bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrodynamic effect of surfactants on gas‐liquid oxygen transfer
Authors: Lee Y. H. , Tsao G. T. , Wankat P. C.
Published: June 2004

An experimental investigation of the hydrodynamics at the surface region of the liquid reveals that the soluble surfactants (sodium lauryl sulfate, glucose oxidase, and bovine serum albumin) affect both the length and the velocity scales of liquid eddies approaching the surface, which results in a decrease in mass transfer.
Simultaneous measurement of interfacial area and mass transfer coefficient in three‐phase fluidized beds
Authors: Dhanuka Vinodkumar R. , Stepanek Josef B.
Published: June 2004

The technique of simultaneous measurement of the mass transfer coefficient and the interfacial area (Robinson and Wilke, 1974) was used to measure the volumetric liquid‐phase mass transfer coefficient \documentclass{article}\pagestyle{empty}\begin{document}$\left({k_L \underline a} \right)$\end{document}, the interfacial area \documentclass{article}\pagestyle{empty}\begin{document}$\left({\underline a} \right)$\end{document} and the true liquid‐phase mass transfer coefficient (kL) in three‐phase fluidized beds. The eddy‐cell model of Lamont and Scott (1970) was found to give a reasonable fit to the kL data, if the proportionality constant is modified. The \documentclass{article}\pagestyle{empty}\begin{document}$k_L \underline a$\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$\underline a$\end{document} data were correlated by empirical equations. Some information on bubble diameter was deduced from the interfacial area and holdup measurements.
Adsorption of binary and ternary hydrocarbon gas mixtures on activated carbon: Experimental determination and theoretical prediction of the ternary equilibrium data
Authors: Costa E. , Sotelo J. L. , Calleja G. , Marrón C.
Published: June 2004

Experimental binary and ternary equilibrium data for the adsorption of hydrocarbon mixtures of methane, ethane, ethylene, and propylene on activated carbon at 20°C are presented and discussed. Reproduction of binary adsorption equilibria and prediction of ternary adsorption equilibria exclusively with data of binary systems have been carried out using a real adsorbed solution theory, which requires the calculation of the activity coefficients for the components in the adsorbed phase.

Predicted equilibrium data are found to be in excellent agreement with experimental values using Wilson and UNIQUAC equations to calculate the activity coefficients. The real absorbed solution theory provides a much more accurate method for predicting multicomponent adsorption equilibria than the ideal adsorbed solution theory.
A branched pore kinetic model for activated carbon adsorption
Authors: Peel Russell G. , Benedek Andrew , Crowe Cameron M.
Published: June 2004

A branched pore kinetic model for aqueous phase activated carbon adsorption is presented in which the carbon particle is separated into rapidly and slowly diffusing regions. The model was developed to overcome problems arising from a single rate parameter analysis and is shown to describe experimental data well. In addition to very different rates of transport in the two regions, parameters estimated by regression analysis indicated differences in the adsorptive characteristics.
Measurement and application of limiting activity coefficients
Authors: Eckert C. A. , Newman B. A. , Nicolaides G. L. , Long T. C.
Published: June 2004

Infinite dilution activity coefficients (γ∞) in binary liquid mixtures are data of wide practical and theoretical applicability, but their extensive use has been hindered by the experimental limitations of classical vapor‐liquid equilibrium techniques. Two new experimental methods for accurate γ∞ determinations are presented. These techniques, both faster and more accurate than classical methods, are complementary, and their applicability to different types of binary systems is discussed.
Distribution equilibrium between a bulk phase and small pores
Authors: Glandt E. D.
Published: June 2004

The pore‐bulk distribution coefficient K for a solute species is calculated by modelling the solute molecules as hard spheres. K is expanded in a virial‐type series in powers of the bulk‐phase concentration. The leading term is the Henry's law constant. The next two coefficients are reported for three pore shapes.
Gas‐phase combustion in fluidized beds
Authors: Stubington J. F. , Davidson J. F.
Published: June 2004

Kerosine or propane was injected near the base of a small, air‐fluidized bed of sand at 940°C. The fraction of fuel burnt within the bed was determined from a heat balance, for various particle sizes, fluidizing velocities, and bed depths.

Assuming the initial formation of a train of fuel vapor bubbles, theoretical analysis indicated two stages of combustion: (1) rapid consumption of the oxygen initially between fuel vapor bubbles; (2) slow consumption of oxygen initially outside the fuel vapor region by radial diffusion of oxygen and fuel vapor, analogous to a diffusion flame.

Comparison of experiment with theory gave effective radial diffusion coefficients of the same order of magnitude as the molecular diffusion coefficient. It was inferred that combustion occurs largely by a diffusion flame within the bed, with diffusion through the particulate phase being the rate‐controlling step. This explains why fuel distribution is so important in attaining efficient combustion.
Effect of chemical modifiers on borax crystal growth, nucleation and habit
Authors: Randolph A. D. , Puri A. D.
Published: June 2004

The effects on the fine‐crystal CSD of various surface active and ionic additives were studied for the sodium tetraborate decahydrate (borax) system. The organic modifiers used were effective at the ppm level. Surface active agents inhibited nucleation rate, while ionic additives increased nucleation. A simultaneous reduction in both the linear‐crystal growth rate and the degree of polycrystalline growth was observed in both cases. These effects correlated with modifier concentration in the liquor, but not with modifier/solids ratio. Borax exhibits classical magma and RPM‐dependent secondary nucleation and the results were well‐correlated with a conventional power‐law kinetic model.
Drop size and continuous‐phase mass transfer in agitated vessels
Authors: Skelland A. H. P. , Lee Jai Moon
Published: June 2004

Continuous‐phase mass transfer coefficients and drop sizes in agitated vessels are correlated with operating variables and physical properties of liquid‐liquid systems. In formulating mass transfer coefficients, a realistic mechanism has been developed, involving periodically varying rates of surface renewal associated with droplet circulation through varying degrees of turbulence around the vessel. Relationships are obtained for optimized design and scale‐up.
Effect of external diffusion on deactivation rates
Authors: Krishnaswamy S. , Kittrell J. R.
Published: June 2004

Alteration in concentration‐independent catalyst decay rates due to the presence of finite external and internal mass transfer resistances is examined. Analytical expressions for external and overall time‐dependent catalytic effectiveness are developed. Analysis of diffusion‐limited catalyst deactivation in flow reactors is discussed.
Wrong‐way behavior of packed‐bed reactors: 1. The pseudo‐homogeneous model
Authors: Mehta P. S. , Sams W. N. , Luss D.
Published: June 2004

A sudden reduction in the feed temperature to a packed‐bed reactor leads to a transient temperature rise, which is referred to as the wrong‐way behavior. A pseudo‐homogeneous plug‐flow model is used to analyze the structure of this transient behavior. The key parameters which determine the magnitude of this response are the dimensionless adiabatic temperature rise, activation energy, heat transfer capacity, coolant temperature, magnitude of temperature drop and length of the reactor. A simple expression is derived for predicing the maximum transient temperature rise.
Heat and mass transfer in hygroscopic capillary extruded products
Authors: Fortes Mauri , Okos Martin R.
Published: June 2004

This work presents an analysis of heat and mass transfer of extruded corn meal. Isotherm, thermal conductivity, drying and center temperature data were experimentally obtained for the cylindrically extruded product.

Modeling of the drying process was made by incorporating the mechanistic and irreversible thermodynamics approaches for determining heat and mass transfer in capillary‐porous media. The proposed model shows that both liquid and vapor fluxes can be expressed in terms of the same driving‐forces, namely, temperature and equilibrium moisture content gradients. A search technique allowed for the evaluation of both liquid and vapor conductivities.
An experimental investigation of stability and multiplicity of steady states in a biological reactor
Authors: DiBiasio David , Lim H. C. , Weigand W. A.
Published: June 2004

The existence of multiple stable and unstable steady states in a continuous stirred tank biological reactor (CSTBR) was demonstrated experimentally for the first time. These experiments resulted in the determination of growth rate, yield and intermediate metabolite concentration data entirely from continuous culture. This information was used to qualitatively interpret the stability behavior in terms of the biochemistry and bioenergetics of substrate metabolism.
Aerosol formation in reacting gases: Theory and application to the anhydrous NH3‐HCL system
Authors: Dahlin R. S. , Su Ja‐An , Peters L. K.
Published: June 2004

Aerosol formation in reacting gases is treated in terms of the gas‐phase reaction, homogeneous nucleation of the reaction product, and particle growth by parallel mechanisms. In the absence of foreign nuclei, nucleation of the gas‐phase reaction product is described by classical homogeneous theory with a nonequilibrium correction factor included; particle growth by diffusion, surface reaction, and cluster scavenging are examined. The predicted contribution of the latter mechanism increases with increasing supersaturation ratio due to a shift in the distribution of cluster sizes in accordance with a Boltzmann‐type steady‐state distribution. Illustrative results predict a nucleation burst during which the formation of nucleating monomer by chemical reaction competes with the loss of monomer due to diffusion to the surface of the freshly formed particles. In addition, conditions under which cluster scavenging can dominate are shown.

The particle‐size spectra predicted using the theory are compared with experimentally measured size spectra of NH4Cl particles formed by the gas‐phase reaction of NH3 and HCl. The size spectra were measured using an electrical aerosol size analyzer and an optical counter at the outlet of a continuous flow reactor after residence times ranging from 2 to 50 seconds. Reactant concentrations of 2.1 × 10−5 to 4.1 × 10−4 mol/m3 (0.5 to 10 ppm) were studied at 23 to 26°C and near atmospheric pressure. The predicted size spectra showed good agreement with the experimental results. At reactant concentrations below 4.1 × 10−4 mol/m3, the predominant particle growth was apparently by diffusion of the monomer in the noncontinuum range. Based on analysis of other data, cluster scavenging became more significant at reactant concentrations greater than about 8 × 10−4 mol/m3, and coagulation was not significantly important. Furthermore, these studies implied a microscopic surface free energy for NH4Cl of approximately 0.051 N/m.
Effect of flow direction on conversion in isothermal radial flow fixed‐bed reactors
Authors: Balakotaiah Vemuri , Luss Dan
Published: June 2004

Singular perturbation solutions are used to derive criteria predicting the influence of change in flow direction on the conversion in an isothermal radial‐flow, fixed‐bed reactor. It is shown that when the reaction does not involve a change in the number of moles, the outward flow direction is the preferred one for any reaction with a convex rate expression. The inward flow direction is a better choice for any reaction with a concave rate expression. A more intricate behavior occurs for reactions involving a change in volume. Analytical approximations and numerical solutions indicate that the influence of flow direction on the conversion is rather small.
A framework for description of mechanical mixing of fluids
Authors: Ottino J. M. , Ranz W. E. , Macosko C. W.
Published: June 2004

Mechanical mixing of fluids interpreted as deformation of contact interfaces between materials or originally designated material surfaces, can be described by continuum mechanical arguments. The idea is developed at two levels.

Part I: Exact kinematical description of mixing of fluids with negligible interfacial tension.

Part II: Description of mixing of fluids with negligible interfacial tension in terms of intermaterial area density.

The approach provides a unified mathematical description of the mechanical mixing of fluids.
Solubilities of carbon dioxide, hydrogen sulfide and nitrogen mixtures in methanol
Authors: Rousseau R. W. , Matange J. N. , Ferrell J. K.
Published: June 2004

Previously published data for the six binary combinations that can be formed from CO2, H2S, N2 and methanol are used to obtain parameters of the four‐suffix Margules equation describing liquid solution behavior. The vapor phase is described by the Soave modification of the Redlich‐Kwong equation of state. Isothermal binary data are fit well by these equations. The effects of temperature on the Margules parameters are significant and, except for N2‐containing mixtures, the parameters were taken to be inversely proportional to absolute temperature.

Experimental data were obtained for multicomponent mixtures of CO2, H2S, N2 and methanol. Model predictions were tested against these data. Comparisons of predicted and measured values of bubble point pressure and equilibrium vapor compositions are satisfactory.
Connection between relative gain and control loop stability and design
Authors: McAvoy T. J.
Published: June 2004

The objective of this paper is to point out the relationship between the relative gain array (RGA) and control system stability and design. Rigorous stability limits are presented for a general 2 × 2 system for several cases involving both steady state and dynamic interactions. These stability limits explicity involve the RGA. Two specific examples of interaction in distillation models are also discussed.
Diffusion and reaction in a stagnant boundary layer about a carbon particle, part 7: Transient behavior and effect of water vapor
Authors: Sundaresan S. , Amundson Neal R.
Published: June 2004

The dynamics of carbon combustion is studied. It is shwon that the carbon particle will not ignite if the furnace temperature is below a certain critical value. In addition, carbon particles display thermal instabilities which can be delayed or eliminated by increasing the water vapor concentration and/or the furnance temperature.
Wall effects in laminar flow of fluids through packed beds
Authors: Cohen Yoram , Metzner A. B.
Published: June 2004

A model which accounts for the effect of a confining wall and the resulting voidage variations near it on the flow behavior in packed columns is proposed.

The model, which is restricted to columns randomly packed with spheres of uniform size, reasonably describes the pressure drop‐flow rate relationship for both linear and non‐Newtonian fluids. The mass flux distribution is also studied in order to provide an insight into processes in which the flow behavior near the wall may be important.
Long‐range predictive control
Authors: Martin G. D.
Published: June 2004

Two process computer control algorithms which are based on long‐range prediction are outlined. The methods are compared, similarities pointed out, and each is shown to become similar to dead‐beat control under certain circumstances.
Collection efficiency of cyclone separators
Authors: Dietz P. W.
Published: June 2004

Based on terLinden's (A. J. terLinden, “Investigations into Cyclone Dust Collectors,” IME Proc., 160, 233, 1949) experimental observations, a three‐region model is proposed for the fluid flow in a cyclone. Within each region, turbulence is assumed to promote mixing of the suspended particles. Incorporation of this mixing concept into the three‐region model allows an analytic expression for the collection efficiency of the cyclone to be developed.

The theoretical result is compared with data obtained in the high temperature, high pressure exhaust from a pressurized fluidized bed combustor.
Reaction regimes in coal oxidation
Authors: Karsner G. G. , Perlmutter D. D.
Published: June 2004

A series of seven coals were oxidized in a fixed bed reactor to determine the controlling reaction regimes during mild coal oxidation. The effects of coal porosity and particle size, reactor temperature, and oxygen partial pressure were evaluated. The results show that coal‐oxygen reactions are controlled by the rate of internal gaseous diffusion for most coals, and by the rate of chemical reaction for the most porous coal of the set tested. Particle size effects also suggest internal diffusional control. Determinations of cumulative oxygen deposition indicate that surface areas several orders of magnitude greater than the superficial surface can participate in oxidation reactions, putting in doubt the applicability of the model previously derived by Kam et al. (1976a) for external mass transfer control.
Coke deposition in the thermal cracking of ethane
Authors: Sundaram K. M. , Van Damme P. S. , Froment G. F.
Published: June 2004

A novel experimental setup allowed both the kinetics of the thermal cracking of ethane and of the coke formation to be studied over a temperature range extending from 750 to 870°C. The overall kinetics of ethane disappearance are in excellent agreement with previously reported pilot results. Coking rates are initially high but rapidly decrease to reach an asymptotic value. The initial product distribution also differs from the asymptotic product distribution. A kinetic model for the coking is derived from the experiments and used in conjunction with a set of conservation equations for the simulation of industrial ethane cracking. The predicted run length, thickness of the coke layer and evolution of the tubeskin temperatures are in agreement with industrial observations.
Simulation of particulate removal in gas‐solid fluidized beds
Authors: Peters M. H. , Fan Liang‐Shih , Sweeney T. L.
Published: June 2004

A mathematical model for simulating particulate removal in gas‐solid fluidized beds is developed based on bubble assemblage concepts and particulate collection mechanisms. The importance of fluidization mechanics on the overall fluidized bed filtration performance is emphasized in the present study. Model predictions of fluidized bed filtration efficiencies are shown to compare favorably to the experimental results of various investigations. Because of the general formulation of the proposed model, it is believed to be applicable in the design of fluidized bed filtration operations.
Thermodynamic properties of adsorbed mixtures of benzene and cyclohexane on graphitized carbon and activated charcoal at 30°C
Authors: Myers A. L. , Minka C. , Ou D. Y.
Published: June 2004

Experimental data at 30°C are reported for the adsorption of mixtures of benzene and cyclohexane on two types of carbon surface: graphitized carbon and activated charcoal. The properties of the adsorbed solution approach those of bulk liquid at vapor saturation for graphitized carbon, but not for activated charcoal. The mixtures adsorbed on graphitized carbon are nonideal, and the deviations from ideality increase with surface coverage. For activated charcoal, the adsorbed mixtures are nearly ideal at all coverages. Mixture behavior for both adsorbents can be predicted without using experimental data for the adsorbed mixtures.
Fluidized bed freeboard phenomena: Entrainment and elutriation
Authors: Wen C. Y. , Chen L. H.
Published: June 2004

A model describing the entrainment of solid particles in the freeboard region of a fluidized bed is proposed. Published experimental data have been used to correlate the entrainment rate near the bed surface and the elutriation rate above the bed. It has been shown that the column diameter can have an important influence on the amount of fines elutriated.
Thinning of a liquid film as a small drop or bubble approaches a solid plane
Authors: Lin C.‐Y. , Slattery J. C.
Published: June 2004

When a small drop or bubble approaches a solid surface, a thin liquid film forms between them, drains, until an instability forms and coalescence occurs. A hydrodynamic theory is developed for the first portion of this coalescence process: the drainage of the thin liquid film while it is still sufficiently thick that the effects of London‐van der Waals forces and electrostatic forces can be ignored. This theory describes the time rate of change of the film profile, given only the drop radius and the required physical properties. Predictions are compared with profiles measured by Platikanov (1964) for gas bubbles. It is concluded that, even with only a trace of surfactant present, the liquid‐gas interface may be nearly immobile (tangential components of velocity are zero) and the surface viscosities will have little effect upon the drainage rate.
Experimental determination of the light distribution in a photochemical reactor: Influence of the concentration of an absorbing substance on this profile
Authors: Tournier A. , Deglise X. , Andre J. C. , Niclause M.
Published: June 2004

Knowledge of the local distribution of the light energy, in a photochemical reactor in the presence of an absorbing substance which reacts at a rate of order different from one with respect to the adsorbed light intensity, is important in order to calculate the mean rate of reaction and the design of the reactor. Here we report a simple method for the determination of this profile as a function of the concentration of an absorbing substance and we compare the results obtained with the models of emission from the literature. A semi‐empirical model accounting for our experimental results is presented.
Modelling highly skewed chromatographic response curves
Authors: Gelbin D. , Wolff H.‐J. , Friedrich S.
Published: June 2004

A model is presented in which damaged pores are distributed throughout a network of undamaged pores within a spherical particle. The differential equations are solved according to the numerical procedure of Haynes, Jr. (1975). The model is intended to simulate more highly skewed chromatographic response curves than the two‐zone model recently proposed by Chou and Hegedus (1978).

Pulse chromatographic measurements in fresh NaMgA zeolites using i‐butane as a tracer which only enters the macropores yield response curves with relatively low skew, which are readily fitted by a system of equations accounting for diffusion in a monodisperse pore system. For hydrothermally treated zeolites effective diffusivities and Henry constants are considerably lower and the skew higher than in fresh samples.

Curve fitting with the model proposed below is quite satisfactory, and the characteristic parameters determined are approximately constant at the flowrates studied. Application of the model should not be restricted to hydrothermally treated zeolites, but may be extended to catalysts or adsorbents with macroporous structures damaged by other forms of ageing.
Cylindrical cell model for the hydrodynamics of particle assemblages at intermediate reynolds numbers
Authors: Tal (Thau) Reuven , Sirignano W. A.
Published: June 2004

The spherical cell model for transport in assemblages of spheres, which stems from the low Reynolds number hydrodynamics, has a serious physical limitation when extended to the range of intermediate Reynolds numbers. Spherical symmetry cannot persist around a sphere, given a definite direction of convection. The boundary conditions of the spherical cell model are inappropriate and a cubic cell model would best represent the system. However, in order to avoid undue mathematical difficulties peculiar to three‐dimensional problems, a cylindrical cell model is proposed.

A numerical solution of the Navier‐Stokes equations expressed in vorticity‐stream function variables has been performed in conjunction with the cylindrical cell model for various values of porosity and Reynolds number. A much better agreement of the drag coefficient with experimental results is obtained by the cylindrical cell model than by the spherical cell model.
Analysis of annular bed reactor for methanation of carbon monoxide
Authors: Davis M. E. , Yamanis John
Published: June 2004

A new reactor configuration, the annular bed reactor, is mathematically modeled to assess its capabilities as a CO methanation reactor. The results show that the reactor offers excellent temperature control characteristics and negligible pressure drop, and that it is a promising configuration for this as well as other reaction systems.
Dispersion by laminar flow
Authors: Powell R. L. , Mason S. G.
Published: June 2004

Dispersion was studied by subjecting clusters of spherical particles (20–400 μm) to laminar flow fields. The clusters were: cohesionless, consisting of particles suspended in the same liquid as the bulk medium and cohesive for which a different liquid was used to make the suspension. Both qualitative and quantitative results are presented.
Non‐isothermal channel flow of non‐Newtonian fluids with viscous heating
Authors: Dinh S. M. , Armstrong R. C.
Published: June 2004

Approximate analytical solutions of the local temperature variations, due to viscous heating, in channel flows of non‐Newtonian fluids with small Nahme‐Griffith numbers were obtained by the WKB‐J method. The results are general and easy to use so that extensive numerical computations are not required. Comparisons between the approximate analytical solution and complete numerical solution showed that the relative differences were very small.
Design parameters estimations for bubble column reactors
Authors: Shah Y. T. , Kelkar B. G. , Godbole S. P. , Deckwer W.‐D.
Published: June 2004

Gas‐liquid as well as gas‐liquid‐solid bubble column reactors are extensively used in the chemical industry. This review evaluates the present state of the art for the estimation of “nonadjustable” parameters in bubble column reactors. All the pertinent literature concerning these parameters is discussed and the discussion is followed by relevant recommendations for their predictions. Literature on the modified bubble columns has been incorporated. Finally, the inadeqacies of the data in some areas of practical importance have been pointed out and the recommendations for future work are outlined.
Concentration dependence of surface diffusion coefficient of propionic acid in activated carbon particles
Authors: Suzuki Motoyuki , Fujii Takao
Published: June 2004

A Wicke Kallenbach type steady state diffusion experiment was performed for varying concentrations of propionic acid solution through activated carbon pellets. Since surface diffusion is a dominant mechanism, concentration dependence of the surface diffusion coefficient is precisely determined from the change of diffusion flux with concentration. Strong dependence of surface diffusion coefficient on amount adsorbed is partially interpreted in terms of the change of heat of adsorption with surface coverage as determined from separate equilibrium runs.
The sedimentation of coal in model oils: The effect of the viscosity and composition of the oil
Authors: Adams‐Viola Mary , Botsaris G. D. , Glazman Yuli
Published: June 2004

The results of batch settling tests with various coal powders in model oils indicated that the viscosity and the aromatic/paraffinic nature of the oil influences the sedimentation and the aggregation rate of the particles. Oxidation of paraffin oil may result in the generation of surface active agents which retards the sedimentation of certain coals.
Heterogeneous catalytic reactors undergoing chemical deactivation. Part I: Deactivation kinetics and pellet effectiveness
Authors: Lee H. H. , Butt J. B.
Published: June 2004

A general expression for the time‐dependence of the activity of a catalyst pellet affected by both chemical deactivation and diffusion is developed. Specific results are given for both uniform and pore‐mouth poisoning, with parallel and series poisoning mechanisms. Comparisons show a satisfactory agreement between theoretical and experimental results. A pellet effectiveness representing the combined effect of deactivation and diffusion is also developed in a form suitable for direct inclusion in reactor conservation equations.
Heterogeneous catalytic reactors undergoing chemical deactivation. Part II. Design and analysis: Approach of reactor point effectiveness
Authors: Lee Hong H. , Butt John B.
Published: June 2004

A design method is presented that takes into account the effects of both diffusion and deactivation on hetergeneous catalytic reactors. Improvements that can be made by the method are demonstrated and an efficient methodology is developed by which the design problem as well as associated optimization problems can be solved in a routine manner. The approach is based on the reactor point effectiveness for global rate of reaction in terms of bulk fluid conditions. Some important features emerge from the examples presented.
A new method for on‐line controller tuning
Authors: Yuwana Minta , Seborg Dale E.
Published: June 2004

A new method for tuning controllers on‐line has been developed based on a single experimental test, a step change in controller set point. The set‐point response data and analytical formulae are used to calculate model parameters for a first‐order plus time delay transfer function. Controller settings can then be calculated using the model parameters and standard controller tuning relations. Simulation results demonstrate that the new method provides good initial values for PID controller settings despite gross modeling errors and unanticipated load disturbances that may occur during the experimental test.
Multiple‐phase equilibria in hydrates from methane, ethane, propane and water mixtures
Authors: Holder G. D. , Hand J. H.
Published: June 2004

Phase‐equilibrium conditions for multicomponent hydrocarbon‐water mixtures were experimentally determined, demonstrating that both structure I and structure II hydrates can form from a single mixture. Model parameters were optimized to allow prediction of the hydrate structure, and prediction of the pressure and temperature of hydrate formation for the experimental mixtures.
Dynamic contact angles
Authors: Gutoff E. B. , Kendrick C. E.
Published: June 2004

The dynamic contact angles of various liquids on a gelatin‐subbed polyester tape were investigated by plunging a tape into a pool of liquid, in the manner of Perry and of Burley and Kennedy. The effect of the upper fluid was studied by replacing the air normally present by immiscible oils. A fair correlation was found at the point of air entrainment, relating the capillary number, μV/σ, to a physical properties number, gμ4/ρσ3. A dimensional correlation, relating the air entrainment velocity to the viscosity to the −0.67 power, was even better. At various velocities, the dynamic contact angle (or the dynamic contact angle minus the static angle) could be related to the capillary number, the physical properties number, and to density and viscosity ratios. Again, the dimensional correlations were better than the dimensionless ones, perhaps caused by an omission of a significant dimensionless group due to our inability to choose a suitable characteristic length.

With any one system, the data could be expressed as θ = kN above some minimum velocity, or, covering all velocities, as (θ − θs) = kN. With air as the upper fluid, all the data at one angle lie within one decade, with capillary numbers at air entrainment in the range of 0.6–1.3.
Analysis of vertical pneumatic conveying of solids using multiphase flow models
Authors: Arastoopour Hamid , Lin Shaw‐Chan , Weil S. A.
Published: June 2004

The multiphase flow models were used to predict pressure drop and segregation of particles flowing in a vertical pipe. To compare calculations with data, it was necessary to assume an effective particle size based on a coefficient of restitution and on inlet void fractions. Different partifle size distributions with equal average particle size generate distinctly different pressure drops and segregations. Contribution of solid interaction force is very important in accounting for the segregation of the particles in a vertical pipe.

All models gave a reasonable prediction of the design parameters. The pressure drops predicted by the models agreed well with both high‐ and low‐pressure experiments.
Gas transport through polyethylene membranes
Authors: Soles Emma , Smith J. M. , Parrish W. R.
Published: June 2004

Transport rates were measured by monitoring the pressure decay between two reservoirs connected by a polyethylene membrane. The diffusion equation was integrated to obtain a relation between the pressure difference across the reservoirs and the time, with solubility, expressed by Henry's law constant H, and the diffusivity D as parameters. A procedure was developed whereby both H and D are evaluated from a single set of Δp vs. t measurements. For argon in low‐density polyethylene, H and D at 323 K were 35[kg·mo]/(m3 of gas)/[kg·mol/(m3 of polymer)] and 2.1 × 10−10 m2/s, respectively. For the high‐density sample these values were 38.7 and 1.11 × 10−10 at 298.1 K.
Analysis of batch, dispersed‐emulsion, separation systems
Authors: Kremesec V. J. , Slattery J. C.
Published: June 2004

An analysis of a batch, dispersed‐emulsion (liquid membrane), separation system results in simple models that describe the concentrations and masses of each phase as functions of time. Comparisons with a limited set of experimental data are offered. One of these models allows a set of pilot studies to be extended to performance predictions and comparative studies of different feed‐membrane‐solvent combinations, which could lead to an optimally designed separation process.
Statistical estimation of parameters in vapor‐liquid equilibrium
Authors: Patino‐Leal Hugo , Reilly P. M.
Published: June 2004

A new procedure for the estimation of parameters in two‐component vapor‐liquid equilibrium is presented. It allows for measurement errors in all variables and gives better fits than most other procedures because of the use of two relations between the variables rather than one as is commonly used. An approximate and an exact solution are described and the importance of using all thermodynamic and statistical information is illustrated for the Wilson and UNIQUAC models. New alternatives for analysis of residuals are also discussed.
Multiparameter corresponding‐states correlation of coal‐fluid thermodynamic properties
Authors: Brule M. R. , Lin C. T. , Lee L. L. , Starling K. E.
Published: June 2004

A multiparameter corresponding‐states correlation has been developed to describe fossil‐fluid thermodynamic properties needed to design fluid‐flow, heat‐exchange, and other unit operations in coal‐liquefaction plants. Three equation‐of‐state parameters, a molecular‐size/separation parameter, a molecular‐energy parameter, and a molecular‐orientation parameter are used to characterize nonpolar and slightly polar aromatic hydrocarbons. A conformal‐solution model is developed for predicting thermodynamic properties of coal‐derived mixtures.
Kinetics of thermal regeneration reaction of activated carbons used in waste water treatment
Authors: Hashimoto Kenji , Miura Kouichi , Watanabe Tsuneo
Published: June 2004

The kinetics of the thermal regeneration of activated carbons used in the waste water treatment was analyzed on the basis of a model that the regeneration reaction consists of a set of many first‐order reactions each of which has different activation energy and frequency factor. The frequency factors were correlated approximately by a function of the activation energy.

The difference in the activation energy was represented by a distribution curve which was obtained by analyzing the thermogravimetric curve (TG curve) measured under a constant heating rate. The weight loss during the regeneration reaction under complicated heating conditions was well predicted by use of the distribution curve determined by the proposed method. This method describing the kinetics of the thermal regeneration may be applied to the design of reactors regenerating spent carbons.
Numerical solution of liquid‐phase multicomponent adsorption in fixed beds
Authors: Mansour Awadh , Von Rosenberg D. U. , Sylvester N. D.
Published: June 2004

A generalized mathematical model is developed to describe the process of multicomponent adsorption on activated carbon in fixed beds. Numerical, finite difference, solutions for the adsorption of binary, and ternary organic mixtures are shown to satisfactorily match previously published experimental data.
Diffusivity of urea in concentrated, saturated and supersaturated solutions
Authors: Sorell L. S. , Myerson A. S.
Published: June 2004

A relatively simple and extremely versatile optical method of obtaining diffusion coefficient data known as Gouy interferometry was employed to measure diffusion coefficients in undersaturated and supersaturated aqueous urea solutions at 25°C. The use of laser light as a monochromatic light source in the interferometer greatly simplified the procedure for obtaining diffusivity data from the interferometer. A novel design of a real image camera was employed to record the interferometric data. Values obtained from the interferometric data for low concentration (0–4 molar) aqueous urea solutions were within ±5% of literature values.

The diffusion coefficient was found to decrease linearly with increasing concentration up to the saturation point of the aqueous urea solutions, and to decrease drastically with increasing concentration in the supersaturated region. This behavior is similar to that observed in liquid‐liquid systems near the consolute point (Cussler, 1980). It is speculated that this phenomenon is a result of molecular aggregation of the urea molecules in supersaturated aqueous solutions. Very little experimental data have previously been obtained in the supersaturated region due to crystallization problems. Supersaturated diffusion coefficient data are important in the study and design of crystallization processes.

The solid‐solute‐liquid solvent binary systems urea‐water and sucrose‐water were modeled as a saturated solution solute‐liquid solvent system in order to test various concentration dependent diffusion relationships. Two of these relationships, the Vignes and Leffler‐Cullinan equations, showed improved correlation with experimentally determined diffusivity data for aqueous urea and aqueous sucrose solutions at undersaturated conditions.
An experimental study of floc strength
Authors: Glasgow L. A. , Hsu Jyh Ping
Published: June 2004

Photographic observation of the disintegration of individual flocs upon interaction with a turbulent jet has been used to quantify the binding force of kaolin‐polymer and kaolin‐Fe+III aggregates. The data suggest that the strength per unit mass decreases with increasing floc size, thereby supporting the multiple‐level model for aggregation.
Complex transitional flows in concentric annuli
Authors: Hanks R. W. , Peterson J. M.
Published: June 2004

Detailed measurements of radial variations of turbulence intensity were made with a hot film anemometer in a concentric annulus of aspect ratio Ri/Ro = 0.0416 for a Reynolds number range 1,200 ⩽ Re ⩽ 3,000 using a Newtonian polyglycol water solution. Measurements were also made of excess entrance pressure gradients and the axial variation of pressure gradients.

Based on the results of these measurements, it is concluded that the proposition of Lea and Tadros (1931), Rothfus (1948) and others that a transitional flow regime develops with a zone of turbulence near the inner core surrounded by a zone of laminar flow near the outer wall is false. The two‐critical Reynolds number transitional regime proposed by Hanks and Bonner (1971) is verified to exist but their mathematical model for the interpretation of its cause is disproved. It is shown that at the lower critical Reynolds number predicted by Hanks and Bonner (1971) and by Hanks (1980) a transition does occur. It is conjectured that the new flow may be a type of complex laminar bifurcation flow described by Joseph (1976), although the present data do not permit a definite conclusion to be reached. This complex laminar flow in turn undergoes a transition to turbulent flow at a second critical Reynolds number, higher than the first, in qualitative accord with Hanks and Bonner's (1971) and Hanks' (1980) predictions, although the latter are not quantitatively correct because they are based on inadequate models of the transitional flow field.
Bed‐surface contact dynamics for horizontal tubes in fluidized beds
Authors: Chandran Ravi , Chen J. C.
Published: June 2004

The local contact characteristics between the bed emulsion and the tube surface for horizontal tubes immersed in fluidized beds were investigated experimentally. The measurements indicated that the contact dynamics change significantly with circumferential position, gas flow rate, particle size and system pressure. From the experimental data, quantitative information on the local fluidization behavior were generated for use in heat transfer models.
Measurement and prediction of dissociation pressures of isobutane and propane hydrates below the ice point
Authors: Holder G. D. , Godbole S. P.
Published: June 2004

A gravimetric technique has been developed for measuring three phase vaporice‐hydrate (VIH) equilibria. This technique has been used for measuring VIH dissociation pressures for propane and isobutane hydrates to temperatures as low as 241.4 K. Kihara parameters, based upon the experimental dissociation pressure data, have been obtained. Because the range of experimental three phase equilibrium data has been considerably extended, the parameters based on this data should be more useful in predicting hydrate dissociation pressures.
Effects of London‐van der Waals forces on the thinning of a dimpled liquid film as a small drop or bubble approaches a horizontal solid plane
Authors: Chen Jing‐Den , Slattery J. C.
Published: June 2004

When a small drop or bubble approaches a solid surface, a thin liquid film forms between them, drains, until an instability forms and coalescence occurs. Lin and Slattery (1982a) developed a hydrodynamic theory for the first portion of this coalescence process: the drainage of the thin liquid film while it is sufficiently thick that the effects of London‐van der Waals forces and electrostatic forces can be ignored. Here the effects of the London‐van der Waals forces are included. The resulting theory describes the evolution of the film profile, given only the bubble radius and the required physical properties. The inclusion of a positive disjoining pressure results in better descriptions of the film profiles measured by Platikanov (1964) for air bubbles pressed against glass plates. When the disjoining pressure is negative, an unstable draining film evolves and finally ruptures. Unfortunately, there are no experimental data with which to compare our predicted coalescence times.
Laminar tube flow with a thermosetting polymerization
Authors: Castro J. M. , Lipshitz S. D. , Macosko C. W.
Published: June 2004

Two models describing the laminar flow of a polymerizing liquid through a tube have been developed and tested experimentally. One model is a full finite difference solution of the balance equations. The other is an approximate analytical solution which assumes that flow ceases after viscosity increases about tenfold. The models are compared to two experimental cases: (1) the pressure rise needed to keep the flow rate through the tube constant and (2) the flow rate decrease when pressure at the tube entrance is held constant. The finite difference model is more accurate in the early stages of polymerization while the approximate analytical model is more accurate at long times. The models have application to runner flow in reaction injection molding, to nozzles in thermoset molding, to thermoset dispensing equipment and to continuous reactive polymer processes in general.
Trickle‐bed reactors: A review
Authors: Herskowitz Mordechay , Smith J. M.
Published: June 2004

Fixed‐bed, catalytic reactors in which gas and liquid phases flow concurrently downward, termed trickle beds, are becoming more widely used in chemical processing, particularly in the petrochemical industry. Shah (1979) has summarized the advantages of trickle‐bed reactors and mentioned some of the processes in which the reactors are used. Shah's monograph and earlier reviews (Satterfield, 1975; Goto et al., 1977; Hofmann, 1978; Gianetto et al., 1978) have discussed factors affecting reactor performance.

In the last few years additional experimental and theoretical studies that contribute to improved design and scaleup of trickle‐bed reactors have been published. The scope of this paper is to review critically these improvements. Progress in understanding local rates of reaction is considered first. Then recent developments in reactor design are analyzed.
Steady‐state mass transfer with homogeneous and heterogeneous reactions
Authors: Dang Vi‐Duong
Published: June 2004

A solution is obtained for convective diffusion with axial diffusion and homogeneous and heterogeous reactions in a tube. The results have been used successfully to examine the validity of a model with simplified inlet boundary condition and to establish the conditions for a one‐dimensional dispersion model.
Determination of multicomponent sorption equilibria using perturbation gas chromatography
Authors: Glover C. J. , Lau W. R.
Published: June 2004

Perturbation chromatography previously has been used experimentally as an efficient method for obtaining sorption equilibria for systems with up to two vapor phase components at finite concentration. The objective of this work was to obtain a theoretical result that could be used for experimental determinations of sorption of multiple interfering species at finite concentration. Results obtained are applicable for both non‐stoichiometric and stoichiometric situations for systems that may have flowing phase velocity and volume changes associated with interphase transport and also may have interactions among the sorbed components. The dependence of each effluent peak characteristic velocity upon all of the component equilibrium isotherms requires that the equilibria be considered as a whole by simultaneously fitting a set of composition grid perturbation response data to appropriate isotherm surface equations.
Effect of the product layer on the kinetics of the CO2‐lime reaction
Authors: Bhatia S. K. , Perlmutter D. D.
Published: June 2004

The kinetics of reaction between CO2 and lime is investigated in the range of 673 to 998 K with a view to examining the effects of product layer deposition and variations in the limestone calcination atmosphere. The reaction is initially rapid and chemically controlled and goes through a sudden transition to a much slower regime controlled by diffusion in the product CaCO3 layer. The magnitude of the estimated product layer diffusivity is in the range of 10−18 to 10−21 m2/s, the corresponding activation energy is 88.9 ± 3.7 kJ/mol below 688 K and 179.2 ± 7.0 kJ/mol above that temperature, suggestive of solid state diffusion. Plausible mechanisms are discussed.
Behavior of particles in a liquid‐solids fluidized bed
Authors: Yutani N. , Fan L. T. , Too J. R.
Published: June 2004

The mechanics of particle motion in a fluidized bed were studied by focusing on the microscopic behavior of the particles. The local displacements of nylon particles fluidized by liquid were measured by the micro‐capacitance method, and the resultant time series was analyzed by determining its auto‐correlation function and the corresponding power spectrum. This has given rise to a stochastic or statistical model of particle displacements in the fluidized bed. This model visualizes the particle motion in a fluidized bed to consist of the random movement, generating irregular signals, and the linear movement, generating wave‐like signals.