bluuebunny/crossref_metadata_2025_split huggingface dataset:
A general expression for the correlation of rates of transfer and other phenomena
Authors: Churchill S. W. , Usagi R. 
Published: June 2004

AbstractThe expression Y = (1 + Zn)1/n where Y and Z are expressed in terms of the solutions for asymptotically large and small values of the independent variable is shown to be remarkably successful in correlating rates of transfer for processes which vary uniformly between these limiting cases. The arbitrary exponent n can be evaluated simply from plots of Y versus Z and Y/Z versus 1/Z. The expression is quite insensitive to the choice of n and the closest integral value can be chosen for simplicity. The process of correlation can be repeated for additional variables in series. Illustrative applications are presented only for flow, conduction, forced convection, and free convection, but the expression and procedure are applicable to any phenomenon which varies uniformly between known, limiting solutions.
A self‐adapting time‐optimal control algorithm for second‐order processes
Authors: Hsu E. H. , Bacher S. , Kaufman A. 
Published: June 2004

AbstractA method for performing time‐optimal control with only limited prior knowledge of specific process dynamics is described. The time constants of the process are identified during the transient period accompanying the desired set point change, and the valve switching times of the control algorithm are calculated based on these time constants. The adaptive features of this method make its use independent of process or operating variation. The effectiveness of the proposed control method was evaluated using digital simulation and experimental techniques. The experimental phase which involved random changes to the temperature set point of a batch reactor was carried out with the aid of an on‐line digital computer.
Diffusion studies of CO2, NO, NO2, and SO2 on molecular sieve zeolites by gas chromatography
Authors: Ma Yi Hua , Mancel Claude 
Published: June 2004

AbstractGas chromatographic techniques were used to measure the diffusion coefficients and the isosteric heats of adsorption of CO2, NO, NO2, and SO2 on 5A and 13X molecular sieves, natural mordenites, and synthetic Na‐ and H‐mordenites in the temperature range of 133 to 325°C. Diffusional resistances for all gases studied decrease in the following order: natural mordenites > Na‐mordenites > H‐mordenites > (13X, 5A) indicating the increased ease of flow in the 3‐dimensional network. Isosteric heats of adsorption (range from 3 kcal/mole to 12 kcal/mole) and activation energies (range from 3 kcal/mole to 19 kcal/mole) decrease in the same order. The variations of diffusion coefficients, heats of adsorption, and activation energies are discussed in terms of the interaction between the surface and gas molecules as well as the openings of the pores relative to the size of the diffusing molecules.
Effects of surface active agents on mass transfer during droplet formation, fall, and coalescence
Authors: Skelland A. H. P. , Caenepeel C. L. 
Published: June 2004

AbstractThis experimental study shows effects of anionic and cationic surface active agents on mass transfer during drop formation, fall, and coalescence for both continuous and disperse phase‐controlled systems. Three dispersion nozzles, mounted with 1.906 cm equilateral pitch, and a 5.08 cm I.D. extraction column were used to simulate certain conditions in commercial liquid‐liquid extraction units.The surfactant effects on extraction were pronounced, frequently reducing transfer to 10% of that in uncontaminated systems, with marked minima at intermediate concentrations of surfactant. In contrast, the continuous phase coefficient during coalescence was substantially increased by surfactants, with maxima in some cases.
Generalized multicomponent equation for activity coefficient calculation
Authors: Chien Henry H. Y. , Null Harold R. 
Published: June 2004

AbstractA new model for the prediction of liquid phase activity coefficients used for predicting multicomponent phase equilibria is presented and compared with presently available methods for making these calculations. In its binary form, the new model includes Margules, van Laar, NRTL, Scatchard‐Hamer, and Fariss models as special cases. In its multicomponent form the van Laar, Margules, and Scatchard‐Hamer forms are different from and superior to the Wohl expansion. It is also possible with the new model to use different special case models for each of the binary pairs.
Use of Monte Carlo in calculating the thermodynamic properties of water clathrates
Authors: Tester Jefferson W. , Bivins Robert L. , Herrick C. C. 
Published: June 2004

AbstractEquilibrium dissociation pressures for monovariant three‐phase (icesolid clathrate‐gas) systems were predicted for water clathrates with Ar, Kr, Xe, N2, O2, CO2, and CH4as the guest molecules. A Monte Carlo approach of statistically sampling the states available to the guest molecule inside the host water cage was used to evaluate the configurational properties including the free volume integral. The Lennard‐Jones 6–12 potential adequately described the guest‐host interaction for monatomic species, for example, Ar, Kr, and Xe, while the nonspherically symmetric Kihara potential with a fixed hard‐core geometry was required for polyatomic guests. The simulated motion of the guest within the cell was consistent with the geometrical features of the host lattice.
Correspondling states correlations for liquid compressibility and partial molal volumes of gases at infinite dilution in liquids
Authors: Brelvi S. W. , O'Connell J. P. 
Published: June 2004

AbstractA statistical mechanical solution theory is used as the basis for corresponding states formulations. Universal functions relate the compressibility to the reduced density and the partial molar volume to reduced solvent density only. Correlations are in good agreement with data for all types of nonelectrolytes over wide ranges of temperatures including saturated and compressed systems. The correlations provide simple methods for describing the isothermal pressure dependence of liquid volumes and the pressure dependence of the ideal‐solution solubility of gases in liquids.
A model for evaporation of a multicomponent droplet
Authors: Newbold Fred R. , Amundson Neal R. 
Published: June 2004

AbstractThe object of this study was to derive a model which would accurately describe the evaporation of a multicomponent droplet, especially near its boiling point. The model is derived and is shown to have the following properties: the transport of one component can be augmented by the bulk (Stefan) flow of the other components, and the droplet can never exceed its boiling point, a property not realized by previous models. The ordinary differential equations which constitute the model were integrated numerically, and results are given for both two‐ and three‐component droplets.
Suboptimal feedback control of distributed systems: Part 1. Theoretical developments
Authors: Vermeychuk J. Gregory , Lapidus Leon 
Published: June 2004

AbstractA new method for suboptimal feedback control of certain classes of distributed systems based on successive instantaneous minimization of the performance functional kernel is presented. This method is applicable to both linear and nonlinear systems.The Lyapunov functional approach is extended to distributed systems, yielding two new suboptimal feedback control techniques. Also, an application of multilevel bang‐bang control to the first‐order hyperbolic system is presented and generalized.Advantages and disadvantage ofthe suboptimal control techniques vis á vis open loop optimal control methods are listed, as well as comparative features of the suboptimal control methods.
Miscible displacement with combined free and forced convection: Laminar flow in a vertical tube
Authors: Posner Martin , Gill William N. 
Published: June 2004

AbstractAn approximate analysis is given for miscible displacement in vertical tubes when density differences between the displaced and displacing fluids give rise to buoyancy forces which affect the velocity distribution significantly. The results of this analysis agree with the available experimental data fairly uniformly over the range of parameters studied experimentally.By analogy with studies of heat transfer in vertcal tubes it is concluded that both cases studied, when a lighter fluid displaces a heavier fluid in upflow, or when the heavier fluid is below the lighter fluid, are potentially unstable flows because buoyancy forces can create points of inflection in the velocity profile; stagnation at the wall also is predicted for upflow when the lighter fluid is on the bottom initially, and this has been observed to induce a sudden transition to turbulence in heat transfer systems.Buoyancy forces reduce the extent of dispersion by flattening the velocity profile when the heavier fluid is on the bottom in upflow. The velocity profile is elongated and the dispersion coefficient is increased when the bottom fluid is lighter than the one it displaces in upflow.
Prediction of adsorption at liquid‐solid interface from adsorption isotherms of pure unsaturated vapors
Authors: Sircar S. , Myers A. L. 
Published: June 2004

AbstractAdsorption from liquid mixtures can be predicted from the adsorption isotherm of the pure unsaturated vapor, measured for each component of the liquid mixture. The theory gives analytical expressions for adsorption from liquids corresponding to Type I (finite capacity) and Type II (multilayer adsorption) vapor isotherms. The free energy of immersion of the adsorbent in the pure liquid adsorbate is the essential parameter for either type of adsorption. Predictions based upon the assumption of an ideal adsorbed solution are compared with experimental data on adsorption from liquid mixtures.
Flow rate‐pressure gradient measurements in periodically nonuniform capillary tubes
Authors: Dullien Francis A. L. , Azzam Mohamed I. S. 
Published: June 2004

AbstractFlow rate‐pressure gradient measurments have been performed on 15 different test capillary tubes, each of which consisted of short, alternating segments of two different diameters. The Reynolds number range covered extended from 2 to 700, based on the conditions in the narrower capillary segment. Darcy's law was found valid up to about Re = 30‐50, whereas the Forchheimer equation described the data over the entire range of Re covered. The Forchheimer equation has been obtained from a nondimensional form of the volume averaged momentum equation by using the averaging theorem due to Slattery and to Whitaker. The parameters α and β have obtained precise hydrodynamic definitions. The experimental data have been treated in terms of the Forchheimer equation: the parameters α and β have been calculated using various definitions for the area of flow. Dimensionless permeability, equal to the ratio of measured‐to‐Poiseuille permeability has been found to be a minimum‐type function of small‐to‐large capillary diameter ratio. Dimensionless inertial parameter β* has been found to be a maximum‐type function of the capillary diameter ratio, if the calculation was based on the area of flow equal to the cross sectional area of the narrower capillary segment, in every case. The maximum occurred at the same value of the capillary diameter ratio as the minimum for the dimensionless permeability.
Thermodynamic properties of strong electrolytes in aqueous solutions
Authors: Bromley Leroy A. 
Published: June 2004

AbstractA generalized analytic correlation is presented for activity coefficient. osmotic coefficient, enthalpy, and heat capacity of single and multicomponent strong aqueous solutions. A good correlation for each salt to an ionic strength of six is obtained by assigning a single parameter “B” value to each salt. These B values are well approximated by assigning two parameters for each ion. Values presented for the common ions at 25°C allow the estimation of activity and osmotic coefficients of many unmeasured salt solutions.
Restricted diffusion in binary solutions
Authors: Newman John , Chapman Thomas W. 
Published: June 2004

AbstractDiffusion coefficients of binary solutions can be measured accurately by observation at long times of isothermal diffusion in a vertical cell closed at the ends (restricted diffusion). The present analysis, which accounts for the effects of solvent flux and variable solution properties, demonstrates that the experiment yields a well‐defined, differential diffusion coefficient, even in concentrated solutions.Observation is effected by Rayleigh interference optics, and results for aqueous potassium chloride solutions confirm the accuracy of the method.
Prediction of thermodynamic properties for low temperature hydrocarbon process calculations
Authors: Lee Byung‐Ik , Erbar John H. , Edmister Wayne C. 
Published: June 2004

AbstractAnalytical expressions for calculating vapor‐liquid compositions, enthalpies, and entropies have been developed for hydrocarbon mixtures containing none or some of the nonhydrocarbon gases and evaluated against experimental measurements of vapor‐liquid equilibria and enthalpies. The evaluation results show that the proposed equations can be applied over wide range of conditions with good accuracy. These equations are extensions and improvements of equations presented previously by Lee and Edmister (1971c) mainly for low temperature thermodynamic property calculations.
Manufacture of silicon tetrachloride from rice hulls
Authors: Basu Prabir K. , King C. Judson , Lynn Scott 
Published: June 2004

AbstractRaw rice hulls contain about 20% silica in very finely dispersed form. Pyrolyzed hulls can be chlorinated at 1000°C to give a nearly quantitative yield of silicon tetrachloride free of most other inorganic chlorides. Solid, organic, chlorine‐containing species have been found to be reaction intermediates. Commercial application appears economically attractive.
Adsorption from ternary liquid mixtures on solids
Authors: Minka Charles , Myers Alan L. 
Published: June 2004

AbstractThe theory of adsorption from binary liquid mixtures on solids is extended to an arbitrary number of components. An equation for the surface excess is derived in terms of the free energy of immersion of the adsorbent, the capacity of the adsorbent at saturation, and activity coefficients in the bulk and adsorbed phases.Experimental data are reported for adsorption from binary and ternary liquid mixtures of benzene, ethyl acetate, and cyclohexane on activated carbon at 30°C. These systems exhibit nonidealities in the adsorbed phase. The theory provides accurate estimates of adsorption from the ternary mixture using data for adsorption from binaries.
Radiation profiles in an empty annular photoreactor with a source of finite spatial dimensions
Authors: Irazoqui Horacio A. , Cerdá Jaime , Cassano Alberto E. 
Published: June 2004

AbstractA model of radiant energy emission for tridimensional sources has been developed and used to predict radiation flux density profiles in an annular photochemical reactor. This paper presents results for a reactor without dispersion or absorption effects; that is, reflexions and refractions have been neglected and the energy has been assumed to propagate in a transparent medium.Computed radiation profiles agree well with published experimental data in a similar lamp‐reactor set up.Also, the formulation does not introduce, as it is the case with all line models, any form of singularities in the prediction of radiation flux density values.Finally, a parametric study of the effects of lamp dimensions on the shape of the radiation profiles was also made.
Correlation and prediction of gaseous diffusion coefficients
Authors: Marrero T. R. , Mason E. A. 
Published: June 2004

AbstractA new correlation method for binary gaseous diffusion coefficients from very low temperatures to 10,000 K is proposed based on an extended principle of corresponding states, and having greater range and accuracy than previous correlations. There are two correlation parameters that are related to other physical quantities and that are predictable in the absence of diffusion measurements. Quantum effects and composition dependence are included, but high‐pressure effects are not. The results are directly applicable to multicomponent mixtures.
Volumetric properties of supercritical ethane‐n‐heptane mixtures: Molar volumes and partial molar volumes
Authors: Wu P. C. , Ehrlich Paul 
Published: June 2004

AbstractMolar volumes were measured and partial molar volumes were calculated in the supercritical region, including the vicinity of the critical locus, lor compositions of 1.8 to 20 mole % n‐heptane. Molar volumes can he represented, to a reasonable approximation, by the Flory‐OrwollVrij (FOV) reduced equation of state. A better fit of the data is possible if the three exponents in the FOV equation are adjusted The irodified FOV equation or the Redlich‐Kwong equation, with parameters idjusted to fit the critical locus, can in general represent the partial molar rolumcs adequately along the critical locus only. The prediction of the imposition‐dependence of the partial molar volumes is only qualitatively successful at best.
Volumetric properties of supercritical ethanen‐n‐heptane mixtures: The isothermal compressibility in the critical region
Authors: Ehrlich P. , Wu P. C. 
Published: June 2004

AbstractThe isothermal compressibility (at constant composition x) kT,x, was calculated in the neighborhood of the critical locus for seven mixtures containing 3.5 to 19.6 mole % heptane and analyzed in terms of the reduced pressure variable σ = (P – P̂)/P̂ where P̂ is the pressure at which kT,x becomes very large. The data can be represented by the equation kT,x = const. σ−λ along the critical isotherm and one near it and by the locus P̂(T). λ was found to be a strong function of x. The divergence of the isothermal compressibility of the mixtures near the critical locus is in conflict with predictions from classical equations of state but in accordance with modern concepts of the critical region.
Separations via semicontinuous parametric pumping
Authors: Chen H. T. , Reiss E. H. , Stokes J. D. , Hill F. B. 
Published: June 2004

AbstractA semicontinuous parametric pump with batch operation during one half‐cycle and continuous operation in the other half‐cycle was experimentally investigated using the model system toluene‐n‐heptane on silica gel adsorbent. A mathematical model based on an equilibrium theory is presented and is found to be in good agreement with the experimental results. Furthermore, it is shown that when the penetration distance for the cold cycle is less than or equal to that of the hot cycle and the height of the column, the rate of production of pure solvent by this pump may become quite large compared to the rate of production by a pump in which operation is continuous during both half‐cycles.
Reaction with mole changes in porous catalysts in the molecular, transition, and Knudsen regimes
Authors: Abed Ran , Rinker Robert G. 
Published: June 2004

AbstractEquations are derived and solved numerically for the intrapellet pressure and composition profiles in porous catalysts. The extended dusty‐gas model is used to describe the transport for a zero‐order, irreversible reaction with mole changes. Results agree with other models in the purely Knudsen and molecular regimes. In the transition region, however, the effectiveness factor is a function of five dimensionless parameters. The calculations predict a significant pressure gradient in the Knudsen regime and transition region but an insignificant gradient in the molecular regime for reactions with mole changes. Since many industrial catalysts operate in the transition region of transport, these calculations are highly desirable in reactor design.
Perturbation methods for calculating properties of liquid mixtures
Authors: Gubbins Keith E. 
Published: June 2004

AbstractPerturbation methods relate thermodynamic and transport properties of the system of interest (gas or liquid) to the known properties of some reference system; commonly used reference substances are hard sphere fluids and argon. Developments since 1967 are reviewed for both types of approach, with emphasis on applications to liquid mixtures of practical interest. Calculations for liquid mixtures of simple and complex molecules, gas solubility in liquids, fused salts, electrolytes, solvent extraction systems, and liquid metals are reviewed.
Diffusion in high viscosity liquids
Authors: Hiss Timothy G. , Cussler E. L. 
Published: June 2004

AbstractThe diffusion coefficients D of n‐hexane and of naphthalene in a series of hydrocarbon liquids with viscosities μ from 5 · 10−4 to 5 kg m−1 sec−1 (0.5 to 5000 centipoise) have been measured at 25°C with a one Savart plate wavefront‐shearing interferometer. This apparatus allows direct determinations at effectively infinite dilution. The values obtained suggest that for a small solute diffusing in a large solvent

a result consistent with earlier studies. The exponent of 2/3 may be rationalized on the basis of the Eyring rate theory.
Diffusion in aqueous nitric acid solutions
Authors: Nisancioḡl̄ū Kemal , Newman John 
Published: June 2004

AbstractThe restricted diffusion method is employed to measure the differential diffusion coefficients of nitric acid in water at 25°C for the concentration range 0.033 to 9.25 molar. The concentration gradients of diffusing solutions are observed by Rayleigh interference optics.Experimental transport data are analyzed within the framework of the concentrated solution theory of electrolytes in order to elucidate the macroscopic transport characteristics of nitric acid in terms of specific binary interactions in solution. The results indicate that the transport properties of nitric acid are largely determined, as in other strong acids, by the hydrogen ion‐water molecule interaction.
The effect of applied force on drainage of the film between a liquid drop and horizontal surface
Authors: Hartland S. , Wood S. M. 
Published: June 2004

AbstractThe effect of applied force, drop volume, and physical properties on the rate of thinning of the draining films above and below a drop trapped between two horizontal surfaces has been examined theoretically and experimentally. The variation in film thickness with position and time has been obtained photographically and from capacitance measurements. The observed rate of film thinning may be predicted by the simple uniform film model with one immobile surface and, surprisingly, decreases when the applied force and drop volume increases.
Hollow fiber reverse osmosis systems analysis and design
Authors: Gill William N. , Bansal Bihari 
Published: June 2004

AbstractA predictive model of hollow fiber reverse osmosis systems is developed using the equivalent annulus assumption. The fraction of feed recovered Φ depends on five parameters. Optimum values exist for the ratio of the inside to outside fiber radius ri/ro and for the outside fiber radius ro. For dilute systems, a simple closed form expression is obtained for Φ which enables one to determine optimum values easily.The effects of pressure, temperature, flow rate, concentration, viscosity of the feed, system length, membrane rejection parameter, and number of fibers are studied. Countercurrent is superior to concurrent operation.
Dropwise condensation phenomena
Authors: Wilkins David G. , Bromley Leroy A. 
Published: June 2004

AbstractDropwise condensation of water vapor on long vertical tubes was investigated as to in situ cleaning and promoting techniques for a variety of tube materials.Excess promoter on the tube surface significantly reduces heat transfer but appears to be slowly removed by draining.Measured steamside heat transfer coefficients for copper, gold, Admiralty, Cu‐Ni 90‐10, and Monel tubes are adequately correlated by the theory of Mikic (1969) modifide to include the effect of wall thickness.A photographic study revealed that falling drops are elongated into rivulets on long vertical surfaces. Short (< 65 mm) rivulets and small, barely visible drops over most of the area are evidence of excellent dropwise condensation.