Measurement of anode falls and anode heat transfer in atmospheric pressure high intensity arcs

Electric probe measurements have been performed at and close to a plane, water-cooled anode surface in atmospheric pressure, high intensity argon arcs for different arc configurations which in turn, result in two distinctly different anode arc roots (diffuse and constricted). An adjustable fine wire probe penetrating through a small hole in the center of a flat anode allows for potential and electron temperature measurements in the anode boundary layer. For the parameter range covered by this investigation (100 A≤I≤250 A) the results reveal negative anode falls ranging from approximately −2.1 to −1.4 V. Electron temperatures at the anode surface range from 8800 to 9800 K. Calorimetric energy balances from which the contributions of the various modes of heat transfer to the anode may be derived, indicate the importance of convective heat transfer to the anode. The results of the calorimetric studies as well as of the anode fall measurements are consistent with a revised anode heat transfer model which takes negative anode falls into account.