bluuebunny/crossref_metadata_2025_split huggingface dataset:
A statistical model of a porous medium with nonuniform pores
Authors: Haring R. E. , Greenkorn R. A. 
Published: June 2004

AbstractA random network model of a porous medium with nonuniform pores has been constructed. Nonuniformity is achieved by assigning two‐parameter distributions to pore radius and pore length. Statistical derivations result in expressions for bulk model properties which are consistent with known empirical behavior of porous media such as capillary pressure, hydraulic permeability, and longitudinal and transverse dispersion. A series of experiments is suggested whereby the parameters of porous media structure may be determined from observed macroscopic behavior by using the expressions developed in this paper.
Laminar‐turbulent transitional flow phenomena in isosceles triangular cross‐section ducts
Authors: Hanks Richard W. , Cope Richard C. 
Published: June 2004

AbstractA theoretical analysis of the laminar‐turbulent transition phenomenon is presented for the case of steady, isothermal, fully developed flow of Newtonian fluids in straight ducts of constant isosceles triangular cross section. As a result of this analysis, the simultaneous existence of macroscopically large stable regions of laminar and turbulent flow are predicted to occur during the transition phenomenon. The existence of this special type of flow field, which has not been previously predicted theoretically, is shown to be a consequence of the presence of an asymmetric shear stress distribution. The results of an experimental study are also presented. These data verify the predictions made by the theoretical analysis.
Initiation of thermal convection in finite right circular cylinders
Authors: Catton Ivan , Edwards D. K. 
Published: June 2004

AbstractLinear perturbation analyses are extended to determine the lowest Rayleigh number at which convection initiates in a vertical cylinder heated on the bottom and cooled on the top. The critical Rayleigh number for the first mode of convection in a right circular cylinder with a perfectly conducting wall is shown to be three times larger than that in such a cell with a perfectly adiabatic side wall. An adjusted wave number is shown to make the results of Pellew and Southwell applicable to the adiabatic wall in a manner similar to that used by Pnueli and Ostrach for the perfectly conducting side wall. The results are compared with experiment and are in very good agreement.
The absorption of carbon dioxide by weak base ion exchange resins
Authors: Weber Oscar W. , Miller Irving F. , Gregor Harry P. 
Published: June 2004

AbstractA study of the feasibility of using ion exchange resin systems for carbon dioxide absorption from gas streams was completed with the conclusion that such a system could compete very successfully with atmospheric control systems now in use. A detailed study of such a system based on polyethylenimine showed that this material is superior to any of the commercially available weak base resins tested. The kinetic data obtained correlated very well when a model was postulated that was based on diffusive transfer through a gas film, a water film, and the resin particle in series, with diffusion with the resin particle as the rate determining step.
Mass transfer in two‐phase flow in horizontal pipelines
Authors: Jepsen John C. 
Published: June 2004

AbstractThe objective of the present study was to obtain data on the rate of liquid‐phase controlled mass transfer in two‐phase gas‐liquid flow in horizontal pipes. Studies were made on the effect of the mean gas and liquid flow rate, pipe diameter, and pipe orientation on k𝓁a, the mean liquid‐phase film mass transfer coefficient. Experimental studies were made on 1 and 4 in. I.D. horizontal pipelines; on 4 in. I.D. 180 deg. vertical short radius bend (H/D = 2); and on 3/16, 5/16, and 7/16 in I.D. tubes wound in 4‐in. diameter spirals (upflow). A general correlation is presented for k𝓁a as a function of the two‐phase frictional energy dissipation, liquid‐phase physical properties, and pipe diameter.
Self‐diffusion measurements in methane by pulsed nuclear magnetic resonance
Authors: Dawson Rapier , Khoury Fouad , Kobayashi Riki 
Published: June 2004

AbstractThe self‐diffusion coefficient of methane has been measured from 150° to 350°K. and from 200 to 5,000 lb./sq. in. abs. At constant temperature, the density‐diffusivity product is constant up to neighborhood of critical density and decreases sharply above that density. The temperature dependence of the low density data agrees with Chapman‐Enskog theory. The Lennard‐Jones (6‐12) parameters determined from the low density data (ϵ/k = 130°K., σ = 3.85Å.) are in good agreement with those determined by other methods. A correlation for the self diffusion coefficient for methane has been developed which may provide predictions of other spherical nonpolar gases.
Virial coefficients and critical properties of perfluorohexanes
Authors: Taylor Z. L. , Reed T. M. 
Published: June 2004

AbstractCompressibility measurements of the gas phase are reported for the compounds n‐C6F14, 2‐CF3C5F11, 3‐CF3C5F11, 2,3‐(CF3)2C4F8, and cyclo C6F12. The measurements range from 1 to 18 atm. pressure and from 80° to 180°C. Second and third virial coefficients and critical properties have been calculated and are reported.
The influence of intraparticle diffusion in fixed bed catalytic reactors
Authors: Liu Shean‐Lin 
Published: June 2004

AbstractBy using curve fitting techniques, mathematical formulas are obtained for the catalyst effectiveness factors for nonisothermal first‐order and second‐order irreversible chemical reactions. The effects of intraparticle mass and heat diffusion upon the concentration and temperature profiles in adiabatic and nonadiabatic catalytic reactors are examined. A relation between the maximum interstitial adiabatic temperature and the maximum intraparticle temperature in the reactor is obtained. For some sets of parameters in a nonadiabatic reactor, the concentration and temperature and, consequently, the reactor effluent are sensitive to small changes in the properties of catalyst particles.
Feedforward computer control of a class of distributed parameter processes
Authors: Paraskos J. A. , McAvoy T. J. 
Published: June 2004

AbstractA finite difference technique has been developed which is suitable for the derivation of feedforward control algorithms for the control of distributed parameter processes. The method embodies both steady state and transient feedforward compensation.An experimental study, involving closed loop, on line, analogue computer control of a simple distributed parameter process proves the feasibility of the finite difference technique. The process under study is a steam water heat exchanger subject to inlet temperature forcing and controlled by flow rate manipulation. The new technique yielded significantly improved results when compared with the performance of a conventional two‐mode feedback controller, or a linearized feedforward control algorithm.
Forced convection in three‐dimensional flows: II. Asymptotic solutions for mobile interfaces
Authors: Stewart W. E. , Angelo J. B. , Lightfoot E. N. 
Published: June 2004

AbstractBoundary‐layer solutions are given for heat and mass transfer at mobile interfaces. The results are asymptotically valid for small thermal and material diffusivities, or for short exposure times. Phase breakup and coalescence are formally included, but Marangoni effects are not. Effects of rapid mass transfer, chemical reactions, and variable boundary conditions are evaluated. The treatment is a generalization of the penetration and surface‐renewal theories.
Mass transfer across a nonequilibrium interface
Authors: Dang Vi‐Duong , Gill William N. 
Published: June 2004

AbstractThe problem of mass transfer with nonequilibrium at, and significant convection across, the interface has been studied by the method of matched asymptotic expansions. The inner solution for small values of t or z/Um was found in terms of fk functions which were obtained in closed analytical form. The outer solution for large values of t or z/Um was found in terms of gk functions which had to be determined numerically. With these solutions, calculation of concentratration distributions or instantaneous rates of mass transfer is straightforward, but determination of the total amount of mass transfer as a function of time is complicated by the lack of an intersection wherein the inner and outer solutions overlap and converge. To avoid the need for graphical interpolation and integration of the interfacial concentration as a function of time to obtain the total mass transferred, the constant of integration M1 is found to be (−kγ\documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt \pi $\end{document}/2h) by assuming that the ratio of mass transferred with an equilibrium interface to that with a nonequilibrium interface is independent of whether or not Vy convection is negligible in the system as t → ∞.The effect of a nonequilibrium interface is greatest for small t in unsteady systems and z/Um in steady state systems. This occurs because the departure from their equilibrium values of the interfacial concentrations of the phases in contact is greatest when they are first brought into contact. The larger the interfacial mass transfer coefficient α, the smaller is the time required for the interfacial concentrations to achieve their equilibrium values.Other things being equal, the rate of mass transfer is greatest when the driving force xA*‐x is greatest. Since the departure from equilibrium at the interface is greatest for small values of time, it follows that nonequilibrium interfacial phenomena can be observed most easily in systems where the rate of mass transfer is high. This is also the case when one cannot neglect the effect of finite velocity at the interface which is shown in the present work to be a significant effect.The method of analysis can be used to study a variety of problems in addition to the specific system considered here. In particular, both batch and flow reverse osmosis problems can be attacked by the present approach.
Methanol synthesis catalysis in an internally recycled reactor
Authors: Brown C. E. , Bennett C. O. 
Published: June 2004

AbstractA gradientless reactor has been tested by measurement of the chemical reaction rate in the synthesis of methanol from carbon monoxide and hydrogen. The reactor behaves as a well‐stirred tank, and data have been obtained at 3,000 lb./sq.in.abs. over the temperature range 300° to 400°C.Rate data have been obtained for commercial zinc chromite catalyst in particle form and for the commercial ¼‐in. pellets. The effectiveness factors derived from these experiments have been used to estimate the tortuosity of the pellets; it is found to agree qualitatively with the value measured from experiments on pure diffusion in a catalyst pellet.
Rate of coalescence of the dispersed phase in a laboratory mixer settler unit: Part I
Authors: Jeffreys G. V. , Davies G. A. , Pitt K. 
Published: June 2004

AbstractThe rate of coalescence of large swarms of drops of a dispersed phase in the settler of a stage, laboratory mixer settler has been studied in order to establish the parameters that determine the dimensions of settlers used in extraction processes and effluent treatment. Part I is devoted to a description of the apparatus, experimental technique, and presentation of experimental results. Part II describes the development of a mathematical model which has been employed to analyze the results and is submitted as the basis for the design of settlers.
Diffusion in the ternary system d‐tartaric acid—l‐tartaric acid‐water at 25°C
Authors: Bremer M. F. , Cussler E. L. 
Published: June 2004

AbstractTernary diffusion coefficients at 25°C. of the system 0.5 g./cc. d‐tartaric acid—0.5 g./cc. l‐tartaric acid‐water are reported. The results allow experimental verification of the theory for the diffusion of two indistinguishable solutes and clearly illustrate the difference between mutual and tracer diffusion. Moreover, the results allow calculation of ternary mass transfer coefficients and ternary tray efficiencies for the case of two similar species dissolved in a third.
Simultaneous noncatalytic solid‐fluid reactions
Authors: Wen C. Y. , Wei L. Y. 
Published: June 2004

AbstractSolid‐fluid reactions often involve two or more simultaneous reactions because either the feed contains multiple fluid reactants or the fluid products are reactive with the solid. Three types of simultaneous reactions, independent, parallel, and consecutive, are examined in terms of the selectivity and the effectiveness factor based on the unreacted core shrinking model under isothermal conditions. Criteria for high selectivities are derived, and effects of diffusion and chemical reaction are discussed.
Evaporation and drying of drops in superheated vapors
Authors: Trommelen A. M. , Crosby E. J. 
Published: June 2004

AbstractThe evaporation of pure liquid drops and the drying of drops containing suspended and dissolved solids in an atmosphere of superheated vapor were studied. Changes in the weight and temperature of approximately 2 μliter drops of four food products, five miscellaneous materials, and pure water were measured as evaporation and drying proceeded at different drying temperatures. Evaporation of water was found to take place more slowly in superheated steam than in air. However, the medium, in which faster drying occurred, depended upon the material being dried. No major differences between the final products were observed for these two drying media except that some materials yielded denser particles in superheated steam than in air.
Withdrawal of flat plates from power law fluids
Authors: Tallmadge John A. 
Published: June 2004

AbstractA new one‐term withdrawal expression for power law fluids is developed from theoretical equations. Comparison with film thickness data for three carbopol fluids of α = 1.79 to 2.68 indicates agreement similar to that observed with valid Newtonian theories. The agreement was verified by comparison with independent measurements of entrainment flow rate.
Laminar flow in the entrance region of a cylindrical tube: Part II. Non‐Newtonian fluids
Authors: Sylvester N. D. , Rosen S. L. 
Published: June 2004

AbstractThe laminar flow of dilute aqueous polymer solutions was studied in the entrance region of a cylindrical tube. In laminar, fully developed, steady tube flow, elastic and inelastic fluids were indistinguishable. Viscoelastic fluids exhibited much higher entrance pressure losses than did inelastic fluids with comparable viscous properties. A method has been developed for separating the elastic portion of the overall entrance loss and shows that in some cases the elastic contribution represents as much as 80% of the total. An analysis is also presented which allows calculation of the elastic entrance loss in terms of a Hookean shear modulus.
numerical investigation of free convection between two vertical coaxial cylinders
Authors: Schwab Thomas H. , De Witt Kenneth J. 
Published: June 2004

AbstractFree convection between two vertical coaxial cylinders was studied by solving the governing transport equations as an initial‐value problem. The coupled, nonlinear, partial differential equations were converted into a set of difference equations by use of an alternating‐direction implicit finite‐difference numerical scheme. Twenty‐four different combinations of Prandtl and Grashof numbers, and height to annular spacing ratios were used to characterize the problem. The results are presented primarily in the form of contour maps for the steady‐state isotherms and streamlines.For Rayleigh numbers greater than 5 × 103, a fully developed boundary‐layer flow was found to exist in the cavity. The interior region of the annulus was found to be thermally stratified and to possess a nearly uniform vertical temperature gradient, with a unicellular flow pattern being generated.With Rayleigh numbers of 5 × 104 and greater, it was found that the flow patterns could not be properly described with a grid spacing of 1/10. The variation of the steady‐state mean Nusselt number with Prandtl and Rayleigh numbers and with geometric ratios was also investigated.
Unsteady state behavior of multicomponent distillation columns: Part I: Simulation
Authors: Howard G. Michael 
Published: June 2004

AbstractA very general form of the basic column equations is presented which allows a wide choice in the form of the specifications of variables required to define the column operation. Variable plate holdups, variable plate efficiencies, heat losses from the column, and finite time liquid flow dynamics are some of the specifications considered. The values of the implicit column variables during the unsteady state period are found by a method which is independent of the numerical procedure chosen to solve the differential equations. Computer runs with the Kutta‐Merson method used to solve the differential equations were made for a column approaching steady state at total reflux. The effect of different variable specifications on this computer column are discussed.
Feedback control of an enriching column
Authors: Shoneman Keith F. , Gerster Jack A. 
Published: June 2004

AbstractThe transient behavior of a 24‐in. diameter, 10‐tray enriching column was investigated experimentally while the column was operated under closed‐loop, feedback control. This behavior was compared with that of a perturbated linear model with the column open‐loop behavior being represented with simple transfer functions in the frequency domain. Comparisons showed that control parameters determined with the predictive linear model were conservative and permitted stable and smooth responses of the experimental column.
Saturated liquid enthalpies of ethane–n‐butane‐n‐pentane system with multicomponent clapeyron equation
Authors: Lee Byung‐Ik , Edmister Wayne C. 
Published: June 2004

AbstractEnthalpies of the coexisting equilibrium vapor and liquid mixtures of the ethane‐n‐butane‐n‐pentane system are computed at several pressures. Saturated liquid enthalpies are obtained by using a new multicomponent Clapeyron equation with the B‐W‐R equation of state and the experimental temperature‐composition data for the ternary mixture. Saturated vapor enthalpies are calculated by applying the B‐W‐R equation to the vapor mixture. Ideal gas state enthalpies are used in both vapor and liquid enthalpy calculations.
Green's functions for the Graetz problem and interfacial concentrations
Authors: Gidaspow Dimitri 
Published: June 2004

AbstractGreen's functions for various Graetz problems are identified. Multiple forms of Duhamel's formula with improved convergence were obtained, using particular solutions to unit flux, linear prescribed flux, and similar problems. The method makes it possible to quickly calculate interfacial concentrations from a knowledge of outlet concentrations at several flow rates. The analysis is illustrated with experimental combustion data from a tubular reactor.
Optimal control policies for tubular reactors experiencing catalyst decay. Part 1. Single bed reactors
Authors: Ogunye A. F. , Ray W. H. 
Published: June 2004

AbstractThe optimal control problem is formulated, and a weak maximum principle for such distributed parameter systems is derived. From this principle an efficient computational algorithm is presented which allows the simultaneous solution of the problems of both catalyst distribution (along the reactor) and optimal control. Detailed numerical examples are worked for isothermal reactors, adiabatic reactors, and adiabatic reactors with both a catalyst distribution problem and an optimal control problem. For irreversible reactions constant conversion policies are found to be optimal a significant portion of the time.
Mass transfer and drag coefficients of bubbles rising in dilute aqueous solutions
Authors: Raymond Delmar R. , Zieminski Stefan A. 
Published: June 2004

AbstractThe effects of aliphatic alcohols on mass transfer and drag coefficients of a carbon dioxide bubble were investigated in very dilute aqueous solutions. A high speed photography technique provided an almost continuous record of the bubble volume, shape, and oscillation, as related to the height of the bubble in the liquid and the time elapsed from the moment of its release. The results showed that the concentration, molecular size, and structure of the investigated alcohols have a pronounced effect on mass transfer as well as drag coefficients of the rising bubble. The significance of these effects with respect to idealized models of a highly circulating bubble and a solid sphere was considered, and a functional relationship was found to exist. This relationship may be applied to systems more complex than a single bubble.
Vapor‐liquid phase behavior of the hydrogen‐propane and hydrogen‐carbon monoxide‐propane systems
Authors: Trust D. B. , Kurata F. 
Published: June 2004

AbstractVapor‐liquid equilibria data for the hydrogen‐propane binary system and the hydrogen‐carbon monoxide‐propane system were taken at temperature of −185° to +75°. and under pressures as high as 3000 psi. Vapor‐liquid data for the hydrogen‐carbon monoxide‐propane system are reported at −50°, 0°, and +50°. at pressures of 500, 1000, and 2000 lb./sq.in. abs. for each of the three temperatures. The Krichevsky‐Kasarnovsky equation adequately correlated the solubility data of hydrogen in the liquid phase of the hydrogen‐propane system. Hydrogen‐propane data are compared with the data of two previous studies.
Stretching of viscoelastic liquids
Authors: Denn M. M. , Marrucci G. 
Published: June 2004

AbstractAnalyses of stretching of a viscoelastic liquid have been interpreted as showing that there is a maximum stretch rate to which the material can be subjected, and several physical phenomena have been explained on this basis. It is shown here theoretically and experimentally that the concept of a limiting stretch rate does not have general validity.
A stochastic model of packed‐bed mixing and mass transfer
Authors: Schmalzer D. K. , Hoelscher H. E. 
Published: June 2004

AbstractA new model of packed‐bed behavior based on a second‐order stochastic process is developed and examined. The model takes as the basis process the transitions of fluid “packets” among allowed velocity states. The observable phenomenon, that is, the spatial distribution of packets, is a projection of the velocity state process.Results from the model compare well with results from experiments for mixing in packed beds. Model parameters are consistent, and correlate with the physical parameters of the systems. Present results under mass transfer conditions are inconclusive but encouraging.
Trajectory optimization techniques in chemical reaction engineering: I. Boundary condition iteration methods
Authors: Jaspan R. K. , Coull J. 
Published: June 2004

AbstractA new generalization of boundary condition iteration (BCI) methods is developed, based on a suggestion of Denn and Aris. This simplifies to Horn's equation for up to two state equations and to previous boundary iteration methods when

is explicitly soluble for

as a function of the constants, the state and the adjoint variables. The new general method is also applicable when this latter function is unobtainable.Distinct improvement in the convergence rates of the existing BCI methods has been obtained through the introduction of a correction specific to each state variable.A convergence procedure for use with Horn's equation is proposed and the resultant algorithm has desirable properties.