Radiative heat transfer in glass manufacture - One- and two-dimensional problems

Abstract

The one-dimensional radiation-conduction model, originally developed by Gardon, has been used to calculate: firstly, the rate of reheat of glass surfaces after forming in metal moulds, and secondly, the rate of temperature changes in glass in a forehearth following a step change in roof temperature. The extent of reheat at short times ( < 2 s) is not greatly dependent on the absorption properties of the glass but is much more so when the reheat time is long e.g. in hand working and in forming large articles. The forehearth temperature changes calculated by the "correct" radiation-conduction method are more rapid than those calculated by the "effective conductivity" method. A two-dimensional radiation-conduction model has been developed and used to calculate the rates of temperature change in glass in a forehearth. These calculations also show that the "effective conductivity" method is inadequate, especially when applied to time-dependent problems.