STEADY AND TRANSIENT, MULTI-DIMENSIONAL SOLUTIONS FOR MELTING OR FREEZING AROUND A BURIED TUBE IN A SEMI-INFINITE MEDIUM.
Item
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Title
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STEADY AND TRANSIENT, MULTI-DIMENSIONAL SOLUTIONS FOR MELTING OR FREEZING AROUND A BURIED TUBE IN A SEMI-INFINITE MEDIUM.
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Identifier
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AAI8601710
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identifier
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8601710
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Creator
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ZHANG, GUO-PING.
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Contributor
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Latif M. Jiji
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Date
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1985
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Language
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English
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Publisher
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City University of New York.
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Subject
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Engineering, Mechanical
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Abstract
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This thesis examines melting or freezing around a buried fluid-carrying tube in a semi-infinite region. Of particular interest is the behavior of the phase change interface and the time variation of the axial temperature distribution in the fluid. Steady state and transient three-dimensional solutions are presented which account for the thermal interaction between a moving fluid and a phase change material having a free surface in the vicinity of the tube. The peripheral variation in the tube surface temperature is neglected and axial variation is left unspecified and is determined by the thermal interaction with the surrounding two-phase medium. Axial conduction is neglected throughout the system.;Different solution methods based on the quasi-steady approximation are used depending on whether the phase change front commences at the tube wall or the plane free surface.;In the former case, a so-called apparent free surface method is developed for a corresponding two-dimensional problem using a locally two-dimensional conformal mapping technique. The approximate analytic solution agrees very well with existing numerical results. The method is extended to include the axial thermal interaction and the three-dimensional solution reveals an important fact which has not been described in the previous two-dimensional studies. The long time required for the isotherms and thaw boundary above the tube to approach equilibrium is not controlled by the conduction process in this region but by the much slower variation in tube wall temperature.;A more general numerical method, the boundary integral technique, is employed for the second type of problem where the interface is generated at the free surface. Since the omission of the sensible heat can significantly influence the interface shape in this case, an artificial movable bottom boundary is used in the contour integral to reduce these effects. The solutions are presented for two-dimensional problems; however, the extension to three-dimensions is straightforward and follows in the same manner as when phase change starts at the tube wall.;The final equilibrium for both cases is identical. A new closed-form approximate analytic solution is obtained to describe the three-dimensional asymptotic state.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
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Program
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Engineering
