bluuebunny/crossref_metadata_2025 huggingface dataset:
Friction coefficients for bubbly two‐phase flow in horizontal pipes
Authors: Kopalinsky Eleonora M. , Bryant R. A. A.
Published: June 2004

Friction coefficients determined from an experimental study of the flow of bubbly two‐phase mixtures in horizontal pipes are used, together with a homogeneous theory, to establish a method for the prediction of the static pressure drop in this class of flows.
On the fate of fuel nitrogen during coal char combustion
Authors: Wendt J. O. L. , Schulze O. E.
Published: June 2004

The physical and chemical characteristics that influence the conversion of fuel nitrogen to nitrogen oxides during coal char combustion were theoretically examined by using a simplified model in which nitric oxide is an intermediate product between fuel nitrogen and N2.

It was found that diffusion‐reaction interactions were important in determining the selectivity of the char particle toward nitric oxide production. At low temperature fluidized bed combustion conditions, pore size is important, and low conversion of fuel nitrogen to nitric oxide is favored by long narrow pores. Under high temperature, pulverized coal combustion conditions, the model provided insight into mechanisms of nitric oxide formation and predicted the observed weak temperature dependence of fuel nitrogen conversion, as well as a significant effect of particle size.
Secondary nucleation of ice in sugar solutions and fruit juices
Authors: Stocking James H. , King C. Judson
Published: June 2004

From thermal response measurements, ice nucleation rates in distilled water, sugar solutions, and fruit juices were determined for a stirred, batch‐seeded crystallizer. High resolution thermometry permitted use of initial sub‐coolings between 0.01° and 0.2°K. Nucleation increased with approximately the second power of subcooling. Applications to freeze concentration are considered.
Multipass flow distribution and mass transfer efficiency for distillation plates
Authors: Bolles William L.
Published: June 2004

A new model for predicting the hydrodynamics, flow distribution, and mass transfer efficiency of multipass distillation trays is presented. Separate submodels apply to two‐, three‐, and four‐pass trays, which may be any type of cross flow tray with downcomers: sieve, valve, or bubble cap.

It was found that the liquid/vapor flow ratio in one pass of a poorly designed multipass tray can be several times that in adjacent passes, and that the mean tray efficiency of such a tray is substantially less than the optimum possible. It is shown that multipass trays can be designed with essentially perfect flow distribution and optimum (maximum) overall tray efficiency.
An interferometric technique for the study of steady state membrane transport
Authors: Min Sengwoo , Duda J. L. , Notter R. H. , Vrentas J. S.
Published: June 2004

A membrane wedge interferometer was designed for obtaining steady state mass transfer data on liquid‐membrane‐liquid systems. Procedures were developed for analyzing the diffusive transfer process, and experiments were conducted on the ethyl alcohol‐water‐cellophane membrane system to obtain the type of data needed for elucidating mechanisms of membrane transport. The proposed technique provides an accurate method of studying membrane transport without the troublesome complications which characterize other methods.
A mechanism supported by extensive experimental evidence to explain high heat fluxes observed during nucleate boiling
Authors: Mesler Russell
Published: June 2004

This paper attempts to elucidate the mechanism responsible for high heat transfer rates occurring in nucleate boiling when liquid films exist on the heating surface. High‐speed cinematography and simultaneous transient surface temperature measurements provide a basis for describing the mechanism. In a liquid film, bubbles grow and detach rapidly. The film is quickly renewed. A liquid microlayer exists beneath a bubble its entire life. Conditions are very favorable for rapid evaporation from the microlayer so that heat transfer is rapid. A number of independent observations by other investigators working on diverse problems are cited in support of the mechanism.
Constitutive equation for vapor drift velocity in two‐phase annular flow
Authors: Ishii Mamoru , Chawla T. C. , Zuber Novak
Published: June 2004

A constitutive equation for a vapor drift velocity which specifies the relative motion between phases in the drift flux model is developed for two‐phase annular flows. The constitutive equation is derived by taking into account the interfacial geometry, the body force field, and the interfacial momentum transfer, since these macroscopic effects govern the two‐phase diffusions. A comparison of the model with three sets of experimental data obtained over a wide range of flow parameters shows a satisfactory agreement.
Practical realizations in process modeling: Part II. The approximation problem
Authors: Jayaraman Krishnamurthy , Lapidus Leon
Published: June 2004

The composite algorithm derived in Part I is used to construct models from pulse responses of lumped and distributed systems, as well as an empirically measured residence time density. Along the way, salient points in the numerical implementation of the algorithm are indicated. In the present recursive procedure, the initial transient is predicted accurately by lower‐order partial realizations; successive partial realizations involve progressively longer tails of the pulse response. The zeroth moment of the impulse response is used to advantage when realizations with no zeros are appropriate.
Mathematical models of the monolith catalytic converter: Part I. Development of model and application of orthogonal collocation
Authors: Young Larry C. , Finlayson Bruce A.
Published: June 2004

The orthogonal collocation method is applied to solve the mathematical model of a monolith catalytic converter, in which the reaction takes place in a porous catalytic layer deposited on the wall of a tube. A sequence of models is developed, with the most complicated one involving transient heat and mass transfer in three dimensions.
Mathematical models of the monolith catalytic converter: Part II. Application to automobile exhaust
Authors: Young Larry C. , Finlayson Bruce A.
Published: June 2004

Calculations are done for a series of mathematical models for a monolith catalytic converter to oxidize carbon monoxide in automobile exhaust. Phenomena studied include axial conduction in the wall, diffusion and conduction in the gas in a transverse direction perpendicular to the flow direction, multiple steady states, and transients giving wall temperatures exceeding the adiabatic temperature.
Digital monitorina and estimation of polymerization reactors
Authors: Jo J. H. , Bankoff S. G.
Published: June 2004

A free‐radical polymerization with kinetic equations taking into account monomer, polymer, and solvent transfer and initiation, termination, propagation, and inhibition reactions was studied both experimentally and by simulation to determine the performance of various Kalman filters, with feasible measurements used.
Performance of rotary flow cyclones
Authors: Ciliberti David F. , Lancaster Brian W.
Published: June 2004

An analysis of the operation of the rotary flow cyclone suggests that no dust below 1μ will be captured in this equipment under normal operting conditions, and that performance will not deteriorate with the use of a dirty secondary flow. Experimental data support these conclusions.
Mathematical modeling of monolithic catalysts
Authors: Heck Roland H. , Wei James , Katzer James R.
Published: June 2004

Mathematical models are developed which account for simultaneous heat transfer, mass transfer, and chemical reaction in the oxidation of carbon monoxide over platinum containing monoliths. A two‐dimensional model is shown to predict unusual behavior of the Nusselt number in the presence of rapid reaction. However, a simpler one‐dimensional model is adequate for predicting monolith behavior.
Mass transfer to drops moving through power law fluids in the intermediate reynolds number region
Authors: Wellek Robert M. , Gürkan Türker
Published: June 2004

The mass transfer rate to fluid spheres is calculated for power law and Newtonian fluids by using the intermediate Reynolds number stream functions of Nakano and Tien (1970) and Yamaguchi et al. (1974), respectively. The Sh increases with increases in Re and Pe and decreases in n. Better results are obtained with Nakano and Tien's functions when Re > 10 and with Yamaguchi's functions when Re < 10.
An effective computational algorithm for suboptimal singular and/or bang‐bang control I. Theoretical developments and applications to linear lumped systems
Authors: Nishida N. , Liu Y. A. , Lapidus Leon , Hiratsuka S.
Published: June 2004

A new and simple computational algorithm for obtaining suboptimal singular and/or bang‐bang solutions of typical lumped and distributed parameter control problems is proposed. The algorithm is based on the piecewise maximization of the Hamiltonian and a limiting process utilizing a penalty function of the control variables. Theoretical developments and computational applications of the algorithm to several linear lumped parameter control problems are presented. Extensions and applications of the algorithm to nonlinear and distributed parameter systems are given in Part II.
Interfacial phenomena in falling film evaporation of natural seawater
Authors: Van Der Mast Victor C. , Bromley Leroy A.
Published: June 2004

The fluid dynamics and heat transfer of boiling seawater in falling film evaporators have been investigated. Large interfacial disturbances have been observed, caused by surfactants in seawater. Although these disturbances enhance heat transfer, they increase entrainment and the tendency for scale formation in fluted tubes.
The steady and unsteady state analysis of a simple gas centrifuge
Authors: Auvil Steven R. , Wilkinson Bruce W.
Published: June 2004

The operating theory of the gas centrifuge is developed under both steady and unsteady state behavior. It is shown that countercurrent flow patterns in a gas centrifuge enhance the possible separation. The effect of self‐diffusion of the gaseous mixtures is shown to be significant with low molecular weight gases but of less significance with heavy gases such as uranium isotopes. The time required to develop steady state pressure and concentration profiles is in the order of minutes, even with no net flow to and from the machine.
Development and application of a simulation model for three‐phase distillation
Authors: Block Ulrich , Hegner Bernd
Published: June 2004

The model of the multicomponent, multistage distillation column has been extended to three coexisting phases. The new model contains the well‐known modeling equations of the two‐phase distillation column as a special case. The versatility of the new simulation model is demonstrated with practical distillation problems.
The effect of surfactant on the terminal and interfacial velocities of a bubble or drop
Authors: Leven M. Douglas , Newman John
Published: June 2004

Stream functions are dervied for a spherical droplet in creeping flow with an arbitary surface tension gradient at its interface. The stream functions are used to show theoretically that the terminal velocity is reduced and that the interfacial velocity is retarded, especially near the rear of the droplet, when a trace of surfactant is present in the exterior phase and when surface aging is controlled by diffusion.
A method of moments for measuring diffusivities of gases in polymers
Authors: Felder R. M. , Ma C‐C , Ferrell J. K.
Published: June 2004

A method of moments has been formulated for the determination of the diffusivity of a gas in a polymer from a step response in a continuous permeation chamber. Contributions of system components other than the polymer are easily factored out to determine the contribution of the polymer alone, and this contribution is then analyzed to calculate the diffusivity. The method has been applied to the measurement of the diffusivities of sulfur dioxide in PTFE (Teflon) and fluorosilicone rubber tubes over a wide temperature range.
Relationships between velocity profiles and drag reduction in turbulent fiber suspension flow
Authors: Lee Peter F. W. , Duffy Geoffrey G.
Published: June 2004

Analytical relationships between velocity profiles and flow resistance data are developed for suspensions of papermaking fibers in turbulent shear. The relationships apply to suspensions of synthetic fibers. The wall layer appears to be unaffected by the presence of fibers, and the cause of drag reduction can be attributed to the turbulent core region.
The hydrodynamic resolution of optical isomers
Authors: Howard D. W. , Lightfoot E. N. , Hirschfelder J. O.
Published: June 2004

A potentially simple and effective technique is proposed for separating enantiomorphic crystal pairs from each other, or separating individual enantiomorphs from optically active impurities.

This method consists essentially of settling under conditions controlling orientation of the asymmetric particles and taking advantage of the tensorial nature of their friction factors.
Scopolamine permation through human skin in vitro
Authors: Chandrasekaran S. K. , Michaels A. S. , Campbell P. S. , Shaw J. E.
Published: June 2004

The sorption and rate of permeation of scopolamine base in human skin have been measured as a function of drug concentration in aqueous solution contacting the stratum corneum surface of the skin. The sorption isotherm is nonlinear, and the apparent penetrant diffusivity computed from steady state permeation data is greater than that estimated from unsteady state (time lag) measurements.

By assuming that sorption occurs by both ordinary dissolution and binding of penetrant to immobile sites in the membrane, the experimental sorption isotherm can be predicted, and the disparity between steady state and time lag diffusivities can be reconciled.
Denitrification kinetics in packed beds
Authors: Parker A. L. , Sikora L. J. , Hughes R. R.
Published: June 2004

Bench scale packed columns were used to study the kinetic behavior of biological denitrification. After tracer studies were run to determine flow characteristics, steady state nitrate profiles were determined. A first‐order rate expression with an Arrhenius temperature dependence is an adequate model of the reaction for nitrate‐nitrogen concentrations of < 100 mg/l and temperature of 5° to 20°C. The rate constants are proportional to the packing surface area.
Finite amplitude equilibrium waves on the surface of nonvertical falling films
Authors: Javdani Kambiz
Published: June 2004

Experimental data on the frequency and wavelength of finite amplitude equilibrium waves on the surface of nonvertical laminar falling films of mineral oil at moderate Reynolds numbers are correlated successfully on the basis that the frequency of the wave remains constant during the course of its amplification.
On the dynamics of fluid interfaces. Part II
Authors: Ramabhadran T. E. , Byers Charles H. , Friedly John C.
Published: June 2004

Ultra high‐speed motion picture photography is used to measure the decay and frequency of drops of liquid in air and of air cavities in liquids. Consequent to the belief that surface active agents induce dynamic interfacial properties, a very clean system is used, and experiments are performed with triple distilled water, tap water, and known aqueous solutions of ionic and nonionic surfactants. Experimental results yield good qualitative agreement with the theory. The theoretical and experimental studies show the system to be a new and promising technique for the quantitative evaluation of the various interfacial viscous and elastic properties.
Diffusion of hydrocarbons in 13X zeolite
Authors: Ruthven Douglas M. , Doetsch Ingo H.
Published: June 2004

The kinetics of sorption of four representative hydrocarbons in 13X zeolite crystals have been investigated at temperatures within the range 409 to 513°K and pressures 0.1 to 100 torr. Extensive diffusivity data are presented showing the dependence on sorbate concentration and temperature. The form of the concentration dependence of the diffusivity for these systems is very similar to that of the small monatomic and diatomic molecules in 5A zeolite. This similarity is understandable, since the key factor which determines the diffusion behavior is the relative size of diffusing molecule and sieve window. For these hydrocarbons in the 13X sieve, as for the monatomic and diatomic gases in 5A, the critical diameters of the diffusing molecules are all appreciably smaller than the free diameter of the windows.
Growth and dissolution of potash alum crystals in the subsieve size range
Authors: Garside John , Jančić Slobodan J.
Published: June 2004

Overall growth and dissolution rates of potash alum crystals have been measured over the size range 3 to 70 μm. The derived surface integration growth kinetics, which are found to be linear with respect to supersaturation and strongly size dependent, are evaluated in terms of the step model of crystal growth. The results emphasize the importance of independently measuring growth kinetics before secondary nucleation kinetics can be calculated from MSMPR experiments.
A new tracer method for determination of liquid‐solid contacting efficiency in trickle‐bed reactors
Authors: Schwartz J. G. , Weger Eric , Duduković M. P.
Published: June 2004

A new tracer technique is reported for the determination of liquid‐solid contacting efficiency and liquid holdup in trickle beds packed with small alumina particles. Holdup was a function of liquid mass velocity for both porous and nonporous packing. Contacting efficiency remained uniform at a level of 65%.
Selective hydrogenation and mass transfer in a fixed‐bed catalytic reactor with gas‐liquid concurrent upflow
Authors: Mochizuki Satoshi , Matsui Tatsuro
Published: June 2004

Reaction rates of selective hydrogenation of phenylacetylene (PA) and styrene were studied in a packed‐bed reactor with concurrent gas and liquid upflow. The surface reaction rates were expressed by the reaction between adsorbed PA or styrene and dissociated hydrogen atoms competing for the same active sites. The contributions of mass transfer rate were determined, and better selectivity conditions were discussed.
Adsorption of nitric oxide in aqueous slurries of activated carbon: Transport rates by moment analysis of dynamic data
Authors: Niiyama Hiroo , Smith J. M.
Published: June 2004

Moment analysis of input‐response data for three‐phase slurry reactors is shown to be useful for detrmining mass trasnport rate coefficients. Data for the nitric oxide‐water activated carbon system indicated that bubble‐to‐liquid transport, intraparticle diffusion, and the adsorption step could all influence the adsorption rate for high concentrations of carbon particles.
On the optimization by boundary control of tubular reactors with catalyst decay
Authors: Gruyaert Frans , Crowe C. M.
Published: June 2004

In optimization problems dealing with catalytic reactors, where the catalyst deactivates slowly with time, it is common to assume a quasi steady state in the reaction and deactivation equations. Although the difference in reactor performance, for a given control policy, between the unsteady state reactor and its quasi steady state approximation is usually negligible, a very large difference can exist in the optimal control policy for the two models. For a single irreversible reaction, where the catalyst deactivation is dependent on conversion and where the control variable is the temperature of the fluid entering a tubular reactor, it is shown numerically that the performance of the reactor for a suboptimal control policy can be significantly superior to the optimal performance predicted from a quasi steady state model formulation.
Equilibrium staged parametric pumping. I. Single transfer step per half‐cycle and total reflux—the analogy with distillation
Authors: Grevillot Georges , Tondeur Daniel
Published: June 2004

Equilibrium staged batch parametric pumps are studied with nonlinear isotherms. The half cycle is composed of one single equilibration step and one discrete transfer. The limiting regime (for infinite number of cycles) is shown to correspond to a staircase construction between the two isotherms, the number of steps being equal to the number of stages. The reservoir concentrations are then connected by Fenske's equation. Several analogies with binary total reflux distillation are suggested.
The modeling of hematite reduction with hydrogen plus carbon monoxide mixtures: Part II. The direct reduction process in a shaft furnace arrangement
Authors: Tsay Q. T. , Ray W. H. , Szekely Julian
Published: June 2004

A mathematical model was developed for the direct reduction of hematite carried out in a countercurrent moving packed bed, and the process was simulated on a CDC 6400 computer. The response of the model to changes in the various process variables was investigated, and it was found that there is an optimum gas inlet composition (hydrogen‐carbon monoxide) for a given set of operating conditions. In addition, an optimum gas inlet temperature was revealed for cases where pure carbon monoxide was used as the reducing gas. The feasibility of side stream injection of reducing gas was studied. The calculations showed that there are certain ranges of operating conditions for which the injection of a hot side stream is advantageous. This study represents the first reported simulation of direct reduction process having carbon monoxide‐hydrogen gas mixtures as a reducing medium.
Steady state diffusion of oxygen in red blood cell and model suspensions
Authors: Stroeve Pieter , Colton Clark K. , Smith Kenneth A.
Published: June 2004

Experimental measurements were made of the steady oxygen permeation rate through films of nonreactive and reactive dispersions, including suspensions of red blood cells. The data compare well with a theoretical analysis which incorporates a one‐step reversible reaction within the dispersed phase. In the absence of reaction, the red cell permeability could be treated as that of a concentrated hemoglobin solution. For reactive suspensions of red cells or water‐in‐oil emulsions containing hemoglobin at 25°C, substantial facilitation of oxygen transport occurred when oxyhemoglobin gradients were steep, but both the data and the theory exhibited considerably less facilitation than would be suggested by an equilibrium analysis.
Enzymatic regeneration of ATP: II. Equilibrium studies with acetate kinase and adenylate kinase
Authors: Langer Robert S. , Gardner Colin R. , Hamilton Bruce K. , Colton Clark K.
Published: June 2004

Equilibria of reactions catalyzed by acetate kinase and adenylate kinase were studied experimentally and theoretically. Nucleotide conversions in excess of 90% were obtained with reactants (acetyl phosphate and one nucleotide) in stoichiometric proportion for ATP regeneration from either ADP via acetate kinase or AMP via the coupled enzyme system. Observed equilibrium constants, measured as a function of [Mg2+] at pH 7.4, ranged from about 1 to 9 for the reaction catalyzed by adenylate kinase and from about 50 to 400 for the reaction catalyzed by acetate kinase. These results agreed well with prediction of a theoretical model for the multiple equilibria between all species present in solution. Theoretical calculations showed that magnesium ion complexes and totally dissociated anions are the predominant species in solution at \documentclass{article}\pagestyle{empty}\begin{document}$p{\rm H}\tilde > 7{\rm and}[{\rm Mg}^{2 + } ]\tilde > 10^{ - 3} {\rm M}$\end{document}.
Fluid vortices and mass transfer in a curved channel artificial membrane lung
Authors: Gilroy Keith , Brighton Elspeth , Gaylor John D. S.
Published: June 2004

Experimental assessment of theory on the convective dispersion of blood gases by vortices in a curved channel exchanger has demonstrated the impracticality of the proposed design. A nonlinear stability analysis of the fluid dynamics provided an amplitude factor an order of magnitude less than that previously assumed for the system secondary circulations.
A compartmental dispersion model for the analysis of mixing in tube networks
Authors: Ultman James S. , Blatman Hal S.
Published: June 2004

A compartmental dispersion model of longitudinal mixing in tube networks has been developed. The ability of this model to predict the impulse response of helium, benzene vapor, and sulfur hexafluride tracer gases in two and in five generation symmetric network models of the large airway system of the lung has been tested over an air flow range of 1 to 400 ml/s.

The results imply that velocity profile distortion and secondary flows in branching regions have only a small effect upon the overall longitudinal mixing when flow is directed toward the higher‐order generations. On the other hand, accurate prediction of the data requires adequate treatment of the finite rate of evolution of the Taylor dispersion occurring in these tube networks.
Nonisothermal nip flow in calendering operations
Authors: Dobbels Frans , Mewis Jan
Published: June 2004

An efficient and simple numerical technique is presented for analyzing nonisothermal nip flow of viscous liquids. It has been applied on calendering to calculate the design parameters as well as the interaction effects between roller characteristics, operation conditions, and material properties. Viscous heating is shown to drastically change the mechanics near the nip exit if the rollers rotate at different speeds. Consequences for scaling‐up and model experiments are indicated.
Use of trajectory analysis to study stability of colloidal dispersions in flow fields
Authors: Zeichner G. R. , Schowalter W. R.
Published: June 2004

Trajectories have been computed for two equal sized spherical particles in simple laminar shearing and in uniaxial extensional flows. Effects of interparticle attraction, electrostatic repulsion, and hydrodynamics were included.

The results are pertinent to questions of colloidal stability under various conditions of flow. Particulate dispersions can react in several different ways as the intensity of shearing is increased from zero: the dispersion can remain stable; it can be redispersed, if it had been initially flocculated into a weak secondary minimum in the interparticle potential curve; it can be flocculated into a strong primary minimum in the potential curve; or, in extreme cases, it can be redispersed from the primary minimum. Results are presented which illustrate criteria for flocculation or stability to both laminar shearing and extensional flow. It is shown that hydrodynamic effects can significantly alter the criteria developed for stability of dispersions to Brownian coagulation.
Limiting criteria for intrinsically stable equilibrium in multiphase, multicomponent systems
Authors: Slattery John C.
Published: June 2004

Necessary and sufficient conditions for intrinsically stable equilibrium in a multiphase, multicomponent body are developed with interfacial effects taken into full account. There is a limiting criterion for intrinsic stability that must be satisfied within every phase, and there is another limiting criterion that must be satisfied on every phase interface. The limits of intrinsic stability for a multiphase, multicomponent body are defined by the failure either of the first criterion within one of the phases or of the second criterion on one of the phase interfaces.
Liquid diffusion in microporous alumina pellets
Authors: Prasher Brahm D. , Ma Yi Hua
Published: June 2004

The effect of the ratio of the molecular solute diameter to the pore diameter and adsorption equilibrium on the liquid phase effective diffsivity for different hydrocarbon solutes was studied in two alumina pellets. A semiemprical correlation based on the relative dimension of the solute molecule with respect to the average pore dimension, the equilibrium partition coefficient, and the porosity is proposed for a variety of binary hydrocarbon systems. The correlation shows that the effective diffusivity is strongly influenced by both the adsorption coefficient as well as the ratio of the solute molecular size to the average pore size.
Combustion kinetics in the modeling of large, pulverized fuel furnaces: A numerical experiment in sensitivity
Authors: Lowe Allen , Wall Terry F. , Stewart Ian McC.
Published: June 2004

A mathematical model of combustion in a utility type of pulverized, coal fired furnace is developed by dividing the furnace into a number of isothermal zones. The method dovetails the combustion rate data available for single char particles with a gas flow pattern to predict local combustion heat release rates and local radiation absorption coefficients, which are used as input to a zoned heat transfer model.

The furnace heat transfer is shown to be insensitive to combustion related parameters such as coal rank and coal fineness. For carbon in ash, local gas temperature, and to a lesser extent local heat flux, significant variations are predicted. It is concluded that for calculation of radiative heat transfer, combustion data are adequate. Further research activity on ignition and combustion stability, together with the radiative properties of fly ash, is recommended.
Influence of drag reducing polymers on turbulent mass transfer to a pipe wall
Authors: McConaghy George A. , Hanratty Thomas J.
Published: June 2004

Completely developed and entry region mass transfer rates in turbulent pipe flow of drag reducing polymer solutions were studied experimentally using electrochemical techniques. The percent change in the fully developed mass transfer rate at a given volumetric flow was found to be greater than the percent change in the pressure gradient. The data are interpreted by using the law of the wall, valid for Newtonian fluids at large Schmidt numbers, whereby K+ is related to Sc−0.74. The proportionality constant is correlated with percent drag reduction and is found to decrease with increasing drag reduction. The use of an analogy between momentum and mass transfer predicts a somewhat greater mass transfer reduction than was observed.
Crystal size distribution dynamics in a classified crystallizer: Part I. Experimental and theoretical study of cycling in a potassium chloride crystallizer
Authors: Randolph Alan D. , Beckman James R. , Kraljevich Zlatica I.
Published: June 2004

Cycles in particle size and slurry density were experimentally observed in a mixed suspension, potassium chloride crystallizer equipped with a fines dissolver and having nonrepresentative product withdrawal. Cycling behavior was achieved with a product crystal elutriator but was also observed with changes in the orientation of the product removal tube, indicating that instability was induced by product classification. Simulation of the unstable runs with a dynamic model showed crystal size distribution (CSD) limit cycles of similar period using nucleation kinetics and process conditions measured experimentally. The computer simulation showed no tendency towards cycling for the stable runs.
Mechanisms and idealized dissolution modes for high density (ρ > 1), immiscible chemicals spilled in flowing aqueous environments
Authors: Thibodeaux L. J.
Published: June 2004

A plausible spill mechanism is proposed and idealized dissolution modes are developed for the prediction of lifetime and downstream cup‐mixing concentration of spilled liquids. Four models are developed which reveal that detailed knowledge of the quantity and distribution of geometric shapes that make up the bottom residing interface between the spillage and the overlaying water are the independent variables of primary importance.
Simulated binary isothermal adsorption on activated carbon in periodic countercurrent column operation
Authors: Klaus Roland , Aiken Richard C. , Rippin David W. T.
Published: June 2004

Simulation studies are presented of single‐ and two‐component adsorption in periodic, countercurrent, multicolumn systems. It is demonstrated that long adsorption profiles are likely to occur in the adsorption of organic contaminants from wastewater onto activated carbon, thus favoring the use of multicolumn rather than single‐column systems. For two‐component adsorption in a multicolumn system, it is shown that more switching periods are needed than in the single‐column case before the profiles stabilize, that the stabilized profiles can differ substantially from those found in a single‐column system, and that their shape is strongly influenced by the relative concentrations of the components in the feed.
The chemical engineering side of nuclear fusion power
Authors: Johnson Ernest F.
Published: June 2004

It is widely recognized that chemical engineering has important roles to play in the development of national and worldwide energy resources through optimal utilization of fossil fuel reserves. It is much less appreciated that there are crucial chemical engineering problems in the development of energy production from other sources. In particular, the successful development of nuclear fusion power generating systems will require the solution of many problems that are uniquely suited to chemical engineers.

This paper presents a brief overview of the fusion development program for magnetically confined fusion power reactors and an identification of the major technological problems remaining to be solved.
An improved corresponding states method for polar fluids: Correlation of second virial coefficients
Authors: Tarakad Ramanathan R. , Danner Ronald P.
Published: June 2004

An improved four‐parameter corresponding states method that includes polar fluids has been developed. The four parameters are the critical temperature, the critical pressure, the radius of gyration, and a newly developed polarity factor based on the second virial coefficient. These parameters have been used to empirically correlate pure and interaction second virial coefficients of a variety of fluids.
Dispersion in layered porous media
Authors: Moranville M. B. , Kessler D. P. , Greenkorn R. A.
Published: June 2004

Experimental data on directional dispersion coefficients in transversely isotropic media, a special case of anisotropic media, were determined in models consisting of alternating layers of sintered glass and unconsolidated glass beads. Values of appropriate parameters to relate the velocity to the directional dispersion coefficient were determined for a variety of permeabilities and angles. Sensitivity of these parameters with respect to angle was determined, and results are presented which will permit estimate of when this effect is significant.
Stochastic models of algal photosynthesis in turbulent channel flow
Authors: Sheth Mayur , Ramkrishna Doraiswami , Fredrickson Arnold G.
Published: June 2004

Models have been formulated and analyzed for photosynthesis by algae in turbulent, channel flow. Analytical and computational for results for different stochastic, kinematic models of algal motion have been obtained for two different rate mechanisms. The results indicate that turbulent mixing can achieve an increase in the rates and efficiencies of photosynthesis by realizing the intermittency effects. Optimum levels of turbulence are shown to exist in turbulent channel flow for the mass cultivation of algae. The methodology of this paper is relevant to photochemical reactions in general.
The effect of surfactants on the stability of fluid interfaces during phase transformation
Authors: Palmer Harvey J.
Published: June 2004

The influence of surface active solutes on the stability of fluids during phase transformation is examined both experimentally and theoretically. Experiments on the interfacial stability of triethanolamine as it steadily evaporates into a partial vacuum verifies that for high surface tension fluids, spontaneous convection induced by differential vapor recoil is stabilized by the addition of surfactants and that the degree of stability increases with the surface activity of the surfactant. The hydrodynamic stability of surfactant solutions undergoing phase transformation is then examined using linear stability analysis. Results reveal that surfactants have a marked stabilizing effect on the differential vapor recoil mechanism but have essentially no effect on the fluid inertia and moving boundary destabilizing mechanisms. Consequently, the maximum stabilizing effect of surface active solutes on liquids evaporating under vacuum is determined by the criterion for fluid inertia instability.
Equilibrium staged parametric pumping: II. Multiple transfer steps per half‐cycle and reservoir staging
Authors: Grevillot Georges , Tondeur Daniel
Published: June 2004

The limit regimes of equilibrium staged batch parametric pumps are studied. The half‐cycle comprises several equilibrations at each temperature, each followed by a discrete transfer of fluid. The concentration distribution of the effluent of each half‐cycle is conserved by a cascade of reservoirs. The concepts, methods, and McCabe‐Thiele representation are first introduced on the example of the (one‐stage, two transfer) pump. The generalization to the (one stage, n transfer) pump leads to a limit regime represented by a staircase construction between the two isotherms, the number of steps of the staircase being equal to the number of transfer steps. The limit regime of the general (N stage, n transfer) pump is then analyzed in terms of the properties of the (one stage, n transfer) pump considered above and of the (N stage, one transfer) pump discussed in the preceding paper of this series. An analytical solution for the separation factor is given in the case of linear isotherms. The importance of conserving the effluent concentration distribution is illustrated by graphical and numerical comparisons with pumps where this is not done.
Two‐phase downflow through catalyst beds: Part II. Pulsing regime pressure drop
Authors: Talmor E.
Published: June 2004

Surveys of local and overall pressure drop in partially pulsing 29.2 cm diameter beds show the overall pressure drop steady but elevated, while local pressure drops across various sections of the bed oscillate in correspondence with the local pulse frequency. The increase in overall pressure drop due to pulsing varies between 0 and 100%, depending on the extent of pulsing and liquid holdup within the bed.

In foaming systems, the overall bed pressure drop can be higher than for pulsing alone, depending on liquid holdup and (apparently) the type of foam and its intensity. In some cases, pulsing appears to be the starting point for low frequency foaming pressure drop surges which are associated with cyclic foam formation and breakup within the bed.
Analytical model reduction of large scale linear dynamic systems
Authors: Edgar T. F. , Schwartz J. S.
Published: June 2004

A class of dynamic model approximation techniques based on a frequency domain Taylor series expansion is presented. These methods yield low‐order models and are analytical rather than computational in nature; that is, one can retain important parameters (which may be time varying) from the original model in functional form in the low‐order model. This feature is very attractive for on‐line updating of the simplified model and subsequent control of the process. An example for a tenth‐order original model has shown that the analytical low‐order models provide excellent approximations to the step response of the original system.
Combined pressure and diffusional transition region flow of gases in porous media
Authors: Alzaydi Ayad A. , Moore Charles A. , Rai Iqbal S.
Published: June 2004

Expressions were derived for combined pressure and diffusional transition region flow of gases in porous media. Experimental systems were developed to verify the applicability of the equations for packed columns of Kaolinite clay and quartz sand with methane and carbon dioxide flowing into nitrogen.
Scaling laws and the differential equations of an entrained flow coal gasifier
Authors: Kane Ronald S. , Mc Callister Robert A.
Published: June 2004

A formal order of magnitude analysis was applied to the differential equations describing mass, momentum, and energy transport in an axially translating, vortex flow field and used to determine the importance of various terms. Significant dimensionless parameters, suitable for establishing scaling laws, appear naturally from the equations. Among the important parameters are the swirl number, geometric scale ratio, Froude number, and particle loading ratio. These parameters were combined to establish rules for complete similarity between a model and a prototype gasifier.
A formulation for ϵM and ϵH based on the surface renewal principle
Authors: Thomas Lindon C.
Published: June 2004

This paper presents a simplified formulation for ϵH for low to moderate Prandtl number fluids and for ϵM that utilizes the surface renewal model, but which also accounts for the fact that eddies do not reach the surface. The predicted trend in Prt obtained on the basis of the present analysis suggests an opposite dependency on Pr to that predicted by many of the other analyses.
Bubble nucleation in viscous material due to gas formation by a chemical reaction: Application to coal pyrolysis
Authors: Attar Amir
Published: June 2004

Most coals swell when heated, and their plastic properties change. These phenomena are explained qualitatively and semiquantitatively using a theory which combines classical nucleation theory and chemical kinetics.

Classical bubble nucleation theory is modified to include cases where gases are formed in a liquid as a result of a chemical reaction. Part of the gas that is formed in the liquid escapes through the surface. However, the concentration of gas that remains in the solution increases until a critical concentration is reached. When the critical concentration of gas in the solution is reached, bubbles will begin to nucleate.

The value of the rate of nucleation has a critical upper limit which is determined by the thermodynamic properties of the solution. However, the kinetics of the heat, momentum, or mass transfer may reduce the thermodynamic rate.

The criteria to decide which transport mode limits the kinetics of the nucleation were derived and applied to melting coal. In coal, the rate of bubble nucleation appears to be limited by the rate of momentum transfer in the melt.

The size of the melting coal particle determines the ratio of surface area to volume and thus affects the kinetics of the accumulation of gaseous reaction product in the melt. Thus, smaller rates of bubble nucleation will be observed in smaller coal particles (very viscous melts).

Kinetic equations are derived and used to estimate the time that is required for bubbles to appear inside a coal particle. A general method is proposed to calculate the time‐temperature contour at which nucleation will occur. The effect of the particle size on the time of nucleation is calculated. The results of the calculations yield values which compare very well with experimental results on coal.
An observation of the effect of integral scale on drag reduction
Authors: Berman Neil S. , Griswold Susan T. , Elihu Shahram , Yuen John
Published: June 2004

Drag reduction pipe flow experiments using random coiling polymers have been dominated by the small scales of turbulence. An experiment is reported using polyelectrolytes DNA and collagen, which have extended conformations in solution that shows a relationship between the large scales and drag reduction. Turbulent or molecular interactions can explain the observed increase in drag reduction with an increase in pipe diameter.
Real‐time estimation of aerobic batch fermentation biomass concentration by component balancing
Authors: Zabriskie Dane W. , Humphrey Arthur E.
Published: June 2004

Real‐time estimates of biomass concentration and growth rate in fermentation processes were obtained by performing a material balance on oxygen and employing a kinetic model for molecular oxygen utilization. A model containing yield and maintenance terms was satisfactory in fermentations where only the EMP and TCA pathways were utilized for glucose metabolism. However, model alterations based on metabolic energetics were required before accurate estimates were obtained for a metabolically complex fermentation producing bakers yeast.
Bounds and approximate solutions to linear problems with nonlinear boundary conditions: Solidification of a slab
Authors: Glasser David , Kern Jochen
Published: June 2004

In solidification, one is primarily interested in the movement of the solid‐liquid interface and not in the details of the internal temperature distribution. This is parallelled in many other processes of practical interest. Because of the linearity of the governing equation, one may readily obtain an integral relationship between the system variables, as expressed by the moment equations. By further introducing physically reasonable assumptions, one obtains bounding or approximate solutions, some of which are simple but accurate analytic expressions.
Mixing and mass transfer at high liquid rates in the steady state counterflow operation of packed columns
Authors: Hatton T. Alan , Woodburn Edward T.
Published: June 2004

Carbon dioxide absorption profiles have been measured for high liquidgas ratios in an absorption column operated at atmospheric pressure under steady state counterflow conditions. Mixing and mass transfer parameters were extracted from these profiles using an extension of the technique described by Brittan (1967). The flow ranges covered are 15 < Res < 100 and 300 < ReL < 1 600.

The dispersion data reflect the same trends as shown by dynamic testing methods (Woodburn, 1974). However, with decreasing liquid‐gas ratios the effect of dispersion on steady state mass transfer becomes less significant than would be inferred from dynamic testing results.

Under reverse gas flow conditions, the mass transfer coefficients corrected for the effects of axial dispersion show the same functional dependency on liquid rate as given by the Sherwood and Holloway (1940) correlation and provide a quantitative explanation for the anomalous behavior exhibited by their results in this liquid range.
Interfacial resistance to interphase mass transfer in quiescent two‐phase systems
Authors: Brenner Howard , Leal L. Gary
Published: June 2004

Interfacial resistance to solute mass transfer between two unstirred immiscible fluids is theoretically calculated. Solute molecules are modeled as Brownian particles, bathed by homogeneous fluid continua when wholly immersed in either fluid, or else by heterogeneous fluid continua when instantaneously straddling the interface. These diffusing particles are assumed to be subjected to either repulsive or attractive conservative forces exerted on them by the interface. Additionally, their mobility is supposed affected by proximity to the interface. Circumstances are found to exist under which the interface may offer significant resistance to interphase transport. Surprisingly, conditions also exist in which the interface may actually offer a negative resistance to such solute transfer. In such cases, the presence of the interface enhances the overall interphase mass transfer rate.
The homogeneous nucleation of bubbles in superheated binary liquid mixtures
Authors: Holden Bruce S. , Katz Joseph L.
Published: June 2004

It is shown how to apply homogeneous nucleation theory to predict the limits of superheat of multicomponent liquid mixtures. Measurements of such limits for n‐pentane‐n‐hexane, n‐hexane‐cyclohexane, benzene‐cyclohexane, and benzene‐n‐hexane mixtures as a function of composition are presented and compared with theory.
Performance of slurry and trickle‐bed reactors: Application to sulfur dioxide removal
Authors: Goto Shigeo , Smith J. M.
Published: June 2004

Methods are developed for predicting the performance of different types of three‐phase reactors for removal of a gaseous reactant by catalytic reaction. The removal is assumed to occur by mass transport of reactant from gas‐to‐liquid and liquid‐to‐catalyst particle and then by intraparticle diffusion and reaction in the liquid filled pores. The method is applied to the oxidation of sulfur dioxide at 25°C and 1 atm using activated carbon, in the presence of water, as a catalyst. Slurry, trickle‐bed, and counterflow packed‐bed reactors are compared in terms of the key variables affecting the fraction of sulfur dioxide reacted.