bluuebunny/crossref_metadata_2025_split huggingface dataset:
Decomposition of systems of nonlinear algebraic equations
Authors: Shacham Mordechai 
Published: June 2004

AbstractA new method for decomposing irreducible subsets, in the solution of systems of nonlinear algebraic equations, is presented. This method consists of two steps: (1) elimination of the nonlinearity from some of the equations by replacing nonlinear expressions by new variables; and (2) formulation of a problem of smaller dimension by tearing the linear subset of equations. It is shown that these modifications do not change considerably the convergence rate of the Newton‐Raphson and Broyden's methods while reducing the problem's dimension. Computer time reduction up to 80% is demonstrated in the examples solved. An algorithm for elimination of nonlinear expressions, which uses Boolean matrices instead of formula manipulation, is also presented.
Mass transfer and pressure drop in a cocurrent reciprocating plate extraction column
Authors: Noh S. H. , Baird M. H. I. 
Published: June 2004

AbstractA 5‐cm‐diameter reciprocating plate extraction column has been operated in cocurrent flow. The pressure drop for water flow, and the local and average mass transfer products for the system acetic acid/kerosene/aqueous sodium hydroxide have been measured. Under well‐agitated conditions, the mass average transfer product is predictable by a model, which is also applicable to data reported earlier by Karr for a 2.54‐cm‐diameter column.
Estimation of critical properties with group contribution methods
Authors: Klincewicz K. M. , Reid R. C. 
Published: June 2004

AbstractCurrently available group‐contribution methods for Tc, Pc, and Vc were evaluated using the Ambrose (1980) critical property data compilation. The Ambrose estimation methods were found to be the most accurate. Linear regression methods were also employed to develop alternate estimation methods which were found to have an accuracy comparable to those of Ambrose.
Calculation of aerosol collection in fluidized filter beds
Authors: Ushiki K. , Tien Chi 
Published: June 2004

AbstractA method is proposed for calculating aerosol collection in fluidized filter beds. The method employs the bubble assembly model of fluidization and considers the bed to be a series of compartments, each of which comprises two or three phases. Aerosol collection is assumed to occur in these phases in accordance with existing theories of particle deposition. The validity of the method is tested against available experimental data.
Effective utilization of equations of state for thermodynamic properties in process simulation
Authors: Mathias P. M. , Boston J. F. , Watanasiri S. 
Published: June 2004

AbstractThermodynamic property computations using equations of state first require computation of the density root. Since higher level calculations such as single‐stage flash, distillation and data regression are usually performed iteratively, properties are often demanded at conditions where the appropriate density root does not exist. A strategy of returning suitable pseudoproperties under such conditions is proposed. It has been successfully used in ASPEN (Advanced System for Process Engineering), a general process simulator developed at the Massachusetts Institute of Technology.
Multivariable computer control of a butane hydrogenolysis reactor: Part II: Design and on‐line implementation of a stochastic controller using an identified multivariate noise model
Authors: Jutan Arthur , Wright J. D. , MacGregor J. F. 
Published: June 2004

AbstractA multivariable stochastic controller is implemented on a pilot scale, plug flow, butane hydrogenolysis reactor. In the synthesis of the controller, a multivariate time series model of the process disturbances is used. The success of this controller is compared to a previous controller where the process disturbances are not directly modeled.
Dispersion, mass transfer and chemical reaction in multiphase contactors: Part II: Numerical examples
Authors: Hatton T. A. , Lightfoot E. N. 
Published: June 2004

AbstractA Numerical study, based on the theoretical developments of Part I of this series, has demonstrated that the chemical activity of a solute can have a significant effect on the convective dispersion behavior of multiphase reactors, and that the dispersion parameters estimated using inert tracers for the individual phases may not be representative of the parameters that should be used in the design of reactive systems. Moreover, the use of different transverse averaging procedures for the individual phases can give rise to additional interaction effects between the phases which are not accounted for in the traditional axial dispersion models. The predicted differences in dispersion parameter values depending on whether the solute is inert or not, are in qualitative agreement with published experimental results.
Kinetics of short contact time coal liquefaction. Part I: Effect of operating variables
Authors: Abichandani J. S. , Wieland J. H. , Shah Y. T. , Cronauer D. C. 
Published: June 2004

AbstractThe liquefaction kinetics of Powhatan No.5 mine coal (Pittsburgh Seam) in the presence of SRC‐II recycle solvent at short contact times (<10 min) and temperature and pressure ranges of 573–723 K and 10.3–13.8 MPa is examined in a well‐mixed reactor. In the initial stages of liquefaction, while overall coal conversion (tetrahydrofuran solubles) increases with temperature, oil (pentane solubles) is lost with an increase in temperature. An increase in solvent‐to‐coal ratio results in an increase of conversion. The initial coal particle size distribution, total pressure, and nature of gas phase (nitrogen or hydrogen) have no significant effect on the production of any of the product of liquefaction for contact times up to 10 min. A lumped kinetic model is presented to describe the product distribution.
Fractionation with condensation and evaporation in wetted‐wall columns
Authors: Davis J. F. , Tung Hsien‐Hsin , Mah R. S. H. 
Published: June 2004

AbstractA model is presented to describe the behavior of falling film fractionators with evaporation or condensation. Experimental measurements of vapor composition, vapor temperature and wall temperature profiles were made. Close agreement suggests that the model is applicable to both adiabatic and nonadiabatic conditions.
Coiled configuration for flow inversion and its effect on residence time distribution
Authors: Saxena A. K. , Nigam K. D. P. 
Published: June 2004

AbstractFlatter velocity profiles and more uniform thermal environents are extremely desirous factors for improved performance in flow reactors and heat exchangers. One means of achieving this in laminar flow systems is to use mixers and flow inverters. These improve performance but at higher initial and operating costs. This paper introduces a new and more effective device for flow inversion which is achieved by changing the direction of centrifugal force in helically‐coiled tubes. Transient response experiments carried out under the conditions of both negligible and significant molecular diffusion reveal drastic narrowing of the residence time distribution (RTD). The effectiveness of the present device can be assessed by the fact that even at a Dean number of 3 the value of dispersion number as low as 0.0013 is obtained under the condition of significant diffusion, and in the case of negligible diffusion the value of dimensionless time at which the first element of tracer appears at the outlet is as high as 0.85.
Excess enthalpies for (water + methane) vapor up to 698.2 K and 12.6 MPa
Authors: Wormald C. J. , Colling C. N. 
Published: June 2004

AbstractA new flow mixing calorimeter has been used to make measurements of the excess enthalpy of water vapor + methane at temperatures up to 698.2 K and pressures up to 12.62 MPa. Tests on the calorimeter and consistency tests on the measurements suggest that the results are free from significant error. The measurements are fitted to an equation from which excess volumes and compressibility factors for the mixture are calculated.
Gas‐Liquid mass transfer in fixed‐bed reactors with cocurrent downflow operating in the pulsing flow regime
Authors: Blok J. R. , Koning C. E. , Drinkenburg A. A. H. 
Published: June 2004

AbstractLiquid‐side mass transfer coefficients were measured for cocurrent two‐phase downflow in 5 and 10 cm diameter columns pakced with 2.5 and 4 mm Raschig rings. Experiments were specifically carried out in the pulsing flow regime. The mass transfer coefficients were determined via absorption of CO2 into buffer solutions with the advantage of a high absorbing capacity. Thus columns of 1 m length could be used. Relations are proposed based on the hydrodynamic phenomena observed in pulsing flow. From these relations a correlation for kL is found in terms of flow rates and packing characteristics that satisfies the experimental data.
Low‐density polyethylene vessel reactors: Part I: Steady state and dynamic modelling
Authors: Marini Luigi , Georgakis Christos 
Published: June 2004

AbstractBy the use of a perfectly mixed model and an imperfectly mixed one for lowdensity polyethylene vessel reactors, we show that increases in the initiator consumption with polymerization temperature are due to mixing limitations at the initiator feed. With all its parameters independently estimated, the imperfectly mixed model provides an excellent agreement with experimental data for several initiators, feed flow rates and polymerization pressures. In the temperature region of industrial interest for each type of initiator, the open‐loop reactor dynamics drastically change from open‐loop unstable, at low temperatures, to open‐loop stable at high polymerization temperatures.
Low‐density polyethylene vessel reactors: Part II: A novel controller
Authors: Marini Luigi , Georgakis Christos 
Published: June 2004

AbstractBy the use of an imperfectly mixed model developed for LDPE vessel reactors, we show that a linear controller cannot perform satisfactorily in the entire range of operating conditions of industrial interest. Based on the concept of reaction rate control, a novel controller is developed which provides satisfactory closed‐loop dynamics independent of steady‐state conditions. A nonlinear controller is shown to be more effective in avoiding reactor light‐off.
Finishing stages of PET synthesis: A comprehensive model
Authors: Ravindranath K. , Mashelkar R. A. 
Published: June 2004

AbstractA comprehensive mathematical model for the finishing stages of polyethylene terephthalate (PET) synthesis is developed. The model takes into account the variables which have significant influences on polymerization but have not been hitherto taken into account, e.g., changing interfacial concentration and the presence of side reactions. The model is applicable to industrial polymerizations, and the predictions agree well with the literature and with certain pilot‐plant and commercial data.
Droplet coalescence and breakage rates in a packed liquid extraction column
Authors: Hamilton J. A. , Pratt H. R. C. 
Published: June 2004

AbstractCoalescence rates for MIBK (methyl isobutyl ketone) droplets in water in a packed column have been measured directly using a novel colorimetric technique. Second‐order coalescence and first‐order breakage rate constants were derived from the results using a discrete population balance model and were correlated in terms of droplet diameter and dispersed‐phase holdup. It is shown that the rate constants can be used to predict the steady‐state droplet‐size distribution and coalescence rates. They were also used in a theoretical study of mass transfer for a typical polydisperse system, which showed that repeated droplet coalescence and breakage leads to some reduction in column height.
The VIM theory of molecular thermodynamics: Part I: Analytic equation of state of nonpolar fluids
Authors: Alem A. H. , Mansoori G. A. 
Published: June 2004

AbstractVariational inequality minimization (VIM) theory of statistical mechanics is used to derive analytic equations of state for nonpolar fluids. Pair‐ and tripletintermolecular potential energy functions are taken into account in the formulation of this equation of state. The VIM theory has made it possible to derive rather simple expressions for the thermodynamic properties of nonpolar fluids. Predictions of the thermodynamic properties of argon and methane in the liquid phase, in the vapor phase, and in the critical region by the VIM equation of state are shown to be in excellent agreement with the experimental data.
Hydrodynamics of fluidization in a semicircular bed with a jet
Authors: Ettehadieh Bozorg , Gidaspow Dimitri , Lyczkowski R. W. 
Published: June 2004

AbstractA hydrodynamic model of fluidization was developed that computes void fractions, pressure and solid and gas velocities in cylindrical fluidized beds. Cmputed time‐averaged gas velocity distributions of a jet compared well with Westinghouse experimental data without the use of any fitted parameters. The main empirical input was a drag correlation from the literature.
A dual mechanism for low‐stress hemolysis in laminar blood flow
Authors: Beissinger R. L. , Williams M. C. 
Published: June 2004

AbstractHuman blood is sheared in cone‐and‐plate and parallel‐plate rotational viscometers, the latter with variable plate spacings h. Plasma is analyzed for hemoglobin and LDH content before and after shearing to determine the extent of shear‐induced blood damage within the low‐stress regime (stress ⩽ 13 Pa). Geometrical variations in the test apparatus can be accommodated by correlating blood damage with the radially‐averaged shear rate. Data on expired blood are shown to imply that much of the damage arises in the bulk fluid, with a smaller contribution from surface effects. Models are proposed to explain these results, obtained over a shear rate range to 5,000 s−1; parallel‐plate platen separation is 0.25 < h < 1.00 mm, cone‐and‐plate angle is 0.5°, and both systems have platens 100 mm in diameter.
Coalescence time for a small drop or bubble at a fluid‐fluid interface
Authors: Chen Jing‐Den , Hahn Pil Soo , Slattery J. C. 
Published: June 2004

AbstractWhen a small drop or bubble is driven through a liquid phase to a fluid‐fluid interface, a thin liquid film which forms between them drains, until an instability forms and coalescence occurs. Lin and Slattery (1982b) developed a hydrodynamic theory for the first portion of this coalescence process: the drainage of the thin liquid film which occurs while it is sufficiently thick that the effects of London‐van der Waals forces and electrostatic forces can be ignored. Here we extend their theory to include the effects of the London‐van der Waals forces. To simplify the analysis, we follow the suggestion of Buevich and Lipkina (1975, 1978) in developing an expression for the rate of thinning at the rim or barrier ring of the draining film. A linear stability analysis permits us to determie the coalescence time or the elapsed time between the formation of a dimpled film and its rupture at the rim.For comparison, this same linear stability analysis is applied to the thinning equations developed by MacKay and Mason (1963) for the plane parallel disc model and by Hodgson and Woods (1969) for the cylindrical drop model.For all three models, our linear stability estimate for the coalescence time tc is in better agreement with the available experimental data than is the elapsed time t∞ between the formation of a dimpled film and its drainage to zero thickness at the rim in the absence of instabilities.
A rotating annular chromatograph for continuous separations
Authors: Begovich J. M. , Sisson W. G. 
Published: June 2004

AbstractPreparative, multicomponent liquid chromatographic separations have been achieved by using a slowly rotating annular sorbent bed with fixed multiple feed points and fixed product withdrawal locations. The cation exchange separation of copper, nickel, and two cobalt complexes has been extensively used to study the effects of rotation rate, eluent rate, bed loading, and column size on separation performance. Experimental results have been compared with three theoretical models: plate theory, an analytical solution which incorporates multicomponent Langmuir isotherms, and an extension of the analytical solution to include dispersion effects.
Influence of hydrodynamics on crystal growth and dissolution in a fluidized bed
Authors: Budz Jerzy , Karpinski P. H. , Nuruc Zbigniew 
Published: June 2004

AbstractMass transfer coefficients for the growth and the dissolution of potassium alum and sodium thiosulfate in a laboratory‐scale fluidized‐bed apparatus were determined and correlated in a form of the Frössling equation. The surface reaction rate for potassium alum was found to be dependent onthe crystal size.
Incomplete state feedback for time delay systems: Observer applications in multidelay compensation
Authors: Ogunnaike B. A. , Ray W. H. 
Published: June 2004

AbstractThis paper demonstrates how a recently developed observer for time delay systems may be used to estimate needed state variables for implementation of multivariable time delay compensation. The general results are illustrated by an example of a multireactor plant in which only one reactor concentration can be measured. The observer worked well in simulation for both multivarible PID control and multidelay compensated PID control and allowed both schemes to function with estimated state variables in the feedback loop.
Numerical methods of solution for continuous countercurrent processes in the nonsteady state part I: Model equations and development of numerical methods and algorithms
Authors: Tan K. S. , Spinner I. H. 
Published: June 2004

AbstractSimple, efficient and noniterative algorithms are developed for the calculation of the dynamics of continuous countercurrent processes described by hyperbolic differential equations. The algorithms are derived using the method of characteristics and are particularly useful for either general quadratic or hyperbolic isotherms such as the Langmuir isotherm. The use of characteristic coordinates for the numerical solution avoids accumulating errors that would arise from computations based on a rectangular grid of real time and space coordinates.The proposed methods can provide an efficient framework for extension to transport processes with general nonlinear rate expressions. The algorithms and methods initially derived for simple models can be extended to more complex systems such as countercurrent flow with accumulating stationary phases and response to distributed disturbances.The application of the algorithm and methods to a number of countercurrent mass and heat transfer processes will be illustrated in Part II, where the accuracy and efficiency of the proposed methods will also be demonstrated by comparison to available analytic solutions. An example demonstrating the extension of the method to a system with complex coupled boundary conditions will also be discussed.
Fluidized combustion of char and volatiles from coal
Authors: Turnbull Eion , Davidson J. F. 
Published: June 2004

AbstractThis paper reviews the literature about fluidized combustion of char and volatiles from coal. While the rate of combustion of particles bigger than about 2 mm is mainly limited by the rate of diffusion of oxygen, there is usually an effect of chemical rate. As particle diameter decreases, the influence of chemical rate increases. Char particles are porous and combustion occurs in pores near their exterior. Char reactivity can be modelled by an effective pore area for combustion.At high bed temperatures (>1,150 K), the rate of combustion of volatiles is limited by the rate of mixing of fuel and oxygen. At low bed temperatures (<1,000 K), combustion reactions are inhibited by the inert particles in the bed.
Desorption of carbon dioxide from supersaturated water in an agitated vessel
Authors: Hikita Haruo , Konishi Yasuhiro 
Published: June 2004

AbstractThe rates of desorption of carbon dioxide from supersaturated water solutions into pure carbon dioxide or nitrogen gas stream were measured at 15,25, and 35°C in a baffled agitated vessel with a flat gas‐liquid interface operated in a continuous manner. The volumetric liquid‐phase mass transfer coefficients for the bubbles generated in the agitated liquid and the enhancement factors of the volumetric liquid‐phase mass transfer coefficient for the free liquid surface due to the bubbling were calculated from the measured desorption rates and correlated as functions of the relative supersaturation of the solution and the liquid‐phase Reynolds number.
Fundamentals of gas‐liquid‐solid fluidization
Authors: Muroyama Katsuhiko , Fan Liang‐Shih 
Published: June 2004

AbstractThe successful design and operation of a gas‐liquid‐solid fluidized‐bed system depend on the ability to accurately predict the fundamental properties of the system, specifically, the hydrodynamics, the mixing of individual phases, and the heat and mass transfer properties. Identification of the flow regimes under which the system operates is crucial to an understanding of both the variations of these properties and overall system performance. This timely, comprehensive review describes in a systematic manner the status of fundamental gas‐liquid‐solid fluidization behavior. This review also discusses the areas in which current knowledge is deficient and further research is needed.
Intermediate storage in noncontinuous processes involving stages of parallel units
Authors: Karimi I. A. , Reklaitis G. V. 
Published: June 2004

AbstractA model is developed to study holdup in intermediate storage as a function of system parameters such as processing unit delay times. General results concerning the periodicity of the required storage volume, the allowable unit delay times, and the calculation of the volume are presented. Analytical expressions for the limiting volume are obtained for several special network configurations. A simple upper bound is derived for purposes of quick estimates of the limiting volume for the general case, and a gradient based algorithm is reported for obtaining the minimum volume schedule for general networks.
Reactor selectivity based on first‐order closures of the turbulent concentration equations
Authors: Brodkey R. S. , Lewalle Jacques 
Published: June 2004

AbstractToor's (1969) hypothesis is extended to the second‐order, series‐parallel reaction. A second closure relates the mixing for the second reaction to the first. The equations are solved for conversion and selectivity for a turbulent reactor configuration. The analysis is extended to incorporate concepts of residence time distribution, segregation, and maximum mixedness.
Particle collection in magnetically stabilized fluidized filters
Authors: Albert R. V. , Tien Chi 
Published: June 2004

AbstractA study was conducted on the use of magnetically stabilized fluidized (MSF) filters for removing fine particles from gases. The effect on filter performance of a number of variables was examined, including the applied field strength, gas velocities, and bed height. The dynamic behavior of MSF filters was found to be characterized by a decreasing collection efficiency with time as a result of significant particle re‐entrainment.
Influence of secondary flow on diffusion with reaction
Authors: Mashelkar R. A. , Venkatasubramanian C. V. 
Published: June 2004

AbstractCoiling of a tube produces a profound change in the internal flow patterns due to the generation of a centrifugally driven secondary flow. This change strongly influences the transport processes in a coiled tube. The present paper investigates the influence of such secondary flow on a process of convective diffusion with reaction. The findings have an important bearing on a better understanding of a coiled tube reactor.