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Dissertation
Plasma discharge in water and its application for industrial cooling water treatment
Doctor of Philosophy (Ph.D.), Drexel University
Jun 2011
DOI:
https://doi.org/10.17918/etd-3651
Abstract
Plasma plays an important role in a wide variety of industrial applications, including material processing, semiconductor manufacturing, light sources, propulsion and many more. In recent years, there are increasing interests in the plasma discharges in liquids because of its potential applications for various biological, environmental, and medical technologies. For example, electric breakdown is developed as a non-chemical method for bio-fouling removal and contaminant abatement in water, with a potential for extension into a wide range of other water treatment applications. Comparing with other conventional water treatment technologies, plasma methods effectively combine the contributions of UV radiation, active chemicals, and high electric fields which leads to higher treatmentefficiency. However, the fundamental knowledge of the electric breakdown in water has not kept pace with these increasing interests, mostly due to the complexity of the phenomenon related to the plasma breakdown process. In most cases, the electric breakdown of liquids is initiated by the application of high electric field on the electrode, followed by rapid propagation and branching of plasma channels. Typically plasmas are only considered to exist through the ionization of gases and typical production of plasmas in liquids generates bubblesthrough heating or via cavitation and sustains the plasmas within those bubbles. The first part of the thesis tried to answer the question whether it is possible to ionize the liquid without cracking and bubble formation. Fast optical diagnostic platform was constructed with 500 ps time-resolution. It was demonstrated for the first time that the possibility of formation of non-equilibrium plasma in the liquid phase without bubble formation under nanosecond and subnanosecond high voltage excitation. The dynamics of excitation and quenching of non-equilibrium plasma in liquid water were investigated and it was observed that under some circumstances the plasma in liquid water possesses certain similarities as gas phase discharge. The second part of the thesis explores the application of underwater spark discharge for industrial cooling water treatment. Direct pulsed spark dischargetreatment was found to be able to accelerate the precipitation of calcium ions in supersaturated hard water. Possible pathways for the plasma-induced precipitationwere studied. Furthermore, the effect of pulsed spark discharges on the mitigation of mineral fouling in a concentric counterflow heat exchanger was investigated. The fouling resistances for the spark discharge treated cases dropped by 50 - 88% compared with those obtained for the no-treatment cases, depending on the initial hardness and flow velocity. The fouling resistance data confirmed that pulsed spark discharge was beneficial in mitigating the mineral fouling in heat exchangers by continuously producing suspended calcium carbonate particles in water.
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Details
- Title
- Plasma discharge in water and its application for industrial cooling water treatment
- Creators
- Yong Yang - DU
- Contributors
- Young I. Cho (Advisor) - Drexel University (1970-)Alexander A. Fridman (Advisor) - Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- College of Engineering (1970-2026); Mechanical Engineering (and Mechanics) [Historical]; Drexel University
- Other Identifier
- 3651; 991014632512704721