Documents disponibles écrits par cet auteur

Experimental and CFD analyses of bubble parameters in a variable - thickness fluidized bed / Lyczkowski, Robert W. in Industrial & engineering chemistry research, Vol. 49 N° 11 (Juin 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5166–5173 Titre : Experimental and CFD analyses of bubble parameters in a variable - thickness fluidized bed Type de document : texte imprimé Auteurs : Lyczkowski, Robert W., Auteur ; Jacques X. Bouillard, Auteur ; Isaac K. Gamwo, Auteur Année de publication : 2010 Article en page(s) : pp. 5166–5173 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Analyse  Fluidized  Bed Résumé : Bubble characteristics in a variable-thickness fluidized bed containing nine tubes were experimentally investigated by analyzing absolute and differential pressure fluctuations. The latter were obtained from vertically aligned probes traversing the bed interior for three bed thicknesses: thin, square, and full. The important bubble parameters, namely, frequencies, effective diameters, and velocities, were determined by analyzing autocorrelations and cross-correlations obtained from these differential pressure signals for the thin and square beds. Wall effects were assessed by comparing the pressure fluctuations as the bed thickness was increased from thin to square. It was found that bubbles move faster within and above the tube bank than below it. This behavior was also found to be more pronounced in the wall regions of the full bed, which might explain why some commercial fluidized-bed combustors experience unusual metal wastage near their tube supports. Although bubble sizes consistently agreed between thin and square beds, bubble velocity reduction was observed for the thin bed. The experimental thin-bed differential pressure measurements were analyzed using a two-phase computational fluid dynamics (CFD) hydrodynamic model. Excellent agreement was obtained between the experimental results and predictions from our hydrodynamic model for autocorrelations, cross-correlations, power spectral densities, and bubble parameters. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901294e [article] Experimental and CFD analyses of bubble parameters in a variable - thickness fluidized bed [texte imprimé] / Lyczkowski, Robert W., Auteur ; Jacques X. Bouillard, Auteur ; Isaac K. Gamwo, Auteur . - 2010 . - pp. 5166–5173. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5166–5173 Mots-clés : Analyse  Fluidized  Bed Résumé : Bubble characteristics in a variable-thickness fluidized bed containing nine tubes were experimentally investigated by analyzing absolute and differential pressure fluctuations. The latter were obtained from vertically aligned probes traversing the bed interior for three bed thicknesses: thin, square, and full. The important bubble parameters, namely, frequencies, effective diameters, and velocities, were determined by analyzing autocorrelations and cross-correlations obtained from these differential pressure signals for the thin and square beds. Wall effects were assessed by comparing the pressure fluctuations as the bed thickness was increased from thin to square. It was found that bubbles move faster within and above the tube bank than below it. This behavior was also found to be more pronounced in the wall regions of the full bed, which might explain why some commercial fluidized-bed combustors experience unusual metal wastage near their tube supports. Although bubble sizes consistently agreed between thin and square beds, bubble velocity reduction was observed for the thin bed. The experimental thin-bed differential pressure measurements were analyzed using a two-phase computational fluid dynamics (CFD) hydrodynamic model. Excellent agreement was obtained between the experimental results and predictions from our hydrodynamic model for autocorrelations, cross-correlations, power spectral densities, and bubble parameters. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901294e

Mathematical modeling and numerical simulation of methane production in a hydrate reservoir / Isaac K. Gamwo in Industrial & engineering chemistry research, Vol. 49 N° 11 (Juin 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5231–5245 Titre : Mathematical modeling and numerical simulation of methane production in a hydrate reservoir Type de document : texte imprimé Auteurs : Isaac K. Gamwo, Auteur Année de publication : 2010 Article en page(s) : pp. 5231–5245 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Methane  Hydrate  Reservoir Résumé : Methane hydrate, a potential future energy resource, is known to occur naturally in vast quantities beneath the ocean floor and in permafrost regions. It is important to evaluate how much methane is recoverable from these hydrate reserves. This article introduces the theoretical background of HydrateResSim, the National Energy Technology Laboratory (NETL) methane production simulator for hydrate-containing reservoirs, originally developed for NETL by Lawrence Berkeley National Laboratory (LBNL). It describes the mathematical model that governs the dissociation of methane hydrate by depressurization or thermal stimulation of the system, including the transport of multiple temperature-dependent components in multiple phases through a porous medium. The model equations are obtained by incorporating the multiphase Darcy’s law for gas and liquid into both the mass component balances and the energy conservation equations. Two submodels in HydrateResSim for hydrate dissociation are also considered: a kinetic model and a pure thermodynamic model. Contrary to more traditional reservoir simulations, the set of model unknowns or primary variables in HydrateResSim changes throughout the simulation as a result of the formation or dissociation of ice and hydrate phases during the simulation. The primary variable switch method (PVSM) is used to effectively track these phase changes. The equations are solved by utilizing the implicit time finite-difference method on the grid system, which can properly describe phase appearance or disappearance as well as the boundary conditions. The Newton−Raphson method is used to solve the linear equations after discretization and setup of the Jacobian matrix. We report here the application of HydrateResSim to a three-component, four-phase flow system in order to predict the methane produced from a laboratory-scale reservoir. The first results of HydrateResSim code in a peer-reviewed publication are presented in this article. The numerical solution was verified against the state-of-the art simulator TOUGH+Hydrate. The model was then used to compare two dissociation theories: kinetic and pure equilibrium. Generally, the kinetic model revealed a lower dissociation rate than the equilibrium model. The hydrate dissociation patterns differed significantly when the thermal boundary condition was shifted from adiabatic to constant-temperature. The surface area factor was found to have an important effect on the rate of hydrate dissociation for the kinetic model. The deviation between the kinetic and equilibrium models was found to increase with decreasing surface area factor. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901407x [article] Mathematical modeling and numerical simulation of methane production in a hydrate reservoir [texte imprimé] / Isaac K. Gamwo, Auteur . - 2010 . - pp. 5231–5245. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5231–5245 Mots-clés : Methane  Hydrate  Reservoir Résumé : Methane hydrate, a potential future energy resource, is known to occur naturally in vast quantities beneath the ocean floor and in permafrost regions. It is important to evaluate how much methane is recoverable from these hydrate reserves. This article introduces the theoretical background of HydrateResSim, the National Energy Technology Laboratory (NETL) methane production simulator for hydrate-containing reservoirs, originally developed for NETL by Lawrence Berkeley National Laboratory (LBNL). It describes the mathematical model that governs the dissociation of methane hydrate by depressurization or thermal stimulation of the system, including the transport of multiple temperature-dependent components in multiple phases through a porous medium. The model equations are obtained by incorporating the multiphase Darcy’s law for gas and liquid into both the mass component balances and the energy conservation equations. Two submodels in HydrateResSim for hydrate dissociation are also considered: a kinetic model and a pure thermodynamic model. Contrary to more traditional reservoir simulations, the set of model unknowns or primary variables in HydrateResSim changes throughout the simulation as a result of the formation or dissociation of ice and hydrate phases during the simulation. The primary variable switch method (PVSM) is used to effectively track these phase changes. The equations are solved by utilizing the implicit time finite-difference method on the grid system, which can properly describe phase appearance or disappearance as well as the boundary conditions. The Newton−Raphson method is used to solve the linear equations after discretization and setup of the Jacobian matrix. We report here the application of HydrateResSim to a three-component, four-phase flow system in order to predict the methane produced from a laboratory-scale reservoir. The first results of HydrateResSim code in a peer-reviewed publication are presented in this article. The numerical solution was verified against the state-of-the art simulator TOUGH+Hydrate. The model was then used to compare two dissociation theories: kinetic and pure equilibrium. Generally, the kinetic model revealed a lower dissociation rate than the equilibrium model. The hydrate dissociation patterns differed significantly when the thermal boundary condition was shifted from adiabatic to constant-temperature. The surface area factor was found to have an important effect on the rate of hydrate dissociation for the kinetic model. The deviation between the kinetic and equilibrium models was found to increase with decreasing surface area factor. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901407x

Viscosity models based on the free volume and frictional theories for systems at pressures to 276 MPa and temperatures to 533 K / Ward A. Burgess in Industrial & engineering chemistry research, Vol. 51 N° 51 (Décembre 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 51 (Décembre 2012) . - pp. 16721–16733 Titre : Viscosity models based on the free volume and frictional theories for systems at pressures to 276 MPa and temperatures to 533 K Type de document : texte imprimé Auteurs : Ward A. Burgess, Auteur ; Deepak Tapriyal, Auteur ; Isaac K. Gamwo, Auteur Année de publication : 2012 Article en page(s) : pp. 16721–16733 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Viscosity  Frictional  theories Résumé : This study presents methods for accurate viscosity modeling using the frictional theory (f-theory) and the free volume theory (FV theory) of viscosity at temperatures to 533 K and pressures to 276 MPa, which are high-temperature, high-pressure (HTHP) conditions associated with ultradeep porous sandstone or carbonate layers that retain crude oil or natural gas. The perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state (EoS), the HTHP-volume-translated (VT) Peng–Robinson EoS, and the HTHP-volume-translated-Soave–Redlich–Kwong EoS (HTHP-VT-PR and HTHP-VT-SRK, respectively) are used to provide input information for both the f-theory and the FV theory. Viscosity values returned by these models are compared to available experimental data for n-alkanes with carbon numbers 1–18, branched alkanes, single and double ring aromatics, and naphthenic compounds. As currently constituted, the f-theory model underpredicts viscosity by as much as 20% at pressures near 276 MPa, but this deficiency is reduced by incorporating an empirical correction term that is a function of temperature and normal melting point. Viscosity predictions from the modified f-theory are comparable with viscosity values returned by FV theory for n-alkanes, although FV theory provides better viscosity modeling than either the f-theory or the modified f-theory for branched and aromatic hydrocarbons. FV theory viscosity values are characterized by a mean absolute percent deviation (MAPD) of 3% or less from the experimental data, with the most accurate results (MAPD 2%) obtained when the PC-SAFT is used to calculate the density input needed for the FV theory calculations. However, FV theory viscosity values actually become slightly less accurate when experimental density data are used, which indicates that FV theory itself has an inherent inaccuracy at extreme conditions unrelated to the accurate prediction of the density input. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie301727k [article] Viscosity models based on the free volume and frictional theories for systems at pressures to 276 MPa and temperatures to 533 K [texte imprimé] / Ward A. Burgess, Auteur ; Deepak Tapriyal, Auteur ; Isaac K. Gamwo, Auteur . - 2012 . - pp. 16721–16733. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 51 (Décembre 2012) . - pp. 16721–16733 Mots-clés : Viscosity  Frictional  theories Résumé : This study presents methods for accurate viscosity modeling using the frictional theory (f-theory) and the free volume theory (FV theory) of viscosity at temperatures to 533 K and pressures to 276 MPa, which are high-temperature, high-pressure (HTHP) conditions associated with ultradeep porous sandstone or carbonate layers that retain crude oil or natural gas. The perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state (EoS), the HTHP-volume-translated (VT) Peng–Robinson EoS, and the HTHP-volume-translated-Soave–Redlich–Kwong EoS (HTHP-VT-PR and HTHP-VT-SRK, respectively) are used to provide input information for both the f-theory and the FV theory. Viscosity values returned by these models are compared to available experimental data for n-alkanes with carbon numbers 1–18, branched alkanes, single and double ring aromatics, and naphthenic compounds. As currently constituted, the f-theory model underpredicts viscosity by as much as 20% at pressures near 276 MPa, but this deficiency is reduced by incorporating an empirical correction term that is a function of temperature and normal melting point. Viscosity predictions from the modified f-theory are comparable with viscosity values returned by FV theory for n-alkanes, although FV theory provides better viscosity modeling than either the f-theory or the modified f-theory for branched and aromatic hydrocarbons. FV theory viscosity values are characterized by a mean absolute percent deviation (MAPD) of 3% or less from the experimental data, with the most accurate results (MAPD 2%) obtained when the PC-SAFT is used to calculate the density input needed for the FV theory calculations. However, FV theory viscosity values actually become slightly less accurate when experimental density data are used, which indicates that FV theory itself has an inherent inaccuracy at extreme conditions unrelated to the accurate prediction of the density input. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie301727k