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Articles 871 - 900 of 914

Full-Text Articles in Chemical Engineering

Electrodeposition Of Copper-Nickel Alloys From Citrate Solutions On A Rotating Disk Electrode, Ramona Y. Ying, Patrick K. Ng, Z. Mao, Ralph E. White Jan 1988

Electrodeposition Of Copper-Nickel Alloys From Citrate Solutions On A Rotating Disk Electrode, Ramona Y. Ying, Patrick K. Ng, Z. Mao, Ralph E. White

Faculty Publications

A mathematical model is developed to simulate the electrodeposition of Cu-Ni alloy from citrate solutions onto a rotating disk electrode under potentiostatic control. The model includes the influence of diffusion, ionic migration, forced convection, and homogeneous equilibria. The three major electrochemical reactions treated in the model are copper deposition, nickel deposition, and hydrogen evolution. Using experimental parameters when available, the model was fitted and tested against experimentally-obtained results for different bath compositions and operating conditions. The model agreed reasonably well with the experimental results particularly in the codeposition region, –1.0 to –1.2V vs. SCE, where hydrogen evolution is not the …

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Heats Of Transport From Diffusion Thermoeffect Measurements On Binary Liquid Mixtures Of Carbon Tetrachloride With Benzene, Toluene, 2-Propanone, N-Hexane, And N-Octane, Richard L. Rowley, S. C. Yi Dec 1987

Heats Of Transport From Diffusion Thermoeffect Measurements On Binary Liquid Mixtures Of Carbon Tetrachloride With Benzene, Toluene, 2-Propanone, N-Hexane, And N-Octane, Richard L. Rowley, S. C. Yi

Faculty Publications

Measurements of heats of transport are reported for binary liquid mixtures containing carbon tetrachloride and benzene, toluene, 2-propanone, n-hexane, or n-octane at 298 K and ambient pressure. Additionally, measurements were made at 308 K for carbon tetrachloride with benzene, toluene, and 2-propanone. The corresponding heat-mass Onsager coefficients are also reported, from which thermal diffusion ratios have been calculated based on Onsager reciprocity. These data will be used in a companion paper to report a modified Enskog method for correlation and prediction of heats of transport.

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On The Use Of A Modified Square-Well Model For Prediction And Correlation Of Thermal Diffusion Factors In Binary Liquid Mixtures, Richard L. Rowley, S. C. Yi Dec 1987

On The Use Of A Modified Square-Well Model For Prediction And Correlation Of Thermal Diffusion Factors In Binary Liquid Mixtures, Richard L. Rowley, S. C. Yi

Faculty Publications

Recently reported thermal diffusion factors obtained from heats of transport have been used to test the ability of existing theories to predict thermal diffusivities using model parameters regressed from pure component transport data. None of the theories tested were able to provide even qualitative agreement with experiment. However, predictions using a square-well Enskog theory, modified here for consistency with normal experimental definitions, were found to be approximately correct using pure-component square-well parameters regressed from viscosity and thermal conductivity and an assumed mixing rule for cross terms. Predicted values are very sensitive to the energy mixing rule, and correlation of experimental …

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Hard-Sphere Theory For Correlation Of Tracer Diffusion Of Gases And Liquids In Alkanes, Michael A. Matthews, Aydin Akgerman May 1987

Hard-Sphere Theory For Correlation Of Tracer Diffusion Of Gases And Liquids In Alkanes, Michael A. Matthews, Aydin Akgerman

Faculty Publications

No abstract provided.

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A Mathematical Model For The Initial Corrosion Rate Of A Porous Layer On A Rotating Disk Electrode, William E. Ryan, Ralph E. White, S. L. Kelly Jan 1987

A Mathematical Model For The Initial Corrosion Rate Of A Porous Layer On A Rotating Disk Electrode, William E. Ryan, Ralph E. White, S. L. Kelly

Faculty Publications

A mathematical model is presented for the initial corrosion rate of a porous layer on a rotating disk electrode. The model is used to predict the corrosion potential and corrosion current density for a porous electrode made of pure iron in aerated caustic solutions. The dependence of these predictions on some of the properties of the porous layer is presented. It is shown that the corrosion rate depends significantly on the specific surface area of the porous electrode.

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The Effect Of The Tribromide Complex Reaction On The Oxidation/Reduction Current Of The Br2/Br– Electrode, P K. Adanuvor, Ralph E. White, S. E. Lorimer Jan 1987

The Effect Of The Tribromide Complex Reaction On The Oxidation/Reduction Current Of The Br2/Br– Electrode, P K. Adanuvor, Ralph E. White, S. E. Lorimer

Faculty Publications

The Br2/Br– electrode reaction with tribromide complex formation reaction in the solution, a chemical-electrochemical (C-E) type reaction, has been investigated in order to determine the effect of the chemical reaction on the electrode kinetics. It is shown that the chemical reaction has little effect on the electrode kinetics at very slow homogeneous reaction rates, but has a more drastic effect on the electrode kinetics at faster homogeneous reaction rates. Also, the kinetics at the electrode are affected by changes in the concentrations of the active species (Br2, Br–, and Br3–) …

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Modeling The Rotating Disk Electrode For Studying The Kinetics Of Electrochemical Reactions, P K. Adanuvor, Ralph E. White, S E. Lorimer Jan 1987

Modeling The Rotating Disk Electrode For Studying The Kinetics Of Electrochemical Reactions, P K. Adanuvor, Ralph E. White, S E. Lorimer

Faculty Publications

A general mathematical model for studying the kinetics of electrochemical reactions at a rotating disk electrode under steady-state potentiostatic conditions is presented. The model, apart from predicting the net and partial current densities at given values of the applied potential, the ohmic potential drop, and the concentration and potential profiles in the solution, also accounts for homogeneous reactions of any order in the solution and noncharge transfer reactions at the electrode surface. The versatility of the model is demonstrated by the application of the model to a variety of complex reaction schemes.

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A Mathematical Model Of A Zinc/Bromine Flow Cell, T. I. Evans, Ralph E. White Jan 1987

A Mathematical Model Of A Zinc/Bromine Flow Cell, T. I. Evans, Ralph E. White

Faculty Publications

A mathematical model is presented for a zinc/bromine flow cell. The model includes a thin porous layer on the bromine electrode and a porous separator. The independent parameters of the porous layer are defined, and their effect on cell performance during charge and discharge is investigated. The dependence of the round trip energy efficiency on the thickness of the porous layer and mode of discharge is presented. The predictions of the model show that a maximum round trip energy efficiency of 70% should be possible under the design conditions considered.

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Simulation Of The Polarization Curves For Oxygen Reduction At A Rotating Disk Electrode, P. K. Adanuvor, Ralph E. White Jan 1987

Simulation Of The Polarization Curves For Oxygen Reduction At A Rotating Disk Electrode, P. K. Adanuvor, Ralph E. White

Faculty Publications

The electrochemical reduction of oxygen in 1M NaOH solution is simulated at a rotating disk electrode. Steady-state polarization curves are presented for possible reaction schemes for the reduction process. The effect of changes in the kinetic parameters on the polarization curves is demonstrated and special attention is focused on the production of hydrogen peroxide.

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Utility Of An Empirical Method Of Modeling Combined Zero Gap/Attached Electrode Membrane Chlor-Alkali Cells, Clifford W. Walton, Ralph E. White Jan 1987

Utility Of An Empirical Method Of Modeling Combined Zero Gap/Attached Electrode Membrane Chlor-Alkali Cells, Clifford W. Walton, Ralph E. White

Faculty Publications

An extensive survey of the Docktor-Ingenieur Dissertationen of Jakob Jörissen and Klaus-R. Menschig, both originally from the Universität Dortmund, is presented in regard to the empirical modeling of membrane chlor-alkali cells and how it can be applied to a combined zero gap/attached porous electrode layer membrane cell. Particular emphasis isplaced on Menschig's work on zero gap (ZG) and attached porous electrode layer (APEL) membrane chlor-alkali cells, the first such research to appear in the open literature. Menschig developed various computer programs to characterize these ZG and APEL membrane chlor-alkali cells. He characterized these cells by using the following parameters: the …

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A Review Of Mathematical Modeling Of The Zinc/Bromine Flow Cell And Battery, T. I. Evans, Ralph E. White Jan 1987

A Review Of Mathematical Modeling Of The Zinc/Bromine Flow Cell And Battery, T. I. Evans, Ralph E. White

Faculty Publications

Mathematical models which have been developed to study various aspects of the zinc/bromine cell and stack of cells are reviewed. Development of these macroscopic models begins with a material balance, a transport equation which includes a migration term for charged species in an electric field, and an electrode kinetic expression. Various types of models are discussed: partial differential equation models that can be used to predict current and potential distributions, an algebraic model that includes shunt currents and associated energy losses and can be used to determine the optimum resistivity of an electrolyte, and ordinary differential equation models that can …

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A Mathematical Model Of A Lead-Acid Cell: Discharge, Rest, And Charge, Hiram Gu, T. V. Nguyen, Ralph E. White Jan 1987

A Mathematical Model Of A Lead-Acid Cell: Discharge, Rest, And Charge, Hiram Gu, T. V. Nguyen, Ralph E. White

Faculty Publications

A mathematical model of a lead-acid cell is presented which includes the modeling of porous electrodes and various physical phenomena in detail. The model is used to study the dynamic behavior of the acid concentration, the porosity of the electrodes, and the state of charge of the cell during discharge, rest, and charge. The dependence of the performance of the cell on electrode thicknesses and operating temperature is also investigated.

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Heats Of Transport From The Diffusion Thermoeffect In Binary Liquid Mixtures Of Toluene, Chlorobenzene, And Bromobenzene, Richard L. Rowley, M. D. Hall Sep 1986

Heats Of Transport From The Diffusion Thermoeffect In Binary Liquid Mixtures Of Toluene, Chlorobenzene, And Bromobenzene, Richard L. Rowley, M. D. Hall

Faculty Publications

Measurements of heats of transport in binary liquid mixtures of toluene, chlorobenzene, and bromobenzene utilizing the diffusion thermoeffect, or Dufour effect, are reported at 298 and 308 K. The corresponding heat-mass Onsager doefficients are also reported, from which thermal diffusion ratios have been calculated based on Onsager reciprocity. The resultant binary thermal diffusion ratios have been correlated as a function of composition in an attempt to study the relationship between values in binary and ternary mixtures. It was found that the single independent binary values can be used to estimate the two independent thermal diffusion ratios previously reported in toluene …

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Predicting Shunt Currents In Stacks Of Bipolar Plate Cells, Ralph E. White, C. W. Walton, H. S. Burney, R. N. Beaver Jan 1986

Predicting Shunt Currents In Stacks Of Bipolar Plate Cells, Ralph E. White, C. W. Walton, H. S. Burney, R. N. Beaver

Faculty Publications

A method is presented for predicting shunt currents in stacks of undivided and divided bipolar plate cells. The method is an efficient way of solving the coupled sets of algebraic equations that arise from using circuit analog models to represent the current paths in stacks of undivided or divided bipolar plate cells. These algebraic equations can be eitherlinear or nonlinear depending upon the current-potential relationships used in the model (i.e., nonlinear circuit elements can be included). The method is used to show the importance of including nonsymmetrical resistances and nonlinear circuit elements in the models. Also, the method …

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A Mathematical Model Of A Zn/Br2 Cell On Charge, M J. Mader, Ralph E. White Jan 1986

A Mathematical Model Of A Zn/Br2 Cell On Charge, M J. Mader, Ralph E. White

Faculty Publications

A mathematical model of a parallel plate electrochemical cell with a separator and a homogeneous bulk reaction is presented. The model is based on the Zn/Br2 redox couple and can be used as an aid for the design of an efficient rechargeable storage battery. It is shown that four independent variables exist for the system at a fixed temperature: the effective separator thickness, the residence time, the channel width, and the potential driving force. Performance criteria of interest for the Zn/Br2 battery are defined. Predictions of performance during the charging process are presented. It is shown that the …

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Parallel-Plate Electrochemical Reactor Model: A Method For Determining The Time-Dependent Behavior And The Effects Of Axial Diffusion And Axial Migration, T. V. Nguyen, C. W. Walton, Ralph E. White, J. Van Zee Jan 1986

Parallel-Plate Electrochemical Reactor Model: A Method For Determining The Time-Dependent Behavior And The Effects Of Axial Diffusion And Axial Migration, T. V. Nguyen, C. W. Walton, Ralph E. White, J. Van Zee

Faculty Publications

A method is presented for determining the effects of time dependence, axial diffusion, and axial migration in aparallel-plate electrochemical reactor (PPER). The method consists of formulating the governing equations and applying a numerical integration technique to solve a set of time-dependent, nonlinear, coupled, multidimensional equations. This formulation reveals that the steady-state performance of the PPER depends on the cell potential and three dimensionless groups. Predictions of the concentration, potential, and local current distributions in a PPER are presented for the electrowinning of copper from an aqueous, hydrochloric acid solution. These predictions show that axial diffusion and axial migration are significant …

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Simple Models For Diaphragm-Type Chlorine/Caustic Cells Ii. Effect Of Acidic Anolyte On Steady-State Caustic Yield, John Van Zee, Ralph E. White Jan 1986

Simple Models For Diaphragm-Type Chlorine/Caustic Cells Ii. Effect Of Acidic Anolyte On Steady-State Caustic Yield, John Van Zee, Ralph E. White

Faculty Publications

A simple steady-state model of a diaphragm-type chlorine/caustic cell in which the diaphragm is divided into two regions by a homogeneous acid-base reaction is presented. The location of the reaction affects significantly the caustic yield and effluent concentration. The model is used to predict the location of this reaction as a function of the operating variables, the physical constants, and three measurable properties of the diaphragm. These measurable properties are the MacMullin number or resistivity ratio of electrolyte-filled diaphragm relative to the electrolyte, the Darcy's law diaphragmpermeability, and the diaphragm thickness. The model is used to predict a maximum in …

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Simple Models For Diaphragm-Type Chlorine/Caustic Cells I. Dynamic Behavior, John Van Zee, Ralph E. White, A T. Watson Jan 1986

Simple Models For Diaphragm-Type Chlorine/Caustic Cells I. Dynamic Behavior, John Van Zee, Ralph E. White, A T. Watson

Faculty Publications

A simple model of the dynamic behavior of a diaphragm-type chlorine/caustic cell is presented. The model is based upon measurable diaphragm properties and the mass transfer of hydroxyl ion through the diaphragm. The anolyte is modeled simply as a region in which the OH– ion concentration is fixed, the diaphragm is modeled as a plug-flow reactor with an electrochemical reaction occurring at the catholyte/diaphragm interface where the cathode is placed, and the catholyte is modeled as a completely stirred flow reactor. Analytical integration of the governing equations for thesemodels yields two mathematical expressions: one for the concentration distribution of …

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Parallel Plate Electrochemical Reactor Model: Material Balance Closure And A Simplification, M J. Mader, C W. Walton, Ralph E. White Jan 1986

Parallel Plate Electrochemical Reactor Model: Material Balance Closure And A Simplification, M J. Mader, C W. Walton, Ralph E. White

Faculty Publications

A material balance closure calculation is presented to test the consistency of a previously published model of a parallelplate electrochemical reactor. New expressions are used in this procedure to calculate the average concentration of species i and the average current density for reaction j from the predicted concentration and potential distributions. Also, the previously presented model equations are simplified by assuming that the axial concentration gradient for species i can be approximated by a step change from the known feed concentration to the unknown outlet concentration. This one-step model provides a qualitative evaluation of cell performance and adds insight into …

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A Mathematical Model For A Parallel Plate Electrochemical Reactor, Cstr, And Associated Recirculation System, T V. Nguyen, C W. Walton, Ralph E. White Jan 1986

A Mathematical Model For A Parallel Plate Electrochemical Reactor, Cstr, And Associated Recirculation System, T V. Nguyen, C W. Walton, Ralph E. White

Faculty Publications

A mathematical model is presented for a system comprised of a parallel plate electrochemical reactor (PPER) and a continuous, stirred-tank reactor (CSTR) under both total and partial recycle. The model is used to predict the time dependent behavior of the electrowinning of copper from an aqueous, hydrochloric acid solution. The model includes many important aspects of a PPER/CSTR system which have been neglected previously. These aspects are the kinetics of electrode reactions, the electroneutrality condition, three mass transfer processes for ionic species in the electrolyte (diffusion, ionic migration, and convection) and the electrode gap in the PPER, and the inclusion …

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Industrial Earthquake Preparedness In Shizuoka And The Role Of The Prefectural Government, Guna S. Selvaduray Feb 1985

Industrial Earthquake Preparedness In Shizuoka And The Role Of The Prefectural Government, Guna S. Selvaduray

Faculty Publications

The Shizuoka Prefectural Office in Japan plays an important role in promoting earthquake emergency preparedness among its industries. In addition to implementing regulatory requirements and enacting new regulations as necessary, the Prefectural Office also provides significant guidance to industry. This includes making publications available and periodic surveys of the status of industrial emergency preparedness. A pharmaceutical company in the prefecture has developed an impressive earthquake preparedness program and hazard reduction techniques. This program addresses both primary and secondary effects of earthquakes.

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Using Parameter Estimation Techniques With A Simple Model Of A Diaphragm-Type Electrolyzer To Predict The Electrical Energy Cost For Naoh Production, John Van Zee, Ralph E. White Jan 1985

Using Parameter Estimation Techniques With A Simple Model Of A Diaphragm-Type Electrolyzer To Predict The Electrical Energy Cost For Naoh Production, John Van Zee, Ralph E. White

Faculty Publications

Predictions of the electrical energy cost for NaOH production are determined as a function of the independent operating variables and diaphragm characterizing properties. The predictions are based on data from a statistically designed experiment, a simple model of a diaphragm-type electrolyzer, a simple model of the cell voltage losses, and parameter estimation techniques. The data were obtained over a sufficiently large range of operating conditions so that the resulting design equation may be industrially useful. The simple model of the diaphragm is based on the mass transport of the hydroxyl ion, a linear potential gradient, and is presented in terms …

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Extension Of Darby's Model Of A Hydrophylic Gas Fed Porous Electrode, Ralph E. White, M. A. Nicholson, L. G. Kleine, J. Van Zee, R. Darby Jan 1984

Extension Of Darby's Model Of A Hydrophylic Gas Fed Porous Electrode, Ralph E. White, M. A. Nicholson, L. G. Kleine, J. Van Zee, R. Darby

Faculty Publications

A model presented previously by one of the authors (1,2) is reviewed and extended. Aspects of this model which were not previously available in the open literature are considered, and the model is extended to include previously neglected terms in the governing differential equations, fractional reaction orders in the current density-overpotential expression, and mass-transfer coefficients to account for mass-transfer resistance of the reactants to the faces of the porous electrode. The model is used to predict quantities of interest for oxygen reduction in an acidic aqueous solution in a porous carbon electrode.

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A Model Of The Bromine/Bromide Electrode Reaction At A Rotating Disk Electrode, Ralph E. White, S. E. Lorimer Jan 1983

A Model Of The Bromine/Bromide Electrode Reaction At A Rotating Disk Electrode, Ralph E. White, S. E. Lorimer

Faculty Publications

A mathematical model is presented for the Br2/Br– electrode reaction at a rotating disk electrode. The model includes current density-overpotential expressions for the electrode reaction according to either the Volmer-Heyrovsky (V-H) or the Volmer-Tafel (V-T) mechanism and the transport equations including the effect of ionic migration. The model is used to predict current-overpotential curves for various cases of interest. Qualitative comparison of the model predictions to literature data shows that either the V-H or the V-T mechanism, with V controlling, may be acceptable for the Br2/Br– reaction.

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An Analysis Of A Back Fed Porous Electorde For The Br2/Br- Redox Reaction, John W. Van Zee, Ralph E. White Jan 1983

An Analysis Of A Back Fed Porous Electorde For The Br2/Br- Redox Reaction, John W. Van Zee, Ralph E. White

Faculty Publications

No abstract provided.

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Parallel Plate Electrochemical Reactor Model, Ralph E. White, Mike Bain, Mike Raible Jan 1983

Parallel Plate Electrochemical Reactor Model, Ralph E. White, Mike Bain, Mike Raible

Faculty Publications

No abstract provided.

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Prediction Of The Current Density At An Electrode At Which Multiple Electrode Reactions Occur Under Potentiostatic Control, Ralph E. White, S. E. Lorimer, R. Darby Jan 1983

Prediction Of The Current Density At An Electrode At Which Multiple Electrode Reactions Occur Under Potentiostatic Control, Ralph E. White, S. E. Lorimer, R. Darby

Faculty Publications

It is often desirable to be able to predict the total current density at an electrode when multiple electrochemical reactions occur there under potentiostatic control. It is also sometimes desirable to include the effect of ionic migration within the diffusion layer upon the predicted total (1) and partial current densities (2). A procedure for doing this can be illustrated by considering the rotating disk electrode (RDE) system and the associated potential distribution near the RDE as shown in Fig. 1 and 2.

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An Analysis Of A Back Fed Porous Electrode For The Br2/Br Reaction, John Van Zee, Ralph E. White Jan 1983

An Analysis Of A Back Fed Porous Electrode For The Br2/Br Reaction, John Van Zee, Ralph E. White

Faculty Publications

An experimental analysis of the Br2/Br– redox reaction in a porous back fed ruthenium-coated titanium electrode is described. A mathematical model of the steady-state process is presented. Nonlinear regression of the model against the experimental data gives physically meaningful parameter estimates; these parameters and the model provide a design equation for the porous electrode current as a function of specific surface area, bulk Br2 concentration, average total overpotential, and the Reynolds number. The design equation shows that the back fed electrode could reduce the loss of Br2 across the separator and the ohmic loss in …

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Diffusion Thermoeffect Measurements Of Heats Of Transport In Ternary Liquid Toluene Chlorobenzene Bromobenzene Mixtures At 25°C And 3°C, Richard L. Rowley, Gerald Platt, Tevin Vongvanich Aug 1982

Diffusion Thermoeffect Measurements Of Heats Of Transport In Ternary Liquid Toluene Chlorobenzene Bromobenzene Mixtures At 25°C And 3°C, Richard L. Rowley, Gerald Platt, Tevin Vongvanich

Faculty Publications

Heats of transport in ternary nonelectrolyte liquid mixtures have been directly measured for the first time. Diffusion thermoeffect measurements have been made for ternary mixtures of toluene-chlorobenzene-bromobenzene at 25 degrees and 35 degrees C. A new boundary sharpening technique was used in addition to a liquid gate withdrawal method. Both techniques yield consistent, accurate values of the heat of transport, but the new cell provides versatility in allowable densities and compositions of the initial phases. Heats of transport were obtained by nonlinear least-squares fitting of calculated to experimental temperature differences measured at positions symmetric about the initial diffusional interface. The …

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The Diffusion Thermoeffect In Ternary, Nonelectrolyte Liquid Mixtures, Richard L. Rowley, Gerald Platt, Tevin Vongvanich Aug 1982

The Diffusion Thermoeffect In Ternary, Nonelectrolyte Liquid Mixtures, Richard L. Rowley, Gerald Platt, Tevin Vongvanich

Faculty Publications

Expressions for that portion of the heat flux which is due to composition gradients in multicomponent nonelectrolyte liquid mixtures have been formulated in terms of heats of transport. The resultant thermal energy equation in combination with component mass balance equations constitute coupled partial differential equations descriptive of the diffusion thermoeffect in liquid mixtures. These equations were solved with a double perturbation technique subject to initial and boundary conditions consistent with experimental design conditions considered appropriate for successful measurement of multicomponent heats of transport. Based on the adiabatic type cell, the expected temperature response, dependent on cell variables, experimental conditions, and …

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