bluuebunny/crossref_metadata_2025_split huggingface dataset:
The influence of temperature on surface and microscopic properties of surfactant solutions in relation to fluid displacement efficiency in porous media
Authors: Sharma M. K. , Shah D. O. , Brigham W. E. 
Published: June 2004

AbstractThe surface properties, microscopic structure of foam, and flow through porous media behavior of mixed surfactant solutions (sodium lauryl sulfate plus lauryl alcohol) have been studied at various temperatures in relation to enhanced heavy oil recovery processes. The studies reported here suggest that temperature has a remarkable influence on the microscopic structure of foam and the flow through porous media behavior of the surfactant solutions. The surface tension and bubble size decreased as the temperature increased. The foam volume increased, whereas foam half‐life (or foam stability) decreased with increasing temperature. A linear increase in bubble size with time was observed at different temperatures. The rate of change in bubble size increased with temperature. A significant reduction in effective air mobility and an improvement in fluid displacement efficiency were observed with increasing temperature. All measured parameters changed strikingly in the temperature range of 20–40°C, whereas they exhibited small changes between 40 and 80°C for the surfactant system investigated. The effect of temperature on half‐life of foam and on the effective air mobility was most pronounced as compared to that on other parameters. An attempt is made to correlate quantitatively the foam volume of surfactant solution with fluid displacement efficiency in porous media.
Reduced‐order, multivariable models with pure time delays
Authors: Iwai Zenta , Fisher D. G. , Seborg D. E. 
Published: June 2004

AbstractMarshall's method of model reduction (1966) neglects the modes of the high order system which contribute little to the overall system response. This approach is extended to handle complex and/or repeated eigenvalues and is then modified so that pure time delays can be included in the control variables of the reduced order model. Open‐ and closed‐loop examples show that the inclusion of the time delays tends to compensate for the eliminated modes and leads to better agreement between the high and low order models.
The effect of interfacial tension gradients on the flow structure of single drops or bubbles translating in an electric field
Authors: Chang L. S. , Berg J. C. 
Published: June 2004

AbstractStream functions, interfacial velocities, and terminal velocities are computed for spherical drops or bubbles supporting interfacial tension gradients and translating in creeping flow in an electric field imposed in the direction of translation. In particular, the case in which a trace of surfactant is present is considered, and it is found that such material may produce quasi‐stagnant zones along the interface either near the poles or the equator. Terminal velocities may be either increased or decreased relative to the value obtained in the absence of the electric field.
Mass transfer in a liquid‐liquid CFSTR
Authors: Bapat P. M. , Tavlarides L. L. 
Published: June 2004

AbstractThe performance of a two‐phase liquid‐liquid continuous flow stirred tank reactor (CFSTR) was evaluated experimentally by simultaneous determination of dispersed phase drop size distribution and extraction efficienty as a function of reactor operating conditions. The results provided a basis against which predictions made by a previously developed simulation technique (Bapat et al., 1984) were compared. The close agreement between the experimental and the simulation results validates the drop rate models and the simulation algorithm employed in this work.
Rates of pyrolysis of colorado oil shale
Authors: Pan Zhenglu , Feng H. Y. , Smith J. M. 
Published: June 2004

AbstractBoth intrinsic kinetics and rates of decomposition in larger particles were determined for a Colorado shale by weight‐loss measurements in TGA‐type equipment. The data for small granular particles indicated first‐order intrinsic kinetics up to a fractional weight change that depended on the temperature level. In the experiments with larger particles, gas, particle‐surface, and particle‐center temperatures measured in separate runs showed that both gas‐to‐particle and intra‐particle temperature differences were significant.A heat transfer model was evaluated by using the intrinsic kinetics data, measured heat transfer coefficients, and shale properties from the literature, to predict weight loss and particle‐center temperatures for the larger particles. Comparison with observed results showed good agreement in general, although there was some deviation in weight‐loss results at low temperatures.The combined set of intrinsic kinetics data and rates for larger particles should be useful for further studies of pyrolysis models.
Characterization of a membrane permeation system for controlled drug delivery studies
Authors: Tojo K. , Sun Y. , Ghannam M. M. , Chien Y. W. 
Published: June 2004

AbstractHydrodynamic characteristics of an in vitro membrane permeation system for controlled drug delivery studies were investigated by measuring dissolution rates of benzoic acid in various aqueous solutions of polyethylene glycol 400. The mass transfer coefficient was well correlated in terms of three dimensionless numbers: Sherwood, Schmidt, and Reynolds numbers. By using the correlation equation, the intrinsic permeation rate of testosterone through silicone membranes was precisely extracted from the experimental data obtained under various nonideal flow conditions.
Thermal regeneration of diesel‐particulate monolithic filters
Authors: Bissett E. J. , Shadman Farhang 
Published: June 2004

AbstractA mathematical model is developed to describe the process of thermal regeneration in diesel‐particulate monolithic filters. The model shows that a typical regeneration cycle consists of four stages: preheating, ignition, transport‐controlled combustion, and cooling. The total regeneration time and the peak temperature are the important regeneration characteristics and can be controlled by initial particulate loading, total filtration area, and channel wall thickness.
A simultaneous transport‐reaction model for controlled drug delivery from catalyzed bioerodible polymer matrices
Authors: Thombre A. G. , Himmelstein K. J. 
Published: June 2004

AbstractA simultaneous diffusion‐reaction model is presented for the analysis of the kinetics of a chemically eroding poly(orthoester) matrix incorporated with a bioactive agent and with a catalyst to promote the erosion. Simulation results are consistent with experimentally observed hollow residuals and provide a basis for analyzing various design options.
Hydrodynamics and mass transfer characteristics of a scheibel extractor. Part II: Backmixing and stage efficiency
Authors: Bonnet J. C. , Jeffreys G. V. 
Published: June 2004

AbstractThe transfer of acetone between the toluene phase (dispersed) and the aqueous phase (continuous) has been measured along the length of a four‐stage Scheibel column packed with material preferentially wetted by the dispersed phase. (A Scheibel stage is defined as one mixing section plus one packing section.) The column concentration profiles were obtained by applying a new technique developed for this investigation.A parameter model‐fitting exercise has been developed to select the most appropriate mathematical model that quantifies the extent of backmixing in the dispersed and continuous phases and evaluates the stage efficiency.Overall dispersed phase mass transfer coefficients were estimated using the drop size and holdup data presented in Part I, and these have been compared with the published correlations based on single drop mechanisms.
Mobility control in the displacement of residual oil by an unstable foam
Authors: Hahn Pil‐Soo , Ramamohan T. R. , Slattery J. C. 
Published: June 2004

AbstractA qualitative analysis is developed for the displacement of an unstable foam in a porous structure. The effects of the magnitude of the London‐van der Waals forces, of the surface tension, of the surface viscosities, of the quality (volume fraction of the gas), of the bubble size, and of the viscosity of the foaming agent solution are investigated. A number of qualitative conclusions are drawn regarding three aspects of mobility control: distribution of bypassed oil, speed of displacement, and displacement efficiency.Ideally, any change in formulation should increase both the speed of displacement and the displacement efficiency. This is possible only by decreasing the surface viscosities. With all of the other variables, whenever either the speed of displacement or the displacement efficiency is increased, the other is decreased. Whether both the speed of displacement and the displacement efficiency actually increase on reducing the surface viscosities depends on whether the effects of the surface viscosities are dominant.
A generalized methodology for estimating minimum fluidization velocity at elevated pressure and temperature
Authors: Yang Wen‐Ching , Chitester D. C. , Kornosky R. M. , Keairns D. L. 
Published: June 2004

AbstractA generalized methodology for estimating minimum fluidization velocity at elevated pressure and temperature was developed on the basis of a general correlation for pressure drop through fixed beds of spherical particles proposed by Barnea and Mizrahi (1973) and extended by Barnea and Mednick (1975). Comparison with experimental results shows good agreement.
Multiplicity in continuous MSMPR crystallizers. Part I: Concentration multiplicity in an isothermal crystallizer
Authors: Tavare N. S. , Garside John 
Published: June 2004

AbstractA theory for the identification of criteria within which a continuous isothermal mixed‐suspension, mixed‐product removal (MSMPR) crystallizer can exhibit concentration multiplicity (i.e., multiple steady states) is developed. Power law growth and power law magma‐dependent nucleation kinetic models are used to describe the crystallization kinetics. Applications to specific cases together with figures delineating regions of multiplicity are presented. The stability of these steady states is analyzed by using small perturbations around the steady state. Growth ratedispersion is shown to be unimportant in establishing this concentration multiplicity.
Real‐time estimation of dynamic particle‐size distributions in a fluidized bed: Theoretical foundation
Authors: Cooper D. J. , Clough D. E. 
Published: June 2004

AbstractSignificant noise (random error) is common in an on‐line signal when measuring the particle size distribution in a fluidized bed. The application of optimal estimation theory to obtain a filtering algorithm that can rectify such measurements is detailed. Off‐line simulation studies demonstrate that the filtering algorithm yields a measure of particle size distribution that is well‐behaved, accurate, and able to track in real time as conditions change in the bed.
Kinetics of CO oxidation over Co3O4/γ‐Al2O3. Part I: Steady state
Authors: Perti Deepak , Kabel R. L. 
Published: June 2004

AbstractSteady state experiments and their interpretation were performed to explore the kinetics of CO oxidation over a supported Co3O4 catalyst. The rate of reaction was found to depend on temperature and the partial pressure of oxygen but not on the partial pressure of carbon monoxide. It is shown that catalyst dynamics must be accounted for to achieve real understanding.
Liquid holdup and heat transfer coefficient in liquid‐solid and three‐phase fluidized beds
Authors: Chiu Tai‐Ming , Ziegler E. N. 
Published: June 2004

AbstractLiquid holdups and wall‐to‐bed heat transfer coefficients in three‐phase fluidized beds with glass beads and cylindrical γ‐alumina particles were determined experimentally. It was found that the product of heat transfer coefficient and liquid holdup in three‐phase fludized beds is equal to that in corresponding liquid‐solid fluidized beds. A generalized correlation equation for heat transfer coefficients in both liquid‐solid and three‐phase fluidized beds was proposed based on the above relationship.
Deterministic variability analysis for intermediate storage in noncontinuous processes. Part I: Allowability conditions
Authors: Karimi I. A. , Reklaitis G. V. 
Published: June 2004

AbstractNoncontinuous processes involving batch and semicontinuous processing operations are typically subject to significant levels of process parameter variations. Intermediate storage is commonly used to mitigate the effects of these variations. A taxonomy and analysis is presented of the various types of parameter variations: elementary and composite, single and multiple, homogeneous and mixed, overlapping and nonoverlapping. Sufficient conditions are developed which insure that continuity of periodic operation can be maintained in the presence of these various types of process variations. These conditions serve as the basis of storage sizing procedures developed in the companion paper.
A generalized equation of state for the thermodynamic properties of polar fluids
Authors: Wu G. Z. A. , Stiel L. I. 
Published: June 2004

AbstractThe generalized relationships of Lee and Kesler for the thermodynamic properties of nonpolar fluids have been combined with an accurate equation of state for water which is utilized as the reference substance for polar fluids for reduced temperatures from 0.4 to 2.5 and reduced pressures to 10. The input data required are the critical temperature, critical pressure, acentric factor, and a polarity factor Y obtained from experimental pressure‐volume‐temperature data. Comparisons between calculated and experimental thermodynamic properties indicate that highly accurate results are obtained by the method of this study for most polar fluids. A modified procedure is presented for the compressibility factors of substances with large acentric factors such as alcohols. Tabulated values of the polar fluid correction terms are presented for the compressibility factor, fugacity coefficient, and enthalpy, entropy, and heat capacity departures for the complete range investigated.
Periodic cycling of distillation columns using a new tray design
Authors: Szonyi L. , Furzer I. A. 
Published: June 2004

AbstractComputer simulations of periodically cycled columns predicted improvements in column performance of greater than 200% for systems with nonlinear equilibrium curves. Experiments distilling methanol‐water mixtures have verified those predictions for periodic cycling with a single plate. The extension of the theory to multiple‐plate columns fails in usual distillation apparatus due to liquid mixing during the liquid flow period. To overcome this problem a new tray design consisting of a sieve plate and inclined surfaces has introduced an effective liquid time delay. Although the predicted efficiencies of 200% were not realized due to vapor movement hindering the tray action, a wide range of operating conditions provided good overall column efficiencies of 140%.
Measuring simultaneous mixing and reaction in batch reactors by dilatometry
Authors: Ghodsizadeh Yousef , Adler R. J. 
Published: June 2004

AbstractA dilatometric technique is reported for studying simultaneous mixing and reaction as a function of time in batch systems. Volume‐averaged fractional conversion is determined from small volume changes without sampling or flow disturbances.Data are obtained for very fast and intermediate speed reactions in a turbulent, unbaffled, stirred laboratory reactor.
Theory and application of an extended horizon self‐tuning controller
Authors: Ydstie B. E. , Kershenbaum L. S. , Sargent R. W. H. 
Published: June 2004

AbstractA robust version of the self‐tuning regulator is developed. The regulator, which requires relatively little knowledge of system characteristics (estimated order of transfer function polynomials and an upper bound for transportation delays), has been shown to yield stable control and convergence for linear, time‐invariant systems. Simulations and practical tests on a large pilot‐scale process have shown that the inclusion of a variable forgetting factor and an “extended horizon” control criterion provides the regulator with a sufficient degree of robustness and flexibility to perform well in a nonlinear time‐varying environment. The regulator makes use of intuitively easy‐to‐understand concepts and leaves few degrees of freedom for the potential user. Furthermore, extensive experiments and simulation studies have shown it to be insensitive to choice of initial conditions and dynamic characteristics set by the user.
Hydrodynamic characteristics of a gas‐liquid‐solid fluidized bed containing a binary mixture of particles
Authors: Fan Liang‐Shih , Matsuura Akinora , Chern Song‐Hsing 
Published: June 2004

AbstractHydrodynamic characteristics were investigated in a cocurrent gas‐liquid‐solid fluidized bed containing a binary mixture of particles. The binary mixtures used were ten combinations of eight types of spherical particles differing in diameter and/or density. The density variation of the particles in the mixture was found to exhibit a stronger effect on the extent of solids mixing or segregation than did the size variation of the particles in the mixture. Additionally, a solids layer inversion phenomenon was found to occur in a bed of small, heavy alumina beads and large, lighter glass beads. The minimum fluidization velocity of binary mixtures correlated well empirically with the superficial gas velocity, weight fraction of jetsam particles, and particle terminal velocities of jetsam and flotsam particles. Bed expansion and gas holdup for a binary mixture were analyzed for three solids mixing states, namely, complete segregation, partial intermixing, and complete intermixing. The analysis indicates that the serial model, or segregation model, predicts the bed voidage satisfactorily even when the bed is at the complete intermixing state.
Further development of selective physisorption for measuring catalyst surface area
Authors: Toor I. A. , Lee H. H. 
Published: June 2004

AbstractPlatinum supported on silica is used as a model supported catalyst for the purpose of demonstrating that the selective physisortion method yields the fractional catalyst surface area of supported catalysts, inclucing metal compounds catalysts for which the method is primarily intended. The selective physisorption results with nitrous oxide as adsorbate are compared with hydrogen chemisorption results for this purpose. Experimental and theoretical refinements of the method developed earlier in our laboratory are presented that allow rather accurate determination of the catalyst surface area. The refinements also make the method effctive even when the catalyst covers a small portion of the total surface area. Because of the nature of physisorption, the method should be applicable to any supported catalyst including metal compounds catalysts, provided a suitable adsorbate is used. Adsorbates other than nitrous oxide and carbon dioxide which are suitable for selective physisorption, are suggested.
Gas absorption with zero‐order chemical reaction
Authors: Riazi Mohammed , Faghri Amir 
Published: June 2004

AbstractThe governing differential equation for gas absorption in laminar falling film with zero‐order homogeneous reaction is solved analytically by the method of separation of variables, and subsequent solution with confluent hypergeometric function. The result for concentration profile was obtained in the forms of a sum of a polynomial and an infinite series of hypergeometric functions.An enhancement factor, E, is defined as the ratio of the calculated absorption rates and the absorption rates found from a simple penetration model. When the Hatta number, is greater than 2, the enhancement factor is given by a simplified form with an error of less than 2%.
Pressure swing adsorption. Part III: Numerical simulation of a kinetically controlled bulk gas separation
Authors: Raghavan N. S. , Ruthven D. M. 
Published: June 2004

AbstractA numerical simulation has been developed for a simple two‐bed PSA system in which kinetic effects and changes in flow rate due to adsorption are significant. The model is therefore more general than most previous models for the PSA cycle. The model equations are solved by the method of double collocation. When applied to air separation on a carbon molecular sieve, using independently measured kinetic and equilibrium parameters, the predicted performance appears consistent with available performance data for a commercial unit.
Nonlinear parameter estimation: A case study comparison
Authors: Biegler L. T. , Damiano J. J. , Blau G. E. 
Published: June 2004

AbstractThe literature abounds with the application of optimization methods for estimating model parameters in equation systems. The utility of these methods is frequently demonstrated on pathological examples using simulated data generated from a known model with a random error component and a known statistical distribution. Unfortunately, parameter estimation problems encountered in practice do not have this advantage. The true model is frequently not known. In fact, one is faced with choosing among various candidate models, all of which may be wrong. Moreover, the error structure is generally unknown and must be estimated from the data. Finally, a great deal of mathematical expertise is required to transform the model and select meaningful starting guesses before parameter estimation can be successful.In order to demonstrate the difficulties of parameter estimation in the industrial environment and the limitations of existing methods, a parameter estimation problem formulated by the Dow Chemical Company is presented and solved. This test problem consists of a stiff differential/algebraic (DAE) model that describes complex kinetics and requires the estimation of nine parameters from batch reactor data. Here the model was inadequate to describe the data, the error structure was not specified and the starting guesses led to a nontrivial optimization problem.The Dow parameter estimation problem was distributed in 1981 to 165 researchers as a followup to the 1980 FOCAPD conference. Of those researchers, eleven agreed to apply their methodologies and expertise to this problem. However, only five acceptable solutions were finally submitted. Here we present and compare these results. Each solution was obtained using different strategies. In most cases the form of the model was also changed to accommodate the algorithms used and to ease the solution procedure. Therefore, while this case study does not present a direct numerical comparison of algorithms, it does offer guidelines and insight towards the solution of difficult parameter estimation problems.
A general design equation for air lift pumps operating in slug flow
Authors: Clark N. N. , Dabolt R. J. 
Published: June 2004

AbstractAir lift pumps are finding increasing use where pump reliability and low maintenance are required, and where corrosive, abrasive, or radioactive fluids must be handled. Although air lifts are used in nuclear fuel reprocessing plants, no general, theoretically sound equation has been proposed in the literature for tall air lift design. Such an equation is developed from two‐phase flow theory to predict the height to which an air lift pump operating in the slug flow regime can lift a given volumetric flow rate of liquid, given the air flow rate and pressure at the point of gas introduction. The widely used drift‐flux model for the prediction of holdup is combined with an approximate relationship to predict pressure loss, and is substituted into the total pressure differential. Integration of the resulting equation provides an explicit formula for the calculation of lift. Experimental work using a variety of liquids in a 38 mm dia. air lift test installation supports the new design equation and demonstrates its flexibility.