Engineering Commons^™

Kinetic Mechanism Of The Reactions Of Dichloromethane And Chloroform With Atomic Hydrogen At Low Pressure And Room Temperature, Jia-Ling Linda Young

Theses

The reaction mechanism of dichloromethane reaction (DCM) with atomic hydrogen in a flow reactor at room temper¬ature (300 K) and low pressure (2.1 - 2.7 torr), argon bath gas, has been developed in this research to analyze the above reaction system. The important addition reactions of radicals (or atoms) to olefins and the radical/radical (atom/radical) combination reactions have been analyzed using the bimolecular version of the Quantum-Rice-Ramsperger-Kassel (QRRK) theory.

The detailed reaction mechanism satisfactorily fits the experimental data for the reagent (DCM) conversion from previous experimental over a initial ratio (atomic hydrogen to dichloromethane) range of 6.8 to 40. The …

Stability Of Poiseuille-Couette Flow Between Concentric Cylinders, J H. Scholtz, Hendrik J. Viljoen, C J. Wright

Papers in Fluid Mechanics

The stability of laminar flow between concentric cylinders is analyzed. Conhinrd Poiseuille and Couette flows are considered. It is shown that instabilities exist if the laminar flow is synnetric or near-spaetric on part of the annulus. Instabilities are reported for aspect ratios as small as q = 0.001.

Asymptotic Boundary-Layer Solutions For Mixed Convection From A Vertical Surface In A Micropolar Fluid, Rama Subba Reddy Gorla, Paul P. Lin, An-Jen J. Yang

Mechanical Engineering Faculty Publications

Using the theory of micropolar fluids due to Eringen, asymptotic boundary layer solutions are presented to study the combined convection from a vertical semi-infinite plate to a micropolar fluid. Consideration is given to the region close to the leading edge as well as the region far away from the leading edge. Numerical results are obtained for the velocity, angular velocity and temperature distribution. The missing wall values of the velocity, angular velocity and thermal functions are tabulated. Micropolar fluids display drag reduction and reduced surface heat transfer rate when compared to Newtonian fluids.

Enzyme- Facilitated Transport And Separation Of Organic Acids Through Liquid Membranes, David C. Rethwisch, Anuradha Subramanian, Gao Yi, Jonathan S. Dordick

Papers in Biotechnology

The selective separation of organic acids is important for the production of numerous biologially functional rnuleculcs, including amino acids, peptidcs, fats, and pharmaceuticals.' Enzyme, specificalty lipases and proteases, have been used to selectively separate a variety of organic acids; however, multiple steps are usually required,Vn additiun, carbonic anhydrase has been usd in a variety of Eiquid membranes for transport of CO2.) In the present study, we have coupled the selectiviey of enzymes with liquid membranes to provide a single-step method to scicctiveiy separate and purify organic acids.

Increased Separation By Variable-Temperature Stepwise Desorption In Multicomponent Adsorption Processes, Suvit Kulvaranon, Marshall E. Findley, Athanasios I. Liapis

Chemical and Biochemical Engineering Faculty Research & Creative Works

When more components than desired are adsorbed, adsorption-desorption separation processes may not be satisfactory. However, in the cases of ethanol and water adsorption on activated carbon, propane and propylene adsorption on molecular sieves, and hydrogen sulfide, carbon dioxide, and propane adsorption on molecular sieves, it has been found that a variable-temperature stepwise desorption (VTSD) procedure following the adsorption stage can significantly increase the degree of separation achieved compared to a complete desorption of all adsorbed components. Studies indicate that these increased separations are in part due to nonequilibrium effects. An estimation of economic factors in separating low concentration propylene in …

Conductivity Of N-Dimensional Composites Containing Hyperspherical Inclusion, Ashok S. Sangani

Biomedical and Chemical Engineering - All Scholarship

A problem of determining the macroscopic or effective thermal conductivity of an N-dimensional composite medium containing N-dimensional nonoverlapping hyperspherical inclusions is considered. Since the macroscopic conductivity is expected to become less sensitive to the detailed spatial distribution of the inclusions for N ≥ 4, only the special case of periodic arrangement of the inclusions is considered. An expression for the macroscopic conductivity correct to O(χ3N + 8), χ being the ratio of "diameter" of the inclusions to the spacing between them, is derived and the numerical results for the conductivity are presented as a function of χ and N for …

A Simple Model For A Zinc/Bromine Flow Cell And Associated Storage Tanks, G. D. Simpson, Ralph E. White

Faculty Publications

A simple model for a parallel plate, zinc/bromine flow cell and associated storage tanks is presented and used to make time-dependent predictions for various quantities in the system. The model is based on a previously published algebraic model of the cell at steady-state and time-dependent, first-order differential equations for the storage tanks. The Butler-Volmer equation is used for the electrochemical reactions, and the homogeneous reaction between bromine and bromide is included. The model predictions indicate that the charging operation of a zinc/bromine battery can be significantly improved by using a storage tank with a larger residence time for the bromine …

Mathematical Modeling Of An H2s Removal Electrolyzer, Z. Mao, P. Adanuvor, Ralph E. White

Faculty Publications

A mathematical model is presented for a high temperature H₂S electrolyzer. It is shown that the maximum current in this type of a cell is determined entirely by the transport rate of sulfide ions through the separator. It is suggested that this model could be used to determine the feasibility of various designs for this electrolyzer.

Electrochemical Behavior Of Graphite And Ni-Cr Electrodes In Sodium Polysulfide In The Absence And Presence Of Hydrogen Sulfide, Z. Mao, Ralph E. White, B. Dandapani, A. Anani, S. Srinivasan, A. J. Appleby

Faculty Publications

The electrochemical behavior of graphite and Ni-Cr electrodes in sodium tetrasulfide melt has been investigated using voltammetric, chronoamperometric, and chronopotentiometric techniques in the presence and absence of hydrogen sulfide. Two continuous phases, namely, Na₂S₂ and Na₂S, are apparently formed at different potentials during the cathodic polarization. The blocking effect by these layers was much less significant on the Ni-Cr electrode than on graphite. The presence of H₂S did not appear to influence the electrode reactions, but it significantly reduced the rate of formation of the continuous phases (Na₂S₂ or Na …

A Computer Simulation Of The Oxygen Reduction Reaction In Carbonate Melts, P. K. Adanuvor, Ralph E. White, A. J. Appleby

Faculty Publications

A computer simulation of the oxygen reduction reaction in various carbonate melts has been carried out under steady-state conditions on the basis of a proposed kinetic model which takes into consideration the autocatalytic reaction involving oxygen and other reducible oxygen species in the melt, and the neutralization of oxide ions by dissolved carbon dioxide. A simulation of the presence of (physically) dissolved oxygen, in the diffusion layer region of the melt, corresponding to the possible situation in porous electrodes, causes a significant enhancement in the polarization curves, particularly in the mass-transfer control region. On the other hand, high levels of …

Estimation Of The Diffusion Coefficient And Solubility For A Gas Diffusing Through A Membrane, Michael C. Kimble, Ralph E. White, Yu-Min Tsou, R. Neal Beaver

Faculty Publications

Analysis of the data obtained by the electrochemical monitoring technique for diffusion of a gas through a membrane is considered. It is shown that combining a numerical method with a nonlinear parameter estimation technique provides a means to determine values for the diffusion coefficient and the solubility of the diffusing gas. It is shown that better accuracy can be obtained for the diffusion coefficient and solubility of this gas by using the method presented and all experimental data rather than only part of the data, as has often been done in the past.

Electrical Properties Of Hydrogenated Diamond, Sacharia Albin, Linwood Watkins

Electrical & Computer Engineering Faculty Publications

Hydrogen passivation of deep traps in diamond is demonstrated. Current‐voltage (I‐V) characteristics of polycrystalline thin film and bulk diamond were studied before and after hydrogenation. On hydrogenation, all the samples showed several orders of magnitude increase in conductivity. Hydrogenation was carried out under controlled conditions to study the changes in the I‐V characteristics of the samples. The concentration of uncompensated traps was varied systematically by hydrogenation. The concentration of electrically active hydrogen was determined from the I‐V data. It is shown that hydrogenation is an alternative to deep‐level transient spectroscopy, suitable for …

The Fractal Dimension As A Measure Of The Roughness Of Rock Discontinuity Profiles, Y. H. Lee, J. R. Carr, David J. Barr, Charles J. Haas

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

An important factor in the analysis of deformation and failure of rock masses along discontinuities is the roughness of the jointing surfaces. The fractal dimension is proposed as a method of objectively quantifying the roughness profile of such discontinuities. With this method much less engineering judgement and experience are required in determining the surface roughness,sb than is required for other methods such as the widely used joint roughness coefficient (JRC) suggested by the International Society for Rock Mechanics [1] (Int. J. Rock. Mech. Min. Sci. & Geomech. Abstr. 15, 319-368, 1978). The fractal dimension, suggested by Mandelbrot [2] (Fractals-Form, Chance …

Effect Of Viscoplastic Flow Rules On The Initiation And Growth Of Shear Bands At High Strain Rates, R. C. Batra, Chang-Soo Kim

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Marchand and Duffy have reported detailed measurements of the temperature and strain as a shear band develops in a HY-100 steel. Assuming their torsional tests in thin-wall tubes can be adequately modeled by a viscoplastic block undergoing overall adiabatic simple shearing deformations, we investigate the effect of modeling the viscoplastic response of the material by a.power law, and flow rules proposed by Litonski, Bodner and Partom, and Johnson and Cook. Each of these flow rules is first calibrated by using the test data at a nominal strain-rate of 3300 s-1. Then predictions from the use of these flow rules at …

Predicted Secondary Current Distributions For Linear Kinetics In A Modified Three-Dimensional Hull Cell, F. A. Jagush, Ralph E. White, William E. Ryan

Faculty Publications

Current density distribution is an important consideration
for those involved in designing electrochemical systems
and electroplating systems in particular. Although it
is important, the common practice in industry is to use
trial and error to determine designs that optimize current
density distributions in electroplating. The purpose of this
paper is to illustrate the use of the finite element method
(FEM) to predict three-dimensional current density distributions.

Mathematical Model Of A Lithium/Polypyrrole Cell, Taewhan Yeu, Ralph E. White

Faculty Publications

A mathematical model to simulate the charge/discharge behavior of a lithium/lithium perchlorate-propylene carbonate/polypyrrole(Li/LiClO₄-PC/PPy) secondary battery cell is presented. The model can be used to gain a better understanding of the behavior of this cell and to provide guidance toward the design of new secondary batteries which utilize an electronically conductive polymer such as polypyrrole (PPy) as the cathode. The model includes the capability of handling charge and discharge behavior and is used to study the effect of various design parameters on the performance of the cell.

Three-Dimensional Current Distributions In A Bipolar, Chlor-Alkali Membrane Cell, Ralph E. White, F. Jagush, H. S. Burney

Faculty Publications

The current distributions in a stack of bipolar, membrane
chlor-alkali cells are important design considerations
(1). The degree of nonuniformity of the current distribution
is important to know because highly nonuniform
current distributions could cause, among other things, severe
damage to the membrane in a cell stack (2).

Electrochemical Production Of Hydrogen And Sulfur By Low-Temperature Decomposition Of Hydrogen Sulfide In An Aqueous Alkaline Solution, A. A. Anani, Z. Mao, Ralph E. White, S. Srinivasan, A. J. Appleby

Faculty Publications

Electrolysis of hydrogen sulfide to its constituents in a solution containing equimolar concentrations of NaOH and NaHS has been carried out at 80°C. In a double-compartment cell employing Nafion membrane as a separator, both crystalline elemental sulfur and high-purity hydrogen have been produced at high current efficiencies. Only minimal, if any, passivation of the anode by sulfur product was observed. According to solution composition, electrolysis could result in gas evolution at the anode, passivation of the anode by sulfur deposition, or oxidation of sulfide (S^2–) or polysulfide (S) to sulfur oxyanions. However, in an optimized solution, electrolysis gave …

The Effects Of Separator Design On The Discharge Performance Of A Starved Lead-Acid Cell, T. V. Nguyen, Ralph E. White, Hiram Gu

Faculty Publications

A mathematical model of a starved lead-acid cell has been developed to study the dynamic behavior of the cell during discharge. Concentrated binary electrolyte theory and a volume-averaging technique were used to model the transport of electrolyte. The model can be used to predict cell voltage and profile of: acid concentration, overpotential, porosity, reaction rate, and electrode capacity, as functions of time. The effects of separator thickness and its porosity were examined with respect to cold-cranking amperage and reserve capacity of the battery. The separator was found to be a significant factor governing performance.

Conformational Changes In An Epitope Localized To The Nh2-Terminal Region Of Protein C, Carolyn L. Orthener, Rapti D. Madurawe, William H. Velander, William N. Drohan, Frances D. Bettey, Dudley K. Strickhand

Papers in Biotechnology

Murine monoclonal antibodies, developed following immunization with human protein C, were characterized for their ability tboin d antigen in thpe resence of either CaClz or excess EDTA. Three stablec lones were obtained which produced antiboditehsa t bound to protein C only itnh e presence of EDTA. Allt hree antibodies bound to the light choafi np rotein C on immunoblots and also bound to the homologous proteins factor X and prothrombin in solid-phase radioimmunoassays. One antibody, 7D7B10 was purified and studied further. The binding of 7D7B10 to human protein C was characterized bya KOo f 1.4 nM. In competition studies, it …

Process Modelling Of The Nitration Of Toluene, Nitin K. Shah

Theses

The thesis on the process modelling of the nitration process focuses specifically on the product separation of the nitrated aromatic material from the reactor and - wash section of the process. Included in the text is an overview of the main process steps associated with the production of para and ortho-nitrotoluene. The critical issues concerning the reaction of nitric acid and toluene were summerized, and resulted in this subject being deferred for future work.

The separation of the isomers into pure components is an important. part of the MNT process because of the close high boiling points of the isomeric …

Thermal Decomposition Of Chlorobenzene Reaction With Hydrogen And Oxygen Mixture In An Atmosphere, Chun-Chen Yang

Theses

The thermal reactions of chlorobenzene in hydrogen and oxygen mixtures were studied in tubular flow reactors at 1 atmosphere total pressure. Experiments were carried out in flow reactors of varied diameter for determining effects of different surface to volume ratios. Residence times ranged from 0.03 to 2.5 seconds and temperature was varied over a range of 560 - 660 °C. The 02/H2 ratios ranged from 1% to 5%.

It was found that the conversion of chlorobenzene in hydrogen and oxygen mixtures increased with both temperature and residence time. The oxidation of chlorobenzene also occurred more rapidly when oxygen concentraction was …

Agitation Requirements For Complete Drawdown Of Floating Solids In Stirred Tanks, Joseph Philemon Mmbaga

Theses

The agitation requirements for complete drawdown of floating solids in mechanically agitated tank vessels has been studied both theoretically and experimentally.

A semi-theoretical equation has been derived on the basis of Kolmogoroff's theory of isotropic turbulence to determine the minimum impeller speed required for drawdown. The equation contains one adjustable parameter which has been found to be a function of the impeller type and position in the tank vessel.

The equation was tested using various vessels and impeller configurations. The solid phase consisted of high density polyethylene (density = 897kg/m³), low density polyethylene (density = 840kg/m³) …

Molecular Dynamics Simulation Of Real-Fluid Mutual Diffusion Coefficients With The Lennard-Jones Potential Model, Richard L. Rowley, J. M. Stoker

Faculty Publications

Mutual diffusion coefficients for selected alkanes in carbon tetrachloride were calculated using molecular dynamics and Lennard-Jones (LJ) potentials. Use of effective spherical LJ parameters is desirable when possible for two reasons: (i) computer time is saved due to the simplicity of the model and (ii) the number of parameters in the model is kept to a minimum. Results of this study indicate that mutual diffusivity is particularly sensitive to the molecular size cross parameter, σ12, and that the commonly used Lorentz–Berthelot rules are inadequate for mixtures in which the component structures differ significantly. Good agreement between simulated and experimental mutual …

Protein Separation With Mathematical Modeling For Chromatographic Operation, Hsien-Chih Ma

Dissertations

We have performed experiments and derived mathematical models for packed bed columns used for liquid phase chromatographic separations of proteins with impulse input of feed solutions. These models can now be used to describe the relationships between the elution characteristics (peak height, peak position, and shapes) and the operating conditions (flow rate and buffer conditions) of ion exchange and gel permeation column chromatography for protein separations.

The surface adsorption model was discussed relative to the nature of the mobile and stationary phases in ion exchange column chromatography for two distinct cases: with and without pore diffusion. For large solute molecules, …

Quantification Of Refining Actions, Hari R. Goyal

Masters Theses

The repeated action of compression-decompression pulses on a wet web of fiber, created by dropping a weight from a height, loosens the internal structure of the fiber. The impaction of fiber did not cause any change in average weighted fiber length, fine content or Canadian Standard Freeness. The sheet made from these fibers showed an increase in tensile strength with increased number of impacts or impact intensity.

In a blend of impacted fibers (internally fibrillated), abraded fibers (externally fibrillated) and fines (fibers shorter than 0.23 mm and created by prolonged beating in a Valley beater), fines were found to be …

Evaluation Of Equilibrium Turbulence For A Hypersonic Boundary Layer At Nonadiabatic Wall Conditions, Cindy W. Albertson

Mechanical & Aerospace Engineering Theses & Dissertations

This paper presents an experimental study to characterize the compressible turbulent boundary layer produced along a flat plate in the NASA Langley 8-Foot High Temperature Tunnel and determine the test conditions necessary to achieve equilibrium turbulence. In addition, the present study extends the data base for equilibrium compressible turbulent boundary layers over quasi-isothermal walls which are far from the adiabatic wall temperature. The measurements consist of pilot pressure, static pressure, and total temperature distributions in the boundary layer. A flat plate measuring 9.7 feet long and 4.3, feet wide was used for the study to provide a naturally turbulent boundary …

Simulation Of Fluid Flow In Packed Beds Using A Simplified Model And Network Analysis Technique, Haggai W.K. Sarakikya

Tanzania Journal of Engineering and Technology (TJET)

Abstract

Metabolic Activity Of Microorganisms Cultured On Inhibitory In Unsteady State, Cleophas L.C. Migiro

Tanzania Journal of Engineering and Technology (TJET)

Abstract

Flowsheet Simulation Studies Of New Oilseed Extraction Processes, M. Khalfani

Tanzania Journal of Engineering and Technology (TJET)

Results are reported on the flowsheet simulation studies of new oilseed processes suitable for local conditions. A process model was developed and new design simulation methods using Computer Aided Design (CAD) approach were employed for the preliminary investigation of a number of alternative scenarios.

Results have shown that new processes should give considerable investment savings if separation of the crude product is not carried out by distillation. However, the economics of processes using alternative separation technology is highly dependent on operating conditions.

The use of spreadsheet programs for flowsheet evaluation studies offers opportunities for application of CAD techniques in local …