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Showing 3 results for Current Distribution
Volume 11, Issue 3 (10-2011)
Abstract
This paper presents the results of a study on the radiation characteristics of a plasma triangular antenna in the VHF band (30-300MHz) applying the method of moment. Deriving the current distribution of the antenna, it shows the relationship between radiation characteristics of the plasma antenna and the plasma parameters. Both theoretical and numerical results indicate that if the plasma frequency is sufficiently higher than the operating frequency and the collision frequency is correspondingly low, the radiation treatment of the plasma antenna will be close to a metal one. Also the consequence of simulations reveals the proposed plasma antenna has better peak gain than the conventional plasma column on the operating band. The results of the current study are checked by using full wave HFSS simulator.
Qadir Esmaili, Majid Eshagh Nimvari,
Volume 18, Issue 1 (3-2018)
Abstract
One of the most important factors in reducing the lifetime of PEM fuel cells is heterogeneous current distribution on membrane surface. Since flow field plays an important role in reactants distribution and water depletion and consequently current distribution, hence, in this paper, with development of a lumped model, water and current distributions on membrane surface were evaluated in two different designs. In this model, the flow field is divided into equal segments and connection between segments are created through flow field pattern. In both designs, flow field of anode side was serpentine, but on cathode side, parallel and serpentine flow field were used in first and second design, respectively. Simulations were carried out for different input relative humidity from 0 to 100 in both sides. The results showed that flow field had no significant effect on polarization curve and the second design had a little better performance in high current density. Also, in terms of current distribution, the second design shows a better uniformity, so that in the first design in fully saturated inlet condition, difference between the percentage of current generated between the first and last segments is about 1.57 percent which recehes to 1.45 percent in the second case.
L. Hendooie , R. Shafaghat, A. Ramiar, M. Dardel, Q. Esmaili,
Volume 19, Issue 7 (7-2019)
Abstract
One of the most important factors in decreasing the lifetime and inappropriate performance of PEM electrolyzers is the non-uniform current distribution on membrane surface. Since the smoothest distribution of species and water leads to optimal current distribution, in this research, a 1D- 1D model has been developed that explores the distribution of species and water, and finally the current distribution in layers and determines the optimal performance conditions of the high PEM membrane electrolyzers. In this model, the pressure is assumed constant throughout the channel, the cell temperature is constant, and the membrane is fully hydrated. The length of the anode and cathode channels is divided into 20 equal parts. By simultaneously solving the equations along the channel and perpendicular to it in each section, the distribution of species and current are obtained. The result showed that by increasing the average flow density, the flow distribution is smoother along the channel and, with increasing water flow, the current distribution is smoothed, but it has little effect on the polarization curve. Fick's effect on the distribution of species at the interface between the membrane and the gas diffusion layer has been investigated. Finally, the effect of thickness on the polarization curve is determined. By increasing the thickness of the membrane and the electrodes, the function of the system decreases.
