Heat transfer in RF plasma sintering: Modeling and experiments |
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Authors: | N P Tandian E Pfender |
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Institution: | (1) Department of Mechanical Engineering and ERC for Plasma-Aided Manufacturing, University of Minnesota, 55455 Minneapolis, Minnesota;(2) Present address: Thermodynamic Research Laboratory, IUC-ES, ITB, Bandung, Indonesia |
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Abstract: | The mechanisms of heat transfer from an argon RF plasma, generated in a water-cooled quartz tube, to a sintering sample immersed
into the plasma and to the walls of the plasma torch have been studied both analytically and experimentally for pressures
from 1 to 50 torr. The model, based on the assumption of chemical equilibrium in a two-temperature plasma with rotational
symmetry, includes the influence of the magnetic field and of the Knudsen number on the thermal conductivity of the plasma.
At pressures below 20 torr heat transfer to the sintering sample is enhanced compared to heat transfer to the wall of the
plasma torch. This nonsymmetry is attributed to the Hall parameter and Knudsen number effect. The relative importance of the
two effects is a function of the pressure. A comparison with experiments, based on calorimetric and indirect heat transfer
measurements for a range of pressures and power levels, indicates satisfactory agreement with analytical predictions, with
the exception of larger discrepancies at higher power levels and relatively low pressures. For pressures below 5 torr, the
chemical equilibrium assumption becomes questionable, i.e., the sintering model underestimates the heat transfer to the sintering
sample. |
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Keywords: | RF plasma sintering reduced pressures effect on heat transfer Hall and Knudsen number effect |
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