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Full-Text Articles in Engineering

Phase Equilibrium Simulation And Its Application In Crystallization Processes , Weixin Song Jan 1991

Phase Equilibrium Simulation And Its Application In Crystallization Processes , Weixin Song

Retrospective Theses and Dissertations

Solid-liquid phase equilibrium information is essential to the research and development of crystallization processes. Computer simulation of the multicomponent solid-liquid equilibrium avoids the traditional tedious experimental determination;The phase equilibrium simulation requires an accurate thermodynamic model to describe the solution chemistry and a usable mathematical procedure to obtain reliable solutions: In this work, a modified activity coefficient model is presented. The modification makes the model more practical to use. A new numerical algorithm, which is based on a large-scale optimization technique is used for phase equilibrium calculation. This new method takes advantage of the thermodynamic properties of the solid-liquid equilibrium ...


Reduced Molybdenum Oxidation States In Hydrodesulfurization Catalysis By Chevrel Phases , Mark Eugene Ekman Jan 1991

Reduced Molybdenum Oxidation States In Hydrodesulfurization Catalysis By Chevrel Phases , Mark Eugene Ekman

Retrospective Theses and Dissertations

The catalytic activities of reduced (relative to Mo[superscript]4+) molybdenum sulfides, known as Chevrel phases, have been evaluated for thiophene and benzothiophene hydrodesulfurization (HDS) and 1-butene hydrogenation (HYD). These materials have been found to have HDS activities comparable to, or greater than, model unpromoted and cobalt-promoted MoS[subscript]2 catalysts; in contrast, Chevrel phases exhibit low activities for 1-butene HYD;X-ray powder diffraction and laser Raman spectroscopy analysis of the used (10 hours of thiophene reaction) catalysts indicated that the bulk structures were stable under reaction conditions. XPS analysis demonstrated that reduced molybdenum oxidation states were present at the ...


Numerical Studies Of Chemical Selectivity And Heat Transfer In Decaying Homogenous Turbulence , Mitali Chakrabarti Jan 1991

Numerical Studies Of Chemical Selectivity And Heat Transfer In Decaying Homogenous Turbulence , Mitali Chakrabarti

Retrospective Theses and Dissertations

This dissertation considers problems concerning (1) mixing and chemical reaction and (2) heat transfer, in a decaying, homogeneous turbulent flow. Direct numerical simulations have been used to compute the flows numerically in order to measure quantities that are difficult to measure in the laboratory and to test some statistical theories of turbulence by examination of the dynamical variables and their Statistics and Probability; These simulations involve solution of the unsteady Navier-Stokes and mass conservation equations by a pseudo-spectral method in 64[superscript]3, 80[superscript]3 and 128[superscript]3 wave-number domains. Part I deals with the problem of chemical ...


A Contribution To The Understanding Of Crystallization , Guenther Herbert Peters Jan 1991

A Contribution To The Understanding Of Crystallization , Guenther Herbert Peters

Retrospective Theses and Dissertations

Thermodynamic and kinetic studies of the vapor/liquid phase transition of a Lennard-Jones model fluid are presented which challenge the conventional interpretation of the mechanism of the condensation process. We have lifted the usual approximations (incompressible phases, constant surface tension, and non-depleting vapor phase) applied in classical nucleation theory to investigate the nature of the barrier to condensation. Based on the 1[superscript]st Yvon-Born-Green integro-differential equation we have developed a thermodynamically consistent molecular theory which accurately predicts the radially dependent surface tension and the location of the surface of tension of microscopically small droplets. The droplet size dependence of ...