bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of thermodynamics to the athabasca tar sands
Authors: Leja J. , Bowman C. W.
Published: March 2009

Significant changes in the interfacial areas often accompany transformations in highly dispersed systems containing oil, water, solid and gas phases. When such changes in area are considered, interfacial tension expressions diametrically opposed to the conventional criteria for oil spreading or de‐wetting may result. Further modifications in the energetics criteria are obtained when the electrical contributions to the free energy of the system (resulting from the adsorption of ionic surfactants) are included.
Electric field phenomena in fluidized and fixed beds
Authors: Katz Herbert , Sears John T.
Published: March 2009

Stabilization of a bed of dielectric particles against fluidization by an electric field (≥ 103 volts/cm) is described. Glass bead and silica gel particle beds have been observed to behave as packed beds with flow rates (and pressure drops) of the fluidizing gas up to 15 times the normal incipient fluidization rate. The pressure drop at the breakup of this fixed bed was dependent on the second power of voltage, the particular bed material, and geometry of the system. Under suitable conditions 100% bed expansion without diffusive particle motion or bubble formation was obtained using silica gel particles. Comparison with iron particle bed‐magnetic field effects are presented. Surface polarization charge effects are the simplest explanation of the phenomena. Several of the possible applications are suggested, such as precipitation enhancement in an aerosol filter or as a new tool for investigating aggregative fluidization.
Compressibility factors for the argon‐carbon dioxide system
Authors: Beer H.
Published: March 2009

Redlich and Kwong's equation of state for compressible gases has been used for computing the compressibility factors for binary gaseous mixtures. The mean deviation between the experimental values of the factor and the values calculated from Redlich's equation is 2.2%. Data for CH4 ‐ CO2 and Ar ‐ CO2 mixtures up to pressures of 200 atm. and temperatures of 453°K in the whole range of composition have been obtained. The experimental error is estimated to be ± 0.74%.
Asymmetric, coupled transport of heat and mass in a duct
Authors: Chen T. S. , Sparrow E. M.
Published: March 2009

Mutually dependent heat and mass transfer for laminar gas flow in a parallel‐plate channel is investigated analytically. Sublimation occurs at one of the channel walls, while the other wall is nonsubliming. Both walls are thermally insulated from the external environment. The analysis of the problem requires simultaneous treatment of the energy and mass diffusion equations, with coupling provided by the boundary conditions. Mathematical expressions are derived and numerical results are presented for various quantities that characterize the heat and mass transfer processes. Comparisons are made with the case of symmetric transfer (i.e., both walls actively participating). In general, unsymmetric transfer is found to slow down the axial development of the temperature and mass fraction fields.
A method of prediction of the porosities of high‐pressure gaseous fluidization systems
Authors: Mogan J. P. , Taylor R. W. , Booth F. L.
Published: March 2009

The porosity of a fluidized bed at any superficial velocity may be calculated by Richardson and Zaki's method if the terminal velocity of a representative particle is known. This terminal velocity can be calculated under any operating conditions by Beranek's atmospheric elutriation criterion.

Porosities were measured at 331 superficial velocities in fluidized beds of cracking catalyst, using hydrogen, nitrogen and argon at pressures of 300 to 800 p.s.i.g. as the fluidizing media. It was postulated that the “largest significant particle” was representative for beds fluidized with high‐pressure gases such as these.

The porosities at these same velocities were calculated using Beranek terminal velocities of the “largest significant particles” in Richardson plots. A 16.6% standard deviation was found in the values of the calculated porosities when compared with the measured values.
Kinetics of catalytic ethane hydrogenolysis: Stirred reactor study of commercial nickel catalyst
Authors: Tajbl D. G.
Published: March 2009

The kinetics of ethane hydrogenolysis catalyzed by a commercial 58% nickel‐on‐kieselguhr catalyst were studied at 1 atm. and from 220° to 250°C. The kinetic data could be fit by a simple power rate equation that is a limiting case of a more general equation. The reaction rate of ethane was first order with respect to ethane and —2 order with respect to hydrogen. A possible reaction mechanism is discussed. The apparent activation energy was 46.4 kcal. Ethane/hydrogen ratios as high as 1:1 were studied without catalyst deactivation. Kinetic data were obtained in a novel stirred‐tank catalytic reactor.
Liquid phase oxidation of the light ketones
Authors: Rouchaud J. , Lutete B.
Published: March 2009

Acetone, methyl ethylketone, methyl isopropylketone and toluene were oxidized separately in the liquid phase by oxygen at 140°C, under 15 atm partial pressure of oxygen with 1 wt % di‐ ter‐ butylperoxide. The main product is acetic acid. Acetone is much less reactive than the other two ketones. Cooxidations of binary mixtures composed of a ketone and toluene were performed under the same experimental conditions. In these cooxidation systems, the three ketones have similar reactivities. The discrepancy between the relative reactivities of the ketones oxidized alone or with toluene is interpreted by the theory of the branched chain oxidations, and indicates the great influence of the chain branching coefficients and the stability of the free peroxy radicals on the total rate of oxidation of the ketones.
Calibration of an argon plasma jet and preliminary application to production of oxygen by carbon dioxide reduction
Authors: Blanchet J. L. , Parent J. R. , Lavallee H. C.
Published: March 2009

An argon plasma jet generator hag been built and calibrated for various power inputs, arc gas flow rates, electrode gaps and anode materials. The gas enthalpy and its temperature, the heat losses, the impact pressure, the exit gas velocity and the heat flux have been calculated from the collected data. Comparisons with helium were also made.

Injection of carbon dioxide into the plasma flame has yielded up to 3% of oxygen in the effluent gas. The reaction temperatures ranged from 3,000 to 11,000°K.
Recent experience with the spherical agglomeration process
Authors: Sirianni A. F. , Capes C. E. , Puddington J. E.
Published: March 2009

The process of removing particles from liquid suspension by selective wetting and agglomeration with a second immiscible liquid has many possible applications. Depending upon the amount of tthe second liquid used and the type of agitation to which the suspension is subjected, the particles to be separated are settled as flocs, as dense pellets or may simply be transferred to a continuous phase of the second liquid. This paper first describes the types of mixing equipment which have been used to carry out the process in its various forms and goes on to discuss a number of specific applications. These include the upgrading of coking coals by selective agglomeration, the pelletization of soluble salts, the formation of highly spherical bodies from various materials and the beneficiation of ores.
Hydrogen‐oxygen ion‐exchange membrane fuel cells
Authors: Foulkes F. R. , Graydon W. F.
Published: March 2009

A hydrogen‐oxygen cationic ion‐exchange membrane fuel cell was operated at various temperatures, pressures, and electrolyte concentrations. The open circuit and discharge characteristics of the cell were explained in terms of the oxygen polyelectrode theory. Although discharge was limited by internal resistance, pressurization greatly reduced polarization.
Simulation and optimization of an existing ethylbenzene dehydrogenation reactor
Authors: Sheel J. G. P. , Crowe C. M.
Published: March 2009

The dehydrogenation of ethylbenzene to styrene in an ideal, adiabatic reactor has been modelled using side reactions in addition to the main one. The differential equations describing the process were integrated on an IBM 7040 digital computer.

A profit function ($ gained/hour) was chosen and for various combinations of process variables, which were subject to constraints, the single bed reactor was optimized by the method of Rosenbrock(1,2). Studies of a proposed two‐bed reactor were also carried out. Catalyst deactivation during the reaction was not considered because of a lack of data.

The results showed that the existing reactor could be operated more efficiently if the present plant constraints were removed. Two beds in series gave still better results.
Forced convection heat‐transfer from the heated downstream end of a cylinder placed in front of a similar, axially aligned, unheated cylinder
Authors: Babij G. B. , Godward R.
Published: March 2009

Experiments, performed to obtain the average forced convection heat‐transfer coefficients from the heated downstream end of a cylinder, placed in front of a similar, axially aligned, unheated cylinder, produced the following results: (1) The Nusselt number can be correlated by an equation of the type NNuf = C NRebn, where C takes on values of 1.01 to 2.13 and n = 0.466 for the spacing between the two cylinders from ½‐in. to 6‐in. (2) In the range of Reynolds number from 3 × 104 to 5 × 105, the Nusselt number increases with the spacing between the two cylinders. At a spacing of 4‐in. a maximum Nusselt number is reached.
Solids concentration profile in the bubble column slurry reactor
Authors: Farkas Edward J. , Leblond Pierre F.
Published: March 2009

Solids concentration profile was measured for the basic babble column slurry reactor configuration: steady flow with respect to gas and batch with respect to solid and liquid. The result confirmed the exponential profile predicted by a diffusion model. An application is discussed.
The shape of a fluid drop approaching an interface
Authors: Hartland Stanley
Published: March 2009

The shape of a fluid drop approaching an interface does not change appreciably with time and is very close to the equilibrium dimensions, in spite of the large pressure gradient which is present in the draining film. This is because the net vertical force due to the excess pressure in the draining film above that in the drop is identical with that for an equilibrium film being zero for a plane interface and —2Rσ sin2 ϕ for a deformable interface. Employing this result in a force balance around the drop which is independent of the bulk interface shows that the area A of the draining film between a fluid drop of volume V and a deformable fluid‐liquid interface is given by

where σ is the interfacial tension and Δρ the density difference between the drop and surrounding fluid, 1/b is the curvature at the top of the drop and h is the distance between this point and the edge of the draining film which is inclined to the horizontal at an angle ϕ. When the interface is a rigid plane the overall curvature 1/R of the draining film and the volume v enclosed by it, together with the angle ϕ are all zero.

The limiting cases of the expression for very small and very large drops agree with those previously established for both deformable and rigid interfaces. An approximate expression which applies when cV2/3 (where c = Δρg/σ) is between 0.6 and 13.5 and which gives A to within ± e% is

where for a rigid plane interface

and for a deformable interface

When the densities of the drop and bulk heavy fluids are equal, but their respective interfacial tensions σ12 and σ23 with the light fluids are different, the expression becomes

which estimates A/V2/3 to within about ± 25% for σ12/σ23 in the range 0.11 to 9.0 and cV2/3 (where c = Δρg/σ12) between 0.6 and 13.5.
Pulsation error in a rotameter
Authors: Baird M. H. I. , Cheema M. A.
Published: March 2009

The effect of square‐wave pulsations in gas flow on the performance of a rotameter has been studied. The experimental variables were pulsation frequency (1–24 Hz), gas flow rate, gas density, float mass, and the gas volume between the pulse generator and the flowmeter. The fluctuation in float position was found to decrease with increasing frequency and this was in agreement with a simplified theoretical model. Pulsation caused the rotameter to over‐read by as much as 100% and in some cases the error was appreciable even when the float was almost stationary. The error decreased as the damping volume was increased.

The factor of error was correlated empirically with the above variables. The results were also compared with other published data and theory, and with a numerical solution of the equations of motion of the float. The numerical solution was found to predict the error satisfactorily in cases where a damping chamber was used and where float bouncing did not occur.
Sonochemical cavitation phenomena in small bubbles
Authors: Fogler Scott
Published: March 2009

A theoretical study has been made on collapsing cavities in liquids. When a chemical reaction is not occurring in the cavity, the departure from the Rayleigh collapse time increases with decreasing Weber number. When a chemical reaction is taking place within the cavity, the conversion first decreases and then increases with decreasing initial radius of the cavity owing to the interaction of collapse time and gas temperature within the cavity. For large cavities the viscous damping effects are almost negligible, while for small cavities the damping of the cavity motion is quite significant. When an exothermic reaction is taking place within the cavity, the velocity of the cavity wall and maximum radius achieved upon rebound increase with each successive rebound until chemical equilibrium is approached. The influence of an increase in the number of molecules formed during the reaction upon collapse is described in the text along with a discussion of how various parameter and dimensionless groups affect the collapse of the cavity.
Bubble drag and mass transfer in non‐newtonian fluids: Creeping flow with power‐law fluids
Authors: Hirose T. , Moo‐Young M.
Published: March 2009

The drag and mass‐transfer characteristics of a gas bubble moving in power‐law non‐Newtonian fluids are examined analytically in terms of the rheological properties of the system. An approximate solution for the case of creeping flow around circulating bubbles shows that the mass‐transfer coefficient is enhanced for pseudoplastics and depressed for dilatants compared to the situation for Newtonian fluids. Some preliminary experimental results in support of the analysis are presented.
Mass transfer without and with chemical reaction from single free gas bubbles
Authors: Ishii T. , Johnson A. I.
Published: March 2009

Rates of mass transfer of carbon dioxide bubbles into water and into monoethanolamine solutions are reported. The apparatus used located the free bubble in an inverted small angle funnel through which the continuous phase flowed. An appreciable wall effect was expected and was included in the analysis of the results by a concentric sphere potential flow model.
Axial dispersion coefficients in packed beds at low reynolds numbers
Authors: Urban Jack C. , Gomezplata A.
Published: March 2009

Peclet numbers describing axial dispersion in gas flow through packed beds of spheres were obtained using a two measurement point, pulse technique in a test section four inches inside diameter and 5.14 feet high. Three packing sizes were investigated, corresponding to tube to particle diameter ratios of 6.4, 17, and 66

In the experiments the contribution of the velocity profile to axial spreading was reduced by using thermal conductivity detectors which responded to dispersion only in the central part of the bed cross‐section. In this region of a packed bed the velocity profile is relatively flat. The results point to a particle diameter effect which is more pronounced than has been previously reported. This is in accord with the diffusive mechanism of axial dispersion in a packed bed provided dispersion caused by the velocity profile does not affect the measured pulse response.

In the absence of velocity profile effects, the spreading of residence times in void cells is caused primarily by the shedding of the decelerated boundary layers on the downstream side of the particles. At low velocities however, molecular diffusion predominates. Implicit in this discussion is the hypothesis that the uniformity of shape and size of packing particles has an important bearing on the manner in which the Peclet number approaches its limiting value as the gas velocity is increased.
The strength of agglomerates bound by salt bridges
Authors: Pietsch Wolfgang B.
Published: March 2009

The correlation between the drying behavior and the tensile strength of agglomerates bound by salt bridges in the dry state was investigated. The pellets examined had been prepared by compacting limestone powders, which were premoistened with a salt solution, in a manually operated die press. The percentage liquid saturation of the moist agglomerate, the concentration of the salt solution and the drying temperature were altered.

The influence of the surface incrustation on the drying process could be examined by measuring the temperatures within the cylindrical pellet at different radial positions during drying and by determining the drying rate curves. The tensile strength of the dried pellets, which was usually measured after removing the salt crust, depends on the quantity and the local distribution of the crystallized salt, and the strength of the salt bridges. The latter depends on the crystal structure which is influenced by the drying rate.
Viscosity prediction through extrapolation with the congruence principle
Authors: Coursey B. M. , Heric E. L.
Published: March 2009

Measured viscosities of mixtures of hexane and tetradecane are used to predict viscosities in three binary and one ternary system containing hexadecane. Predictions are based upon extrapolation, by means of the restricted congruence principle, of the excess Cibbs free energy of activation for flow. The errors in that function thereby range from 2.3 to 14.8 cal/mole for the several systems, and the corresponding errors in viscosity from 0.5 to 2.5%.
Enskog modulus, bρχ, for the gaseous and liquid states of carbon dioxide
Authors: Rosenbaum B. M. , Thodos George
Published: March 2009

The PVT behavior of carbon dioxide was used to establish a correlation for the Enskog modulus, bρχ in the dense gaseous and liquid regions. This modulus is presented for reduced temperatures ranging from TR = 0.90 up to TR = 3.5 and reduced pressures up to PR = 40.

The Enskog modulus finds use in the calculation of the effect of pressure on viscosity, thermal conductivity, and self‐diffusivity. The value of the Enskog modulus for carbon dioxide at the critical point has been calculated to be (bρχ)c = 0.885.
The dynamics of extraction processes: Part I. Introduction and critical review of previous work
Authors: Pollock G. G. , Johnson A. I.
Published: March 2009

A critical review and comparison of published work in the field of extraction dynamics is made. These studies of the transient behavior of liquid‐liquid extraction processes are summarized and evaluated. From these evaluations it is concluded that much work remains to be done for systems other than those involving simple extraction columns with terminal feeds and products, and also that pulse testing and frequency response analysis have become important tools for the determination of extraction dynamics. It was also concluded that staged models as opposed to differential contact models offer the most hope for realistic control and simulation studies.
The determination of theoretical frequency response of some stagewise processes
Authors: Pang K. H. , Johnson A. I.
Published: March 2009

The signal flowgraph and the matrix inversion methods for the determination of theoretical frequency response of some separation processes of interest to chemical engineers were described and compared with the difference operator (E) method. The application of these techniques to a 3‐and 5‐stage liquid‐liquid extraction column was demonstrated.

For the systems under study, the signal flowgraph method was found to be less time consuming and is therefore recommended for frequency response modeling for such devices.
The formation of uniformly sized drops by vibration‐atomization
Authors: Wissema J. G. , Davies G. A.
Published: March 2009

The effects of external vibrations on the disintegration of a liquid jet are described. Conditions for the formation of uniformly sized drops are discussed and results presented to illustrate the effect of amplitude and frequency of vibration on the drop size and break‐up length of the jet. Liquids of various viscosity have been studied, 60‐1400 c.p., and the results compared with existing theories.

This method can be used with standard pressure nozzles and may be of use in research experiments when dispersions of uniform drops are required. It also has application in the formation of uniform prills.
The longitudinal mixing of liquids flowing successively in pipelines
Authors: Aunicky Z.
Published: March 2009

In the case of two miscible liquids flowing successively in a single pipeline, a mixture of the two media is produced in the region of contact. Current theories for prediction of the volume of this mixture are not reliable. In this study the following matters are discussed: 1. The majority of previous results were reworked and presented in terms of a Taylor dispersion coefficientKand mixing width based onK(Table 1, 2); 2. This work proposes and tests new empirical correlations including the influence of the flow length on the growth of the value of the dispersion coefficientKas well as the influence of the Reynolds' number and concentration boundary upon the final volume of the mixtureVm(equations 6, 7, 9); 3. There are compared the predictions of various equations with our own experiments (Table 3) 4. It is pointed out that a Taylor type model is not completely satisfactory, since the dispersion coefficientKseems to increase with length of pipe and not stay constant. (Cmax∼ L−0.5 to −0.6instead ofCmax∼ L−0.5). The difference of exponents is a function of Reynolds number.
Mass transfer without and with chemical reaction in dispersed gas‐liquid two‐phase flows
Authors: Ishii Tsutomu , Johnson A. I.
Published: March 2009

Using a concentric sphere model, velocity profiles around bubbles in a bubble swarm were derived for clean and for relatively contaminated gas bubbles. The theoretical Sherwood numbers were calculated, including the effect of void fraction.

These mass transfer predictions were compared with experimental results for the absorption with reaction of carbon dioxide into monoethanolamine solutions. The results indicated an appreciable contamination of the bubbles by surface active material.
Hydrogen reduction of the chlorides of bi‐valent chromium and iron
Authors: Rigg Tyson
Published: March 2009

Previous work on the topochemical reduction of chromous and ferrous chlorides has been extended to include investigations carried out at elevated pressures. The kinetics are explained on the basis of heat and mass transfer processes involving vaporization of the metal chloride. Some of the problems encountered in the industrial application of these reactions are discussed.
The effect of mass transfer on selectivity for heterogeneous reactions
Authors: Harriott Peter
Published: March 2009

A simple model based on existing penetration theory solutions is proposed to predict the selectivity for consecutive reactions in gas‐liquid systems. The model is limited to cases of moderate to high selectivity, where the first reaction is much faster than the second. When the reaction greatly increases the mass transfer rate, the model gives about the same selectivity as the film theory, but predicts higher selectivities than the film theory when the enhancement factor ø is small and the reaction is rapid. When ø is small, an appreciable fraction of the gas that is absorbed reacts after surface elements are mixed with the bulk, and this contribution is neglected in the film theory. The model can also be applied to estimate the effect of diffusion on parallel reactions.
Poisoning studies in a single‐pellet catalytic reactor
Authors: Hahn Jeffery L. , Petersen Eugene E.
Published: March 2009

Using a novel reactor configuration, the nonuniformity of a poison in a single catalyst pellet was studied. The activity of an n‐alumina supported catalyst containing 0.25% platinum was measured using the cyclopropane hydrogenolysis reaction. The results show that the catalyst is progressively poisoned from the outside of the catalyst to the center plane nonuniformly. The data suggest a bimodal pore size distribution in the pellet.
Microcatalytic reactors: Kinetics and mechanisms with isotopic tracers
Authors: Galeski J. B. , Hightower Joe W.
Published: March 2009

Pulsed microcatalytic reactors have found extensive application in the petroleum and chemical industries where rapid catalyst screening and evaluation are demanded. Automated, continuous‐operation test units allow the accumulation of considerable amounts of data in a minimum of time. The technique is also useful in research where the small pulse size enables one to study “initial” interactions between surface and reactants. In this way, information about many kinetic parameters, such as intrinsic reaction rates, orders, poisoning effects, and catalyst deactivation, can be obtained. Both stable and radioactive isotopic tracers may be used economically in microcatalytic reactors to provide significant mechanistic information which cannot be obtained conveniently by other methods. For example, one can explore the chemical nature and number of active sites, as well as the fate of individual atoms and molecules as they interact with the catalyst. Although the technique may be applied to both “simple” and complex catalytic reaction systems, the discussion will be limited to a review of data obtained from (1) “unimolecular” reactions such as cyclopropane and butene isomerization and cumene dealkylation over the mixed oxides silica‐alumina, silica‐magnesia, and zeolites and (2) “bimolecular” reactions such as ethylene hydrogenation over alumina. Some of the limitations of microcatalytic reactors will also be given.
Generalised criteria for the stability of catalytic reactors
Authors: Mcgreavy C. , Thornton J. M.
Published: March 2009

It is well known that particles catalyzing highly exothermic reactions can have multiple steady states, which are characteristic of unstable behavior. Previous work has shown that under practical conditions the pellets are essentially isothermal, all the temperature rise being across the surrounding fluid film. A technique has been developed for such cases which enables the regions of potential local instability, if present, to be defined for arbitrary operating conditions. It is thus possible to monitor the calculation of concentration and temperature profiles in a fixed bed reactor to ascertain whether the conditions would represent multiple states and therefore non‐feasible operating conditions.
Development of a process for production of acetonitrile from acetic acid and ammonia
Authors: Tollefson Eric L. , Decker R. M. , Johnson C. B.
Published: March 2009

The development of a process for production of acetonitrile using a fluid bed, semi‐synthetic, silica‐alumina catalyst is described. The effects of reaction temperature and pressure, choice of catalyst, linear gas velocity and the mole ratio of reactants on the yield of acetonitrile from a pilot unit are given. Purification of the product is described. Some details concerning problems encountered in scaling up the process for commercial production are discussed. Experience gained from the operation of a commercial unit relating to the design of fluid bed reactors is summarized.
The motion of small air bubbles in stagnant and flowing water
Authors: Yip F. C. , Venart J. E. S. , Govier G. W.
Published: March 2009

The motion and interaction of small air bubbles rising vertically in stagnant and flowing water has been studied. Singlet, doublet and triplet bubble configurations with bubble generation frequencies of between 0.5 and 3.0 bubbles per second were used to examine the effects of radial and axial bubble interaction. The observed bubble flow behavior and subsequent analysis has allowed an identification of both the steady state and unsteady state (accelerating) regions. The critical separation distance, within which non‐steady state prevails, has been determined and the extrapolated limiting value for a Taylor bubble confirms the accepted value. Based on the experimental observations and the analysis, a prediction method to determine the details of bubble flow behavior within a limited range of the variables is proposed.
The measurement of interfacial area and surface‐renewal rate in a bubble‐cap plate
Authors: Mcneil K. M.
Published: March 2009

It is shown how interfacial area and surface‐renewal rate in a bubble‐cap plate can be determined from absorption‐rate measurements of CO2 into carbonate‐bicarbonate solutions in which the pseudo‐first‐order rate constant is varied by catalysis. A method of measuring the rate of constants of the experimental solutions is also described.
L'équation NRTL pour le calcul des équilibres liquide‐liquide à n‐constituants
Authors: Cohen C. , Renon H.
Published: March 2009

We propose a new method for the application of the NRTL equation(1) to the representation of phase equilibria, especially between two liquid phases, of multicomponent mixtures including polar substances; it is based on the determination of the parameters from the tie‐lines in ternary liquid‐liquid equilibria.

The advantage of this method is to give three parameters by pair of components, in agreement with binary phase equilibria, and to allow, without any additional parameter, the prediction of liquid‐liquid equilibria with more than three components.

Comparison of calculated and experimental data shows that the prediction of quaternary liquid‐liquid equilibria is good for the two systems found in the literature: cyclohexane, benzene, isooctane, furfural(2) and water, benzene, heptane, dimethylformamide(3).
Dynamic simulation of a stagewise mass transfer process with back‐mixing
Authors: Souhrada F. , Landau J. , Prochazka J.
Published: March 2009

A model is presented for studying the dynamic behavior of stagewise processes with non‐ideal stages and back‐mixing between them. By numerical integration on a computer, solutions have been obtained for two variants of the model: with a linear and non‐linear equilibrium relationship respectively. For the first variant an approximate relation was obtained for calculating the start‐up time. The analysis presented has been experimentally verified for a reciprocating‐plate extractor.
Particle velocities in a gas fluidized bed
Authors: Meissner H. P. , Kusik C. L.
Published: March 2009

A force acts on the walls of a fluidized bed container due to the collisions of the particles with these walls. A method is described for measuring this force, here called the particle pressure to distinguish it from the gas pressure. Using a model similar to the elementary kinetic theory of gases, an equation has been derived for calculating the average particle velocity from this particle pressure. Comparison shows the calculated velocities to be in fair agreement with reported measurements made photographically and with scintillation counters.
Longitudinal mixing in reciprocating and pulsed sieve‐plate column‐single phase flow
Authors: Novotny P. , Prochazka J. , Landau J.
Published: March 2009

Longitudinal mixing in reciprocating and pulsed sieve‐plate columns has been investigated for single‐phase flow and is described by a model in which both back‐mixing between stages and axial mixing within stages is considered. The model proposed expresses the effect of the amplitude, frequency, flow‐rates, distance between trays, their fractional free area and hole size on longitudinal mixing. The relations proposed have been verified by experiments, and the values of the constants in the correlation have been determined.
The correlation of axial dispersion data
Authors: Edwards M. F. , Richardson J. F.
Published: March 2009

The axial dispersion which occurs when a binary gas mixture flows through a bed of inert, non‐porous particles is well understood when the dispersion is dominated by either molecular diffusion or by turbulent mixing. In this paper consideration is given to the dispersion which occurs in the transition region between these two extremes of molecular diffusion and turbulent mixing. An equation for the prediction of the axial dispersion coefficient is discussed in the light of recent experimental evidence.
On motion of bubbles and drops
Authors: Gal‐Or Benjamin
Published: March 2009

Dynamically interacting effects of surfactant impurities and neighbor particles on the transfer mechanism of momentum and terminal velocities of spherical bubbles, drops, or solid particle assemblages at low Reynolds numbers are analysed and formulated. The steady‐state equations of viscous fluid motion and continuity (one set for each phase) have been solved simultaneously with a conservation equation for diffusing surfactant impurities. By employing a cell model with zero vorticity at its outer boundary, and modified interfacial conditions the terminal relative velocity of an ensemble of fluid particles is evaluated and compared with some available experimental data.

The analysis of solid‐fluid mixture is shown to become a special case of the analysis of fluid‐fluid mixtures where adventitious surfactant impurities stop internal circulation thereby causing drop and bubble assemblages to behave as suspension of solid particles.
Optimization of reactors with catalyst decay I — single tubular reactor with uniform temperature
Authors: Crowe C. M.
Published: March 2009

The optimal choice of temperature with time is sought so as to maximize the total amount of reaction in a fixed time in a tubular reactor with uniform temperature and decaying catalyst. The single reaction is assumed to be irreversible with a rate expressible as a product of separate functions of temperature, activity and conversion. The rate of decay of activity is also a product of separate functions of temperature and activity but independent of conversion.

To each total reaction time, there is a unique optimal policy. The policies are derived for various cases, distinguished by the ratio of activation energies for reaction and decay. Any optimal policy must end on the upper temperature constraint except for certain special cases. The stationary sub‐policy is shown to be one of constant conversion when the inlet conversion is constant. The stationary sub‐policy for a variable inlet conversion is also derived.

Numerical calculations are presented to illustrate the optimal policies and a comparison of the present results is made with those of previous workers.
The dynamics of extraction processes: Part IV. Frequency and time domain modeling of a mechanically agitated extractor
Authors: Pollock G. G. , Johnson A. I.
Published: March 2009

Frequency domain and time domain techniques have been used for the comparison of mathematical models of the transient behavior of a multistage extractor with experimenal data. In particular the sensitivity of the model to the number qf stages has been assessed. Several methods of model discrimination are compared.

It was found that an ideal mixing, non equilibrium stage model is both practical and realistic. The transient behavior of individual exit streams can be predicted well, although the model will not exactly predict both streams simultaneously.
A model for velocity and eddy diffusivity distributions in fully turbulent pipe flow
Authors: Travis J. R. , Buhr H. O. , Sesonske Alexander
Published: March 2009

A model was developed for the eddy diffusivity and mean velocity distributions in fully developed turbulent isothermal smooth pipe flow (4 × 103 < Re < 5 × 106). Reichardt's tworegion eddy diffusivity models were modified so as to fulfill the requirements that the eddy diffusivity be represented by a smooth, continuous curve, and vanish with the third power of the distance from the wall; the continuity equation be satisfied; and the ratio of the bulk velocity to centerline velocity agree with experimental data.

The descripition is in excellent agreement with Laufer's experimental mean velocity data and, in general, provides a method of accurately predicting the mean velocity distribution.
An experimental model for visual studies of turbulent flow in porous materials
Authors: Kyle C. R. , Perrine R. L.
Published: March 2009

A two‐dimensional experimental model has been developed to simulate turbulent flow in porous materials. It uses cross flow through a matrix of cylinders between parallel plexiglass plates. Matrix geometry was chosen to approximate a bed of packed spheres.

Pressure loss and axial dispersion in several models have been measured over a wide range of flow rates in the non‐Darcy region. Photographs have been taken of flow patterns developed in the transition from laminar to fully turbulent flow. All typical characteristics of flow through beds of packed spheres were exhibited; however, both pressure loss and dispersion differed somewhat when compared to similar three‐dimensional flow.
Condensation on a vertical rotating finned tube
Authors: Williams A. G. , Nandapurkar S. S. , Holland F. A.
Published: March 2009

Experiments have been carried out to determine the effect of centrifugal force on the rate of condensation of vapors. Methanol and isopropanol vapors were condensed on a vertical rotating finned tube and it was found that the data could be correlated by the equation:

Condensation film heat transfer coefficients in excess of 5,700 W/(m2 °K) and 4,200 W/(m2 °K) were obtained for methanol and isopropanol respectively at a tube rotational speed of 1,000 rpm.
Dynamics of cyclic fixed bed ion exchange an analysis based on a linear mass transfer model
Authors: Tan K. S. , Spinner I. H.
Published: March 2009

Solutions for fixed bed ion exchange based on a linear mass transfer model (linear isotherm and linear driving force rate equation) and general initial and boundary conditions are presented. The linear model solutions are applied to the study of the cyclic operation of fixed bed ion exchange and the equations describing both the transient and cyclic fixed bed processes for co‐current regeneration are derived. Examples which illustrate the simplicity of application of the analytical solutions are discussed.
Interpretation of chromatographic peaks by fourier analysis
Authors: Gangwal S. K. , Hudgins R. R. , Bryson A. W. , Silveston P. L.
Published: March 2009

Extraction of model parameters, such as kinetic rate coefficients, equilibrium constants and transport rate coefficients, may be obtained by determining the coefficients of the Fourier series which describe chromatographic peaks. Error buildup due to noise occurs slowly with successive harmonics in contrast to the rapid buildup in successive moments which make higher moments unreliable for extracting model parameters. Fourier analysis is applied to the simplest case of axial dispersion in a non‐porous, non‐adsorbing packing and to the important case of adsorption on a porous packing. Expressions for the Fourier coefficients, amplitude ratios and phase lags are derived for the axial dispersion case, the Kubin‐Kucera model for adsorption on a porous packing and, as well, for the case of axial dispersion and inter‐particle diffusion without adsorption.
Dynamics of convection heat exchangers
Authors: Heidemann R. A. , Huckaba C. E. , Eisen F. S. , Weissman L. I. , Gallatig G. M.
Published: March 2009

A mathematical model is developed for heat exchangers with condensing vapors on one side which includes the effects of variations in the local film heat transfer coefficients and allows for energy accumulation and conduction in the tube wall. A numerical integration scheme for the flow forced case is presented. The model is tested against experimental steady state and transient data for a steam‐water exchanger. It was necessary to modify the standard correlations of heat transfer coefficients to get a match of the overall steady state heat flux actually obtained in the apparatus. With these modified heat transfer coefficients, the model proved capable of predicting flow forced transients. These results are contrasted with transients predicted by a simple lumped parameters model employing empirically fit overall heat transfer coefficients. The lumped parameters model is shown quite adequate for predicting transient behavior under the specific conditions studied. The reasons for and limitations on the success of this very simple model are explored.
Expansion of a single gas bubble rising in a column of liquid
Authors: Weller K. R.
Published: March 2009

Measurements of the expansion behavior of single bubbles of an insoluble gas by monitoring the pressure change in a gas space at the top of a closed column show that the same expansion law applies both to the bubble and the gas space, but the correct expansion law cannot be deduced from pressure measurements alone. Results from a semi‐quantitative heat transfer experiment indicate that isothermal expansion should be assumed.
Friction factors in pulsed turbulent flow
Authors: Baird M. H. I. , Round G. F. , Cardenas J. N.
Published: March 2009

An apparatus for investigating pulsed turbulent liquid flow in a 2 in. diameter, 80 ft. pipeline is described. The pulsation unit was powered by compressed air with a consumption of up to 2.7 std. cu.ft./min. at 35 lb/in2 gauge. The pressure drop for water flowing at mean velocities of 7.66 to 12.28 ft./sec. has been measured, both for steady flow and for pulsed flow, at frequencies between 0.48 and 0.82 Hz. The experimentally measured pressure versus time curves for pulsed flow can be matched fairly closely by a solution of Euler's equation employing the friction factors measured under steady flow conditions.
Composition dependence of viscosity of some binary solutions
Authors: Ghai R. K. , Dullien F. A. L.
Published: March 2009

Viscosities of eleven binary liquid systems, mostly regular solutions, have been measured over the entire composition ranges at 25°C. Most of the systems had not been investigated before. The procedure, the precautions observed for the measurement of viscosity, and the calibration of the viscometers have been discussed. Of the many empirical and semi‐empirical equations tested for their validity the McAllister equation has been found to fit best the experimental data for all the solutions. Non‐ideality of a solution, as expressed in terms of excess activation energy for viscous flow or in terms of excess molal volume, has also been briefly discussed.
Regional stability for a tubular reactor with axial mixing
Authors: Wang F. S. , Perlmutter D. D.
Published: March 2009

A graphical phase‐plane procedure is suggested by which regions of stability can be estimated for a tubular reactor. The technique uses a super‐position of limits for primary flow and reaction effects and those arising from secondary axial dispersion. Several detailed numerical tests are reported to substantiate the conjecture.
Transport of solids by gas‐liquid mixtures in horizontal pipes
Authors: Scott D. S. , Rao P. K.
Published: March 2009

Two sizes of particles of 500μ and 100μ mean diameter were conveyed as water slurries through 1 inch and 2 inch horizontal pipelines. Pressure drops and saltation velocities were measured over a range of slurry concentrations to 14% by volume with and without concurrently flowing air. In the former case, the principal flow patterns studied were in the bubble and plug flow regimes. Although small effects on saltation point were noted due to the induced turbulence from the air bubbles, these were not significant, and a reasonable estimate of saltation velocities could be made from Durand's correlation. Pressure drops were found to be correlated reasonably well by modified Lockhart‐Martinelli parameters as used for turbulent‐turbulent horizontal gas‐liquid flow except at conditions near the saltation point. Pressure drops for slurry flow alone were predicted reasonably well by the modified Durand equation.
Theoretical interpretation of gas oil conversion data on an x‐sieve catalyst
Authors: Pachovsky R. A. , Wojciechowski B. W.
Published: March 2009

A four parameter model based on the catalyst aging theory of Wojciechowski(5) is applied to experimental conversion data in gas oil cracking. The data extends over a range of cat/oil ratios from 0.094 to 3.0, and run times from 1.25 to 40 minutes. Within this range of conditions the model is applied to data with and without thermal conversion and excellent correlation between experimental results and calculated values is obtained. The technique for fitting data to the model is described in some detail.
Modeling and parametric studies of a vapour recompression distillation system
Authors: Menzies M. A. , Johnson A. I.
Published: March 2009

A vapor recompression system for the separation of ethylene from a multicomponent feed has been modeled using the CHESS program and based on data from the Polymer Corporation. The experience in implementing CHESS on a CDC6400, and in using its property calculation features are reviewed. The modification of the CHESS modules, and new unit computations required for the study are described. Some typical applications of the model to seek improvements in plant operation are discussed.
Motion of entrained particles in gas streams
Authors: Clift R. , Gauvin W. H.
Published: March 2009

Recent work on the drag experienced by an entrained particle in relative motion through a fluid is reviewed. It is shown that fluid turbulence, acceleration, particle shape and orientation, and particle‐fluid mass transfer can all have a significant effect on the value of the drag force, particularly when the non‐idealities cause a change in the flow pattern around the particle. Conditions under which the drag force can be predicted with certainty are still very limited, and some potentially valuable directions for future research are suggested.
Internal age and residence time distributions of a fluid in non‐ideal stirred tanks in series
Authors: Chiang David , Cholette A.
Published: March 2009

The internal age distribution of a fluid, for p imperfectly mixed vessels in series, is presented and interpreted in the light of the laws of probabilities.

An expression is presented for the residence time distribution. Five graphs show the variation of this expression as a function of the reduced effective time, each graph being characterized by a given degree of channeling. The curves, similar to those for the dispersion model, indicate that the model can represent mixing conditions extending all the way from an imperfectly mixed reservoir to plug flow.

An expression is also presented for the mean residence time.
Prediction of excess free energies of liquid mixtures containing aromatic hydrocarbons using a group solution model
Authors: Maripuri V. C. , Ratcliff G. A.
Published: March 2009

The group solution model of Ratcliff and Chao for the excess free energies of liquid mixtures has been tested and found satisfactory for six mixtures of alcohols and aromatic hydrocarbons. The model was tested by comparing experimental and predicted vapor‐liquid equilibrium data.

The assumption that aliphatic and aromatic carbon atoms are equivalent appears satisfactory for the mixtures considered. Group contribution functions were generated from experimental data on ethanol/benzene mixtures at 45°C, and are presented. These functions allow the prediction of excess free energies of mixtures containing alcohols and aromatic hydrocarbons at 45°C. No experimental data is required. Predictions at temperatures close to 45°C, using the same functions, should be satisfactory.

The group contribution functions were close to those generated previously from alcohol/alkane data. The latter may be used for predicting excess free energies of alcohol/aromatic hydrocarbon mixtures with little loss of accuracy.