1997, Endrýs, Jiří, Geotti-Bianchini, Franco, De Riu, Luca

The spectral absorption coefficients of container glasses in the wavelength region from 0.4 to 4.5 µm and in the temperature range from room temperature to 1400 °C were measured by a single-beam spectrophotometer by means of the transmission method. From the measured absorption coefficients radiative thermal conductivities in the temperature ränge from 600 to 1400 °C were calculated by means of Rosseland's diffusion approximation. The intensity of the band at 2.8 µm due to dissolved hydroxyl groups in glass was also calculated. While most previous measurements were performed on model glasses with a very simple basic composition, molten in laboratory furnaces from pure raw materials, the glasses investigated in this paper are the most frequently used types of container glasses with a complex composition and different chromophores. The influence of different coloring agents and dissolved water on the spectral behavior and radiative thermal conductivity of glass were studied, checking how the spectra change from room temperature to high temperature.

1993, Endrýs, Jiří, Blažek, Antonin, Ederová, Jana

An experimental furnace for the determination of the effective thermal conductivity of molten glass was constructed. As the values of thermal conductivities previously measured by direct experimental methods depend strongly on the thickness of the glass layer it was necessary to make the measurements on thicker layers of glass. The thermal conductivity values have been calculated from temperature distributions measured on the molten glass layer and from the temperature drops on the ceramic bottom of the furnace the thermal conductivity of which was known. From the physical point of view this is a steady-state comparative method with linear heat flow. The values of the effective thermal conductivity of four commercial glasses experimentally determined by this measuring procedure are compared to the radiative thermal conductivities computed from the measured absorption coefficients by means of Rosseland's diffusion approximation. The great differences between effective and radiative thermal conductivities, which have been found especially with weakly absorptive colorless glasses, are critically discussed.