bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dialysis study of diffusion in a flowing suspension
Authors: Hsu George C. , Lindgren Robert G. , Chung Ying‐Chee , Corcoran William H. 
Published: June 2004

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

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

AbstractA liquid flowing over a nonwettable surface can form rivulets of various types. The regime of rectilinear rivulet flow plays a key role in that it provides the basis for the study of the other regimes.An analytical solution for the velocity distribution of rectilinear rivulet flow down a vertical plate is derived. A generalized Ritz‐Galerkin method is used to obtain a polynomial solution for the case of an inclined plate.These results, unlike those of previous authors, enable one to calculate all the rectilinear flow properties of rivulets over the complete range of practical interest.
Shear viscosity of native and enzyme hydrolyzed amioca starch pastes
Authors: Cruz Angel , Russel William B. , Ollis David F. 
Published: June 2004

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

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

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

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

AbstractTwo kinetic models of hydrocarbon hydrogenolysis over monometallic surfaces, based respectively on catalytically uniform or nonuniform surfaces, are applied to ethane and n‐pentane hydrogenolysis results over copper‐nickel alloy catalysts as well as the monometallic catalysts platinum and nickel. If no direct hydrogen desorption appears in any postulated irreversible step, both models predict the same composition for the important surface intermediates CnHx (n = 1, s), where x depends upon the catalyst.This analysis predicts that for essentially all alloy catalysts to which the postulated sequences may apply, the hydrogenolytic surface intermediate CnXx contains one more hydrogen atom than that calculated for a nickel catalyst: specifically, C2H3 (alloy) vs. C2H2 (nickel) for ethane and C5H6 (alloy) vs. C5H7 (nickel) for n‐pentane.
Exothermic gas absorption with chemical reaction
Authors: Mann Reginald , Moyes Hilary 
Published: June 2004

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

AbstractNew measurements are presented on the influence of Schmidt number on the rate of mass transfer between a turbulent fluid and a pipe wall. It is found that for large Schmidt numbers the fully developed mass transfer coefficient is related to the friction velocity and the Schmidt number by the equation
equation image
The experiments are accurate enough to rule out the Sc−2/3 or the Sc−2/3 relations commonly used, deduced from plausible limiting expressions for the eddy diffusivity close to a wall. It is argued that these expressions arevalid only over a vanishingly small portion of the concentration field as Sc → ∞.
Thermal cracking of light hydrocarbons and their mixtures
Authors: Froment Gilbert F. , Van De Steene Boudewijn O. , Vanden Berghe Philip J. , Goossens A. G. 
Published: June 2004

AbstractThe kinetics and product distributions of the thermal cracking of binary and ternary mixtures of ethane, propane, n‐ and i‐butane were determined in a pilot plant under conditions of residence time, temperature, total pressure, and dilution as close as possible to those prevailing in industrial operation. The kinetics and yields observed with ternary mixtures were compared with those obtained with binary mixtures and with pure components. The experimental selectivities were compared with those which would be obtained from separate cracking and subsequent addition of the product streams. The deviations between the two can be predicted by means of the so‐called global kinetics selectivities, which are based upon the selectivities obtained from the pure components cracking and upon the global rates of cracking of the feed components in the mixture.
A rigorous method for predicting the critical properties of multicomponent systems from an equation of state
Authors: Peng Ding‐yu , Robinson Donald B. 
Published: June 2004

AbstractThis paper shows how the rigorous critical state criterion enunciated by Willard Gibbs can be used with a recently formulated two‐parameter equation of state to obtain an analytical solution to the problem of predicting the critical properties of defined multicomponent mixtures. Comparisons are made between predicted and experimental values for several systems containing paraffin hydrocarbons and related materials.
Formation of an air‐water two‐phase flow
Authors: Adler Pierre M. 
Published: June 2004

AbstractThe geometrical parameters of injection devices are shown to have almost no effect on the resulting two‐phase flow, while they influence the pressure drop owing to its formation. The predominant hydrodynamic parameter is the ratio of the mean superficial velocities. A simplified analysis leads to good agreement with experimental results. The different causes of pressure drops are quantified.
Flow of slurries in pipelines
Authors: Turian Raffi M. , Yuan Tran‐Fu 
Published: June 2004

AbstractPressure drop correlations for flow of slurries in pipelines were developed for each of the following four flow regimes: flow with a stationary bed, saltation flow, heterogeneous flow, and homogeneous flow. A total number of 2 848 data points, comprised of 1 912 collected from the published literature together with 936 taken using our own test pipelines and relating to ranges of the pertinent variables extensive enough to span all four flow regimes were used as the basis of these correlations. Also, these data were used in developing an associated quantitative regime delineation scheme. The correlations provide an improved predictive capability over previously available procedures and are also broader in scope. The delineation procedure developed here permits straightforward classification of the data according to the flow regime prevailing, and it is moreover inclusive of all the data and is self‐consistent.
Transport of nitrate ion in unsteady, unsaturated flow in porous media
Authors: Hildebrand Margaret A. , Himmelblau David M. 
Published: June 2004

AbstractA simplified model of nitrate ion transport (and other nonadsorbing solutes) in unsteady, unsaturated flow in porous media has been developed. The model represents nitrate flow in infiltration and drainage in sand quite well and can be applied to unsaturated flow in other homogeneous media with only minimum extra experimental data needed to describe the medium.
Vacuum stripping of refrigerants in water sprays
Authors: Lin Wen‐Cheng , Rice Philip A. , Cheng Yung‐Sung , Barduhn Allen J. 
Published: June 2004

AbstractThe number of overall liquid transfer units as a function of the total pressure, flow rate, and nozzle height has been measured for the removal of butane and F‐22 refrigerants from water for a flat spray nozzle in a vacuum spray chamber. The number of transfer units increases with the flow rate and with the total pressure with the increase proportional to 0.2 power of the Weber number in which the gas density is used. NOL also increases linearly with length, but more than two‐thirds of the mass transfer always takes place in liquid sheet attached to the nozzle. Because the rate of mass transfer in a spray chamber is much greater than in a packed column, vacuum spray stripping is recommended for the removal of refrigerants from water and brine in the freezing and hydrate processes for desalination and other slightly soluble gases from aqueous solution in other processes.
Absolute evaporation rates for some polar and nonpolar liquids
Authors: Lednovich Sandra L. , Fenn John B. 
Published: June 2004

AbstractA method was developed for providing continuously wiped and, therefore, clean liquid surfaces in vacuo. By means of a mass spectrometer detector, the absolute evaporation flux from such clean surfaces was measured for diethylene glycol, glycerine, dibutyl phthalate, and oleic acid. The molecular flux from equilibrium vapor was also measured by the same detector. The ratio of the former to the latter, the evaporation coefficient, was found in each case to be close to unity and independent of the temperature.
Vapor‐liquid equilibrium of hydrogen/tetralin system at elevated temperatures and pressures
Authors: Simnick J. J. , Lawson C. C. , Lin H. M. , Chao K. C. 
Published: June 2004

AbstractA flow type of apparatus is built to give equilibrium gas and liquid samples at elevated pressures and temperatures while minimizing thermal decomposition. Saturated vapor and liquid compositions and K values are determined with this apparatus for the binary system hydrogen/tetralin (1,2,3,4‐tetrahydronaphthalene) at four temperatures from 189.6° to 389.1°C, and seven pressures from 20 to 250 atm. Vapor pressures of tetralin are determined with the same apparatus, and values are reported at the four temperatures of this work.
Vacuum‐spray stripping of sparingly soluble gases from aqueous solutions: Part I. Mass transfer from streams issuing from hydraulic nozzles
Authors: Simpson Stuart G. , Lynn Scott 
Published: June 2004

AbstractCarbon dioxide, oxygen, Freon 114, and butane were stripped from deionized water, sodium chloride solutions, and freshly acidified seawater in a vacuum‐spray chamber using three types of hydraulic nozzle. Purely physical desorption was found for each gas/liquid system.For both conical‐spray and fan‐jet nozzles, the bulk of the gas was shown to desorb from the thin liquid sheet issuing from the nozzle, that is, before droplet formation occurs. Behavior was explained semiquantitatively by a mathematical model of the diffusion in the sheet. This model was also shown to predict well the desorption from the laminar liquid sheets formed by jet impingement nozzles. For turbulent flow in jet impingement nozzles, the fit of the model was again semiquantitative.
Separation of proteins via semicontinuous pH parametric pumping
Authors: Chen H. T. , Hsieh T. K. , Lee H. C. , Hill F. B. 
Published: June 2004

AbstractA semicontinuous pH parametric pump for separating proteins was experimentally investigated using the model system haemoglobin and albumin on a Sephadex ion exchanger. The pump considered had a center feed between an enriching column and a stripping column and was operated batchwise during upflow and continuously during downflow. Various factors affecting separations were examined. It was shown that parametric pumping is capable of separating proteins with high separation factors.
Multivariable computer control of a butane hydrogenolysis reactor: Part I. State space reactor modeling
Authors: Jutan Arthur , Tremblay J. P. , MacGregor J. F. , Wright J. D. 
Published: June 2004

AbstractA state space model is developed for an existing nonadiabatic packed‐bed reactor which experiences axial and radial concentration and temperature gradients resulting from highly exothermic reactions involving several chemical species. The set of partial differential equations is reduced from three to two dimensions using orthogonal collocation. Further use of orthogonal collocation on the quasi steady state version of the differential equations results in a set of coupled algebraic and differential equations from which a linearized low‐order state space model is obtained. The model parameters are estimated from reactor data, and the fitted model is used for design and implementation of a multivariable stochastic control schemes on the reactor. These applications are described in parts II and III of this paper.
Effect of dimethyl sulfoxide on drug permeation through human skin
Authors: Chandrasekaran S. K. , Campbell P. S. , Michaels A. S. 
Published: June 2004

AbstractThe effect of the presence of dimethyl sulfoxide (in admixture with water) on the sorption and permeation rate of scopolamine base in human skin in vitro has been measured as a function of drug concentration in aqueous solution. The equilibrium sorption of scopolamine by skin from solution appears to be unaffected by the presence of even high concentrations of dimethyl sulfoxide in the solution phase. In the absence of a transdermal gradient of DMSO (or water), the permeability of skin to scopolamine in the presence of DMSO is about twofold higher than in its absence, suggesting that the diffusivity of scopolamine in the stratum corneum is somewhat elevated by the solvating action of DMSO.When, however, a gradient of DMSO concentration is impressed across the skin (irrespective of whether that gradient is of the same or opposite sign to that of the drug), the permeability of the skin to scopolamine is increased by one to two orders of magnitude. Microscopic examination of the skin subjected to such treatment reveals marked swelling, distortion, and intercellular delamination of the stratum corneum, which is only partially reversible following complete extraction with water. These effects are believed due to development of very high osmotic stresses produced within the stratum corneum, as both water and DMSO are transported into the tissue.
Deposition of solid particles on a collector: Formulation of a new theory
Authors: Wang Chiu‐Sen , Beizaie Masoud , Tien Chi 
Published: June 2004

AbstractTwo concepts concerning the deposition of particles from suspension onto a collector, the shadow effect due to deposited particles and the singular and random behavior of approaching particles, are presented and discussed. Based on these concepts, a new theory of particle deposition is proposed and procedures for the simulation of deposition process outlined. The simulation results give the rate of deposition and the deposit morphology. Potential applications of this model to a number of technical problems are outlined.
Simulation of particulate systems using the concept of the interval of quiescence
Authors: Shah B. H. , Ramkrishna Doraiswami , Borwanker J. D. 
Published: June 2004

AbstractA simulation procedure is presented in this work which can analyze the behavior of any dispersed phase system consisting of particles whose random behavior is specified in terms of probability functions. The procedure distinguishes itself from its predecessors in being free from arbitrary discretization of time or any other parameter along which the system evolves, and its ability to predict the behavior of randomly behaving small populations. Where population balance equations, which describe the behavior of particulate systems, cannot be readily solved, the simulation technique presented herein represents an efficient alternative to the modeling of such systems. Tables and a flow chart are given which would enable the use of the method for any system with specified particle behavior.
Properties and structure of polymeric alloys
Authors: Shen Mitchel , Kawai Hiromichi 
Published: June 2004

AbstractBecause of the generally immiscible nature of polymers, multicomponent polymers or polymeric alloys often exhibit microphase separation. The morphologies of these heterogeneous materials are determined not only by the composition of the system, but also by the processing conditions. The resulting microstructures exert a profound influence on the properties of the polymeric alloys. The purpose of this review is to discuss the more recent advances in the investigation of the relation between the structure of the polymeric alloys and their properties. An understanding of this relationship would be important in being able to tailor make better materials and exploit the unique properties of these materials for engineering applications.
Pore diffusion in packed‐bed reactors containing immobilized glucoamylase
Authors: Swanson Steven J. , Emery Alden , Lim Henry C. 
Published: June 2004

AbstractConversion was measured in small packed‐bed reactors containing immobilized glucoamylase in a range of variables in which diffusion was an important limitation. Three sets of data involving two carriers and two temperatures agreed satisfactorily with the theory of simultaneous reaction and diffusion.Several reactors were designed for 99% conversion, and the results show that diffusion is a small problem when feed concentration is high but a serious problem at low concentration, requiring careful design of the catalyst. The particle size needed to eliminate the effect of diffusion is shown as a function of length.
Collocation solution of creeping newtonian flow through periodically constricted tubes with piecewise continuous wall profile
Authors: Neira Mariano A. , Payatakes A. C. 
Published: June 2004

AbstractA collocation solution of creeping Newtonian flow through periodically constricted tubes is obtained. The profile of the wall of the type of tube considered is piecewise continuous, composed of symmetric parabolic segments. A transformation of the domain of interest into a rectangular one is obtained, which allows satisfaction of all boundary conditions. The collocation solution gives the stream function in terms of the new independent variables and can easily be converted to the original cylindrical coordinates. Axial and radial velocity components are obtained in analytical form, and the pressure drop is calculated from a volume integration of the viscous dissipation function as well as from line integration of the Navier‐Stokes equation. The results are compared with the finite‐difference solution by Payatakes et al. (1973b) and are found in good agreement. Differences between the two solutions are attributed mainly to discretization error in the finite‐difference solution. The analytical expressions obtained from the collocation solution can be used together with porous media models of the constricted unit cell type for the modeling of processes taking place in granular porous media.
Droplet size spectra generated in turbulent pipe flow of dilute liquid/liquid dispersions
Authors: Karabelas A. J. 
Published: June 2004

AbstractExperiments were carried out with water dispersed in hydrocarbons at various flow rates. The measured size spectra can be well represented by either an upper limit log‐probability function or a Rosin‐Rammler type of equation with constant parameters and only one variable, the maximum drop diameter dmax or d95. The latter can be predicted satisfactorily by a correlation based on the Hinze/Kolmogorov model of droplet breakup.