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00453 Some computational aspects in the simulation of hydrodynamics in a trickle-bed reactor
16 Fuel science and technology (fundamental science, analysis, instrumentation) In order to optimize the performance of a thermoelectric device, an attempt is made to clarify the dependence on the temperature of its cold side and the size of the incisions made on its lateral faces. By means of experimental measurements and numerical simulations, the temperature difference between the hot and cold sides of the device is estimated, and the primary measures of performance, namely the electric power and the conversion efficiency, are examined for variations in the size of the incisions and in the cold-side temperature. The results of the simulations are in fairly good agreement with the experimental ones. Furthermore, the relationship between electrical power, conversion efficiency, and incision size were found to depend on the cold-side temperature.
seismic event has been carried out. An attempt has been made to quantify the initial leakage rate and average emptying time for the structure during seismic event after evaluating the various crack parameters, viz., crack-width and crack-spacing at the locations of interest. Finally, the seismic fragility of the structure is developed as families of conditional probability curves plotted against peak ground acceleration (PGA) parameter at the location of interest considering the randomness and uncertainty associated with various parameters that could affect the seismic structural response.
06/00447 Pareto-optimal solutions for multi-objective optimization of fed-batch bioreactors using non-dominated sorting genetic algorithm
Gfimfi, H. Radiafion Physics and ChemisU;v, 2005, 72, (1), 7 12. A simple stopping power formula, modified from that of Rohrlich and Carlson is presented. In this study analytical expressions for effective charge and effective mean excitation energies of target atoms in the modified Rohrlich and Carlson stopping power formula are used, while for effective charge of incoming electrons, Sugiyama's semi-empirical formula is used from Peterson and Green. The Lenz-Jensen statistical atomic density model has been used for calculations of effective charge and effective mean excitation energies. The calculated results of stopping power for electrons in the energy range from a few tens of electron volts to 10 MeV are found to be in good agreement to within 10% with the experimental data and a number of other calculations.
Sarkar, D. and Modak, J. M. Chenffcal Engineering Science, 2005, 60, (2), 481 492. Many optimal control problems are characterized by their multiple performance measures that are often non-commensurable and competing with each other. The presence of multiple objectives in a problem usually give rise to a set of optimal solutions, largely known as Paretooptimal solutions. Evolutionary algorithms have been recognized to be well suited for multi-objective optimization because of their capability to evolve a set of non-dominated solutions distributed along the Pareto front. This has led to the development of many evolutionary multiobjective optimization algorithms among which non-dominated sorting genetic algorithm (NSGA and its enhanced version NSGA-II) has been found effective in solving a wide variety of problems. Recently, the authors reported a genetic algorithm based technique for solving dynamic single-objective optimization problems, with single as well as multiple control wlriables, that appear in fed-batch bioreactor applications. The purpose of this study is to extend this methodology for solution of multi-objective optimal control problems under the framework of NSGA-II. The applicability of the technique is illustrated by solving two optimal control problems, taken from literature, which have usually been solved by several methods as single-objective dynamic optimization problems.
06/00448 Performance of experimental carbon blacks in aqueous supercapacitors Toupin, M. el al. Journal of Power Sources, 2005, 140, (1), 203 210. Four samples of carbon black were synthesized for use in aqueous supercapacitors. They were designed to have different surface areas and pore size distributions. The objectives were to identify the attributes that are necessary to obtain a high specific capacitance and to attempt to correlate different physical characteristics of the carbon electrodes with their capacitance. A fifth carbon was obtained from another laboratory for comparison. Carbon electrodes were analysed using both acidic and alkaline electrolytes. Their capacitance was measured at room temperature and at -40°C, using slow sweep cyclic voltammetry. Electrochemical impedance spectroscopy was also performed on the carbon electrodes using the same electrolytes and temperatures. The results from these measurements are discussed in terms of the surface areas and pore size distributions of the samples, which were measured using the BET technique.
06•00449 Real-time simulation using graceful degradation of accuracy Vityaz, O. and Zimmermann, G. Energy and Buildings, 2005, 37, (8), 795 806. Real-time computer simulation is required in a number of applications, where the simulated dynamic systems are directly coupled with systems in the real world or with other systems also running in real-time. Typical problems of real-time simulations are that the dynamics of the modelled system are not represented in enough detail, either by not sampling the inputs or not producing output values frequently enough or both. Increasing the sampling frequencies may lead, as an additional problem, to real-time violations caused by insufficient computing power. The latter problem is amplified if the real-time is accelerated to achieve a kind of fast motion and reduce experiment times. This paper shows how the first problem can be solved by automatic frequency adjustment, minimizing the number of computations and how the remaining second problem can be reduced by trading a graceful degradation of accuracy against the computing power requirements automatically. Experiments show that simulation times could be reduced by a factor of 100 without unacceptable simulation errors.
06/00450 Seismic response and fragility analysis of a water storage structure Bhargava, K. et al. 1481 1501. Stress analysis of a static and seismic assessment of most
Nuclear Engineering and Design, 2005, 235, (14), water storage structure has been carried out for loading. Based on the stress analyses results, likely failure modes for the structure caused by
06/00451 Simple stopping power formula for low and intermediate energy electrons
06•00452 Solving advanced network reliability problems by means of cellular automata and Monte Carlo sampling Rocco, C. M. and Zio, E. Reliability Engineering & System S~]2~t)', 2005, 89, (2), 219 226. This paper extends the cellular automata-based, Monte Carlo sampling methodology for computing network reliability, previously proposed by the first author. The extension regards the development of cellular automata for the solution of the all-terminal and k-terminal connection problems and the maximum unsplittable flow problem, which can be considered as a particular, simplified case of the maximum flow distribution problem. The algorithms developed are presented in detail and verified on literature cases.
06•00453 Some computational aspects in the simulation of hydrodynamics in a trickle-bed reactor Souadnia, A. et at. Chemical Engineering and Processing, 2005, 44, (8), 847 854. In this paper, the general multi-material formulation of Kashiwa and Rauenzahn is used to derive an appropriate hydrodynamic model for a trickle-bed reactor operating under trickling flow conditions. Using some realistic assumptions, the resulting model consists of two equations in two unknowns, i.e. liquid volume fraction and pressure. Moreover, the equations exhibit elliptic (pressure) and hyperbolic (volume fraction) behaviours, which require the use of different numerical methods in order to correctly handle these different numerical behaviours. Thus, the finite volume method, the CrankNicholson scheme and the second order Godunov's method combined with the solution of Riemann problem were implemented. The numerical results of pressure drops derived from the model solution are shown to be in good agreement with the values measured in the same operating conditions or previously published in the literature.
06/00454 Study of models for predicting the diffuse irradiance on inclined surfaces Li, D. H. W. and Cheung, G. H. Applied Energy, 2005, 81, (2), 170 186. Solar irradiance data on various inclined surfaces at different orientations are important information for active solar-system analyses and passive energy-efficient building designs. In many parts of the world, however, the basic solar irradiance data for the surfaces of interest are not always readily available. Traditionally, different mathematical models have been developed to predict the solar irradiance on various inclined surfaces using 'horizontal' data. Alternatively, the diffuse irradiance of a sloping plane can be calculated by integrating the radiance distribution generated with a sky radiance model. This paper presents the evaluation of two slope irradiance models, namely, the Perez point-source model (PEREZSIM) and the Muneer model (MUNEERSIM), and two sky-distribution models, namely, the Perez all-weather model (PEREZSDM) and the Kittler standard-sky model (KITTLERSDM). Three-year (1999-2001) measured average hourly sky radiance and horizontal sky diffuse irradiance data were used for the model assessment. Statistical results showed that all four models can accurately predict the solar irradiance of a 22.3 ° (latitude angle of Hong Kong) inclined south-oriented surface, indicating the good predictive ability for modelling an inclined surface with a small tilted angle. In general, the KITTLERSDM and PEREZSIM show the best predictions for vertical solar irradiance at this location, followed by the PEREZSDM, then the MUNEERSIM.
Fuel and Energy Abstracts
January 2006
61
seismic event has been carried out. An attempt has been made to quantify the initial leakage rate and average emptying time for the structure during seismic event after evaluating the various crack parameters, viz., crack-width and crack-spacing at the locations of interest. Finally, the seismic fragility of the structure is developed as families of conditional probability curves plotted against peak ground acceleration (PGA) parameter at the location of interest considering the randomness and uncertainty associated with various parameters that could affect the seismic structural response.
06/00447 Pareto-optimal solutions for multi-objective optimization of fed-batch bioreactors using non-dominated sorting genetic algorithm
Gfimfi, H. Radiafion Physics and ChemisU;v, 2005, 72, (1), 7 12. A simple stopping power formula, modified from that of Rohrlich and Carlson is presented. In this study analytical expressions for effective charge and effective mean excitation energies of target atoms in the modified Rohrlich and Carlson stopping power formula are used, while for effective charge of incoming electrons, Sugiyama's semi-empirical formula is used from Peterson and Green. The Lenz-Jensen statistical atomic density model has been used for calculations of effective charge and effective mean excitation energies. The calculated results of stopping power for electrons in the energy range from a few tens of electron volts to 10 MeV are found to be in good agreement to within 10% with the experimental data and a number of other calculations.
Sarkar, D. and Modak, J. M. Chenffcal Engineering Science, 2005, 60, (2), 481 492. Many optimal control problems are characterized by their multiple performance measures that are often non-commensurable and competing with each other. The presence of multiple objectives in a problem usually give rise to a set of optimal solutions, largely known as Paretooptimal solutions. Evolutionary algorithms have been recognized to be well suited for multi-objective optimization because of their capability to evolve a set of non-dominated solutions distributed along the Pareto front. This has led to the development of many evolutionary multiobjective optimization algorithms among which non-dominated sorting genetic algorithm (NSGA and its enhanced version NSGA-II) has been found effective in solving a wide variety of problems. Recently, the authors reported a genetic algorithm based technique for solving dynamic single-objective optimization problems, with single as well as multiple control wlriables, that appear in fed-batch bioreactor applications. The purpose of this study is to extend this methodology for solution of multi-objective optimal control problems under the framework of NSGA-II. The applicability of the technique is illustrated by solving two optimal control problems, taken from literature, which have usually been solved by several methods as single-objective dynamic optimization problems.
06/00448 Performance of experimental carbon blacks in aqueous supercapacitors Toupin, M. el al. Journal of Power Sources, 2005, 140, (1), 203 210. Four samples of carbon black were synthesized for use in aqueous supercapacitors. They were designed to have different surface areas and pore size distributions. The objectives were to identify the attributes that are necessary to obtain a high specific capacitance and to attempt to correlate different physical characteristics of the carbon electrodes with their capacitance. A fifth carbon was obtained from another laboratory for comparison. Carbon electrodes were analysed using both acidic and alkaline electrolytes. Their capacitance was measured at room temperature and at -40°C, using slow sweep cyclic voltammetry. Electrochemical impedance spectroscopy was also performed on the carbon electrodes using the same electrolytes and temperatures. The results from these measurements are discussed in terms of the surface areas and pore size distributions of the samples, which were measured using the BET technique.
06•00449 Real-time simulation using graceful degradation of accuracy Vityaz, O. and Zimmermann, G. Energy and Buildings, 2005, 37, (8), 795 806. Real-time computer simulation is required in a number of applications, where the simulated dynamic systems are directly coupled with systems in the real world or with other systems also running in real-time. Typical problems of real-time simulations are that the dynamics of the modelled system are not represented in enough detail, either by not sampling the inputs or not producing output values frequently enough or both. Increasing the sampling frequencies may lead, as an additional problem, to real-time violations caused by insufficient computing power. The latter problem is amplified if the real-time is accelerated to achieve a kind of fast motion and reduce experiment times. This paper shows how the first problem can be solved by automatic frequency adjustment, minimizing the number of computations and how the remaining second problem can be reduced by trading a graceful degradation of accuracy against the computing power requirements automatically. Experiments show that simulation times could be reduced by a factor of 100 without unacceptable simulation errors.
06/00450 Seismic response and fragility analysis of a water storage structure Bhargava, K. et al. 1481 1501. Stress analysis of a static and seismic assessment of most
Nuclear Engineering and Design, 2005, 235, (14), water storage structure has been carried out for loading. Based on the stress analyses results, likely failure modes for the structure caused by
06/00451 Simple stopping power formula for low and intermediate energy electrons
06•00452 Solving advanced network reliability problems by means of cellular automata and Monte Carlo sampling Rocco, C. M. and Zio, E. Reliability Engineering & System S~]2~t)', 2005, 89, (2), 219 226. This paper extends the cellular automata-based, Monte Carlo sampling methodology for computing network reliability, previously proposed by the first author. The extension regards the development of cellular automata for the solution of the all-terminal and k-terminal connection problems and the maximum unsplittable flow problem, which can be considered as a particular, simplified case of the maximum flow distribution problem. The algorithms developed are presented in detail and verified on literature cases.
06•00453 Some computational aspects in the simulation of hydrodynamics in a trickle-bed reactor Souadnia, A. et at. Chemical Engineering and Processing, 2005, 44, (8), 847 854. In this paper, the general multi-material formulation of Kashiwa and Rauenzahn is used to derive an appropriate hydrodynamic model for a trickle-bed reactor operating under trickling flow conditions. Using some realistic assumptions, the resulting model consists of two equations in two unknowns, i.e. liquid volume fraction and pressure. Moreover, the equations exhibit elliptic (pressure) and hyperbolic (volume fraction) behaviours, which require the use of different numerical methods in order to correctly handle these different numerical behaviours. Thus, the finite volume method, the CrankNicholson scheme and the second order Godunov's method combined with the solution of Riemann problem were implemented. The numerical results of pressure drops derived from the model solution are shown to be in good agreement with the values measured in the same operating conditions or previously published in the literature.
06/00454 Study of models for predicting the diffuse irradiance on inclined surfaces Li, D. H. W. and Cheung, G. H. Applied Energy, 2005, 81, (2), 170 186. Solar irradiance data on various inclined surfaces at different orientations are important information for active solar-system analyses and passive energy-efficient building designs. In many parts of the world, however, the basic solar irradiance data for the surfaces of interest are not always readily available. Traditionally, different mathematical models have been developed to predict the solar irradiance on various inclined surfaces using 'horizontal' data. Alternatively, the diffuse irradiance of a sloping plane can be calculated by integrating the radiance distribution generated with a sky radiance model. This paper presents the evaluation of two slope irradiance models, namely, the Perez point-source model (PEREZSIM) and the Muneer model (MUNEERSIM), and two sky-distribution models, namely, the Perez all-weather model (PEREZSDM) and the Kittler standard-sky model (KITTLERSDM). Three-year (1999-2001) measured average hourly sky radiance and horizontal sky diffuse irradiance data were used for the model assessment. Statistical results showed that all four models can accurately predict the solar irradiance of a 22.3 ° (latitude angle of Hong Kong) inclined south-oriented surface, indicating the good predictive ability for modelling an inclined surface with a small tilted angle. In general, the KITTLERSDM and PEREZSIM show the best predictions for vertical solar irradiance at this location, followed by the PEREZSDM, then the MUNEERSIM.
Fuel and Energy Abstracts
January 2006
61