The effect of ionization on heat transfer to wires immersed in a highly thermallyionized plasma

Abstract

Results obtained with a previously developed technique for measuring local heat transfer to bare and ceramic coated metal wires from a dense, highly thermallyionized plasma are presented and compared with theoretical predictions. A free-burning arc in argon at atmospheric pressure provides a plasma in local thermodynamic equilibrium. Wire probes are swept through this plasma in planes parallel to the anode. The wires do not draw a net current from the plasma. Experimental evidence indicates that the layer between the undisturbed plasma and the probe surface is not in chemical equilibrium. The data show that heat transfer . to the wire in this situation is dominated by the energy transport associated with electron and ion partial currents to the probe surface as determined by the potential of the probe with respect to the plasma. The data obtained using this technique provide an experimentally verified model for the heat transfer to wires immersed in a plasma over a wide range of plasma conditions including a 100 percent variation in the degree of ionization.

Experimental and analytical aspects of plasma heat transfer

“…4 are due to the variance in the inversion technique. Circumferentially averaged heat fluxes are about 60 watt/ram 2 in the center, in excellent agreement with data of [2,3,4]. Since Petrie [2] was unable to obtain satisfactory measurements with coated wires, this comparison refers only to bare metal surfaces.…”

“…Previous heat transfer studies in similar situations have been reported by Kimura and Kanzawa [1], Petrie [2], and Petrie and Pfender [3,4]. These authors measure the heat flow to cylindrical bodies immersed into an arc plasma.…”

“…In Refs. [2,3,4], an arc plasma of similar properties is utilized and a heat transfer model is proposed which takes the fact into account that the wire probe is not floating locally over its entire length. Together with his model and the average floating heat transfer data, an inversion of the data similar to the Abel inversion is applied to obtain local heat fluxes to a locally floating tube.…”

The decomposition kinetics of molybdenite in an argon plasma

“…This was observed by Chludzinski et al (1965), Kimura andKanzawa (1965), andPetrie (1969). The argon plasma tail flames used in this work, however, reached only about 8 000°K.…”

Motion of particles entrained in a plasma jet

“…In order to calculate mean film temperatures, the particle surface temperature was required. This was calculated using the Ranz-Marshall ( 1952) correlation corrected for nonisothermal effects (Ahmed, 1967), ionization effects (Petrie, 1969), and recombination effects (Chludzinski, 1964). The latter correction was necessary due to the entrainment of considerable quantities of air by the hot argon jet.…”