dc.contributor.advisor |
Chen, J. |
en |
dc.contributor.advisor |
Chen, D. |
en |
dc.contributor.author |
Chen, Zhengdong |
en |
dc.date.accessioned |
2020-06-02T04:32:26Z |
en |
dc.date.available |
2020-06-02T04:32:26Z |
en |
dc.date.issued |
1997 |
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dc.identifier.uri |
http://hdl.handle.net/2292/51040 |
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dc.description |
Full text is available to authenticated members of The University of Auckland only. |
en |
dc.description.abstract |
Oscillating interfaces or interfaces undergoing wave motion are encountered in several metallurgical processes; examples include the gas/slag and slag/metal interface in the tundish of a continuous casting machine, the gas/electrolyte and electrolyte/metal interface in a Hall-Heroult aluminium reduction cell. Literfacial oscillation or wave movement significantly alters the local flow characteristics and heat/mass transport process, and thus may directly affect the refractory corrosion behaviour and the service life of the equipment, hr this work, experimental, analytical and numerical studies were carried out to investigate the heat and mass transfer characteristics near an oscillating interface or an interface undergoing wave motion. Heat transfer experiments using oscillating air/water and air/propylene glycol aqueous solution systems show significant enhancement of heat transfer on the solid surface near an oscillating interface. Experiments using an air/water interfacial wave system and an oscillating air/liquid interface system give similar results under the same oscillation amplitude and frequency. A simple analysis shows that the flow fields between these two types of interfacial disturbances are similar. By measuring the dissolution rate of benzoic acid in water, the mass transfer characteristics near an air/water wavy interface were investigated for large Schmidt numbers. It was found that for the same average velocity, the mass transfer rate near a wavy interface might be up to three times that of uni-directional flows. A unified correlation was developed for both the heat and the mass transfer coefficients near an oscillating interface or an interface undergoing wave motion. Visualisation studies using dye traces provided some details of the flow fields and transport characteristics near an oscillating air/water interface. Vortices are formed and developed near the oscillating interface and the process of vortex formation and dissipation were related to the downward and upward strokes of the liquid surface movement. The high local heat/mass transfer near an oscillating interface is due primarily to the periodic and efficient renewal of the liquid in the wall boundary regions. Based on the visualisation studies, an approximate analysis was carried out for the heat/mass transfer process near an oscillating gas/liquid interface. The predicted heat/mass transfer coefficients are in good agreement with the experimental values obtained in this work. Numerical simulations were conducted for the flow fields and heat transfer from a discrete heated surface located on the wall of a two-dimensional channel to an oscillatory laminar flow. The PHOENICS code used was verified by an independent CFD code developed in this work as well as using analytical solutions. It was found that compared to the steady uni-directional flow, the enhancement of heat transfer due to an oscillatory flow is small in the linear laminar flow region. Under certain conditions, the heat transfer due to oscillatory flows may even be smaller than that of uni-directional flow. Using the Height Of Liquid (HOL) method, numerical simulations had also been carried out to investigate the flow fields and heat transfer characteristics near an oscillating interface. The flow fields and heat transfer results obtained are in reasonable agreement with the visualisation studies and the experimental values obtained in this work. |
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dc.publisher |
ResearchSpace@Auckland |
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dc.relation.ispartof |
PhD Thesis - University of Auckland |
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dc.relation.isreferencedby |
UoA9975451714002091 |
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dc.rights |
Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. |
en |
dc.rights |
Restricted Item. Full text is available to authenticated members of The University of Auckland only. |
en |
dc.rights.uri |
https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm |
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dc.title |
Heat and mass transfer near an oscillating interface |
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dc.type |
Thesis |
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thesis.degree.discipline |
Chemical and Materials Engineering |
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thesis.degree.grantor |
The University of Auckland |
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thesis.degree.level |
Doctoral |
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thesis.degree.name |
PhD |
en |
dc.rights.holder |
Copyright: The author |
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dc.identifier.wikidata |
Q112850804 |
|