Transmission of Radiation through Glass in Tank Furnaces

JSGT 1952 V36 T115-T123

The mechanism of absorption and re-radiation of energy suggested in 1947 by F. W. Preston as a means by which heat is carried through hot glass is analysed mathematically. Steady heat flow by radiation in a tank furnace can be regarded with sufficient accuracy as being due to a “radiation conductivity. "The temperature gradients and bottom temperatures deduced from this model, both for experimental and large-scale tank furnaces containing different glasses, are compared with the observations of R. Halle and W. E. S. Turner and good agreement is found. It is concluded, first, that radiation heat flow is very important, giving for sheet glass at 1200°C a total effective conductivity about fifty times the ordinary thermal conductivity; and secondly, that the differences in infra-red absorption amongst coloured glasses can affect the radiation heat flow sufficiently to explain the different heat transparencies of coloured glasses at melting temperatures.

B. S. Kellett