bluuebunny/crossref_metadata_2025_split huggingface dataset:
Self‐generated oscillations in continuous crystallizers: Part II. An experimental study of an isothermal system
Authors: Song Y. H. , Douglas J. M. 
Published: June 2004

AbstractAn experimental study was undertaken to verify the theoretical predictions that for a certain range of operating conditions an isothermal crystallizer would produce oscillating outputs even when the inputs were maintained constant. An interesting feature of the results is that even though a power‐law model and Volmer's model for nucleation kineties provided equivalent descriptions of the steady state data, predictions of transient responses based on Volmer's equation were much better than the power‐law results, and the observed behavior of the oscillating system was described well with Volmer's expression, whereas the power‐law equation predicted that the system would not oscillate.
Flow phenomena in stirred tanks. Part I. The impeller stream
Authors: Günkel Alfred A. , Weber Martin E. 
Published: June 2004

AbstractFlow parameters were measured in a baffled, turbulent, stirred tank agitated by a six‐blade, disk style turbine. The working fluid was air. Mean and fluctuating velocities were measured between the blades of the impeller with a probe mounted on the spinning impeller. Mean velocities, turbulent velocities, one‐dimensional energy spectra, and Eulerian autocorrelation functions were measured in the impeller stream by using the shielded hot‐wire anemometer of Gunkel et al. (1971) which permits the measurement of turbulence parameters in flows of very high turbulence intensity. Reliable impeller pumping capacities were obtained yielding Qrad/ND3 = 1.0 at the impeller periphery. An energy balance on a control volume containing the impeller and the impeller stream showed that the energy put into the tank via the impeller appeared as a net efflux of kinetic energy leaving the control volume. Therefore, most of the energy input to the tank is dissipated in the bulk of the tank.
Nonlinear theory of free coating onto a vertical surface
Authors: Esmail M. Nabil , Hummel Richard L. 
Published: June 2004

AbstractThe work of Landau and Levich (1942) initiated detailed theoretical and experimental study of the flow of the thin liquid film entrained by a steady withdrawal of a sheet from a bath of liquid. The existing theories, which differ considerably, are all based on linearization of the problem and give single relationships between film thickness T and a capillary number Ca. The present paper demonstrates theoretically that differing physical properties for each liquid result not in a single curve but in a family of curves for T vs. Ca and that the complete set of previous experimental work required and fitted the family of curves. Previous theories could fit only a portion of this experimental data.The solution requires a nonlinear theory to include inertial terms and two‐dimensional flow and thus treat the parameter of liquid physical properties. This is obtained by applying a nonlinear approach based on the direct method of Galerkin. Owing to the nonlinear character of the solution, the new theory has the advantage of accurately determining the shape and size of the upper meniscus profile. Excellent agreement with the complete set of available experimental data is obtained.
Numerical treatment of laminar flow in helically coiled tubes of square cross section. Part I. Stationary helically coiled tubes
Authors: Joseph B. , Smith E. P. , Adler R. J. 
Published: June 2004

AbstractNumerical solution of steady laminar flow in helically coiled tubes of square cross section for Dean numbers from 0.8 to 307.8 reveal two regimes of secondary flow. Up to Dean number of 100, the expected secondary flow pattern appears with twin counterrotating vortices. Above Dean numbers of 100, a new secondary flow regime, reported here for the first time, appears with four vortices. Flow visualization and pressure drop experiments confirm the transition.
Drug permeation through human skin: Theory and invitro experimental measurement
Authors: Michaels A. S. , Chandrasekaran S. K. , Shaw J. E. 
Published: June 2004

AbstractThe penetration of drugs and other micromolecules through intact human skin can be regarded as a process of dissolution and molecular diffusion through a composite, multilayer membrane, whose principal barrier to transport is localized within the stratum corneum. A mathematical model of the stratum corneum as a two‐phase protein‐lipid heterogeneous membrane (in which the lipid phase is continuous) correlates the permeability of the membrane to a specific penetrant with the water solubility of the penetrant and with its lipid‐protein partition coefficient.Experimentally measured permeabilities of human skin to a variety of drugs have been found to conform to this model. The extraordinarily low permeability of skin to most micromolecules appears to arise from the very low diffusivity of such molecules in the intercellular lipid phase.
Thermal cracking of propane and propane‐propylene mixtures: Pilot plant versus industrial data
Authors: Van Damme P. S. , Narayanan S. , Froment G. F. 
Published: June 2004

AbstractThe product distribution and kinetics of the thermal cracking of propane and propane‐propylene mixtures were investigated for a temperature range of 700° to 850°C, exit total pressures from 1.2 to 2 atm. absolute, and steam dilutions of 0.4 and 1.0. The reaction kinetics were determined by two methods. The first uses the equivalent reactor volume concept to reduce the data to isothermicity before attempting the kinetic analysis. The second determines the parameters directly from the nonisothermal data by means of a search routine. Both methods led to a reaction order of 1. The effect of propylene addition was also investigated. Finally, a detailed molecular reaction scheme was derived from a nonisothermal and nonisobaric simulation of the cracking experiments. This scheme was used in the simulation of an industrial cracker and led to excellent agreement, in particular of the product distribution.
Group‐contribution estimation of activity coefficients in nonideal liquid mixtures
Authors: Fredenslund Aage , Jones Russell L. , Prausnitz John M. 
Published: June 2004

AbstractA group‐contribution method is presented for the prediction of activity coefficients in nonelectrolyte liquid mixtures. The method combines the solution‐of‐functional‐groups concept with a model for activity coefficients based on an extension of the quasi chemical theory of liquid mixtures (UNIQUAC). The resulting UNIFAC model (UNIQUAC Functional‐group Activity Coefficients) contains two adjustable parameters per pair of functional groups.By using group‐interaction parameters obtained from data reduction, activity coefficients in a large number of binary and multicomponent mixtures may be predicted, often with good accuracy. This is demonstrated for mixtures containing water, hydrocarbons, alcohols, chlorides, nitriles, ketones, amines, and other organic fluids in the temperature range 275° to 400°K.
Interactions between catalytic hydrodesulfurization of thiophene and hydrodenitrogenation of pyridine
Authors: Satterfield Charles N. , Modell Michael , Mayer Jerome F. 
Published: June 2004

AbstractPyridine hydrodenitrogenation (HDN) is more difficult than thiophene hydrodesulfurization (HDS), and there is a thermodynamic limitation on the first step of the HDN reaction mechanism which occurs, for example, at 5 to 11 bars, at temperatures above about 350°C. Pyridine inhibits the HDS reaction as previously reported, but sulfur compounds have a dual effect on HDN. At low temperatures, thiophene inhibits the reaction by competing with pyridine for hydrogenation sites on the catalyst. This retards the hydrogenation of pyridine to piperidine, reducing the overall reaction rate. At high temperatures the dominant effect is interaction of hydrogen sulfide, an HDS reaction product, with the catalyst to improve its hydrogenolysis (hydrocracking) activity. This increases the rate of piperidine hydrogenolysis, which is rate determining at the latter conditions, and enhances the overall rate of HDN.
A new technique for collecting binary vapor‐liquid equilibrium data without measuring composition: The method of intersecting isochores
Authors: Hall Kenneth R. , Eubank Philip T. , Myerson Allan S. , Nixon William E. 
Published: June 2004

AbstractThe Burnett coupled isochoric PVT experiment possesses many advantages for determining volumetric properties. In this study, we suggest that it also provides an excellent vehicle for determining VLE data. Incorporating a magnetic densimeter into the apparatus encompasses a VLE experiment in which the phases are not sampled to determine composition. Material balances allow composition calculation; the Gibbs‐Duhem equation is not necessary and thus remains available for consistency checks.
Electroosmosis and electrolyte conductance in charged microcapillaries
Authors: Koh Wei‐Hu , Anderson John L. 
Published: June 2004

AbstractInteractions between the electrostatic double layer and transport rates in long capillary pores were investigated experimentally. Track‐etched mica sheets with extremely narrow pore size distribution and large length‐toradius ratio were used as model membranes to examine the electrokinetic phenomena enhanced conduction and electroosmosis as a function of pore size and electrolyte (potassium chloride) concentration. Of experimental significance was that the capillary pores were of radius comparable to or even less than the solution Debye length parameter even at moderate (10−4 – 10−3 M) electrolyte concentrations. Heparin, a negatively charged polyelectrolyte, was adsorbed to the pore wall to augment electrostatic effects. The data were compared with numerical calculations based on a diffuse double‐layer model, and the unknown pore wall charge densities were computed for each experiment. The results show that the classical analysis is somehow deficient and also that adsorption of the potential determining ion (heparin) is dependent on electrostatic potential at the pore wall.
Correlation and prediction of gas‐liquid holdups in inclined upflows
Authors: Greskovich E. J. , Cooper W. T. 
Published: June 2004

AbstractA correlation is developed for predicting in‐situ (or true) liquid holdups for two‐phase, gas‐liquid slug flows in inclined pipes. The correlation is based on experimental data collected in pipes ranging from 2.54 to 7.94 cm in diameter with the air‐water system used.The experimental data used to develop the correlation were collected at zero input liquid qualities, as previously discussed by Greskovich (1973), and extended over the entire range. These data revealed little diameter effect on holdup for diameters greater than 2.54 cm but a marked effect of angle of inclination. Predicted holdup values show good agreement with experimental data.
A model for predicting flow regime transitions in horizontal and near horizontal gas‐liquid flow
Authors: Taitel Yemada , Dukler A. E. 
Published: June 2004

AbstractModels are presented for determining flow regime transitions in two‐phase gas‐liquid flow. The mechanisms for transition are based on physical concepts and are fully predictive in that no flow regime transitions are used in their development. A generalized flow regime map based on this theory is presented.
Solubilities of ethylene and other organic solutes in liquid, low‐density polyethylene in the region 124° to 300°C
Authors: Maloney D. P. , Prausnitz J. M. 
Published: June 2004

AbstractGas‐liquid chromatography was used to measure the solubilities of ethylene, n‐butane, vinyl acetate, n‐hexane, benzene, toluene, and n‐octane in three different samples of liquid, low‐density polyethylene. Solubilities in the different samples are similar. A correlation is presented for estimation of solubilities of nonpolar solutes in liquid polyethylene.
Solubility of gases and liquids in molten polystyrene
Authors: Stiel Leonard I. , Harnish Daniel F. 
Published: June 2004

AbstractExperimental solubility data have been obtained for sixteen organic solutes in molten polystyrene by a gas chromatographic procedure for temperatures from 408° to 503°K and pressures to 4 atm. The effects of diffusion and adsorption of the solute on the substrate were considered. The Henry's law constants resulting from this study and those obtained by other investigators were related to the reduced temperature. The effect of pressure on the Henry's law constants is also discussed, and a relationship is presented for the heat of solution.
Convective instabilities in porous media with through flow
Authors: Homsy George M. , Sherwood Albert E. 
Published: June 2004

AbstractThe stability of a thermally stratified, saturated porous media through which mass is being ejected is considered theoretically. The stability parameter is a flow modified D'Arcy‐Rayleigh number and is a function of a single scalar variable, the dimensionless through‐flow strength. Results of both linear and energy theory are given, and it is seen that the fluid can lose stability by either a buoyantly driven mode or by a continuous analogue of the Saffman‐Taylor mode.
Surface reaction with combined forced and free convection
Authors: Chang Ching‐Yuan , Guin James A. , Roberts Loy D. 
Published: June 2004

AbstractThe influence of combined forced and free convection on the surface reaction of a laminarly flowing species in a rectangular channel is studied. The free convective motion, which is superimposed upon the main axial flow, arises from a transverse density gradient produced by the release of a reaction product, or heat, at the channel wall. A numerical stream function‐vorticity method is employed to solve the three‐dimensional conservation equations in the case of large Schmidt number. Effects of aspect ratio, diffusivity ratio, surface reaction rate, and Rayleigh number upon the overall reactant conversion rate and local Sherwood number are examined. Reasonable agreement is obtained with experimental data for a hydrochloric acid‐calcium carbonate surface reaction.
Drop size distributions and coalescence frequencies of liquid‐liquid dispersions in flow vessels
Authors: Coulaloglou C. A. , Tavlarides L. L. 
Published: June 2004

AbstractA flash photomicrographic method and modified dye‐light transmittance technique are employed to measure size distributions and mixing frequencies in a turbulently agitated flow vessel. This liquid‐liquid dispersion is nearly spatially homogenous. Mixing frequencies are strongly dependent on impeller speed and moderately dependent on holdup fraction.
Practical realizations in process modeling: Part I. A new approach to practical realization
Authors: Jayaraman Krishnamurthy , Lapidus Leon 
Published: June 2004

AbstractA new approach is presented for the construction of linear, low‐order stable, state‐variable, dynamic models from experimental pulse response data of process systems: the problem of practical realization. This problem is solved by deriving and implementing constraints in the estimation of Markov parameters which are input to a realization algorithm. This is accomplished sequentially by using an algorithm for recursive partial realization. Bounds on the Markov parameters are derived from qualitative information about the smoothness of the response curve and used in a stagewise regression procedure. The presente procedure identifies the faster modes first; hence the tail of the pulse response, if inordinately long and inaccurate, may be ignored while lower‐order partial realizations are constructed.
A multicomponent film model incorporating a general matrix method of solution to the Maxwell‐Stefan equations
Authors: Krishna Rajamani , Standart G. L. 
Published: June 2004

AbstractConvenient expressions for calculating multicomponent gas phase mass transfer coefficients and transfer rates are obtained by use of an exact matrix method of solution to the Maxwell‐Stefan equations. The results are seen to be exact matrix analogues of classical binary relations and may also be applied as an approximation to describe liquid phase transport.
Evaluation of a rapid technique for measuring the diffusion coefficients of small molecules
Authors: Lemaguer Marc , Wolfe F. H. , Smyrl T. G. 
Published: June 2004

AbstractThe diffusion coefficients of sucrose, glycol, and glycine in water have been measured at 25.0°C by using the schlieren optical system of a preparative ultracentrifuge. The schlieren optical system was modified by the incorporation of a 35 mm single lens reflex camera. The values obtained were well within 2% of values found in existing literature and had an intrinsic precision of better than 2%.
A dual functional solid liquid separation process based on filtration and settling
Authors: Henry Joseph D. , Lui Alain P. , Kuo C. H. 
Published: June 2004

AbstractThe dual functional filter combines both the mechanisms of filtration and settling or decantation. The combined mechanisms of separation permit very high degrees of sludge dewatering; for example, slurries containing 0.2 wt. % gelatinous particles have been dewatered to produce a sludge of 35 wt. % particles. A mathematical model which includes both the effects of axial (vertical) variation of pressure driving force and cake compressibility effects is used in conjunction with experimental data to evaluate the dual functional filter performance.
Reaction of sulfur dioxide with limestone and the grain model
Authors: Hartman Miloslav , Coughlin Robert W. 
Published: June 2004

AbstractExperimental measurements of the reaction of sulfur dioxide and oxygen with limestones have demonstrated substantial influence of the geologic origin of the stone, its porosity and particle size, gaseous concentration of sulfur dioxide, and temperature on the course of reaction and the conversion (that is, the degree of utilization of the limestone content of the particles as a sorbent for sulfur dioxide). A mathematical model including intraparticle transport and chemical reaction within the particles (grain theory) has been developed to simulate this sulfur dioxide sorption reaction.
Application of h‐transformation for the solution of multicomponent adsorption in fixed bed
Authors: Tien Chi , Hsieh J. S. C. , Turian R. M. 
Published: June 2004

AbstractA procedure for the application of the so‐called h‐transformation in solving fixed‐bed multicomponent adsorption problems is developed. In order to apply this procedure, it is necessary to select an appropriate value for the transition‐motion factor ξ, and the criteria for making this selection are established in this work.
The static electrification of particles in gas‐solids pipe flow
Authors: Masuda Hiroaki , Komatsu Takahiro , Iinoya Koichi 
Published: June 2004

AbstractElectrostatic characteristics in gas‐solids flow in a metal pipe are studied both theoretically and experimentally with particular attention to the collision between particles and pipe wall. Effects of gas velocity and particle diameter on the electrification are also examined.
Catalyst aging in a process for liquefaction and hydrodesulfurization of coal
Authors: Stanulonis J. J. , Gates B. C. , Olson J. H. 
Published: June 2004

AbstractAged CoO/MoO3/SiO2/Al2O3 catalyst pellets, used in a pilot plant for the single‐stage liquefaction and hydrodesulfurization of coal, were analyzed with an electron microprobe and scanning electron microscope. The results demonstrate the occurrence of catalyst aging processes which could lead to bed plugging and pore mouth blocking.
Coal devolatilization and hydrogastification
Authors: Anthony Donald B. , Howard Jack B. 
Published: June 2004

AbstractThe fundamental understanding of coal and its behavior under gasification conditions is far from complete, but significant insights into the complex chemical and physical phenomena have been achieved. This review of available fundamental information focuses on thermal decomposition of coal in inert gas and in hydrogen, with emphasis on the effects on yield of products exerted by time, temperature, heating rate, pressure, hydrogen partial pressure, and particle size, and on the development of chemical and transport models of engineering importance.
Turbulent drag reduction in dilute fiber suspensions: Mechanistic considerations
Authors: Kale D. D. , Metzner A. B. 
Published: June 2004

AbstractBoth fibrous and polymeric additives, used alone or in combination, appear to affect primarily the fluid in the sublayer region adjacent to a solid surface, contrary to previous predictions. An analysis of fluid deformation modes shows tentatively why drag reduction levels become less sensitive to system scale when fibrous additives are employed, and why polymeric and fibrous additives may be more effective in combination than when either additive is used alone.
Global minimization of a cooled reactor by using a posynomial lower bounding function
Authors: Wilde Douglass J. 
Published: June 2004

AbstractThe cost of a reactor‐heater system with an auxiliary cooler can have at least two local minima and a local maximum, with respect to the design variables: temperature and extent of reaction. This cost can be bounded below by a unimodal function which, being a posynomial (a sum of power functions), can be minimized efficiently by geometric programming. Construction of this lower bounding function is not obvious, since the cost involves both a definite intergral and economies of scale.
Basic concepts of spray dryer design
Authors: Gauvin W. H. , Katta S. 
Published: June 2004

AbstractThe major parameters in the design of spray dryers are discussed. A Lagrangian approach, combining experimental data with theoretical concepts, is proposed to develop design methods. Vortex flow patterns, obtained experimentally in a laboratory size chamber, are correlated and presented.Based on this design methodology, computational methods are given to calculate droplet trajectories and hence to predict the optimum chamber dimensions and operating conditions for maximum thermal efficiency and/or minimum operating cost. Application of these basic principles is illustrated by the design of an industrial size, spray drying chamber for a specific feed solution and production rate.
An examination of the adaptive random search technique
Authors: Heuckroth M. W. , Gaddy J. L. , Gaines L. D. 
Published: June 2004

AbstractRandom search procedures have recently been successfully applied to the optimization of a variety of chemical engineering problems, including optimization of chemical processes by flow sheet simulation. These procedures represent the independent variables as random variables described by probability distributions. The adaptive random search procedure centers the distribution for each variable about the best search point found and examines this region for a better point. Thus, this technique has the ability of continuously moving the search region toward the optimum, which is particularly advantageous in following constraints.This study examines the efficiency of the adaptive random search technique as applied to six different problems, which have been previously solved by various other techniques.
Sorption of oxygen, nitrogen, carbon monoxide, methane, and binary mixtures of these gases in 5A molecular sieve
Authors: Ruthven Douglas M. 
Published: June 2004

AbstractEquilibrium data for the sorption of oxygen, nitrogen, carbon monoxide, and methane in 5A molecular sieve are analyzed in terms of a simple theoretical model isotherm. The model provides an excellent correlation of the single‐component isotherms over the entire concentration range, and it is shown that equilibrium data for sorption of binary mixtures of these gases are correctly predicted by the model using the parameters (Henry constants and molecular volumes) derived from analysis of the single‐component isotherms. The model predicts that mixtures of two sorbates with equal molecular volumes should show approximately ideal solution behavior in the adsorbed phase. The experimental data of Lederman for the sorption of nitrogen‐methane mixtures show the expected behavior over a wide range of pressures.