Documents disponibles écrits par cet auteur

Experimental and computational investigation of two phase gas — liquid flows / Ashraf Ali in Industrial & engineering chemistry research, Vol. 50 N° 23 (Décembre 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 23 (Décembre 2011) . - pp. 13220-13229 Titre : Experimental and computational investigation of two phase gas — liquid flows : point source injection at the center Type de document : texte imprimé Auteurs : Ashraf Ali, Auteur ; S. Pushpavanam, Auteur Année de publication : 2012 Article en page(s) : pp. 13220-13229 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Point  source  Two  phase  flow  Gas  liquid  flow Résumé : In this work, an experimental and numerical investigation ofhydrodynamics in a liquid induced by a bubble plume is carried out. The gas is introduced through a needle in the center of the tank containing water. The gas―liquid flow in such systems is inherently unsteady. Particle image velocimetry (PIV) was used to experimentally determine the transient velocity fields in the system. For this gas―liquid flow system, both the fluctuating and mean liquid velocities were determined experimentally by 2D and 3D PIV. The system was investigated for a liquid phase Reynolds number in the range of 3.7 × 104 to 1.8 × 105 and bubble phase Reynolds number in the range from 2350 to 11773. The behavior of the system was simulated in FLUENT 6.3.26 using a two fluid Euler―Lagrangian (EL) model with a constant bubble size of 5 mm. Here, water is treated as the continuous phase, and gas bubbles are treated as the dispersed phase. Motion of the bubbles renders the flow turbulent, and this effect is captured by the standard k―ε turbulence model. The temporal prediction of the flow field is compared with experimental results obtained from 2D and 3D measurements. The predictions from the 3D simulations capture the oscillating behavior found using 3D PIV. The 2D simulations predict a significantly higher value of turbulent viscosity. This is hypothesized as the reason as to why these simulations do not capture the oscillating behavior. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=25267477 [article] Experimental and computational investigation of two phase gas — liquid flows : point source injection at the center [texte imprimé] / Ashraf Ali, Auteur ; S. Pushpavanam, Auteur . - 2012 . - pp. 13220-13229. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 23 (Décembre 2011) . - pp. 13220-13229 Mots-clés : Point  source  Two  phase  flow  Gas  liquid  flow Résumé : In this work, an experimental and numerical investigation ofhydrodynamics in a liquid induced by a bubble plume is carried out. The gas is introduced through a needle in the center of the tank containing water. The gas―liquid flow in such systems is inherently unsteady. Particle image velocimetry (PIV) was used to experimentally determine the transient velocity fields in the system. For this gas―liquid flow system, both the fluctuating and mean liquid velocities were determined experimentally by 2D and 3D PIV. The system was investigated for a liquid phase Reynolds number in the range of 3.7 × 104 to 1.8 × 105 and bubble phase Reynolds number in the range from 2350 to 11773. The behavior of the system was simulated in FLUENT 6.3.26 using a two fluid Euler―Lagrangian (EL) model with a constant bubble size of 5 mm. Here, water is treated as the continuous phase, and gas bubbles are treated as the dispersed phase. Motion of the bubbles renders the flow turbulent, and this effect is captured by the standard k―ε turbulence model. The temporal prediction of the flow field is compared with experimental results obtained from 2D and 3D measurements. The predictions from the 3D simulations capture the oscillating behavior found using 3D PIV. The 2D simulations predict a significantly higher value of turbulent viscosity. This is hypothesized as the reason as to why these simulations do not capture the oscillating behavior. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=25267477

Experimental and numerical investigations of two-phase (Liquid−Liquid) flow behavior in rectangular microchannels / Reddy Cherlo, Siva Kumar in Industrial & engineering chemistry research, Vol. 49 N° 2 (Janvier 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 2 (Janvier 2010) . - pp 893–899 Titre : Experimental and numerical investigations of two-phase (Liquid−Liquid) flow behavior in rectangular microchannels Type de document : texte imprimé Auteurs : Reddy Cherlo, Siva Kumar, Auteur ; Kariveti, Sreenath, Auteur ; S. Pushpavanam, Auteur Année de publication : 2010 Article en page(s) : pp 893–899 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : kinetics  Mass-transfer  Multiphase  microreactors  Two  phase  liquid  Rectangular  microchannels. Résumé : The interaction between kinetics and mass-transfer effects is determined by the flow regime in liquid−liquid multiphase microreactors. The operating conditions under which the various flow regimes such as slug flow and stratified flow occur in liquid−liquid systems has not been extensively studied and is not well-understood. The effect of operating conditions on slug length for instance is not well-known. The present study focuses on microreactors fabricated in Perspex (poly(methyl methaacrylate) (PMMA)), which are essentially microchannels with a rectangular cross-section. Experiments are carried out for a wide range of flow rates, channel sizes, and fluid systems with varying properties. Two different kinds of flow regimes, slug flow and stratified flow, are experimentally observed, and these are predicted using numerical simulations. We divide the space of operating conditions (the two liquid flow rates) into different regions such that in each region the flow regime is distinct. The dependence of slug length on flow rates and other parameters such as channel size, viscosity, surface tension, and contact angle have been determined and are quantitatively compared with predictions of simulations. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900555e [article] Experimental and numerical investigations of two-phase (Liquid−Liquid) flow behavior in rectangular microchannels [texte imprimé] / Reddy Cherlo, Siva Kumar, Auteur ; Kariveti, Sreenath, Auteur ; S. Pushpavanam, Auteur . - 2010 . - pp 893–899. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 2 (Janvier 2010) . - pp 893–899 Mots-clés : kinetics  Mass-transfer  Multiphase  microreactors  Two  phase  liquid  Rectangular  microchannels. Résumé : The interaction between kinetics and mass-transfer effects is determined by the flow regime in liquid−liquid multiphase microreactors. The operating conditions under which the various flow regimes such as slug flow and stratified flow occur in liquid−liquid systems has not been extensively studied and is not well-understood. The effect of operating conditions on slug length for instance is not well-known. The present study focuses on microreactors fabricated in Perspex (poly(methyl methaacrylate) (PMMA)), which are essentially microchannels with a rectangular cross-section. Experiments are carried out for a wide range of flow rates, channel sizes, and fluid systems with varying properties. Two different kinds of flow regimes, slug flow and stratified flow, are experimentally observed, and these are predicted using numerical simulations. We divide the space of operating conditions (the two liquid flow rates) into different regions such that in each region the flow regime is distinct. The dependence of slug length on flow rates and other parameters such as channel size, viscosity, surface tension, and contact angle have been determined and are quantitatively compared with predictions of simulations. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900555e

Screening, selecting, and designing microreactors / Reddy Cherlo, Siva Kumar in Industrial & engineering chemistry research, Vol. 48 N° 18 (Septembre 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 18 (Septembre 2009) . - pp. 8678–8684 Titre : Screening, selecting, and designing microreactors Type de document : texte imprimé Auteurs : Reddy Cherlo, Siva Kumar, Auteur ; Sreenath, K., Auteur ; S. Pushpavanam, Auteur Année de publication : 2010 Article en page(s) : pp. 8678–8684 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Microreactors  Computational  fluid  dynamics  approach  Flow  regimes Résumé : Microreactors can be used to carry out hazardous organic reactions like nitration of benzene and toluene safely. A theoretical analysis of the performance of these systems is usually based on using a computational fluid dynamics approach incorporating the effect of reactions. These simulations help us identify different flow regimes of the system as stratified flow, vortex flow, and engulfment flow. Though it provides realistic estimates of the performance this is a computationally intensive approach. In this work we discuss two strategies for modeling, which exploits the inherent features of single phase flows in microchannels. The first is based on a one-dimensional model where lateral mixing is incorporated using a “pseudo” mass transfer coefficient. In the second we use an effective dispersion coefficient to represent lateral mixing in microchannels. In both approaches we assume the fluid flows as a plug, that is, with a uniform velocity across the cross-section. We consider two different sets of reactions, (i) a set of parallel reactions and (ii) a set of series parallel reactions, and determine how the flow regime in the channel can be exploited to carry out reactions and simultaneously separate the products. The 1D results are compared with those of the 2D model where the transport in the lateral direction is modeled using a dispersion coefficient. The results of the two simplified models are compared with rigorous two-dimensional simulations using Fluent. The approach proposed here can be used to screen and analyze the performance of different reactions in microchannels and examine if the flow features can be used to carry out reactions and separate the products simultaneously. The promising candidates can then be analyzed rigorously for a realistic evaluation of the performance incorporating the prevailing flow structures using computational fluid dynamics. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900306j [article] Screening, selecting, and designing microreactors [texte imprimé] / Reddy Cherlo, Siva Kumar, Auteur ; Sreenath, K., Auteur ; S. Pushpavanam, Auteur . - 2010 . - pp. 8678–8684. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 18 (Septembre 2009) . - pp. 8678–8684 Mots-clés : Microreactors  Computational  fluid  dynamics  approach  Flow  regimes Résumé : Microreactors can be used to carry out hazardous organic reactions like nitration of benzene and toluene safely. A theoretical analysis of the performance of these systems is usually based on using a computational fluid dynamics approach incorporating the effect of reactions. These simulations help us identify different flow regimes of the system as stratified flow, vortex flow, and engulfment flow. Though it provides realistic estimates of the performance this is a computationally intensive approach. In this work we discuss two strategies for modeling, which exploits the inherent features of single phase flows in microchannels. The first is based on a one-dimensional model where lateral mixing is incorporated using a “pseudo” mass transfer coefficient. In the second we use an effective dispersion coefficient to represent lateral mixing in microchannels. In both approaches we assume the fluid flows as a plug, that is, with a uniform velocity across the cross-section. We consider two different sets of reactions, (i) a set of parallel reactions and (ii) a set of series parallel reactions, and determine how the flow regime in the channel can be exploited to carry out reactions and simultaneously separate the products. The 1D results are compared with those of the 2D model where the transport in the lateral direction is modeled using a dispersion coefficient. The results of the two simplified models are compared with rigorous two-dimensional simulations using Fluent. The approach proposed here can be used to screen and analyze the performance of different reactions in microchannels and examine if the flow features can be used to carry out reactions and separate the products simultaneously. The promising candidates can then be analyzed rigorously for a realistic evaluation of the performance incorporating the prevailing flow structures using computational fluid dynamics. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900306j