bluuebunny/crossref_metadata_2025_split huggingface dataset:
The continuous‐lumping method for vapor‐liquid equilibrium calculations
Authors: Moore Patrick K. , Anthony Rayford G. 
Published: June 2004

AbstractThe continuous‐lumping method is a refinement of continuous thermodynamics which does not depend upon the continuous‐mixture hypothesis. The method utilizes a generalized Fourier series expansion of a functional formulation of the equilibrium relations obtained by embedding the classical discrete equilibrium equations into generalized function space. The resulting method provides an effective means of reducing the number of parameters needed to describe a many‐component, complex mixture; furthermore, the method provides a straightforward means of converting the equilibrium equations to the new parameterized form. The error associated with the reduction in number of parameters can be easily estimated using the ratio convergence test for mathematical series. The theory of the method is first presented and the method is then used in an example calculation to illustrate the advantages of the method over pseudocomponent lumping and continuous thermodynamics. The method is useful particularly for mixtures described by chromatographic data.
Drop oscillations in liquid‐liquid systems
Authors: Basaran Osman A. , Scott Timothy C. , Byers Charles H. 
Published: June 2004

AbstractWhen the ratio of the drop radius to the distance separating any two drops and the relative importance of gravitational to surface forces are both small, the small amplitude oscillations of a drop of one viscous fluid immersed in another fluid are governed by the nonlinear dispersion relation derived by Miller and Scriven (1968). The dispersion relation has been solved numerically to determine the character of oscillations for arbitrary values of drop size, physical properties of the two fluids, and interfacial tension. The new theoretical results determine the range of validity of the low‐viscosity approximation of Miller and Scriven, and are also shown to be essential for proper interpretation of many previously reported experimental results. New experimental measurements of natural frequencies of oscillation of water drops falling in 2‐ethyl‐1‐hexanol, a system having properties characteristic of many others in solvent extraction, agree well with the theoretical predictions when drop radius is smaller than a critical size. The frequencies of oscillations of larger drops are better described by the dispersion relation due to Subramanyam (1969), which accounts for the relative motion of the two phases.
Magnetic determination of axial catalyst temperature profiles
Authors: Cale T. S. , Merson J. A. 
Published: June 2004

AbstractA magnetic thermometric method is used to determine cross‐sectional average axial catalyst temperature profiles for superparamagnetic neckel catalyst beds during ethane hydrogenolysis, an exothermic reaction. Each solid temperature profile is determined from an axial profile of cross‐sectional average magnetization and is represented by a polynomial. In turn, each magnetization profile is determined from voltage data obtained as the bed is moved through an AC permeameter. A Fredholm equation of the first kind, “regularized” using a minimum variance constraint, is inverted to determine the magnetization profile.The determination of the axial temperature profile for a reactor operating at 11.0% conversion is detailed. It provides a good test of the method used. Some limitations of the method are highlighted by attempts to analyze data from a reactor operating at complete conversion. The potential for model parameter estimation is discussed.
Bifurcation analysis in heterogeneous azeotropic distillation
Authors: Widagdo Soemantri , Seider Warren D. , Sebastian Donald H. 
Published: June 2004

AbstractParameterization with respect to the aqueous reflux ratio has been carried out for the steady‐state analysis of a tower to dehydrate secbutanol using disecondary butyl ether as the entrainer. With an equilibrium‐stage model, singularities are observed as the second liquid phase is introduced on the trays and regions of steady‐state multiplicity are demonstrated. Furthermore, a critical aqueous reflux ratio, in the vicinity of which two liquid phases are introduced on most of the trays, varies only slightly with the number of trays in the tower. The model predicts that the product purities and recoveries remain high using one‐third of the trays in the industrial SBA‐II tower. Bifurcation analysis for a single stage does not explain these observations, and the effect of recycle is suspected.
Dispersion and diffusion influences on yield in complex reaction networks
Authors: Liou Jiunn‐Shyan , Balakotaiah Vemuri , Luss Dan 
Published: June 2004

AbstractDifferences in the dispersion and/or catalytic pellet size between laboratory and commercial reactors, operating at the same average residence time, may lead to differences in the yield of a desired product. Bounds are developed for predicting the maximal design uncertainty introduced by these phenomena for a network consisting of an arbitrary number of irreversible first‐order reactions. A major advantage of these bounds is that they do not require any knowledge of the rate constants. It is shown that in a packed‐bed reactor, the fractional yield loss is smaller than:

where m − 1 is the number of reaction steps involved in converting a reactant to the desired product, σ is the dimensionless variance of the residence time density function, Bim is the Biot number, p2 = [(Vp/Sx)2(1/Deτ)], and τ is the average residence time.
Design and minimum reflux for heterogeneous azeotropic distillation columns
Authors: Pham Hoanh N. , Ryan Peter J. , Doherty Michael F. 
Published: June 2004

AbstractA simple design technique for heterogeneous distillation columns has been developed. The underlying geometric conditions which govern minimum reflux are shown to share certain common features with homogeneous distillations, but differ in some important respects. It is shown that heterogeneous columns display some unusual sensitivities to the design parameters. The most notable being the drastic swings in the composition and temperature profiles with very small changes in the level of trace impurities in the product stream.
Axial distribution of solid holdup in bubble column for gas‐liquid‐solid systems
Authors: Matsumoto Toshitatsu , Hidaka Nobuyuki , Morooka Shigeharu 
Published: June 2004

AbstractThe axial distribution of solid holdup was investigated in a bubble column of 0.07 m in diameter and 4.25 m in height. The particle phase was glass beads of diameter 66, 118, 243, 465 or 1,300 μm. The effective slip velocity and the axial dispersion coefficient of the solid particles were evaluated in batch operation without solids feed and were correlated on the basis of mixing length theory. The equations obtained were applied to analyze axial profiles of particle concentration with a continuous feed of solids, and experimental data in the literature were simulated successfully over a wide range of solid concentration.
Mathematical analysis of two‐phase flow in low‐permeability porous media
Authors: Arastoopour Hamid , Semrau James 
Published: June 2004

AbstractA one‐dimensional isothermal transient two‐phase flow model of gas and liquid in a low‐permeability medium has been developed from the general mass and momentum balances.The characteristic roots of the governing differential equations are real and distinct. Therefore, solution of the flow equations may be attempted by a stable initial‐value finite‐difference scheme. A numerical solution was obtained using the method of lines.Calculated two‐phase flow parameters are consistent with expected flow behavior and reflect the sensitivity of fluid flow to porosity, gas and liquid permeability, and capillary pressure in a tight sands porous medium. Calculated gas flow rates compared well with experimental data obtained at the Institute of Gas Technology (IGT) for low‐permeability sandstone.
Control mechanisms of fluidized solids circulation between adjacent vessels
Authors: Fox D. , Molodtsof Y. , Large J. F. 
Published: June 2004

AbstractMany industrial proceses require the circulation of particles between reacting fluidized compartments at a stable, but flexible rate, so that the processes can be operated at different solids rates. In order to understand the phenomena involved in the circulation and its control, circulation of sand particles has been studied through a new experimental approach, using an open‐loop two compartment circulating system.Experimental results show that the control of the circulation rate depends on three phenomena: the vertical resisting force in the fluidized compartments, the contraction of flow in the communication zone, and the bypass of gas between the compartments. For industrial purposes, the first appears to be predominant in the control of the solids rate. The second ensures neither the strict control of this rate nor the required flexibility. The link between the gas bypass and the circulation phenomena is explained and recommendations for the design and operation of circulating systems are given.
Sequential gas‐solid reactions
Authors: Fortini Arthur J. , Perlmutter Daniel D. 
Published: June 2004

AbstractA model is developed describing consecutive gas‐solid reactions occurring in porous media. The model calls for independently measurable parameters and predicts two maxima in the reaction rate at intermediate conversions. The low temperature (350°C) reduction of hematite to iron in a hydrogen‐nitrogen atmosphere was used to test the model. The experimental data confirmed the expected rate maxima. The conversion predictions are very close to the data for conversions below 30%, but are systematically somewhat lower than the experimental values for higher levels of conversion. An explanation for the discrepancy is offered in terms of the description of the pore structure.
Melt blowing: General equation development and experimental verification
Authors: Uyttendaele Marc A. J. , Shambaugh Robert L. 
Published: June 2004

AbstractA model has been developed for steady polymer melt blowing. This model includes the dominant effect that the forwarding air has upon the process. Inertial, gravitational and heat transfer effects are also included. The model equations are solved numerically with both Newtonian and viscoelastic (Phan‐Thien and Tanner) constitutive equations. The predicted results compare favorably with actual experimental data.
A study of multicomponent adsorption equilibria by liquid chromatography
Authors: Ching Chi Bun , Chu Khim Hoong , Ruthven Douglas M. 
Published: June 2004

AbstractEquilibrium relations for the fructose‐dextran‐water system on silica gel have been determined by a liquid chromatographic method. The experimental procedure discussed provides a simple and straightforward means of determining adsorption equilibria. The ternary adsorption equilibria, derived from chromatographic retention time measurements of binary systems, are verified by the equilibrium theory developed by Gluekauf (1949).
Self‐consistent local composition model of electrolyte solutions
Authors: Ananth M. S. , Ramachandran Sunder 
Published: June 2004

AbstractA self‐consistent local composition theory for the excess Gibbs free energy of a multicomponent electrolyte solution is developed. The theory incorporates correct pair counting, assumes that like‐charged ions cannot be nearest neighbors of each other, and accounts for the effect of second nearest neighbor interactions.A perturbation analysis of the model, linear in the interaction parameters, is also carried out. For a given solvent and a given class of electrolyte the perturbed theory yields universal functions of molality, which can be weighted by suitable parameter values and added to give the desired property. The parameters can be expressed in a temperature‐independent form. This theory correlates very well the data on osmotic and activity coefficients in single‐solute aqueous solutions up to very high concentrations (up to 20 M) as well as over a range of temperatures.
Experiments on the conductivity of suspensions of ionically‐conductive spheres
Authors: Bashir Y. M. , Goddard J. D. 
Published: June 2004

AbstractThis is a report on the ionic conductivity of monodisperse, neutrally‐buoyant suspensions of ion‐exchange beads, both AC total‐ion conductivity and DC specific‐ion conductivity of an electrochemically‐active species. They represent the zero Péclet‐number and the large Péclet‐number limits of mass transfer, respectively.A rotating disc electrode was employed for the DC studies and a well mixed conductivity cell for the AC—for particle volume fractions ϕ ranging from zero to about 45%. Novel techniques were developed for rapidly determining the particle AC conductivity and for modifying the relative conductivity α of ion‐exchange beads by poisoning with immobilely‐bound ions. For α values, 0.044⩽ α ⩽ 1.48, of this study Maxwell's classical relation is shown to be adequate for ϕ ⩽ 0.5, which is, in agreement with Turner (1973, 1976).Our results for the DC conductivity differ somewhat from those of Andersen (1987) land show the weak dependence on particle Péclet number predicted by the dilute‐suspension theory of Nir and Acrivos (1976) for Pe ≫ 1.
Stress distribution in a packed bed above raceway cavities formed by an air jet
Authors: Apte Vivek B. , Wall Terry F. , Truelove John S. 
Published: June 2004

AbstractThe vertical stress profile in a packed bed above the cavities formed by an upward, high‐velocity air jet is estimated from a force balance analysis and static pressure measurements. The objective is to understand and determine the forces responsible for maintaining the cavity roof. Such cavities, formed in an iron blast furnace, adjacent to the hot air blast emanating from the tuyere pipes, are called raceways. A net upward force provided by the gas pressure drag and the support from the bed walls holds the raceway roof in its position. Abrupt changes in the stress and the gas velocity are observed near the roof. The zero vertical stress is also found close above the roof but fluctuates vertically with the raceway size, which varies irreversibly following a cyclic change in the blast rate.
Diagnostic model processor: Using deep knowledge for process fault diagnosis
Authors: Petti Thomas F. , Klein Jim , Dhurjati Prasad S. 
Published: June 2004

AbstractMany recent attempts to use expert systems for process fault diagnosis have included information derived from deep knowledge. This information is generally implemented as a rule‐based expert system. Drawbacks of this architecture are a lack of generality, poor handling of novel situations, and a lack of transparency. An algorithm called the diagnostic model processor is introduced; it uses the satisfaction of model equations from process plants to arrive at the most likely fault condition. The method is generalized by the process model and diagnostic methodology being separated. The architecture addresses each of the shortcomings discussed. Experiments show that the methodology is capable of correctly identifying fault situations. Furthermore, information is derived from an a priori analysis technique, which is used to show the degree to which different faults can be discriminated based on the model equations available. The results of this analysis add further insight into the diagnoses provided by the diagnostic model processor.
Simple process equations, fixed‐point methods, and chaos
Authors: Lucia Angelo , Guo Xinzhou , Richey Paula J. , Derebail Ramnath 
Published: June 2004

AbstractThe chaotic behavior of fixed‐point methods for steady‐state process simulation is studied. It is shown that direct substitution and Newton's method exhibit all of the rich structure of chaos (period doubling, aperiodicity, fractal basin boundaries, and related properties) on simple process examples. These examples include finding roots to the Soave‐Redlich‐Kwong and Underwood equations, dew point and flash calculations for heterogeneous mixtures, and a simple process flowsheet.For single variable problems, it is shown that direct substitution follows a classical period‐doubling route to chaos. On the other hand, the chaotic behavior of direct substitution and Newton's method on multivariable problems is considerably more complex, and can give the appearance that no organized route to chaos is followed. For example, for the dew point problems, truncated period doubling, odd periodic cycles, and chaotic behavior can be observed, within which are embedded narrow regions of global convergence. Many numerical results and geometric illustrations are presented.
Structure of plane underexpanded air jets into water
Authors: Loth Eric , Faeth Gerard M. 
Published: June 2004

AbstractAn experimental and numerical investigation of the structure of plane underexpanded turbulent air jets in water was conducted to characterize their structure and mixing properties. Measurements included void fraction profiles, static pressure distributions, entrainment rates, and high speed flow visualization. A locally homogeneous flow model was also developed with compressibility effects treated using an effective adapted jet condition. Static pressure measurements confirmed the presence of a shock‐wave‐containing external expansion region for underexpanded air jets in water, similar to results observed for underexpanded air jets in air. In addition, the plane jets exhibited half‐widths (based on void fractions) that were two to three times greater than half‐widths (based on scalar properties) observed for single‐phase jets. This behavior follows from the strong sensitivity of void fraction to mixing levels due to the large density ratio of the flow. Predictions of void fraction and mass entrainment were encouraging, but performance was found to be sensitive to initial conditions and effects of large‐scale unsteadiness near the jet exit.
Computation of flow patterns in circulating fluidized beds
Authors: Tsuo Yuan P. , Gidaspow D. 
Published: June 2004

AbstractFlow regimes of dense‐phase vertical pneumatic transport of solids, referred to in the literature as circulating fluidized beds, have been computed using a generalization of the Navier‐Stokes equations for two fluids. In the less dense regime corresponding to volume fractions of solids of about 1%, the flow consists of centrally upward moving solids and downward moving clusters. The computations agree with observations made by high‐speed motion pictures and with measurements of radial solids concentrations and velocities. In the dense regime, corresponding to volume fractions of about 10%, a core‐annulus type of regime is obtained, with solids descending down at the wall. The computed voidage distributions and velocity profiles agree with measurement done at the Institute of Gas Technology.
Robust error‐in‐variables estimation using nonlinear programming techniques
Authors: Kim In‐Won , Liebman Michael J. , Edgar Thomas F. 
Published: June 2004

AbstractFor systems described by algebraic or differential equation models where all variables are subject to error, the error‐in‐variables method (EVM) for parameter estimation has been shown to be superior to standard least‐squares techniques. Previous EVM algorithms were developed assuming linear (or linearized) model equations. Unfortunately, many chemical engineering processes operate in strongly nonlinear regions where linear approximations may be inaccurate. In this paper, new algorithms using nonlinear programming techniques for the error‐in‐variables methods are proposed. In addition, a method for discerning when these methods are necessary is discussed. The proposed algorithms are compared to the least‐squares method and traditional error‐in‐variable approaches. Improved parameter estimates for several steady‐state nonlinear processes are demonstrated.
Platelet interaction with poly(ethylene oxide) networks
Authors: Chaikof Elliot L. , Merrill Edward W. , Coleman James E. , Ramberg Karen , Connolly Raymond J. , Callow Allan D. 
Published: June 2004

AbstractInterpenetrating polymer networks (IPNs) of poly(ethylene oxide) (PEO) and a polyether substituted polysiloxane were synthesized containing variations of PEO content (35 and 65% dry network weight) and PEO systematically varied from low to high molecular weight (2,000, 8,000, and 20,000). Biocompatibility was assessed by measureing 111In platelet deposition in a baboon femoral ex vivo shunt. Mass transfer analysis revealed that platelet transport to PEO/polysiloxane surfaces was kinetically limited and correlated with both PEO content and molecular weight. Differences in material performance were noted particularly after the initial 30 min blood contact period. In mid and high PEO molecular weight networks (8,000 and 20,000), reduced platelet deposition was noted with increased PEO content. In materials of high PEO content (65%), mid and high PEO molecular weight samples had significantly lower levels of platelet adsorption than PDMS (60 min; p< 0.05) or networks of low PEO molecular weight, coded 2K‐65 (30 and 60 min; p < 0.05). The lowest level of platelet deposition was noted on 20K‐65 networks, less than one platelet per 1,000 μm2.
Protein partitioning in PEG/dextran aqueous two‐phase systems
Authors: Diamond Alan D. , Hsu James T. 
Published: June 2004

AbstractUtilizing a modified form of the Flory‐Huggins theory of polymer solution thermodynamics, a generalized expression has been obtained for correlating protein partitioning in the polyethylene glycol (PEG)/dextran aqueous two‐phase systems. The expression relates the natural logarithm of the partition coefficient of the protein to the polymer concentration difference between the phases. The parameters of the relationship are a function of protein and phase forming polymer molecular weight, protein‐water, protein‐polymer and polymer‐water interaction parameters, and the electrostatic potential difference between the phases. The relationship was verified by partitioning 17 proteins covering a wide range of molecular weight in the tie lines of the above systems, along with data from the literature. This correlation will facilitate the selection and engineering scale‐up of aqueous two‐phase systems for biomolecule purification.
Development of a space‐charge transport model for ion‐exchange membranes
Authors: Guzmán‐Garcia Angel G. , Pintauro Peter N. , Verbrugge Mark W. , Hill Robert F. 
Published: June 2004

AbstractA two‐dimensional, electrokinetic transport model that incorporates ionic hydration, orientation of solvent molecules by an applied electric field, and solvent dipole‐dipole interactions is developed. The model is used to simulate equilibrium and transport experiments for perfluorosulfonic acid membranes containing aqueous alkali metal sulfate solutions. The membrane is modeled as an array of cylindrical pores. Solution of the mathematical model requires that the membrane porosity, water partition coefficient, coion partition coefficient, water diffusion coefficients, and coion and counterion diffusion coefficients be known. Membrane coion and counterion diffusion coefficients were determined from free solution equivalent conductance data. All other parameters were determined experimentally for a Nafion (of E. I. du Pont de Nemours Inc.) cation‐exchange membrane and five 0.1 M alkali metal sulfate solutions. Experimental radiotracer data for coion absorption as well as for coion and water transport are compared with theoretical predictions to test the accuracy of the model.