bluuebunny/crossref_metadata_2025_split huggingface dataset:
Elongational flow of polymer melts
Authors: Stevenson James F. 
Published: June 2004

AbstractElongational flow experiments with viscous polymeric material were conducted at a constant elongation rate on a modified tensile testing machine. Steady elongational and shear viscosity data and elongational stress growth data are presented for an isobutylene‐isoprene copolymer at 100°C. S‐shaped elongational stress growth curves are reported for cis‐1,4‐polyisoprene at 80°C.The stresses necessary to maintain a cylindrical specimen in steady elongational flow are indicated by a calculation which includes the effects of inertia, gravity, and interfacial tension.Interrelations among several elongational flow material functions are given for a constitutive equation based on the theory of linear viscoelasticity.
Ecological aspects of combustion devices (with reference to hydrocarbon flaring)
Authors: Swithenbank J. 
Published: June 2004

AbstractSome fundamental factors controlling the emission of pollutants by an industrial combustion system are illustrated by reference to gaseous hydrocarbon flare stack combustion. The formation of smoke (soot), radiation, and nitric oxide may be controlled by limiting of the premixed fuel air ratio to moderately rich mixtures. The factors which determine the design of a suitable Canada mixer are shown to be area ratio, density ratio, and pressure ratio. An important pollutant for large burners is the combustion roar. Fuel type and mixture ratio only affect the combustion noise output by about 5 db. The dominant factor in the generation of this noise is the burner turbulence, which can be controlled to reduce the combustion roar by up to 20 db.Burner cost considerations lead to the current use of simple flare tips; however, the eventual use of more technically sophisticated low pollution units is inevitable.
Nonisothermal laminar contracted flow
Authors: Christiansen E. B. , Kelsey S. J. 
Published: June 2004

AbstractTemperature and velocity profiles and pressure losses were computed for laminar, temperature‐dependent Newtonian flow from a stream tube through an abrupt contraction into and through the entrance region of a smaller coaxial tube, in which the fluid was cooled or heated at constant wall temperature. The equations of motion and energy, including axial diffusion and viscous dissipation, were solved numerically for diameter ratios of one and two, a practical temperature range, and NPe and NRe up to 100. Entrance temperatures and velocities are far from uniform, and pressure losses are greater than those computed using simplified equations and uniform entrance temperatures and velocities.
Asymptotic solutions of Hopf's equation for turbulent chemical reactions
Authors: Petty C. A. , Reed X. B. 
Published: June 2004

AbstractHopf's formalism is extended to chemically reactive turbulent systems, and weak mixing and convective mixing asymptotic forms are considered. The former recovers Corrsin's isotropic decay law for an isothermal first‐order, irreversible reaction; the latter extends Hopf's result to equipartition of mechano‐chemical energy.
Nucleation kinetics of the potassium sulfate‐water system
Authors: Randolph Alan D. , Cise Michael D. 
Published: June 2004

AbstractSecondary nucleation in the potassium sulfate‐water system occurs by micro‐attrition processes over the entire 1.3‐26 μ size range of this study. Experimental nucleation rates were correlated with power‐law kinetics expressions in terms of supersaturation, the fourth moment of the parent seed‐crystal distribution, and stirring rate. Such kinetics expressions are similar to those used to correlate MSMPR data; however, the secondary nucleation rates of this paper are two orders of magnitude greater than those reported in previous MSMPR studies of the same system. An upper bound on growth rate of these nuclei was calculated based on a population balance analysis; maximum growth rates of these nuclei was markedly size‐dependent in the 1.3‐26 micron size range of measurement, decreasing with decreasing size. The apparent descrepancy between these nucleation rates and MSMPR values can be explained by nuclei washout during the low growth rate period. Anomalous MSMPR kinetics (low or even negative supersaturation power‐law dependence) can be explained by this growth phenomenon.
A heuristic method for the inversion of certain Laplace transforms to produce initially valid approximations
Authors: Semerciyan Mikayel , Thodos George 
Published: June 2004

AbstractBased on a Lagrangian interpolation, a heuristic scheme is developed for the inversion of certain types of Laplace transforms and is applied to the solution of problems of interest to chemical engineers for which the exact solution is either very difficult or impossible to obtain. The solutions thus obtained are in good agreement with exact values, when available, for initial values of the transformed independent variable and may therefore be used as approximations. Three illustrative examples are presented.
Mass transfer to a rotating fluid: Part I. Transport from a stationary disk to a fluid in bödewadt flow
Authors: Smith Kenneth A. , Colton Clark K. 
Published: June 2004

AbstractSolutions are developed for mass transfer between a fluid undergoing solid body rotation and a coaxial disk which is located on a stationary infinite surface. The fluid mechanics corresponds to a laminar Bödewadt boundary layer. The overall mass transfer is dominated by the outer portion of the disk, a result of the high transfer rate associated with a leading edge. The concentration field near the axis of rotation extends to great axial distances as a long narrow plume. Approximate analytical solutions are given for each of these regions, and a numerical solution is provided for the entire concentration field.
Stability of rotational couette flow of polymer solutions
Authors: Sun Zu‐Shung , Denn Morton M. 
Published: June 2004

AbstractThe onset of secondary flow between rotating cylinders (Taylor vortices) was observed for a dilute polymer solution whose viscometric flow properties were characterized rheogoniometrically. The critical Taylor number (flow onset) was predicted accurately by linear stability theory with a stress constitutive equation describing viscometric behavior. The cell spacing differed significantly from that predicted by linear theory. A nonlinear analysis shows that Linear theory will predict the ultimate cell size only for an inelastic liquid. For an elastic liquid a larger wave number (closer spacing) is a lower energy configuration than the linear theory spacing. This is consistent with experiment.
Intermolecular repulsions and the equation of state for fluids
Authors: Carnahan Norman F. , Starling Kenneth E. 
Published: June 2004

AbstractThis investigation demonstrates the advantages of an improved expression for intermolecular repulsions in equations of state. A highly accurate equation of state for the rigid‐sphere fluid is used as the model of repulsion behavior in real fluids. A method for general usage of this new rigid‐sphere equation in real fluid models is presented via reformulation of van der Waal's equation using the accurate new rigid‐sphere equation to describe repulsion effects. To test this reformulation, properties of methane, ethane, propane, n‐butane, isobutane, hydrogen sulfide, nitrogen, ethylene, acetylene, methyl chloride, cyclohexane, pentane and octane have been calculated. The advantage of using the accurate rigid‐sphere equation was demonstrated by the general improvement in calculated properties relative to the original van der Waals and Redlich‐Kwong equations. Calculations of enthalpy departures for mixtures of nitrogen and methane, propane and methane, pentane and cyclohexane, and pentane and octane also indicated the desirability of using the accurate rigid‐sphere equation to describe repulsion effects in mixtures.
Hydrodynamic stability and natural convection in Ostwald‐de Waele and Ellis fluids: The development of a numerical solution
Authors: Ozoe Hiroyuki , Churchill Stuart W. 
Published: June 2004

AbstractAn algorithm was developed for the finite‐difference computation of hydrodynamic stability and natural convection in non‐Newtonian fluids heated from below. Test calculations were carried out for fluids whose viscosity characteristics are described by the Ostwald‐de Waele (power‐law) and Ellis models and for roll‐cells with both rigid and dragless vertical boundaries. The effects of time‐step and grid‐size were tested thoroughly. The results were found to be independent of the assumed initial state. The computed values of the Nusselt number and the critical Rayleigh number for Newtonian fluids agree well with prior experimental results. The computations for the Ostwald‐de Waele model indicate that the approximate solution of Tien, Tsuei, and Sun may underestimate the critical Rayleigh Number.
Synthesis in the design of chemical processes
Authors: Hendry J. E. , Rudd D. F. , Seader J. D. 
Published: June 2004

AbstractUntil recently, the subject of chemical process synthesis was largely ignored in the chemical engineering literature despite its importance in chemical engineering practice. However since 1968, attention to the subject has greatly increased and important progress has been made. This review article critically surveys the readily accessible literature in chemical process synthesis from two points of view: theory and applications. It is concluded that a number of effective synthesis tools are now available for application in industrial chemical process design. However, much more remains to be done, particularly with regard to the development of synthesis procedures which can lead to novel processing system structures.
Prediction of transport processes within porous media: Diffusive flow processes within an homogeneous swarm of spherical particles
Authors: Neale Graham H. , Nader Walter K. 
Published: June 2004

AbstractA geometric model for an homogeneous and isotropic porous medium composed of spherical particles is proposed. This model requires a minimum of geometric simplifications and lends itself to the study of hydrodynamic as well as diffusive flow processes, permitting in each application a mathematically rigorous and fully predictive analysis leading to mathematical representations of the respective flow parameters.This particular investigation seeks to evaluate, and to provide physical insight into, diffusive flow processes occurring within an homogeneous swarm of spherical particles.
Dropwise and filmwise condensation of water vapor on gold
Authors: Wilkins David G. , Bromley Leroy A. , Read Stanley M. 
Published: June 2004

AbstractA pure gold tube was found to give filmwise condensation in the absense of organic contamination in a flow sitution simulating that found in seawater conversion plants. A sensitive test for the presence of organic contamination has been developed. The gold tube, promoted by paraffinic thio‐silane or mercaptan, gave 100% excellent dropwise condensation. Overall heat transfer coefficients are reported for filmwise and dropwise condensation. The steamside heat transfer coefficient with dropwise condensation was estimated to be over 0.2 MW/m2‐°C (35,000 B.t.u./hr‐ft2‐°F) at the 95% confidence level.Gold plated tubesSupplied by P. Tomalin and S. Mulford of the Office of Saline Water, USDI.
gave 95% filmwise condensation after one week of operation in a clean, once‐through system.
Suboptimal feedback control of distributed systems: Part II. Discussion of test systems and numerical results
Authors: Vermeychuk J. Gregory , Lapidus Leon 
Published: June 2004

AbstractThe suboptimal control algorithms developed in Part I are tested on four example problems to obtain some indication of their performance. Results are presented and compared with results obtained from the application of classical open‐loop optimal control synthesis algorithms to the same test problems.The suboptimal feedback control algorithms are found to give acceptable performance on both linear and nonlinear systems at the expense of very little computational effort.
Vapor‐Liquid equilibrium: Part I. An appraisal of data reduction methods
Authors: Van Ness Hendrick C. , Byer Stanley M. , Gibbs Richard E. 
Published: June 2004

AbstractCorrelations of the excess Gibbs function and the activity coefficients of a binary, liquid‐phase system at constant temperature depend on reduction of P‐x‐y data taken for the system in vapor‐liquid equilibrium. It is shown that use of a full P‐x‐y data set is for all practical purposes based on just the P‐y values. Alternative procedures require only P‐x or P‐y data. In any case, effective use of a full P‐x‐y data set can be made only if redundent experimental values of Px,y or P are compared for consistency with calculated values. This cannot be accomplished by means of the popular area test for thermodynamic consistency.
Gasification: Part II. Extension to diffusion control
Authors: Hashimoto Kenji , Silveston P. L. 
Published: June 2004

AbstractGasification model developed in Part I is extended to allow for mass transfer of oxidant to the particle and for intraparticle diffusion. For this extension, a moving boundary problem results which is solved numerically in conjunction with a two‐point boundary value problem for the oxidant concentration profile in the particle. The extended model predicts, as expected, that mass transfer stifles gasification and intraparticle diffusion shifts gasification to the outer surface of the particle. For the conditions and parameters used in Part I, particle Thiele moduli above 10 result in particle shrinkage with negligible change in the solid properties, whereas if this modulus is less than 0.1, gasification is kinetically controlled.
Infinite dilution diffusion coefficients in liquids
Authors: Vadovic C. J. , Colver C. P. 
Published: June 2004

AbstractThe extension of the Enskog theory by Tham and Gubbins for the calculation of diffusivities is applied to the prediction of infinite dilution diffusion coefficients in binary organic systems. The resulting expression is a function only of the size and mass of the diffusing species. Excellent agreement is obtained for nonassociating n‐alkane mixtures as well as for associated systems. Extension of the expression to alcohol and aqueous systems is shown to require Only an empirical correction factor. It is also shown that the quantity Dij∞ ηj Mj/ρjT is independent of temperature for all systems.
Convergence properties of systems of algebraic equations—explicit loops
Authors: Friedman Francois , Ramirez W. Fred 
Published: June 2004

AbstractTechniques are developed for using the structural information contained in algebraic equation sets to aid in the study of convergence properties of iterative equation loops.The concept of inverse mapping is applied directly in order to study convergence properties of sequences. For problems in which there exist both a direct and inverse path for the computation of iterative loops, direct substitution techniques will converge via one path and diverge via the other path. When an inverse path existed, the direct substitution method was superior to simultaneous solution techniques for the problems studied. Not all iterative loops have an inverse path. For problems in which inverse paths do not originally exist, rearrangement of the equations of an iterative loop can result in a modified loop for which an inverse path does exist. The digraph representation of an iterative loop aids in deciding whether rearrangements are feasible for a particular problem. When inverse paths cannot conveniently be obtained, direct substitution cannot be successfully used and simultaneous solution techniques such as quasi‐linearization are recommended.
Real‐time control of air pollution
Authors: Kyan Chwan P. , Seinfeld John H. 
Published: June 2004

AbstractThe problem of determining real‐time (episode) air pollution control strategies for an urban airshed is posed as selecting those control measures from among all possible such that air quality is maintained at a certain level over a given time period and the total control imposed is minimum. The real‐time control is based on meteorological predictions made over a several‐hour to several‐day period. A computational algorithm is developed for solving the class of control problems that result. The theory is applied to a hypothetical study of the effect of implementation of the optimal control on September 29, 1969, in the Los Angeles basin.
Gas‐solid fluidized systems: Average mass transfer potentials of shallow beds
Authors: Yoon Poong , Thodos George 
Published: June 2004

AbstractAn experimental investigation has been conducted on the direct establishment of mass transfer driving forces for the vaporization of n‐decane from Celite particles fluidized by air. Ranges of particle sizes and reactor diameters were employed.Concentration profiles of n‐decane were determined and were integrated to obtain the actual average concentration difference for the entire bed. The ratio of the actual driving force to the corresponding log‐mean value has been correlated with the average particle size, the fluidized bed height, and the modified Reynolds number to produce two relationships capable of predicting these ratios to within 2.5% (83 runs). The results for these mass transfer studies should also be applicable to comparable studies on heat transfer in fluidized beds.
Thermodynamics of concentrated polymer solutions containing polyethylene, polyisobutylene, and copolymers of ethylene with vinyl acetate and propylene
Authors: Newman R. D. , Prausnitz J. M. 
Published: June 2004

AbstractGas‐liquid chromatography is used to measure polymer‐solvent interactions in polymer solutions where the solvent is at infinite dilution. Experimental data are presented for 24 binary polymer‐solvent systems in the temperature range 50° to 150°C. A simple relation exists between the experimental retention volume data and the infinite dilution volatility; this volatility can be used to calculate the solvent vapor pressure over the polymer solution up to about 0.1 weight fraction solvent. Using concepts from the Prigogine‐Flory theory of polymer solutions, Flory‐HugginsXparameters for some polymer‐hydrocarbon systems were correlated with the hydrocarbon's normal boiling temperature.
Experimental liquid mixture densities for testing and improving correlations for liquefied natural gas
Authors: Rodosevich James B. , Miller Reid C. 
Published: June 2004

AbstractLiquid molar volumes and excess volumes have been experimentally determined for some methane‐rich binary and ternary mixtures containing ethane, propane, isobutane, and nitrogen between 91 and 115 K. A gas expansion type system calibrated against pure methane densities was used to make the necessary pure fluid and mixture measurements.The best of the available density correlations predicts the experimental methane‐ethane molar volumes within ±0.2%, while larger systematic deviations are found for the methane‐propane and methane‐isobutane systems. Molar volumes for methane‐nitrogen and ternary mixtures containing nitrogen diverge strongly from the correlation predictions at 108 K and higher temperatures. An empirical scheme is proposed for predicting molar volumes of methane‐rich liquefied natural gases using reported methane‐ethane and methane‐nitrogen excess volumes. This method predicts all binary and ternary molar volumes from this investigation within ±0.1%.
Membrane ultrafiltration of a nonionic surfactant
Authors: Grieves R. B. , Bhattacharyya D. , Schomp W. G. , Bewley J. L. 
Published: June 2004

AbstractAqueous solutions 1.65 × 10−4 to 1.10 × 10−2 molar in the nonionic surfactant Triton X‐100 are subjected to membrane ultrafiltration over the temperature range of 22 to 50°C in a continuous flow, thin channel cell, with channel Reynolds numbers from 50 to 1175. Data for the ultrafiltrate flux through the optimum polyelectrolyte complex membrane (of the three tested) are correlated by an equation involving the in‐series resistances of the membrane and of the polarized boundary layer of the sufactant rejected by the membrane, with the latter resistance varied over a wide range. The correlations are used to estimate the required membrane area and resultant ultrafiltrate concentration of surfactant to achieve any specified water recovery using cells‐in‐series and cells‐in‐parallel operation. The gelation concentration and surfactant mass transfer coefficient are used to estimate water flux in the gel‐polarization region.
Stability of moving surfaces in fluid systems with heat and mass transport II. Combined effects of transport and density difference between Phases
Authors: Miller Clarence A. 
Published: June 2004

AbstractStability of interfaces moving as a result of phase transformation or mass transfer is considered. Effects of transport and of the density difference between phases known to significantly influence stability during solidification and combustion respectively are here studied theoretically in fluid systems. The analysis indicates that instability is possible during vaporization of liquids under vacuum and perhaps during growth of cavitation bubbles. But except when interfacial tension is very low, instability is unlikely during mass transfer in liquid‐liquid systems because the density difference between phases is small. A density difference can also produce cellular convection at an unstable interface during solidification.
A stochastic analysis of a nonisothermal packed bed reactor
Authors: Kado T. , Himmelblau D. M. 
Published: June 2004

AbstractMonte Carlo techniques have been used to simulate the stochastic responses of the nonisothermal packed bed reactor. Random variables with specified ensemble means, ensemble standard deviations, and probability distributions (normal, uniform, or autocorrelated) were introduced as inputs and parameters into the model equations, and the equations were solved repeatedly to provide a sample of the outputs. Sample means and sample standard deviations both in the steady and unsteady state were evaluated and the probability distributions of the output temperature and concentration characterized. Confidence limits for a specified confidence coefficient have been determined from which overdesign factors could be computed.
Removal of liquid from a packed column of spherical beads under centrifugal force
Authors: Fricke Gordon H. , Rosenthal Donald , Welford George A. 
Published: June 2004

AbstractSurface sulfonated copolymer beads and glass beads of various size distributions were used to study the removal of liquid from a packed column of spherical beads under centrifugal force. At low forces, from 1 G to approximately 20 G, the volume of liquid retained corresponds to the free volume between the packed beads. The liquid level varies with force from about 20 to 400 G. It is shown that the liquid level is a function of the force applied and the size distribution of the beads in the column. At forces from approximately 400 to 1200 G the weight of the liquid on the sample remains constant.
Chemical kinetics at a critical point
Authors: Snyder R. B. , Eckert C. A. 
Published: June 2004

AbstractThe rate of the Diels‐Alder reaction of isoprene with maleic anhydride has been measured in the vicinity of the upper critical solution points of two liquid‐liquid mixtures, and the rate of the Menschutkin reaction of ethyl iodide and triethylamine has been investigated near a lower critical solution point. Anomalous behavior has been observed, with the former reaction rate augmented by up to 40% and the latter apparently running 25–30% too slow. A possible explanation for these results is presented in terms of transition state theory and the abrupt behavior of the solution activities of dilute solutes near a critical point.