The modelling of radiation heat transfer in forehearths units in glass melting

Abstract

The interaction between conduction, convection and radiation heat transfer in molten glass has been studied with specific reference to the forehearth units of a glass tank furnace. In shallow molten glass flows as typically encountered in forehearth units, the radiation-conductivity approach for modelling the radiative transfer process is found inappropriate. This is especially so for colourless glasses which are not optically thick below 2.8 microns. In the present work radiative heat transfer process in molten glass has been treated more rigourously by incorporating both optically thick and thin limits. The radiative interaction at the boundaries is treated more realistically. In the case of colourless glasses, the results obtained by the present method show the necessacity to account for the direct radiative interaction between the interior layers of the glass and refractory walls at the top and the bottom. The forehearth exit temperature profiles obtained by using the present method are quite different with those obtained using the radiation conductivity approach.