Determination of Streaming Velocity and the Flow of Heat and Mass in High-Current Arcs

Abstract

Arc plasma streaming velocities were calculated from previously unpublished experimental data obtained by H. N. Olsen on total pressure distributions at the anodes in 100- to 300-amp argon and helium arcs. The dynamic streaming component of pressure was calculated by subtracting the magnetic component (due to the self-magnetic field of the arc) from this total pressure. Arc temperatures also measured by Olsen were then used to calculate densities and heat contents of the plasma, and these were used with the streaming pressure to calculate velocities and mass and heat flow distributions. These in turn were integrated to give total mass and heat flows. The results compare reasonably with other measurements and estimates in the literature. Peak velocities range from 16 000 to 60 000 cm/sec, mass flows from 0.04 to 0.23 g/sec. The plasma heat flow distribution shows a close similarity in shape to values of heat transfer intensity at the anode measured by O. H. Nestor. A comparison of the total heat flow in the plasma to the total heat transfer due to streaming at a series of currents shows heat transfer proportional to (heat flow)0.62 which agrees with correlations used for heat transfer from gases and flames. A simplified model of arc pumping is presented which suggests that heat and mass flow should increase as (current)32. A simple analog experiment in mercury is described which illustrates graphically the streaming caused by a divergent current path in a conductor.