Electrode Current Distribution Research Articles

Generalized Algebraic Phenomenological Model for Parallel-Plate Bipolar Electrochemical Reactors

Electrochemical reactors with bipolar electrodes are widely used in industry and laboratories due to their ease of assembly and electrical connection. Understanding the impact of leakage currents on reactor performance is crucial for design improvement. Previous studies have analyzed these devices using the Laplace equation and Tafel kinetics for a single bipolar electrode. A simplified analysis of a reactor with multiple bipolar electrodes was also conducted, neglecting the contribution of intermediate electrodes to the leakage current. In this article, a simplified model to analyse the influence of leakage current on the electrode current distribution in a reactor with n bipolar electrodes is developed. Multiple models to study the current that flows perpendicular to the electrodes and finally becomes parasitic current, are studied. Also two reaction kinetics, Tafel and Butler-Volmer, are taking into account. Experimental data of reactors with one bipolar electrode considering Tafel-type kinetics, and with one and two bipolar electrodes considering primary current distribution, are compared with predictions obtained through the Laplace equation, and the models of this paper. Furthermore, given the current importance of green hydrogen, this work sheds light on the implications of the study and design of electrochemical reactors used in its production.

Optimization of Low-Voltage Metallized Film Capacitor Geometry

Thermal constraint is one of the major cause of capacitor failures. In this paper, a loss model, based on electrode current distribution, is first established to determine, by numerical simulation, a temperature mapping of capacitor. This mapping is successfully compared to measurements. Then a shape optimization, coupling losses computing and finite-element method, is led in order to find parameters that give the best lifespan and the larger reactive power provided. Very interesting new geometries have been found out; they allow an increase in reactive power greater than the increase in volume

Line stimulation parallel to myofibers enhances regional uniformity of transmembrane voltage changes in rabbit hearts.

The sign of transmembrane voltage (Vm) change (delta Vm) in the heart during unipolar point stimulation is nonuniform, which introduces dispersion of states of Vm-dependent ion channels that depends on fiber orientation. We hypothesized that line stimulation parallel to cardiac fibers increases regional uniformity of the delta Vm sign. To test this, we evaluated electrode current distribution and delta Vm produced by unipolar line stimulation in isolated rabbit hearts. The Vm-sensitive fluorescent dye, di-4-ANEPPS, and a laser scanner provided delta Vm measurements at 63 spots in an 8 x 8-mm epicardial region. Line stimulation was tested at specific angles with respect to the fiber direction. Current peaks occurred at electrode ends. For electrodes parallel to fibers (0 degree), epicardium in regions beyond the ends exhibited a nonuniform delta Vm sign, whereas epicardium between the ends exhibited a uniform delta Vm sign that was essentially negative (hyperpolarized) during anodal pulses and positive (depolarized) during cathodal pulses. The delta Vm sign between the ends became less uniform when the stimulation angle was increased relative to the long axis of the fibers. At 90 degrees, the delta Vm sign between the ends was nonuniform and was frequently opposite, near versus away from the electrode. Spatial distributions of delta Vm during line stimulation were qualitatively predictable from anisotropic effects of point stimulation provided that combined effects of points along the electrode and points with higher current near ends were considered. For biphasic line stimulation, delta Vm during the second phase was weakly correlated with the temporal sum of effects of phases given individually, indicating limited ability of summation to predict delta Vm. Thus, uniformity of the delta Vm sign during stimulation is enhanced in the region between the ends of a line electrode parallel to fibers. This may lessen arrhythmogenic dispersion of Vm-dependent ion channel states in the region.

Electrode current distribution in a hypochlorite cell

Electrochemical production of gases, e.g. Cl2, H2 and O2, is generally carried out in vertical electrolysers with a narrow electrode gap. The evolution of gas bubbles, on one hand, speeds up the mass transport; on the other it increases the solution resistance and also the cell potential. The gas void fraction in the cell increases with increasing height and, consequently, the current density is expected to decrease with increasing height. Insight into the effects of various parameters on the current distribution and the ohmic resistance in the cell is of the utmost importance in understanding the electrochemical processes at gas-evolving electrodes. An example of the described phenomena is the on-site production of hypochlorite by means of a vertical cell. Experiments were carried out with a working electrode consisting of 20 equal segments and an undivided counter electrode. It has been found that the current distribution over the anode is affected by various electrolysis parameters. The current density,j, decreased linearly with increasing distance,h, from the leading edge of the electode. The absolute value of the slope of theI/h straight line increased with increasing average current density and temperature, and with decreasing velocity of the solution, NaCl concentration and interelectrode gap.

Langmuir probes of general shape and electrode current distribution in a flowing plasma

The physical basis of ion collection by a negatively charged Langmuir probe in a quasineutral plasma is elucidated and arguing from the general solution of the stationary collisionless Boltzmann equation the dichotomy of current/voltage relationships below and above saturation voltage is explained. Without restriction of shape it is shown how the 3/4 law of plane probe theory may be extended in an averaging sense. It is argued that the removal of electrons to form a positive sheath adjacent to the probe proceeds isoenergetically along the equipotentials of Laplace's equation so that these remain the equipotentials of the Poisson equation for the positive sheath region which develops although the potential and field will satisfy the latter rather than the former equation. This idea is pursued for the case of 3D probe shapes matching orthogonal coordinate systems and for cylindrically symmetric probe shapes of arbitrary simply-connected cross-section and differential equations for potentials in the space-charge regions are derived. For the case of a probe in a plasma with flow velocity much above thermal maximal current densities on the collector may occur at points distinct from electrostatic field maxima loci. This is handled by treating the current density as a statistical distribution and expressing the standard deviation as a function of voltage. That which is new in this paper may be summarized as follows: (1) The generalization of shapes among Langmuir probes far exceeding anything previously attained. (2) The isoenergetic argument for the retention of equipotential surface shapes in passing from Laplace's to Poisson's equation. (3) An explanation why the current concentration lines do not follow electrostatic field lines above saturation by balancing the statistical and deterministic arguments.

Magnetic Forces on Gas Blast Interrupter Arcs Due to Electrode Shape

Nozzle electrode shape in a gas blast circuit interrupter can cause very large magnetic forces to act on the arc. A rapid and inexpensive method for computing these forces is described. A conformal mapping technique is used in approximating the non-symmetrical 3-dimensional electrode current distribution by a large number of straight line segments of current. Superposition of the effect of each element determines the field at points of interest in the arcing region. Significant advantage exists over methods using numerical solutions of partial differential equations when knowledge of the, field is required at relatively few points.

Blast wave impingement on a slender wedge moving at hypersonic speeds.

References 1 Harris, L. P. and Cobine, J. D., The significance of the Hall effect in three MHD generator configurations, American Society of Mechanical Engineers 60-WA-329 (1960). 2 Hurwitz, H., Kilb, R. W., and Sutton, G. W., Influence of tensor conductivity on current distribution in a MHD generator, J. Appl. Phys. 32, 205-216 (1961). 3 Crown, J. C., Analysis of magnetogasdynamic generators having segmented electrodes and anisotropic conductivity,' United Aircraft Corp. Rept. R-1852-2 (1961). 4 Schultz-Grunow, F. and Denzel, D. L., Calculation of the electric characteristics of an MHD generator with finite electrodes by conformal mapping under full consideration of tensor conductivity and a velocity profile, Second International Symposium on MHD Electrical Power Generation (European Nuclear Energy Agency and Organization for Economic Cooperation, Paris, 1964), pp. 661-676. 5 Celinski, Z. N. and Fischer, F. W., Two-dimensional analysis of MHD generators with segmented electrodes, Institut fur Plasmaphysik, Garching, Germany, Rept. IPP 3/26 (1965). 6 Hoffman, M. A. and Gates, G. C., Electrode current distribution in linear M. G. D. channel flows, Sixth Symposium on Engineering Aspects of Magnetohydrodynamics (University of Pittsburgh, Pittsburgh, Pa., 1965), p. 34. 7 Witalis, E. A., Analysis of linear MHD power generators, Aktiebolaget Atomenergi, Stockholm, Sweden, AE-175 (1965).