Documents disponibles écrits par cet auteur

Effect of geometry of the plenum chamber on gas distribution in a fluidized bed / Ali Mohammadkhah in Industrial & engineering chemistry research, Vol. 48 N° 16 (Août 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 16 (Août 2009) . - pp. 7624–7630 Titre : Effect of geometry of the plenum chamber on gas distribution in a fluidized bed Type de document : texte imprimé Auteurs : Ali Mohammadkhah, Auteur ; Navid Mostoufi, Auteur Année de publication : 2009 Article en page(s) : pp. 7624–7630 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Fluidized  bed  Plenum  chambersComputational  fluid  dynamics  technique Résumé : The computational fluid dynamics (CFD) technique was used to simulate a fluidized bed with eight different plenum chambers of different design. The effect of the geometry of the plenum chamber on the velocity profile on the distributor and the pressure drop across the distributor was investigated. The plenums were selected such that the influence of characteristics such as body shape, direction and location of gas entrance, entrance type, and existence and shape of the internal baffle could be studied. The results indicate that the geometry of the body and the existence of the baffle are the most important characteristics that affect the flow uniformity above the distributor. It was shown that the shape of the baffle does not have a remarkable impact on the velocity profile. The direction and location of the gas entrance each has a significant effect on the distribution quality. The downward injection of gas and placement of the gas entrance far enough from the distributor increases the uniformity of flow over the distributor. It was shown that the geometry of the plenum chamber affects the total pressure drop across the distributor. A correction factor was introduced to quantify the effect of the geometry of the plenum on the pressure drop of the perforated plate distributor. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9001684 [article] Effect of geometry of the plenum chamber on gas distribution in a fluidized bed [texte imprimé] / Ali Mohammadkhah, Auteur ; Navid Mostoufi, Auteur . - 2009 . - pp. 7624–7630. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 16 (Août 2009) . - pp. 7624–7630 Mots-clés : Fluidized  bed  Plenum  chambersComputational  fluid  dynamics  technique Résumé : The computational fluid dynamics (CFD) technique was used to simulate a fluidized bed with eight different plenum chambers of different design. The effect of the geometry of the plenum chamber on the velocity profile on the distributor and the pressure drop across the distributor was investigated. The plenums were selected such that the influence of characteristics such as body shape, direction and location of gas entrance, entrance type, and existence and shape of the internal baffle could be studied. The results indicate that the geometry of the body and the existence of the baffle are the most important characteristics that affect the flow uniformity above the distributor. It was shown that the shape of the baffle does not have a remarkable impact on the velocity profile. The direction and location of the gas entrance each has a significant effect on the distribution quality. The downward injection of gas and placement of the gas entrance far enough from the distributor increases the uniformity of flow over the distributor. It was shown that the geometry of the plenum chamber affects the total pressure drop across the distributor. A correction factor was introduced to quantify the effect of the geometry of the plenum on the pressure drop of the perforated plate distributor. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9001684

Evaluating the probabilities of fluidization regimes / Milad Aghabararnejad in Industrial & engineering chemistry research, Vol. 50 N° 8 (Avril 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 8 (Avril 2011) . - pp. 4245–4251 Titre : Evaluating the probabilities of fluidization regimes Type de document : texte imprimé Auteurs : Milad Aghabararnejad, Auteur ; Navid Mostoufi, Auteur ; Rahmat Sotudeh-Gharebagh, Auteur Année de publication : 2011 Article en page(s) : pp. 4245–4251 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Probabilities  fluidization  regimes Résumé : Probabilities of fluidization regimes were determined experimentally using frequency domain analysis of pressure fluctuation data. It was assumed that regime transition does not occur at a distinct gas velocity and fluidization regimes coexist at each gas velocity. Three different flow structures (macro-, meso-, and microstructures) were recognized in a fluidized bed. Macrostructure is represented by bubbles, mesostructures are represented by clusters, and microstructure is represented by particles. These structures are the characteristics of bubbling, turbulent, and fast fluidization regimes. Regime probabilities were determined using power spectrum energies of these structures. Experiments were carried out in a 1 m high and 5 cm inner diameter glass column. Pressure fluctuations were measured using a piezoresistive pressure sensor. Sand particles with various diameters (150, 280, and 490 μm) and fluid catalytic cracking (FCC) particles (73 μm) were used as solids. Probabilities of fluidization regimes were calculated at various gas velocities. A new procedure was proposed for evaluating the regime probabilities versus gas velocity. It was shown that the proposed correlation is in good agreement with the experimental data and is noticeably better than the method proposed in the literature. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100642b [article] Evaluating the probabilities of fluidization regimes [texte imprimé] / Milad Aghabararnejad, Auteur ; Navid Mostoufi, Auteur ; Rahmat Sotudeh-Gharebagh, Auteur . - 2011 . - pp. 4245–4251. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 8 (Avril 2011) . - pp. 4245–4251 Mots-clés : Probabilities  fluidization  regimes Résumé : Probabilities of fluidization regimes were determined experimentally using frequency domain analysis of pressure fluctuation data. It was assumed that regime transition does not occur at a distinct gas velocity and fluidization regimes coexist at each gas velocity. Three different flow structures (macro-, meso-, and microstructures) were recognized in a fluidized bed. Macrostructure is represented by bubbles, mesostructures are represented by clusters, and microstructure is represented by particles. These structures are the characteristics of bubbling, turbulent, and fast fluidization regimes. Regime probabilities were determined using power spectrum energies of these structures. Experiments were carried out in a 1 m high and 5 cm inner diameter glass column. Pressure fluctuations were measured using a piezoresistive pressure sensor. Sand particles with various diameters (150, 280, and 490 μm) and fluid catalytic cracking (FCC) particles (73 μm) were used as solids. Probabilities of fluidization regimes were calculated at various gas velocities. A new procedure was proposed for evaluating the regime probabilities versus gas velocity. It was shown that the proposed correlation is in good agreement with the experimental data and is noticeably better than the method proposed in the literature. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100642b

Improved modeling of bubble column reactors by considering the bubble size distribution / Mohammad Ramezani in Industrial & engineering chemistry research, Vol. 51 N° 16 (Avril 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 16 (Avril 2012) . - pp. 5705-5714 Titre : Improved modeling of bubble column reactors by considering the bubble size distribution Type de document : texte imprimé Auteurs : Mohammad Ramezani, Auteur ; Navid Mostoufi, Auteur ; Mohammad Reza Mehrnia, Auteur Année de publication : 2012 Article en page(s) : pp. 5705-5714 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Particle  size  distribution  Bubble  Reactor  Bubble  column  Modeling Résumé : Bioconversion of glucose to gluconic acid with glucose oxidase as enzyme was considered to occur in a bubble column reactor at 40 °C, atmospheric pressure, and pH 5.5 while oxygen gas velocity was varied in the homogeneous and transition regime in the range of 0.0014-0.0112 m s-1. It was found that the superficial gas velocity has a positive effect on gas holdup, mean bubble size, and volumetric mass transfer coefficient, while the glucose concentration has a negative influence on these hydrodynamic parameters. The modeling of bubble column by considering the complete bubble size distribution in the governing equations was carried out in this work. The model was also solved by considering the single and double sizes of bubbles instead of complete bubble size distribution. It was shown that the results of the model, considering the complete bubble size distribution, is in a good agreement with the experimental data, while the considered single and double bubble sizes cannot predict the experimental data of oxygen concentration in the reactor properly. It was also found that the superficial gas velocity has a positive influence on oxygen concentration while glucose concentration has negative influence at low superficial gas velocity and positive influence at high gas velocity. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=25834484 [article] Improved modeling of bubble column reactors by considering the bubble size distribution [texte imprimé] / Mohammad Ramezani, Auteur ; Navid Mostoufi, Auteur ; Mohammad Reza Mehrnia, Auteur . - 2012 . - pp. 5705-5714. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 16 (Avril 2012) . - pp. 5705-5714 Mots-clés : Particle  size  distribution  Bubble  Reactor  Bubble  column  Modeling Résumé : Bioconversion of glucose to gluconic acid with glucose oxidase as enzyme was considered to occur in a bubble column reactor at 40 °C, atmospheric pressure, and pH 5.5 while oxygen gas velocity was varied in the homogeneous and transition regime in the range of 0.0014-0.0112 m s-1. It was found that the superficial gas velocity has a positive effect on gas holdup, mean bubble size, and volumetric mass transfer coefficient, while the glucose concentration has a negative influence on these hydrodynamic parameters. The modeling of bubble column by considering the complete bubble size distribution in the governing equations was carried out in this work. The model was also solved by considering the single and double sizes of bubbles instead of complete bubble size distribution. It was shown that the results of the model, considering the complete bubble size distribution, is in a good agreement with the experimental data, while the considered single and double bubble sizes cannot predict the experimental data of oxygen concentration in the reactor properly. It was also found that the superficial gas velocity has a positive influence on oxygen concentration while glucose concentration has negative influence at low superficial gas velocity and positive influence at high gas velocity. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=25834484

Nonlinear characterization of pressure fluctuations in fluidized beds / Reza Zarghami in Industrial & engineering chemistry research, Vol. 47 N° 23 (Décembre 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 N° 23 (Décembre 2008) . - p. 9497–9507 Titre : Nonlinear characterization of pressure fluctuations in fluidized beds Type de document : texte imprimé Auteurs : Reza Zarghami, Auteur ; Navid Mostoufi, Auteur ; Rahmat Sotudeh-Gharebagh, Auteur Année de publication : 2009 Article en page(s) : p. 9497–9507 Note générale : Chemistry engineering Langues : Anglais (eng) Mots-clés : Pressure  fluctuations  Fluidized  beds Résumé : Nonlinear time series analysis techniques were applied to predict pressure fluctuation data in fluidized beds in two different hydrodynamic states. The method of delays was used to reconstruct the state space attractor to carry out analysis in the reconstructed state space. The state space reconstruction parameters, i.e., time delay and embedding dimension, were determined and the results shown that their values were different for various types of methods introduced in the literature. Chaotic behavior and predictability of fluidized system were determined by introducing two nonlinear dynamic invariants, correlation dimension and entropy, in different ways. The traditional linear autoregression method and state space based prediction methods (SSBPMs), i.e., nearest neighbors and locally linear, and global linear methods, were applied to predict the pressure fluctuation signals. The quality of prediction was assessed by comparison of the predicted data with its original benchmark. In addition, the dynamic invariants of measured and predicted attractor of the pressure signals were compared. The results showed that SSBPMs are preferred to the traditional linear methods. Finally, a continuous uncertainty band of pressure signals of single and multiple bubble regimes for the prediction methods was presented. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800460f [article] Nonlinear characterization of pressure fluctuations in fluidized beds [texte imprimé] / Reza Zarghami, Auteur ; Navid Mostoufi, Auteur ; Rahmat Sotudeh-Gharebagh, Auteur . - 2009 . - p. 9497–9507. Chemistry engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N° 23 (Décembre 2008) . - p. 9497–9507 Mots-clés : Pressure  fluctuations  Fluidized  beds Résumé : Nonlinear time series analysis techniques were applied to predict pressure fluctuation data in fluidized beds in two different hydrodynamic states. The method of delays was used to reconstruct the state space attractor to carry out analysis in the reconstructed state space. The state space reconstruction parameters, i.e., time delay and embedding dimension, were determined and the results shown that their values were different for various types of methods introduced in the literature. Chaotic behavior and predictability of fluidized system were determined by introducing two nonlinear dynamic invariants, correlation dimension and entropy, in different ways. The traditional linear autoregression method and state space based prediction methods (SSBPMs), i.e., nearest neighbors and locally linear, and global linear methods, were applied to predict the pressure fluctuation signals. The quality of prediction was assessed by comparison of the predicted data with its original benchmark. In addition, the dynamic invariants of measured and predicted attractor of the pressure signals were compared. The results showed that SSBPMs are preferred to the traditional linear methods. Finally, a continuous uncertainty band of pressure signals of single and multiple bubble regimes for the prediction methods was presented. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800460f