Particle heating in a radio-frequency plasma torch

Abstract

A numerical model was developed to predict the behavior of a particle in a radio-frequency (rf ) plasma. The analysis obtained the heat, mass, and momentum transfer of a single particle injected into an rf plasma. The governing equations for vaporization of a liquid particle were taken from the model which was used to simulate the vaporization process of liquid droplets in a rocket combuster. All the thermodynamical and transport properties were calculated as functions of temperature in order to simulate the actual behavior more precisely. The boundary conditions are a finite temperature at the particle center and a heat balance at the particle surface. Thermodynamical equilibrium at the particle surface was always assumed. ’’Moving-boundary problems’’ in the case of melting or vaporizing processes were solved by the use of a ’’moving grid system’’. Four sizes of iron particles injected into the rf argon plasma have been computed: r0=20, 40, 60, and 80 μ. The iron particles with radii less than 70 μ could be melted under the assumed plasma conditions. It was found that the potentiality as concerns powder processing of an rf plasma was overestimated by previous models.

Numerical Modelling of an Anodic Metal Bath Heated with an Argon Transferred Arc

“…It is assumed that the condensation occurs when the partial pressure of the iron vapour is larger than the saturated vapour pressure. 12) In this case, a new iron vapour concentration is estimated by using this saturated vapour pressure.…”

“…V a , f a and L Fe are the anode fall set at 3.5 V, the work function of the anode material equal to 4.5 V, and the latent heat of vaporisation of iron. 12) The study of the arc-anode interactions needs the knowledge of F v , the rate of vaporisation or condensation of the electrode material. This rate has to consider the background pressure, the anode material and the convection and diffusion of the vapour in the surrounding plasma.…”

Applications physico-chimiques des plasmas d'arc

“…6 [194] (1974), Yoshida [208] (1977) et Gal-Or [215] (1980), soit des modèles à deux dimensions : Boulos [196] (1974) et [190] (1978), Battacharyya et Gauvin [202] (1975), Fiszdon [211] (1975) et [212] (1979). Un seul modèle ultra simplifié tente de prendre en compte les interactions entre les particules ou plus précisément de déterminer dans quelles conditions on peut les négliger, c'est celui de Mathieu [199] (1979).…”

“…b) Quelques phénomènes à prendre en compte. -Pour la modification des propriétés de la couche lors de l'évaporation de la particule, l'hypothèse la plus simple consiste à supposer que le flux de vapeur issu de la particule se mélange au plasma qui l'entraîne modifiant ainsi les propriétés de transport et Yoshida [208] suggère de [221,222,195], où toujours pour des particules d'alumine, il a été montré [195] que la diminution du transfert de chaleur était de plus de [217].…”

Thermal Treatment of Granulated Particles by Induction Thermal Plasma

“…Thus, for numerical investigation it is the challenge to predict the trajectory and temperature history of the particles injected into the ITP torch. Among others Yoshida et al [Yoshida, 1977] pioneered the modeling of particle heating in induction plasmas; though their work assumed the particle trajectory along the centerline of the torch only. Boulos [Boulos, 1978] developed a model and comprehensively discussed the thermal treatment of alumina powders in the fire ball of argon induction plasma.…”