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High Temperature Material Processes: An International Quarterly of High-Technology Plasma Processes
SJR: 0.137 SNIP: 0.341 CiteScore™: 0.43

ISSN Druckformat: 1093-3611
ISSN Online: 1940-4360

High Temperature Material Processes: An International Quarterly of High-Technology Plasma Processes

DOI: 10.1615/HighTempMatProc.v4.i1.20
22 pages

THERMODYNAMIC AND TRANSPORT PROPERTIES OF THERMAL PLASMAS

Pierre Fauchais
Laboratoire Sciences des Procedes Ceramiques et de Traitements de Surface UMR CNRS 6638 University of Limoges 123 avenue Albert Thomas, 87060 LIMOGES - France
M. F. Elchinger
SPCTS University of Limoges, 123 av. A. Thomas, 87060 Limoges cedex, France
Jacque Aubreton
SPCTS University of Limoges, 123 av. A. Thomas, 87060 Limoges cedex, France

ABSTRAKT

The requirements for thermodynamic and transport properties are illustrated through an example: a d.c. spraying plasma torch used either for spraying or thermal plasma CVD. First the problems involved in calculating thermodynamic properties of complex molecules existing at temperatures below 3000 K are recalled and a few examples of thermodynamic properties are presented. The way to introduce non equilibrium by a multi-temperature "pseudo-equilibrium" is then discussed and the results compared with kinetic or pseudo-kinetic calculations. The calculation of transport properties, except for diffusion, can be performed easily in multiple temperatures "pseudo-equilibrium" provided the interaction potentials are known, which at the moment is limited to a few simple gas mixtures. Examples of the influence of multiple temperatures and the poorly known interaction potentials are presented. The difficulties involved in calculating diffusion at equilibrium are recalled, and the interest of such calculations is highlighted with the example of an Ar-H2 d.c. arc. The calculations of a plasma flow illustrate the necessity of using simple mixing rules but also their limitations. Finally, the relative importance of the uncertainties in transport and thermodynamic properties is shown compared to the influence of turbulence or the changing of the calculation from 2 to 3 dimensions.