27 research outputs found
Three-dimensional CFD modeling of transport phenomena in anode-supported planar SOFCs
No full textIn this study, a three-dimensional computational fluid dynamics model has been developed for an anode-supported planar SOFC. The conservation equations of mass, momentum, species/charges and thermal energy are solved by finite volume method for a complete unit cell consisting of 13 parallel channels in both anode and cathode. The simulation results of the developed model are well in agreement with the experimental data obtained at same conditions. In this study, the co-flow arrangement with hydrogen utilization of 60 % and operating voltage of 0.7 V is used as the base case, and compared with the counter-flow arrangement. The predicted results reveals that the maximum temperature obtained in the counter-flow arrangement is about 10 A degrees C lower than that of co-flow, but the counter-flow arrangement has a higher temperature gradient between the respective anodes and cathodes in a cross-section normal to the main flow direction, especially in the air inlet region of the cell (x = 0.04 m),which is very harmful to the lifetime of materials. The current density is very unevenly distributed along and normal to the flow direction for both the co- and counter-flow arrangements, and the maximum values occur at junctions of the electrodes, channels and ribs, which causes higher over-potentials and ohmic heating
Three-dimensional CFD modeling of transport phenomena in multi-channel anode-supported planar SOFCs
No full textIn this study, a three-dimensional computational fluid dynamics (CFD) model is developed and applied for anode-supported planar SOFC involving multi-channels. The developed model is first validated in agreement with the experimental data obtained at same conditions. Three different flow arrangements (co-, counter- and cross-flow) are simulated and compared in terms of cell overall performance and various transport phenomena occurred inside the SOFC single cell functional components. Local distribution of temperature, mass flow rate, current density, gas concentrations of reactants and products in both fuel and air sides under different flow arrangements is predicted and presented. It is found that the co-flow and counter-flow arrangements have a better performance than that of the cross-flow arrangement at the same operating conditions. It is also found that the temperature for the three flow arrangements is unevenly distributed and the significant temperature gradients exist along the length of the cell. The mass flow rate of fuel at the inlet of each channel is uniform, however its difference between the side channel and the channel at the center is increasing along the fuel flow direction, which reaches a maximum value at the outlet region. It is also predicted that the maximum current density is located at the interfaces between the channels, ribs and the electrodes resulting in a large over-potential and a heat source in the electrodes, which is harmful to the cell overall performance and working life time. (C) 2015 Elsevier Ltd. All rights reserved
The revision of an orientalist to a reoriented image : Arab women in The Algerian Quartet by Assia Djebar
No full textCette thèse porte sur l’œuvre d’Assia Djebar qui est une des plus grandes représentantes de la littérature maghrébine de langue française. Elle met à profit les nombreux travaux occidentaux déjà menés sur cette œuvre en les infléchissant et en les prolongeant par une approche personnelle qui s’attache à montrer comment l’écriture de cette écrivaine postcoloniale a contribué à renouveler la représentation des femmes arabes.La première partie fait d’abord le point sur la constitution de stéréotypes popularisés par les représentations orientalistes qui réduisaient les femmes orientales au statut d’objet esthétique et fantasmatique puis sur les apports des théories (théorie postcoloniale ; courants féministes) qui ont permis la déconstruction de l’approche orientaliste et de son idéologie sous-jacente. La deuxième partie montre comment l’écriture d’Assia Djebar s’inscrit dans cette perspective féministe postcoloniale. Ses récits donnent à de nombreux personnages de femmes algériennes des sensibilités, des modalités expressives, des rôles historiques et sociaux qui en font des sujets pleins et complexes. La troisième partie se concentre sur l’autoportrait de l’écrivaine qui s’affirme en tant que femme d’origine arabo-berbère assumant une hybridité culturelle et identitaire qui se traduit par les innovations génériques, poétiques et linguistiques de ses récits.This thesis focuses on the work of Assis Djebar, one of the greatest representatives of Francophone Maghreb literature. It draws on numerous works on this literature already published by modifying their approach and adding a personal perspective to show how this postcolonial writer renews the representation of Arab women.The first part of this study shows how the popular stereotypes invented by Orientalists reduced women to fantasmatic and aesthetic objects but the contribution of certain theories (postcolonial and feminist) have allowed the deconstruction of this Orientalism and its underlying ideology. The second part shows how Assia Djebar’s writing fits into the postcolonial feminist perspective. The author attributes many Algerian women characters with sensibilities, expressive modes, social and historical roles that make them fully-rounded and complex people. The third part focuses on the self-portrait of the author as a woman of Arab-Berber origin who recognises herself as a cultural and identity hybrid, reflected in the generic, poetic and linguistic innovations of her work
Parameter Study of Transport Processes with Catalytic Reactions in Intermediate Temperature Solid Oxide Fuel Cells
No full textAnalysis of Transport Processes and Chemical Reaction in Combustion Duct of Compact Methane Reformer
No full textA composite combustion duct in compact methane reformers consists of a gas flow channel, porous layer and solid plates. There are various transport processes appeared, such as gas flow in the channel, multi-component species convection/diffusion in the porous layer, and heat transfer. They are further coupled by methane catalytic combustion in the porous layer, which affects the reformer overall performance and reliability. By three dimensional CFD approach, the reacting gas flow and heat transfer processes were numerically studied. The reformer conditions such as mass balances associated with the chemical reaction and gas permeation to/from the porous layer are implemented in the calculation. The results reveal that the catalytic combustion reaction is confined in a thin porous catalyst area close to fuel gas flow duct. Transport processes of the fuel gas species and temperature distribution are significantly affected by the reactions.</jats:p
Transport Phenomena Coupled by Chemical Reactions in Methane Reforming Ducts
No full textMass, heat and momentum transport processes are strongly coupled with catalytic chemical reactions in a methane steam reforming duct. In this paper, a three-dimensional calculation method is developed to simulate and analyze reforming reactions of methane, and the effects on various transport processes in a steam reforming duct. The results show that the design and operating parameters grouped as characteristic ratios have significant effects on the transport phenomen
Transport Phenomena Coupled by Chemical Reactions in Methane Reforming Ducts
No full textMass, heat and momentum transport processes are strongly coupled with catalytic chemical reactions in a methane steam reforming duct. In this paper, a three-dimensional calculation method is developed to simulate and analyze reforming reactions of methane, and the effects on various transport processes in a steam reforming duct. The results show that the design and operating parameters grouped as characteristic ratios have significant effects on the transport phenomen
Analysis of Chemically Reacting Gas Flow and Heat Transfer in Methane Reforming Processes
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