bluuebunny/crossref_metadata_2025_split huggingface dataset:
The dispersion of discrete particles in a turbulent fluid field
Authors: Calabrese Richard V. , Middleman Stanley 
Published: June 2004

AbstractThe degree of radial dispersion of medium size particles (ηK < dp < lf) emanating from a point source, is measured photographically in the turbulent core of a fully developed vertical pipe flow of water. From the classical theoretical results of G. Taylor, it was then possible to calculate statistical parameters which characterize the turbulent particle motion. A comparison is made between a tracer and neutrally dense, buoyant and heavy particles. Results indicate that the effect of particle intertia is negligible, and that the crossing trajectories effect dominates the dispersion process. A “wake effect” causes a buoyant particle to disperse to a greater degree than an equivalent heavy particle. An exponential‐cosine form of the Lagrangian autocorrelation coefficient provides a best fit for the dispersion data, although a purely exponential form is equally adequate for practical calculations.
A justification of the internal isothermal model for gas‐solid catalytic reactions
Authors: Pereira Carmo J. , Wang Jenshi B. , Varma Arvind 
Published: June 2004

AbstractThe commonly employed internal isothermal model for gas‐solid catalytic reactions, wherein the pellet is assumed internally isothermal but with internal concentration gradient, is justified by analyzing the full non‐isothermal diffusion‐reaction equations as an appropriate perturbation problem (β small, and Bih/β finite). The internal isothermal model is shown to be the zeroth order solution of the perturbation problem. Analytic expressions for the first order corrections are given for a first order reaction.
Heat transfer to a stationary sphere in a plasma flame
Authors: Sayegh N. N. , Gauvin W. H. 
Published: June 2004

AbstractThe overall heat transfer rates to stationary spheres of highly‐polished molybdenum (2 to 5.6 mm in diameter) in a confined argon plasma jet were experimentally measured. The effects of large temperature differences and large variations of the fluid property on the heat transfer process are investigated. The sphere Reynolds number range between 10 and 80, and the sphere temperature between 1,200 K and 2,400 K, with temperature differences between the gas and the sphere in excess of 2,000 K. These conditions are within the range commonly encountered in industrial plasma processing. The experimental values of the heat transfer coefficients are in reasonably good agreement with the predictions of a theoretical analysis of variable‐property flow and heat transfer previously reported by the authors.
Bead coating instability: A comparison of speed limit data with theory
Authors: Tallmadge John A. , Weinberger Charles B. , Faust Helen L. 
Published: June 2004

AbstractBead coating geometry is used in the continuous, high‐speed coating of photographic and other films. However, bead coating suffers from instabilities occurring at maximum and minimum speeds which result in non‐uniform films and unsatisfactory coating. This article describes an experimental study of these speeds for a range of flowrates, gaps, and viscosities. Results are compared with theory.
Entrance region (Lévêquelike) mass transfer coefficients in packed bed reactors
Authors: Fedkiw Peter , Newman John 
Published: June 2004

AbstractCalculations for the high Peclet number, entrance region (Lévêquelike) packed bed, mass transfer coefficient using a sinusoidal periodically constricted tube model for the void structure of the bed are presented. An inverse cube root dependence of the mass transfer coefficient on the bed depth is predicted. This length dependence is anticipated only at very low Reynolds numbers. Calculations which assume a mixing region between successive periods are also presented. No bed length dependence is anticipated in these coefficients.
A new approach to optimization of chemical processes
Authors: Berna T. J. , Locke M. H. , Westerberg A. W. 
Published: June 2004

AbstractBased on recent work by Powell, a new optimization algorithm is presented. It merges the Newton‐Raphson method and quadratic programming. A unique feature is that one does not converge the equality and tight inequality constraints for each step taken by the optimization algorithm. The article show how to perform the necessary calculations efficiently for very large problems which require the use of mass memory. Experience with the algorithm on small problems indicates it converges exceptionally quickly to the optimal answer, often in as few iterations (5 to 15) as are needed to perform a single simulation with no optimization using more conventional approaches.
The Co‐current reactor‐heta exchanger part II. Experimental results
Authors: Degnan Thomas F. , Wei James 
Published: June 2004

AbstractA reactor of fiour crossflow nomolithic blocks is used to approximate a cocurrent and a countercurrent reactor‐heat excanger. Essentailly isothermal reaction pass profiles are produced by flowing the coolant and reactant streams cocurrent to each other according to the criteria set down in Part I of this paper. A multiplicy of steady states is shown to exist for the autothermal countercurrent mode, but not for the autothermal cocurrent mode, under identical conditions.
The influence of mixing on the antisolvent induced agglomeration and sedimentation of mineral matter in coal derived liquids
Authors: Vaidyanatan K. R. , Verhoff F. H. , Henry J. D. 
Published: June 2004

AbstractThere are several ways to remove minral matter from coal‐derived liquids: antisolvent agglomeration and subsequent sedimentation is one. Adding antisolvent to coal liquids causes asphaltenes and/or preasphaltenes in the oil to precipitate. The precipitated asphaltenes then agglomerate the paraticles, increasing the sedimentation rate. The magnitude of this increase depend no the mixing conditions used to dispers the antisolvent in the oil.This article discuss the results of sedimentation experiments performed onthe antisolvent addition to coal liquids, using an x‐ray detection system. The system has the capacity of high temperature (up to 315°C) and high pressure (up to 2.75 7 × 106 Pa). The important parameters are the mixing time, the impeller speed, and the antisolvent addition rate. These are studied in detail for the antisolvent Soltrol.
Calculation of the governing equations for a seriated unequal velocity, equal temperature two‐phase continuum
Authors: Lyczkowski Robert W. , Solbrig Charles W. 
Published: June 2004

AbstractThe governing equations describing the flow of an unequal phase velocity, equal phase temperature (UVET) seriated two‐phase continuum as derived by Solbrig and Hughes (1978) are solved in this article, in one space dimension. A simple implicit iterative solution procedure is developed to numerically evaluate the five non‐linear coupled field equations. Analytical solutions are developed, against which the computer code results are compared. The prototype UVET code results are compared to the equivalent equal phase velocity, equal phase temperature (EVET) code results for the same problem. Major phenomena such as phase flow reversal, counter‐current flow and flooding‐like behavior are predicted.
Equilibrium staged parametric pumping: Part III. Open systems at steady‐state‐McCabe‐Thiele diagrams
Authors: Grevillot Georges 
Published: June 2004

AbstractThe theory of equilibrium staged parametric pumps with discrete fluid transfers has been presented in previous papers for total reflux. Here, it is extended to open, fractionating systems, operating in cyclic steady state. The cases of and enriching section, a stripping section, and a complete fractionating apparatus are successively considered. Providing adequate variables are defined, the result is a diagram which plays the same role as the McCabe‐Thiele diagram in distillation. The optimal feed stage location, the minimum reflux, and the separation factor for given operating conditions are determined analytically and graphically in the case of linear equilibrium isotherms. The method is then generalized to non‐linear equilibria, particularly of constant relative volatility type.
Thermodynamics of microemulsions: Combined effects of dispersion entropy of drops and bending energy of surfactant films
Authors: Miller C. A. , Neogi P. 
Published: June 2004

AbstractA theory of dilute microemulsions is presented which includes for the first time both the entropy of dispersion of the drops and energy effects associated with bending the surfactant films at the drop interfaces. It yields expressions for drop size for (a) a dilute microemulsion in equilibrium with an excess bulk phase, e.g., an oil‐in‐water microemulsion in equilibrium with excess oil and (b) dilute oil‐continuous and water‐continuous microemulsions in equilibrium and containing equal amounts of surfactant. In the latter case, our theory indicates that existence of the two microemulsion phases sometimes is favored over a layered or lamellar phase, even though the “natural curvature” of the surfactant films is zero, corresponding to a perfectly flat film.
A Corresponding States equation for saturated liquid densities. II. Applications to the calculation of swelling factors of CO2—crude oil systems
Authors: Teja Amyn S. , Sandler Stanley I. 
Published: June 2004

AbstractIn an earlier article, a Corresponding States Method was presented for predicting the saturated liquid densities of both pure components and mixtures. The method is based on the known saturated liquid densities of two reference fluids and requires the critical properties and acentric factors of the pure components as input parameters. We use the method here to calculate the swelling factors of CO2‐crude oil mixtures using CO2 and n‐dodecane as the reference fluids. The critical properties and acentric factors of the crude oils were estimated from their API gravities and Watson K‐factors. Using only one adjustable coefficient to characterize each CO2‐crude oil system, swelling factors were calculated to within 0.5% of their experimental values. The single, adjustable coefficient is linearly related to the boiling point of the crude.
Gas‐adsorbate collisional effects and surface diffusion in porous materials
Authors: Thakur Subhash C. , Brown Lee F. , Haller Gary L. 
Published: June 2004

AbstractIf gas‐adsorbate momentum transfer is ignored, calculated surface fluxes within porous materials often can be grossly incorrect. Methods are introduced for including these interactions when calculating surface fluxes in permeability studies. Developments are carried out for systems with porous materials having both uniform and heterogeneous surfaces. These methods complement one developed earlier for Wicke‐Kallenbach experiments, using porous materials with uniform surfaces. Some previous studies are then considered. In one system, including gas‐adsorbate momentum transfer changes the proposed surface‐diffusion mechanism from a “hopping” phenomenon to the mobility inherent in a two‐dimensional gas. Consideration of other systems shows that, while very frequently these collisional interactions are important, experiments can occur where they are not. A criterion is developed for indicating when this momentum transfer is significant and its inclusion in surface‐flux determinations is necessary.
Observations on fixed‐bed dispersion models: The role of the interstitial fluid
Authors: Sundaresan S. , Amundson Neal R. , Aris Rutherford 
Published: June 2004

AbstractModels of the role of the interstitial fluid for dispersion in a fixed bed for very high Reynolds numbers are examined in detail to determine how well they fit the physical requirements of finite speed of signal propagation, no backmixing, conservation and correct asymptotic form. It is concluded that no linear continuous partial differential equation of finite order can satisfy all of these requirements as well as the cell model, although all models for sufficiently large axial space and time variables are very good approximations to the cell model. Some new hyperbolic models are presented and their solutions obtained and compared with the standard solutions. In present day design it appears that no model has an outstanding advantage over any other.
Experimental and analytical study of wall reaction and transport effects in fast reaction systems
Authors: Smith Geoffrey K. , Krieger Barbara B. , Herzog Peter M. 
Published: June 2004

AbstractThis paper extends previous modeling calculations of concentration profiles and reaction rates in tubular flow reactors by including very fast wall reactions such as surface catalyzed atom recombinations. The plug flow assumption is investigated and found to be valid in tubular flow reactors when the dimensionless wall reaction rate is less than on (H < 1), and the dimensionless ratio of homogeneous reaction rate to diffusion rate (Damkohler number) is greater than one (α > 1). If these criteria are not met, this work provides a correlation yielding a correction factor which can be applied to the mean residence time. The method is applied to experimental data relating to the deactivation probability of two types of atoms on teflon and quartz. Values of 1.0 + 0.2 × 10−4 and 1.7 + 0.4 × 10−4 for the deactivation probabilities of 0 and N atoms, respectively, are reported.
Adsorption of methane and several mixtures of methane and carbon dioxide at elevated pressures and near ambient temperatures on 5A and 13X molecular sieves by tracer perturbation chromatography
Authors: Rolniak Paul D. , Kobayashi Riki 
Published: June 2004

AbstractThe principles of tracer perturbation chromatography were applied to measure the sorption of pure methane and several methane‐carbon dioxide mixtures on 5A and 13X molecular sieves at near ambient temperatures to pressures in excess of 7 MPa (1 000 lb/in.2abs). The molecular sieves studied were industrial grade zeolite crystals pelleted with 20 wt % clay binder.The statistical mechanical model of Ruthven was applied to both pure methane and to several mixtures of methane rich, methane‐carbon dioxide mixtures from a few MPa (50 lb/in.2abs) to pressures as high as 10.34 MPa (1 500 lb/in.2abs) at near ambient temperature. While the theory appears to correlate the data well even at high pressures, some limitations of the theory begin to appear for the mixtures of higher dioxide concentrations.
Mass transfer in periodically cycled plate columns containing multiple sieve plates
Authors: Goss D. W. , Furzer I. A. 
Published: June 2004

AbstractA five plate distillation column, 100 mm in diameter, has been used to study both fluid mixing and the mass transfer separations of mixtures of methylcyclohexane and n‐heptane under periodically cycled conditions. Both the fluid mixing and mass transfer could be successfully analyzed using the (2S) model to describe the liquid movement in the column. Previously reported results by McWhirter and Lloyd could not be reproduced. Only moderate improvements in separating ability can be obtained with sieve plates and packed sieve plate columns operated in the cycled mode.
Semiempirical theory of surface tension of binary systems
Authors: Carey B. S. , Scriven L. E. , Davis H. T. 
Published: June 2004

AbstractSurface tensions of several binary mixtures are computed using the gradient theory of inhomogeneous fluids. The interfacial influence parameters are determined from mixing rules and pure fluid experimental tensions. A comparison of the compositional dependence of the predicted and experimental tensions indicates that the best results for nonpolar hydrocarbons are obtained from a geometric mixing rule for the influence parameter. Predicted tensions vs. composition for nonpolar systems are in excellent agreement with experiment, generally lying within 2% of observed data. Predictions are poor for alcohol solutions.
Multiplicity and stability of the hydrogen‐oxygen‐nitrogen flame: The influence of chemical pathways and kinetics on transitions between steady states
Authors: Heinemann Robert F. , Overholser Knowles A. , Reddien George W. 
Published: June 2004

AbstractNumerical bifurcation techniques are used to predict multiple steady states for a nonadiabatic, premixed hydrogen flame stabilized on a flat‐flame burner. It is found that predicted conditions for burnout and ignition vary remarkably as rival chemical niodels are selected, while conditions for a well‐stabilized flame are much less sensitive to chemical and kinetic assumptions. It is concluded that multiplicity theory can help define the chemical behavior of realistic, complex reaction‐diffusion systems.
Simultaneous melting and freezing in the impingement region of a liquid jet
Authors: Epstein Michael , Swedish M. J. , Linehan J. H. , Lambert G. A. , Hauser G. M. , Stachyra L. J. 
Published: June 2004

AbstractAn experimental investigation of an impinging water jet freezing on a melting solid surface has been carried out. Attention was focused on the stagnation region of an axisymmetric jet. In the experiment, a water jet was directed upward against the lower end of a meltable rod, having a diameter about twice that of the jet orifice. Solid octane (m.p.—56.5°C) and solid mercury (m.p.—38.9°C) served as the meltable materials. A laminar‐axisymmetric flow model was developed to describe melting heat transfer in the presence of jet solidification within the impingement region. Measurements of the melting rate and conditions for the onset of jet solidification were found to agree quite well with the values predicted with this model.
The calculation of critical points
Authors: Heidemann Robert A. , Khalil Ahmed M. 
Published: June 2004

AbstractGibb's classical theory of critical points leads to two simultaneous, nonlinear equations in the intensive variables of the critical phase. In this paper is presented a new procedure for evaluating the functions which appear in these nonlinear equations. The new procedure simplifies and permits the speeding up of the computation of critical points in multicomponent mixtures.Computations have been performed for critical points in binary and multicomponent mixtures described by the SRK equation. The methods developed will be equally applicable to other two‐constant equations of state. The equations to be solved are organized as two equations in the unknown critical temperature and specific volume for a mixture of known composition. One of the two equations, the determinant which establishes the stability limit for the mixture, is shown to be satisfied by more than one volume at a given temperature and by several temperatures at a given volume. A technique is proposed to assure that the correct temperature, volume solution can be found for this equation. For critical points in ordinary gas‐liquid systems, an overall computational procedure is suggested in which it proves to be unnecessary to provide initial guesses for either the temperature or the volume.Application has also been made to several systems with high density (liquid‐liquid) critical points.
Separation of proteins via multicolumn pH parametric pumping
Authors: Chen H. T. , Yang W. T. , Pancharoen Ura , Parisi Robert 
Published: June 2004

AbstractFractionation of protein mixtures by multicolumn pH parametric pumping is investigated theoretically and experimentally. The parapumps considered consist of a series of columns packed alternately with cation and anion exchangers. Various methods of operation of the parapumps are discussed. Two separation problems are examined: enrichment and splitting. Experimental data were obtained for two‐column systems and compared with the calculated results based on an equilibrium theory.
The separation of ethylbenzene from p‐ and m‐xylene by extractive distillation using mixtures of polychloro compounds
Authors: Berg Lloyd , Kober P. J. 
Published: June 2004

AbstractThe use of a single compound as the agent in modifying the apparent relative volatility in extractive distillation is well known. In the separation of ethylbenzene from para‐ and meta‐xylenes by extractive distillation, it was found that mixtures containing from two to four components were more effective than any known single compound. Hundreds of combinations of extractive agents were investigated in vapor‐liquid equilibrium stills, and from these, twenty‐seven different combinations of chlorinated organic compounds showed merit. The relative volatility of ethylbenzene to p‐xylene is 1.06 and to m‐xylene 1.08. The promising combinations were investigated in three glass perforated plate extractive distillation columns containing twelve, fifteen and nineteen theoretical plates, respectively. Of the twenty‐seven different extractive agents tested in the columns, sixteen yielded a relative volatility greater than 1.20. The best one, a mixture of pentachlorophenol, benzene hexachloride and 1,2,4‐trichlorobenzene, gave a relative volatility of 1.27. Other combinations approaching this relative volatility are pentachlorophenol, benzene hexachloride and 2,4‐dichlorotoluene giving 1.25 and polychlorobenzene, pentachlorophenol, benzene hexachloride and 1,2,4‐trichlorobenzene giving 1.26, when used in the ratio of two parts of extractive agent to one part of ethylbenzene‐xylene mixture. All the extractive agents boil sufficiently above xylene to make their recovery by distillation easy and complete. Life studies showed no excessive decomposition of any of them while in use.
Rate parameters for adsorption of CO2 in beds of carbon particles
Authors: Andrieu J. , Smith J. M. 
Published: June 2004

AbstractAdsorption equilibrium constants and intraparticle diffusivities were determined for the adsorption of carbon dioxide on an activated carbon derived from bituminous coal particles. The moment method was used to extract these results from pulse‐response measurements for beds of carbon particles. The activated carbon had a very broad pore‐size distribution: average radius of micropores was 11Å and macropores 3750Å. Bulk molecular and Knudsen diffusion could not explain mass transfer in the micropores. An activated surface migration concept (Chihara et al., 1978) did give reasonable results. The adsorption rate was also significantly retarded by intraparticle diffusion in the macropores.
Substrate‐inhibited kinetics with catalyst deactivation in an isothermal CSTR
Authors: Do Duong D. , Weiland Ralph H. 
Published: June 2004

AbstractAnalytical expressions are developed for the time‐dependent reactant concentration and catalyst activity in an isothermal CSTR with Langmuir‐Hinshelwood kinetics of deactivation and reaction. Several parallel and series posioning mechanisms are considered for a reactor which, without poisoning, would operate at a unique steady state. The use of matched asymptotic expansions and abandonment of the usual initial‐steady‐state assumption give results, valid from startup to final loss of activity, whose accuracy can be improved systematically.
Determination of interaction second virial coefficients; He‐CO2 system
Authors: Holste J. C. , Watson M. Q. , Bellomy M. T. , Eubank P. T. , Hall K. R. 
Published: June 2004

AbstractWe have obtained values for interaction second viral coefficients of the helium‐carbon dioxide system in the range 230 ⩽ T/K ⩽ 300. Our experimental technique is essentially the Burnett mixing method described by Hall and Eubank (1973, 1974). We have modified the analysis to account for higher‐order effects and to detect significant systematic errors. We also report virial coefficients for the pure components: helium in the range 100 ⩽ T/K ⩽ 300 and carbon dioxide at 300 K.