bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vapor‐liquid equilibrium calculations for concentrated polymer solutions
Authors: Bonner D. C. , Prausnitz J. M. 
Published: June 2004

AbstractThe free‐volume theory of polymer solutions initiated by Prigogine and developed by Flory and Patterson is reduced to practice. This theory, which represents a substantial improvement over the older theory of Flory and Huggins, facilitates calculation of solvent activities in polymer solutions from a minimum of experimental binary data. However, it is necessary to characterize each pure component with three molecular parameters which can be obtained from PVT data; such data, unfortunately, are often unavailable. Nevertheless, using reasonable approximations based on Bondi's correlations as needed, molecular parameters are given for 22 solvents and for 16 polymers. Binary parameters are given for 20 systems. Illustrative examples are presented.
Optimization of parallel reactions in a tubular reactor by feed distribution
Authors: Delbridge H. T. , Dyson D. C. 
Published: June 2004

AbstractThe System of isothermal, isobaric, perfect gas reactions with stoichiometric kinetics

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taking place in a tubular reactor is considered where A3 is desired and A5 undesired. A class of optimum selectivity problems is formulated, and distributed bypass of A1 is investigated. It is shown that there are cases where the performance of the best plug flow reactor can be improved substantially (sometimes by more than 100%) by the bypass of A1, but there are also cases where bypass is fruitless.
Secondary nucleation of magnesium sulfate by fluid shear
Authors: Sung C. Y. , Estrin J. , Youngquist G. R. 
Published: June 2004

AbstractThe secondary nucleation of magnesium sulfate due to the action of fluid forces on a seed crystal was studied by introducing the hypothesized nuclei so generated into a region of high supersaturation. The number of nuclei observed is strongly dependent on the supersaturation at the seed and the severity of shear forces. Classical nucleation theory is used to interpret the results. These results are consistent with other experimental observations described in the recent literature on contact nucleation. The growth and nucleation process inferred is similar to that illustrated by Clontz and McCabe (1972) and suggested by Knight (1971).
Combined forced and free convection flow past a horizontal flat plate
Authors: Robertson G. E. , Seinfeld J. H. , Leal L. G. 
Published: June 2004

AbstractThe problem of simultaneous forced and free convection flow of a Newtonian fluid past a hot or cold horizontal flat plate is investigated by means of numerical solutions of the full equations of motion and thermal energy subject only to the Boussinesq approximation. These solutions span the parameter ranges 10 ≤Re≤ 100, 0.1 ≤Pr≤ 10, and –2.215 ≤Gr/Re5/2≤ 2.215 whereRe,Pr, andGrare based on the ambient free stream fluid properties and the overall plate lengthl. WhenGr> 0, the boundary flow near the plate surface is accelerated relative to the corresponding forced convection flow, with a resulting increase in both the local skin friction and heat transfer coefficients. WhenGr< 0, the boundary flow is decelerated, the local skin friction and heat transfer are decreased, and the flow actually separates forGr/Re5/2< –0.8 whenPr= 0.7. In the latter circumstance, an increasing degree of upstream influence is observed asGr/Re5/2is further decreased.
Application of conformational analysis techniques to the prediction of heats of formation and gas‐phase thermodynamic functions
Authors: Boyd R. H. , Breitling S. M. , Mansfield M. 
Published: June 2004

AbstractConformational energy calculations based on describing the deformation of chemical bonds by energy functions allow the prediction of molecular geometries, heats of formation, vibrational frequencies, and gas‐phase thermodynamic functions of compounds which contain bonds or groups of bonds whose properties are transferable from molecule to molecule.
On the use of Crocco's equation for the flow of power‐law fluids in a transverse magnetic field
Authors: Djukic Djordje S. 
Published: June 2004

AbstractThe steady laminar boundary layer flow past two‐dimensional surfaces of a power‐law non‐Newtonian electrically conducting fluid in a transverse external magnetic field is studied. The Crocco boundary layer equation is presented and, for the flow over a flat plate, solved approximately by the use of the integral method. Three examples are studied in detail. The transverse magnetic field has a greater influence on the flow of a dilatant fluid than for a pseudo plastic fluid. Increasing the magnetic field strength increases the shear stress coefficient.
Topics in computer‐aided design: Part II. Synthesis of optimal heat exchanger networks by tree searching algorithms
Authors: Pho T. K. , Lapidus L. 
Published: June 2004

AbstractA compact matrix representation of an acyclic exchanger network is derived and used to generate a decision tree for the heat exchanger problem. The optimal network, which is imbedded in one of the tree nodes, is located by enumerating the entire tree using a search procedure. When this is not feasible, an alternate partial enumeration method is suggested. Sample problems ranging in size from 4 to 10 streams are used to illustrate the methods.
Measurement of mutual diffusion coefficients and thermal diffusivities by quasi‐elastic light scattering
Authors: Gulari Erdogan , Brown Ronald J. , Pings C. J. 
Published: June 2004

AbstractQuasi‐elastic light scattering techniques have been employed to measure the mutual diffusion coefficient DAB as a function of concentration in eight binary mixtures and the thermal diffusivity x in nine pure liquids and two binary mixtures. The mass diffusivities obtained are typically accurate to 3% while thermal diffusivities are known to be accurate to 5%; both types of values are in substantial agreement with the available bulk values. Under most circumstances light scattering is found to offer distinct advantages over the standard techniques for determining mass and thermal diffusivities.
Liquid phase mass transfer with concurrent flow through packed towers
Authors: Ufford Raymond C. , Perona Joseph J. 
Published: June 2004

AbstractLiquid phase mass transfer coefficients were measured for the absorption of carbon dioxide into water in concurrent flow. Liquid flow rates ranged up to 300 kg‐mol/min. m2 or about 60,000 lb./hr. ft.2. In comparison with countercurrent flow, the coefficients were lower by as much as a factor of 3 with significant gas rate effect. Correlations for concurrent coefficients with liquid and gas flow rates were obtained in the form kxa = CLrGs for 19.0‐mm Berl saddles and 6.35‐mm and 12.7‐mm Rashig rings.
Solubilities of gases in water and other associated solvents
Authors: Hayduk Walter , Laudie Harry 
Published: June 2004

AbstractA method for estimating the effect of hydrogen‐bonding on gas solubilities in polar solvents is presented. H‐bonding factors, which are based on ideal gas solubilities and solubilities in water, appear to be closely related to H‐bonding factors in the simple alcohols. Similarly, H‐bonding factors in solvents containing a carbonly group or dihydroxy groups were related to those in acetone. The relation between the various H‐bonding factors can be used to estimate solubilities in these and other associated solvents.
Prediction of variable process performance by stochastic flow sheet simulation
Authors: Gaddy J. L. , Culberson Oran L. 
Published: June 2004

AbstractThe method of stochastic (Monte Carlo) simulation is employed to determine variable process performance of a 545 Mg/d ammonia plant. Operating conditions and equipment reliability are varied in a flow sheet simulation model of the process. Probability distributions of the plant production capability and failure times are generated. These data agree closely with the operating experience of an actual ammonia plant.
Liquid diffusion of nonelectrolytes: Part II
Authors: Ertl H. , Ghai R. K. , Dullien F. A. L. 
Published: June 2004

AbstractPart II of the review paper covers the self‐diffusion theories and their comparison with experimental results. This is followed by a review of empirical and semi‐empirical predictive equations of mutual and self‐diffusion coefficients. Recent developments in experimental techniques for measuring liquid diffusivities are discussed in the last section. A supplement of experimental diffusion data since 1956 is available.
Intraparticle mass transport in slurries by dynamic adsorption studies
Authors: Furusawa Takehiko , Smith J. M. 
Published: June 2004

AbstractRates were measured at 25°C for the adsorption of benzaldehyde from an aqueous solution into particles of Amberlite, or activated carbon, suspended in the solution. The data for monodisperse, Amberlite particles (mean pore radius = 50Å) showed significant intraparticle diffusion resistance over the entire particle size range 200 to 900 microns (diameter). Intraparticle diffusivities were larger (tortuosity factor ∼ 0.35) than expected from pore‐volume diffusion in the liquid‐filled pores.For the activated carbon particles (of the same size) which have a bidisperse pore‐volume distribution (pore diameter range 15 to 104Å), the effect of intraparticle diffusion was much less important and separation of the external diffusion resistance to obtain a precise value of the intraparticle diffusivity was not possible. However, De values are larger than for Amberlite and much greater than the molecular diffusivity of benzaldehyde in liquid‐filled pores. The unusually high intraparticle diffusivity seems most likely to be due to interpreting dynamic adsorption data for a bidisperse porous particle with a theory involving but one diffusivity.
Salt effects on vapor‐liquid equilibrium: Some anomalies
Authors: Meranda David , Furter William F. 
Published: June 2004

AbstractExperimental data are presented for five systems, each consisting of water, an alcohol (methanol or ethanol), and an inorganic salt dissolved to saturation in the boiling liquid phase. The data confirm and extend knowledge of recently discovered anomalies to the general theory of salt effect in vapor‐liquid equilibrium. A partial accounting for the observed anomalies is attempted based on recent advances in the understanding of the structural nature of alcohol‐water mixtures.
Turbulent drag reduction in polymeric solutions containing suspended fibers
Authors: Lee W. K. , Vaseleski R. C. , Metzner A. B. 
Published: June 2004

AbstractBoth polymeric solutions and fiber suspensions have separately been known to exhibit drag reduction under turbulent flow conditions. It has recently been shown that the mechanisms of drag reduction differ appreciably in these two kinds of systems.The objective of this study was to show that both mechanisms may be exploited concomitantly to achieve unusually low friction factors. Drag reductions in excess of 95% have been obtained in a 2.4‐cm tube and there is no evidence that even more dramatic results could not be obtained under optimal conditions.
New methods for suboptimal feedback control of parabolic systems
Authors: Vermeychuk J. Gregory 
Published: June 2004

AbstractA new class of algorithms for the suboptimal feedback control of parabolic systems is presented. Three specific techniques within this class are developed and tested numerically using a linear example with three different types of boundary conditions. Performance of two of these techniques is found to compare favorably with that obtained by use of a rigorous open‐loop optimal control computed by the gradient method. It is also shown for linear systems having quadratic performance criteria that the new algorithms are superior to the technique presented by Vermeychuk and Lapidus (1973) in cases where state deviation has a weighting coefficient much greater than that for control energy.
Turbulent flow and mass transfer on a rotating hemispherical electrode
Authors: Chin Der‐Tau 
Published: June 2004

AbstractUsing the Karman‐Pohlhausen integral method, an analysis has been made for turbulent flow on a rotating hemispherical electrode mounted on an inert support rod of equal radius. The resulting friction coefficient is then substituted into the Chilton‐Colburn relation to give a rate equation for mass transfer at high Schmidt numbers. Experiments with a diffusion‐controlled electrolytic system over a range of Sc from 910 to 6,300 confirm the validity of the theory for Re > 40,000. A comparison with the results of previous heat and mass transfer measurements reveals that the turbulent flow on the present geometry is different from that on a rotating sphere and on a hemispherical electrode mounted on a support rod of larger radius.
Thermodynamic properties of sea salt solutions
Authors: Bromley Leroy A. , Singh Daljit , Ray Parthasarathi , Sridhar Srinivasan , Read Stanley M. 
Published: June 2004

AbstractBased on new experimental data presented for the boiling point elevation of natural sea water solutions, smoothed tabular values are presented for boiling point elevation (BPE), osmotic coefficient, water activity, osmotic pressure, and minimum separation energy to 200°C and 12% sea salt.The concentration of sodium chloride solutions having the same water activities as sea salt solutions is also presented.Rigorous thermodynamics and the equations for strong electrolytes by Bromley (1973) were used for the correlation together with previously obtained heat capacity and enthalpy data and equations. A simplified equation is presented for boiling point elevation.
Scale‐up of agitated vessels gas‐liquid mass transfer
Authors: Miller Donald N. 
Published: June 2004

AbstractProcedures are developed for predicting liquid film controlled mass transfer in gas sparged contactors with and without mechanical agitation. Mass transfer is shown to depend on mean bubble size. Bubble shape, motion, and interface fluctuations are all properties that are associated with bubble size, which, in turn, can be determined from the physical characteristics of the contacting system.Experimental measurements were made on CO2 stripping from aqueous solution with air in 0.00252, 0.0252, and 0.252 m3 tanks. The vessels were geometrically similar, fully baffled, and equipped with four flat‐blade impellers and spargers. These measurements are used to evaluate earlier correlations and to develop improved scale‐up procedures.
Effect of cavitation on reacting systems
Authors: Couppis Evis C. , Klinzing George E. 
Published: June 2004

AbstractWhen ultrasound is applied to a liquid reacting system, the reaction rates are often increased. The application of ultrasonics, therefore, provides additional modes of accelerating the reaction rates which are usually not considered by conventional mechanisms. In an attempt to study the effect of ultrasonics on chemical reactions, experimental work was undertaken in which the reaction rates of the hydrolysis of methyl acetate were measured under the presence of ultrasound. The temperature, the vapor pressure with in the cavitating bubbles, the resonance characteristics, the volume of the reacting system, and the intensity and frequency of the ultrasound are all influencing parameters on the reaction rates.
Effect of phase‐volume ratio and phase‐inversion on viscosity of microemulsions and liquid crystals
Authors: Falco J. W. , Walker R. D. , Shah D. O. 
Published: June 2004

AbstractMicroemulsions, which are optically transparent oil‐water dispersions, were spontaneously produced upon mixing hexadecane, hexanol, potassium oleate, and water in specific proportions. The viscosity of the microemulsions was measured for several water/oil ratios including the phase‐inversion region. The striking optical and viscosity changes observed at specific water/oil ratios were in agreement with the proposed mechanism of phase‐inversion, namely, water spheres → water cylinders → water lammellae → continuous water phase, for this system. In the phase‐inversion region, the dispersion exhibited birefringence and rheopectic properties. An extremely high viscosity (> 100,000 cps) exhibited by the dispersions between water/oil ratios of 2.0 and 3.5 were explained in terms of ion‐dipole association between oleate and hexanol molecules on adjacent droplets.
Causes, magnitude, and effects of temperature fluctuations (flickering) of catalytic wires and gauzes
Authors: Edwards W. M. , Zuniga‐Chaves J. E. , Worley F. L. , Luss Dan 
Published: June 2004

AbstractAn experimental study has confirmed a theoretical prediction that, when an exothermic mass transfer limited chemical reaction occurs on a single catalytic wire for which the parametera[Equation (11)] is large, temperature fluctuations (flickering) of large amplitude must be induced by concentration fluctuations. A simplified model is presented for predicting the magnitude of flickering in industrial convertors for which the parameterais usually large. The model should be useful in estimating the influence of improved mixing of the reactants on the reduction in precious metal loss from the gauze.
Facilitated transport via carrier—mediated diffusion in membranes: Part II. Mathematical aspects and analyses
Authors: Goddard Joe D. , Schultz Jerome S. , Suchdeo Shyam R. 
Published: June 2004

AbstractPart II of this review is concerned with the mathematical analysis of facilitated transport. An exposition is given of the most generally useful techniques for obtaining asymptotic or approximate solutions to one‐dimensional carrier‐mediated diffusion in membranes, involving multiple permeant and carrier species which undergo one or more chemical reactions. Primary emphasis is devoted to the limiting regimes of weakly‐perturbed membranes (small driving forces) and slow or fast reactions (small or large Damkohler numbers). Many of the results appearing in the literature are unified and extended, and a systematic procedure for using these to estimate membrane performance is put forth. Finally, some areas for further work are identified.
Effect of nonuniform velocity fields and retrograde flow on distillation tray efficiency
Authors: Bell Richard L. , Solari Rodolfo B. 
Published: June 2004

AbstractThe effect of nonuniform velocity distributions and retrograde flow on Murphree tray efficiency has been studied. Both types of nonuniformities were shown to substantially reduce the efficiency of the tray. The results show that the presence of flow nonuniformity alone may result in significant deviations from the efficiency predicted by the AIChE model.
Statistical characteristics of thin, wavy films: Part II. Studies of the substrate and its wave structure
Authors: Chu K. J. , Dukler A. E. 
Published: June 2004

AbstractWaves on falling liquid film display certain random features. At least two classes of such random waves are shown to exist; large waves which carry the bulk of the fluid and small waves which cover a substrate film that exists between large waves. It is shown that the statistics of the substrate thicknes and its wave structure can be extracted from measurements of the variation of film thickness with time. A theory is presented for calculating the mean substrate thickness and the substrate flow rate. The statistics of the wave structure is presented and compared with existing theory. The importance of the substrate in controlling transfer processes is demonstrated.
Optimal temperature policy for reversible reactions with deactivation: Applied to enzyme reactors
Authors: Haas Willard R. , Tavlarides Lawrence L. , Wnek Walter J. 
Published: June 2004

AbstractThe optimal temperature policy which will maximize the final catalyst activity that gives a fixed conversion of reactants in a specified time for batch operation was determined by the formulation of a calculus of variations problem following the technique of Szepé and Levenspiel (1968). The method was applied to the general case of first‐order reversible reactions which occur in the presence of catalysts deactivating by an irreversible first‐order mechanism. To reduce trial and error estimations and circumvent numerical instabilities, the two‐point boundary value variational problem was reformulated in terms of an initial value problem with a parameter which includes the initial value of temperature. This initial value problem was solved by a regression technique.These techniques were applied to the industrially important enzymatic reaction of the isomerization of D‐glucose to D‐fructose catalyzed by glucose isomerase in solution. Kinetic and deactivation data are available for this endothermic reaction which obeys first‐order reversible kinetics and for the isomerase denaturation which appears to be first order. The optimal temperature operational policy as stated above maximized final enzyme activity such that 10% less denaturation of glucose isomerase occurred when compared to final isomerase activity yielding the same conversion for the same reaction time when the reactor is operated at the optimal isothermal temperature.
Chromatographic investigation of the oxygen exchange reaction between carbon monoxide and carbon dioxide
Authors: Smith W. D. , Deans H. A. 
Published: June 2004

AbstractThe theory of perturbation chromatography and isotopic tracers has been applied to the investigation of the oxygen exchange reaction between carbon monoxide and carbon dioxide in the presence of a copper‐zinc oxide catalyst at 205°C and atmospheric pressure. By analyzing the retention times of carbon‐14 monoxide and carbon‐14 dioxide tracers in six binary carbon monoxide/carbon dioxide carrier gas streams, it has been possible to shed light on the mechanism of the exchange reaction. Two types of carbon monoxide adsorption and two types of carbon dioxide adsorption were identified. Based on a numerical simulation of the experimental data, it has been concluded that the exchange reaction proceeds via the dissociative adsorption of carbon dioxide. Furthermore, the surface oxygen species formed during the dissociative adsorption of carbon dioxide appears to be the active site for the exchange reaction.
Viscous dissipation in die flows
Authors: Cox Howard W. , Macosko Christopher W. 
Published: June 2004

AbstractThe flow of polymer melts in cylindrical, annular, and slit dies has been examined. Large temperature rises at the outer surface of the extrudate were measured with an infrared pyrometer. Calculations show that severe radial temperature gradients exist in these flow geometries under conditions similar to those encontered in polymer processing and in viscometry measurements. A common method of estimating the average temperature rise from the total mechanical energy input seriously underestimates the maximum temperature rise.A numerical solution of the flow and energy equations models the flow in all three geometries. A very simple Nusselt number correlation allowed an estimate of the temperature rises possible if heat transfer with the die wall occurrs. Good agreement was obtained between predicted and infrared measured melt surface temperature rises. The pressure drop gives only an indication that nonisothermal flow is occuring and is not sensitive enough to distinguish the type of heat transfer boundary condition present.The mathematical model presented could be helpful in die design and in process modeling, allowing the designer to obtain some knowledge of the kind of flow situations which might be encountered.
Kinetics of ice crystallization in sugar solutions and fruit juices
Authors: Omran A. Monem , King C. Judson 
Published: June 2004

AbstractIce‐crystal secondary nucleation kinetics are derived from thermal response experiments carried out with concentrated sugar solutions and fruit juices. Variables studied include the level of supersaturation, power input, sugar concentration, sugar type, and the presence of high‐molecular‐weight additives. The nucleation rate is indicated to have a low‐order dependence upon subcooling (about 1.25 power) for subcoolings in the range 0.25 to 1.00°C. Fruit juices are well modeled by the corresponding synthetic sugar solution. The selection and improvement of processing approaches for freeze concentration of food liquids are discussed in light of the experimental results.