bluuebunny/crossref_metadata_2025 huggingface dataset:
Explaining solubilization kinetics
Authors: Chan A. F. , Evans D. Fennell , Cussler E. L.
Published: June 2004

Solubilization rates of fatty acids in pure detergent solutions are controlled by mixed micelle desorption and diffusion. Solubilization rates in partially saturated detergent solutions also involve exchange of fatty acids between the solid and the solution. These conclusions depend on models like those used in gas‐solid catalysis and in tracer diffusion.
The effect of flow maldistribution on conversion in a catalytic packed‐bed reactor. Part I. Analysis
Authors: Choudhary Manoj , Szekely Julian , Weller Sol W.
Published: June 2004

Through the statement of the vectorial form of the Ergun equation, combined with a differential component balance, a formulation was developed describing the velocity fields and reactant concentration profiles in an isothermal packed‐bed reactor in which the gas flow is nonuniform. This flow maldistribution was caused by both the preferential flow near the wall, inherent in most systems, and by the deliberate arrangement of the solid packing in the bed. The numerical solution of the governing equations showed that a nonuniform flow field had a very strong effect in distorting the concentration isopleths, particularly at intermediate conversion levels.
Simulation of an electrochemical carbon dioxide concentrator
Authors: Abdel‐Salam Omar E. , Winnick Jack
Published: June 2004

The performance of an electrochemical device for the concentration of carbon dioxide from the atmosphere of a spacecraft cabin is analyzed. The removal rates as well as the concentration distributions of the different species are calculated for any set of operating conditions by a model which embodies the fundamental electrolyte properties and design parameters.
Enzymatic regeneration of ATP. I. Alternative routes
Authors: Langer Robert S. , Hamilton Bruce K. , Gardner Colin R. , Archer Michael C. , Colton Clark K.
Published: June 2004

Prospects for enzymatic synthesis processes on an industrial scale depend upon development of a practical process for ATP regeneration. The relative merits of various routes to ATP regeneration involving chemical synthesis, whole cells or organelles, or cell free enzymes are evaluated. The most promising route involves one or more enzyme incorporating the reaction catalyzed by acetate kinase for ADP phosphorylation.
Mass transfer and internal circulation in forming drops
Authors: Burkhart Lawrence , Weathers P. W. , Sharer P. C.
Published: June 2004

The presence of internal circulation in forming liquid drops has a significant effect on mass transfer rates. For the systems studied, no circulation was observed below a Reynolds number of 9.7. For Reynolds numbers between 9.7 and 34.4, transition from zero circulation to complete circulation during the entire drop formation period occurred. In studies on the rate of mass transfer from fixed volume drops with forced internal circulation, increases in mass transfer rates were found at Reynolds numbers which corresponded to those observed for the development of internal circulation patterns within the drop.
Periodic cycling of plate columns: Discrete residence time distribution
Authors: Furzer I. A. , Duffy G. J.
Published: June 2004

The discrete residence time distribution applies to systems under periodic control. A system consisting of a plate column has been modeled to allow the generation of the discrete residence time distribution. The parameters in the model have been evaluated by measurements of entrainment, holdup, and the step response of the column under direct computer control. A least‐squares minimization technique provided confirmation of the modeling procedures.
A comprehensive correlating equation for laminar, assisting, forced and free convection
Authors: Churchill Stuart W.
Published: June 2004

A correlating equation for assisting convection was developed by combining correlating equations for pure free and pure forced convection. These component equations are based on laminar boundary‐layer theory for an isothermal, vertical plate. Theoretical values for assisting convection indicate that the third root of the sum of the third powers gives the best representation, as contrasted with the choice and rationalization of the second or fourth power by prior investigators.

This expression was modified by the addition of a limiting value Nuo to obtain a better representation below the domain of boundary‐layer theory and was generalized for uniform heating and for spheres and horizontal cylinders by the appropriate choice of the characteristic length.
Mechanics of nonisothermal polymer melt spinning
Authors: Fisher Robert J. , Denn Morton M.
Published: June 2004

Spin line tension, diameter attenuation, and the onset of the draw resonance instability are determined for a viscoelastic polymer melt, taking into account the changes in physical properties resulting from cooling of the filament. The theory predicts the experimentally observed stabilization of very short and very long filaments.
Stirred‐tank mechanical power requirement and gas holdup in aerated aqueous phases
Authors: Hassan Ibrahim T. M. , Robinson Campbell W.
Published: June 2004

Gas holdup and the ratio of the turbulent regime mechanical power consumed in aerated compared to that in nonaerated aqueous phases were measured in two laboratory sized tanks. Standard six‐blade turbine (D/T = 1/3), six‐blade paddle (D/T = 1/3), and four‐blade paddle (D/T = 2/3) impellers were used over a wide range of impeller rotational speed and gas sparging rate. For all systems, the power ratio results were found to fit a semitheoretical correlation (derived from dimensional analysis) involving the impeller Weber number, the aeration number, and the ratio of dispersion and liquid densities. Empirical correlations for gas holdup in water, aqueous solutions of nonelectrolytes, and an aqueous electrolyte solution are given. The overall results lead to the conclusion that power ratio and gas holdup correlations are highly specific to a particular impeller type and are also dependent on the tank size and the liquid phase physicochemical properties.
Thermodynamics of the sulfur dioxide‐seawater system
Authors: Abdulsattar Abdul H. , Sridhar Srinivasan , Bromley Leroy A.
Published: June 2004

The solubility of sulfur dioxide in seawater in the range 10° to 25°C and 10−5 to 1 molal is predicted based on a simplified chemical model. Estimates are also given of the resulting pH and the attendant distribution of sulfur and carbon dioxide species. Sulfur dioxide is considerably more soluble in seawater or other naturally alkaline waters than in pure water.
Drop sizes in annular gas‐liquid flows
Authors: Tatterson David F. , Dallman John C. , Hanratty Thomas J.
Published: June 2004

The droplets that appear in annular gas‐liquid flows are formed by the eruption of wavelets from the surface of the wall layer. Ninety per cent of the volume of this dispersed liquid is carried by only about 10% of the drops. We find, as suggested by Wicks and Dukler, that the distribution of drop sizes can be characterized by an upper limit, log normal function with only one of the three parameters, the volume median diameter, a strong function of flow conditions. A method for predicting the average diameter is suggested which is consistent with a theoretical interpretation based on a Kelvin‐Helmholtz mechanism, whereby the destabilizing force is the pressure variation over the wavelets.
Diffusional boundary‐layer resistance for membranes with low porosity
Authors: Malone Dermot M. , Anderson John L.
Published: June 2004

Diffusional mass transfer across membranes with uniform but low pore densities was studied experimentally as a function of stirring rate and pore area fraction. The results were analyzed in terms of a stagnant film boundary‐layer model specially formulated for a heterogeneous membrane containing discrete pores. The overall membrane diffusional resistance is linearly related to the inverse of the pore area fraction of the membranes for a constant stirring rate. An equivalent boundary‐layer thickness can be defined which is independent of membrane properties but a unique function of stirrer speed. These experimental boundary‐layer thicknesses are greater by a factor of 3 than those predicted by a published Sherwood number correlation determined for homogeneous surfaces, but the stirring rate dependence is in excellent agreement with this same correlation.
Model of transient aerosol particle deposition in fibrous media with dendritic pattern
Authors: Payatakes Alkiviades C.
Published: June 2004

When a suspension of fine solid particles in a gaseous medium flows through a fibrous filter, particles deposit on the fibers forming chainlike agglomerates known as dendrites. This deposition pattern is responsible for the intrinsically transient behavior of the filter, leading to drastic increases of the filtration efficiency and of the pressure drop. Related phenomena are observed when aerosols flow through other types of porous media (for example, granular beds), or next to duct walls, around immersed objects, etc. A theoretical model of the particle dendrite growth was proposed recently by Payatakes and Tien. Here a revised and generalized version of that model is developed. The following major revisions are made: allowance is made for collisions with a particle in a given dendrite layer that lead to retension in the same layer, radial as well as angular contributions to deposition are considered, and the dendrite layer adjacent to the collector is allowed to contain more than one particle. These changes lead to a substantially more realistic theoretical model. Expressions for the transient behavior of a filter of differential thickness are obtained, based entirely on first principles. These, as it has been shown in a previous publication, can be used to predict the dynamic behavior of a macroscopic fibrous filter. The use and behavior of this model is demonstrated in the simple case of deposition by pure interception. The present treatment of deposition by pure interception is more rigorous than and supersedes that adopted in previous works.
Mass transfer at high Péclet numbers for creeping flow in a packed‐bed reactor
Authors: Fedkiw Peter , Newman John
Published: June 2004

An isotropic, homogeneous packed‐bed reactor is modeled as an array of sinusoidal periodically constricted tubes (PCT). The effective asymptotic bed‐Sherwood number has been calculated for mass transfer at large Péclet number with a constant wall concentration and creeping flow hydrodynamics. The bed friction factor has also been calculated. The results for these macroscopic bed quantities depend upon two ratios of the microscopic PCT period length, average radius, and sinusoidal amptitude.
Binary gas diffusion of methane‐nitrogen through porous solids
Authors: Chen Lillian Lung‐yu , Katz Donald L. , Tek M. Rasin
Published: June 2004

Diffusion rates of nitrogen and methane have been measured across ten porous solids at 35°C and 1 atm by a steady state flow method. The porous plugs used were cylindrical in shape, with diffusion occurring in the direction of the axis. Diffusion data were taken with porous cores either dry or saturated with liquids. Water and n‐heptane were used as saturating liquids.

The rather complex internal structure of porous solids were indirectly characterized through some auxiliary measurements. These included porosity, permeability, and electrical resistivity factor (yet another indirect measurement of tortuosity).

The effective diffusion coefficients were correlated for the gas phase diffusion as a function of porosity. The ratio of effective diffusion coefficient to the open space diffusion coefficient (De/Do) was correlated for dry cores using the properties approximately characterizing the pore structure.
Photoassisted heterogeneous catalysis with optical fibers: I. Isolated single fiber
Authors: Marinangeli Richard E. , Ollis David F.
Published: June 2004

Recently reported varieties of photoassisted heterogeneous catalysts are summarized. A cylindrical, light carrying, optical fiber coated with a catalyst layer is evaluated as a novel configuration for all such light assisted catalysis. Equations are obtained which describe the light intensity in the fiber and its surrounding catalyst layer. A dimensionless group of the form Φ = (4αcβcdL)/(df) [d = dc for dc < λ, d = 0(λ) for dc > λ] determines the relative influence of light loss by all absorption and scattering to light transported in the fiber length. An effectiveness factor ηI for heterogeneous photoassisted catalysis is determined for reactions which are first order in intensity and without mass transport limitations. Asymptotic forms of ηI are ηI = 1.0 (Φ ≪ 1.0) and ηI = Φ−1 (Φ ≫ 1.0).
Vertical distribution of dilute suspensions in turbulent pipe flow
Authors: Karabelas A. J.
Published: June 2004

Closed‐form expressions are presented for predicting vertical concentration distribution of the dispersed phase in the turbulent core of pipe and channel flow. Experimental data obtained with spherical particles, of mean diameter d50 comparable to the Kolmogorov microscale, are in good agreement with model predictions. The average value of dimensionless lateral particle diffusivity, ζ = ε/Ru*, determined from these data is approximately 0.25, that is, fairly close to previously reported measurements with much coarser particles.
An alternate to the Dengler and Addoms convection concept of forced convection boiling heat transfer
Authors: Mesler Russell B.
Published: June 2004

Current literature describes forced convecting, boiling heat transfer as primarily convective heat transfer. The original evidence for this concept, reported by Dengler and Addoms, was reexamined and found misinterpreted. Nucleate boiling data, instead, correlate with their data. Subsequent use of the concept in correlations and models now requires close scrutiny.
Influence of drag reducing additives on mixing and dispersing in agitated vessels
Authors: Quraishi A. Q. , Mashelkar R. A. , Ulbrecht J. J.
Published: June 2004

The influence of the addition of drag reducing polymers and fibers on two transport processes in mechanically agitated liquid systems is examined. The first one concerns the determination of mixing times, which were found to be insignificantly to moderately increased in the drag reducing systems. The second one concerns the determination of the critical RPM at which complete suspension of solid particles occurs. It was shown that this was unaffected in the drag reducing systems. The results of this work can be applied to fermentation processes, biological reactors with flocs, and metallurgical processes. The theoretical implications of this work are to be seen in the association of polymeric and fibrous drag reducing additives with different parts of the turbulent spectrum.
Crystal size distribution dynamics in a classified crystallizer: Part II. Simulated control of crystal size distribution
Authors: Beckman James R. , Randolph Alan D.
Published: June 2004

Control of sustained limit‐cycle instability in crystal size distribution (CSD) was simulated for a class II (high yield) crystallizer equipped with a fines destruction system and product classifier. Control was simulated by proportional control of nuclei density using fines destruction rate as the manipulated variable. The control constant necessary to eliminate instability was theoretically predicted and agreed with the constant found via simulation. Poorer control of CSD (inability to completely eliminate limit cycles) was predicted using slurry density and slurry withdrawal rate as the measured and manipulated variables, respectively. Development of techniques for fine crystal population measurements to estimate nuclei density are necessary for implementation of the former control scheme. The suggested nuclei density control scheme is effective both in minimizing CSD transients and for elimination of instability.
Predicting the combustion rate of pulverized fuel from its initial size distribution
Authors: Leesley M. E.
Published: June 2004

It is assumed that for pulverized fuel, the weight fraction W with a size larger than x can be expressed as W = exp(−bxn). This paper describes the theoretical development and experimental evaluation using pulverized anthracite burning at 30 lb/hr of a method of predicting the combustion rate of a pulverized fuel from the constants b and n in the above equation.
Absorption of sulfur dioxide into aqueous sodium hydroxide and sodium sulfite solutions
Authors: Hikita Haruo , Asai Satoru , Tsuji Tadashi
Published: June 2004

The rates of absorption of pure sulfur dioxide into aqueous sodium bisulfite, sodium hydroxide, and sodium sulfite solutions with and without a surface active agent were measured at 25°C using a liquid jet column. For the sulfur dioxide‐sodium hydroxide system, the rate of absorption into the solution without surface active agent was higher than that into the solution with surface active agent, indicating the existence of the interfacial turbulence. The absorption rates obtained for the present system under the conditions of no interfacial turbulence were in good agreement with the theoretical predictions based on the penetration theory.
The permeation of gases through hollow silicone rubber fibers: Effect of fiber elasticity on gas permeability
Authors: Stern S. A. , Onorato F. J. , Libove Charles
Published: June 2004

The permeation of oxygen, nitrogen, argon, and synthetic air through hollow silicon rubber fibers was studied between 0° and 40°C and at gauge pressures of up to 3.45 × 105 N/m2 (50 lb/in.2 abs). The study was conducted in a permeator module in which the hollow fibers were pressurized externally. Strain measurements with single fibers showed this mode of operation to be preferable to internal pressurization. The gas permeation rates were markedly affected by dimensional changes of the hollow fibers under external pressure. These changes were predicted satisfactorily by a modification of Varga's (1966) deformation analysis of thick‐walled elastic tubes. The extent of air separation achieved in the permeator was in agreement with that calculated from theoretical models. It is conjectured that the performance of such a permeator may be improved in certain cases if the fibers are under suitable initial tension.
Multiple steady states in an isothermal, integral reactor: The catalytic oxidation of carbon monoxide over platinum‐alumina
Authors: Hegedus L. Louis , Oh Se H. , Baron Kenneth
Published: June 2004

Stable isothermal multiplicities were observed during carbon monoxide oxidation in an integral reactor, filled with alumina supported platinum catalysts. The multiplicities were investigated in the conversion‐temperature, conversion‐inlet carbon monoxide concentration and conversion‐mass flow rate domains.

The region of multiplicities was found to widen significantly upon catalyst aging which enhanced the pellets' diffusive resistances.

Several intermediate stable steady states were found between the highest and lowest steady states, both experimentally and theoretically.

All the above phenomena could be well interpreted by the interactions of the kinetics of carbon monoxide oxidation with intrapellet diffusion resistances.
Vacuum‐spray stripping of sparingly soluble gases from aqueous solutions: Part II. Stripper design using jet impingement nozzles
Authors: Simpson Stuart G. , Lynn Scott
Published: June 2004

Experimental data on vacuum‐spray stripping of sparingly soluble gases from aqueous solution using hydraulic nozzles were presented in part I of this communication. Mass transfer was shown to occur primarily from the thin liquid sheet issuing from the nozzle tip in semiquantitative accordance with an analytical model based on laminar flow behavior.

Jet impingement hydraulic nozzles offer the advantages of simplicity and low operating cost in vacuum‐spray stripping. An empirical model for the turbulent flow regime has been developed to facilitate incorporating jet impingement nozzles into a vacuum stripper design. The results of an economic analysis comparing other types of industrial vacuum strippers with the proposed design of a jet impingement vacuum stripper show the latter process to compare very favorably in terms of estimated equipment size and cost and in expected operating cost.
Dispersed phase mass transfer during drop formation under jetting conditions
Authors: Skelland A. H. P. , Huang Y‐F
Published: June 2004

A recent design procedure for perforated plate extraction columns requires extension to include jetting conditions at each perforation. For this purpose, correlations are obtained for jet length, jet contraction, drop size, and mass transfer coefficients in disperse phase controlled liquid‐liquid systems. Experimental variables include nozzle size, flow velocity, and physical properties.
Elongational flow behavior of viscoelastic liquids: Part I. Modeling of bubble collapse
Authors: Pearson Glen , Middleman Stanley
Published: June 2004

A spherically collapsing gas bubble will create a uniaxial extension of the fluid surrounding it. This flow may be readily analyzed, and it is possible to relate observed experimental parameters such as the pressure inside the bubble and the bubble collapse rate to the predictions of viscoelastic constitutive relations. This study compares the predictions of the Newtonian fluid and a viscoelastic model to observed bubble collapse in three fluids: one Newtonian fluid and two viscoelastic polymer solutions. Good agreement between data and the model was observed for the Newtonian experiments. The viscoelastic solutions, however, yielded rates of collapse which were greater than the Newtonian predictions based on equal zero‐shear viscosity. Subsequent modeling with a modified corotational Maxwell fluid yielded good agreement with the data for the transient elongational response in the viscoelastic solutions.
Multivariable computer control of a butane hydrogenolysis reactor: Part II. Data collection, parameter estimation, and stochastic disturbance identification
Authors: Jutan Arthur , MacGregor J. F. , Wright J. D.
Published: June 2004

A state space model, developed for multivariable control studies on a pilot plant packed‐bed reactor for the hydrogenolysis of butane, is fitted to experimental temperature and concentration data collected under unsteady state conditions. The parameters estimated are the fundamental transport parameters of the packed‐bed reactor and a catalyst activity parameter. A discrete stochastic model for the process disturbances is also identified, and a principle component type of procedure is used to reduce its dimensionality and to gain insight into the nature of these distrubances.
Calculation of phase equilibria for ethylene/low‐density polyethylene mixtures
Authors: Harmony Stephen C. , Bonner David C. , Heichelheim Hubert R.
Published: June 2004

We have used recent ethylene/low‐density polyethylene gas sorption data to calculate phase equilibria for ethylene/polyethylene mixtures from 0 to 30.3 MN/m2 (0 to 300 atm), the pressure range normally used in the flash separation step in low‐density polyethylene manufacture. The computations show significant differences from results obtained by extrapolation of the results of a previous study to the relatively low pressure range considered here.
Mean temperature difference: A reappraisal
Authors: Gardner Karl , Taborek Jerry
Published: June 2004

The derivation of the mean temperature difference in heat exchangers is based on a number of assumptions or idealizations, the most important ones being that the heat transfer coefficient is constant throughout the exchanger; that the temperature of either fluid is constant over any cross section of its nominal path, that is, complete mixing, no stratification or bypassing; and that an additional assumption for shell and tube exchangers, which has not always been fully recognized, is that within one baffle crossing the shell fluid temperature change is small with respect to its overall change, (that is, number of baffles is large). In actual exchangers, any of the above assumptions are frequently subject to various degrees of invalidation. This paper examines the effects of deviating from the first two assumptions and presents a new solution to the third.
Effects of temperature on the crystallization of potassium nitrate by direct measurement of supersaturation
Authors: Helt James E. , Larson Maurice A.
Published: June 2004

A laboratory continuous mixed‐suspension, mixed‐product‐removal crystallizer was used to study the effects of temperature on the kinetics of crystallization of potassium nitrate. A differential refractometer was used to continuously monitor the supersaturation permitting the measurement of supersaturation levels of order 10−3Kg solute/Kg water. The nucleation rate exhibited an inverse relationship with temperature.
A solid/liquid separation process based on cross flow and electrofiltration
Authors: Henry Joseph D. , Lawler Lee F. , Kuo C. H. Alex
Published: June 2004

The cross flow/electrifiltration process combines migration of particles in the presence of electrical and shear fields to increase filtration rates. A mathematical model and the experimental data are presented for both a kaolin clay suspension and an oil in water chemically stabilized emulsion. When the filter is operated in a regime above the critical voltage, filtration rate‐electric field strength dependence becomes linear, and both electroosmosis in the filtration medium and electrophoresis in the liquid film are the controlling mechanisms of transport. Both experimental data and the mathematical model indicate that the fluid circulation rate tangential to the filtration media does not necessarily increase filtration rate depending on the regime of operation. The model is used in conjunction with the experimental data to separate the liquid film resistance adjacent to the filter cake which is determined by fluid shear and electric field from the cake and filter medium resistances which are influenced by electroosmosis.
Two‐phase downflow through catalyst beds: Part I. Flow maps
Authors: Talmor E.
Published: June 2004

Flow regimes for nonfoaming and foaming two‐phase downflow through catalyst beds are correlated in terms of the superficial volumetric gas‐to‐liquid ratio and a force ratio relating inertia plus gravity forces to viscous plus interphase forces. In the pulsing flow regime, the frequency of pulses leaving large (29.2 cm) and small (6.58 cm) diameter beds is correlated with the flow map coordinates.
Model of the constricted unit cell type for isotropic granular porous media
Authors: Payatakes A. C. , Neira Mariano A.
Published: June 2004

The constricted unit cell model for isotropic granular porous media developed by Payatakes, Tien, and Turian (1973) is extended here to take in account the random orientation of the flow channels. In the proposed model, each unit cell corresponds to a pore (cavern) and has two coaxial constricted inlet and outlet ports (throats). The unit cells have random dimensions and orientations, the distributions of which can be determined from simple experimental measurements. The flow through a unit cell is assumed to be identical to that through a segment of the corresponding periodically constricted tube. The model is applied to the case of creeping Newtonian flow. The solution to the flow problem is obtained by a collocation method. Permeabilities of typical packings are calculated without use of any adjustable parameters (such as tortuosities, etc.) and are found in excellent agreement with experimental values.
Aeration and mixing in deep tank fermentation systems
Authors: Jackson Melbourne L. , Shen Chia‐Cheuh
Published: June 2004

Oxygen transfer characteristics for three sizes of equipment, from 76 mm to 7.6 m in diameter and for liquid depths from 4 to 21 m, correlate well and permit scaling of fermentation systems in size. Simple orifice inlets for gas flow, uniformly distributed over a tank bottom, effect rapid mixing and permit very high oxygen demands to be met. Supersaturation provides dissolved gases for the flotation and solids separation as an inherent processing procedure. Nearly uniform bulk liquid composition and a linear decrease of gas phase composition with depth permit a proper, integrated value of the oxygen saturation driving force to be employed. Results provide the design basis for large scale aeration systems which offer potential savings in both capital and energy.
Mass transfer characterization of Donnan dialysis
Authors: Lake Michael A. , Melsheimer Stephen S.
Published: June 2004

Donnan dialysis is a relatively new ion exchange process using ion exchange membranes to permit continuous operation. Potential applications exist in many areas where traditional columnar ion exchange, requiring a regeneration cycle, is currently used. A mathematical model was developed. Mass transfer parameters for the model were determined from laboratory data and correlated with the system operating variables.
A generalized correlation for Henry's constants in nonpolar binary systems
Authors: Yorizane Masahiro , Miyano Yoshimori
Published: June 2004

A generalized correlation for Henry's constant is developed from a three‐parameter corresponding states theory for fluid mixtures. Two characteristic parameters are required in each binary system. These parameters are determined for thirty‐eight nonpolar binary systems containing quantum gases for solutes. The overall average deviation for calculated Henry's constants is relatively small, about ± 2.5%.
Critical points of mixtures: An analogy with pure fluids
Authors: Moldover Michael R. , Gallagher John S.
Published: June 2004

The thermodynamic properties of vapor‐liquid equilibrium (VLE) states near the critical locus of mixtures are correlated in very close analogy with the techniques used to correlate the properties of pure fluids near a critical point. The only mixture parameters used in the correlation are the values of pressure, volume, temperature, and mole fraction (PVTx) along the physical critical locus. We illustrate the power of the present approach by correlating the rather extensive PVTx data that exist near the critical loci of the binary mixtures: CO2C2H6, SF6C3H8, and C8H18C3H8. Nearly all the data within 10% of the critical temperature may be described within their accuracy despite the occurrence of critical azeotropy or large regions of retrograde condensation.
Liquid distribution in trickle‐bed reactors: Part I. Flow measurements
Authors: Herskowitz Mordechay , Smith J. M.
Published: June 2004

Radial liquid distribution was measured for concurrent downflow of air and water through beds packed with catalyst particles. The experimental results can be predicted by a theory involving two parameters, a spreading factorSand wall factorf. Criteria are presented for predicting operating conditions (particle size and shape and tube diameter) for which the equilibrium distribution will be uniform and packed‐bed depth required to attain equilibrium liquid distribution.
Dispersion measurement in clogged filter beds: A diagnostic study on the morphology of particle deposits
Authors: Pendse Hemant , Tien Chi , Rajagopalan R. , Turian R. M.
Published: June 2004

The use of tracer dispersion measurements in conjunction with associated pressure drop data, as an indirect diagnostic technique for the determination of particle deposit morphology in deep‐bed filters, was investigated. The dispersion measurements consisted of the injection of an electrolyte tracer pulse at the inlet and the monitoring of the tracer peak as it traveled down the bed, while the pressure drop data consisted of the axial pressure gradient histories as deposition took place. These data are interpreted using dispersion and pressure drop theories established on the basis of assumed models of deposit morphology. The validity of this technique was confirmed experimentally.
Inferential control of processes: Part I. Steady state analysis and design
Authors: Joseph Babu , Brosilow Coleman B.
Published: June 2004

Methods are presented for the design of a static estimator which infers unmeasurable product qualities from secondary measurements. The secondary measurements are selected so as to minimize the number of such measurements required to obtain an accurate estimate which is insensitive to modeling errors. Unlike previous work, the number of secondary measurements can be fewer than the number of unmeasured disturbances. If the statistics of the disturbances and/or measurement noise are available, this information can be incorporated into the design procedure to obtain an optimal static estimator.

The design procedure is illustrated by application to a simulated industrial debutanizer. Data for the simulation were supplied by the Marathon Oil Company. Deviations in bottoms product quality are compared for the current control policy (maintenance of a stage temperature at its set point) and the inferential control system with the column subjected to representative feed composition disturbances. Results show that inferential control based on four, five, or six tray temperature measurements improves the steady state control performance by as much as 400%.
Inferential control of processes: Part III. Construction of optimal and suboptimal dynamic estimators
Authors: Joseph Babu , Brosilow Coleman
Published: June 2004

Methods are presented for the construction of optimal and suboptimal estimators for inferential control systems. Optimal estimators are constructed with the aid of Kalman filtering techniques applied to linear systems driven by integrated white noise disturbances. The description of the disturbances as integrated white noise leads to optimal dynamic estimators which reduce to optimal static estimators for sustained disturbances. Suboptimal estimators are constructed by prespecifying the structure of the estimator and choosing estimator parameters so as to minimize the mean square error in estimation.

Optimal and suboptimal estimators are compared by using them in an inferential control system which attempts to control the product composition of a simulated multicomponent distillation column. There is little difference in performance between optimal and suboptimal estimators which use temperature and flow measurements to estimate product composition. However, the inferential control system using a simple suboptimal estimator is significantly superior to the policy of maintaining a selected tray temperature constant through a standard feedback control system. The inferential control system is also superior to composition feedback control systems where the measurement delay is greater than 5 min.
Particle turbulent diffusion in a dust laden round jet
Authors: Yuu Shinichi , Yasukouchi Naoto , Hirosawa Yasuo , Jotaki Tomosada
Published: June 2004

The turbulent diffusion mechanism of particles in a round air jet are studied both theoretically and experimentally, with particular attention to the relative velocity between particles and fluid, overshooting effect of particles, and the distributions of fluid properties in space. The results indicate that the particle diffusivity decreases with the increase of the particle inertia. In general, the turbulent diffusivity of particles in an air jet is smaller than that of fluid scalar quantities. The particle inertia and the fluid large eddies, which are expressed by the Stokes number and the integral scale, respectively, play an important role in the transport mechanism of particles.
A modal approach to dynamics of nonlinear processes
Authors: Fisher Robert J. , Denn Morton M.
Published: June 2004

Approximate process dynamics of certain nonlinear systems can be estimated by elementary quadratures using a modal approach. The transient response including quadratic nonlinearities is determined by the eigenvalues, eigenvectors, and adjoint eigenvectors of the linearized system equations. The only restriction is that the dominant eigenvalue of the linearized system must be widely separated from the next slowest mode. Several process models satisfy this requirement.

The method is illustrated by application to a fourth‐order model of a fluidized bed. The dynamical response is in agreement with numerical solutions to the complete model equations, including estimates of finite regions of stability.
Prediction of multicomponent ion exchange equilibria for the ternary system SO‐NO‐Cl from data of binary systems
Authors: Smith Robert P. , Woodburn Edward T.
Published: June 2004

A framework is developed which provides predictions of multicomponent ion exchange equilibria from binary data.

Experimental data are reported for the ion exchange equilibria of the binary systems SO42−‐Cl−, SO42−‐NO3−, and Cl−‐NO3− on a strong base anion exchange resin. These systems exhibit nonideal characteristics in both phases, and the experimental characterization has been based on the reaction equilibrium constants and correlations for the activity coefficients in both phases. The exchanger phase activity coefficients are obtained from the well known Wilson (1964) model

The predictions of the ternary system SO42−‐NO3−‐Cl− based solely on the binary data are consistent with the experimental data for this system.
A design oriented model of fines dissolving
Authors: Kraljevich Zlatica I. , Randolph Alan D.
Published: June 2004

Mass and population balances, together with nucleation kinetics of the potassium chloride system, were combined to present a design oriented model which describes the behavior of a fines destruction system (FDS) implemented in an MSMPR crystallizer. This model was tested in a well‐documented, bench scale, potassium chloride crystallizer and was found to be adequate to predict the effect of fines dissolving. Product size improvement was related to incremental cost incurred with an FDS.
Convective heat transfer in gas‐solid suspension flow through packed beds
Authors: Balakrishnan Arcot R. , Pei David C. T.
Published: June 2004

A correlation for the convective heat transfer between a bed of metallic oxides and a flowing gas‐solid suspension was obtained experimentally. Four industrially important commercial catalysts with different physical, thermal, and transport properties were used as the bed materials. A wide range of air flow rates and solids to gas loading ratios were used. The correlating parameters, to estimate the convective Nusselt number, were found to be the Reynolds number, the Archimedes number, the solids loading ratio, and the shape factor of the packing materials. Impressive increases in heat transfer rates were observed with increased solids loading.
Reliability of optimization procedures for obtaining global optimum
Authors: Wang Bi‐Chong , Luus Rein
Published: June 2004

The importance of the starting point, the size of initial search region, and the search region reduction rate is examined with respect to the reliability of different direct search optimization procedures in being able to furnish the global optimum for nonunimodal systems. Although, in general, the reliability of an optimization procedure is problem dependent, it is nevertheless clear that reliability cannot be increased simply by selecting larger search regions or by reducing the rate of contraction of the search region. A more efficient means of increasing reliability is to embody a pseudo one‐dimensional search in the optimization procedure to enable the search to leave a local optimum and proceed to a better optimum.
Internal boiling and superheating in vaporizing multicomponent droplets
Authors: Law C. K.
Published: June 2004

The vaporization and combustion of a miscible multicomponent droplet in a quiescent atmosphere is analyzed by assuming transient‐diffusive transport within the droplet, quasi steady diffusive‐convective transport in the gas phase, and ideal solution behavior for the mixture. Results on the vaporization of a binary droplet show that owing to the significant liquid phase diffusional resistance, the vaporization process approximately consists of an initial transient regime, an intermediate, diffusion limited, almost quasi steady regime, and a final volatility limited regime. It is further demonstrated that the entrapment of the volatile components within the rapidly heated droplet interior may lead to the initiation of either homogeneous or heterogeneous nucleation, which can result in the fragmentation of the parent droplet with the internal pressure buildup.
Synthesis of heat exchanger networks: I. Systematic generation of energy optimal networks
Authors: Linnhoff Bodo , Flower John R.
Published: June 2004

A thermodynamically orientated method is presented for the synthesis of heat exchanger networks. With this method, the problem is solved in two stages. In the first stage, preliminary networks are generated which give maximum heat recovery. In the second stage, the most satisfactory final networks are evolved using the preliminary networks as starting points. In this paper, emphasis is given to the synthesis of the preliminary networks. Two four‐stream examples are solved. In Part II, emphasis will be given to the synthesis of final networks.
On‐line gain identification of flow processes with application to adaptive pH control
Authors: Gupta Surendra R. , Coughanowr Donald R.
Published: June 2004

A simple and practical method is presented for the control of first‐order flow processes with time varying gain and a pure delay in the measurement of the control variable. It involves on‐line identification of the process gain and a subsequent adjustment of the controller parameter. The method is well suited for applications in the chemical process industries where high frequency fluctuations in the process gain are not generally expected. It is tested on a computer simulated process as well as experimentally by application to a continuous stirred‐tank neutralization process involving pH control, where buffer concentration in the feed varies with time. There is a potential for the application of this method to an industrial process such as wastewater treatment.
Flow of a falling film into a pool
Authors: Ruschak Kenneth J.
Published: June 2004

Complete interfacial profiles are generated for the gravity flow of a thin film into a stagnant pool. The profiles show standing waves and a rapid thinning of the film just above the static meniscus over the pool. Such effects are encountered, for example, at the bottom of wetted wall columns.
Vapor‐liquid equilibrium for salt containing systems: Correlation of binary solvent data and prediction of behavior in multicomponent solvents
Authors: Rousseau R. W. , Boone J. E.
Published: June 2004

When salts or electrolytes are encountered in the design of separation equipment, the effects of these electrolytes on the vapor‐liquid equilibrium behavior of nonelectrolytes are often neglected. This is the case because there has not been a method for the correlation of data for salt containing systems which can be used for varying salt and solvent compositions. Boone, Rousseau, and Schoenborn (1976) proposed a method for correlating data from binary solvent‐salt systems which are not restricted in this manner. This work proposes an extension that correlates phase equilibrium behavior using the Prausnitz UNIQUAC equation, which can be used for systems having regions of immiscibility. In addition, the model used for binary solvent systems is extended to multisolvent salt systems, and it is shown that vapor‐liquid equilibrium data for these systems can be predicted from data on binary solvent‐salt systems.
Underground coal gasification
Authors: Gregg D. W. , Edgar T. F.
Published: June 2004

Underground coal gasification (UCG) is a method whereby the mining and conversion of coal are accomplished in a single step. Many field tests of UCG have been operated worldwide since the 1930's with varying degrees of success; based on this experience (especially in the USSR and United States), a field design which is applicable to a wide range of geological conditions and coal properties has evolved. This review discusses the rationale of this design and provides a physicochemical interpretation for the operation of a UCG system. Pertinent field and laboratory results as well as formal mathematical models of an in situ gasifier are evaluated as part of the analysis.
The mechanisms of transfer of hydrophobic coated mineral matter particles from a hydrocarbon to an aqueous phase
Authors: Prudich Michael E. , Henry Joseph D.
Published: June 2004

A solid/liquid separation process based on the transfer of hydrophobic coated mineral particles from a hydrocarbon to an aqueous phase is described. This process could be used, for example, to remove mineral matter from coal derived liquids in order to meet fuel specifications. A model system which involves hydrophobic, asphaltic, coated mineral matter particles in a model liquid, xylene, was used in conjunction with the mechanistic studies. The mineral matter distribution coefficient to the aqueous phase decreases rather than increases with time in batch experiments. Five asymptotic models based on the fate of the surface active chemical at long time are investigated. Included were adsorption on the mineral matter particle, adsorption at the oil/water interface, distribution of the surfactant to the aqueous phase, complete detergency, and partial detergency. Experimental data on the influence of surfactant concentration, contact time, water/oil ratio, and shear are consistent only with the partial detergency model.
Shape of a vertical column of drops approaching an interface
Authors: Vohra D. K. , Hartland Stanley
Published: June 2004

In a close packed dispersion, a drop at the interface experiences forces from the drops above which affect its shape and rate of coalescence. The shape of a vertical column of two drops approaching either a horizontal plane or deformable fluid‐liquid interface is considered here. The surface of the upper drop is sessile and that of the lower drop is defined by the differential equations governing the shape of an annular meniscus with apex. These have been integrated on a digital computer and the areas of the draining films between the two drops and between the lower drop and the interface obtained. The forces pressing on the films may also be obtained when the drop volumes are known and hence the ratio of the coalescence times of the upper and lower draining films. For equisized drops, the results indicate that the lower drop always coalesces with the upper drop before it coalesces with the bulk interface. When the lower drop approaches a deformable interface, the areas of the draining films are almost identical with those associated with a single drop to which the same vertical force is applied through a horizontal surface. Solutions for this case are already available and hence provide an estimate of the areas of the draining films associated with the bottom drop in a vertical column containing several drops.
A new thermodynamic representation of binary electrolyte solutions nonideality in the whole range of concentrations
Authors: Cruz Jose‐Luis , Renon Henri
Published: June 2004

A system of equations based on the ionic atmosphere theory of Debye and Huckel, Born model contribution, and local compositions of the nonrandom two‐liquid (NRTL) model is developed to represent isothermal activity coefficients, in the whole range of concentrations, for solutions in an undissociated solvent of a partially or completely dissociated electrolyte.

The physical constants and the four adjustable parameters necessary to represent the osmotic coefficient, for fifteen strong aqueous electrolytic solutions, are given at 298.15°K and atmospheric pressure. Vapor‐liquid equilibrium, for the hydrochloric acid‐water system at 298.15°K, is represented for acid compositions ranging from infinite dilution to 18 M using a known dissociation constant and six parameters.