bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stability of dissolving or depositing surfaces
Authors: Thorsness C. B. , Hanratty Thomas J. 
Published: June 2004

AbstractIn a previous paper, we have examined the variation of the mass transfer rate along a small amplitude wavy surface which is exchanging mass with a turbulently flowing fluid. We now use these results to show that a soluble flat surface is unstable in the presence of a turbulent flow. The wavelength of the most rapidly growing surface disturbance, made dimensionless with respect to the friction velocity and the kinematic viscosity, is found to be a very weak function of the Schmidt number. These results provide a possible explanation for wavelike dissolution patterns observed in caves and on the underside of river ice. The analysis predicts that deposition patterns should be quite different from dissolution patterns in that the most rapidly growing wave for deposition has a length of zero.
The effect of gas and solids maldistribution on the performance of moving‐bed reactors: The reduction of iron oxide pellets with hydrogen
Authors: Yagi Jun‐Ichiro , Szekely Julian 
Published: June 2004

AbstractA mathematical formulation is presented describing the reduction of iron oxide pellets with hydrogen in a counterflow moving‐bed arrangement under conditions such that both the gaseous and the solids streams may be maldistributed. This maldistribution is imposed on the system by prescribing a radial variation in the void fraction and the particle size, together with a radial variation in the axial velocity of the solid stream.In the formulation, allowance has been made for realistic chemical kinetics and nonisothermal behavior. Computer results are presented for both the maldistributed system and for base line cases where uniform gas and solids flow have been postulated.It was found that maldistribution may play a very marked role in affecting the performance of the system, in particular, when the gas and the solid streams are mismatched, for example, preferential flow of gas near the walls and preferential flow of solids in the central core.
Extension and application of the pitzer equation for vapor‐liquid equilibrium of aqueous electrolyte systems with molecular solutes
Authors: Chen Chau‐Chyun , Britt Herbert I. , Boston Joseph F. , Evans Lawrence B. 
Published: June 2004

AbstractThe semi‐empirical Pitzer equation for modeling equilibrium in aqueous electrolyte systems has been extended in a thermodynamically consistent manner to allow for molecular as well as ionic solutes. Under limiting conditions, the extended model reduces to the well‐known Setschenow equation for the salting out effect of molecular solutes. To test the validity of the model, correlations of vapor‐liquid equilibrium data were carried out for three systems: the hydrochloric acid aqueous solution at 298.15°K and concentrations up to 18 molal; the NH3‐CO2aqueous solution studied by Van Krevelen et al. (1949) at 293.15°K; and the K2CO3‐CO2aqueous solution of the Hot Carbonate Process with temperatures from 343.15°K to 413.15°K and concentrations up to 40 weight percent equivalent potassium carbonate. The success of the correlations suggests the validity of the model for aqueous electrolyte systems of industrial interest.
Characterization and analysis of continuous recycle systems
Authors: Mann Uzi , Rubinovitch Michael , Crosby Edwin J. 
Published: June 2004

AbstractA general analysis of continuous recycle systems and models is presented by considering the fluid history inside the systems. The history of a fluid element is expressed in terms of the number of cycles it completes, its residence time in the system and the total time it resides in a specific section of the systems. Concepts from probability theory are used to derive expressions for the number of cycles distribution (NCD), the residence time distribution (RTD), and the total regional residence time distribution (TRRTD) and their means and variances. Applications of these distributions in various processes are considered. Relationships between the number of cycles, the residence time, and the total regional residence time are expressed in terms of the covariances and correlation coefficient of pairs of these variables. These relationships allow the estimation of one variable for a given value of the other, and thus provide a mathematical means to completely describe the history of fluid in a recycle system.
Prediction of stagnation and minimum pressure points for thin films of power law and Bingham liquids
Authors: Roy S. K. , Agarwal J. P. 
Published: June 2004

AbstractThis study concerns the determination of stagnation point and minimum pressure point film thicknesses when a vertical flat plate is withdrawn from a reservoir containing non‐Newtonian liquids. Upon consideration of three types of liquids, namely, Ellis, power law, and Bingham liquids, it has been found that stagnation point or minimum pressure point film thickness is a function of two parameters, one characterizing the liquid and the other representing parallel flow film thickness. It has also been shown that in the case of power law liquids, both the stagnation point and minimum pressure point exist, while in the case of Bingham liquids, the existence of one or both the points for a given nondimensional parallel flow film thickness depends upon the value of the Bingham number. Furthermore, it has been found that there may be situations when both the points can coincide; for example, in the case of Newtonian liquids, the two points coincide if the parallel flow film thickness is \documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt {2 - \sqrt 3 } $\end{document}.
Sedimentation of flocculent suspensions: State of the art
Authors: Fitch Bryant 
Published: June 2004

AbstractThree modes or types of sedimentation are recognized in flocculent suspensions:Clarification, in which floccules are separated and settle independently;zone settling, in which floccules are incorporated into some solids structure so that all are constrained to subside at more or less the same rate; andcompressionorcompaction, in which the solids structure is strong enough to exhibit a compressive yield value. Current models for sedimentation in the three modes are reviewed, with particular emphasis on their use and reliability (or lack of it) for sedimentation basin design. Most models of thickening presented in the literature derive from a basic partial differential equation for force balance. Models differ in which terms of the equation are disregarded. Several of the theories of compaction are essentially equivalent solutions for the same model, but with different sets of independent variables.
Measurement and scale‐up of secondary nucleation kinetics for the potash alum‐water system
Authors: Garside John , Jančić Slobodan J. 
Published: June 2004

AbstractSecondary nucleation kinetics for potash alum in draft‐tube baffled crystallizers have been determined from steady state crystal size distributions measured down to about 5 μm. Differences in nucleation rates were found for crystallizers of similar geometry but different capacity. Models relating the frequency of crystal/propeller collisions to crystallizer geometry and operating parameters were compared. In general, these successfully accounted for the observed differences in nucleation rates.
Moving‐bed solids flow in an inclined pipe leading into a fluidized bed: Part I. Gas leakage and pressure drop
Authors: Chen Te‐Yu , Walawender Walter P. , Fan L. T. 
Published: June 2004

AbstractFor moving‐bed solids flow in an inclined pipe leading into a fluidized bed, the pressure drop across the pipe is a retarding force while the gas leakage rate alters the flow properties of the solids. The pressure drop has been related to the pipe exit pressure, which, in turn, can be calculated by integrating the solids bulk density over the bed depth. A correlation for the rate of gas leakage in terms of the geometric features and operating conditions of the system is developed. The correlation agrees with experimental data to within ± 25%. Part II of this paper will deal with solids flow.
A gas adsorption isotherm equation based on vacancy solution theory
Authors: Suwanayuen Solot , Danner Ronald P. 
Published: June 2004

AbstractA new Isotherm equation for pure gas adsorption is developed and tseted. In the new method, the adsorption equilibrium is treated as an osmotic equilibrium between two “vacancy” slutions having different compsoitions. One solutions represents the gas phase and the other the adsorbed phase. The vacancy solution is composed fo adsorbates and vacancies. the latter is an imaginary entity defined as the vacuum space which acts as the solvent for the system. Thermodynamic equations governignt he euilibrium of this system are used to derive the equation of state for the adsorbed phase. The non‐ideality of the adsorbed solution is accounted for in terms of an activity coefficent whose compsotion dependence is decribed by the Wilson equation. The equation of state, together the Gibbs adsorption equation, is then used in the derivaion of the adsorption isotherm equation. The developed correlation has been evalued with the adsorption isotherm data of O2, N2, and CO on zeolite 10X at 144.3 K, 172.0 K, 227.6 K and 273.2 K, and that of CH4, C2H2, C2H4, C2H6, C3H8, nC4H10, and CO2 on Nuxit‐AL activated carbon at 293.2 K, 313.2K, 333.2 K and 363.2 K. For both adsorbents, the correlations are better than those obtained by any other adsorption model which has been extended to gas mixtures. The parametes obtained from the pure component data can be use to predict a priori, gas‐mixture equilibria.
Vacancy solution theory of adsorption from gas mixtures
Authors: Suwanayuen Solot , Danner Ronald P. 
Published: June 2004

AbstractA new correlation that improves predictions of gas mixtrue adsorption equilibria from single‐component adsorption isotherm data is eveloped, based on the vacancy solution theory. In this theory, the adsorbed phase and the gas phase are treated as two cavancy solutions. The vacancy is an imaginary solvent occupying spaces that will be filled by adsorbates. The composition relationship between the two phases is derived from thermodynamic equilibrium criteria. The non‐ideality of the absorbed solution is accounted for by an acitivity coefficient, whose composition dependence is described by the Wilson equation. For an adsorption system, the binary parameters, adsorbate and vacancy, can be obtained from regression of the pure gas adsorptio data with the cavancy solution isotherm equation. These parameters are then used to predict multicomponent adsorption equilibirum, assuming hat the adsorbate‐adsorbate interactions are negligible. The new correlation has been tested on two different kinds of binary adsorption systems. The new method is more geneeral, simpler to apply, and more accurate than other available models. The predictions can be further improved by taking into account the assorbate‐adsorbate interactions.
Structural analysis of multicomponent reaction models: Part II. Formulation of mass balances and thermodynamic constraints
Authors: Sorensen Jan P. , Stewart Warren E. 
Published: June 2004

AbstractSimulation of chemical reactors requires the formulation of mass balances, often coupled with thermodynamic constraints such as ionization and chemisorption equilibria. We provide a systematic procedure for selecting the smallest sufficient set of dependent variables and a corresponding set of mass balances. The procedure depends on the type of reactor, and is developed for two common reactor types. The procedure is implemented on a computer and illustrated by examples from catalysis and electrochemistry.
Intraparticle mass transfer in coal pyrolysis
Authors: Gavalas George R. , Wilks Karl A. 
Published: June 2004

AbstractIntraparticle mass transfer in coal pyrolysis is described by ternary diffusion and viscous flow, in conjunction with a simple pore model to predict concentration profiles for gases and tar. At low pressures, product yields depend on particle size only, while at high pressures they depend on pressure and particle size. Limited experimental data from a subbituminous coal confirm these trends. Data from a bituminous coal show different trends, as expected from the drastic changes the pore structure undergoes during pyrolysis.
Improving distillation column design using thermodynamic availability analysis
Authors: Fitzmorris R. E. , Mah R. S. H. 
Published: June 2004

AbstractThis is a comprehensive availability analysis of conventional, vapor recompression and SRV (secondary reflux and vaporization) distillation. The physical significance of different availability losses is interpreted, and the magnitude and distribution of these losses in an ethyleneethane separation are shown. Also discussed is how they may be reduced by design modifications.
A crossflow model of dispersion in packed bed reactors
Authors: Hinduja M. J. , Sundaresan S. , Jackson R. 
Published: June 2004

AbstractA three‐parameter model of axial and radial dispersion in a packed tubular reactor is proposed as an alternative to the Fickian dispersion model. Though it is formulated in terms of differential equations, it requires no exit boundary condition, so it is mathematically more convenient than the Fickian model. Examples of its application to chemical reactors are given.
A Corresponding States equation for saturated liquid densities. I. Applications to LNG
Authors: Teja Amyn S. 
Published: June 2004

AbstractPresented here is a Corresponding States Method for predicting saturated liquid densities of both pure components and mixtures. The method is based on the known properties of two reference fluids and requires the critical properties and the acentric factor of the pure component(s) as input parameters. The method is tested for predicting the orthobaric densities of LNG mixtures using methane and n‐butane as the reference fluids. Very accurate prediction (well within the accuracy of the experimental data) are obtained for such mixtures using, at most, only one adjustable coefficient to characterize each binary system. The method is extremely simple to use and is suitable for design applications.
Modelling flow pattern transitions for steady upward gas‐liquid flow in vertical tubes
Authors: Taitel Yehuda , Barnea Dvora , Dukler A. E. 
Published: June 2004

AbstractModels for predicting flow pattern transitions during steady gas‐liquid flow in vertical tubes are developed, based on physical mechanisms suggested for each transition. These models incorporate the effect of fluid properties and pipe size and thus are largely free of the limitations of empirically based transition maps or correlations.
A channel flow analysis for porous beds moving under high G forces
Authors: Meyer J. W. 
Published: June 2004

AbstractAn analysis is made of centrifugal flow of compacted porous beds through channels against high gas backpressure. One‐dimensional compressible gas flow solutions are presented for concurrent and countercurrent solids/gas motion through the variable area channels. The physical process analyzed represents the flow through a newly developed centrifugal pump for feeding dry pulverized material against a pressure barrier. The objective of the analysis is to gain a basic theoretical understanding of this type of device. Good agreement is found between analytical predictions and test data obtained with an experimental pump feeding coal.
A cubic perturbed, hard sphere equation of state for thermodynamic properties and vapor‐liquid equilibrium calculations
Authors: Ishikawa Takeshi , Chung W. K. , Lu Benjamin C.‐Y. 
Published: June 2004

AbstractA cubic perturbed, hard sphere equation of state which combines the hard sphere expression of Scott and the empirical attractive term of Redlich and Kwong with two temperature dependent parameters has been successfully applied to the calculation of pure component properties and vapor‐liquid equilibrium values.
A random pore model for fluid‐solid reactions: I. Isothermal, kinetic control
Authors: Bhatia S. K. , Perlmutter D. D. 
Published: June 2004

AbstractFor fluid‐solid reactions, a random pore model is developed which allows for arbitrary pore size distributions in the reacting solid. The model can represent the behavior of a system that shows a maximum in reaction rate as well as one that does not, and it identifies an optimal pore structure for either of such systems. It is demonstrated that the new model subsumes several earlier treatments as special cases. By comparison with the grain model, a relationship is derived between the effective grain shape factor and a pore structure parameter defined here. When the variance of the pore size distribution is effectively zero, the new results approach those predicted by the Petersen (1957) model over a large range of conversions. The char gasification data of Hashimoto et al. (1979) are shown to produce correlations consistent with the expectations of the new model.
Application of corresponding states principles for prediction of self‐diffusion coefficients in liquids
Authors: Riazi Mohammad R. , Daubert Thomas E. 
Published: June 2004

AbstractA corresponding states approach has been used successfully to correlate reduced self‐diffusivity of pure liquids with reduced temperature and acentric factor. In addition, dimensional analysis techniques have been used to accurately relate viscosity, normal boiling point and temperature with self‐diffusivity, as well as to relate the three transport properties.
On the movement of multiple reaction zones in porous media
Authors: Hekim Yusuf , Fogler H. S. 
Published: June 2004

AbstractA distributed parameter model has been developed to describe flow and dissolution of different minerals in porous media. Asymptotic solutions are obtained to give the separation of the different mineral reaction fronts and the time for the reaction front to move through the porous core. The experimental observations agree well with theoretical predictions.
On the construction of dispersion approximations to the solution of the convective diffusion equation
Authors: DeGance Anthony E. , Johns Lewis E. 
Published: June 2004

AbstractWe identify dispersion approximations to the transverse average of the solution of the convective diffusion equation on exacting equality of a finite number of axial Hermite moments. The method unifies the dispersion of chemically active and passive solutes and generalizes dispersion theory to arbitrary transverse averages. We emphasize the importance of the scalar results via their application to the dispersion of a system of chemical isomers.
Oil ganglion dynamics during immiscible displacement: Model formulation
Authors: Payatakes A. C. , Ng K. M. , Flumerfelt R. W. 
Published: June 2004

AbstractA model is formulated in order to study the transient behavior of oil ganglion populations during immiscible displacement in oil recovery processes. The model is composed of three components: a suitable model for granular porous media; a stochastic simulation method capable of predicting the expected fate (mobilization, breakup, stranding) of solitary oil ganglia moving through granular porous media; and two coupled ganglion population balance equations, one applying to moving ganglia and the other to stranded ones. The porous medium model consists of a regular network of randomly sized unit cells of the constricted tube type. Based on this model and a mobilization‐breakup criterion, computer aided simulations provide probabilistic information concerning the fate of solitary oil ganglia. Such information is required in the ganglion population balance equations, the solution of which delineates the conditions under which oil bank formation suceeds or fails. Successful oil bank formation depends on the outcome of the competition between the process of oil ganglion deterioration through breakup and stranding on one hand and the process of oil ganglion collision and coalescence on the other. The parameters entering the system of population balances are initial ganglion number concentration, average ganglion velocity, ganglion dispersion coefficients, ganglion stranding coefficient, ganglion breakup coefficient and probability of coalescence given a collision. These parameters are, in turn, functions of the porous medium geometry, capillary number, ganglion size distribution, flood velocity, oil saturation and flood composition.
Dendritic deposition of aerosols by convective Brownian diffusion for small, intermediate and high particle Knudsen numbers
Authors: Payatakes A. C. , Gradoń L. 
Published: June 2004

AbstractWhen an aerocolloidal suspension flows through a fibrous filter, particles deposit on the fibers and form dendrites. Similar phenomena are observed with collectors other than fibers, provided that the characteristic dimension of the collector does not exceed that of the particles by more than one to two orders of magnitude. This deposition pattern leads to marked increases in capture efficiency and pressure drop, as particles accumulate within the filter. In previous publications, theoretical models of this process were developed for the cases of deposition by interception alone and of deposition by combined inertial impaction and interception. Consequently, those works apply to aerosol particles with diameters of 1 μm or larger. Here we extend the model to the case of submicron particles, where the main transport mechanism is Brownian diffusion. To keep things specific, we consider fine fibers as collectors, but the model can be easily converted to other geometries. We present solutions for the cases of nonslip flow around the fiber and nonslip, slip and free molecular flow around particles. Unlike deposition by inertial impaction and/or interception, convective Brownian diffusion forms dendrites over the entire fiber surface.
On the concentration dependence of diffusion coefficients in zeolites
Authors: Gelbin D. , Fiedler K. 
Published: June 2004

AbstractRuthven (1976) published thermodynamic and kinetic data on the adsorption of five gases in zeolites over a wide range of temperatures and concentrations. We have described zeolite diffusivities with a model based on the discrete structure of zeolite crystals and a statistic‐thermodynamic evaluation of equilibrium measurements (Fiedler and Celbin 1978). Prof. Ruthven has kindly sent us tables of results for all systems in his paper, which we analyze below.
Sulfur dioxide transport through aqueous solutions: Part I. Theory
Authors: Roberts Daryl L. , Friedlander Sheldon K. 
Published: June 2004

AbstractExpressions are derived for the steady state flux of sulfur dioxide through films of water and neutral and alkaline salt solutions. A local equilibrium approximation yields and analytical expression for the flux through water and neutral salt solutions. To account for deviations from local equilibrium, the conversion from sulfur dixoxide (aq) to sulfur containing ions (and vice versa) is assumed frozen near the boundaries of the film (x = 0, x = 1). The thickness of the boundary layer near x = 1 is pH dependent, indicating an increasing deviation from equilibrium flux in increasingly alkaline solutions. Strong nonequilibrium behavior can be realized under some conditions for a film of concentrated sodium hydroxide operating as a liquid membrane and in conventional scrubbers.
Aerosol behavior in the continuous stirred tank reactor
Authors: Crump James G. , Seinfeld John H. 
Published: June 2004

AbstractThe basic features of aerosol behavior in the CSTR are examined. Solutions are obtained for the steady state aerosol size distribution during simultaneous coagulation, particle growth by vapor condensation and new particle formation by nucleation. Explicit distributions are shown for the case of a monodisperse feed aerosol.