bluuebunny/crossref_metadata_2025_split huggingface dataset:
A new two‐impinging‐streams heterogeneous reactor
Authors: Luzzatto Kfir , Tamir Abraham , Elperin Isaak 
Published: June 2004

AbstractThe characteristics of a new heterogeneous reactor of the “two impinging streams” type, suitable for gas‐solid heat and mass‐transfer operations, were investigated.The operating limits of the reactor, with respect to gas and solid particles mass flow rate and pressure drop, were determined; scale‐up criteria with respect to the hydrodynamics of the reactor were also established. It has been found that, under certain conditions, the introduction of solid particles into the gas stream lowers the pressure drop on the reactor. In addition, the maximal pumping energy per kg of solids transported through the reactor by the air is much lower than in a fluidized‐bed‐type reactor.A stochastic model based on Markov processes was developed which closely describes the behavior of the solid particles in the reactor. A technique based on this model was employed for determining the residence time distribution of the particles in the reactor.
Estimation of parameters where dependent observations are related by equality constraints
Authors: Solomon B. O. , Oner M. D. , Erickson L. E. , Yang S. S. 
Published: June 2004

AbstractPirt's model for microbial growth and product formation are reparameterized to obtain multiresponse models with common parameters. The dependent variables in the models are related through the available electron and carbon balance constraints. Covariance adjustment is used to reduce the growth model to a unit variate linear model with covariates. Therefore, standard multiple regression programs can be used to obtain combined point and interval estimates of true biomass energetic yield, true product yield and maintenance coefficient. This approach may yield “better” estimates than the maximum likelihood approach when an appropriately selected subset of covariates is used. Nonlinear estimation procedures are also considered; these procedures are efficient with few responses; however, as the number of responses per observation increase, they may require a lot of computing time. For illustration several data from the biochemical engineering literature are analyzed by the proposed methods.
Mass transfer in AC electrolysis part II: Experimental study on sinusoidal current
Authors: Cheng C. Y. , Chin D‐T. 
Published: June 2004

AbstractAn experimental study has been made for laminar mass transfer to a rotating disk and a rotating hemispherical electrode when sinusoidal alternating current (AC) together with direct current (DC) are flowing across the electrode/electrolyte interface. A resistor‐capacitor circuit was used to measure the phase shift between the applied AC and the resulting periodical concentration overpotential. The limiting AC current density corresponding to a zero instantaneous surface concentration was determined as a function of AC frequency and DC current density. The experimental data agreed with the theoretical calculations in a regime of a dimensionless AC frequency K = (ω/Ω)Sc1/3 greater than 1 and less than 200.
Gas entry effects in fluidized bed reactors
Authors: Yates J. G. , Rowe P. N. , Cheesman D. J. 
Published: June 2004

AbstractExperimental results from an X‐ray study of gas bubbles entering a fluidized bed of two differently sized powders are presented and their significance for chemical reactions taking place in the distributor region of a fluidized bed reactor are examined using a simple two‐phase model.
Distribution of bubble properties in a gas‐liquid‐solid fluidized bed
Authors: Matsuura Akinori , Fan Liang‐Shih 
Published: June 2004

AbstractThe behavior of bubbles in a cocurrent gas‐liquid‐solid fluidized bed was investigated in a column of 76.2 mm ID in this study. The particles used were glass beads of 3 and 6 mm and a binary mixture of these particles. A novel dual electrical resistivity probe system was developed and utilized to obtain bubble properties including bubble size and rise velocity. The distributions of the bubble properties in the gas‐liquid‐solid fluidized bed were evaluated for three flow regimes: the dispersed bubble flow regime; the coalesced bubble flow regime; and the slug flow regime.
Theory and operational characteristics of the magnetic valve for solids Part II: Collar design
Authors: Zhang Guo‐Tai , Jaraiz‐M. Eladio , Wang Yang , Levenspiel Octave 
Published: June 2004

AbstractThis paper reports on the operating characteristics of the collar type MVS which uses either orifice plates or screens as supports for the solids.The optimum placement for the support (screens or orifice plates), the current needed to operate the valve as a function of vessel size (up to 0.55 m) and screen or orifice opening, and the response characteristics of the valve were all determined. These findings were then compared with theory.Finally, the operational characteristics of the MVS (magnetic valve for solids) when handling a mixture of magnetic and nonmagnetic solids were briefly examined.
Correlation of critical properties and acentric factor of hydrocarbons and derivatives
Authors: Lin Ho‐Mu , Chao Kwang‐Chu 
Published: June 2004

AbstractThe critical constants and acentric factor are generally required in thermodynamic calculations based on the principle of corresponding states. In this work, these properties of hydrocarbons and derivatives are correlated with the molecular weight, specific gravity, and normal boiling point. Properties of n‐alkanes are correlated with the molecular weight. Properties of other hydrocarbons and derivatives are expressed as perturbations from those of the n‐alkanes, and the perturbations are corrlated in terms of specific gravity and normal boiling point.
Growth rate dispersion in MSMPR crystallizers
Authors: Larson M. A. , White E. T. , Ramanarayanan K. A. , Berglund K. A. 
Published: June 2004

AbstractA model is presented which relates the crystal size distribution (CSD) from a mixed–suspension, mixed‐product‐removal (MSMPR) crystallizer to the distribution of growth rates. This model is based on the assumption that individual contact nuclei have some inherent growth rate which remains constant, but the growth rate may vary from crystal to crystal. The crystal size distribution can be calculated from prior knowledge of the growth rate distribution. Even a limited knowledge of only the coefficient of variation and the mean growth rate permits an approximation of the expected crystal size distribution. Conversely, estimates of the mean and variance of the growth rate distribution can be determined from the moments of the CSD from an MSMPR crystallizer.
Separation of helium‐methane mixtures by pressure swing adsorption
Authors: Cheng H. C. , Hill F. B. 
Published: June 2004

AbstractThe separation of mixtures of helium and methane using a single column of activated carbon in a pressure swing adsorption process was studied experimentally. Process performace was predicted with an average error of 10% or less by a local‐equilibrium well‐stirred cell model in which dead volumes at the feed and product ends of the column were accounted for. Systematic differences between experiment and model were ascribed to omission from the model of flow resistance and heat release.
Taylor‐aris dispersion arising from flow in a sinusoidal tube
Authors: Hoagland D. A. , Prud'Homme R. K. 
Published: June 2004

AbstractAn analysis of dispersion arising from creeping flow through a periodically constricted tube is developed with the goal of evaluating the effect of converging and diverging pore structure on dispersion in porous media. The theory is based on rigorous long‐time solutions of the convective‐diffusion equation. The calculations are done numerically over a range of Peclet numbers and tube geometries; for the geometrical parameters which correlate permeability data in packed beds, the results of the present work agree well with literature data for dispersion in such beds.
A generalized model for predicting equilibrium conditions for gas hydrates
Authors: John V. T. , Papadopoulos K. D. , Holder G. D. 
Published: June 2004

AbstractA modification of van der Waals and Platteeuw's (1959) hydrate equilibrium model which incorporates the effect of spherical asymmetry is developed. A corresponding states correlation is used to predict the deviation of Langmuir constants from ideal values. In this model the Kihara parameters obtained from hydrate equilibrium data agree well with those obtained from virial coefficient data.
Surfactant chromatographic movement: An experimental study
Authors: Harwell J. H. , Schechter R. S. , Wade W. H. 
Published: June 2004

AbstractPrevious papers (Trogus et al., 1979a; Harwell et al., 1982) have developed a theory of surfactant chromatographic movement on the assumption that micelles may be treated as a separate thermodynamic phase in predicting surfactant adsorption. The work examined here demonstrates that, even with incorporation of the complex surface interactions between surfactant molecules that are present in real systems, conclusions and observations made in the previous studies hold true. Additionally, theoretical predictions are compared to experimental results to demonstrate that for the system studied the phase separation model of micelle formation (Shinoda, 1963) and the plateau adsorption model (Trogus et al., 1979a) are powerful and useful simplifications for predicting surfactant chromatographic behavior.
A nonequilibrium stage model of multicomponent separation processes. Part II: Comparison with experiment
Authors: Krishnamurthy R. , Taylor R. 
Published: June 2004

AbstractA nonequilibrium stage model of countercurrent separation processes is used to predict composition and temperature profiles during binary and multicomponent distillation in wetted‐wall and bubble‐cap‐tray columns. The profiles predicted by the model are compared with experimental data for the binary systems benzene‐toluene, ethanol‐water, and acetone‐chloroform and for the ternary systems benzene‐toluene‐ethylbenzene, acetone‐methanol‐water, methanol‐isopropanol‐water, acetone‐methanol‐ethanol, and benzene‐toluene‐m‐xylene. The model does a very commendable job of predicting the composition profiles measured for these systems; average absolute differences between predicted and measured mole fractions are seldom greater than 4 mole percent and are often very much less.
The unusual behavior of extractive distillation—Reversing the volatility of the acetone–isopropyl ether system
Authors: Berg Lloyd , Yeh An‐I 
Published: June 2004

AbstractExtractive distillation can not only negate azeotropes to produce pure compounds by rectification but in some cases will reverse the volatility and bring out the less volatile component before the more volatile component. As an example, isopropyl ether, b.p. = 68.5°C, was distilled off as the overhead from mixtures with acetone, b.p. = 56.2°C, leaving the acetone in the stillpot and column until all the isopropyl ether was removed. This reversal phenomenon does not occur in the isopropyl ether‐methyl ethyl ketone system, although the azeotrope is negated.
Longitudinal and lateral thermal dispersion in packed beds. Part I: Theory
Authors: Levec J. , Carbonell R. G. 
Published: June 2004

AbstractA new model is developed for the transient thermal response of a packed bed, using the method of spatial averaging. Equations for the average temperature of the fluid and the solid phase are derived from the point equations for thermal energy in each phase. The new model exhibits some unusual convective and dispersive coupling between the equations for the average fluid and solid temperatures. The response of the model equations to a pulse disturbance is analyzed. It is found that after a sufficiently long time has elapsed, the temperature pulses for the fluid and solid phases will be separated by a constant distance and will spread or disperse about their centroids at an equal rate. The pulse separation predicted by the new model equations is larger than that predicted using more conventional analyses of heat transfer in packed beds. Effective thermal conductivities measured under steady state conditions can differ significantly from those observed in transient experiments due to the spread in temperature pulses caused by heat exchange between phases. Estimates are made of the magnitude of the more important terms affecting longitudinal and lateral effective thermal conductivities under flow conditions, in order to make possible a direct comparison between theory and experiment in a companion paper.
Prediction of steady state dispersion height from batch settling data
Authors: Jeelani S. A. K. , Hartland Stanley 
Published: June 2004

AbstractIn order to design continuous industrial settlers, it has in the past been necessary to obtain extensive pilot plant data, the interpretation of which required considerable experience before it could be used for scale‐up purposes. The idea of using batch settling tests has always seemed attractive, but the difficulty of reconciling unsteady‐ and steady‐state experiments has so far proved physically and mathematically insurmountable.In this study the variation in steady state height with dispersion throughput in a continuous settler is predicted from unsteady state data obtained in a small‐scale batch settler. Models are presented which relate the drop sedimentation and coalescence in batch and continuous dispersions, thus enabling the steady state settler behavior to be predicted from parameters obtained from the batch data. These models are verified with available experimental data and should greatly simplify the future design and scale‐up of continuous settlers.
Development of a catalytic two‐stage combustion system
Authors: Sadakata M. , Shigehisa T. , Kunii D. 
Published: June 2004

AbstractA new NOx‐free combustion system using a new catalyst produced from stainless steel by special treatment was proposed and studied. A series of experiments verified that this new system could produce a high reduction rate of NO under the hostile flue gas conditions of a practical combustion process.
Hydrodynamics and mass transfer characteristics of a scheibel extractor. Part I: Drop size distribution, holdup, and flooding
Authors: Bonnet J. C. , Jeffreys G. V. 
Published: June 2004

AbstractThe hydrodrynamic behavior of a 1.0 × 10−1 m dia. Scheibel column packed with a material preferentially wetted by the dispersed phase has been investigated with and without mass transfer. Drop size and size distribution and dispersed phase holdup were measured as a function of flow rates, agitator speed, packing pad height, and mass transfer direction in a 24 factorial design. Flooding rates were measured and found to be dependent on the impeller position.
Activity coefficients for binary and multicomponent liquid mixtures from unary property model for Wilson parameters
Authors: Ash S. N. , Ray P. , Dutta B. K. 
Published: June 2004

AbstractA model has been developed for prediction of Wilson parameters from single component properties. Activity coefficients and VLE data for miscible binary or multicomponent systems can be calculated from the standard form of the Wilson equation using these properties. The major advantage of this model is that experimental determinations of binary data are not required. Relevant properties for a fairly large number of chemical species have been provided. This method has been compared with UNIFAC, which is generally used for prediction of activity coefficients and has been found to give comparable results with considerably less computational effort.
Solids mixing in an expanded top fluid bed
Authors: Avidan Amos , Yerushalmi Joseph 
Published: June 2004

AbstractThis study investigated solids mixing of a group A fine powder in a 0.15 m ID expanded top fluid bed with a ferromagnetic tracer. The superficial gas velocity was raised from 0.075 to 1.1 m/s, causing the bed to go through bubbling, slugging, and turbulent fluidization regimes. A countercurrent flow model described the data well at low gas velocities. The bed assumed a more homogeneous appearance at higher gas velocities; a one‐dimensional axial dispersion model was used to correlate the data. Axial dispersion coefficients increased with gas velocity. The data agree well with literature data for low gas velocities.
Heat and mass transfer in water‐laden sandstone: Microwave heating
Authors: Wei Chen Kou , Davis H. T. , Davis E. A. , Gordon Joan 
Published: June 2004

AbstractOur previous theoretical model was extended to predict the heat and mass transfer phenomena in microwave‐heated porous materials. A water‐filled sandstone was heated in microwaves and its drying rates and temperature profiles were measured. Predictions agree well with observations. Besides moisture loss rates and temperature profiles, the model also predicts local moisture content, gas densities, and pressure. These latter quantities were not measured in our work, but are of interest since they reveal the basic mechanisms of heat and mass transfer in internally heated porous media.
Mathematical modeling of catalytic converter lightoff. Part II: Model verification by engine‐dynamometer experiments
Authors: Oh S. H. , Cavendish J. C. 
Published: June 2004

AbstractA transient mathematical model has been developed which describes the behavior of packed‐bed catalytic converters during warmup. Model predictions agree very well with the results of engine‐dynamometer experiments for three Pt‐alumina catalysts of widely different properties, thus demonstrating the validity of the model.
Mathematical modeling of catalytic converter lightoff. Part III: Prediction of vehicle exhaust emissions and parametric analysis
Authors: Oh S. H. , Cavendish J. C. 
Published: June 2004

AbstractThe converter warmup model developed previously (Oh and Cavendish, 1985) has been used to simulate the performance of a packed‐bed converter during the cold‐start portion of vehicle emissions tests. Despite the highly transient converter inlet conditions, the model successfully predicts tailpipe mass emissions as a function of time.
Porosity effects on catalytic char oxidation. Part II: Experimental results
Authors: Su J. L. , Perlmutter D. D. 
Published: June 2004

AbstractOxidation rates of Na2CO3‐ and K2CO3‐impregnated char samples were measured in an isothermal kinetic control regime. The results were analyzed by a previously developed model to extract the intrinsic catalytic reactivities, freed from superimposed noncatalytic and structural effects. Although the overall catalyzed rates are only several times greater than their uncatalyzed counterparts, the intrinsic catalytic rates were found to be four orders of magnitude greater. The results further indicate that the function of the catalyst is to increase the number of active sites without affecting the activation energy. The overall reaction kinetics are demonstrated to contain the combined contributions of both catalytic and noncatalytic reactions, and in this context the effects of multiple catalysts as well as of the pore structure development during reaction can be understood and interpreted.
Adsorption of gaseous hydrocarbons on activated carbon: Characteristic kinetic curve
Authors: Costa E. , Calleja G. , Domingo F. 
Published: June 2004

AbstractThe internal diffusion coefficients, Di, of pure methane, ethane and ethylene as well as some of their binary and ternary mixtures, have been calculated at 20°C for solid particles of a commercial activated carbon. It has been observed that the contribution of the surface migration mechanism to the global mass transfer process inside the adsorbent particles can be as much as 70–80%. Values for the surface migration coefficient Ds have also been calculated from the relation Di = Dg + KDs, where K is a dimensionless mean slope factor. Values found for both coefficients are of the same order of magnitude as those reported in the literature for similar systems.All the values for the internal diffusion coefficients of these pure components and their mixtures fit into a single correlation curve, the characteristic kinetic curve of the adsorbent.
On dense phase voidage and bubble size in high pressure fluidized beds of fine powders
Authors: Weimer A. W. , Quarderer G. J. 
Published: June 2004

AbstractDense phase voidage, εD, dense phase superficial gas velocity, uDo, and absolute bubble rise velocity, uB, were measured at pressures up to 8300 kPa in a pilot‐scale, fluidized bed of Group A and boundary Group A/B powders. The mean equivalent bubble diameter, db, near the top of the bed was inferred from uB, and known bed operating conditions. Increased pressure at fixed superficial gas velocity, uo, increased εD and uDo and decreased db for Group A powders. The marked decrease in inferred maximum bubble size, d with increased pressure could not be explained by a decrease in gas contributing to bubble flow, uBo, but rather appeared to be the result of a bubble instability phenomenon limiting bubble growth.
Determination of mass transfer coefficients for bubble‐free devolatilization of polymeric solutions in twin‐screw extruders
Authors: Collins G. P. , Denson C. D. , Astarita G. 
Published: June 2004

AbstractTheoretical and experimental studies have been conducted on the mass transfer rates which occur during the continuous devolatilization of bubble‐free polymeric solutions in a corotating twin‐screw extruder. Experimental measurements of the mass transfer rates, when reported in terms of the product of the individual liquid phase mass transfer coefficient and the surface area for mass transfer per unit volume of empty extruder, were found to correlate well with screw speed in accordance with the predictions of a model based on penetration theory. It is shown, however, that significant differences exist between the measured and predicted values for the rates of mass transfer, which leads to the conclusion that the surface area for mass transfer is substantially smaller than the value computed on the basis that continuous films are formed on the surfaces of the screws and the barrel wall.
Nonisothermal gas absorption with chemical reaction
Authors: Asai Satoru , Potter O. E. , Hikita Haruo 
Published: June 2004

AbstractThe temperature rise at a gas‐liquid interface due to heat evolution and the relevant enhancement factor for gas absorption rate are analyzed for absorption, with an instantaneous irreversible reaction and with a first‐order irreversible reaction allowing for the temperature dependence of the major physicochemical properties. The analysis reveals that, unlike isothermal absorption, the film theory solutions with the replacement of any system parameters do not give a reasonable approximation to the realistic penetration theory solution, except in the case of the physical absorption regime. However, the modified Danckwerts analysis, in which the physicochemical properties are evaluated at the time‐averaged interface temperature, is shown to be useful in obtaining the approximate penetration theory solutions with satisfactory accuracy.
Kinetics of CO oxidation over Co3O4/γ‐Al2O3. Part II: Reactor dynamics
Authors: Perti Deepak , Kabel R. L. 
Published: June 2004

AbstractThe transient responses of a fixed‐bed reactor to step increases and decreases in CO, O2, and/or CO2 feed concentrations were measured and interpreted. It is shown that dynamic methods yield vastly more phenomenological and mechanistic information than steady state measurements, with significantly less experimental effort.
Short‐lived sites in nucleate boiling
Authors: Myers J. E. 
Published: June 2004

AbstractAn hypothesis is proposed to explain the origin of short‐lived sites observed in nucleate pool boiling. Conditions are postulated under which microbubbles might circulate into the superheated liquid region and serve as the source of these nucleation sites. Consequences of this possible mechanism are examined for explanations of hysteresis effects and scatter of results in boiling research.