Heat transfer, thermal conductivity, and emissivity of Hall-Heroult top crust

Abstract

Samples of top crust were prepared in the laboratory, using various bath compositions and temperatures and with variable mixing ratios of alumina/crushed anode cover. The temperature gradient and the heat flux through the crust and the loose alumina mixture were studied, and it was found that the heat flux increased strongly with increasing contents of crushed anode cover in the mixture, due to increased thermal conductivity of the material. Across the air-filled gap between the bath surface and the crust the heat is mainly carried by infra-red radiation, and the investigations showed that the emissivity of the downward-facing crust surface increased slightly with increasing contents of crushed anode cover in the mixture.