bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spatial formulation of the Orr‐Sommerfeld equation for thin liquid films flowing down a plane
Authors: Krantz William B. , Owens W. Brechner 
Published: June 2004

AbstractThe linear stability problem for thin liquid films flowing down a plane is formulated in terms of disturbance which are harmonic in space and time and grow or decay spatially. A closed‐form analytical solution to the resulting spatial formulation of the Orr‐Sommerfeld equation is shown to compare more favorable with wave property data than do solutions to the classical temporal formulation of this stability problem. The predictions of Gaster that the spatial and temporal formulations will be equivalent only for weakly amplified nondispersive disturbances are confirmed for falling film flow.
Dissolution of a homogeneous porous medium by surface reaction
Authors: Glover Martin C. , Guin James A. 
Published: June 2004

AbstractIn this paper a mathematical model is used to predict the time behavior of porosity and permeability of a porous medium being dissolved by acid. Experimentally determined reaction kinetics and pore size distribution are used in the model. The acidizing process studied here is of importance in the stimulation of oil well reservoirs. A polynomial expansion method is used to obtain an approximate solution to an infinite hierarchy of moment equations resulting from application of the capillary model. Experimental porosity and permeability measurements using a sintered glass disk dissolved by hydrofluoric acid are in good agreement with predictions from the model.
Reaction path synthesis strategies
Authors: Powers Gary J. , Jones Russell L. 
Published: June 2004

AbstractA system is offered for the mathematical representation of the functional and structural features of organic molecules and their reactions. Two basic synthesis strategies, an antithetic method anda synthetic method, are defined and compared. The use of heuristic information in guiding synthesis is evaluated. A synthetic method which uses dynamic programming is presented and applied to the synthesis of bihelical DNA. Possible extensions to other classes of compounds are presented.
Molecular thermodynamics for chemical reaction design
Authors: Eckert C. A. , Hsieh C. K. , McCabe J. R. 
Published: June 2004

AbstractVarious techniques of molecular thermodynamics and solution theory have been applied, through the transition state theory, to problems in chemical kinetics. These include experimental techniques for ascertaining the structure and properties of the transition states for various classes of reactions, plus analytical methods for using this information to predict the effect of solvents or reactant structure on chemical reaction rates. Such methods provide the chemical engineer with an additional parameter to use in the optimal design of reaction systems–that is, the chemistry of the reaction itself.
Oscillating behavior on distillation trays
Authors: Biddulph Michael W. , Stephens David J. 
Published: June 2004

AbstractThe objective of this work was to study the undesirable oscillating behavior which can develop on distillation trays. This takes the form of violent lateral movements of the gas/liquid mixture, causing premature flooding and reduced efficiency. It has been demonstrated that entrainment is significantly increased by the presence of oscillations. A simple predictive method by which a designer may evaluate the likelihood of oscillations occurring is proposed. It is concluded that columns of greater than about 1.0 m diam. operating at atmospheric pressure or above are unlikely to oscillate. However, reduced pressure columns of greater diameter may oscillate. A very simple mesh baffle system which completely prevents oscillations developing is described.
Analysis of the normal stress extruder
Authors: Good Paul A. , Schwartz Arthur J. , Macosko Christopher W. 
Published: June 2004

AbstractA theoretical and experimental investigation of the pumping characteristics of the normal stress extruder was made. The theoretical model requires only material property data and extruder dimensions and rotation speed to evaluate the main velocity field, flow rate, and pressure. The flow from the extruder was measured for two viscoelastic polymer solutions and a polymer melt as a function of gap setting and angular velocity. These measurements were in reasonable agreement with the proposed model.
Chlorination of sulfur dioxide in a plasma arc photochemical reactor: Part I. Reactor performance
Authors: Quarderer George J. , Kadlec Robert H. 
Published: June 2004

AbstractThis is a study of a photochemical reactor consisting of a vortex‐stabilized arc and an annular, triple‐walled, fused silica reaction chamber. An argon arc plasma provides the light. For power inputs of 3‐12 kw, the spectral output of the light source was characterized as a function of wavelength, arc‐gas flow rate, power input to the arc, and position along the arc. For power inputs of 3.84 and 8.45 kw, there were, respectively, 0.314 and 0.862 einsteins emitted per hour in the 2500 to 5000Å wavelength region. Selective filter solutions of 1.5N KNO3 and 0.05N KI were investigated. A reactor analysis is presented, based on mass and energy balances, and the geometrical properties of the system.
Chlorination of sulfur dioxide in a plasma arc photochemical reactor: Part II. Chlorination of sulfur dioxide
Authors: Quarderer George J. , Kadlec Robert H. 
Published: June 2004

AbstractThe photochemical chlorination of sulfur dioxide was investigated experimentally. The photochemical reactor was the vortex‐stabilized arc radiation source described in Part I. Aqueous inorganic solutions, providing selective wavelength filtration, were circulated through the inner annular region. The outer annulus served as the reaction volume. The dependence of the reaction on wavelength, reaction gas inlet temperature, pressure, and reactant flow rate was investigated. The amount of sulfur dioxide in the mixture was varied from 1/6 to 2/3 atmosphere. The photochemical rate of formation of sulfuryl chloride is best described by the rate expression:

where J is the volumetric rate of light absorption and where k0 and E have values of 0.0542 s1/2 and −2.6 kcal/gmol, respectively.
Developing pressure profiles for non‐Newtonian flow in an annular duct
Authors: Bhattacharyya Satinath , Tiu Carlos 
Published: June 2004

AbstractA steady, laminar, isothermal flow of non‐Newtonian fluids in the entrance region of an annulus has been studied experimentally. The axial pressure distributions, as well as the excess pressure energy, in the developing flow region are presented. The loss coefficients are found to increase with increasing flow behavior index for inelastic power law fluids. The experimental values of the loss coefficients are about 20% lower than those predicted from the boundary‐layer approximation method presented earlier. A preliminary result indicates that the entrance loss for a viscoelastic fluid is much smaller than that for the inelastic fluid of the same flow behavior index.
Theoretical development and experimental verification of a novel, well‐mixed vessel
Authors: Landau Julian I. , Petersen Eugene E. 
Published: June 2004

AbstractThe mixing characteristics of a vessel containing no moving parts have been studied theroretically and experimentally. The vessel consists of two chambers separated by a porous barrier. Mixing results because elements of fluid permeating the barrier at various distances from the inlet reside for different periods of time within the vessel and combine with other elements having entered earlier and later. An apparatus was designed a priori and experimentally verfied to give a residence‐time distribution function the same as a completely mixed vessel. The method was extended to show that in principle a vessel exhibiting any residence‐time distribution function can be designed by modifying the geometries of the chambers and the porous barrier.
Determination of slip ratios in air‐water two‐phase critical flow at high quality levels utilizing holographic techniques
Authors: Lee Young J. , Fourney Michael E. , Moulton Ralph W. 
Published: June 2004

AbstractHolographic techniques employing a pulse ruby laser were used to measure the size and velocity of drops for air‐water two‐phase critical flow at quality levels above 0.95. The use of a large numerical aperture in the holographic recording system permitted diffraction limited resolution of the droplets. The measured slip ratio a long withthe observation that a very significant portion of the liquid phase was concentrated near the boundary layer at the exit plane indicates that a separated flow model describing two‐phase critical flow would represent the actual conditions to a better degree than the other models.
A calculational procedure for design problems in multicomponent distillation
Authors: Ricker Neil L. , Grens Edward A. 
Published: June 2004

AbstractA calculation procedure for multicomponent distillation has been developed that is directly applicable to design problems. It is based on successive approximation methods with adjustment of the number of equilibrium stages in each column section between iterations to meet given reflux flow and feed stage composition conditions while maintaining specified key component recoveries. This procedure has been applied to a number of representative distillation design problems. It converges readily to proper column designs from initial estimates based on a noniterative stage‐to‐stage calculation. Moreover, the procedure is markedly superior in computational efficiency to solution of design problems by repeated application of operating calculations to assumed column configurations.
A new method for the estimation of parameters in differential equations
Authors: Bosch Bruno Van Den , Hellinckx Leon 
Published: June 2004

AbstractA new objective function for estimating parameters in differential equations, based upon a weighted least squares criterion for the residuals of these equations, is presented. The use of Lobatto quadrature in combination with the collocation technique reduces the original problem to one of minimizing a simple algebraic expression with respect to a series of unknowns. The method can be applied to different types of differential equations as shwon by a series of examples and leads to very good estimates. It becomes particularly useful for systems which are linear in the parameters and for which all states are observable since in this case the usual convergence problem is avoided. The gain in computation time when compared with classical methods is significant.
Simultaneous measurement of interfacial area and mass transfer coefficients for a well—mixed gas dispersion in aqueous electrolyte solutions
Authors: Robinson Campbell W. , Wilke Charles R. 
Published: June 2004

AbstractA new measuring technique involving concurrent chemical absorption of carbon dioxide and desorption of oxygen is developed for simultaneously evaluating the liquid‐phase mass transfer coefficient kL and the specific area a of sparingly‐soluble gas dispersions in stirred tanks containing an aqueous solution of inorganic electrolytes. The method ensures that kL and a are evaluated under consistent hydrodynamic conditions.Results from three different nonviscous systems show that at high agitation power, such that the average bubble diameter is between 0.2 and 2 mm, kL decreases with increasing power input and is dependent on the bubble diameter. This behavior is in contrast to the results of others at lower agitation levels or in nonelectrolytic liquids, but in general agreement with previous results for bubbles of the same diameter range produced in viscous, nonelectrolytic solutions.
Computer‐aided safety interlock systems
Authors: Rivas J. Roberto , Rudd Dale F. , Kelly Lloyd R. 
Published: June 2004

AbstractSince operation error is a major factor contributing to industrial disaster, it is necessary to develop safety interlock systems which prevent modes of operation that are known to be dangerous. It is not possible to foresee all the disruptions that might occur and, for this reason, an a priori analysis of safety problems is incomplete. At each step in operation the state of the process must be updated if hazardous conditions are to be avoided. To a large extent this is a problem in logic which can be handled rapidly by the computer using the methods developed here.
Measurement and prediction of high‐pressure phase equilibria with a dilute component in the gas phase: The methane‐n‐hexane system
Authors: Gunn Robert D. , McKetta John J. , Ata Nassar 
Published: June 2004

AbstractThe design of vapor recovery processes requires very accurate vapor‐liquid equilibria data. In this work the problem is attacked from both an experimental and a correlational viewpoint, and the methane‐n‐hexane system is chosen for study. A predictive model for vapor‐liquid equilibrium aids in the interpretation of the experimental measurements, and data acquired in this study agree closely with the theoretical predictions. Maximum deviation between calculated and experimental equilibrium ratios (yi/xi) is 8.5% with average absolute deviations of 3% for n‐hexane and 0.1% for methane. Several procedures are described for checking the accuracy of experimental VLE data when a heavy vapor is present at low concentrations in the gas phase. Several potential sources of experimental error are also identified and discussed.
Fast fluxes with supercritical solvents
Authors: Rance Robert W. , Cussler E. L. 
Published: June 2004

AbstractMeasurements of iodine dissolution rates in supercritical carbon dioxide and other supercritical fluids show when the iodine flux in these systems can be made fast. For these systems, the dominant factor in achieving this fast flux is the solubility; increases in diffusion coefficient have less effect. An approximate guide for estimating these fluxes is developed and compared with the experimental results.
Concentration profiles in free‐flow electrophoresis
Authors: Reis Joaquim F. G. , Lightfoot E. N. , Lee Ho‐Lun 
Published: June 2004

AbstractAn analysis is presented which enables detailed description of solute concentration profiles for free‐flow elecrophoresis in planar slit flows. This analysis is suitable for either batch or continuous operation with arbitrary variation of solute input rate, and it requires no seriously restrictive assumptions other than constancy of equilibrium and transport properties. It permits for the first time a systematic investigation of the effects of governing parameters and can be used to optimize operating conditions. The most significant finding is that Taylor dispersion, ignored in previous analyses, markedly reduces separability.
An effective numerical integration method for typical stiff systems
Authors: Aiken Richard C. , Lapidus Leon 
Published: June 2004

AbstractThere is an equivalence between stiff and singularly perturbed systems of ordinary differential equations. This feature is exploited in this paper by numerically employing recent singular perturbation methods to attack troublesome boundary layer stage of the solution in which some variables have very short response times. The numerical method affords a means of essentially determining the thickness of this boundary layer. The algorithm is capable of high stability and accuracy for the commonly occurring stiff system, whether or not it is in singularly perturbed form. Application to a singularly perturbed reaction system and a highly stiff reactor system not in singularly perturbed form demonstrate the effectiveness and utility of this approach.
Unsteady mass transfer in a long composite cylinder with interfacial resistances
Authors: Stevenson James F. 
Published: June 2004

AbstractA solution is given for unsteady state concentration profiles in an infinitely long composite cylinder resulting from a step‐change in concentration in a large reservoir surrounding the cylinder. The composite cylinder consists of an inner cylinder with diffusivity D1 surrounded by a permeable tube with diffusivity D2 and has interfacial mass transfer resistances at the cylinder‐tube and tube‐reservoir interfaces. Numerical values are given for the first eight roots and various coefficients of the solution for physical properties typical of tubular (hollow fiber) membranes. These results can be used in the analysis of data from unsteady state mass transfer experiments to determine the permeability of homogeneous tubular membranes. A simple, approximate method for data analysis is suggested for the rapid estimation of the permeability of both homogeneous and asymmetric (skinned) tubular membranes.
Simulation of the precipitation of silver bromide photographic emulsions
Authors: Margolis Geoffrey , Gutoff Edgar B. 
Published: June 2004

AbstractNucleation and crystal growth processes involved in the batch precipitation of photographic emulsions by the addition of silver nitrate to an aqueous solution of bromide and gelatin have been reasonably successfully modeled. Simulation predicts the known increase in average crystal size with increased addition time, with increased temperature, and with increased halide levels. Solubility is related to crystal size by the Gibbs‐Thomson equation. The predicted decrease in the number of crystals during the course of precipitation is similar to published data, but there are quantitative differences. The model is very sensitive to variations in the constant in the growth equation, but not to variations in the constants in the nucleation equation.
Synthesis strategies for multicomponent separation systems with energy integration
Authors: Rathore Ram N. S. , Van Wormer Kenneth A. , Powers Gary J. 
Published: June 2004

AbstractThe problem of synthesizing an optimal multicomponent separation system which is energy integrated is solved by a combined decomposition and dynamic programming technique.Dynamic programming is an optimization technique which allows the solution by decomposition of a multistage or serial optimization problem. Whenever the special serial structure is absent, again decomposition can be tried, but in this case it is by no means obvious how to decompose effectively the given problem into subproblems. In this paper the nonserial problem of synthesizing an energy integrated separation system is solved by decomposing the original problem so that a serial structure results.
Ignition on catalytic wires: Kinetic parameter determination by the heated‐wire technique
Authors: Rader C. G. , Weller S. W. 
Published: June 2004

AbstractA new analysis is presented for the extraction of Arrhenius parameters from experimental measurements of ignition temperatures during catalytic oxidation over electrically‐heated metal wires. Butane oxidation on high purity platinum wires has yielded reproducible experimental results for the reaction rate and has provided consistent estimates of the Arrhenius parameters. First‐order kinetics was assumed. The present treatment contains explicit consideration of: (1) the ohmic heating term; and (2) the end conduction heat loss from the catalytic wire. The effects of wire length, diameter, and configuration are reconciled when the ignition phenomenon is refferred to the center‐point temperature of the wire.
Sorption and diffusivity characteristics of acid‐leached mordenites
Authors: Satterfield Charles N. , Chiu George T. 
Published: June 2004

AbstractThe apparent diffusivity for the binary liquid systems benzene‐cumene and cyclohexane‐cumene in H‐mordenite crystals at 25°C to 44°C was increased by an order of magnitude or more after the zeolite was acid‐leached to increase the silica‐alumina mole ratio from the range of 14 to 18 to the range of 70 to 89. The calculated diffusivities, which range from 10−12 to 10−16 cm2/s, decrease with approach to sorption equilibrium and may be markedly reduced under some circumstances by adsorption of molecules from the bulk liquid, causing blockage of pores.Comparison of sorption capacities as a function of silica‐alumina ratio as reported by various investigators indicates that considerable differences exist in the properties of acid‐leached mordenites of the same silica‐alumina ratio but of different origins.
Stabilizing effects of surfactants on pseudoplastic falling films
Authors: Skelland A. H. P. , Popadic Vujadin O. 
Published: June 2004

AbstractThe effects of nonionic surfactants on thin‐film flow of pseudoplastic non‐Newtonian liquids down a smooth vertical plate have been studied experimentally. For all liquids examined there was a surfactant concentration at which the stabilizing action of surfactants was maximized. Comparison with experimental data showed that an existing equation, developed for the stabilizing action of surfactants on thin‐film flow of Newtonian fluids, may be used to predict the effect of surfactants on the stability of pseudoplastic thin‐film flow by using the zero‐shear rate apparent viscosity in place of the Newtonian viscosity.
Influence of crystal size on the rate of contact nucleation in stirred‐tank crystallizers
Authors: Bauer L. G. , Rousseau R. W. , McCabe W. L. 
Published: June 2004

AbstractThe purpose of this study was to investigate the influence of seed crystal size on the rate of nucleation in batch stirred‐tank crystallizers. Experimental results confirm the existence of such an effect. Nucleation rate data are correlated with a second‐order polynomial in seed crystal size; coefficients of the correlation are functions of the solute‐solvent system, crystallizer geometry, and mixing conditions. The empirical correlation is incorporated into a population balance model for determining the nucleation rate in multi‐seed crystallizers. The observed results are explained in terms of variations in impact energy, circulation frequency, and target efficiency.
Adsorption and kinetics in a batch heterogeneous catalytic reactor
Authors: Hsu Stephen M. , Kabel Robert L. 
Published: June 2004

AbstractThe utility of a new dynamic experimental technique is illustrated for the specific case of the vapor phase dehydration of ethanol over a hydrogen ion exchange resin. Adsorbed phase composition data are obtained simultaneously with complete vapor phase information, providing new insight into the catalytic behavior. A mathematical model, based upon Langmuir‐Hinshelwood kinetics, comprises simply five first‐order ordinary differential equations. The model describes all of the important transient and equilibrium characteristics of the reacting system qualitatively and most quantitatively. Experimental data alone are used to show that the surface reaction is the rate controlling step.
Application of quasilinearization to methane pyrolysis
Authors: Denis Gilles H. , Daubert Thomas E. 
Published: June 2004

AbstractThe rate constants appearing in differential equations derived from proposed mechanisms for methane pyrolysis were estimated from published integral conversion data. Quasilinearization, capable of fitting the differential equation solutions directly to the integral data and therefore not requiring differentiation or transformations, was used. Since differential equations representing free radical reactions have coefficients varying over many orders of magnitude, implicit numerical integration was used to obtain the numerous particular and homogeneous solutions required in the execution of the algorithm. Convergence was achieved by replacing the concentrations after each iteration with values near the solution at that point and by repeatedly estimating a small number of parameters in a cyclic manner in order to improve starting estimates of all parameters simultaneously. The mechanisms attempted were considered plausible when they led to adequate data fits and reasonable rate constant estimates. The major contribution of the work is that the algorithm is capable of testing a mechanistic model over a relatively wide range of conditions with minimal experimental data.