bluuebunny/crossref_metadata_2025 huggingface dataset:
A four‐parameter corresponding states theory: Saturated liquid densities of anormal fluids
Authors: Bhirud Vasant L.
Published: June 2004

A fourth parameter to be used in conjunction with Pitzer's acentric factor is proposed to correlate the thermophysical properties of anormal fluids. It is based on the saturated liquid density at a reduced temperature of 0.7. A correlation for saturated liquid densities of anormal fluids is presented to cover a reduced temperature range from 0.42 to 1.0. For four hundred and fifty‐six data points, covering twenty‐one compounds, calculated average and average absolute deviation in predicted saturated liquid densities are −0.05 and 1.11%, respectively.
Catalytic hydrogenation of cyclohexene: Part II. Liquid phase reaction on supported platinum in a gradientless slurry reactor
Authors: Madon R. J. , O'Connell J. P. , Boudart Michel
Published: June 2004

The areal rate of liquid phase hydrogenation of cyclohexene on supported platinum catalysts does not depend on the nature of the support. Nor does it depend on particle size of the metal. The rate constant is independent of the nature of the solvent when the concentration of hydrogen in it is expressed as its measured or calculated solubility. All observations are compatible with the idea that the measured rate is that of chemisorption of dihydrogen on a metal surface covered with reactive hydrocarbon intermediates.
Hydrocarbon separation through a liquid water membrane: Modeling of permeation in an emulsion drop
Authors: Casamatta Gilbert , Chavarie Claude , Angelino Henri
Published: June 2004

The mass transfer of hydrocarbons within an emulsion drop has been modeled. The selective behavior of the process is attributed to the controlling effect of the aqueous phase; calculations show that the presence of a very thin membrane of water separating the inner core of the hydrocarbon droplets from the surrounding solvent is sufficient to explain observed selectivities.
On dynamical methods of heat integration design
Authors: Georgakis Christos , Worthey David J.
Published: June 2004

Perturbation theory is utilized in order to examine the change in stability characteristics due to heat integration between process units. Dynamical rules of design are obtained in order to select the unit integrations with the most desirable stability characteristics. The integration of nonisothermal CSTR's with endothermic and exothermic reactions is examined in detail. It is shown that heat integration can make the endothermic reactor more stable if it increases the slope of the heat removal line for this reactor. On the other hand, the stability of exothermic reactors tends to increase when heat integration moves the slope of the heat removal line for this reactor closer to a characteristic value. Approximate values are also calculated for the critical amount of heat integration which makes the system unstable.
Drop coalescence in liquid‐liquid fluidized beds
Authors: Ramamoorthy Periaswamy , Treybal Robert E.
Published: June 2004

A drop size segregation technique leads to a direct measurement of the interdrop coalescence frequencies of equisized droplet swarms in liquid‐liquid fluidized beds. Mass transfer between the phases and the use of a tracer dye are avoided. The study includes the effects of highly viscous continuous as well as dispersed phases. Binary liquid solutions of ethylene glycol and distilled water provided aqueous phases of increasing viscosity, and toluene was the second liquid phase. Twenty two liquid‐liquid systems including other dispersed liquids, namely, benzene, ethyl acetate, cyclohexane, and carbon tetrachloride, were studied by this technique.

In the case of toluene continuous, the drops of water dispersed in toluene were large in size, and they coalesced at unusually high rates up to about 100 times faster than those of toluene dispersed in water. Similarly, anhydrous ethylene glycol dispersed in toluene showed somewhat high coalescence frequencies. All the data excluding these two anomalous systems were analyzed by a stepwise regression technique to yield the best fitting correlation in terms of the most significant dimensionless ratios.

For the present, the proposed empirical correlation for the dimensionless parameter [ωD× 105/Vs] containing the coalescence frequency (ω, time−1) as a function of the coalescence number (σ/μcVs) and the viscosity ratio (μd/μc) is as follows:.
Immobilization of glucose isomerase to cellulose
Authors: Sirotti David A. , Emery Alden
Published: June 2004

Glucose isomerase was covalently bonded to Solka‐floc and DEAE cellulose by several techniques. The best results were obtained with techniques that opened the crystalline structure of the cellulose and kept it that way during immobilization. The most active catalyst was prepared by mercerizing Solka‐floc, cross‐linking it in that expanded configuration with epoxides, and immobilizing the enzyme with cyanogen bromide. The second most active catalyst was made using DEAE cellulose and a mixture of di and tri‐epoxides as immobilization reagent.

The practical consequences of the results were tested by designing reactors to produce high fructose syrup using the activity and stability of several of the preparations. Since the activity decays with time, equations were developed to give the optimum time of running before the catalyst was discarded. The most promising one was the second most active; the most active catalyst yielded a production cost three times as great because of the large quantities of cyanogen bromide needed.
Semiempirical theory of surface tensions of pure normal alkanes and alcohols
Authors: Carey B. S. , Scriven L. E. , Davis H. T.
Published: June 2004

A comparison of experimental and theoretical surface tensions leads to a correlation between homogeneous fluid parameters and the inhomogeneous influence parameter c. From this correlation, it is possible to predict, to within excellent agreement with experiment, the surface tensions of normal alkanes and alcohols from bulk data only.
Molecular diffusion in polymer solutions
Authors: Vrentas James S. , Duda J. Larry
Published: June 2004

Methods for estimating mutual diffusion coefficients for polymer‐solvent systems are reviewed. Procedures are recommended for the determination of the temperature, concentration, and molecular weight dependences of diffusivities both for dilute and concentrated solutions.
Applications of a stretch model to mixing, diffusion, and reaction in laminar and turbulent flows
Authors: Ranz William E.
Published: June 2004

In a Lagrangian frame of reference based on lamina (fluid filament) thickness and in a warped time scale based on a single, flow dependent quantity, mixing, diffusion, and reaction can be described in a relatively simple way. Applications are presented for stretch and fold in taffy pull, egg beater and static mixer, shear stretch, stretch of laminae in a vortex, mixing with diffusion, reaction rate controlled by diffusion of reactant through a product layer, and very fast reactions in a turbulent flow.
Effect of flow maldistribution on conversion and selectivity in radial flow fixed‐bed reactors
Authors: Ponzi Peter R. , Kaye Larry A.
Published: June 2004

This paper examines the effect of flow maldistribution on the predicted conversion and selectivity in a radial flow fixed‐bed reactor. A simple model was developed to relate gas maldistribution to the catalyst bed to the conversion with first‐ and second‐order reactions and to selectivity for first‐order reactions in series and parallel. For the cases considered, the conversion debit due to maldistribution of the gas phase was as much as 11%. The model was extended to cover adiabatic conditions for simple first‐order reactions. For an exothermic reaction, maldistributions can enhance conversion over that obtained with a uniformly distributed gas phase.
Mass transfer in regular arrays of hollow fibers in countercurrent dialysis
Authors: Noda Isao , Gryte Carl C.
Published: June 2004

The concentration profiles in a countercurrent hollow fiber bundle mass exchanger dialyzer is derived, assuming a uniform distribution of fibers in the dialyzer shell. Mass transfer coefficients are obtained as a function of fiber packing density, membrane thickness, membrane material, and solute type.
Gas absorption by a liquid layer flowing on the wall of a pipe
Authors: Henstock William H. , Hanratty Thomas J.
Published: June 2004

A method is presented for predicting absorption rates for liquid layers flowing along a wall. It is based on results presently available in the literature as well as on the results of studies we recently carried out on the rate of oxygen absorption from a flowing air stream into water layers on the bottom of a horizontal enclosed channel and on the inside of a vertical pipe. Absorption measurements can be interpreted by assuming that the process is controlled by eddies whose length and velocity are characterized by bulk turbulence properties and that in a region of thickness δ close to the interface the turbulence is dampened by viscosity.
Residence time distributions of paper pulp slurries in vertical laminar flow
Authors: Moreira R. M. , Felder R. M.
Published: June 2004

The hydrodynamic behavior of paper pulp slurries in vertical laminar flow has been observed and modeled. Radiotracers were used to tag both the liquid and solid phases of slurries flowing in 4 and 30 cm pipes. Residence time distributions were determined for each phase and were used to derive and compare several flow models. A model consisting of a central core in plug flow circumscribed by a clear Newtonian annulus provides a good representation of the observed slurry behavior. Correlations between the model parameters and the Reynolds number and slurry consistency are presented, and implications of the results on the design of slurry flow reactors are discussed.
Properties of recirculating turbulent two phase flow in gas bubble columns
Authors: Ueyama Korekazu , Miyauchi Terukatsu
Published: June 2004

The equation of motion for the two phase flow within a bubble column, operated within the recirculation flow regime, has been solved, and the profile of liquid flow has been determined. Nicklin's relation for the bubble flow regime has been extended to the recirculation flow regime.

Data analysis shows that the mean slip velocity between bubble and liquid is approximately constant and that the kinematic turbulent viscosity increases rapidly with increasing diameter of the column. These observations lead to the conclusion that scale‐up has but little influence upon the mean gas holdup.
Interfacial effects in the displacement of residual oil by foam
Authors: Slattery John C.
Published: June 2004

A qualitative theory is developed to explain the roles of surface tension and the two surface viscosities in the displacement of foams through porous media. There is a critical value of the surface tension above which a foam cannot be displaced under a given pressure gradient. The displacement efficiency of a foam can be raised by increasing the surface tension to only slightly less than this critical value, by increasing the viscosity of the aqueous surfactant solution from which the foam is formed and by increasing the surface viscosities. These predictions are in agreement with available experimental data.
Continuous fractionation of protein mixtures by p H parametric pumping: Experiment
Authors: Chen H. T. , Wong Y. W. , Wu S.
Published: June 2004

Continuous pH parametric pumping separations of a haemoglobin‐albumin‐CM Sepharose system were experimentally investigated. The parapump has a feed containing the protein mixture to be separated, introduced alternately to the top and bottom of the chromatographic column. The top and bottom products are withdrawn from the apparatus, respectively, during the bottom and top feed. It is shown that under certain conditions the pH driven parametric pump has the capacity for removal of protein components from one product fraction and large enrichment in the other fraction. Moreover, the continuous process can be operated with a large feed throughput.
Residence time distributions in a plasticating twin screw extruder
Authors: Janssen L. P. B. M. , Hollander R. W. , Spoor M. W. , Smith John M.
Published: June 2004

Residence time distribution measurements in a twin screw extruder are compared with a model based on ideally mixed chambers. Special attention is given to the tail of the distribution. These measurements are compared with the residence time distributions in single screw extruders and an empty pipe.
Transient behavior of moving‐bed coal gasification reactors
Authors: Yoon Heeyoung , Wei James , Denn Morton M.
Published: June 2004

The transient response of dry ash and slagging moving‐bed coal gasification reactors is analyzed for small step changes in feed conditions. The approach to the new steady state for perturbations about the optimum in the Lurgi gasifier has a time scale of about 10 hr. Transients in the slagging gasifier can result in a decrease in the coal bed height, which occurs on a time scale of several hours. There is a rapid initial response in both types of reactors in product gas temperature and heating value.
A Study of disaggregation effects in sedimentation
Authors: Adler P. M.
Published: June 2004

Aggregates are considered as a porous medium. Stresses within the porous solid matrix are calculated when the particle deformation is ignored. The maximum size of the aggregates is derived from a yield condition, and the settling velocity is deduced. The influence of the mechanical properties and concentration of the aggregates are detailed and discussed.
Quantitative interpretation of phase volume behavior of multicomponent systems near critical points
Authors: Fleming Paul D. , Vinatieri James E.
Published: June 2004

Equations describing phase volumes in multicomponent, multiphase systems in the neighborhood of critical points are derived to aid in the location of such critical points. The theory is in good agreement with experiments for three ternary systems and four surfactant systems of the type used for tertiary oil recovery.
Mixing with helical ribbon agitators: Part III. Non‐Newtonian fluids
Authors: Yap C. Y. , Patterson W. Ian , Carreau P. J.
Published: June 2004

The use of helical ribbon agitators to mix viscous non‐Newtonian fluids has been investigated. A generalized model, based on an appropriate definition of effective viscosity, is proposed to predict power consumption. This model is most successful with fluids that do not have a high degree of elasticity.

It was found that the efficiency of mixing of pseudoplastic fluids was about half of that of Newtonian fluids in the same mixer, while the efficiency of mixing viscoelastic fluids was still lower and approximately independent of the mixer geometry. Blade width was the primary variable affecting the mixing efficiency on inelastic fluids.
Vapor‐liquid equilibrium. Part VI. Standard state fugacities for supercritical components
Authors: Van Ness H. C. , Abbott M. M.
Published: June 2004

A general treatment of fugacities of liquid mixtures yields the proper thermodynamic functions for dealing with nonidealities of liquid phases in equilibrium with vapor mixtures for systems containing supercritical components. The activity coefficients of the supercritical components may be based on standard state fugacities for the hypothetical pure liquids or on Henry's constants. A comparison of the rigorous thermodynamic equations which apply to the liquid phase for the two alternatives shows that they are equivalent.
A new correlation for saturated densities of liquids and their mixtures
Authors: Hankinson Risdon W. , Thomson George H.
Published: June 2004

A new correlation has been developed for the densities of saturated liquids and their mixtures. The correlation is relatively easy to use and is applicable to a wide variety of liquids. The saturated liquid density correlation is flexible and consistent and requires only reduced temperature, acentric factor, and a characteristic volume for each pure compound. Mixing rules are given. When tested against a data base of 2 657 points of pure compound liquid density data for 97 hydrocarbons and 1 851 points for 103 other compounds, the new correlation gave an average absolute error of 0.37% compared to 2.14% for the Yen‐Woods correlation and 0.50% for the SDR equation as modified by Spencer and Danner. For 2 994 points of liquid mixture density data for 167 mixtures, the new correlation gave an average absolute error of 1.40% compared to 5.64% for the Yen‐Woods correlation and 2.95% for the SDR equation. Characteristic volumes are listed for 200 compounds; they are generalized as functions of acentric factor for various types of compounds and are compared to critical volumes.
Theoretical prediction of effective heat transfer parameters in packed beds
Authors: Dixon Anthony G. , Cresswell David L.
Published: June 2004

A theory for predicting the effective axial and radial thermal conductivities and the apparent wall heat transfer coefficient for fluid flow through packed beds is derived from a two‐phase continuum model containing the essential underlying and independently measurable heat transfer processes. The theory is shown to explain much of the confused literature and pinpoints the remaining major areas of uncertainty, further investigation of which is needed before secure prediction is possible.
Stability of dissolving or depositing surfaces
Authors: Thorsness C. B. , Hanratty Thomas J.
Published: June 2004

In 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

A 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

The 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

A 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

This 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

Three 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

Secondary 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

For 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

A 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

A 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

Simulation 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

Intraparticle 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

This 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

A 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

Presented 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

Models 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

An 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

A 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

For 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

A 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

A 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

We 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

A 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

When 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

Ruthven (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

Expressions 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

The 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.
Volatiles loss during atomization in spray drying
Authors: Kieckbusch Theo G. , King C. J.
Published: June 2004

Losses of volatile acetates have been measured in the vicinity of pressure nozzles during spraying of sucrose and maltodextrin solutions. Large losses occur very near the atomizer, where only a small portion of the water has evaporated. The effects of atomizer design, nozzle pressure, sucrose concentration, air flow rate, air temperature and liquid feed temperature have all been measured. Correlation of volatiles loss vs. percent water evaporation accounts for most of the effects of changes in spray pattern and drop size distribution. Individual contributions of gas and liquid phase mass transfer are determined from the relative retentions of acetates of different molecular weight and from the effect of sucrose concentration. In the expanding film at the nozzle, both gas and liquid phase resistances are important, but the losses become entirely liquid phase controlled once drops are formed.
Heat transfer from two‐phase boundary layers on isothermal cylinder: Influence of drop trajectory
Authors: Lu Christopher C. , Heyt John W.
Published: June 2004

The influence of drop trajectories on boundary layer structure and heat transfer coefficient is determined for a binary spray flow over the upstream surface of an isothermal cylinder. Governing equations are solved for drop trajectories upstream of the cylinder, the laminar liquid boundary layer adjacent to the cylinder surface, and the outer laminar vapor boundary layer. Velocity, temperature, and mass concentration profiles throughout the double boundary layers are shown to depend on flow parameters involving drop size and velocity. The critical conditions for which the liquid film dries out are identified for a range of drop size and velocity, defining the transition from the liquid film to the dry wall flow regime. Theoretical results for heat transfer are shown to correlate existing experimental data.
The extended Graetz problem with prescribed wall flux
Authors: Papoutsakis Eleftherios , Ramkrishna Doraiswami , Lim Henry C.
Published: June 2004

An analytical solution is obtained to the extended Graetz problem with prescribed wall flux, based on a selfadjoint formalism resulting from a decomposition of the convective diffusion equation into a pair of first‐order partial differential equations. The solution obtained is simple, computationally efficient and in striking contrast with incomplete numerical efforts in the past.
Transport phenomena in solids with bidispersed pores
Authors: Neogi P. , Ruckenstein E.
Published: June 2004

Existing analyses for transport phenomena in bidisperse porous media assume that the microparticles act as uniformly distributed point sinks. This article provides an analysis which determines under what conditions the point sink approximation is valid. For random packing, the concentration field inside a pellet is described by its ensemble average, i.e., the average over all possible ways in which the microparticles can be packed into the pellet. For these averaged quantities, we formulate the transport equations for a solid with bidisperse pores which provide the criteria of validity of the point sink approximation.
Permeation cascades for the separation of krypton and xenon from nuclear reactor atmospheres
Authors: Stern S. A. , Wang S.‐C.
Published: June 2004

Multistage permeation cascades have been designed for the removal of radioactive krypton and xenon from nuclear reactor atmospheres. These cascades could serve for the decontamination of the atmosphere within a reactor containment dome following a nuclear accident and for other applications of interest to the nuclear industry. The stages of the cascades are assumed to consist of permeator modules using silicone rubber capillaries as separation membranes. All stages are to be operated in a countercurrent mode with shell‐side feed.

It is shown that it is possible to design an ideal cascade for the separation of multicomponent mixtures by matching the concentrations of a suitable key component in interstage streams that are mixed. This procedure minimizes the cascade volume and power requirement. It is also possible to design a cascade with constant stage cuts in its enriching and stripping sections that approximates the performance of an ideal cascade. The krypton and xenon content of a feed mixture containing about 1 × 10−3 mol% Kr and 1 × 10−2 mol% Xe in air can be lowered by factors of 103 and 108 respectively in a 27‐stage permeation cascade. Methods of reducing the number of stages and the effects of irradiation on the membrane performance are also discussed.
Mathematical modeling of catalytic converter lightoff: Single‐pellet studies
Authors: Oh Se H. , Cavendish James C. , Hegedus L. Louis
Published: June 2004

A detailed mathematical model of a single catalyst pellet has been developed to describe its behavior under transient conditions encountered during the warmup period of automobile exhaust catalytic converters. In contrast to the converter models previously reported in the literature, this model is capable of describing the time‐dependent behavior of a composite catalyst pellet, and thus provides a convenient means of examining the effects of poison penetration and various noble metal impregnation strategies in the activity‐time (rather than activity‐temperature) domain.

Extensive calculations were carried out to investigate the effects of various catalyst design parameters and converter operating conditions on the lightoff behavior of a spherical, platinum‐alumina catalyst pellet. Due to the complex kinetics of the CO and hydrocarbon oxidation reactions, catalyst lightoff was found to exhibit interesting behavior with respect to variations of the system's design parameters and operating conditions. Graphs are presented to illustrate the parameteric sensitivity of these effects.
Modeling pulverized coal conversion in entrained flows
Authors: Sprouse K. M.
Published: June 2004

A detailed description of pulverized coal conversion in one‐dimensional entrained flows has been formulated and correlated to hydrogasification data from the Rockwell International Flash Hydropyrolysis (FHP) reactor using bituminous coals. This analysis contains physical and chemical descriptions which have not been included in previous mathematical models. These descriptions provide further important insights into the nature of entrained flow coal gasification.
Photo‐assisted heterogeneous catalysis with optical fibers II. Nonisothermal single fiber and fiber bundle
Authors: Marinangeli R. E. , Ollis D. F.
Published: June 2004

A previous paper (Marinangeli and Ollis, 1977) considered light transport in a single optical fiber which was coated with a heterogeneous photoassisted catalyst. This paper analyzes simultaneous mass, heat, and light transport in a catalyst on a single fiber, and in a likely large‐scale configuration, a bundle of parallel, catalyst‐coated optical fibers. The dimensionless temperature rise is dominated by energy released by light absorption, with the heat of reaction contributing to a lesser degree.