bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wave formation on a vertical falling liquid film
Authors: Alekseenko S. V. , Nakoryakov V. Ye. , Pokusaev B. G. 
Published: June 2004

AbstractThe method of integral relations is used to derive a nonlinear two‐wave equation for long waves on the surface of vertical falling liquid films. This equation is valid within a range of moderate Reynolds numbers and and be reduced in some cases to other well‐known equations.The theoretical results for the fastest growing waves are compared with the experimental results concerning velocities, wave numbers, and growth rates of the waves in the inception region. The validity of the theoretical assumptions is also confirmed by direct measurements of instantaneous velocity profiles in a wave liquid film.The results of the experimental investigation concerning nonlinear stationary waves and the evolution of initial solitary disturbances are presented.
An MILP formulation for heat‐integrated distillation sequence synthesis
Authors: Andrecovich M. J. , Westerberg A. W. 
Published: June 2004

AbstractIn this paper the problem of distillation sequence synthesis with heat integration is formulated and solved as a mixed integer linear superstructure optimization problem. Allowing both conventional and multieffect distillation, two alternatives for generating a superstructure are shown, then a formulation is presented which approximates the synthesis problem as a mixed integer linear programming (MILP) problem. Examples illustrate the method. Reported computer times suggest that earlier algorithmic methods for discovering the better sequences among those allowed by the problem formulation, and without the option of multieffecting, are an order of magnitude slower than this approach.
Utility bounds for nonconstant QΔT for heat‐integrated distillation sequence synthesis
Authors: Westerberg A. W. , Andrecovich M. J. 
Published: June 2004

AbstractIn earlier work the authors presented a simple method to synthesize heat‐integrated distillation sequences through the use of simple sketches on a diagram displaying temperature vs. enthalpy. Embedded in that work is the useful but in‐correct assumption that the reboiler/condenser heat loads and the temperature‐difference across the column are independent of the temperature (pressure) level at which the column is operated. This assumption of constancy is removed here, and it is shown how to calculate the minimum utility target using a small linear programming formulation. It is also shown how to use the results of this calculation to synthesize distillation sequences that approach the bound discovered. For the example problems solved, the minimum utility target calculated increases about 25 to 60% over that calculated assuming constant QΔT. The sequences synthesized based on this improved target are virtually the same as the constant QΔT method produces, suggesting that the earlier method is indeed a useful approach.
Finite amplitude waves in stratified two‐phase flow: Transition to slug flow
Authors: Ahmed Rafi , Banerjee Sanjoy 
Published: June 2004

AbstractIn horizontal two‐phase flow, transition from stratified to slug flow occurs due to the nonlinear instability of finite amplitude interfacial waves. The nonlinear equations describing interfacial waves in stratified two‐phase flow are solved by a multiple scales perturbation method. Instability criteria and amplification factors are determined. The phase velocities that are calculated to lead to amplification of finite amplitude interfacial waves are well below those based on linear stability criteria. This is in agreement with existing experimental data on transition from stratified to slug flow in horizontal channels.
Effects of intraparticle heat and mass transfer during devolatilization of a single coal particle
Authors: Bliek Alfred , Van Poelje W. M. , Van Swaaij W. P. M. , Van Beckum F. P. H. 
Published: June 2004

AbstractThe objective of the present work is to elucidate the influence of intraparticle mass and heat transfer phenomena on the overall rate and product yields during devolatilization of a single coal particle in an inert atmosphere. To this end a mathematical model has been formulated which covers transient devolatilization kinetics and intraparticle mass and heat transport. Secondary deposition reactions of tarry volatiles also are included. These specific features of the model allow a quantitative assessment to be made of the impact of major process conditions such as the coal particle size, the ambient pressure and the heating rate on the tar, gas and total volatile yield during devolatilization. Model predictions are compared to a limited number of experimental results, both from the present work and from various literature sources.
Gas separation by pressure swing adsorption: A pore‐diffusion model for bulk separation
Authors: Yang R. T. , Doong S. J. 
Published: June 2004

AbstractAn experimental and theoretical study is performed for bulk separation of gas mixture by pressure swing adsorption, a process widely used commercially for gas purification. By cycling the pressure of a bed of activated carbon between 3 and up to 500 psig (0.021 to 3.445 MPa), at the ambient temperature, a 50/50 H2/CH4 mixture is separated into two products with well over 90% purity and recovery at high throughputs. All process characteristics can be predicted by a pore‐diffusion model. A fundamental understanding of the function of each step in the cyclic process is given.
Diffusion of benzene, toluene, naphthalene, and phenanthrene in supercritical dense 2,3‐dimethylbutane
Authors: Sun C. K. J. , Chen S. H. 
Published: June 2004

AbstractThe conditions under which the Taylor‐Aris dispersion phenomenon can be employed to generate accurate tracer diffusion data in supercritical dense fluids are established. The technique is used to determine the diffusivities of benzene, toluene, naphthalene, and phenanthrene in supercritical dense 2,3‐dimethylbutane as a function of temperature and pressure. A molecular theory incorporating the Sung‐Stell formulation of molecular dynamic correlations in smooth‐hardsphere fluids and the Baleiko‐Davis molecular roughness for polyatomics with the Enskog‐Thorne dense gas diffusivity relationship is found to represent our experimental data to within ±4%. The values of the effective hard‐sphere diameters involved in the present theory can be predicted fairly accurately from the critical volumes of the solutes and solvent considered here.
Pressure swing adsorption. Part II: Experimental study of a nonlinear trace component isothermal system
Authors: Hassan M. M. , Raghavan N. S. , Ruthven D. M. , Boniface H. A. 
Published: June 2004

AbstractThe recently developed mathematical model for simulation of a PSA system (Raghavan et al., 1985) has been extended to a nonlinear Langmuir equilibrium system. The pressure swing adsorption separation of a small concentration of ethylene from helium has been studied experimentally on 4A and 5A molecular sieves. In the 4A system mass transfer is controlled by intracrystalline diffusion and is slow, whereas in the 5A system mass transfer is very much faster and is controlled by macropore diffusion. With rate and equilibrium parameters derived from experimental breakthrough curves, the theoretical model provides a good representation of the experimentally observed behavior of both PSA systems.
Effects of London‐van der Waals forces on the thinning and rupture of a dimpled liquid film as a small drop or bubble approaches a fluid‐fluid interface
Authors: Hahn Phil‐Soo , Chen Jing‐Den , Slattery J. C. 
Published: June 2004

AbstractWhen a small drop or bubble approaches a fluid‐fluid interface, a thin liquid film forms between them and begins to drain. As the thickness of the draining film become sufficiently small [about 1,000 Å (100 nm)], the effects of the London‐van der Waals forces and of the repulsive force of any electrostatic double layer become important. Lin and Slattery (1982b) developed a hydrodynamic theory for the first portion of the coalescence process: the drainage of the thin liquid film while it is sufficiently thick that the effects of London‐van der Waals forces and of electrostatic forces can be ignored. Here the effect of the London‐van der Waals forces are included. Given only the drop radius and the required physical properties, the configuration of the film as a function of time is predicted. For the case of a negative disjoining pressure, it is possible to estimate an upper bound for the coalescence time or the time during which a small drop or bubble appears to rest at a phase interface before it coalesces under the influence of London‐van der Waals forces.
Effect of air shear on gas absorption by a liquid film
Authors: McCready M. J. , Hanratty T. J. 
Published: June 2004

AbstractRates of oxygen absorption from turbulent air by a concurrently flowing liquid film were measured in an enclosed 2.54 cm × 30.5 cm rectangular channel. The effect of liquid viscosity is varied by using water and a water‐glycerine solution. The results are interpreted by arguing that flow fluctuations in the liquid that control mass transfer are associated with waves of small wavelength at the interface.
Aerosol reactor theory: Stability and dynamics of a continuous stirred tank aerosol reactor
Authors: Pratsinis S. E. , Friedlander S. K. , Pearlstein A. J. 
Published: June 2004

AbstractThe stability characteristics of an aerosol reactor in a continuous stirred tank configuration have been investigated theoretically. Three dimensionless parameters, the surface tension group ∑, reaction rate group R, and residence time group θc, suffice to determine the dynamic behavior of this system. The stability of the unique steady state was investigated using linear analysis. Numerical integration of the full nonlinear equations shows that the dynamic behavior was in accord with the predictions of the linear stability theory. The system exhibits limit‐cycle behavior in the unstable part of the parameter space. In the unstable region, a simple linear relation was found between the period of the numerically computed solutions and the bifurcation parameter, θc. The results of this study are in qualitative agreement with the experimental results of Badger and Dryden (1939).
Theory of electrophoretic separations. Part II: Construction of a numerical simulation scheme and its applications
Authors: Palusinski O. A. , Graham A. , Mosher R. A. , Bier M. , Saville D. A. 
Published: June 2004

AbstractThe mathematical model outlined in Part I is recast in a form suitable for numerical computation. The spatial derivatives are replaced by finite‐difference expressions, which leads to a set of ordinary differential equations coupled to a set of nonlinear algebraic relations. This system is solved using existing integration techniques. The resulting algorithm simulates the characteristic behavior of the classical modes of electrophoresis, which is shown by examples involving moving boundary electrophoresis and isoelectric focusing. In the first example two different integration schemes are used and their accuracy and stability investigated. The second example illustrates the versatility of the methodology.
Computer simulation of a rotary dryer. Part I: Retention time
Authors: Kamke F. A. , Wilson J. B. 
Published: June 2004

AbstractA computer model of a single‐pass, rotary‐drum dryer with or without a center‐fill flighting section, describes the drying behavior of wood particles within the drum. This part of a two‐part study examines retention time; the second part incorporates heat and mass transfer for the complete drying model. Simulation results with retention time data from a large‐scale rotary dryer showed a favorable comparison, with a root mean square error of 14.2%.
Computer simulation of a rotary dryer. Part II: Heat and Mass Transfer
Authors: Kamke F. A. , Wilson J. B. 
Published: June 2004

AbstractA computer model of a single‐pass, rotary‐drum dryer with or without a centerfill flighting section, describes the drying behavior of wood particles within the drum. This part of a two‐part study examines heat and mass transfer, which are shown to be partly dependent on the pattern of particle flow and on retention time. Comparison of simulation results with drying data based on moisture content of outlet particles from a large‐scale rotary dryer was favorable, with a root mean square error of 22.2%.
A local composition model for the excess Gibbs energy of aqueous electrolyte systems
Authors: Chen Chau‐Chyun , Evans L. B. 
Published: June 2004

AbstractThe electrolyte nonrandom two‐liquid (NRTL) model proposed by Chen et al. (1982) is generalized to represent the excess Gibbs energy of aqueous multicomponent electrolyte systems. Using only binary parameters, the model correlates and predicts the deviation from ideality of aqueous multicomponent electrolyte systems over the entire range of temperature and concentration.
A mixed‐integer nonlinear programming algorithm for process systems synthesis
Authors: Duran M. A. , Grossmann I. E. 
Published: June 2004

AbstractThe problem of synthesizing processing systems via simultaneous structural and parameter optimization is addressed in this paper. Based on a superstructure representation for embedding alternative configurations, a general mixed‐integer nonlinear programming (MINLP) framework is presented for the synthesis problem. An efficient outer‐approximation algorithm is described for the solution of the underlying optimization problem, which is characterized by linear binary variables and continuous variables that appear in nonlinear functions. The proposed algorithm is based on a bounding sequence that requires the analysis of few system configurations, and the solution of a master problem that identifies new candidate structures. Application of the proposed algorithm is illustrated with the optimal synthesis of gas pipelines.
Interfacial area generated in aqueous electrolyte solutions on a sieve plate
Authors: Pohorecki Ryszard , Nowosielski Jan 
Published: June 2004

AbstractA light depolarization method was used to measure the interfacial area of froth on a sieve plate. The effects of hydrodynamics and the presence of electrolytes on the magnitude of the interfacial area were studied. The results obtained for pure water and for two different aqueous solutions of inorganic salts were compared. In the case of aqueous electrolyte solutions the size distributions of ionic bubbles and the fraction of interfacial area contributed by these bubbles were determined by a photographic method. It was found that the interfacial area generated in aqueous electrolyte solutions was considerably (about 30%) greater than the interfacial area generated in pure water, and that about 45% of the total interfacial area in the former case was contributed by ionic bubbles which formed a separate population.
Drop breakup in turbulent stirred‐tank contactors. Part II: Relative influence of viscosity and interfacial tension
Authors: Wang C. Y. , Calabrese R. V. 
Published: June 2004

AbstractThe relative influence of dispersed‐phase viscosity and interfacial tension on equilibrium drop size and drop size distribution is studied for dilute suspensions by dispersing various silicone oils in water, methanol, and their solutions. Correlations for Sauter mean diameter, D32, are developed in terms of system variables using the mechanistic models of Part I. Drop sizes for low to moderate viscosity dispersed phases are normally distributed in volume and can be correlated by normalization with D32. Trends in the distributions are explained in terms of a parameter representing the relative resistance to breakage.
Effects of finely divided solids on mass transfer between a gas and an organic liquid
Authors: Bartos T. M. , Satterfield C. N. 
Published: June 2004

AbstractGlobal gas‐liquid mass transfer parameters, kLa and a were determined in an organic liquid in which finely divided solid particles were suspended in a mechanically stirred vessel. The product kLa and a both decreased linearly with solids loading; both were independent of particle size and particle density. Gas holdup was independent of solids loading.
Separation of fine particle dispersions using periodic flows in a spining coiled tube
Authors: Papanu J. S. , Adler R. J. , Gorensek M. B. , Menon M. M. 
Published: June 2004

AbstractA centrifugal method for fractionating fine (<10 μm) particles by size and/or density is described. Periodic, bidirectional flow through a continuously spinning coiled tube splits fine particle suspensions into two fractions. Proof‐of‐principle experiments with zeolite powder have demonstrated successful concentration of aqueous dispersions.
Vertical upward cocurrent gas‐liquid annular flow
Authors: Zabaras G. , Dukler A. E. , Moalem‐Maron D. 
Published: June 2004

AbstractUpward cocurrent gas‐liquid annular flow was investigated in a 50.8 mm ID cylindrical vertical pipe. The film flow was studied by measuring instantaneous local film thickness, wall shear stress, and pressure gradient. Analysis of these data revealed that at low gas flow rates the film motion is controlled by a switching mechanism, as speculated by Moalem‐Maron and Dukler (1984). In the region of high gas flow rates the switching process is suppressed and traveling roll waves characterize the film motion.
Mass transfer and electrochemical kinetic interactions in localized pitting corrosion
Authors: Gaudet G. T. , Mo W. T. , Hatton T. A. , Tester J. W. , Tilly J. , Isaacs H. S. , Newman R. C. 
Published: June 2004

AbstractIdentification and characterization of coupled diffusional and electrochemical kinetics effects was achieved under potentiostatic anodic dissolution conditions. A one‐dimensional artificial pit geometry with sample wire electrodes embedded in an inert support exposed to NaCl solutions was used to study the dissolution of stainless steel and highnickel Alloy 600. Multiple steady states for both materials were determined at conditions where the diffusional transport rates balanced the electrochemical rate of dissolution at the surface of the wire electrode. A theoretical transport model was developed to quantitatively explain the observed multiple steady state phenomena.
Interaction analysis in multivariable control systems
Authors: Jensen N. , Fisher D. G. , Shah S. L. 
Published: June 2004

AbstractMost published “interaction measures” can produce misleading results and often do not measure the true closed‐loop interaction. Therefore, closed‐loop transmittances are defined mathematically as direct, parallel, disturbance, and interaction transfer functions and it is shown that the direct Nyquist array design method includes an excellent basis for interaction analysis.
Rapid computation of chemical equilibrium composition: An application to hydrocarbon combustion
Authors: Erickson W. D. , Prabhu R. K. 
Published: June 2004

AbstractA scheme for rapidly computing the chemical equilibrium composition of hydrocarbon combustion products is derived. A set of ten governing equations is reduced to a single equation that is solved by the Newton iteration method. Computation speeds are approximately 80 times faster than the often used free‐energy minimization method. The general approach also has application to many other chemical systems.
Immobilization of enzymes in porous solids under restricted diffusion conditions
Authors: Hossain Md. M. , Do D. D. , Bailey J. E. 
Published: June 2004

AbstractA restricted diffusion model is developed to study the immobilization of enzyme in porous solid supports. Simulation studies have been carried out for various combinations of process variables and parameters of the immobilization system. The model has also been used to develop a method for estimating the intrinsic rate constant of immobilization when enzyme diffusion into the support is restricted. Results of experiments in which glucose oxidase was immobilized in porous glass supports are consistent with model simulations.
Diffusion in solids under strain, with emphasis on polymer membranes
Authors: Neogi P. , Kim Myungsoo , Yang Yun 
Published: June 2004

AbstractA solute diffusing through a solid gives rise to a change in volume. This swelling can be viewed as a strain, and it is possible to obtain the accompanying stress using elasticity theory. The theory provides two ways by which stresses can be generated. The first comes from the condition of impenetrability where the system generates stress to exclude certain configurations during deformation. The second is due to imposed restrictions on the geometry during the swelling process. Larché and Cahn have provided the thermodynamics for such systems, from which the chemical potential can be used to obtain a phenomenological expression for flux and an expression for the solubility. These two are sufficient to obtain the sorption response in most systems. Solutions have been obtained here.
Connectivity effects for surface diffusion of adsorbed gases
Authors: Zgrablich G. , Pereyra V. , Ponzi M. , Marchese J. 
Published: June 2004

AbstractNonlocal models for the surface transport of adsorbed gases on solids are proposed and compared to experimental data. These models take into account connectivity effects due to heterogeneous adsorption potential surfaces and introduce a more realistic calculation of the surface mean free path.
Liquid phase oxidation kinetics of oil sands bitumen: Models for in situ combustion numerical simulators
Authors: Adegbesan K. O. , Donnelly J. K. , Moore R. G. , Bennion D. W. 
Published: June 2004

AbstractMultiresponse kinetic models are established for the low‐temperature oxidation (LTO) reactions of Athabasca oil sands bitumen. The models provide adequate description of the overall rate of oxygen consumption and of the reactions of the liquid phase bitumen components. The LTO models are suitable for use in the in situ combustion numerical simulators of the oil sands.
Multicomponent adsorption equilibria of nonideal mixtures
Authors: Talu Orhan , Zwiebel Imre 
Published: June 2004

AbstractExperimental gas‐solid adsorption measurements were made on the binary and ternary mixtures of H2S, CO2, and C3H8 on H‐mordenite molecular sieve zeolite at 30°C. The C3H8 containing binaries and the ternary mixture exhibited nonideal behavior, as evidenced by the azeotropelike crossovers in the composition domains and by the peaks in the total amount adsorbed surface. The ternary data were successfully predicted with the activity coefficients calculated by the spreading‐pressure‐dependent equation. Models that neglect the spreading‐pressure dependence can only qualitatively predict the nonidealities.
Effect of convective heat transfer and phase change on the stability of aluminium smelting cells
Authors: Taylor M. P. , Welch B. J. , McKibbin R. 
Published: June 2004

AbstractThis paper focuses on two aspects of smelting operation that are highly dependent on the rate of heat transfer in the molten bath. As a consequence of the elevated temperature and the corrosive nature of the fluoride mixture, the cell sidewalls are designed so that some electrolyte will freeze onto them, protecting the carbon from erosion and at the same time insulating the cell against excessive heat loss. The thickness and dynamic variation of this frozen ledge are determined by the convective heat transfer from the bath to the freeze surface.Another situation where the rate of convective heat flow exerts a subtle influence is the dissolution of aluminium oxide powder in the bath. The localized feeding of large quantities of the powder causes transient electrolyte freezing on some of the added material, hindering its dissolution and causing the formation of an alumina sludge below the molten aluminium pad.
Droplet entrainment in vertical annular flow and its contribution to momentum transfer
Authors: Lopes J. C. B. , Dukler A. E. 
Published: June 2004

AbstractSimultaneous measurements were made of the size and the axial and radial velocity of drops entrained by the gas in annular flow. A model is developed to use these data to compute the rate of deposition or entrainment and the pressure gradient, ▽ρE, due to drop interchange. ▽ρE is a significant fraction of the measured total gradient, ▽ρ.