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Computational fluid dynamics simulation of regime transition in bubble columns incorporating the dual-bubble-size model / Jianhua Chen in Industrial & engineering chemistry research, Vol. 48 N° 17 (Septembre 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8172–8179 Titre : Computational fluid dynamics simulation of regime transition in bubble columns incorporating the dual-bubble-size model Type de document : texte imprimé Auteurs : Jianhua Chen, Auteur ; Ning Yang, Auteur ; Wei Ge, Auteur Année de publication : 2009 Article en page(s) : pp. 8172–8179 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Regime  transition  Bubble  columns  Dual-bubble-size  model  Computational  fluid  dynamics  simulation Résumé : This article investigates the two regime transition points for bubble columns with the so-called dual-bubble-size (DBS) model featuring the utilization of a stability condition to analyze the compromise between dominant mechanisms. Our previous work indicated that the second point could be reasonably predicted and physically interpreted by the DBS model for various gas−liquid systems. This work further clarifies the relationship between the bifurcation of energy dissipation and of structural parameters and the regime transition. It is found that the bifurcation of energy dissipation exists for both the gas−liquid and gas−solid systems and can be used to predict and understand regime transition in multiphase flow. Then the DBS model is incorporated into the two-fluid model for calculating interphase coupling, and a computational fluid dynamics (CFD) calculation is performed to simulate a bubble column. The “shoulder” on the gas hold-up curve can be observed in the simulation with the new coupling method, and the second transition point predicted from the CFD simulation is consistent with experiments and the calculation of the DBS model. Sparger effects are investigated through the two simulation cases for uniform aeration and local aeration, and the radial distribution of local hydrodynamic parameters is comparable with experimental data in the literature. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801644d [article] Computational fluid dynamics simulation of regime transition in bubble columns incorporating the dual-bubble-size model [texte imprimé] / Jianhua Chen, Auteur ; Ning Yang, Auteur ; Wei Ge, Auteur . - 2009 . - pp. 8172–8179. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8172–8179 Mots-clés : Regime  transition  Bubble  columns  Dual-bubble-size  model  Computational  fluid  dynamics  simulation Résumé : This article investigates the two regime transition points for bubble columns with the so-called dual-bubble-size (DBS) model featuring the utilization of a stability condition to analyze the compromise between dominant mechanisms. Our previous work indicated that the second point could be reasonably predicted and physically interpreted by the DBS model for various gas−liquid systems. This work further clarifies the relationship between the bifurcation of energy dissipation and of structural parameters and the regime transition. It is found that the bifurcation of energy dissipation exists for both the gas−liquid and gas−solid systems and can be used to predict and understand regime transition in multiphase flow. Then the DBS model is incorporated into the two-fluid model for calculating interphase coupling, and a computational fluid dynamics (CFD) calculation is performed to simulate a bubble column. The “shoulder” on the gas hold-up curve can be observed in the simulation with the new coupling method, and the second transition point predicted from the CFD simulation is consistent with experiments and the calculation of the DBS model. Sparger effects are investigated through the two simulation cases for uniform aeration and local aeration, and the radial distribution of local hydrodynamic parameters is comparable with experimental data in the literature. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801644d

Modeling of regime transition in bubble columns with stability condition / Jianhua Chen in Industrial & engineering chemistry research, Vol. 48 N°1 (Janvier 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N°1 (Janvier 2009) . - P. 290-301 Titre : Modeling of regime transition in bubble columns with stability condition Type de document : texte imprimé Auteurs : Jianhua Chen, Editeur scientifique ; Ning Yang, Editeur scientifique ; Wei Ge, Editeur scientifique Année de publication : 2009 Article en page(s) : P. 290-301 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Regime  Transition  Hydrodynamique  Dual-bubble-size  (DBS) Résumé : Understanding the physical essence of regime transition is of crucial importance for the modeling and simulation of hydrodynamics and heat and mass transfer in bubble columns. The regime transition of the air−water system has been captured by the dual-bubble-size (DBS) model in our previous work [Yang et al. Chem. Eng. Sci. 2007, 62, 6978−6991] as a jump change from one minimum point of the stability criterion to the other. The DBS model features the incorporation of a stability condition with hydrodynamic conservation equations through the analysis of compromise between dominant mechanisms. This work reiterates our previous work and further explores some remaining issues and underlying physics related to the jump change by analyzing the trajectory of global minimum points in the three-dimensional space of structural parameters. The influence of drag coefficient correlations on the model prediction is investigated. The effect of liquid viscosity on regime transition is evaluated using the DBS model for saccharose and glycerin systems. The dual effects of liquid viscosity reported in literature, namely, suppressing the regime transition while slightly increasing viscosity and destabilizing the homogeneous regime at higher viscosity, can be reasonably predicted with this model. Finally, the concept of the compromise between dominant mechanisms is extended to understand the bubble behavior at different scales and its relationship with stability condition. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8003623 [article] Modeling of regime transition in bubble columns with stability condition [texte imprimé] / Jianhua Chen, Editeur scientifique ; Ning Yang, Editeur scientifique ; Wei Ge, Editeur scientifique . - 2009 . - P. 290-301. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N°1 (Janvier 2009) . - P. 290-301 Mots-clés : Regime  Transition  Hydrodynamique  Dual-bubble-size  (DBS) Résumé : Understanding the physical essence of regime transition is of crucial importance for the modeling and simulation of hydrodynamics and heat and mass transfer in bubble columns. The regime transition of the air−water system has been captured by the dual-bubble-size (DBS) model in our previous work [Yang et al. Chem. Eng. Sci. 2007, 62, 6978−6991] as a jump change from one minimum point of the stability criterion to the other. The DBS model features the incorporation of a stability condition with hydrodynamic conservation equations through the analysis of compromise between dominant mechanisms. This work reiterates our previous work and further explores some remaining issues and underlying physics related to the jump change by analyzing the trajectory of global minimum points in the three-dimensional space of structural parameters. The influence of drag coefficient correlations on the model prediction is investigated. The effect of liquid viscosity on regime transition is evaluated using the DBS model for saccharose and glycerin systems. The dual effects of liquid viscosity reported in literature, namely, suppressing the regime transition while slightly increasing viscosity and destabilizing the homogeneous regime at higher viscosity, can be reasonably predicted with this model. Finally, the concept of the compromise between dominant mechanisms is extended to understand the bubble behavior at different scales and its relationship with stability condition. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8003623