxides were used for the experiments: HfO_2, Y_2O_3, Al_2O_3, Ho_2O_3. We use a 2 kW solar concentrator to supply radiant energy to a 30 cm3 rotating reactor filled with the various refractory oxides. As the highly-concentrated sunlight enters the reactor it melts the oxides, forming a cavity or self-crucible. This solar technique allows to: 1. reach the high temperatures necessary to melt the refractory oxides 2. perform high quality temperature measurements because the melted cavity approachs a black-body 3. preserve the purity of the material 4. realize various heating and cooling rates.