A theoretical and experimental investigation of copper electrode erosion in electric arc heaters: I. The thermophysical model

Abstract

A simple model is reported for copper electrode erosion in electric arc heaters as a result of electrode surface fusion by the action of the arc spot. In the analysis we substitute the real arc spot by an intensive moving surface heat source. The time evolution and the distribution of the electrode surface temperature within the arc spot is studied in coordinates coupled with the moving heat source. The electrode erosion is attributed in the model to the unbalance between the heat supply and the heat removal due to the development of an arc spot fusion zone. An erosion effective enthalpy is applied in the analysis, including all physical processes for the material transformation from the solid state into the plasma state under the action of the intensive heat flux. Formulae were obtained that enable one to calculate the electrode erosion as a function of arc velocity, electrode temperature, current, near-electrode thermal volt-equivalent, current density and electrode material properties. We show briefly that the theory agrees reasonably well with experimental results. The present model enables us to reveal the relative significance of the different parameters in the erosion process and to predict the erosion behaviour in copper electrode electric arc heaters.