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Transition of bubbly flow in vertical tubes / A. K. Das in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 9 (Septembre 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 9 (Septembre 2009) . - 06 p. Titre : Transition of bubbly flow in vertical tubes : effect of bubble size and tube diameter Type de document : texte imprimé Auteurs : A. K. Das, Auteur ; J. R. Thome, Auteur ; P. K. Das, Auteur Année de publication : 2009 Article en page(s) : 06 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  bubbles;  bubbly  flow;  slug;  porosity Résumé : In a companion paper (“Modelling Bubbly Flow by Population Balance Technique Part I: Axial Flow Development and Its Transitions,” ASME J. Fluids Eng), a two fluid model along with a multiclass population balance technique has been used to find out comprehensive criteria for the transition from bubbly to slug flow, primarily through a study of axial flow development. Using the same basic model the transition mechanism has been investigated in the present paper covering a wide range of process parameters. Though the dominating rate of bubble coalescence during the axial development of the flow acts as the main cause for the transition to slug flow, the simultaneous transformation of the radial voidage pattern cannot be overlooked. Appearance of core, intermediate, wall, and two peaks are observed in the radial voidage distribution depending on the phase superficial velocities. A map has been developed indicating the boundaries of the above subregimes. It has been observed that not only the size of the bubbles entering the inlet plane but also the size distribution (monodispersion or bidispersion) changes the voidage peak and shifts the transition boundary. It is interesting to note that the bubbly flow only with a core peak void distribution transforms into slug flow with a change in the operating parameters. Transition boundary is also observed to shift with a change in the tube diameter. The simulation results have been compared with experimental data taken from different sources and very good agreements have been noted. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Transition of bubbly flow in vertical tubes : effect of bubble size and tube diameter [texte imprimé] / A. K. Das, Auteur ; J. R. Thome, Auteur ; P. K. Das, Auteur . - 2009 . - 06 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 9 (Septembre 2009) . - 06 p. Mots-clés : flow  (dynamics);  bubbles;  bubbly  flow;  slug;  porosity Résumé : In a companion paper (“Modelling Bubbly Flow by Population Balance Technique Part I: Axial Flow Development and Its Transitions,” ASME J. Fluids Eng), a two fluid model along with a multiclass population balance technique has been used to find out comprehensive criteria for the transition from bubbly to slug flow, primarily through a study of axial flow development. Using the same basic model the transition mechanism has been investigated in the present paper covering a wide range of process parameters. Though the dominating rate of bubble coalescence during the axial development of the flow acts as the main cause for the transition to slug flow, the simultaneous transformation of the radial voidage pattern cannot be overlooked. Appearance of core, intermediate, wall, and two peaks are observed in the radial voidage distribution depending on the phase superficial velocities. A map has been developed indicating the boundaries of the above subregimes. It has been observed that not only the size of the bubbles entering the inlet plane but also the size distribution (monodispersion or bidispersion) changes the voidage peak and shifts the transition boundary. It is interesting to note that the bubbly flow only with a core peak void distribution transforms into slug flow with a change in the operating parameters. Transition boundary is also observed to shift with a change in the tube diameter. The simulation results have been compared with experimental data taken from different sources and very good agreements have been noted. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Transition of bubbly flow in vertical tubes / A. K. Das in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 9 (Septembre 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 9 (Septembre 2009) . - 12 p. Titre : Transition of bubbly flow in vertical tubes : new criteria through CFD simulation Type de document : texte imprimé Auteurs : A. K. Das, Auteur ; J. R. Thome, Auteur ; P. K. Das, Auteur Année de publication : 2009 Article en page(s) : 12 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  bubbles;  bubbly  flow;  simulation Résumé : The two fluid model is used to simulate upward gas-liquid bubbly flow through a vertical conduit. Coalescence and breakup of bubbles have been accounted for by embedding the population balance technique in the two fluid model. The simulation enables one to track the axial development of the voidage pattern and the distribution of the bubbles. Thereby it has been possible to propose a new criterion for the transition from bubbly to slug flow regime. The transition criteria depend on (i) the breakage and coalescence frequency, (ii) the bubble volume count below and above the bubble size introduced at the inlet, and (iii) the bubble count histogram. The prediction based on the present criteria exhibits excellent agreement with the experimental data. It has also been possible to simulate the transition from bubbly to dispersed bubbly flow at a high liquid flow rate using the same model. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Transition of bubbly flow in vertical tubes : new criteria through CFD simulation [texte imprimé] / A. K. Das, Auteur ; J. R. Thome, Auteur ; P. K. Das, Auteur . - 2009 . - 12 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 9 (Septembre 2009) . - 12 p. Mots-clés : flow  (dynamics);  bubbles;  bubbly  flow;  simulation Résumé : The two fluid model is used to simulate upward gas-liquid bubbly flow through a vertical conduit. Coalescence and breakup of bubbles have been accounted for by embedding the population balance technique in the two fluid model. The simulation enables one to track the axial development of the voidage pattern and the distribution of the bubbles. Thereby it has been possible to propose a new criterion for the transition from bubbly to slug flow regime. The transition criteria depend on (i) the breakage and coalescence frequency, (ii) the bubble volume count below and above the bubble size introduced at the inlet, and (iii) the bubble count histogram. The prediction based on the present criteria exhibits excellent agreement with the experimental data. It has also been possible to simulate the transition from bubbly to dispersed bubbly flow at a high liquid flow rate using the same model. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]