Multiscale molecular simulations of heat and mass transfer at multiphase flow interfaces
Item
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Title
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Multiscale molecular simulations of heat and mass transfer at multiphase flow interfaces
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Identifier
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d_2009_2013:5ccf38e5915a:10597
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identifier
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10873
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Creator
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Gu, Kai,
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Contributor
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Charles B. Watkins | Mumtaz K. Kassir
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Date
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2010
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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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Mechanical engineering | condensation | Direct Simulation Monte Carlo | gas flow | Molecular Dynamics | mutliphase
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Abstract
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Molecular simulation is employed to investigate heat and mass transfer at multiscale, multiphase flow interfaces for solid-gas, liquid-vapor and solid-liquid-vapor interfacial systems in argon. The multiscale systems considered involve a gas/vapor Knudsen layer with a length scale on the order of several mean free paths over an interface with nanoscale molecular interactions between the gas and the condensed phase. To improve simulation efficiency for such systems, a multiscale hybrid method for coupling the direct simulation Monte Carlo (DSMC) method to the nonequilibrium molecular dynamics (NEMD) method is introduced. It incorporates a new, modified generalized soft sphere (MGSS), DSMC molecular collision model to improve the poor computational efficiency of the traditional generalized soft sphere GSS model and to achieve DSMC compatibility with the Lennard-Jones molecular interactions of the NEMD method. Both equilibrium and nonequilibrium gas-solid systems are simulated to validate the method. For liquid-vapor interfaces, physically consistent procedures are developed to define the boundaries of the interphase region between the liquid and vapor phases, which can be applied to equilibrium or nonequilibrium systems. Simulations of liquid-vapor equilibrium systems are performed to demonstrate the improved precision of this new method over alternative methods. The new hybrid molecular simulation method and interphase boundary definitions are employed to study the condensation of saturated argon vapor flowing tangentially across a stationary cooled substrate, at nanoscale resolution. Unsteady and quasi-steady interfacial properties and heat and mass transfer parameters are analyzed. Results within the Knudsen layer are compared with kinetic theory analytical and molecular simulation results.
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Type
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dissertation
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Source
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2009_2013.csv
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degree
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Ph.D.
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Program
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Engineering
