bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of three‐phase packed‐bed reactors
Authors: Goto Shigeo , Smith J. M.
Published: June 2004

Three‐phase reactors involving a solid catalyst are normally used for production of product or removal of impurity. Equations are presented for these two measures of reactor performance for a first‐order, reversible or irreversible reaction in an isothermal reactor. The results are presented in terms of dimensionless groups of the pertinent mass transfer, kinetic, and equilibrium (solubility) properties, and the gas and liquid flow rates. From the equations given, it is possible to predict the relative performance of concurrent (trickle bed) and countercurrent flow reactors and also the effect of mixing in the gas or liquid streams on performance.
Parametric studies in industrial distillation: Part II. Heuristic optimization
Authors: Tedder D. William , Rudd Dale F.
Published: June 2004

State optimization should not be ignored in the evaluation of distillation alternatives. However, heuristic rank order algorithms can greatly simplify the analysis. Optimal operating pressures correlate well with feed bubble points, and intertower economic interactions are often small.
Parametric studies in industrial distillation: Part III. Design methods and their evaluation
Authors: Tedder D. William , Rudd Dale F.
Published: June 2004

Distillation networks are described as sets of composition nodes which are used to estimate material and energy balances. Comparisons with equialent, equilibrium stage models indicate that these simplified design methods consistently result in small, but acceptable, overdesign, even when applied to complex, thermally coupled tower configurations.
A constitutive equation for a viscoelastic interface
Authors: Gardner J. W. , Addison J. V. , Schechter R. S.
Published: June 2004

A constitutive equation has been developed to relate surface stresses to the deformational history of an interface. This equation is designed to provide a unified description of complex interfacial rheological phenomena. New and as yet unreported behavior such as surface normal stresses and viscoelastic contributions to the dynamic surface tension are predicted.

A monolayer of poly(vinyl alcohol) adsorbed at an air/water interface has been studied using a deep channel surface rheometer and the observed viscoelastic behavior shown to be fitted by the model.
Squeezing flows of polymeric liquids
Authors: Grimm Roger J.
Published: June 2004

An experimental study has been done on the flow of viscoelastic liquids squeezed between two flat parallel plates. In fast squeezes under a constant load, the plates did not come together as rapidly as predicted by inelastic fluid theory. Our experimental data suggest that this device is not generally useful as a viscometer.
Liquid distribution in trickle‐bed reactors: Part II. Tracer studies
Authors: Herskowitz Mordechay , Smith J. M.
Published: June 2004

An aqueous solution of potassium chloride tracer was introduced at a central location in the water feed to a trickle bed, and the tracer concentration was measured at various radial positions and bed depths. From the model and parameters of liquid distribution proposed in Part I, tracer concentrations can also be predicted. The predicted and experimental concentrations usually agreed within a few percent, providing an independent evaluation of the flow distribution model.
Measurement of structured microbial population dynamics by flow microfluorometry
Authors: Bailey James E. , Fazel‐Madjlessi Jila , McQuitty Donald N. , Lee L. Y. , Oro James A.
Published: June 2004

Commercial microbiological processes frequently contain dispersed microorganisms which are heterogeneous in their age, size, and composition. Relative protein and nucleic acid contents of individual bacteria in Bacillus subtilis submerged cultures have been measured experimentally using laser flow microfluorometry. Marginal and joint population composition density data and their complex patterns of evolution during batch growth provide an impetus and emerging basis for a new generation of potentially robust mathematical models of microbial systems.
Vapor‐liquid equilibrium measurements for the propane‐ethanol system at elevated pressures
Authors: Gomez‐Nieto Mateo , Thodos George
Published: June 2004

Vapor‐liquid equilibrium measurements have been carried out for the propane‐ethanol system at 325°, 350°, 375°, 400°, and 425°K. The pressures corresponding to these temperatures ranged from 569.5 kPa (82.6 lb/in.2abs) to 5 618.5 kPa (814.9 lb/in.2abs). Altogether, nineteen experimental determinations were made; one of these determinations at 425°K approached the critical state, and this measurement assisted in establishing the entire critical temperature and critical pressure profiles for this binary system. The information associated with these measurements enabled the construction of isothermal bubble point‐dew point relationships up to 500°K. These results made possible the establishment of isothermal relationships of K values vs. pressure for the components of the propane‐ethanol system. Calculated K values for this system using the BWR method and the SRK method were found to be in fair agreement with corresponding experimental values.
Countercurrent backmixing model for slugging fluidized‐bed reactors
Authors: Raghuraman Janakiraman , Potter O. E.
Published: June 2004

A model is developed for slugging fluidized bed catalytic reaction which improves on the model of Hovmand and Davidson by incorporating the solids mixing. The model parallels the countercurrent backmixing model of Fryer and Potter. Solids mixing is accounted for by the model of Thiel and Potter which assumes the rising slug is followed by a well‐mixed wake into and out of which solids flow at a rate determined by the rise velocity of the slug. Comparison is made with experimental data reported by Hovmand and Davidson with good results.
Liquid‐solid mass transfer in packed beds with downward concurrent gas‐liquid flow
Authors: Satterfield Charles N. , Van Eek Michael W. , Bliss Gary S.
Published: June 2004

Mass transfer coefficients were determined by measuring the rate of solution of cylindrical 3 or 6 mm benzoic acid tablets into water in the presence of flowing nitrogen, helium, or argon. Gas flow rates varied from 0 to 1.6 kg/(m2·s) and liquid flow rates from 0.5 to 25 kg/(m2·s), resulting in hydrodynamic flow patterns varying from trickle to turbulent pulse types of flow. In the pulse regime, the mass transfer coefficient was markedly affected by gas flow rate but did not depend on gas density explicitly if correlated in terms of an energy dissipation function.
Hydrodynamics of drop formation from a hydrocarbon film around a sphere placed in a moving aqueous phase
Authors: Calteau Jean P. , Aurelle Yves , Roques Henri L.
Published: June 2004

The study of the coalescence of secondary dispersions passing through a granular packing has led to the consideration of drop formation from a hydrocarbon film around a single sphere placed in the flux of an aqueous phase. An analogue mock‐up study led to a mathematical model for relating the diameter of the drop to various parameters participating in the phenomenon. A relationship enabling reasonably accurate calculation of the diameter of a drop formed by means of such a sphere placed in a stationary or mobile aqueous phase for a wide range of Reynolds numbers and Bond numbers is proposed.
A sparse computation system for process design and simulation: Part I. Data structures and processing techniques
Authors: Lin T. D. , Mah R. S. H.
Published: June 2004

As an alternative to tearing, symbolic permutation may be used to facilitate data processing rather than dimensional reduction in equation solving, permitting a reduction in computing effort without introducing any deleterious effects on the numerical convergence. Data structures and processing techniques suitable for this purpose have been successfully devised and tested. A program incorporating these techniques has been implemented on a CDC 6400 computer and used to solve irreducible systems of up to 551 linear and nonlinear equations.
Part II. A performance evaluation based on the simulation of a natural gas liquefaction process
Authors: Mah R. S. H. , Lin T. D.
Published: June 2004

SPARSCODE was evaluated based on the simulation of natural gas liquefaction using multicomponent refrigerants. Results obtained on four cases containing 179 to 573 equations show a computing time reduction by a factor of 40 to 250 in equation solving and an overall reduction by a factor of 4 to 30 for the simulation.
A comprehensive experimental investigation of tubular entry flow of viscoelastic fluids. Part II. The velocity field in stable flow
Authors: Cable P. J. , Boger D. V.
Published: June 2004

Center‐line velocities and developing velocity profiles are presented for viscoelastic fluids flowing in a 2:1 and 4:1 abrupt entry contraction. Two flow regimes are clearly identified: a vortex growth regime and a divergent flow regime. Dramatic differences in the velocity field are observed and discussed for the two flow regimes. A kinematic model based on the velocity field data is proposed for vortex growth flow.
Optimum design of chemical plants with uncertain parameters
Authors: Grossmann I. E. , Sargent R. W. H.
Published: June 2004

A new strategy is proposed for the optimum design of chemical plants whose uncertain parameters are expressed as bounded variables. The design is such that the plant specifications will be met for any feasible values of the parameters while optimizing a weighted cost function which reflects the costs over the expected range of operation. The strategy is formulated as a nonlinear programme, and an efficient method of solution is derived for constraints which are monotonic with the parameters, a case which arises frequently in practice. The designs of a pipeline with a pump, of a reactor‐separator system, and of a heat exchanger network, all with uncertain technical parameters, illustrate the effectiveness of the strategy for rational overdesign of a chemical plant.
Vapor‐liquid equilibrium: Part V. Data reduction by maximum likelihood
Authors: Van Ness H. C. , Pedersen Finn , Rasmussen Peter
Published: June 2004

A systematic study is presented of the objective functions applicable to the reduction of vapor‐liquid equilibrium data by regression procedures based on the principle of maximum likelihood. Numerical results are based on a set of artificial x‐y‐P data constructed so as to conform to the assumptions that underlie proper application of this principle.
An experimental study of the rheological behavior of surface films
Authors: Addison J. V. , Schechter R. S.
Published: June 2004

A constitutive equation has been developed to relate surface stresses to the deformational history of an interface. To verify the applicability of the equation to real surface films, experimental studies involving spread and adsorbed monolayers have been conducted using the deep‐channel surface rheometer operated both under the conditions of oscillatory and constant floor motion. The results reported here are the first obtained using an oscillatory system.

Experimental results indicate that both spread and adsorbed monolayers can exhibit viscoelastic behavior which may be represented by the model. Furthermore, it has been found that for three long chain, fatty acid films, spread on a pH 6.1 aqueous substrate, surface shear viscosity and surface elasticity increase with film pressure and molecular weight. The observed rheological behavior was found to be strongly pH dependent.
Optimal design of multistage adsorption‐bed systems
Authors: Sung Edmond , Han Chang Dae , Rhee Hyun‐Ku
Published: June 2004

The operation of two arrangements of multistage adsorption beds, parallel and series, was analyzed, and the optimal design problem of minimizing the capital and operating costs of the multistage adsorption bed systems was formulated. Solution of the optimization problem was obtained by using the Fibonacci search scheme. For the purpose of the study, data on the adsorption of liquid on activated carbon were taken from the literature for both single solute and multisolute adsorption systems and was used to derive the expressions for adsorption rate and the equilibrium relationship. Details of the performance of the optimally designed multistage adsorption bed systems are presented in terms of the physical and design parameters.
An analytical study of ultrafiltration in a hollow fiber artificial kidney
Authors: Papenfuss Heinz D. , Gross Joseph F. , Thorson Steven T.
Published: June 2004

A theoretical investigation of ultrafiltration through hollow fibers used in artificial kidney applications is presented. The hollow fibers are considered to be cylindrical tubes with ideally selective semipermeable walls which retain cellular particles (red and white cells, platelets) and plasma proteins in the blood perfusing the fibers. In contrast, water and species of low and medium molecular weight can freely permeate the membranes. The assumption is made that secondary flows avoid the formation of concentration boundary layers at the wall. Proper nondimensionalization of the equations for axial and radial transport results in the identification of parameters which are important in the characterization of the ultrafiltration through semipermeable tubes. Perturbation analyses for small values of these parameters lead to sets of differential equations which were solved analytically. These closed form solutions demonstrate the influence of hydraulic conductivity of the fiber walls, geometry, and axial and transmembrane pressure drop on the efficiency of hollow fiber artificial kidneys.
Solution of material balances for flow sheets modeled with elementary modules: The constrained case
Authors: Sood Mohinder K. , Reklaitis G. V.
Published: June 2004

Flow sheet material balance calculations are greatly simplified if all process input streams, reaction stoichiometry, and conversions, as well as all stream and component split fractions, are specified. Yet in many applications, especially those arising in process design, the available material balance specifications can take on many alternate forms. Each of these additional specifications can readily be expressed as a linear or nonlinear constraint equation involving species or total flow rates.

In this paper, an approach is developed for incorporating such specifications within the computational framework for solving unconstrained material balance problems. The linear as well as the nonlinear constraints are accommodated by generating a parametric solution to the underlying unconstrained problem. The parameters are determined by solving simultaneously first the linear and then the nonlinear constraint equations. Only as many equations are solved iteratively as there are nonlinear constraints.
Use of a finite‐stage transport concept for analyzing residence time distributions of continuous processes
Authors: Rogers Reed S. C. , Gardner Robin P.
Published: June 2004

This study is concerned with the derivation and application of the finite‐stage transport concept for modeling residence time distributions (RTD's) originally proposed by Adler and Hovorka (1961). This six‐parameter model is shown to be more versatile and accurate than the common two‐parameter tanks‐in‐series or axial dispersion models. Radioactive tracer results are given for a number of particulate unit processes with special emphasis on wet‐discharge ball mills.
Kinetics of step polymerization with unequal reactivities
Authors: Gandhi K. S. , Babu S. V.
Published: June 2004

The kinetics of step polymerization involving a monomer with unequal reactivities has been obtained. The polydisperity index (PDI) has also been calculated both as a function of conversion and the initial stoichiometric ratio. It has been shown that the usually assumed maximum value of 2 for PDI can lead to erroneous molecular weight.
The dynamic behavior of a CSTR: Some comparisons of theory and experiment
Authors: Schmitz R. A. , Bautz R. R. , Ray W. H. , Uppal A.
Published: June 2004

Mathematical methods employed recently in a theoretical study by Uppal et al. (1974) are applied to the second‐order homogeneous reaction between sodium thiosulfate and hydrogen peroxide and are combined with experimental investigations of that reaction using a nonadiabatic continuous stirred tank reactor (CSTR). A complete portrayal of the expected behavior of that reaction system is presented in parameter space. Some new experimental studies of reactor instabilities are presented and linked to that portrayal. Close agreement is shown between theoretical predictions and experimental data.
Rheological characteristics of solid‐liquid mixtures
Authors: Ackermann Norbert L. , Shen Hung Tao
Published: June 2004

The relationship between the shear stress and strain rate of a mixture consisting of solid particles suspended in a Newtonian fluid depends upon the physical properties of the mixture as well as kinematic features of the flow. Functional relationships for rheological properties of mixtures are derived and compared to measured results obtained by previous investigators.
The co‐current reactor heat exchanger: Part I. Theory
Authors: Degnan Thomas F. , Wei James
Published: June 2004

Mathematical development is presented for the theory of a reactor heat exchanger in which the heat generated in the reaction stream is simultaneously transferred to a co‐currently flowing coolant stream. The advantages of this scheme include isothermal conditions for the reaction stream, decreased parametric sensitivity, and improved stability.
Kinetics of fixed‐bed adsorption: A new solution
Authors: Liaw C. H. , Wang J. S. P. , Greenkorn R. A. , Chao K. C.
Published: June 2004

A new solution is obtained to the kinetics of a fixed‐bed adsorber in response to a step change in feed concentration for a linear equilibrium system with consideration for the resistance to mass transfer in both the mobile and stationary phases. The differential equations of continuity and mass transfer are integrated upon simulating the intraparticle concentrations with a parabola. The results agree with Rosen's rigorous but complex solution in the range of conditions of practical interest. The present solution is more convenient for computer application for the calculation of breakthrough curves.
A gas convection model of heat transfer in large particle fluidized beds
Authors: Adams Ronald L. , Welty James R.
Published: June 2004

A steady gas convection model of heat transfer to a horizontal cylinder immersed in a large particle gas fluidized bed has been developed. The model is based upon the hypothesis that the large particles will be isothermal and includes the effect of radiation as well as interstitial turbulence.

Results of calculations based on the model, for a two‐dimensional bubbling bed, indicate that a single bubble, having a diameter equal to the cylinder diameter, has a relatively small influence on the total heat transfer.
Simulation models for intraparticle deactivation: Scope and reliability
Authors: Downing D. M. , Lee J. W. , Butt J. B.
Published: June 2004

An experimental and modeling study of the dynamic behavior of an individual catalyst pellet as influenced by deactivation and dilution has been made. The reaction system employed was benzene hydrogenation over nickel/kieselguhr catalyst pellets diluted with 10% graphite, 10% silica, or undiluted; thiophene was employed as the catalyst poison.

A one‐dimensional effective transport model was developed, and the parameters for this model were determined principally from separate off line experiments or steady state experimental information. The adequacy of the model was determined from a direct comparison of the experimental and computed time‐temperature profiles.
Steady nonionic countergradient transport through membranes by coupled diffusion
Authors: Notter R. H. , Tam Y. M. , Min S.
Published: June 2004

Coupled diffusion generated countergradient transport through membranes is analyzed by experimental and theoretical means. Membrane wedge interferometer experiments on an ethanolwater‐cellophane membrane system show that net countergradient mass transfer of the less permeable component ethanol may be generated over a wide concentration range. A theoretical analysis of an idealized membrane separating two binary bulk solutions is developed to display further the major features of diffusional coupling effects, and good agreement between observed and predicted countergradient transport characteristics is shown.
A kinetic study of ozone‐phenol reaction in aqueous solutions
Authors: Li K. Y. , Kuo C. H. , Weeks J. L.
Published: June 2004

The present research concerns mechanism and rate of reaction between dissolved ozone and phenol in homogeneous solutions. The stopped‐flow technique was employed to obtain absorbances during reactions; the kinetic experiments were conducted at temperatures varying from 5° to 35°C in aqueous solutions with pH values ranging from 1.5 to 5.2.

The kinetic data indicated that the absorbance of a mixed solution increased rapidly in the very early portion of the reaction and then declined slowly in the remaining period. The rate of reaction in the early period was first order with respect to both phenol and ozone concentrations. The rate constant increased with pH value and temperature, and an activation energy of 5.74 K cal/mole was obtained. Further tests showed that the dissolved ozone was consumed completely in the first period and that in the second period the intermediate products were decomposed without depletion of ozone. Catechol, o‐quinone, hydroquinone, oxalic acid, humic acid, and a dimer were identified from mass spectra as products of the ozonization reaction.

A free radical mechanism, with initiation of an electrophilic reaction for the formation of catechyl radical, has been proposed to explain the experimental data for phenol‐ozone reaction in aqueous solutions. According to the proposed mechanism, the reaction path through the attachment to ortho position is much more favorable compared with that through the paraposition because of geometric advantage, though quinones and hydroxyphenol can be formed through parallel paths. The products of reaction detected in this research, therefore, are accountable by this mechanism. A rate equation derived on the basis of this mechanism also agrees well with that observed from the kinetic experiments.
Periodic cycling of plate columns: Mass transfer with nonideal liquid draining
Authors: Furzer I. A.
Published: June 2004

Mathematical modeling of a periodically cycled plate column has been completed by using a liquid bypass model to describe nonideal liquid draining. A numerical solution over a wide range of parameters provides a closed envelope of feasible solutions. A region of this envelope encloses favorable operating values of the parameters, while the other region is unfavorable. Measurements of the parameters for nonideal liquid draining in a 600 mm diameter column fitted with sieve plates lead to predictions of only small improvements in separation performance. Modifications to the column intervals are required to move the parameters into a more favorable position in the solution envelope.
Maintaining sparsity in process design calculations
Authors: Stadtherr Mark A.
Published: June 2004

Sparse linear systems in bordered block‐triangular form can be efficiently solved by block‐triangular splitting, a new technique that provides a drastic reduction in the fill‐in (loss of sparsity) that occurs in the direct solution of such systems. This technique is applicable in the iterative solution of the large systems of nonlinear equations that arise in the equation oriented approach to process simulation and design calculations.
Flow through tubes with sinusoidal axial variations in diameter
Authors: Deiber J. A. , Schowalter W. R.
Published: June 2004

An iteration technique has been developed to solve the equations of motion for flow of an incompressible Newtonian fluid through a circular tube with a radius which varies sinusoidally in the axial direction. The iteration is essentially geometric; one proceeds from a solution for flow through a tube in which the wavelength of diameter change in the axial direction is arbitrarily large to a solution for the wavelength and amplitude of interest. Theoretical predictions of inception of secondary flow are in good agreement with experiments.
Power consumption and gas capacity of self‐inducting turbo aerators
Authors: Zundelevich Yury
Published: June 2004

A theoretical and experimental analysis of self‐inducting turbo aerator performance was carried out based on the theory of water jet injector operation. It was shown that the aerator's injection coefficient is completely determined by only two dimensionless groups, CH and EuG, between which there is a single valued dependence on whose basis generalization of experimental data is possible. An analytical expression for the optimality criterion or aerator performance index, accounting for aerator gas capacity, power consumption, and submergence, has been obtained in terms of CH and EuG with only one adjustable parameter. From the above two dependencies, a methodology was developed for determining optimal operating conditions, by means of which all the data necessary for the optimal design can be obtained from the results of bench scale experiment.
On the kinetics of coal oxidation
Authors: Avison N. L. , Winters R. M. , Perlmutter D. D.
Published: June 2004

A series of seven coals of different ranks and from various locations were heated in air under relatively mild conditions to measure the rates of oxidation and the production of carbonic gases in the effluent stream. The gas flow rate, coal particle size, and reactor temperature were changed as independent variables. Each sample was exposed for from 6 to 9 hr under atmospheric pressure at temperatures in the range of 200° to 250°C. The results show two kinds of rate behavior depending primarily on the relative porosity of the coal under study. The small pore coals followed the expectations of the earlier Kam‐Hixson‐Perlmutter (KHP) model, but the large pore coals gave rates sensitive to transport effects. Correlations were also obtained on the ratio of carbon dioxide and carbon monoxide produced and on the relationship between the carbon content of an exposed coal and its heating value.
Criteria for selective path promotion in electrochemical reaction sequences
Authors: Sakellaropoulos George P.
Published: June 2004

An analysis of consecutive electrochemical reactions is presented with some emphasis on organic electrocatalytic sequences. The effect of potential and electrode kinetic parameters on reaction selectivity and on current and rate distribution is examined in two model electrochemical reactors with channel flow or with complete mixing. Results and some examples demonstrate that the electrolyte potential is the most significant parameter for selectivity control of complex series reactions in electrochemical processing or energy generation. Criteria developed for selectivity and current or rate variation provide the basis for the design of electrochemical reactors and for optimal operation considerations with multiple electrode reactions. Such criteria and analyses apply to a number of working electrode configurations operating with ionic as well as molecular reactants.
Water limitation in the C‐H‐O system over iron
Authors: Sacco Albert , Reid R. C.
Published: June 2004

Carbon dioxide and hydrogen will react over iron at 800° to 1 000°K and 1 bar pressure yielding water, carbon monoxide, methane, and carbon. In addition, iron oxides and carbides form during reaction. Phase diagrams are used to analyze this complex reaction system. Data are presented which suggest that the formation of magnetite (Fe3O4) or wustite (FexO) inhibits carbon formation. The water yield thus observed is limited by the time dependent iron‐iron oxide‐gas equilibrium. Preliminary data also suggest that the formation of carbides has little effect on water yield.
The growth of competing microbial populations in a CSTR with periodically varying inputs
Authors: Stephanopoulos Gregory , Frederickson A. G. , Aris Rutherford
Published: June 2004

The operation of a periodically forced chemostat (CSTR) in which two microbial populations compete for the same nutrient has been examined. Easily implemented criteria for the stability of the resulting cycles have been obtained, using the Floquet stability theory. After examining several possibilities it was found that stable periodic trajectories of coexistence can be achieved: (a) when the dilution rate of the chemostat is properly varied in a periodic manner between two values so chosen that the growth of one population is favored by the first and the growth of the other population is favored by the second, (b) when a certain percentage of biomass and growing medium is harvested periodically from the chemostat, and (c) when both the dilution rate and the concentration of the substrate in the feed are varied simultaneously and in a periodic manner.
An equation for predicting third virial coefficients of nonpolar gases
Authors: De Santis Roberto , Grande Biagio
Published: June 2004

An empirical correlation for calculating third virial coefficients of nonpolar gases is developed in agreement with the corresponding states theorem. This equation requires the use of a third parameter which can be estimated from molecular parameters. The method is reliable, even for systems where no experimental data are available. The extension to mixtures involves one interaction constant for all possible binary sets.
The dispersion of discrete particles in a turbulent fluid field
Authors: Calabrese Richard V. , Middleman Stanley
Published: June 2004

The degree of radial dispersion of medium size particles (ηK < dp < lf) emanating from a point source, is measured photographically in the turbulent core of a fully developed vertical pipe flow of water. From the classical theoretical results of G. Taylor, it was then possible to calculate statistical parameters which characterize the turbulent particle motion. A comparison is made between a tracer and neutrally dense, buoyant and heavy particles. Results indicate that the effect of particle intertia is negligible, and that the crossing trajectories effect dominates the dispersion process. A “wake effect” causes a buoyant particle to disperse to a greater degree than an equivalent heavy particle. An exponential‐cosine form of the Lagrangian autocorrelation coefficient provides a best fit for the dispersion data, although a purely exponential form is equally adequate for practical calculations.
A justification of the internal isothermal model for gas‐solid catalytic reactions
Authors: Pereira Carmo J. , Wang Jenshi B. , Varma Arvind
Published: June 2004

The commonly employed internal isothermal model for gas‐solid catalytic reactions, wherein the pellet is assumed internally isothermal but with internal concentration gradient, is justified by analyzing the full non‐isothermal diffusion‐reaction equations as an appropriate perturbation problem (β small, and Bih/β finite). The internal isothermal model is shown to be the zeroth order solution of the perturbation problem. Analytic expressions for the first order corrections are given for a first order reaction.
Heat transfer to a stationary sphere in a plasma flame
Authors: Sayegh N. N. , Gauvin W. H.
Published: June 2004

The overall heat transfer rates to stationary spheres of highly‐polished molybdenum (2 to 5.6 mm in diameter) in a confined argon plasma jet were experimentally measured. The effects of large temperature differences and large variations of the fluid property on the heat transfer process are investigated. The sphere Reynolds number range between 10 and 80, and the sphere temperature between 1,200 K and 2,400 K, with temperature differences between the gas and the sphere in excess of 2,000 K. These conditions are within the range commonly encountered in industrial plasma processing. The experimental values of the heat transfer coefficients are in reasonably good agreement with the predictions of a theoretical analysis of variable‐property flow and heat transfer previously reported by the authors.
Bead coating instability: A comparison of speed limit data with theory
Authors: Tallmadge John A. , Weinberger Charles B. , Faust Helen L.
Published: June 2004

Bead coating geometry is used in the continuous, high‐speed coating of photographic and other films. However, bead coating suffers from instabilities occurring at maximum and minimum speeds which result in non‐uniform films and unsatisfactory coating. This article describes an experimental study of these speeds for a range of flowrates, gaps, and viscosities. Results are compared with theory.
Entrance region (Lévêquelike) mass transfer coefficients in packed bed reactors
Authors: Fedkiw Peter , Newman John
Published: June 2004

Calculations for the high Peclet number, entrance region (Lévêquelike) packed bed, mass transfer coefficient using a sinusoidal periodically constricted tube model for the void structure of the bed are presented. An inverse cube root dependence of the mass transfer coefficient on the bed depth is predicted. This length dependence is anticipated only at very low Reynolds numbers. Calculations which assume a mixing region between successive periods are also presented. No bed length dependence is anticipated in these coefficients.
A new approach to optimization of chemical processes
Authors: Berna T. J. , Locke M. H. , Westerberg A. W.
Published: June 2004

Based on recent work by Powell, a new optimization algorithm is presented. It merges the Newton‐Raphson method and quadratic programming. A unique feature is that one does not converge the equality and tight inequality constraints for each step taken by the optimization algorithm. The article show how to perform the necessary calculations efficiently for very large problems which require the use of mass memory. Experience with the algorithm on small problems indicates it converges exceptionally quickly to the optimal answer, often in as few iterations (5 to 15) as are needed to perform a single simulation with no optimization using more conventional approaches.
The Co‐current reactor‐heta exchanger part II. Experimental results
Authors: Degnan Thomas F. , Wei James
Published: June 2004

A reactor of fiour crossflow nomolithic blocks is used to approximate a cocurrent and a countercurrent reactor‐heat excanger. Essentailly isothermal reaction pass profiles are produced by flowing the coolant and reactant streams cocurrent to each other according to the criteria set down in Part I of this paper. A multiplicy of steady states is shown to exist for the autothermal countercurrent mode, but not for the autothermal cocurrent mode, under identical conditions.
The influence of mixing on the antisolvent induced agglomeration and sedimentation of mineral matter in coal derived liquids
Authors: Vaidyanatan K. R. , Verhoff F. H. , Henry J. D.
Published: June 2004

There are several ways to remove minral matter from coal‐derived liquids: antisolvent agglomeration and subsequent sedimentation is one. Adding antisolvent to coal liquids causes asphaltenes and/or preasphaltenes in the oil to precipitate. The precipitated asphaltenes then agglomerate the paraticles, increasing the sedimentation rate. The magnitude of this increase depend no the mixing conditions used to dispers the antisolvent in the oil.

This article discuss the results of sedimentation experiments performed onthe antisolvent addition to coal liquids, using an x‐ray detection system. The system has the capacity of high temperature (up to 315°C) and high pressure (up to 2.75 7 × 106 Pa). The important parameters are the mixing time, the impeller speed, and the antisolvent addition rate. These are studied in detail for the antisolvent Soltrol.
Calculation of the governing equations for a seriated unequal velocity, equal temperature two‐phase continuum
Authors: Lyczkowski Robert W. , Solbrig Charles W.
Published: June 2004

The governing equations describing the flow of an unequal phase velocity, equal phase temperature (UVET) seriated two‐phase continuum as derived by Solbrig and Hughes (1978) are solved in this article, in one space dimension. A simple implicit iterative solution procedure is developed to numerically evaluate the five non‐linear coupled field equations. Analytical solutions are developed, against which the computer code results are compared. The prototype UVET code results are compared to the equivalent equal phase velocity, equal phase temperature (EVET) code results for the same problem. Major phenomena such as phase flow reversal, counter‐current flow and flooding‐like behavior are predicted.
Equilibrium staged parametric pumping: Part III. Open systems at steady‐state‐McCabe‐Thiele diagrams
Authors: Grevillot Georges
Published: June 2004

The theory of equilibrium staged parametric pumps with discrete fluid transfers has been presented in previous papers for total reflux. Here, it is extended to open, fractionating systems, operating in cyclic steady state. The cases of and enriching section, a stripping section, and a complete fractionating apparatus are successively considered. Providing adequate variables are defined, the result is a diagram which plays the same role as the McCabe‐Thiele diagram in distillation. The optimal feed stage location, the minimum reflux, and the separation factor for given operating conditions are determined analytically and graphically in the case of linear equilibrium isotherms. The method is then generalized to non‐linear equilibria, particularly of constant relative volatility type.
Thermodynamics of microemulsions: Combined effects of dispersion entropy of drops and bending energy of surfactant films
Authors: Miller C. A. , Neogi P.
Published: June 2004

A theory of dilute microemulsions is presented which includes for the first time both the entropy of dispersion of the drops and energy effects associated with bending the surfactant films at the drop interfaces. It yields expressions for drop size for (a) a dilute microemulsion in equilibrium with an excess bulk phase, e.g., an oil‐in‐water microemulsion in equilibrium with excess oil and (b) dilute oil‐continuous and water‐continuous microemulsions in equilibrium and containing equal amounts of surfactant. In the latter case, our theory indicates that existence of the two microemulsion phases sometimes is favored over a layered or lamellar phase, even though the “natural curvature” of the surfactant films is zero, corresponding to a perfectly flat film.
A Corresponding States equation for saturated liquid densities. II. Applications to the calculation of swelling factors of CO2—crude oil systems
Authors: Teja Amyn S. , Sandler Stanley I.
Published: June 2004

In an earlier article, a Corresponding States Method was presented for predicting the saturated liquid densities of both pure components and mixtures. The method is based on the known saturated liquid densities of two reference fluids and requires the critical properties and acentric factors of the pure components as input parameters. We use the method here to calculate the swelling factors of CO2‐crude oil mixtures using CO2 and n‐dodecane as the reference fluids. The critical properties and acentric factors of the crude oils were estimated from their API gravities and Watson K‐factors. Using only one adjustable coefficient to characterize each CO2‐crude oil system, swelling factors were calculated to within 0.5% of their experimental values. The single, adjustable coefficient is linearly related to the boiling point of the crude.
Gas‐adsorbate collisional effects and surface diffusion in porous materials
Authors: Thakur Subhash C. , Brown Lee F. , Haller Gary L.
Published: June 2004

If gas‐adsorbate momentum transfer is ignored, calculated surface fluxes within porous materials often can be grossly incorrect. Methods are introduced for including these interactions when calculating surface fluxes in permeability studies. Developments are carried out for systems with porous materials having both uniform and heterogeneous surfaces. These methods complement one developed earlier for Wicke‐Kallenbach experiments, using porous materials with uniform surfaces. Some previous studies are then considered. In one system, including gas‐adsorbate momentum transfer changes the proposed surface‐diffusion mechanism from a “hopping” phenomenon to the mobility inherent in a two‐dimensional gas. Consideration of other systems shows that, while very frequently these collisional interactions are important, experiments can occur where they are not. A criterion is developed for indicating when this momentum transfer is significant and its inclusion in surface‐flux determinations is necessary.
Observations on fixed‐bed dispersion models: The role of the interstitial fluid
Authors: Sundaresan S. , Amundson Neal R. , Aris Rutherford
Published: June 2004

Models of the role of the interstitial fluid for dispersion in a fixed bed for very high Reynolds numbers are examined in detail to determine how well they fit the physical requirements of finite speed of signal propagation, no backmixing, conservation and correct asymptotic form. It is concluded that no linear continuous partial differential equation of finite order can satisfy all of these requirements as well as the cell model, although all models for sufficiently large axial space and time variables are very good approximations to the cell model. Some new hyperbolic models are presented and their solutions obtained and compared with the standard solutions. In present day design it appears that no model has an outstanding advantage over any other.
Experimental and analytical study of wall reaction and transport effects in fast reaction systems
Authors: Smith Geoffrey K. , Krieger Barbara B. , Herzog Peter M.
Published: June 2004

This paper extends previous modeling calculations of concentration profiles and reaction rates in tubular flow reactors by including very fast wall reactions such as surface catalyzed atom recombinations. The plug flow assumption is investigated and found to be valid in tubular flow reactors when the dimensionless wall reaction rate is less than on (H < 1), and the dimensionless ratio of homogeneous reaction rate to diffusion rate (Damkohler number) is greater than one (α > 1). If these criteria are not met, this work provides a correlation yielding a correction factor which can be applied to the mean residence time. The method is applied to experimental data relating to the deactivation probability of two types of atoms on teflon and quartz. Values of 1.0 + 0.2 × 10−4 and 1.7 + 0.4 × 10−4 for the deactivation probabilities of 0 and N atoms, respectively, are reported.
Adsorption of methane and several mixtures of methane and carbon dioxide at elevated pressures and near ambient temperatures on 5A and 13X molecular sieves by tracer perturbation chromatography
Authors: Rolniak Paul D. , Kobayashi Riki
Published: June 2004

The principles of tracer perturbation chromatography were applied to measure the sorption of pure methane and several methane‐carbon dioxide mixtures on 5A and 13X molecular sieves at near ambient temperatures to pressures in excess of 7 MPa (1 000 lb/in.2abs). The molecular sieves studied were industrial grade zeolite crystals pelleted with 20 wt % clay binder.

The statistical mechanical model of Ruthven was applied to both pure methane and to several mixtures of methane rich, methane‐carbon dioxide mixtures from a few MPa (50 lb/in.2abs) to pressures as high as 10.34 MPa (1 500 lb/in.2abs) at near ambient temperature. While the theory appears to correlate the data well even at high pressures, some limitations of the theory begin to appear for the mixtures of higher dioxide concentrations.
Mass transfer in periodically cycled plate columns containing multiple sieve plates
Authors: Goss D. W. , Furzer I. A.
Published: June 2004

A five plate distillation column, 100 mm in diameter, has been used to study both fluid mixing and the mass transfer separations of mixtures of methylcyclohexane and n‐heptane under periodically cycled conditions. Both the fluid mixing and mass transfer could be successfully analyzed using the (2S) model to describe the liquid movement in the column. Previously reported results by McWhirter and Lloyd could not be reproduced. Only moderate improvements in separating ability can be obtained with sieve plates and packed sieve plate columns operated in the cycled mode.
Semiempirical theory of surface tension of binary systems
Authors: Carey B. S. , Scriven L. E. , Davis H. T.
Published: June 2004

Surface tensions of several binary mixtures are computed using the gradient theory of inhomogeneous fluids. The interfacial influence parameters are determined from mixing rules and pure fluid experimental tensions. A comparison of the compositional dependence of the predicted and experimental tensions indicates that the best results for nonpolar hydrocarbons are obtained from a geometric mixing rule for the influence parameter. Predicted tensions vs. composition for nonpolar systems are in excellent agreement with experiment, generally lying within 2% of observed data. Predictions are poor for alcohol solutions.
Multiplicity and stability of the hydrogen‐oxygen‐nitrogen flame: The influence of chemical pathways and kinetics on transitions between steady states
Authors: Heinemann Robert F. , Overholser Knowles A. , Reddien George W.
Published: June 2004

Numerical bifurcation techniques are used to predict multiple steady states for a nonadiabatic, premixed hydrogen flame stabilized on a flat‐flame burner. It is found that predicted conditions for burnout and ignition vary remarkably as rival chemical niodels are selected, while conditions for a well‐stabilized flame are much less sensitive to chemical and kinetic assumptions. It is concluded that multiplicity theory can help define the chemical behavior of realistic, complex reaction‐diffusion systems.
Simultaneous melting and freezing in the impingement region of a liquid jet
Authors: Epstein Michael , Swedish M. J. , Linehan J. H. , Lambert G. A. , Hauser G. M. , Stachyra L. J.
Published: June 2004

An experimental investigation of an impinging water jet freezing on a melting solid surface has been carried out. Attention was focused on the stagnation region of an axisymmetric jet. In the experiment, a water jet was directed upward against the lower end of a meltable rod, having a diameter about twice that of the jet orifice. Solid octane (m.p.—56.5°C) and solid mercury (m.p.—38.9°C) served as the meltable materials. A laminar‐axisymmetric flow model was developed to describe melting heat transfer in the presence of jet solidification within the impingement region. Measurements of the melting rate and conditions for the onset of jet solidification were found to agree quite well with the values predicted with this model.
The calculation of critical points
Authors: Heidemann Robert A. , Khalil Ahmed M.
Published: June 2004

Gibb's classical theory of critical points leads to two simultaneous, nonlinear equations in the intensive variables of the critical phase. In this paper is presented a new procedure for evaluating the functions which appear in these nonlinear equations. The new procedure simplifies and permits the speeding up of the computation of critical points in multicomponent mixtures.

Computations have been performed for critical points in binary and multicomponent mixtures described by the SRK equation. The methods developed will be equally applicable to other two‐constant equations of state. The equations to be solved are organized as two equations in the unknown critical temperature and specific volume for a mixture of known composition. One of the two equations, the determinant which establishes the stability limit for the mixture, is shown to be satisfied by more than one volume at a given temperature and by several temperatures at a given volume. A technique is proposed to assure that the correct temperature, volume solution can be found for this equation. For critical points in ordinary gas‐liquid systems, an overall computational procedure is suggested in which it proves to be unnecessary to provide initial guesses for either the temperature or the volume.

Application has also been made to several systems with high density (liquid‐liquid) critical points.