bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sonochemical cavitation phenomena in small bubbles
Authors: Fogler Scott 
Published: March 2009

AbstractA 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

AbstractThe 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

AbstractRates 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

AbstractPeclet 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 66In 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

AbstractThe 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

AbstractMeasured 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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractThe 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

AbstractIn 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

AbstractUsing 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

AbstractPrevious 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

AbstractA 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

AbstractUsing 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

AbstractPulsed 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

AbstractIt 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

AbstractThe 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

AbstractThe 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

AbstractIt 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

AbstractWe 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

AbstractA 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

AbstractA 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

AbstractLongitudinal 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

AbstractThe 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

AbstractDynamically 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

AbstractThe 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

AbstractFrequency 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

AbstractA 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.