Ceramics-Silikáty 44, (1) 20 - 25 (2000)

The method of three-dimensional mathematical modelling by means of CFD program FLUENT was used to find the influence of means of intensification upon technological characteristics of glass melting furnaces. Two physical means, i.e. a mechanical barrier and melting tank insulation (or heat losses through walls and bottom) were selected to intensify a melting process. Technological characteristics were defined by the magnitude and shape of temperature and velocity fields and by the volume of glass melt with the temperature lower than the temperature liquidus. The results of mathematical modeling have shown the considerable influence of the pull of the furnace, of the magnitude of thermal losses through the walls and the bottom and of the height of a mechanical barrier. The temperature of glass melt flowing into the throat is increased by a height of a barrier and decreased by heat losses. The temperature 1200 °C which corresponds with glass melt viscosity h = 103 dPa s was considered to be the lowest limit of the temperature of glass melt coming to a throat. Variants with this temperature lower then 1200 °C have not satisfied this evaluating criterion. The velocity of the glass melt flowing into the throat is increased by the pull of the furnace (18 t day⁻¹ corresponds with 9.38 × 10⁻⁴ m s⁻¹; 50 t day⁻¹ corresponds with 2.62 × 10⁻³ m s⁻¹) and by the heat losses. The heat losses also influence the volume of ”dead areas” (the higher the heat losses the larger the ”dead areas”). Only the variants with a = 1 W m⁻² K⁻¹ and two variants with a =3Wm⁻² K⁻¹ have satisfied the criterion of zero ”dead areas”. The height of a barrier influences the shape of velocity pro-files, i.e. the presence of the backward current. If this height h = 0.75 m, the return current cannot be observed. On the other hand, the mechanical barrier with the smallest height h = 0.375 m actually did not influence the current in a melting tank. All the above mentioned evaluating criteria have been satisfied by only 17 variants from the whole number of 92 investigated ones. The investigated glass melting furnace should be operated with very low coefficient of heat transfer at walls and bottom. The pull of the furnace can be kept at 40 t day⁻¹. The height of a mechanical barrier should range between 0.5 m and 0.625 m from the furnace bottom. Significant influence of distance between a mechanical barrier and a charge wall has not been proved, so the barrier can be situated across the melting tank with the proximity 4.75 – 5.5 m to the frontal charge wall.