bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unsteady diffusion with first‐order reaction
Authors: Lightfoot E. N. 
Published: June 2004

AbstractOutline below is a method for simplification of the solution of diffusion problems involving irreversible first‐order reactions. It permits writing the concentration profiles for reactive systems in terms of those for nonreactive systems of the same geometry and similar boundary conditions. The method is valid where fluid flow patterns and concentration boundary conditions are time independent and where the assumptions of constant density and mass diffusivity are acceptable. The useful results of this development are summarized in Equations (31) through (33) and represent a generalization of an earlier development by P. V. Danckwerts (1).
Semibatch operation of a recirculation reactor for the hydrogenation of ethylene
Authors: Leinroth J. P. , Sherwood T. K. 
Published: June 2004

AbstractThe purpose of this study was to develop the use of semibatch operation of a recirculation reactor in kinetic studies. Ethylene hydrogenation over a supported copper catalyst was studied experimentally. In semibatch operation one of the reactants is fed at the rate necessary to hold the total pressure in the reactor constant. In ethvlene hydrogenation the reaction rate is directly equal to the feed rate, and the kinetics can be studied at constant partial pressure of either of the reactants. Since ethane is inert, this technique permitted the study of reaction rate as a function of one variable at a time.Although ethylene hydrogenation has been studied extensively, there is not general agreement regarding the kinetics over a copper catalyst. The results are themselves of interest because they indicate the reasons for the apparently conflicting data in the literature.
Statistical surface thermodynamics of simple liquid mixtures
Authors: Eckert C. A. , Prausnitz J. M. 
Published: June 2004

AbstractThe surface properties of nonpolar liquid mixtures are derived from the application of the grand partition function to a cell model of the vapor‐liquid interface. The surface tension and surface composition are expressed in terms of the activity coefficients in the bulk liquid and pure‐component properties. The results are in excellent agreement with existing data for the surface tension of mixtures. This treatment provides a sound theoretical basis for the prediction of surface properties of other liquid systems and is especially applicable to cryogenic mixtures.
An analysis of the equilibrium stage separations problem—formulation and convergence
Authors: Friday John R. , Smith Buford D. 
Published: June 2004

AbstractThe formulation of a solution method for the equilibrium stage model equations involves six major decisions. Each of these decisions is analyzed and the proper choices indicated. One major contribution of the analysis was a clearer understanding of why any one solution method is not convergent on both distillation and absorber types of problems. A correct solution method is formulated for absorption and extraction problems. This method when programed in parallel with a distillation method works all but a few unusual problems with a minimum of computer time. Another contribution was the development of a procedure for solving the concentration or component rate matrix equations which avoids the computational difficulties of the Lewis‐Matheson and Thiele‐Geddes methods; that is the procedure avoids truncation error build up, does not require mesh points, works equally well for any number of feeds and side streams, and handles nondistributed components in the same way as distributed ones.
Velocity profiles of thoria suspensions in turbulent pipe flow
Authors: Eissenberg D. M. , Bogue D. C. 
Published: June 2004

AbstractVelocity profiles and friction factors of non‐Newtonian fluids in turbulent pipe flow can be displayed with the semiempirical forms developed for Newtonian fluids in which the apparent viscosity evaluated at the wall shear stress is used.Friction factors and velocity profiles were obtained for a dilute and a concentration aqueous thoria suspension and compared with the Newtonian correlations and with previous data obtained from widely different non‐Newtonian fluids including a viscoelastic fluid. A relationship is shown between the decrease of the friction factor and the change in the velocity distribution towards a more laminar profile.A generalized method of deriving the friction factor‐Reynolds number plot from the velocity profile based on the von Kármán relationship for Newtonian fluids is derived and compared with the data.
Turbulence energy and intensity spectra in a baffled, stirred vessel
Authors: Kim W. J. , Manning F. S. 
Published: June 2004

AbstractThe radial components of the turbulence energy and intensity spectra within a stirred, baffled tank are measured with a transducer probe of the type developed by Eagleson et al. (9). The spectra are normalized because absolute levels of the intensity in these high intensity velocity fields cannot be measured with the present technique. Average velocities are also measured with Pitot and Prandtl tubes.Range of measured energy and intensity spectra was 19 to 1,100 cycles/sec. The measured energy spectra show a k−5/3‐relation in the low wave number range where the wave number k is less than 100 ft.−1 and a k−10/3‐relation in the wave number range of 100 to 1,000 ft.−1. This behavior is found regardless of impeller size, motor speed, and position in tank, in particular radial distance, indicating that the decay of energy spectra is self‐preserving. Increasing the viscosity from 0.80 to 103 centipoises results in a progressively steeper slope in the high wave number range. The shape of the intensity spectra is the same as that of the concentration spectra measured by Manning (26, 27).
Kinetics of sulfochlorination of cyclohexane in carbon tetrachloride induced by gamma radiation
Authors: Schneider Alfred , Chu Ju Chin 
Published: June 2004

AbstractSolutions of cyclohexane, chlorine, and sulfur dioxide in carbon tetrachloride were irradiated in an oxygen‐free system with gamma rays from uranium fission products contained in spent fuel elements. Reaction rates, equivalent to the rate of disappearance of free chlorine, were determined spectrophotometrically at 4,000Å. The reaction products were cyclohexanesulfonyl chloride and hydrochloric acid in nearly stoichiometric quantities. An empirical rate equation was derived, in which the rate of disappearance of chlorine was shown to be proportional to the square root of the product of the product of absorbed radiation, chlorine and cyclohexane concentrations, and independent of the concentration of sulfur dioxide. A chain mechanism was proposed, and the rate equation derived from this scheme was found to be in excellent agreement with the empirical rate equation. The reaction proceeded by a free radical mechanism, as evidenced by the strong inhibiting effect of oxygen. G numbers were of the order of 105, corresponding to an estimated chain length of 5,000, which is of the same order as the quantum yield of the photochemical sulfochlorination.
Dynamic optimization of a two‐stage reactor system
Authors: Thibodeau Robert D. , Stevens William F. 
Published: June 2004

AbstractWith the development of relatively inexpensive control computers and on‐stream analyzers, on‐line dynamic optimization of nonlinear, multistage systems has become more feasible. Investigators have been concerned with the static optimization and control of single‐stage and multistage systems, but few have considered the optimization of a multistage system whose behavior is nonstatic owing to stochastic changes in its input and environment, and whose optimal control policy is time varying.This paper looks at the problem of dynamic optimization as it applies to the analysis of a multistage continuous stirred‐tank reactor system. A variational approach, in which the physical restraints on the manipulatable variables are included by a parametric representation, led to a bang‐bang, sampled‐data, optimal control law, or an equivalent analytical expression for continuous optimal control. Inclusion of the inequality relationships, specifying amplitude constraints on the manipulatable variables by a penalty function, resulted in a set of nonlinear Euler‐Lagrange equations specifying the control law.
A study of interstitial liquid flow in foam. Part I. Theoretical model and application to foam fractionation
Authors: Leonard Ralph A. , Lemlich Robert 
Published: June 2004

AbstractA theoretical model for interstitial liquid flow in a stationary or moving foam was devised by relating the physical structure of the foam to the physical properties of the surfactant and the foam movement. This was accomplished through a differential momentum balance within a typical capillary (Plateau border) of noncircular cross section with finite surface viscosity at its boundaries. Velocity profiles were then calculated and integrated numerically for the randomly oriented capillaries so as to obtain the overall liquid flow through the foam in terms of the pertinent variables. Results are presented in a form suitable for estimating concentrations and flow rates of product and waste streams in foam fractionation.
Some molecular transport characteristics in binary homogeneous systems
Authors: Longwell P. A. , Sage B. H. 
Published: June 2004

AbstractThe behaviors of several diffusion coefficients are shown for the methane‐n‐butane system under conditions such that solutions are very nonideal and the concentrations of both components are significant. The coefficient proposed by Chapman and Cowling shows the least variation with state and is recommended for use under such conditions in hydrocarbon systems. Several other coefficients commonly used show large variations with state and coefficients using concentrations as a potential are even negative in certain regions.
Mass transfer in a sparged contactor: Part I. Physical mechanisms and controlling parameters
Authors: Braulick W. J. , Fair J. R. , Lerner B. J. 
Published: June 2004

AbstractStudies of the air oxidation of aquoeus sodium sulfite solutions were made in simple bubble contacting columns of 3‐, 4‐, and 6‐in. diameter. Superficial gas rates up to 300 lb./hr.‐sq.ft. were used. Contacting action is described in detail, and comparisons with air‐water data show the marked influence of small, ionic bubbles. Mass transfer and dynamic gas holdup data are presented, and the former are compared with mass transfer data for bubble‐cap trays.
On the stability of a detailed packed‐bed reactor
Authors: McGuire M. L. , Lapidus Leon 
Published: June 2004

AbstractAn analysis of the stability of a packed‐bed reactor is presented subject to a model including axial and radial gradients in the interparticle field and gradients plus reaction in the intraparticle field. The stability of the entire reactor is characterized in terms of various stable and unstable conditions inside the porous particles. Simplifications in the mathematical model are shown to be invalid in many situations.
The friction factor–Reynolds number relation for the steady flow of pseudoplastic fluids through rectangular ducts. Part II. Experimental results
Authors: Wheeler John A. , Wissler Eugene H. 
Published: June 2004

AbstractThe friction factor and Reynolds number were measured for sodium carboxymethylcellulose (cmc) flowing through a rectangular duct. Measured values were compared with values calculated in Part I of this paper. Both a pipe viscometer and a Couette viscometer were used to evaluate the rheological parameters for the fluids. Calculations were based on a power law model. The agreement between theoretical and experimental values was excellent.
Mixing and chemical reaction in turbulent flow reactors
Authors: Keeler R. Norris , Petersen E. E. , Prausnitz J. M. 
Published: June 2004

AbstractMixing and a rapid, second‐order irreversible chemical reaction were studied in a turbulent chemical flow reactor, with a point conductivity probe used to detect changes in concentration. From the mathematical theory of Toor, it is shown experimentally that data on the mixing of a passive scalar additive in a nonreactive system may be used accurately to predict the yield of a rapid, irreversible second‐order reaction when the hydrodynamics and initial conditions on mixing for the reactive system are identical to those of the nonreactive system. Increasing the bulk average concentration of one reactant is shown to have a strong effect on the overall reaction yield.
Foam columns for countercurrent surface—liquid extraction of surface‐active solutes
Authors: Haas Paul A. , Johnson H. F. 
Published: June 2004

AbstractThe foam separation process uses differences in surface activity to separate components of a solution. Stable foams can flow upward countercurrent to liquid to give countercurrent differential separations with stripping, enrichment, or scrubbing similar to solvent extraction.Six‐ and 24‐in. I.D. foam columns were operated with sodium dodecylbenzenesulfonate solutions to measure height of transfer unit (HTU) values and foam densities and to develop satisfactory gas spargers, liquid feed distributors, foam drainage conditions, and foam condensation equipment. The HTU values for stripping of Sr‐89 were about 1 cm. for the best conditions of uniform foams, liquid flows of 100 gal./sq.ft.hr. or less, and uniform liquid feed distribution with low inlet velocities. Variations of countercurrent column lengths within 10 to 28 cm. caused little variation in HTU values. The foams were condensed, with four types of pneumatic or mechanical foam breakers used. A pilot plant was designed for decontamination of a low level radioactive waste.
Constitutive equations for viscoelastic fluids with application to rapid external flows
Authors: White J. L. , Metzner A. B. 
Published: June 2004

AbstractA major problem in the analysis of complex flows of viscoelastic fluids lies in the development of a suitable constitutive equation relating stresses to the kinematics of deformation. In this paper an equation is developed from successive approximations to a very general theory of viscoelasticity. This equation, which predicts both a non‐Newtonian viscosity coefficient and normal stress effects in simple laminar shearing flows, appears to reflect a reasonable compromise between simplicity and useful applicability to real materials.The use of this equation is illustrated by means of a study of rapid flows about submerged objects. The results of this study are compared with the usual boundary‐layer theory for Newtonian fluids, and the implications of this comparison are discussed in some detail.
Correlation of latent heats of vaporization
Authors: Martin Joseph J. , Edwards John B. 
Published: June 2004

AbstractGeneralized equations for vapor pressure and PVT behavior are used to develop a functional relationship between latent heat of vaporization and reduced temperature and pressure. This function leads to a graphical correlation which utilizes the slope M of the vapor‐pressure curve at the critical point. The correlation gives the latent heat of vaporization at any temperature in the two‐phase region for any substance for which the critical point and one vapor‐pressure point are known. The correlation is particularly useful for prediction of latent heat of vaporization near the critical point by the use of information for removed from the critical. Included in the study are polar, nonpolar, organic, inorganic, and metallic substances. General predictions of latent heat as a function of temperature are within a few percent wherever comparisons can be made with experimental data.
Mass transfer in horizontally moving stable aqueous foams
Authors: Weissman Eugene Y. , Calvert Seymour 
Published: June 2004

AbstractAn efficient gas absorption device has been developed based on a stable aqueous foam moving in a horizontal duct, with a gas‐liquid interaction that causes only negligible pressure drops.The study of a liquid‐phase and a mostly gas‐phase‐controlled system has indicated that their mass transfer performance can be predicted. This is based on hydrodynamic data for flowing foams, obtained in a preliminary study published elsewhere.The influence of geometry, foaming solution properties, and surfactant‐caused interfacial resistance are included in the analysis.
Significance of pressure gradients in porous materials: Part III. Effect of pressure gradients on the effectiveness of porous catalysts
Authors: Otani Seiya , Wakao Noriaki , Smith J. M. 
Published: June 2004

AbstractThe effect of a change in moles, due to reaction, on the effectiveness of a catalytic reaction is analyzed by calculating the concentration profile along a capillary whose wall surface acts as a catalyst and within a spherical, porous, catalyst pellet. The effectiveness factor E is influenced most when the diffusion is predominately of the bulk type and none at all for Knudsen diffusion. For an increase in moles, the diffusion of reactant into the pellet is suppressed because of the opposing pressure gradient. The result is a decrease in E.Application to a typical bidisperse catalyst pellet such as alumina indicates that the reduction in E due to an increase in moles is not likely to be large. The effect can be important only if the change in moles exceeds 1 or 2, and the pellet is of the low‐density type with large macropores.In contrast the pressure gradient is large only when mass transfer is by the Knudsen process.
Normal stress and viscosity measurements for polymer solutions in steady cone‐and‐plate shear
Authors: Williams Michael C. 
Published: June 2004

AbstractNormal stress and viscometric measurements were made on nine polymer solutions with cone‐and‐plate instruments. Temperature, concentration, molecular weight, and chemical structure were varied. Zero‐shear viscosities, obtained by extrapolation of falling‐sphere data, ranged from 0.7 to 380 poise.A brief description is given of a normal stress‐measurement apparatus, incorporating fast‐response strain gauge pressure transducers. Measurements were made at shear rates between 5 and 2,800 sec.−1, sometimes necessitating a considerable correction for inertial forces.Non‐Newtonian viscosity, normal stress, recoverable shear strain, and elastic modulus are presented in terms of modified Ferry reduced variables.
An analytical solution for the nonlinear frequency response of radiant heat transfer
Authors: Blum Edward H. 
Published: June 2004

AbstractAn analytical solution is presented for the nonlinear frequency response of a system in which radiant heat transfer is coupled with conduction. The model is that of an object inside an evacuated enclosure whose wall temperature oscillates about a mean. A perturbation analysis solves the describing equations for oscillatory amplitudes less than one‐tent the mean wall temperature. An exact solution to a Ricatti differential equation verifies the perturbation analysis. These solutions show that, contrary to linear experience, the average object temperature over an oscillatory cycle exceeds the mean at the wall.The complete solution for the frequency response can be divided into three regimes. In the first, at low frequencies, all response is truly linear. In the second, higher harmonics become important, but the response remains that of a lumped parameter systems. In the third, response changes with distance from the object surface and the response at the surface dominates. Nonlinearities are important in the second and third regimes. The solution has several applications.
Unsteady heat transfer to slug flows: Effect of axial conduction
Authors: Chu S. C. , Bankoff S. G. 
Published: June 2004

AbstractSolutions are obtained for three illustrative cases of unsteady heat transfer to slug flows, taking axial conduction into account. The magnitude of the correction to the solutions neglecting this effect is shown to be quite appreciable near the leading edge. In agreement with previous steady state estimates, the axial conduction correction becomes negligible for Peclet numbers in excess of 100.
Water‐oil displacements from porous media utilizing transient adhesion‐tension alterations
Authors: Michaels Alan S. , Porter Marcellus C. 
Published: June 2004

AbstractPrevious laboratory studies have demonstrated that the injection of small quantities of reverse‐wetting agents during water displacement can increase oil recovery from unconsolidated porous media. Hexylamine is a suitable reverse‐wetting agent. It has been found that the effectiveness of this treatment increases with the quantity of amine injected (slug volume and/or amine concentration in the slug), and that treatments sufficient to stimulate oil production at high water flow rates did not do so at low flow rates. It has been established that the stimulation of oil production by this technique is accomplished by transient adhesion‐tension alterations, resulting in the spontaneous accumulation of oil into large continuous masses which are subsequently mobilized.The present investigation has attempted to investigate the effect of other variables thought to be important in this system in order to clarify the mechanism by which increased oil recovery is effected. Specifically, the mechanism by which large oil masses are formed and propagated was studied.Displacement studies conducted in a glass‐grid micromodel, under cinemicrographic observation, revealed that large oil masses form as a consequence of restoration of water wettability (amine desorption) but only if the local oil saturation exceeds the irreducible minimum value (under water‐wet conditions). Mobilization of these oil masses was observed under the influence of a favorable wettability gradient.Displacement studies were also performed in unconsolidated silica sand beds, under conditions of varying oil‐water viscosity ratio, hydraulic permeability, flow rate, and time at which the amine was injected. In the range of the variables investigated, the additional oil recovered (by treatment) increased as the viscosity ratio increased oil recovery. Water‐oil displacement efficiencies enhanced by amine treatment were found to correlate satisfactorily with a parameter representing the ratio of the hydraulic forces to the capillary forces within the medium.
Deposits formed beneath bubbles during nucleate boiling of radioactive calcium sulfate solutions
Authors: Hospeti Narayan B. , Mesler Russell B. 
Published: June 2004

AbstractMoore and Mesler postulated microlayer evaporation beneath a bubble to explain the sudden temperature drops observed by them during nucleate boiling of water.A method was devised to estimate the microlayer thickness from the deposit formed by a series of bubbles during nucleate boiling of saturated calcium sulfate solution containing radioactive sulfur‐35. The results support the microlayer evaporation hypothesis.
A pitot tube method for measuring the first normal stress difference and its influence on laminar velocity profile determinations
Authors: Savins J. G. 
Published: June 2004

AbstractA scheme is outlined which enables the calculation of the normal stress difference P11‐P22 in fluids undergoing steady Poiseuille flow from measurements with a pitot tube of local velocity distributions. This new technique should enable measurements in a region of shear rate comparable to that encountered in the torsional and circular flow methods. A particularly interesting consequence of the method is it leads one to the inescapable conclusion that the presence of finite normal stresses should produce significant aberrations on the measurement of the velocity profile in the laminar flow of viscoelastic fluids. The presence of a P11‐P22 induced aberration on the velocity profile measurement suggests that caution be exercised in the practice of deducing estimates of the thickness of a boundary layer in the nonlaminar flow of these fluids.