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RESEARCH PAPERS: Heat Transfer in Manufacturing

Effects of Plasma Parameters on the Temperature Field in a Workpiece Experiencing Solid-Liquid Phase Transition

[+] Author and Article Information
F. B. Yeh1

Department of Marine Mechanical Engineering, Chinese Naval Academy, P. O. Box 90175, Tsoying, Kaohsiung, Taiwan, ROCfbyeh@mail.cna.edu.tw

P. S. Wei

Department of Mechanical and Electro-Mechanical Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan, ROC

1

Corresponding author.

J. Heat Transfer 127(9), 987-994 (Apr 27, 2005) (8 pages) doi:10.1115/1.1999653 History: Received January 22, 2004; Revised April 27, 2005

The heat transfer characteristics of a workpiece subject to plasma heating and melting are theoretically and systematically studied. Plasma etching, spray deposition, sputtering, cutting and surface treatment, etc., are usually controlled by energy transfer from plasma to workpieces. In this work, the one-dimensional unsteady conduction equation accounting for solid-liquid phase transition with distinct thermal properties in a workpiece is solved. The plasma is composed of a collisionless presheath and sheath on an electrically floating workpiece that partially reflects or secondarily emits ions and electrons. The energy transport from plasma to the surface is kinetically, analytically and exactly calculated from self-consistent velocity distributions of the ions and electrons. The results show that the predicted surface temperature and energy transmission factor agree well with experimental data. The effects of plasma characteristics and thermal parameters of the workpiece on unsteady temperature profiles and thickness of the molten layer in the workpiece are quantitatively provided in this work. Energy released from recombination of the ions and electrons on the surface is found to play the most important role on heating the workpiece. The deviation of surface temperature contributed by recombination energy can be 1000 K.

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Copyright © 2005 by American Society of Mechanical Engineers
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Figures

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Figure 1

System sketch for the physical model and coordinates

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Figure 2

A comparison between the measurements (25) and predicted energy transmission factor as a function of dimensionless wall potential

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Figure 3

A comparison between the measurements (26) and predicted surface temperature of a workpiece as a function of time

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Figure 4

Dimensionless surface temperature of a workpiece as a function of time for different reflectivities of ions and electrons, ion-to-electron mass ratios, charge numbers, and electron-to-ion source temperature ratios

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Figure 5

Dimensionless thickness of the molten layer in a workpiece as a function of time for different reflectivities of ions and electrons, ion-to-electron mass ratios, charge numbers, and electron-to-ion source temperature ratios

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Figure 6

Dimensionless surface temperature of a workpiece as a function of time for different Stefan numbers, dimensionless liquid conductivities, melting temperatures, and plasma flow work-to-heat conduction ratios

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Figure 7

Dimensionless thickness of the molten layer in a workpiece as a function of time for different Stefan numbers, dimensionless liquid conductivities, melting temperatures, and plasma flow work-to-heat conduction ratios

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Figure 8

Dimensionless temperature in a workpiece for different dimensionless times

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Figure 9

Dimensionless temperature in a workpiece at a dimensionless time τ=1.5 for different reflectivities of ions and electrons, ion-to-electron mass ratios, charge numbers, and electron-to-ion source temperature ratios

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Figure 10

Dimensionless temperature in a workpiece at a dimensionless time τ=1.5 for different Stefan numbers, dimensionless liquid conductivities, melting temperatures, and plasma flow work-to-heat conduction ratios

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Figure 11

Dimensionless surface temperature of a workpiece as a function of time for different dimensionless ionization energies

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Figure 12

Dimensionless thickness of the molten layer in a workpiece as a function of time for different dimensionless ionization energies

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