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HEAT TRANSFER IN CONTINUUM AND NON-CONTINUUM PLASMA FLOWS IN MATERIALS PROCESSING APPLICATIONS

RAJAMANI, VIGNESH

Abstract Details

2005, MS, University of Cincinnati, Engineering : Mechanical Engineering.
Computational analysis of heat transfer in continuum and non-continuum plasma flow is presented in this thesis. First a continuum, laminar, mid-temperature range (1200K-1600K) plasma flow over a cylinder has been considered. The steady form of continuity and momentum conservation equations are solved in the plasma by a finite volume method. The conjugated transient heat transfer in the cylinder and in the plasma is obtained by simultaneous solution of the transient energy conservation equations. The ion and electron fluxes at the solid surface and the self-consistent electric field are evaluated. An inverse heat transfer problem is considered by using available experimental measurements of temperature rise in the cylinder to characterize the degree of ionization in the plasma flow. Comparing computational predictions of heat transfer in plasma flow with those for air flow, it is shown that the heat transfer to the cylinder is higher from plasma flow than that in flow of unionized air under identical flow and temperature conditions. The enhancement of heat transfer in plasma is due to the energy deposited at the solid surface by charged species during recombination reaction at the solid surface. An important finding is that even a small degree of ionization (< 1%) provides significant enhancement in heat transfer. This enhancement in heat transfer can lead to productivity increase in materials processing applications using mid-temperature convective plasma devices. When small particles are introduced in plasma flow, the ratio of mean free path to particle radius, which is known as the Knudsen number (Kn), may not be very small. As such a continuum treatment is not valid under such conditions. In the second part of this thesis, heat transfer to a spherical solid particle from a non-continuum stagnant plasma is considered. A kinetic theory formulation is developed by considering two-sided velocity and temperature distributions for neutral molecules. Governing equations obtained by taking moments of the Boltzmann equation are solved by a Newton-Raphson method along with a shooting technique and a fourth-order Runge-Kutta method. The temperature distribution in the plasma and heat transfer to the particle is obtained at different Knudsen numbers. Results show that the model accurately captures both continuum (Kn 0) and free-molecular regimes (Kn) and the agreement with available experimental data for heat transfer in the entire range of Knudsen number is excellent. The heat transfer to the particle decreases with increase in Knudsen number. The model is used to ascertain validity of the commonly used temperature jump approximation in non-continuum flows. It is shown that the temperature jump approach can be used under near-continuum conditions (Kn < 0.1) and the predictions of heat transfer by this approximation deviate significantly from the developed model. The model developed here can predict the heat transfer in the entire range of Knudsen number and can be applied to accurately evaluate plasma heat transfer in plasma-aided manufacturing applications involving small length scales.
Dr. Milind Jog (Advisor)
103 p.

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Citations

  • RAJAMANI, V. (2005). HEAT TRANSFER IN CONTINUUM AND NON-CONTINUUM PLASMA FLOWS IN MATERIALS PROCESSING APPLICATIONS [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1130076192

    APA Style (7th edition)

  • RAJAMANI, VIGNESH. HEAT TRANSFER IN CONTINUUM AND NON-CONTINUUM PLASMA FLOWS IN MATERIALS PROCESSING APPLICATIONS. 2005. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1130076192.

    MLA Style (8th edition)

  • RAJAMANI, VIGNESH. "HEAT TRANSFER IN CONTINUUM AND NON-CONTINUUM PLASMA FLOWS IN MATERIALS PROCESSING APPLICATIONS." Master's thesis, University of Cincinnati, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1130076192

    Chicago Manual of Style (17th edition)