A THEORETICAL AND EXPERIMENTAL INVESTIGATION OF COPPER ELECTRODE EROSION IN ELECTRIC-ARC HEATERS .1. THE THERMOPHYSICAL MODEL

A simple model is reported for copper electrode erosion in electric ar e heaters as a result of electrode surface fusion by the action of the are spot. In the analysis we substitute the real are spot by an inten sive moving surface heat source. The time evolution and the distributi on of the electrode surface temperature within the are spot is studied in coordinates coupled with the moving heat source. The electrode ero sion is attributed in the model to the unbalance between the heat supp ly and the heat removal due to the development of an are spot fusion z one. An erosion effective enthalpy is applied in the analysis, includi ng all physical processes for the material transformation from the sol id state into the plasma state under the action of the intensive heat flux. Formulae were obtained that enable one to calculate the electrod e erosion as a function of are velocity, electrode temperature, curren t, near-electrode thermal volt-equivalent, current density and electro de material properties. We show briefly that the theory agrees reasona bly well with experimental results. The present model enables us to re veal the relative significance of the different parameters in the eros ion process and to predict the erosion behaviour in copper electrode e lectric are heaters.