bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mathematical models of the monolith catalytic converter: Part II. Application to automobile exhaust
Authors: Young Larry C. , Finlayson Bruce A. 
Published: June 2004

AbstractCalculations are done for a series of mathematical models for a monolith catalytic converter to oxidize carbon monoxide in automobile exhaust. Phenomena studied include axial conduction in the wall, diffusion and conduction in the gas in a transverse direction perpendicular to the flow direction, multiple steady states, and transients giving wall temperatures exceeding the adiabatic temperature.
Digital monitorina and estimation of polymerization reactors
Authors: Jo J. H. , Bankoff S. G. 
Published: June 2004

AbstractA free‐radical polymerization with kinetic equations taking into account monomer, polymer, and solvent transfer and initiation, termination, propagation, and inhibition reactions was studied both experimentally and by simulation to determine the performance of various Kalman filters, with feasible measurements used.
Mathematical modeling of monolithic catalysts
Authors: Heck Roland H. , Wei James , Katzer James R. 
Published: June 2004

AbstractMathematical models are developed which account for simultaneous heat transfer, mass transfer, and chemical reaction in the oxidation of carbon monoxide over platinum containing monoliths. A two‐dimensional model is shown to predict unusual behavior of the Nusselt number in the presence of rapid reaction. However, a simpler one‐dimensional model is adequate for predicting monolith behavior.
Mass transfer to drops moving through power law fluids in the intermediate reynolds number region
Authors: Wellek Robert M. , Gürkan Türker 
Published: June 2004

AbstractThe mass transfer rate to fluid spheres is calculated for power law and Newtonian fluids by using the intermediate Reynolds number stream functions of Nakano and Tien (1970) and Yamaguchi et al. (1974), respectively. The Sh increases with increases in Re and Pe and decreases in n. Better results are obtained with Nakano and Tien's functions when Re > 10 and with Yamaguchi's functions when Re < 10.
An effective computational algorithm for suboptimal singular and/or bang‐bang control I. Theoretical developments and applications to linear lumped systems
Authors: Nishida N. , Liu Y. A. , Lapidus Leon , Hiratsuka S. 
Published: June 2004

AbstractA new and simple computational algorithm for obtaining suboptimal singular and/or bang‐bang solutions of typical lumped and distributed parameter control problems is proposed. The algorithm is based on the piecewise maximization of the Hamiltonian and a limiting process utilizing a penalty function of the control variables. Theoretical developments and computational applications of the algorithm to several linear lumped parameter control problems are presented. Extensions and applications of the algorithm to nonlinear and distributed parameter systems are given in Part II.
Interfacial phenomena in falling film evaporation of natural seawater
Authors: Van Der Mast Victor C. , Bromley Leroy A. 
Published: June 2004

AbstractThe fluid dynamics and heat transfer of boiling seawater in falling film evaporators have been investigated. Large interfacial disturbances have been observed, caused by surfactants in seawater. Although these disturbances enhance heat transfer, they increase entrainment and the tendency for scale formation in fluted tubes.
The steady and unsteady state analysis of a simple gas centrifuge
Authors: Auvil Steven R. , Wilkinson Bruce W. 
Published: June 2004

AbstractThe operating theory of the gas centrifuge is developed under both steady and unsteady state behavior. It is shown that countercurrent flow patterns in a gas centrifuge enhance the possible separation. The effect of self‐diffusion of the gaseous mixtures is shown to be significant with low molecular weight gases but of less significance with heavy gases such as uranium isotopes. The time required to develop steady state pressure and concentration profiles is in the order of minutes, even with no net flow to and from the machine.
Development and application of a simulation model for three‐phase distillation
Authors: Block Ulrich , Hegner Bernd 
Published: June 2004

AbstractThe model of the multicomponent, multistage distillation column has been extended to three coexisting phases. The new model contains the well‐known modeling equations of the two‐phase distillation column as a special case. The versatility of the new simulation model is demonstrated with practical distillation problems.
The effect of surfactant on the terminal and interfacial velocities of a bubble or drop
Authors: Leven M. Douglas , Newman John 
Published: June 2004

AbstractStream functions are dervied for a spherical droplet in creeping flow with an arbitary surface tension gradient at its interface. The stream functions are used to show theoretically that the terminal velocity is reduced and that the interfacial velocity is retarded, especially near the rear of the droplet, when a trace of surfactant is present in the exterior phase and when surface aging is controlled by diffusion.
A method of moments for measuring diffusivities of gases in polymers
Authors: Felder R. M. , Ma C‐C , Ferrell J. K. 
Published: June 2004

AbstractA method of moments has been formulated for the determination of the diffusivity of a gas in a polymer from a step response in a continuous permeation chamber. Contributions of system components other than the polymer are easily factored out to determine the contribution of the polymer alone, and this contribution is then analyzed to calculate the diffusivity. The method has been applied to the measurement of the diffusivities of sulfur dioxide in PTFE (Teflon) and fluorosilicone rubber tubes over a wide temperature range.
Relationships between velocity profiles and drag reduction in turbulent fiber suspension flow
Authors: Lee Peter F. W. , Duffy Geoffrey G. 
Published: June 2004

AbstractAnalytical relationships between velocity profiles and flow resistance data are developed for suspensions of papermaking fibers in turbulent shear. The relationships apply to suspensions of synthetic fibers. The wall layer appears to be unaffected by the presence of fibers, and the cause of drag reduction can be attributed to the turbulent core region.
The hydrodynamic resolution of optical isomers
Authors: Howard D. W. , Lightfoot E. N. , Hirschfelder J. O. 
Published: June 2004

AbstractA potentially simple and effective technique is proposed for separating enantiomorphic crystal pairs from each other, or separating individual enantiomorphs from optically active impurities.This method consists essentially of settling under conditions controlling orientation of the asymmetric particles and taking advantage of the tensorial nature of their friction factors.
Scopolamine permation through human skin in vitro
Authors: Chandrasekaran S. K. , Michaels A. S. , Campbell P. S. , Shaw J. E. 
Published: June 2004

AbstractThe sorption and rate of permeation of scopolamine base in human skin have been measured as a function of drug concentration in aqueous solution contacting the stratum corneum surface of the skin. The sorption isotherm is nonlinear, and the apparent penetrant diffusivity computed from steady state permeation data is greater than that estimated from unsteady state (time lag) measurements.By assuming that sorption occurs by both ordinary dissolution and binding of penetrant to immobile sites in the membrane, the experimental sorption isotherm can be predicted, and the disparity between steady state and time lag diffusivities can be reconciled.
Denitrification kinetics in packed beds
Authors: Parker A. L. , Sikora L. J. , Hughes R. R. 
Published: June 2004

AbstractBench scale packed columns were used to study the kinetic behavior of biological denitrification. After tracer studies were run to determine flow characteristics, steady state nitrate profiles were determined. A first‐order rate expression with an Arrhenius temperature dependence is an adequate model of the reaction for nitrate‐nitrogen concentrations of < 100 mg/l and temperature of 5° to 20°C. The rate constants are proportional to the packing surface area.
On the dynamics of fluid interfaces. Part II
Authors: Ramabhadran T. E. , Byers Charles H. , Friedly John C. 
Published: June 2004

AbstractUltra high‐speed motion picture photography is used to measure the decay and frequency of drops of liquid in air and of air cavities in liquids. Consequent to the belief that surface active agents induce dynamic interfacial properties, a very clean system is used, and experiments are performed with triple distilled water, tap water, and known aqueous solutions of ionic and nonionic surfactants. Experimental results yield good qualitative agreement with the theory. The theoretical and experimental studies show the system to be a new and promising technique for the quantitative evaluation of the various interfacial viscous and elastic properties.
Diffusion of hydrocarbons in 13X zeolite
Authors: Ruthven Douglas M. , Doetsch Ingo H. 
Published: June 2004

AbstractThe kinetics of sorption of four representative hydrocarbons in 13X zeolite crystals have been investigated at temperatures within the range 409 to 513°K and pressures 0.1 to 100 torr. Extensive diffusivity data are presented showing the dependence on sorbate concentration and temperature. The form of the concentration dependence of the diffusivity for these systems is very similar to that of the small monatomic and diatomic molecules in 5A zeolite. This similarity is understandable, since the key factor which determines the diffusion behavior is the relative size of diffusing molecule and sieve window. For these hydrocarbons in the 13X sieve, as for the monatomic and diatomic gases in 5A, the critical diameters of the diffusing molecules are all appreciably smaller than the free diameter of the windows.
Growth and dissolution of potash alum crystals in the subsieve size range
Authors: Garside John , Jančić Slobodan J. 
Published: June 2004

AbstractOverall growth and dissolution rates of potash alum crystals have been measured over the size range 3 to 70 μm. The derived surface integration growth kinetics, which are found to be linear with respect to supersaturation and strongly size dependent, are evaluated in terms of the step model of crystal growth. The results emphasize the importance of independently measuring growth kinetics before secondary nucleation kinetics can be calculated from MSMPR experiments.
A new tracer method for determination of liquid‐solid contacting efficiency in trickle‐bed reactors
Authors: Schwartz J. G. , Weger Eric , Duduković M. P. 
Published: June 2004

AbstractA new tracer technique is reported for the determination of liquid‐solid contacting efficiency and liquid holdup in trickle beds packed with small alumina particles. Holdup was a function of liquid mass velocity for both porous and nonporous packing. Contacting efficiency remained uniform at a level of 65%.
Selective hydrogenation and mass transfer in a fixed‐bed catalytic reactor with gas‐liquid concurrent upflow
Authors: Mochizuki Satoshi , Matsui Tatsuro 
Published: June 2004

AbstractReaction rates of selective hydrogenation of phenylacetylene (PA) and styrene were studied in a packed‐bed reactor with concurrent gas and liquid upflow. The surface reaction rates were expressed by the reaction between adsorbed PA or styrene and dissociated hydrogen atoms competing for the same active sites. The contributions of mass transfer rate were determined, and better selectivity conditions were discussed.
Adsorption of nitric oxide in aqueous slurries of activated carbon: Transport rates by moment analysis of dynamic data
Authors: Niiyama Hiroo , Smith J. M. 
Published: June 2004

AbstractMoment analysis of input‐response data for three‐phase slurry reactors is shown to be useful for detrmining mass trasnport rate coefficients. Data for the nitric oxide‐water activated carbon system indicated that bubble‐to‐liquid transport, intraparticle diffusion, and the adsorption step could all influence the adsorption rate for high concentrations of carbon particles.
On the optimization by boundary control of tubular reactors with catalyst decay
Authors: Gruyaert Frans , Crowe C. M. 
Published: June 2004

AbstractIn optimization problems dealing with catalytic reactors, where the catalyst deactivates slowly with time, it is common to assume a quasi steady state in the reaction and deactivation equations. Although the difference in reactor performance, for a given control policy, between the unsteady state reactor and its quasi steady state approximation is usually negligible, a very large difference can exist in the optimal control policy for the two models. For a single irreversible reaction, where the catalyst deactivation is dependent on conversion and where the control variable is the temperature of the fluid entering a tubular reactor, it is shown numerically that the performance of the reactor for a suboptimal control policy can be significantly superior to the optimal performance predicted from a quasi steady state model formulation.
Equilibrium staged parametric pumping. I. Single transfer step per half‐cycle and total reflux—the analogy with distillation
Authors: Grevillot Georges , Tondeur Daniel 
Published: June 2004

AbstractEquilibrium staged batch parametric pumps are studied with nonlinear isotherms. The half cycle is composed of one single equilibration step and one discrete transfer. The limiting regime (for infinite number of cycles) is shown to correspond to a staircase construction between the two isotherms, the number of steps being equal to the number of stages. The reservoir concentrations are then connected by Fenske's equation. Several analogies with binary total reflux distillation are suggested.
The modeling of hematite reduction with hydrogen plus carbon monoxide mixtures: Part II. The direct reduction process in a shaft furnace arrangement
Authors: Tsay Q. T. , Ray W. H. , Szekely Julian 
Published: June 2004

AbstractA mathematical model was developed for the direct reduction of hematite carried out in a countercurrent moving packed bed, and the process was simulated on a CDC 6400 computer. The response of the model to changes in the various process variables was investigated, and it was found that there is an optimum gas inlet composition (hydrogen‐carbon monoxide) for a given set of operating conditions. In addition, an optimum gas inlet temperature was revealed for cases where pure carbon monoxide was used as the reducing gas. The feasibility of side stream injection of reducing gas was studied. The calculations showed that there are certain ranges of operating conditions for which the injection of a hot side stream is advantageous. This study represents the first reported simulation of direct reduction process having carbon monoxide‐hydrogen gas mixtures as a reducing medium.
Steady state diffusion of oxygen in red blood cell and model suspensions
Authors: Stroeve Pieter , Colton Clark K. , Smith Kenneth A. 
Published: June 2004

AbstractExperimental measurements were made of the steady oxygen permeation rate through films of nonreactive and reactive dispersions, including suspensions of red blood cells. The data compare well with a theoretical analysis which incorporates a one‐step reversible reaction within the dispersed phase. In the absence of reaction, the red cell permeability could be treated as that of a concentrated hemoglobin solution. For reactive suspensions of red cells or water‐in‐oil emulsions containing hemoglobin at 25°C, substantial facilitation of oxygen transport occurred when oxyhemoglobin gradients were steep, but both the data and the theory exhibited considerably less facilitation than would be suggested by an equilibrium analysis.
Enzymatic regeneration of ATP: II. Equilibrium studies with acetate kinase and adenylate kinase
Authors: Langer Robert S. , Gardner Colin R. , Hamilton Bruce K. , Colton Clark K. 
Published: June 2004

AbstractEquilibria of reactions catalyzed by acetate kinase and adenylate kinase were studied experimentally and theoretically. Nucleotide conversions in excess of 90% were obtained with reactants (acetyl phosphate and one nucleotide) in stoichiometric proportion for ATP regeneration from either ADP via acetate kinase or AMP via the coupled enzyme system. Observed equilibrium constants, measured as a function of [Mg2+] at pH 7.4, ranged from about 1 to 9 for the reaction catalyzed by adenylate kinase and from about 50 to 400 for the reaction catalyzed by acetate kinase. These results agreed well with prediction of a theoretical model for the multiple equilibria between all species present in solution. Theoretical calculations showed that magnesium ion complexes and totally dissociated anions are the predominant species in solution at \documentclass{article}\pagestyle{empty}\begin{document}$p{\rm H}\tilde > 7{\rm and}[{\rm Mg}^{2 + } ]\tilde > 10^{ - 3} {\rm M}$\end{document}.
Fluid vortices and mass transfer in a curved channel artificial membrane lung
Authors: Gilroy Keith , Brighton Elspeth , Gaylor John D. S. 
Published: June 2004

AbstractExperimental assessment of theory on the convective dispersion of blood gases by vortices in a curved channel exchanger has demonstrated the impracticality of the proposed design. A nonlinear stability analysis of the fluid dynamics provided an amplitude factor an order of magnitude less than that previously assumed for the system secondary circulations.
A compartmental dispersion model for the analysis of mixing in tube networks
Authors: Ultman James S. , Blatman Hal S. 
Published: June 2004

AbstractA compartmental dispersion model of longitudinal mixing in tube networks has been developed. The ability of this model to predict the impulse response of helium, benzene vapor, and sulfur hexafluride tracer gases in two and in five generation symmetric network models of the large airway system of the lung has been tested over an air flow range of 1 to 400 ml/s.The results imply that velocity profile distortion and secondary flows in branching regions have only a small effect upon the overall longitudinal mixing when flow is directed toward the higher‐order generations. On the other hand, accurate prediction of the data requires adequate treatment of the finite rate of evolution of the Taylor dispersion occurring in these tube networks.
Nonisothermal nip flow in calendering operations
Authors: Dobbels Frans , Mewis Jan 
Published: June 2004

AbstractAn efficient and simple numerical technique is presented for analyzing nonisothermal nip flow of viscous liquids. It has been applied on calendering to calculate the design parameters as well as the interaction effects between roller characteristics, operation conditions, and material properties. Viscous heating is shown to drastically change the mechanics near the nip exit if the rollers rotate at different speeds. Consequences for scaling‐up and model experiments are indicated.
Use of trajectory analysis to study stability of colloidal dispersions in flow fields
Authors: Zeichner G. R. , Schowalter W. R. 
Published: June 2004

AbstractTrajectories have been computed for two equal sized spherical particles in simple laminar shearing and in uniaxial extensional flows. Effects of interparticle attraction, electrostatic repulsion, and hydrodynamics were included.The results are pertinent to questions of colloidal stability under various conditions of flow. Particulate dispersions can react in several different ways as the intensity of shearing is increased from zero: the dispersion can remain stable; it can be redispersed, if it had been initially flocculated into a weak secondary minimum in the interparticle potential curve; it can be flocculated into a strong primary minimum in the potential curve; or, in extreme cases, it can be redispersed from the primary minimum. Results are presented which illustrate criteria for flocculation or stability to both laminar shearing and extensional flow. It is shown that hydrodynamic effects can significantly alter the criteria developed for stability of dispersions to Brownian coagulation.
Limiting criteria for intrinsically stable equilibrium in multiphase, multicomponent systems
Authors: Slattery John C. 
Published: June 2004

AbstractNecessary and sufficient conditions for intrinsically stable equilibrium in a multiphase, multicomponent body are developed with interfacial effects taken into full account. There is a limiting criterion for intrinsic stability that must be satisfied within every phase, and there is another limiting criterion that must be satisfied on every phase interface. The limits of intrinsic stability for a multiphase, multicomponent body are defined by the failure either of the first criterion within one of the phases or of the second criterion on one of the phase interfaces.
Liquid diffusion in microporous alumina pellets
Authors: Prasher Brahm D. , Ma Yi Hua 
Published: June 2004

AbstractThe effect of the ratio of the molecular solute diameter to the pore diameter and adsorption equilibrium on the liquid phase effective diffsivity for different hydrocarbon solutes was studied in two alumina pellets. A semiemprical correlation based on the relative dimension of the solute molecule with respect to the average pore dimension, the equilibrium partition coefficient, and the porosity is proposed for a variety of binary hydrocarbon systems. The correlation shows that the effective diffusivity is strongly influenced by both the adsorption coefficient as well as the ratio of the solute molecular size to the average pore size.
Combustion kinetics in the modeling of large, pulverized fuel furnaces: A numerical experiment in sensitivity
Authors: Lowe Allen , Wall Terry F. , Stewart Ian McC. 
Published: June 2004

AbstractA mathematical model of combustion in a utility type of pulverized, coal fired furnace is developed by dividing the furnace into a number of isothermal zones. The method dovetails the combustion rate data available for single char particles with a gas flow pattern to predict local combustion heat release rates and local radiation absorption coefficients, which are used as input to a zoned heat transfer model.The furnace heat transfer is shown to be insensitive to combustion related parameters such as coal rank and coal fineness. For carbon in ash, local gas temperature, and to a lesser extent local heat flux, significant variations are predicted. It is concluded that for calculation of radiative heat transfer, combustion data are adequate. Further research activity on ignition and combustion stability, together with the radiative properties of fly ash, is recommended.
Influence of drag reducing polymers on turbulent mass transfer to a pipe wall
Authors: McConaghy George A. , Hanratty Thomas J. 
Published: June 2004

AbstractCompletely developed and entry region mass transfer rates in turbulent pipe flow of drag reducing polymer solutions were studied experimentally using electrochemical techniques. The percent change in the fully developed mass transfer rate at a given volumetric flow was found to be greater than the percent change in the pressure gradient. The data are interpreted by using the law of the wall, valid for Newtonian fluids at large Schmidt numbers, whereby K+ is related to Sc−0.74. The proportionality constant is correlated with percent drag reduction and is found to decrease with increasing drag reduction. The use of an analogy between momentum and mass transfer predicts a somewhat greater mass transfer reduction than was observed.