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Full-Text Articles in Engineering
A Mathematical Model Of A Sealed Nickel-Cadmium Battery, Deyuan Fan, Ralph E. White
A Mathematical Model Of A Sealed Nickel-Cadmium Battery, Deyuan Fan, Ralph E. White
Faculty Publications
A mathematical model for the charge and discharge of a sealed nickel-cadmium (Ni-Cd) battery is presented. The model is used to study the effect of transport properties of the electrolyte and kinetic parameters of the electrode reactions on the cell performance during the charge and discharge period. The model can also be used to demonstrate the changes of cell performance during cycling. Some comparisons between model predictions and experimental results indicate that the model predictions appear to fit the experimental data well. Sensitivity analyses illustrate that the sealed nickel-cadmium battery operates under activation control. It is also shown theoretically that …
Electrode Kinetics Of Oxygen Reduction In Lithium Carbonate Melt: Use Of Impedance Analysis And Cyclic Voltammetric Techniques To Determine The Effects Of Partial Pressure Of Oxygen, Bhasker B. Davé, Ralph E. White, Supramanian Srinivasan, A. John Appleby
Electrode Kinetics Of Oxygen Reduction In Lithium Carbonate Melt: Use Of Impedance Analysis And Cyclic Voltammetric Techniques To Determine The Effects Of Partial Pressure Of Oxygen, Bhasker B. Davé, Ralph E. White, Supramanian Srinivasan, A. John Appleby
Faculty Publications
The effects of the partial pressure of oxygen and temperature on the oxygen reduction on a submerged gold electrode in a lithium carbonate melt were investigated using cyclic voltammetry and impedance analysis. The values for the mass-transfer parameters, DCO, obtained from cyclic voltammetry and impedance analysis were in good agreement. The reaction orders for oxygen at 800°C were calculated to be about 0.3 for the exchange current density and 0.5 for the product DCO; these values are consistent with the mechanism proposed in the literature for oxygen reduction in Li2CO3 melt.
A Mathematical Model Of Electrochemical Reactions Coupled With Homogeneous Chemical Reactions, Ken-Ming Yen, Taewhan Yeu, Ralph E. White
A Mathematical Model Of Electrochemical Reactions Coupled With Homogeneous Chemical Reactions, Ken-Ming Yen, Taewhan Yeu, Ralph E. White
Faculty Publications
The zinc/bromine (Zn/Br2) flow battery has received considerable
attention in recent years [e.g., (2-4)]. Although it
is agreed that the solution chemistry is important in the
system, most of the work that has been done is concentrated
on the design variables. In this note the basic mass
transfer-solution and surface kinetics are studied to furnish
a better understanding of the system.
A Modified Electrochemical Process For The Decomposition Of Hydrogen Sulfide In An Aqueous Alkaline Solution, Z. Mao, A. Anani, Ralph E. White, S. Srinivasan, A. J. Appleby
A Modified Electrochemical Process For The Decomposition Of Hydrogen Sulfide In An Aqueous Alkaline Solution, Z. Mao, A. Anani, Ralph E. White, S. Srinivasan, A. J. Appleby
Faculty Publications
An electrochemical process for the decomposition of hydrogen sulfide into its constituents in an aqueous alkaline solution is presented. It essentially consists of presaturation of an alkaline scrubber solution with H2S. Thereafter, partial neutralization of the presaturated solution provides not only the necessary mass balance for electrolysis, but also creates the optimum conditions under which passivation of the anode, as well as side chemical and electrochemical reactions, are minimized. Finally, the electrolysis stage of the process leads to precipitation of crystalline sulfur at the anode and evolution of hydrogen at the cathode. Regeneration of the alkaline solution via …
Current Distribution In A Horizon® Lead-Acid Battery During Discharge, Z. Mao, Ralph E. White, B. Jay
Current Distribution In A Horizon® Lead-Acid Battery During Discharge, Z. Mao, Ralph E. White, B. Jay
Faculty Publications
A simple mathematical model is presented and used to analyze the potential and current distributions in a HORIZON® sealed lead-acid battery. It was found that an increase in the thickness of an electrode would not enhance the discharge rate of that electrode; instead, it causes the transfer current distribution to be less uniform in the electrode. Also, the ohmic drop across the separator would decrease with a decrease in the thickness of the separator more rapidly when the thickness is small than when it is large. In addition, it was found that efficient high-capacity, high-rate electrodes must consider the electrode …
Modification Of Newman's Band(J) Subroutine To Multi-Region Systems Containing Interior Boundaries: Mband, D. Fan, Ralph E. White
Modification Of Newman's Band(J) Subroutine To Multi-Region Systems Containing Interior Boundaries: Mband, D. Fan, Ralph E. White
Faculty Publications
Newman's BAND(J) subroutine, which has been used widely to solve models of various electrochemical systems, is extended to solve a system of coupled, ordinary differential equations with interior boundary conditions. A set of coupled, linear ordinary differential equations is used to demonstrate the solution procedure. The results show that the extended technique has the same accuracy as that of using pentadiagonal BAND(J), but the execution speed is about five times faster than that of pentadiagonal BAND(J). Using sparse matrix solver Y12MAF to solve the same set of equations takes even longer time than pentadiagonal BAND(J).
Impedance Analysis For Oxygen Reduction In A Lithium Carbonate Melt, Bhasker B. Davé, Ralph E. White, Supramaniam Srinivasan, A. John Appleby
Impedance Analysis For Oxygen Reduction In A Lithium Carbonate Melt, Bhasker B. Davé, Ralph E. White, Supramaniam Srinivasan, A. John Appleby
Faculty Publications
Oxygen reduction on a smooth gold electrode in a pure lithium carbonate melt was investigated by electrochemical impedance spectroscopy and cyclic voltammetry. The impedance data were analyzed using the Randles-Ershler equivalent circuit to determine parameters such as the charge-transfer resistance, Warburg coefficient, double-layer capacity, and uncompensated electrolyte resistance. The parameters estimated by complex plane plots and a complex nonlinear least squares method are in good agreement. Cyclic voltammetric measurements showed that oxygen reduction in a lithium carbonate melt is very rapid. A mass transfer parameter, DC0, estimated by the cyclic voltammetry concurred withthat calculated by the electrochemical …
Electrochemical Characterization Of Electronically Conductive Polypyrrole On Cyclic Voltammograms, Taewhan Yeu, Ken-Ming Yin, Jose Carbajal, Ralph E. White
Electrochemical Characterization Of Electronically Conductive Polypyrrole On Cyclic Voltammograms, Taewhan Yeu, Ken-Ming Yin, Jose Carbajal, Ralph E. White
Faculty Publications
Experimental and theoretical cyclic voltammograms for electronically conducting polypyrrole film are obtained from the identical conditions and compared to each other to characterize electrochemical behavior of the polymer. A comparison of the simulated and experimental cyclic yoltammograms shows quantitative agreement. The profiles of the dependent variables show that the switching process is governed by the availability of the counter ion to the polypyrrole electrode and the amount of electroactive sites. Sensitivity analysis shows that the double layer effects have more influence in the cyclic voltammograms than the electrokinetic effects.
Mathematical Modeling Of A Nickel-Cadmium Battery: Effects Of Intercalation And Oxygen Reactions, Deyuan Fan, Ralph E. White
Mathematical Modeling Of A Nickel-Cadmium Battery: Effects Of Intercalation And Oxygen Reactions, Deyuan Fan, Ralph E. White
Faculty Publications
Extensions are presented for a previously published (1) mathematical model of a nickel-cadmium (Ni-Cd) cell. These extensions consist of intercalation thermodynamics for the nickel electrode and oxygen generation and reduction reactions during charge and overcharge. The simulated results indicate that intercalation may be important in the nickel electrode and that including the oxygen reactions provides a means of predicting the efficiency of the cell on charge and discharge.
A Mathematical Model Of The Self-Discharge Of A Ni-H2 Battery, Z. Mao, Ralph E. White
A Mathematical Model Of The Self-Discharge Of A Ni-H2 Battery, Z. Mao, Ralph E. White
Faculty Publications
A simple mathematical model is presented and used to characterize the self-discharge of a nickel oxyhydroxide(NiOOH) electrode in a hydrogen environment. This model includes diffusion of dissolved hydrogen in an electrolyte film which covers a flooded electrode, electrochemical oxidation of hydrogen, reduction of nickel oxyhydroxide, and changes of surface area and of porosity of the electrode during the self-discharge process. Although the self-discharge process is complicated, the predictions of the model are consistent with experimental results reported in the literature, which include linear relationships between the logarithm of hydrogen pressure and time and between the logarithm of the capacity remaining …
A Mathematical Model Of A Hydrogen/Oxygen Alkaline Fuel Cell, Michael C. Kimble, Ralph E. White
A Mathematical Model Of A Hydrogen/Oxygen Alkaline Fuel Cell, Michael C. Kimble, Ralph E. White
Faculty Publications
A mathematical model of a hydrogen/oxygen alkaline fuel cell is presented that can be used to predict polarization behavior under various potential loads. The model describes the phenomena occurring in the solid, liquid, and gaseous phases of the anode, separator, and cathode regions, assuming a macrohomogeneous, three-phase porous electrode structure. The model calculates the spatial variation of the partial pressures of oxygen, hydrogen, and water vapor, dissolved oxygen and hydrogen concentrations, electrolyte concentration, and the solid- and solution-phase potential drops. By developing a complete model of the alkaline fuel cell, the interaction of the various transport and kinetic resistances can …
In Situ Degradation Of Polyhalogenated Aromatic Hydrocarbons By Electrochemically Generated Superoxide Ions, E. E. Kalu, Ralph E. White
In Situ Degradation Of Polyhalogenated Aromatic Hydrocarbons By Electrochemically Generated Superoxide Ions, E. E. Kalu, Ralph E. White
Faculty Publications
The reduction of dioxygen in aprotic media yields superoxide ions which react with polyhalogenated aromatic hydrocarbons by nucleophilic substitution. The degradation of hexachlorobenzene to bicarbonates and chlorides using in situ generated superoxide ions was carried out at room temperature in a flow cell system equipped with a gas fed, porous electrode. The effects of current, electrolyte flow, and aprotic media on the extent of degradation of hexachlorobenzene are presented.
Effect Of Ohmic, Mass-Transfer, And Kinetic Resistances On Linear-Sweep Voltammetry In A Cylindrical-Pore Electrode, John W. Weidner, Peter S. Fedkiw
Effect Of Ohmic, Mass-Transfer, And Kinetic Resistances On Linear-Sweep Voltammetry In A Cylindrical-Pore Electrode, John W. Weidner, Peter S. Fedkiw
Faculty Publications
Extracting quantitative kinetic information from linear-sweep voltammograms (LSV) on porous electrodes is more difficult than on planar electrodes since the electrode surface is not uniformly accessible to the bulk supply of reactant or the counterelectrode. We present here a means to account for the effect of ohmic, mass-transfer, and kinetic resistances on LSV by modeling a pore in a porous matrix as a cylindrical-pore electrode, and solving the mass and charge conservation equations in the context of this geometry for the simply redox reaction O + ne– <=> R where both O and R are soluble species. Both analytical …