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Mohamed S. El-genk - One of the best experts on this subject based on the ideXlab platform.

  • Simulation of fission heated single-cell thermionic fuel elements in presence of oxygen using uniform electric heating
    Space technology and applications international forum (STAIF - 97), 1997
    Co-Authors: Dmitry V. Paramonov, Mohamed S. El-genk
    Abstract:

    This paper investigated the accuracy of simulating fission heated single-cell Thermionic Fuel Elements (TFEs) using uniform electric heating in the presence of oxygen in the Interelectrode Gap. The electrodes temperatures current densities, and the tungsten loss rates from the emitter surface were calculated and compared for both heating options. The effect of oxygen presence in the Interelectrode Gap on the TFE performance was also compared for fission and electrically heating TFE. Electrical heating results in a more uniform axial distributions of emitter temperature, current density, and tungsten loss rate distributions in the central part of the TFE compared to fission heating. Results show that introducing oxygen into the Interelectrode Gap reduces the output electric power for both fission and electrically heated TFEs. For example, at an effective oxygen pressure of 5×10−9 torr and O/W atom ratio in the tungsten oxides deposits on the collector surface of 0.66, the electric power output at Qth=3500 ...

  • ‘‘TITAM’’ thermionic integrated transient analysis model: Load‐following of a single‐cell TFE
    AIP Conference Proceedings, 1992
    Co-Authors: Mohamed S. El-genk, Huimin Xue, Christopher S. Murray, Shobhik Chaudhuri
    Abstract:

    TITAM, a dynamic model that simulates transient and steady‐state operation of a fully integrated single‐cell thermionic fuel element (TFE), has been developed. Operation modes investigated include transient response to a step input in reactivity, effects of changing the Cs pressure and/or the width of the Interelectrode Gap on the load electric power, overall conversion efficiency, and the load‐following characteristics of a TFE. Results show that although the nuclear reactor is always load following, a TFE is only partially load‐following. Results also show that in a thermionic (TI) nuclear power system, which employs single‐cell TFEs having a large Interelectrode Gap, it is desirable to conserve Cs by lowering its vapor pressure at the beginning‐of‐life, since increasing the Cs pressure insignificantly affects the load electric power. However, should fuel swelling, after operating for an extended period of time, reduce the width of the Interelectrode Gap, both the conversion efficiency and the load elec...

  • Effect of oxygen on performance and mass transport in a single-cell thermionic fuel element
    IECEC 96. Proceedings of the 31st Intersociety Energy Conversion Engineering Conference, 1
    Co-Authors: Dmitry V. Paramonov, Mohamed S. El-genk
    Abstract:

    The introduction of tracer amounts of oxygen into the Interelectrode Gap of a thermionic converter has been shown to improve converter performance. Excess oxygen, however, increases the loss rate of emitter material, reducing the converter performance and shortening its lifetime, owing to the increase in the effective emissivity of the electrodes, the change in the collector work function, and the deposition of emitter material oxides on spacers and insulators. In this paper, a model was developed which calculated the emitter material loss rate, composition of the emitter material deposits on the collector surface and investigated the effect of performance of a single-cell thermionic fuel element (TFE) in the presence of oxygen and cesium oxides in the Interelectrode Gap. The amount of oxygen and the cesium pressure in the Interelectrode Gap were varied parametrically and the TFE volt-ampere characteristics, and axial distributions of current density and emitter material loss rate along the TFE were calculated.

Ludvig Edman - One of the best experts on this subject based on the ideXlab platform.

Joonho Shin - One of the best experts on this subject based on the ideXlab platform.

J.m. Bisang - One of the best experts on this subject based on the ideXlab platform.

  • Mass-transfer studies in an electrochemical reactor with a small Interelectrode Gap
    Electrochimica Acta, 2013
    Co-Authors: Alejandro Nicolás Colli, R. Toelzer, M. E. H. Bergmann, J.m. Bisang
    Abstract:

    Abstract This paper reports the distribution of the local mass-transfer coefficient along the electrode length for an electrochemical reactor with parallel-plate electrodes and narrow Interelectrode Gaps of 1 and 2.2 mm, using the reduction of ferricyanide as a test reaction. The studies were performed at different flow rates, Reynolds numbers ranging from 370 to 3700, with the empty reactor and also the Interelectrode Gap was filled with two types of expanded plastics and a woven plastic mesh as turbulence promoters. The effect of both the Interelectrode Gap and the partial placing of the turbulence promoter along the electrode length on the mass-transfer behaviour was also analyzed. In all cases the pressure drop across the reactor was measured. A more uniform distribution of the local mass-transfer coefficient, ±15% related to its mean value, and an important increase of the mean mass-transfer coefficient, enhancement factor ranging from 2 to 8, were observed, depending on the type of turbulence promoter, the volumetric flow rate, and the Interelectrode Gap.

Dmitry V. Paramonov - One of the best experts on this subject based on the ideXlab platform.

  • Simulation of fission heated single-cell thermionic fuel elements in presence of oxygen using uniform electric heating
    Space technology and applications international forum (STAIF - 97), 1997
    Co-Authors: Dmitry V. Paramonov, Mohamed S. El-genk
    Abstract:

    This paper investigated the accuracy of simulating fission heated single-cell Thermionic Fuel Elements (TFEs) using uniform electric heating in the presence of oxygen in the Interelectrode Gap. The electrodes temperatures current densities, and the tungsten loss rates from the emitter surface were calculated and compared for both heating options. The effect of oxygen presence in the Interelectrode Gap on the TFE performance was also compared for fission and electrically heating TFE. Electrical heating results in a more uniform axial distributions of emitter temperature, current density, and tungsten loss rate distributions in the central part of the TFE compared to fission heating. Results show that introducing oxygen into the Interelectrode Gap reduces the output electric power for both fission and electrically heated TFEs. For example, at an effective oxygen pressure of 5×10−9 torr and O/W atom ratio in the tungsten oxides deposits on the collector surface of 0.66, the electric power output at Qth=3500 ...

  • Effect of oxygen on performance and mass transport in a single-cell thermionic fuel element
    IECEC 96. Proceedings of the 31st Intersociety Energy Conversion Engineering Conference, 1
    Co-Authors: Dmitry V. Paramonov, Mohamed S. El-genk
    Abstract:

    The introduction of tracer amounts of oxygen into the Interelectrode Gap of a thermionic converter has been shown to improve converter performance. Excess oxygen, however, increases the loss rate of emitter material, reducing the converter performance and shortening its lifetime, owing to the increase in the effective emissivity of the electrodes, the change in the collector work function, and the deposition of emitter material oxides on spacers and insulators. In this paper, a model was developed which calculated the emitter material loss rate, composition of the emitter material deposits on the collector surface and investigated the effect of performance of a single-cell thermionic fuel element (TFE) in the presence of oxygen and cesium oxides in the Interelectrode Gap. The amount of oxygen and the cesium pressure in the Interelectrode Gap were varied parametrically and the TFE volt-ampere characteristics, and axial distributions of current density and emitter material loss rate along the TFE were calculated.