Effective Thermal Conductivity of Soda-Lime Silicate Glassmelts with Different Iron Contents Between 1100°C and 1500°C

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Abstract

This study presents a simple method for retrieving the effective thermal conductivity of semitransparent glassmelts from measured temperature profiles. Effective thermal conductivity of molten glass at high temperature is an important thermophysical property that affects the glassmelting and forming processes and thus the quality of the final glass products. In semitransparent glassmelts, heat is transferred by both conduction and radiation. In the limiting case of optically thick glassmelts, typically featuring high iron content, thermal radiation can be treated as a diffusion process. The total heat flux can be expressed as the sum of a phononic and a radiative heat fluxes based on Fourier's law. For weakly absorbing glassmelts, the temperature profile may be strongly nonlinear particularly neat container walls due to the contribution from emission and absorption. Steady-state measurement techniques, such as the linear heat flux method, have been developed to measure glassmelt effective thermal conductivity at high temperatures. However, they typically use only three temperatures measurements and assume linear temperature profile in the glassmelt. The new retrieval method addresses these drawbacks particularly for weakly absorbing glassmelts featuring nonlinear temperature profiles. It is demonstrated with experimental data collected for soda-lime silicate glasses with iron content ranging from 0.008 to 1.1 wt% and temperatures between 1100°C and 1550°C.

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