bluuebunny/crossref_metadata_2025 huggingface dataset:
Prediction of transport processes within porous media: Creeping flow relative to a fixed swarm of spherical particles
Authors: Neale Graham H. , Nader Walter K.
Published: June 2004

A geometric model for an homogeneous swarm of spherical particles was introduced by us in an earlier paper and successfully employed in a theoretical investigation of diffusive transport processes occurring therein.

The same geometric model is used here in a theoretical study of the hydrodynamic transport process occurring within a fixed swarm of spherical particles. The product of the application of this model to the problem of incompressible, creeping fluid flow within an homogeneous swarm of impermeable spherical particles may be regarded as a logical extension of the well‐known Brinkman model; it permits physical representation and rigorous mathematical solution, yielding predictions which are in good agreement with experimental data throughout the entire porosity range. For porosities in excess of 0.7, the predictions agree closely with those obtained by means of Happel's free surface model.
Studies of coalescence and phase separation in thick dispersion bands
Authors: Allak A. M. A. , Jeffreys G. V.
Published: June 2004

A refractive index matching technique has been developed to study the behavior and coalescence phenomena of drops in closely packed dispersion bands. The frequency of drop‐drop coalescence has been measured and correlated, and a mathematical model, based on film rupture thickness, has been written for solution by computer to predict dispersion band thickness as a function of inlet drop size, flow rate, and the physical properties of the system.
Friction modification in a coupled system
Authors: Peters L. K. , Bender D. W. , Klinzing G. E.
Published: June 2004

Two‐phase solids‐in‐air flow was experimentally studied in a once through flexible wall tube flow system using nominal 25μm and 50μm spherical glass beads. For turbulent flow through the Silastic tube without a damping medium behind the wall, cases of true drag reduction and no drag reduction were found. The rate of addition of the glass beads was seen to be a correlatable parameter for both the flexible and rigid wall systems. A mechanistic model is proposed for interpretation of the results. It was qualitatively observed that the presence of an electrostatic charge on the particles at low relative humidities had a pronounced effect on increasing the drag in the system.
Pressure drop and holdup in stratified gas‐liquid flow
Authors: Russell T. W. F. , Etchells A. W. , Jensen R. H. , Arruda P. J.
Published: June 2004

A mathematical model and an iterative procedure to calculate holdup and pressure drop in horizontal gas‐liquid flow is developed. The predictions of the model agree with well over a hundred data points collected with air‐water and air‐glycerine solutions in 0.0254‐, 0.0381‐, and 0.0508‐m. diameter pilot pipelines. A design procedure using the verified model is presented.
Gas absorption by non‐Newtonian fluids in agitated vessels
Authors: Perez Jerome F. , Sandall Orville C.
Published: June 2004

Carbon dioxide was absorbed by aqueous Carbopol solutions in a turbine‐agitated vessel for the cases of absorption across an unbroken interface and absorption with the gas bubbling through the liquid. The rheological behavior of the solutions was described by the non‐Newtonian power law model with flow behavior indices varying from 0.92 to 0.59. An effective viscosity technique which had previously been developed to correlate agitated vessel rates of viscous dissipation and heat transfer with power law pseudoplastic fluids was used to correlate the data.
Effect of mass transfer on laminar jet breakup: Part I. Liquid jets in gases
Authors: Burkholder Harry C. , Berg John C.
Published: June 2004

The instability and breakup of laminar liquid jets in gaseous surroundings is investigated for conditions under which a solute is transferring across the jet interface rendering the system susceptible to Marangoni convection. Linear hydrodynamic stability analysis reveals that solute transfer out of the jet is stabilizing (produces longer jets) while transfer into the jet is destabilizing and promotes breakup. Solute adsorption, including as a limiting case the presence of a spread surfactant monolayer, may strongly counteract the stabilizing or destabilizing effects of mass transfer but has only a negligible effect on jet stability in the absence of interphase mass transfer. Qualitative experimental results for water jets in air with acetone as the transferring solute corroborate both the stabilizing and destabilizing mass transfer effects predicted by the theory.
Fixed bed desorption behavior of gases with nonlinear equilibria: Part II. Dilute, multicomponent, isothermal systems
Authors: Zwiebel Imre , Kralik Christopher M. , Schnitzer Jay J.
Published: June 2004

Generalized depletion curves for desorption (and Corresponding breakthrough curves for adsorption) were calculated for systems characterized by the Langmuir‐type multicomponent equilibrium equation and controlled by the film type rate model. In contrast with adsorption where the nonkey (or less strongly adsorbed) component curves display overshoots above feed concentration, in desorption the key component depletion curves exhibit the instabilities in the form of inflections and curvatures. As in the one component case, the differences in the depletion and breakthrough curves may be related to the rate phenomena. The undulations in the key component depletion curves may be characterized by derivatives of the rate data. The major significance of these instabilities is to elongate the depletion curves, which in turn requires the expenditure of added effort during regeneration. Process modifications are indicated, which could suppress the instabilities. The predicted trends were confirmed by experimental depletion curves.
Experimental investigation of polarization effects in reverse osmosis
Authors: Johnson A. R.
Published: June 2004

With a Mach‐Zehnder interferometer, salt concentration profiles were measured in a reverse osmosis system under natural convection with the membrane in a vertical position. The measured concentration profiles compared favorably with those predicted theoretically as long as the motion remained laminar. At large distances from the leading edge, however, the flow developed a wavy pattern, especially for bulk salt concentrations in excess of 0.1 moles/liter. As expected, whenever this motion became especially pronounced, the concentration of salt at the membrane surface was less and the production rate of fresh water greater than that predicted using the laminar analysis.
Co‐rotational rheological models and the Goddard expansion
Authors: Bird R. Byron , Hassager Ole , Abdel‐Khalik S. I.
Published: June 2004

A survey is given of co‐rotational rheological equations suitable for describing the flow of viscoelastic liquids such as polymer solutions and melts. Comparisons are given with experimental data and molecular theories. An introduction to kinematical descriptions in co‐rotating reference frames is included.
Dynamic meniscus profiles in free coating III predictions based on two‐dimensional flow fields
Authors: Lee Chie Y. , Tallmadge John A.
Published: June 2004

One challenging problem in liquid‐gas, interfacial phenomena is the prediction of the size and location of a flowing meniscus because it involves surfaces which are highly curved. The paper presents one aspect of this problem. A numerical method is presented for predicting the dynamic meniscus profiles–specifically these distorted considerably by flow. The geometry considered to provide those free (liquid‐gas) surfaces is coating of a moving sheet by upward withdrawal from a finite bath. The predicted profiles agree with data taken with a glycerine‐water solution and with viscous oils.

The method predicts the three parameters (coating thickness and two others) which are the minimum number of parameters necessary to describe the dynamic‐meniscus profiles for this geometry. The numerical method is iterative, it simultaneously predicts the flow field in the bath, and it is based on the two‐dimensional Navier‐Stokes equations and appropriate boundary conditions. The interfacial boundary condition used for iteration is the normal stress condition which is composed of pressure, surface tension, and viscous terms.
Developing and fully developed velocity profiles for inelastic power law fluids in an annulus
Authors: Tiu Carlos , Bhattacharyya Satinath
Published: June 2004

Developing and fully developed velocity profiles with respect to position for laminar flow of inelastic fluids in an annulus were measured using streak photography. The polymer solutions used in the investigation were found to exhibit power law behavior under the present experimental conditions. The experimental results substantiated published theoretical solutions for developing and fully developed flow of power‐law fluids in annuli, and also indicated good agreement between the measured and predicted entrance lengths. The dimensionless entrance length was found to increase with increasing flow behavior index for the inelastic power‐law fluids.
Distribution coefficients at high dilution for organic solutes between water and isobutane or isobutylene
Authors: Won K. W. , Prausnitz J. M.
Published: June 2004

To facilitate design of an extraction process for removal of organic solutes from petroleum and petrochemical waste streams distribution‐coefficient date were obtained for typical organic pollutants at high dilution. Volatile solvents were chosen because of their low solubility in water and because they are recovered easily. Samples form both the aqueous and the organic phase were analyzed chromatographically. To remove a sample from an equilibrium cell operating at ressures well above atmospheric, a special technique was developed using low‐melting Indalloy for micro‐encapsulation.

Distribution coefficients at ambient temperature are given for a variety of solutes, including esters, phenolics, ketones, and aldehydes. The results are correlated by a simple relation based on perturbed‐hard‐sphere theory for dilute solutions. Isobutane or isobutylene may be particularly useful in a dual‐solvent extraction process wherein a polar organic solvent is used in a secondary extraction tod remove the polar solvent from water.
Legendre transforms and their application in thermodynamics
Authors: Beegle Bruce L. , Modell Michael , Reid Robert C.
Published: June 2004

Legendre transform theory is: (1) developed to show the relationships among the common thermodynamic potential functions (that is, energy, enthalpy, and free energy); (2) extended to introduce other potential functions which are particularly convenient in certain applications (for example, stability and critical point phenomena of multicomponent systems). General derivative operators are employed to allow partial derivatives of a given potential functions to be transformed to derivatives of other potential functions.
Thermodynamic stability criterion for pure substances and mixtures
Authors: Beegle Bruce L. , Modell Michael , Reid Robert C.
Published: June 2004

Criteria are derived to specify the limit of stability for pure material and multicomponent thermodynamic systems. Through the use of Legendre transforms, the criteria may be expressed in a very simple form that only involves the determination of positiveness of a single second‐order partial derivative of a potential function. Alternate and equivalent criteria are shown to result from a simple reordering of the independent variables in the Fundamental Equation of Gibbs. Certain criteria that are often stated as necessary conditions of stability (for example, Cv > 0) are shown to be insufficient for specifying the limit of stability; that is, a system will always become unstable for other reasons before Cb can attain a negative value.
Estimation of bubble diameter in gaseous fluidized beds
Authors: Mori S. , Wen C. Y.
Published: June 2004

Bubble size is one of the most important parameters in the design and simulation of a fluidized‐bed reactor.

A correlation of the bubble size and growth in fluidized beds of various diameters is developed. A maximum bubble diameter determined from the bubble coalescence is incorporated in the correlation to relate the effect of the bed diameter on the bubble size.

Experimental data of bubble size reported are used to develop and test the validity of the correlation. The bubble diameters calculated using this correlation show good agreement with the observed bubble diameters.
Some fundamental aspects of spray drying
Authors: Katta S. , Gauvin W. H.
Published: June 2004

Equations are proposed to predict the three‐dimensional motion of droplets in a spray dryer, based on a knowledge of the characteristics of the atomizing device and of the gas flow patterns in the drying chamber. If the droplet size distribution produced by the atomizing device is known or can be assumed, the trajectories of the droplets can be calculated throughout the drying process and hence the evaporative capacity and thermal efficiency of the spray dryer can be predicted.

Experimental verification of this theoretical approach was obtained from a study of the drying of calcium lignosulfonate solutions of various concentrations in a 122‐cm diam. × 183‐cm high laboratory circular concurrent chamber with a conical bottom where the drying air was introduced tangentially near the top.

An experimental study of the effects of a number of operating variables on the capacity and the efficiency of the spray dryer was also carried out. These effects were interpreted in terms of the droplet trajectories obtained in each case.
Mathematical modeling of atomizing scrubbers
Authors: Taheri Mansoor , Sheih Ching Ming
Published: June 2004

A mathematical model for predicting particle collection efficiency in an atomizing scrubber has been developed. The model solves the diffusion equations for both droplets and particles by using particle in cell technique. The effect of scrubber size and water distribution from various points of injection have been studied on collection efficiency. The results of the mathematical prediction agrees very well with the data reported in the literature for a wide variety of operating conditions and configurations.
Inception criteria for droplet entrainment in two‐phase concurrent film flow
Authors: Ishii M. , Grolmes M. A.
Published: June 2004

Inception criteria for droplet entrainment in concurrent gas‐liquid film flow were developed from simple physical models. For film Reynolds number ≳ 160, an entrainment model based on the shearing off of roll‐wave crests was used. At lower film Reynolds numbers, a wave undercutting mechanism was introduced. Experimentally observed abrupt changes in the critical gas velocity corresponding to the onset of entrainment at a certain film Reynolds number have been explained by the shift in the entrainment mechanisms. An agreement of the present inception criteria with various experimental data is shown to be satisfactory, and significant improvements over the existing empirical correlations have been made.
Freeze dehydration by microwave energy: Part II. Experimental study
Authors: Ma Yi Hua , Peltre Philippe R.
Published: June 2004

Experimental drying curves have been obtained for the freeze‐dehydration of beef meat with microwave energy at 2450 MHz. In particular, experiments conducted with slabs of raw beef meat approximately 1.5 cm thick show that total drying times of less than 6 hr. can be obtained. Further drying time reductions are possible if microwave heating and freezing techniques are improved. Samples can be dried slightly faster at a higher pressure (for example, 1 mmHg) than at a lower pressure (for example, 0.2 mmHg) for the same microwave power input. However, melt back and vaporization occur if the pressure or the microwave power input is too high.

Comparison of the experimental drying curves with those predicted by the theory shows a reasonable agreement which, at least in part, verifies the validity of the previously derived mathematical model.
A generalized thermodynamic correlation based on three‐parameter corresponding states
Authors: Lee Byung Ik , Kesler Michael G.
Published: June 2004

The volumetric and thermodynamic functions correlated by Pitzer and co‐workers analytically represented with improved accuracy by a modified BWR equation of state. The representation provides a smooth transition between the original tables of Pitzer et al. and more recent extensions to lower temperatures. It is in a form particularly convenient for computer use.
Convergence promotion in the simulation of chemical processes—the general dominant eigenvalue method
Authors: Crowe C. M. , Nishio M.
Published: June 2004

The objective of this study was to devise an improved method of accelerating the iterative computation of steady state simulations of chemical processes. An extension of the dominant eigenvalue method is presented and its effectiveness is tested with simulations of chemical processes. The method is compared to previously available methods and is found to achieve convergence more rapidly and indeed was effective in cases where some other methods were ineffective or did not take a promotion step at all. The proposed method is applicable to the acceleration of any iterative computation of a nonlinear fixed‐point problem.
The behavior of a power‐law fluid flowing through a sudden expansion: Part I. A numerical solution
Authors: Halmos A. L. , Boger D. V. , Cabelli A.
Published: June 2004

A numerical solution for the axisymmetric flow of an inelastic power‐law fluid through an abrupt circular expansion is presented. The equations of motion were solved using an Alternating Direction Implicit method. Both a stream tube‐real tube and a real tube‐real tube model were investigated and the conditions for significant upstream diffusion of momentum were specified. Secondary flow characteristics and the bulk flow field development are predicted as a function of the flow behavior index (n) and of the Reynolds number. Some results are presented to show the influence of the expansion ratio.
Transport of mass in ternary liquid‐liquid systems. Part I. Diffusion studies
Authors: Sethy Anil , Cullinan Harry T.
Published: June 2004

The diffusional behavior of the ternary partially miscible liquid system acetonitrile‐benzene‐n‐heptane is investigated at 25°C using the diaphragm cell technique. The mutual diffusivity of the partially miscible binary system acetonitrile‐n‐heptane is found to be a strong function of concentration; the concentration dependence is described using a linear relationship. The diffusion coefficient matrix of the ternary system acetonitrile‐benzene‐n‐heptane is determined at a number of points, and the ternary diffusion matrices are found to be significantly coupled with the off‐diagonal elements of about 10 to 40% of the main diffusion coefficients.
Statistical characteristics of thin, wavy films III. Structure of the large waves and their resistance to gas flow
Authors: Chu K. J. , Dukler A. E.
Published: June 2004

Two classes of random waves exist on falling films at flow rates of practical interest; large waves which carry the bulk of the liquid and small waves which cover the substrate. In this paper statistics of the large waves are presented and compared with existing theory. These waves are bimodal in character at ReL > 700. The form drag of the large waves is shown to contribute negligibly the observed pressure drop in the gas phase. It is thus concluded that the small wave structure controls the fluid resistance and transfer processes in the gas while the large waves control these same processes in the liquid film.
Drag reduction fundamentals
Authors: Virk P. S.
Published: June 2004

Drag reduction by dilute solutions of linear, random‐coiling macromolecules in turbulent pipe flow is reviewed. The experimental evidence is emphasized in three sections concerned with the graphical display of established features of the phenomenon, data correlation and analysis, and the physical mechanism of drag reduction.
Grouping of many species each consumed by two parallel first‐order reactions
Authors: Luss Dan , Golikeri Sudhir V.
Published: June 2004

The behavioral features of a mixture containing many species each of which participates in two competing parallel first‐order reactions may deviate significantly from those of the individual species. For example, the grouped selectivity may depend on the conversion and attain up to N‐2 extremal values where N is the number of the reactants in the mixture. The kinetics of the grouped species depends on the composition of the feed and can be of an unconventional functional form. The use of empirical grouped kinetics may lead to unexpected pitfalls. For example, grouped rate expressions based on experiments carried out in one reactor may not be adequate for predicting the behavior in a reactor with a different residence time distribution.
Synthesis of separation sequences by ordered branch search
Authors: Rodrigo B. Fernando R. , Seader J. D.
Published: June 2004

An efficient and algorithmic procedure is developed for the synthesis of multicomponent separation sequences. The procedure involves list processing of the prossible separation subproblems followed by an ordered branch search to find the optimal sequence with respect to system structure. The technique is conveniently represented by an and/or directed graph. The distribution of sequence costs for a separation problem is considered. When a wide distribution exists, only a minimum of separators need be analyzed to find the optimal sequence. Even when a narrow distribution of sequence costs exists, not all sequences must be developed. The importance of near optimal sequences is examined, and the search procedure is extended to find those sequences whose costs are within a specified factor of the cost of the optimal sequence.
Mixing in the interaction zone of two free jets
Authors: Becker H. A. , Booth B. D.
Published: June 2004

Mixing in the interaction zone of two round free jets with nozzle axes intersecting at half‐angles of 15, 30, and 45 deg. has been studied by the smoke scattered light technique. The fields of mean concentration and concentration fluctuation intensity were mapped with one jet marked with smoke, the other jet marked, and both jets marked. The correlation function between the concentration fluctuations associated with fluid of the two nozzle streams has been calculated from the results and is an important characteristic of the mixing field and a significant measure of molecular mixedness. A transport equation for the associated covariance function is derived, and the special features of the mathematical modeling problem for this class of mixing process are discussed. The implications of the results for processes involving chemical reactions are examined.
Numerical treatment of laminar flow in helically coiled tubes of square cross section. Part II. Oscillating helically coiled tubes
Authors: Joseph B. , Adler R. J.
Published: June 2004

The numerical method of Part I is extended to study periodic laminar flow in helically coiled tubes of square cross section oscillating sinusoidally about their helix axis. Depending on the relative strength of the wall velocity and the velocity of flow through the tube, one of three flow regimes occur. When the wall velocity is small, the computed results resemble these for a stationary helix. When the wall velocity dominates, the direction of the secondary flow is reversed. When the wall and flow velocities are comparable, the secondary flow pattern varies periodically in time and sometimes alternates in direction.
Breakup of a turbulent liquid jet in a low‐pressure atmosphere
Authors: Phinney Ralph E.
Published: June 2004

Breakup length measurements were made of turbulent liquid jets in a low‐pressure atmosphere. As a result of these experiments, it was found that the jets obey a pseudo laminar analogy only at low exit velocity. The nondimensional breakup length correlates with the jet Weber number through the complete range.
Transient viscoelastic flow of polymer solutions
Authors: Leppard W. R. , Christiansen E. B.
Published: June 2004

Stress growth and stress decay data for two highly viscoelastic polymer solutions indicate that the first and second normal stress differences grow and decay at the same relative rates. These shear stress and first normal stress difference data are not represented well by the Spriggs, Bogue‐Chen, or Carreau constitutive equations. The second normal stress difference, stress growth, and decay data are the first to be reported. The data were derived from radial pressure distributions and total normal and tortional forces obtained in cone and plate shearing. Sensitive miniature pressure transducers with pressure sensing diaphragms mounted flush with the plate surface provided the radial pressure distribution data.
The vapor‐liquid equilibrium of the hydrogen—n‐butane system at elevated pressures
Authors: Klink A. E. , Cheh H. Y. , Amick E. H.
Published: June 2004

The vapor‐liquid equilibrium of the hydrogen–n–butane system was studied at temperatures between 54° and 121°C and at pressures up to 167 atm. The fugacity of hydrogen in the vapor phase was measured directly by using a palladium‐silver semipermeable membrane, whereas p‐T‐x‐y data were obtained in a conventional manner.

Henry's constants for hydrogen in n‐butane were obtained from the experimental fugacity data without making any assumptions about the vapor phase. Constant‐pressure, liquid‐phase activity coefficients for both hydrogen and n‐butane were calculated and correlated by using a modified van Laar equation.
On the prediction of ultimate separation in parametric pumps
Authors: Foo S. C. , Rice R. G.
Published: June 2004

Quantitative theories based on first principles are derived to explain the roles of heat and mass transfer in the attainment of steady state or ultimate separation in closed direct‐thermal‐mode parametric pumps. The theoretical results are in agreement with applicable experimental data, including the experimental anomaly called reversed separation. Under conditions when the axial dispersion is much greater than molecular diffusion, the theory predicts and experiments confirm that 1/ln(α∞) varies in a linear way with fluid displacement at constant frequency. An additional asymptotic result suggests that when Sh » PeM, there is a simple linear connection between 1/ln(α∞) and PeM which is supported by experimental data.
Turbulent motion, mixing, and kinetics in a chemical reactor configuration
Authors: McKelvey Kenneth N. , Yieh Heh‐Nien , Zakanycz Stephen , Brodkey Robert S.
Published: June 2004

The nature of turbulence and mixing in a reactor used by Toor for kinetic studies was investigated in detail. Simple empirical methods were useful for estimating the decay of the scalar fluctuations. An equation, based on continuity, was used with measured velocities and an improved procedure at the inlet to calculate results that agree well with the kinetic data.
An unsteady state method for measuring the permeability of small tubular membranes
Authors: Stevenson James F. , Von Deak Michael A. , Weinberg Mark , Wade Schuette R.
Published: June 2004

An experimental method is described for measuring the permeability of small tubular (hollow fiber) membranes by means of an unsteady state diffusion experiment. Permeability data obtained by this method are reported for experimental collagen and commercial cellulose acetate membranes for urea, sucrose, and polyethylene glycol (MW ∼ 4 000).
The stability of a vertical flow which arises from combined buoyancy modes
Authors: Boura Andre , Gebhart Benjamin
Published: June 2004

We consider a mass transfer induced buoyancy force, superimposed on a thermally induced one, in a flow generated adjacent to a vertical surface. Flow and stability were investigated for a Prandtl number of 0.7; for Schmidt numbers of 2.0, 0.94, and 0.2; and for different magnitudes of the buoyancy effects.
Secondary nucleation of two fast growth systems in a mixed suspension crystallizer: Magnesium sulfate and citric acid water systems
Authors: Sikdar Subhas K. , Randolph Alan D.
Published: June 2004

Secondary nucleation of magnesium sulfate and citric acid was studied in a seeded back mixed crystallizer. The MSMPR type of exponential population density distribution was obtained above 8 μm size in quasi steady state operation. Growth rates were satisfactorily correlated with supersaturation. Nucleation rates correlated with supersaturation and slurry properties. Agitation level (RPM) did not have any significant effect on the nucleation rates, presumably implying surface regeneration limited nucleation.
Experimental study of the residence time distribution in plasticating screw extruders
Authors: Wolf David , White Don H.
Published: June 2004

Experimental residence time distribution functions for the liquid and solids conveying processes by a screw conveyer and for the polymer in a plasticating extruder were obtained by using a radioactive tracer technique. A comparison was made between the experimental results and several theoretical models available for melt extrusion and mixing processes.
Optimal feedback control of time‐delay systems
Authors: Oh Se H. , Luus Rein
Published: June 2004

The suboptimal control policy obtained from series expansion of time‐delay terms is useful when the delays are small. The second method involving direct search on the constant gain matrix is applicable even for large delays. Both of these proposed methods are computationally simple and lead to easy implementation in practice.
Transient diffusion in solids with a bipore distribution
Authors: Ma Y. H. , Lee T. Y.
Published: June 2004

Transient diffusion of n‐butane, iso‐butane, and 1‐butene in synthetic CaX(Na) spherical pellets is studied in a constant volume, well‐stirred system. The intracrystalline diffusion coefficients are in the order of 10−14 cm2/s, and the activation energy is about 7.0 Kcal/g‐mole. Experimental data agree well with a mathematical model developed to describe transient diffusion.
Prediction of transport processes within porous media: Diffusive transport processes within anisotropic or isotropic swarms of nonspherical particles
Authors: Neale G. , Nader W. K.
Published: June 2004

The effects of particle shape and orientation upon diffusive transport processes occurring within unconsolidated porous media are investigated analytically. By means of a generalization of an earlier presented geometric model, diffusivities are predicted for both anisotropic systems (represented by swarms of aligned oblate or prolate spheroids) and isotropic systems (represented by swarms of randomly orientated spheroids). Theoretical predictions are compared with experimental data reported in the literature.
Adsorption and desorption of particles and their chromatographic separation
Authors: Ruckenstein Eli , Prieve Dennis C.
Published: June 2004

Rates of adsorption/desorption are calculated by considering Born, double‐layer, and van der Waals forces. Conditions exist where rates are highly sensitive to particle size, shape, and chemical constitution because diffusion over a potential barrier controls. On this basis, a new separation technique, called potential‐barrier chromatography, is suggested.
Steady state multiplicity of adiabatic gas‐liquid reactors: II. The two consecutive reactions case
Authors: Sharma Shanmuk , Hoffman Lee A. , Luss Dan
Published: June 2004

A model describing two consecutive gas‐liquid reactors in a continously stirred‐tank reactor is developed with reaction factors used to account for the interactions between the chemical and transport rate processes. A parametric numerical study revealed several interesting effects, including the existence of up to seven steady state solutions. The predictions of the model adequately describe the steady state multiplicity observed during the chlorination of liquid n‐decane. It is shown that the steady state multiplicity can serve as an excellent tool for discriminating among rival models and estimation of kinetic parameters.
Axial distribution of reactivity inside a fluid‐bed contactor
Authors: Furusaki Shintaro , Kikuchi Tatsuji , Miyauchi Terukatsu
Published: June 2004

The axial destribution of reactivity inside a fluid‐bed contactor is studied for the hydrogenation of ethylene. The reactivity is large near the surface of the dense phase. The significant effect of the dilute phase, or the free board region, is verified experimentally, and the contact efficiency in the transition zone and in the dilute phase is obtained. The contact efficiency was approximated by ηc = 1 − 0.75 (ϵe/ϵede)0.4. The temperature rise in the dilute phase is measured in the small reactor. The transition zone between the dense and dilute phases is almost isothermal, but it is found that temperature increases in the dilute phase.
Solid phase reactions under nonadiabatic conditions
Authors: Vavanellos T. D. , Ruckenstein Eli
Published: June 2004

The kinetics of solid phase reactions proceeding through nucleation and subsequent nucleus growth is treated by taking into account heat losses by convection and radiation from the reacting solid. A critical initial reaction temperature dependent upon particle size is identified below which the reaction decays and above which explosion can occur.
The rheological properties of suspensions of rigid particles
Authors: Jeffrey D. J. , Acrivos Andreas
Published: June 2004

Experimental and theoretical work on the rheological properties of suspensions are reviewed. Attention is focused on systems consisting of rigid, neutrally buyoant particles suspended in Newtonian fluids; no restrictions, however, are placed on the concentration of the particles or on the forces acting in the suspension. The assumption that an effective viscosity depending solely on the volume fraction of the particles suffices to describe the rheology of suspensions is examined and shown to be inadequate. Indeed, the experimental evidence strongly supports the view that suspensions behave macroscopically as non‐Newtonian fluids whose rheological properties are influenced by a large number of factors; these factors are listed. The various theories that have been put forward to explain the flow of suspensions are discussed, with particular emphasis being placed on the nature of the approximations made, so that purely empirical formulas can be clearly separated from those having a theoretical basis. Suggestions for future work, both theoretical and experimental, are provided.
Onset of draw resonance during isothermal melt spinning: A comparison between measurements and predictions
Authors: Weinberger C. B. , Cruz‐saenz G. F. , Donnelly G. J.
Published: June 2004

Various polymer melts were spun isothermally to determine the critical extensional strain at which draw resonance occurs. Simultaneously, the variation of apparent spinning viscosity with extensional strain was measured. Experimental results failed to confirm the theoretical prediction that strain thickening behavior leads to enhanced stability.
Lagrangian simulation of dispersion in turbulent shear flow with a hybrid computer
Authors: Lee Naugab , Dukler A. E.
Published: June 2004

Two‐dimensional turbulent diffusion is modeled with a generalized Langevin equation. Instantaneous velocities are simulated by using white noise filtered to simulate turbulence. By generating fluctuating signals that are partially correlated, it is possible to model diffusion for a turbulent shear field. The result show that the dispersion is independent of shear for long and short diffusion times but depend strongly on shear for intermediate times.
Optimal design of pressure relieving piping networks by discrete merging
Authors: Cheng Wai‐biu , Mah Richard S. H.
Published: June 2004

Refinery relief‐header network design can be optimized by a new discrete optimization technique which requires no rounding of decision variables, no initial guesses for the solution, and no artificial termination criteria; it produces parametric solutions when the optimum is attained. The method is also faster and more compact than the alternative continuous optimization methods.
An effective computational algorithm for suboptimal singular and/or bang‐bang control II. Applications to nonlinear lumped and distributed systems
Authors: Nishida N. , Liu Y. A. , Lapidus Leon , Hiratsuka S.
Published: June 2004

A new and simple algorithm based on the piecewise maximization of the Hamiltonian and a limiting process utilizing a penalty function of the control variables for the computation of suboptimal singular and/or bang‐bang control, previously developed and applied to linear lumped systems in Part I, is tested on four typical nonlinear lumped and distributed systems of particular chemical engineering interest. The computational results have shown that the proposed algorithm is a very effective method for solving singular and/or bang‐bang control problems with high state dimensionality, extreme nonlinearity, and multiple controls.
Trajectory analysis of deep‐bed filtration with the sphere‐in‐cell porous media model
Authors: Rajagopalan Rajamani , Tien Chi
Published: June 2004

This paper presents a model for the initial particle deposition in a deepbed filter with a sphere‐in‐cell porous media model used. The analysis includes all the relevant mechanisms, and the results indicate that deposition occurs under favorable surface interactions. A semiempirical expression relating collection efficiency and operating parameters is presented.
Solution procedures for indexed equation sets: Structural considerations
Authors: Allen Gary L. , Westerberg Arthur W.
Published: June 2004

Results are obtained permitting the systematic development of solution procedures for indexed equations by analyzing and combining a number of small problems. The solution procedures obtained are independent of index limits and can be written compactly by using nested FORTRAN DO‐loops or equivalent. To illustrate the approach, a solution procedure is developed for a multistage, multicomponent distillation column segment. The solution procedure is valid for any number of stages and components.
Capture of small paramagnetic particles by magnetic forces from low speed fluid flows
Authors: Cummings Daniel L. , Himmelblau David A. , Oberteuffer John A. , Powers Gary J.
Published: June 2004

High gradient magnetic separators are able to capture small, dilute, paramagnetic particles from high velocity fluid flows. Capture cross sections are computed and correlated with dimensionless groups for a bare ferromagnetic collector.
The fluid mechanics and heat transfer of injection mold filling of thermoplastic materials
Authors: Kuo Youti , Kamal Musa R.
Published: June 2004

For injection flow of thermoplastic material in thin cavities, with some minor restrictions, both pressure and stream function obey Laplace equations. An analytical‐numerical method, with a generalized viscous model used, is developed for determining the shape of a progressing flow front and for computing flow quantities and temperature distributions. Specifically, flows in a rectangular cavity are solved and compared to experiments.
Dialysis study of diffusion in a flowing suspension
Authors: Hsu George C. , Lindgren Robert G. , Chung Ying‐Chee , Corcoran William H.
Published: June 2004

Comparison of solute concentrations at the outlet of a model dialyzer with values calculated from the appropriate convective diffusion equation yielded effective diffusion coefficients for mass transfer of sodium chloride in sherared suspensions of 37 to 74 μ spheres of a copolymer of styrene‐divinylbenzene. Significant mass transfer augmentation was observed over that attributable to molecular diffusion, and the effective diffusivity increased with increasing concentration of suspension but remained relatively constant with respect to shear rate over the experimental range.
A lumping and reaction scheme for catalytic cracking
Authors: Jacob Solomon M. , Gross Benjamin , Voltz Sterling E. , Weekman Vern W.
Published: June 2004

A predictive kinetic model has been developed for fluid catalytic cracking (FCC). The kinetic scheme involves lumped species consisting of paraffins, naphthenes, aromatic rings, and aromatic substituent groups in light and heavy fuel oil fractions. The kinetic model also incorporates the effect of nitrogen poisoning, aromatic ring adsorption, and time dependent catalyst decay. The rate constants for these lumped species are invariant with respect to charge stock composition. The predictive capabilities of the model have been verified for wide ranges of charge stocks and process conditions.
Analysis of rectilinear rivulet flow
Authors: Bentwich Michael , Glasser David , Kern Jochen , Williams Donald
Published: June 2004

A liquid flowing over a nonwettable surface can form rivulets of various types. The regime of rectilinear rivulet flow plays a key role in that it provides the basis for the study of the other regimes.

An analytical solution for the velocity distribution of rectilinear rivulet flow down a vertical plate is derived. A generalized Ritz‐Galerkin method is used to obtain a polynomial solution for the case of an inclined plate.

These results, unlike those of previous authors, enable one to calculate all the rectilinear flow properties of rivulets over the complete range of practical interest.
Shear viscosity of native and enzyme hydrolyzed amioca starch pastes
Authors: Cruz Angel , Russel William B. , Ollis David F.
Published: June 2004

Shear viscosity of an Amioca starch paste undergoing hydrolysis by immobilized α‐amylase is shown to follow a power law behavior. The power law constants are uniquely related in a way which reduces the power law to a dimensionless form, a result previously reported only for retrograding starch and coagulating milk. The concept of a total hydrodynamic volume [Amioca starch molecules (amylopectin) plus associated immobilized liquid] is extended to concentrations above the dilute solution regime. A molecular interpretation is proposed for the shear viscosity behavior of Amioca starch pastes vs. extent of starch hydrolysis.
Process design in a dynamic environment: Part I. A decomposition technique to study the stability of chemical engineering systems
Authors: Stephanopoulos George , Schuelke Lawrence M.
Published: June 2004

The stability of various chemical engineering systems is studied through the use of vector Lyapunov functions. A decomposition technique is employed which reduces the problem to small, independent, free subsystems that can be analyzed through Lyapunov's second method. The stability characteristics of the overall system are then related to the behavior of a linear system which is easily analyzed.
On the dynamics of fluid interfaces. Part I
Authors: Ramabhadran T. E. , Byers Charles H. , Friedly John C.
Published: June 2004

The system of a dispersed phase oscillating in a continuous medium is investigated theoretically with the specific purpose of developing a new technique for the measurement of interfacial viscous and elastic properties. By use of the well‐known models of interfacial mechanics, the decay and frequency of liquid drops oscillating in a gas and of gas cavities oscillating in a liquid are computed as functions of dynamic interfacial properties. The results of the theory indicate, for the size range considered, that the elastic properties dominate over the viscous properties and that dilational effects dominate in the case of the drop in air and shear effects dominate in the case of the cavity in a liquid. The frequency does not seem to depend on the dynamic interfacial properties.
Mathematical modeling and optimization of the dehydrogenation of ethylbenzene to form styrene
Authors: Clough David E. , Ramirez W. Fred
Published: June 2004

A mathematical model is developed for a styrene pilot plant reactor. The steady state version of this model was used to optimize the location of a steam injection port part way along the catalytic bed. Significant improvement in reactor performance was predicted by splitting the steam feed between the reactor inlet and the injection port. Performance was measured in terms of market value of products minus a utility cost for the steam. Studies were also carried out via computer simulation to determine optimal operating conditions. An important result was the relationship of optimal steam‐to‐ethylbenzene feed ratio to the kinetic parameters which describe the main dehydrogenation reaction. A pilot plant was constructed and operated in order to investigate experimentally the predictions of the mathematical model. Instrumentation was designed and installed so that an on‐line digital computer could acquire process measurements directly and establish operating conditions. The experimental program confirmed the improved performance by operation of the reactor with a steam injection port and the existence of an optimum of the steam‐to‐ethylbenzene feed ratio as indicated by simulation.
Hydrogenolysis kinetics of ethane and n‐pentane over unsupported copper/nickel and platinum catalysts
Authors: Ollis David F. , Taheri Hassan
Published: June 2004

Two kinetic models of hydrocarbon hydrogenolysis over monometallic surfaces, based respectively on catalytically uniform or nonuniform surfaces, are applied to ethane and n‐pentane hydrogenolysis results over copper‐nickel alloy catalysts as well as the monometallic catalysts platinum and nickel. If no direct hydrogen desorption appears in any postulated irreversible step, both models predict the same composition for the important surface intermediates CnHx (n = 1, s), where x depends upon the catalyst.

This analysis predicts that for essentially all alloy catalysts to which the postulated sequences may apply, the hydrogenolytic surface intermediate CnXx contains one more hydrogen atom than that calculated for a nickel catalyst: specifically, C2H3 (alloy) vs. C2H2 (nickel) for ethane and C5H6 (alloy) vs. C5H7 (nickel) for n‐pentane.
Exothermic gas absorption with chemical reaction
Authors: Mann Reginald , Moyes Hilary
Published: June 2004

The film theory for gas absorption with chemical reaction has been extended to take into account the release of heat due to solution and reaction. The analysis is applied to the industrially significant sulfur trioxide‐dodecylbenzene system, and large increases in interface temperature are predicted during absorption. The enhancement factor behavior is correspondingly complex owing to the interaction of solubility reduction and rate constant enlargement. Some initial experimental measurements with the laminar jet technique confirm the need for and the basic soundness of the theory.
Turbulent mass transfer rates to a wall for large Schmidt numbers
Authors: Shaw Dudley A. , Hanratty Thomas J.
Published: June 2004

New measurements are presented on the influence of Schmidt number on the rate of mass transfer between a turbulent fluid and a pipe wall. It is found that for large Schmidt numbers the fully developed mass transfer coefficient is related to the friction velocity and the Schmidt number by the equation
equation image
The experiments are accurate enough to rule out the Sc−2/3 or the Sc−2/3 relations commonly used, deduced from plausible limiting expressions for the eddy diffusivity close to a wall. It is argued that these expressions arevalid only over a vanishingly small portion of the concentration field as Sc → ∞.