Canadian Journal of Chemical Engineering, Aug 1, 1993
Heat transfer in dense fluidized beds have been extensively studied. However, there is not much d... more Heat transfer in dense fluidized beds have been extensively studied. However, there is not much detailed information about the mechanism of surface-to-suspension heat transfer in the freeboard region. In the present work, a newly designed heating plate was used to measure the plate-surface-to-particle-suspension heat transfer coefficients in the freeboard. The experimental unit consisted of a 30 cm i.d. fluidized bed reactor packed with fluidized catalytic particles of mean particle size 90 pm. Three types of plate orientations were used to test directional effects of surface on heat transfer rate. Height of the freeboard was 171 cm, and the superficial gas velocity was varied from 0.28 to 0.64 m/s. Local solids concentrations in the freeboard were also obtained by a nozzle-type sampling probe. Data on axial distribution of solids concentration were used to find out the solids kinematics in the freeboard region. Finally, a surface-to-suspension heat transfer model was developed to elucidate the surface to particle heat transfer mechanism in this lean phase system. The model is based on the transient gas-convective heating of single particles when sliding over the heating plate and the assumption of instantaneous attachment-detachment equilibrium between particles and the plate surface. On a mene une Ctude approfondie sur le transfert de chaleur en lits fluidisCs denses. Peu de donnkes sont toutefois disponibles concernant le mCcanisme du transfert de chaleur de la surface vers la suspension dans la zone libre. Dans le present travail, un plateau de chauffage de conception nouvelle est utilist pour mesurer les coefficients de transfer de chaleur de la surface des plateaux vers la suspension des particules dans la zone libre. Le dispositif expkrimental comprend un rCacteur lit fluidis6 de 30 cm de diamktre intkrieur garni de particules catalytiques fluidisCes d'une taille moyenne de 90 pm. Trois types d'orientation des plateaux ont Ct C utilisCs pour tester les effets directionnels de la surface sur le taux de transfert de chaleur. La hauteur de la zone libre est de 171 cm et on a fait varier la vitesse de gaz superficielle de 0,28 B 0,64 m/s. Les concentrations locales des solides dans la zone libre ont Cgalement Ct C obtenues au moyen d'une sonde d'kchantillonnage h tuykre. On a utilisC la distribution axiale de la concentration des solides afin de trouver la cinkmatique des solides dans la zone libre. Enfin, un modtle de transfert de chaleur de la surface vers la suspension a CtC mis au point pour expliquer le mCcanisme de transfert de chaleur de la surface vers les particules dans ce systkme a phases pauvres. Ce modtle s'appuie sur deux CICments: le chauffage convectif transitoire de particules uniques lorsque celles-ci glissent au-dessus du plateau de chauffage et l'hypothkse d'un Cquilibre instan-tan6 de type attachement-dktachement entre les particules et la surface des plateaux.
Knowledge of the temperature profile of the gases produced by the combustion of fossil fuels with... more Knowledge of the temperature profile of the gases produced by the combustion of fossil fuels with air is a desirable step in the thermal protection systems. These gases are generally associated with high temperatures and steep temperature gradients. The measurement of temperature profiles of combustion products are often hard to make using thermocouples and other immersed pyrometers because such probes may have to be immersed in inaccessible and possibly destructive media. Determination of gas temperature profiles from multi-frequency radiative measurements seems an attractive alternative. This could be accomplished by radiative heat transfer probing and the application of the principle of inversion, where inversion is the process of inferring the internal parameters of a system of outside measurements, without the interruption of the combustion system itself.This paper discusses the development of models to retrieve the temperature distribution in a flame system by remote spectral sensing. Mixed Gray-Gas models were developed to calculate water vapor and carbon dioxide standard emissivities. The evaluation of combustion system spectral radiant flux was simulated and a model was developed and successfully tested for the application of temperature inversion.
Since its introduction in 1942 the fluid catalytic cracking (FCC) has been the most important and... more Since its introduction in 1942 the fluid catalytic cracking (FCC) has been the most important and widely used process for the production of gasoline from heavy distillates. In most refineries the capacity of the FCC unit is second only to that of the crude distillation unit. Often an FCC unit is referred to as the heart of a modern refinery oriented toward maximum production of gasoline. The basic step in the FCC process is the recirculation of the catalyst through the reactor, stripping and regenerator. In the reactor system the hydrocarbon feed is heated and cracked. Coke (or carbon) may be produced and may deposit on the catalyst reducing its activity and selectivity. When the catalyst is circulated to the regenerator carbon is burned off causing the heating of the catalyst before its return to the reactor part. The products from the reactor are separated in a main fractionator into gas and liquid streams normally including a recycle feed to the reactor. The operation of an FCC unit requires the manipulation of a large number of controlled variables affecting its performance. Major process variables such as reactor temperature, catalyst circulation rate, catalyst inventory and recycle feed rate can be varied to influence the product yields and to accommodate widely different feedstocks. Unpredictable variation can occur in feed stock, catalyst quality and equipment performance. Most normal variation can be accommodated by a small change in operating conditions. For a new plant, comparison of actual versus predicted performance provides a valuable check on the validity of the design correlations and a guide for future laboratory and engineering research. The objectives of the present work are to simplify the complicated FCC process variables and to develop a computer model to simulate the operation of an FCC at different conditions. This includes the prediction of the effects of the operating variables on the reactor product yields. These products include fuel gas, C3, C4 gasoline, light gas oil and coke. The model provides a good base for troubleshooting and debottlenecking and may be useful in optimal control of the FCC.
The main sources of non-luminous gas radiation in furnaces are carbon dioxide and water vapor. Ap... more The main sources of non-luminous gas radiation in furnaces are carbon dioxide and water vapor. Approximation of the standard emissivities of water vapor and of carbon dioxide by mixed gray-gas model is studied. The model developed for carbon dioxide standard emi s si vi ti es covers a range of temperature of 3DO-1BOOK and a partial-pressure-length product range of 0.01 to 10 m atm. A mixture of six gray gases was adequate to cover the whole range. For the water vapor thermal radiation two models were developed to approximate the standard water ~apor emissi~ities. In the first model water ~apor is approximated by a mixture of four gray-gases and can be used in the temperature range of 300-700K and the partial-pressure-length range of 0.01 to 2 m atm. The second model is a piece-wise one in which one gray gas is used to cover the pL range 0.5-2 m and a second gray gas covered the range of 0.05-0.5 m. The model may be used in the temperature range of 700-l500K and has an error range of -2.3 to 3.7~.
... and TAREK A. ALLAM Deparrmenr of Chemical Engineering University of New Hampshire Durham, New... more ... and TAREK A. ALLAM Deparrmenr of Chemical Engineering University of New Hampshire Durham, New Hampshire 03824-3591 ... The knowledge of the emissivities of carbon dioxide and water vapor is very important in burner design and thermal efficiency calculations. ...
Canadian Journal of Chemical Engineering, Aug 1, 1992
Local surface-to-suspension heat transfer coefficients in the freeboard of a fluidized bed reacto... more Local surface-to-suspension heat transfer coefficients in the freeboard of a fluidized bed reactor were measured by a newly designed miniature probe. Four types of plate orientations were used to test directional effects of surkce on heat transfer rate. Variations of heat transfer coefficients with radial position are more significant at !ower freeboard. For plate parallel both to the axial and radial directions of the column, the heat transfer coefficient (h) is higher at the center than at wall. For plate with exposed surface parallel to the axial and perpendicular to the radial directions, the plate gives nearly the same value of h at the center and the wall. At low heights of freeboard, center-facing surface exhibits higher heat transfer rate than wall-facing one. The phenomena of higher solids concentration and center to wall niovenient of particles account for this observation. Variations of heat transfer coefficients with elevation in the freeboard are as much as an order of magnitude, decreasing to gas convection with increasing elevation. These variations are relatively insensitive to the types of plate orientation investigated. On a mesurC les coefficients de transfert de chaleur locaux entre la surface et la suspension dans la zone libre d'un reacteur B lit fluidist au moyen d'une sonde miniature de conception nouvelle. On a utilist quatre types d'orientation des plateaux pour tester les effets directionnels de surface sur la vitesse du transfert de chaleur. Les variations des coefficients de transfert de chaleur selon la position radiale sont plus importantes dans la zone libre infirieure. Lorsque le plateau est parallkle a la fois aux directions axiales et radiales de la colonne, le coefficient de transfert de chaleur (h) est plus grand au centre qu'B la paroi. Lorsque la surface exposCe du plateau est parallkle B la direction axiale et perpendiculaire B la direction radiale, on obtient quasiment la m&me valeur de h au centre et a la paroi. Pour de faibles hauteurs de la zone libre, la surface faisant face au centre rnontre une vitesse de transfert de chaleur plus grande que la surface se trouvant face 1 la paroi. Le phtnomkne des plus fortes concentrations de solides et du mouvement des particules entre le centre et la paroi explique cette observation. La variation des coefficients de transfert de chaleur avec I'CICvation de la zone libre est au moins d'un ordre de grandeur, diminuant avec la convection du gaz lorsque la hauteur augmente. Ces variations sont relativement insensibles aux types d'orientation des plateaux Ctudits.
Bioprocess and Biosystems Engineering, Nov 22, 2000
In the present study the oxygen mass transfer from the gas to the aqueous phase in a Three-Phase ... more In the present study the oxygen mass transfer from the gas to the aqueous phase in a Three-Phase Inverse Fluidized Bed (TPIFB) has been studied. A pilot scale TPIFB has been designed and constructed. For determination of the volumetric oxygen mass transfer coefficient the elegant dynamic method, described by Dang et al. (1977) was used. The influence of hydrodynamic parameters,
This publication contains 12 papers of which 2 appear as abstracts only. The volume is based upon... more This publication contains 12 papers of which 2 appear as abstracts only. The volume is based upon papers presented at the 89th National AIChE Meeting, August 17-20, 1980, in Portland, Oregon and the 73rd AIChE Annual Meeting, held November 16-20 1980, in Chicago, Illionois, in two solar energy sessions. Topics covered include: thermal storage; solar cells; solar generation; biomass utilization; and solar energy applications. All papers are abstracted separately.
Published spectral data on the emission/absorption characteristics of water vapor and carbon diox... more Published spectral data on the emission/absorption characteristics of water vapor and carbon dioxide gases, which are generally in the form of the absorption coefficient and the mean line spacing averaged over same spectral interval have been compiled and studied. Different gas band models were studied and the gas statistical model have been adopted as the present model for emissivity and absorptivity calculation. Total emissivity and absorptivity data of carbon dioxide, water vapor and their mixture by various investigators have been complied, corrected to a common partial pressure of zero and total pressure of one atmsophere and critically reviewed. Spectral data of carbon dioxide were modified to include the 10 and 2 micron bands, which are of importance at high temperatures. Computed emissivities of carbon dioxide were compared to experimental data to construct the recommended emissivity charts for carbon dioxide at Pc = 0, Pt = 1 atm. Comparison of corrected experimental water vapor emissivities with computed using the Ludwig et. al. (1973) spectral tabulations necessitated the modification of the rotation band absorptive coefficient to include the more recent tabulations of McClatchey et. al. (1972) at 300 and 600 K. Computed emissivities are compared to experimental and rules for constructing the recommended emissivity charts for water vapor at pw = 0, Pt = 1 atm. are presented and implemented. Pressure broadening correction factor charts are presented both in a set of general plots and a set of Engineering plots. Overlap correction charts due to superimposed spectral radiation bands are presented in two different sets of plots at pc = Pw = 0 and Pt = 1 atm. Pressure boradening correction of the overlap correction is discussed and a "Grey gas" approximation proposed in the work is discussed.
An algorithm has been developed and tested for steady-state liquid-liquid extraction, using recta... more An algorithm has been developed and tested for steady-state liquid-liquid extraction, using rectangular coordinates. It is capable of handling common types of stagewise contact, i.e. single stage extraction, multistage cross-current, and continuous countercurrent multistage extraction. The results depend on the nature of the extraction scheme and the extent of separation desired. While equilibrium data for some systems are stored in its data bank, the present portable computer simulator (LIQEXT) has the flexibility of reading equilibrium data for other systems, as well as overriding stored data.
This publication contains 12 papers of which 2 appear as abstracts only. The volume is based upon... more This publication contains 12 papers of which 2 appear as abstracts only. The volume is based upon papers presented at the 89th National AIChE Meeting, August 17-20, 1980, in Portland, Oregon and the 73rd AIChE Annual Meeting, held November 16-20 1980, in Chicago, Illionois, in two solar energy sessions. Topics covered include: thermal storage; solar cells; solar generation; biomass utilization; and solar energy applications. All papers are abstracted separately.
Volume 3: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations, Jun 8, 1986
Data was obtained from the combustion of coal derived fuels in a 30 inch diameter, 4 foot long be... more Data was obtained from the combustion of coal derived fuels in a 30 inch diameter, 4 foot long bench scale atmospheric unit fueled with CWF. The data is presented and compared with model predictions of ash, temperature, and mole fraction distributions. A computer model was developed to simulate the heat transfer processes taking place in a gas turbine combustor (GTC) burning a coal water fuel (CWF). It is to predict the species and temperature distribution, the heat flux patterns, and the contribution of both convection and radiation to the total heat transfer rate. This model was verified in part 1 of this paper. 1.
International Communications in Heat and Mass Transfer, 1989
It is possible to disperse high concentrations of finely pulverized beneficiated coal in water to... more It is possible to disperse high concentrations of finely pulverized beneficiated coal in water to produce a stable coal-water slurry fuel (CWF). One of the potential applications of CWF is as a fuel in gas turbines. This represents a relatively novel, developing technology. The gas ...
The major mode of heat transfer in industrial combustion furnaces is that of radiation. The effec... more The major mode of heat transfer in industrial combustion furnaces is that of radiation. The effects of radiative scattering are therefore of great importance in furnace design. This study investigates the behavior of both anisotropic and isotropic scattering using a computer-simulated model of a typical combustion furnaceThe furnace model employed is based on the zoning method of Hottel and the Monte-Carlo statistical approach. To study scattering effects, subroutines to simulate isotropic and anisotropic scattering have been added on to the model developed in earlier work with non-scattering mediums. Anisotropic scattering distributions studied include both forward and backward skewed profilesTo simplify the three-dimensional model, a three by four meter slab of a semi-infinite furnace is studied. Each stab is rectangular in shape, containing twelve cubical zones and incorporating a single burner. Model results are presented in the form of temperature contours and total surface heat fluxes for different scattering albedoes and profiles.
The development of a microcomputer based finite element program featuring phase change (melting a... more The development of a microcomputer based finite element program featuring phase change (melting and freezing) simulation and facilities is outlined. A closed form Galerkin finite element method derived from a delta function formulation of the latent heat discontinuity in the heat capacity versus temperature function is used within phase change elements of the solution domain. Storage reduction data structures are implemented and compared on the basis of overall program execution time. Analytical solutions for melting and freezing are used to vertify program accuracy and to explore other simulation parameters such as time step size, mesh density and start-up technique. Several ''life like'' phase change simulations are compared to the results obtained from other numerical models.
Volume 3: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations, Jun 8, 1986
Eg Blackbody emissive power of gas, W/m 2. It is possible to disperse high concentrations of E s ... more Eg Blackbody emissive power of gas, W/m 2. It is possible to disperse high concentrations of E s Blackbody emissive power of surface, W/m 2. finely pulverized beneficiated coal in water to produce a stable coal-water slurry fuel (CWF). One of f a Fraction of ash in coal, dimensionless. the potential applications of CWF is as a fuel in gas turbines. This represents a relatively novel, developgg Direct gas-gas exchange area, m 2 c
An investigation was undertaken to study the mixing of two miscible phases in coils by secondary ... more An investigation was undertaken to study the mixing of two miscible phases in coils by secondary flow and natural convection. In the absence of natural convection the Dean number was found to be a unique dynamic similarity parameter governing fluid flow and mixing in helical coils, even when the viscosities of the phases are very different. For fluids of differing densities natural convection increased the enhancements by as much as 58%. Mixing enhancement in segmented (i.e., gas partitioned) flow was typically three to four times larger than in nonsegmented flow. Various coil configurations were evaluated for enhancing the mixing. The change of coil curvature with coil length and the initial position of the interface relative to the direction of secondary flow were established as vital parameters affecting mixing.
Canadian Journal of Chemical Engineering, Aug 1, 1993
Heat transfer in dense fluidized beds have been extensively studied. However, there is not much d... more Heat transfer in dense fluidized beds have been extensively studied. However, there is not much detailed information about the mechanism of surface-to-suspension heat transfer in the freeboard region. In the present work, a newly designed heating plate was used to measure the plate-surface-to-particle-suspension heat transfer coefficients in the freeboard. The experimental unit consisted of a 30 cm i.d. fluidized bed reactor packed with fluidized catalytic particles of mean particle size 90 pm. Three types of plate orientations were used to test directional effects of surface on heat transfer rate. Height of the freeboard was 171 cm, and the superficial gas velocity was varied from 0.28 to 0.64 m/s. Local solids concentrations in the freeboard were also obtained by a nozzle-type sampling probe. Data on axial distribution of solids concentration were used to find out the solids kinematics in the freeboard region. Finally, a surface-to-suspension heat transfer model was developed to elucidate the surface to particle heat transfer mechanism in this lean phase system. The model is based on the transient gas-convective heating of single particles when sliding over the heating plate and the assumption of instantaneous attachment-detachment equilibrium between particles and the plate surface. On a mene une Ctude approfondie sur le transfert de chaleur en lits fluidisCs denses. Peu de donnkes sont toutefois disponibles concernant le mCcanisme du transfert de chaleur de la surface vers la suspension dans la zone libre. Dans le present travail, un plateau de chauffage de conception nouvelle est utilist pour mesurer les coefficients de transfer de chaleur de la surface des plateaux vers la suspension des particules dans la zone libre. Le dispositif expkrimental comprend un rCacteur lit fluidis6 de 30 cm de diamktre intkrieur garni de particules catalytiques fluidisCes d'une taille moyenne de 90 pm. Trois types d'orientation des plateaux ont Ct C utilisCs pour tester les effets directionnels de la surface sur le taux de transfert de chaleur. La hauteur de la zone libre est de 171 cm et on a fait varier la vitesse de gaz superficielle de 0,28 B 0,64 m/s. Les concentrations locales des solides dans la zone libre ont Cgalement Ct C obtenues au moyen d'une sonde d'kchantillonnage h tuykre. On a utilisC la distribution axiale de la concentration des solides afin de trouver la cinkmatique des solides dans la zone libre. Enfin, un modtle de transfert de chaleur de la surface vers la suspension a CtC mis au point pour expliquer le mCcanisme de transfert de chaleur de la surface vers les particules dans ce systkme a phases pauvres. Ce modtle s'appuie sur deux CICments: le chauffage convectif transitoire de particules uniques lorsque celles-ci glissent au-dessus du plateau de chauffage et l'hypothkse d'un Cquilibre instan-tan6 de type attachement-dktachement entre les particules et la surface des plateaux.
Knowledge of the temperature profile of the gases produced by the combustion of fossil fuels with... more Knowledge of the temperature profile of the gases produced by the combustion of fossil fuels with air is a desirable step in the thermal protection systems. These gases are generally associated with high temperatures and steep temperature gradients. The measurement of temperature profiles of combustion products are often hard to make using thermocouples and other immersed pyrometers because such probes may have to be immersed in inaccessible and possibly destructive media. Determination of gas temperature profiles from multi-frequency radiative measurements seems an attractive alternative. This could be accomplished by radiative heat transfer probing and the application of the principle of inversion, where inversion is the process of inferring the internal parameters of a system of outside measurements, without the interruption of the combustion system itself.This paper discusses the development of models to retrieve the temperature distribution in a flame system by remote spectral sensing. Mixed Gray-Gas models were developed to calculate water vapor and carbon dioxide standard emissivities. The evaluation of combustion system spectral radiant flux was simulated and a model was developed and successfully tested for the application of temperature inversion.
Since its introduction in 1942 the fluid catalytic cracking (FCC) has been the most important and... more Since its introduction in 1942 the fluid catalytic cracking (FCC) has been the most important and widely used process for the production of gasoline from heavy distillates. In most refineries the capacity of the FCC unit is second only to that of the crude distillation unit. Often an FCC unit is referred to as the heart of a modern refinery oriented toward maximum production of gasoline. The basic step in the FCC process is the recirculation of the catalyst through the reactor, stripping and regenerator. In the reactor system the hydrocarbon feed is heated and cracked. Coke (or carbon) may be produced and may deposit on the catalyst reducing its activity and selectivity. When the catalyst is circulated to the regenerator carbon is burned off causing the heating of the catalyst before its return to the reactor part. The products from the reactor are separated in a main fractionator into gas and liquid streams normally including a recycle feed to the reactor. The operation of an FCC unit requires the manipulation of a large number of controlled variables affecting its performance. Major process variables such as reactor temperature, catalyst circulation rate, catalyst inventory and recycle feed rate can be varied to influence the product yields and to accommodate widely different feedstocks. Unpredictable variation can occur in feed stock, catalyst quality and equipment performance. Most normal variation can be accommodated by a small change in operating conditions. For a new plant, comparison of actual versus predicted performance provides a valuable check on the validity of the design correlations and a guide for future laboratory and engineering research. The objectives of the present work are to simplify the complicated FCC process variables and to develop a computer model to simulate the operation of an FCC at different conditions. This includes the prediction of the effects of the operating variables on the reactor product yields. These products include fuel gas, C3, C4 gasoline, light gas oil and coke. The model provides a good base for troubleshooting and debottlenecking and may be useful in optimal control of the FCC.
The main sources of non-luminous gas radiation in furnaces are carbon dioxide and water vapor. Ap... more The main sources of non-luminous gas radiation in furnaces are carbon dioxide and water vapor. Approximation of the standard emissivities of water vapor and of carbon dioxide by mixed gray-gas model is studied. The model developed for carbon dioxide standard emi s si vi ti es covers a range of temperature of 3DO-1BOOK and a partial-pressure-length product range of 0.01 to 10 m atm. A mixture of six gray gases was adequate to cover the whole range. For the water vapor thermal radiation two models were developed to approximate the standard water ~apor emissi~ities. In the first model water ~apor is approximated by a mixture of four gray-gases and can be used in the temperature range of 300-700K and the partial-pressure-length range of 0.01 to 2 m atm. The second model is a piece-wise one in which one gray gas is used to cover the pL range 0.5-2 m and a second gray gas covered the range of 0.05-0.5 m. The model may be used in the temperature range of 700-l500K and has an error range of -2.3 to 3.7~.
... and TAREK A. ALLAM Deparrmenr of Chemical Engineering University of New Hampshire Durham, New... more ... and TAREK A. ALLAM Deparrmenr of Chemical Engineering University of New Hampshire Durham, New Hampshire 03824-3591 ... The knowledge of the emissivities of carbon dioxide and water vapor is very important in burner design and thermal efficiency calculations. ...
Canadian Journal of Chemical Engineering, Aug 1, 1992
Local surface-to-suspension heat transfer coefficients in the freeboard of a fluidized bed reacto... more Local surface-to-suspension heat transfer coefficients in the freeboard of a fluidized bed reactor were measured by a newly designed miniature probe. Four types of plate orientations were used to test directional effects of surkce on heat transfer rate. Variations of heat transfer coefficients with radial position are more significant at !ower freeboard. For plate parallel both to the axial and radial directions of the column, the heat transfer coefficient (h) is higher at the center than at wall. For plate with exposed surface parallel to the axial and perpendicular to the radial directions, the plate gives nearly the same value of h at the center and the wall. At low heights of freeboard, center-facing surface exhibits higher heat transfer rate than wall-facing one. The phenomena of higher solids concentration and center to wall niovenient of particles account for this observation. Variations of heat transfer coefficients with elevation in the freeboard are as much as an order of magnitude, decreasing to gas convection with increasing elevation. These variations are relatively insensitive to the types of plate orientation investigated. On a mesurC les coefficients de transfert de chaleur locaux entre la surface et la suspension dans la zone libre d'un reacteur B lit fluidist au moyen d'une sonde miniature de conception nouvelle. On a utilist quatre types d'orientation des plateaux pour tester les effets directionnels de surface sur la vitesse du transfert de chaleur. Les variations des coefficients de transfert de chaleur selon la position radiale sont plus importantes dans la zone libre infirieure. Lorsque le plateau est parallkle a la fois aux directions axiales et radiales de la colonne, le coefficient de transfert de chaleur (h) est plus grand au centre qu'B la paroi. Lorsque la surface exposCe du plateau est parallkle B la direction axiale et perpendiculaire B la direction radiale, on obtient quasiment la m&me valeur de h au centre et a la paroi. Pour de faibles hauteurs de la zone libre, la surface faisant face au centre rnontre une vitesse de transfert de chaleur plus grande que la surface se trouvant face 1 la paroi. Le phtnomkne des plus fortes concentrations de solides et du mouvement des particules entre le centre et la paroi explique cette observation. La variation des coefficients de transfert de chaleur avec I'CICvation de la zone libre est au moins d'un ordre de grandeur, diminuant avec la convection du gaz lorsque la hauteur augmente. Ces variations sont relativement insensibles aux types d'orientation des plateaux Ctudits.
Bioprocess and Biosystems Engineering, Nov 22, 2000
In the present study the oxygen mass transfer from the gas to the aqueous phase in a Three-Phase ... more In the present study the oxygen mass transfer from the gas to the aqueous phase in a Three-Phase Inverse Fluidized Bed (TPIFB) has been studied. A pilot scale TPIFB has been designed and constructed. For determination of the volumetric oxygen mass transfer coefficient the elegant dynamic method, described by Dang et al. (1977) was used. The influence of hydrodynamic parameters,
This publication contains 12 papers of which 2 appear as abstracts only. The volume is based upon... more This publication contains 12 papers of which 2 appear as abstracts only. The volume is based upon papers presented at the 89th National AIChE Meeting, August 17-20, 1980, in Portland, Oregon and the 73rd AIChE Annual Meeting, held November 16-20 1980, in Chicago, Illionois, in two solar energy sessions. Topics covered include: thermal storage; solar cells; solar generation; biomass utilization; and solar energy applications. All papers are abstracted separately.
Published spectral data on the emission/absorption characteristics of water vapor and carbon diox... more Published spectral data on the emission/absorption characteristics of water vapor and carbon dioxide gases, which are generally in the form of the absorption coefficient and the mean line spacing averaged over same spectral interval have been compiled and studied. Different gas band models were studied and the gas statistical model have been adopted as the present model for emissivity and absorptivity calculation. Total emissivity and absorptivity data of carbon dioxide, water vapor and their mixture by various investigators have been complied, corrected to a common partial pressure of zero and total pressure of one atmsophere and critically reviewed. Spectral data of carbon dioxide were modified to include the 10 and 2 micron bands, which are of importance at high temperatures. Computed emissivities of carbon dioxide were compared to experimental data to construct the recommended emissivity charts for carbon dioxide at Pc = 0, Pt = 1 atm. Comparison of corrected experimental water vapor emissivities with computed using the Ludwig et. al. (1973) spectral tabulations necessitated the modification of the rotation band absorptive coefficient to include the more recent tabulations of McClatchey et. al. (1972) at 300 and 600 K. Computed emissivities are compared to experimental and rules for constructing the recommended emissivity charts for water vapor at pw = 0, Pt = 1 atm. are presented and implemented. Pressure broadening correction factor charts are presented both in a set of general plots and a set of Engineering plots. Overlap correction charts due to superimposed spectral radiation bands are presented in two different sets of plots at pc = Pw = 0 and Pt = 1 atm. Pressure boradening correction of the overlap correction is discussed and a "Grey gas" approximation proposed in the work is discussed.
An algorithm has been developed and tested for steady-state liquid-liquid extraction, using recta... more An algorithm has been developed and tested for steady-state liquid-liquid extraction, using rectangular coordinates. It is capable of handling common types of stagewise contact, i.e. single stage extraction, multistage cross-current, and continuous countercurrent multistage extraction. The results depend on the nature of the extraction scheme and the extent of separation desired. While equilibrium data for some systems are stored in its data bank, the present portable computer simulator (LIQEXT) has the flexibility of reading equilibrium data for other systems, as well as overriding stored data.
This publication contains 12 papers of which 2 appear as abstracts only. The volume is based upon... more This publication contains 12 papers of which 2 appear as abstracts only. The volume is based upon papers presented at the 89th National AIChE Meeting, August 17-20, 1980, in Portland, Oregon and the 73rd AIChE Annual Meeting, held November 16-20 1980, in Chicago, Illionois, in two solar energy sessions. Topics covered include: thermal storage; solar cells; solar generation; biomass utilization; and solar energy applications. All papers are abstracted separately.
Volume 3: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations, Jun 8, 1986
Data was obtained from the combustion of coal derived fuels in a 30 inch diameter, 4 foot long be... more Data was obtained from the combustion of coal derived fuels in a 30 inch diameter, 4 foot long bench scale atmospheric unit fueled with CWF. The data is presented and compared with model predictions of ash, temperature, and mole fraction distributions. A computer model was developed to simulate the heat transfer processes taking place in a gas turbine combustor (GTC) burning a coal water fuel (CWF). It is to predict the species and temperature distribution, the heat flux patterns, and the contribution of both convection and radiation to the total heat transfer rate. This model was verified in part 1 of this paper. 1.
International Communications in Heat and Mass Transfer, 1989
It is possible to disperse high concentrations of finely pulverized beneficiated coal in water to... more It is possible to disperse high concentrations of finely pulverized beneficiated coal in water to produce a stable coal-water slurry fuel (CWF). One of the potential applications of CWF is as a fuel in gas turbines. This represents a relatively novel, developing technology. The gas ...
The major mode of heat transfer in industrial combustion furnaces is that of radiation. The effec... more The major mode of heat transfer in industrial combustion furnaces is that of radiation. The effects of radiative scattering are therefore of great importance in furnace design. This study investigates the behavior of both anisotropic and isotropic scattering using a computer-simulated model of a typical combustion furnaceThe furnace model employed is based on the zoning method of Hottel and the Monte-Carlo statistical approach. To study scattering effects, subroutines to simulate isotropic and anisotropic scattering have been added on to the model developed in earlier work with non-scattering mediums. Anisotropic scattering distributions studied include both forward and backward skewed profilesTo simplify the three-dimensional model, a three by four meter slab of a semi-infinite furnace is studied. Each stab is rectangular in shape, containing twelve cubical zones and incorporating a single burner. Model results are presented in the form of temperature contours and total surface heat fluxes for different scattering albedoes and profiles.
The development of a microcomputer based finite element program featuring phase change (melting a... more The development of a microcomputer based finite element program featuring phase change (melting and freezing) simulation and facilities is outlined. A closed form Galerkin finite element method derived from a delta function formulation of the latent heat discontinuity in the heat capacity versus temperature function is used within phase change elements of the solution domain. Storage reduction data structures are implemented and compared on the basis of overall program execution time. Analytical solutions for melting and freezing are used to vertify program accuracy and to explore other simulation parameters such as time step size, mesh density and start-up technique. Several ''life like'' phase change simulations are compared to the results obtained from other numerical models.
Volume 3: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations, Jun 8, 1986
Eg Blackbody emissive power of gas, W/m 2. It is possible to disperse high concentrations of E s ... more Eg Blackbody emissive power of gas, W/m 2. It is possible to disperse high concentrations of E s Blackbody emissive power of surface, W/m 2. finely pulverized beneficiated coal in water to produce a stable coal-water slurry fuel (CWF). One of f a Fraction of ash in coal, dimensionless. the potential applications of CWF is as a fuel in gas turbines. This represents a relatively novel, developgg Direct gas-gas exchange area, m 2 c
An investigation was undertaken to study the mixing of two miscible phases in coils by secondary ... more An investigation was undertaken to study the mixing of two miscible phases in coils by secondary flow and natural convection. In the absence of natural convection the Dean number was found to be a unique dynamic similarity parameter governing fluid flow and mixing in helical coils, even when the viscosities of the phases are very different. For fluids of differing densities natural convection increased the enhancements by as much as 58%. Mixing enhancement in segmented (i.e., gas partitioned) flow was typically three to four times larger than in nonsegmented flow. Various coil configurations were evaluated for enhancing the mixing. The change of coil curvature with coil length and the initial position of the interface relative to the direction of secondary flow were established as vital parameters affecting mixing.
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