bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some aspects of crystallization theory: Systems that violate McCabe's delta L law
Authors: Canning T. F. , Randolph A. D. 
Published: June 2004

AbstractA new empirical model has been proposed to described crystallization systems where the growth rate increases with increasing crystal size in violation of McCabe's ΔL law. Experimental data for Glauber's salt have been presented to illustrate the fit of the new model to an actual system. Equations for steady state crystal size distributions with the use of the proposed model have been derived. Wider use of population density plots for analysis of crystallization systems along with the coefficient of variation to describe a distribution numerically is recommended.
Interfacial turbulence during the absorption of carbon dioxide into monoethanolamine
Authors: Brian P. L. T. , Vivian J. E. , Matiatos D. C. 
Published: June 2004

AbstractSevere discrepancies exist between theoretical considerations and the carbon dioxide–monoethanolamine absorption data available in the literature. By desorbing the inert tracer propylene simultaneously with the absorption of carbon dioxide into monoethanolamine in a short wetted‐wall column, it is shown that the physical mass transfer coefficient is increased substantially by the carbon dioxide–monoethanolamine chemical absorption process. This is presumably due to interfacial turbulence driven by surface tension gradients. The use of the actual physical mass transfer coefficient prevailing during carbon dioxide absorption into monoethanolamine results in a considerable improvement in the agreement between the penetration theory solution and the experimental data on the rate of absorption of carbon dioxide into monoethanolamine.
Isothermal homogeneous two‐phase flow in horizontal pipes
Authors: Huey C. T. , Bryant R. A. A. 
Published: June 2004

AbstractIn the first part of this paper a theory for isothermal homogeneous two‐phase, liquid‐gas flow in horizontal pipes is established by introducing the concept of Mach number and by considering the medium to be a pseudo gas. The theory takes account of wall friction, compressibility and flow choking. A set of working formulas is obtained. In the second part, results of experiments on homogeneous bubbly flows of water‐air mixtures in a 1‐in. Pipe are reported. Criteria for the occurrence of bubbly flow are established and the occurrence of flow choking confirmed. It is shown that the mathematical model is adequate insofar as it explains, phenomenologically, real flow conditions.
The control of nonlinear systems. Part III: Invariant imbedding and quasilinearization
Authors: Rothenberger B. F. , Lapidus Leon 
Published: June 2004

AbstractAn iterative technique is proposed that solves the two‐point boundary value problem formed from the variational equations for the optimal control of nonlinear systems. The computational algorithm utilizes invariant imbedding to provide a set of the unknown boundary conditions and quasilinearization to calculate the optimal control policy. A numerical example indicates that the method exhibits considerable promise.
Flow of molten polymers through porous media
Authors: Gregory Dale R. , Griskey Richard G. 
Published: June 2004

AbstractThe flow of molten polymer through porous media has been investigated at constant temperatures and flow rates. Temperatures of 375°, 400°, and 425°F., flow rates from 12 to 60 g./min. and particle sizes from 0.054 in. to 6 mm. in diameter were studied. A modified Darcy's law was developed using the Metzner‐Reed modification of the Mooney‐Rabinowitsch relation. This form was then used to develop a modified friction factor plot which correlated the data with an average error of 5.02%. Calculated superficial velocities from the Darcy's law equation checked experimental values generally to within 10%. A technique for estimating shear rates when curved rheological flow curves occurred was also developed.
Heat transfer and binary diffusion with thermodynamic coupling in variable‐property forced convection on a flat plate
Authors: Zeh Dale W. , Gill William N. 
Published: June 2004

AbstractThe variable‐property, laminar, boundary‐layer equations, which describe simultaneous momentum, heat, and binary mass transfer with thermodynamic coupling,Thermodynamic coupling refers to the Soret (or thermaldiffusion)effect, which is the flow of mass caused hy a temperaturegradient, and the Dufour (or diffusion thermo) effect, which is theflow of heat caused by a concentration gradient.
are analyzed for air flows over a flat plate with the injection of foreign gases through the solid surface. A simplified general treatment of thermodynamic coupling is developed and applied to yield approximate but accurate expressions for evaluating heat transfer rates and adiabatic wall temperatures for injection of hydrogen, helium, and carbon dioxide. This method explains why the driving force based on (Tω − Tω) can be used to correlate heat transfer results for situations where diffusion thermo is important. Furthermore, and perhaps most significant, the method provides a simple error estimate for the correlation obtained by using the adiabatic wall temperature.It is shown that the injection of lightweight gases can significantly reduce viscous dissipation in flows over slender bodies and that diffusion thermo and dissipation effects can be otion in flows over slender bodies and that diffusion thermo and dissipation effects can be of the same order of magnitude even for reasonably high‐velocity flows. These effects are discussed in terms of convenient quantities, called σ functions.
Numerical solution of the Navier‐Stokes equation for flow past spheres: Part II. Viscous flow around circulating spheres of low viscosity
Authors: Hamielec A. E. , Johnson A. I. , Houghton W. T. 
Published: June 2004

AbstractSteady state solutions of the Navier‐Stokes equations for Reynolds numbers of 0.1, 1, 50, 100, and 200 have been obtained by using finite‐difference methods. The effects of radial and angular step size and wall proximity have been investigated. Results were found in the form of stream function and vorticity distributions with pressure distributions and drag coefficients calculated from them. The results compare favorably with experimental data and show a steady trend from Hadamard‐Rybczynski flow to boundary‐layer flow after Levich‐Chao‐Moore. For a circulating sphere of low viscosity there is no flow separation indicated at Reynolds numbers equal to or less than 200.
The forgotten effect in thermal diffusion
Authors: Korchinsky Walter J. , Emery Alden H. 
Published: June 2004

AbstractThe basic equations that describe the thermal diffusion column, including the forgotten effect, were solved numerically. When the density of the liquid in the column varies with concentration, the effect is important in transient batch operation of columns, increasingly so as the wall spacing decreases, but it has no influence at the steady state. Experimental work corroborated the theoretical results.According to the theory, the instances of concentration reversal reported in the literature cannot be the result of the forgotten effect; the fluids involved could not have had the necessary properties. Attempted duplications of these instances in careful experiments yielded normal behavior. However, theoretical and experimental work on a column with a deliberately nonconstant wall spacing indicated that concentration reversals could occur in the complete absence of any forgotten effect contribution.
Partial control of linear inventory systems
Authors: Wilde Douglass J. , Passy Ury 
Published: June 2004

AbstractFeedback and feedforward inventory control systems are derived which give improved probability of holding all inventories between predetermined limits, even when there are fewer controllers than controlled variables. The concept of partial controllability is developed to describe systems with uncontrollable states. An example shows that four tank levels can be held within limits with high probability, with only one manipulated flow rate used.
The prediction of bubble terminal velocities from wave theory
Authors: Mendelson Harvey D. 
Published: June 2004

AbstractThe terminal velocity of bubbles in low viscosity liquids of infinite extent is known to undergo a marked transition in behavior at an equivalent radius in the order of 0.07 cm. This transition is apparently due to a change from viscous to inviscid flow. It is also known that the inviscid flow regime can be further subdivided into surface tension‐ (Weber number) and buoyancy‐ (Froude number) dominated regimes. This behavior of rising bubbles is strikingly similar to the behavior of surface waves propagated over deep water. The analogy is found to be in quantitative agreement when the wavelength is suitably interpreted in terms of bubble dimensions. The inference of this analogy is that bubbles may be thought of as interfacial disturbances whose rate of propagation is governed by the well‐known laws of wave motion.
Flow of viscoelastic fluids past a flat plate
Authors: Hermes R. A. , Fredrickson A. G. 
Published: June 2004

AbstractThe flow of viscoelastic fluids past a flat plate has been investigated. Experimental studies were performed with aqueous solutions of sodium carboxymethylcellulose used as viscoelastic fluids and corn syrup as a viscous Newtonian fluid. It was observed that the flow patterns of elastic and inelastic fluids are markedly different. Tracer particles placed in the approaching viscoelastic fluids to follow their motion were seen to first decelerate and then to accelerate until a nearly constant velocity was reached. On the other hand tracer particles in the Newtonian fluid were observed merely to decelerate smoothly to the constant velocity.The drag force measured for the viscoelastic fluids was found to be roughly twice that predicted by inelastic models of fluid behavior. Predicted and measured values of the drag force for the Newtonian fluid agreed well.A discussion of mathematical solutions to the problem of flow of viscoelastic fluids past a flat plate is given. Solutions are obtained for a prototype of flow past a flat plate, the suddenly accelerated flat plate (Stokes' problem) with linear viscoelastic models used. The results from Stokes' problem qualitatively explain the anomalous kinematical behavior and the large drag force.
Electrokinetic‐potential fluctuations produced by pipe flow turbulence
Authors: Chuang Hsing , Cermak J. E. 
Published: June 2004

AbstractThe distribution across a pipe of turbulent intensities, shearing stress, and energy spectra are inferred from measured electrokinetic‐potential fluctuations in a fully developed flow of distilled water in a 2.54‐cm. diameter glass pipe. These quantities are shown to be in good agreement with those obtained by Laufer and Sandborn with hot‐wire anemometers for air flows at the same mean Reynolds number. A tentative analytical model of the phenomenon is constructed and analyzed by Maxwell's electrodynamic field equations for a nonmagnetized medium moving with a velocity which is much smaller than the velocity of light. A set of equations governing the interrelation between the electrokinetic‐potential fluctuations and the turbulent velocity‐fluctuation components of the flow field in fully developed pipe flow is deduced. Fourier transforms are then introduced and simple relations between the electrokinetic‐potential fluctuations and velocity fluctuations are obtained.
Two‐phase flow in Hele‐Shaw models
Authors: Greenkorn R. A. , Matar J. E. , Smith R. C. 
Published: June 2004

AbstractA study of the motion of the interface in two‐phase flow in two dimensions with gravity force parallel to the plane of motion is described. The experiments were run in a porous medium analog, the Hele‐Shaw model. A modification of the Saffman‐Taylor solution is compared with the experimental results. The arbitrary parameter in the solution, measured in the experiments, does not approach an asymptote but is a function of the ratio of plate spacing to channel height. In the course of the air‐water experiments three forms of the interface were observed before turbulence, which indicate regime changes in the flow. Finally, the effects of heterogeneities (change in plate spacing) on the interface were observed.
Development of the Scatchard‐Hildebrand and Wohl equations in terms of pair and triplet weighting functions
Authors: Wheeler Joe D. , Smith Buford D. 
Published: June 2004

AbstractA previous paper introduced the pair‐type‐probability (PTP) function for use in molecular corresponding states theory. The present paper develops the predictive equations of Scatchard and Hildebrand and the correlation equations of Wohl from particular pair and triplet weighting functions for clusters of two and three molecules in a liquid mixture. The cluster‐weighting idea therefore unifies the major prediction and correlation schemes now in engineering use.
Penetration theory for diffusion accompanied by a reversible chemical reaction with generalized kinetics
Authors: Secor R. M. , Beutler J. A. 
Published: June 2004

AbstractThe penetration theory equations representing diffusion with a generalized, reversible chemical reaction of the form γAA + γBB ⇌ γMM + γNN are solved by a finite‐difference method. Many solutions are presented in graphical form. Approximate solutions to several limiting cases are obtained analytically by means of a steady state representation and are useful for estimating results of the solution to the penetration theory equations.
The frequency domain evaluation of mathematical models for dynamic systems
Authors: Hays James R. , Clements William C. , Harris Thomas R. 
Published: June 2004

AbstractAn important problem in the mathematical modeling of dynamic systems is the testing of model applicability and the determination of the best model parameters through the minimization of the squared difference of the observed and predicted responses. This paper discusses the advantages of the transformation of the expression for the integral of the squared deviations ϕ to the frequency domain by the use of parseval's theorem. Two important advantages of the minimization of ϕ in the frequency domain are the ease with which the transform of the predicted response can be obtained and the algebraic nature of frequency domain operations. Other advantages are discussed and techniques for the numerical transformation and inversion of the observed and predicted responses are given.
Mass transfer with chemical reaction from single gas bubbles
Authors: Johnson A. I. , Hamielec A. E. , Houghton W. T. 
Published: June 2004

AbstractNumerical solutions of the equations that describe steady state, forced‐convection mass transfer around single circulating or noncirculating gas bubbles have been obtained for both first‐ and second‐order chemical reaction conditions. For the noncirculating bubbles, solutions have been obtained up to Reynolds numbers of 200 with Kawaguti velocity profiles used to describe the flow. In the case of circulating gas bubbles, Kawaguti profiles have been utilized up to Reynolds numbers of 80, while the potential flow velocity profiles have been used for higher Reynolds numbers. The numerical results for circulating gas bubbles have been compared with penetration theory for both first‐ and second‐order chemical reactions. For the case of noncirculating gas bubbles the solutions for physical mass transfer have been compared with the Ranz and Marshall correlation as well as with the results of Griffith and the more recent work of Tsubouchi and Masuda.
The relationship between transport properties and rates of freeze‐drying of poultry meat
Authors: Sandall Orville C. , King C. Judson , Wilke C. R. 
Published: June 2004

AbstractControlled studies have been made of unidirectional freeze‐drying of turkey meat. The results provide a test of the model of a uniformly retreating ice front. Comparisons are made with independent measurements of thermal conductivity and with the predicted effect of pressure level upon diffusivity. Variables explored include the pressure and humidity of the drying chamber, the meat surface temperature, and the grain orientation. Drying rates were measured in the presence of water vapor alone and also in the presence of 0 to 760 mm. Hg of nitrogen or helium. Nitrogen and helium runs were made both with a stagnant gas phase and with a circulating gas stream. The rates show quantitative agreement with the uniformly retreating ice front model during the removal of most of the moisture.
Effect of the resonance parameter on a chemical reaction subjected to ultrasonic waves
Authors: Aerstin Franklyn G. P. , Timmerhaus Klaus D. , Fogler H. Scott 
Published: June 2004

AbstractExperimental results are presented which indicate that the application of a fixed intensity of ultrasonic waves to a water‐tetrachloride solution containing dissolved air provides yields of chlorine varying from zero to maximum simply as a function of the liquid height in the capillary above the transducer. The difference in heights of the liquid between zero and maximum yields is found to be equal to one‐quarter the wavelength of the ultrasonic wave in the liquid. A mathematical model to explain this phenomenon is presented.
A generalized model for the dynamic behavior of a distillation column
Authors: Tetlow N. J. , Groves D. M. , Holland C. D. 
Published: June 2004

AbstractThe generalized model accounts for the effects of channeling, transfer lag, mixing, and mass transfer that occur on each plate of a column in the process of separating a multi‐component mixture at unsteady state operation. The equations required to describe the model were tested by solving a wide variety of numerical examples. Selected numerical results are presented to demonstrate certain characteristics and uses of the generalized model.
Model‐reference adaptive control system
Authors: Casciano Robert M. , Staffin H. Kenneth 
Published: June 2004

AbstractAn adaptive process control scheme—which uses a differential equation model, requires no differentiations in the adaptive circuitry, and no identification of the varying process parameter—was analyzed mathematically and studied on an analog computer. The adaptive loop is operative only during a transient and corrects only in the direction of mismatch between the process and model. Linear analysis of the system differential equations when the correction signal is not introduced into the controller provides a means of designing the adaptive circuitry and approximating the effect when the signal is introduced. The effects on system stability with a pure delay, measurement lag, or an additional pole in the process are presented. Computer results show that when large differences exist between the actual process time constant and the original controller setting, the adaptive feature reduces the overshoot to essentially zero.
Friction factors and pressure drop for sinusoidal laminar flow of water and blood in rigid tubes
Authors: Hershey Daniel , Song Geasoon 
Published: June 2004

AbstractFrom the Navier‐Stokes equations and a modified Fanning equation, a theoretical equation was derived for computing friction factors and pressure drop for sinusoidal flow in rigid pipes. The friction factor equation was f = (π/16S) (16/NRe), which is analogous to the usual laminar flow equation. The factor S is dependent on the frequency and kinematic viscosity and is easily computed. Friction factors were calculated from experimental data and it was found that the theoretical friction factors predicted the experimental values to within less than 5%.
An investigation of solids distribution, mixing, and contacting characteristics of gas‐solid fluidized beds
Authors: Halwagi M. M. El , Gomezplata Albert 
Published: June 2004

AbstractThis two‐part series describes an integrated experimental investigation. The first part is concerned with the determination of axial and radial solids concentration profiles at different superficial gas velocities for three columns having I.D. of 2.5, 6.5, and 9.5 in. respectively. The second part is concerned with steady state point source gas tracer experiments carried out in the 9.5‐in. column and in which the tracer concentration was measured at different radial positions above and below the injection source at various gas velocities Both parts are complimentary to each other for describing the internal flow behavior of the gas‐solid fluidized system.
Constant total pressure evaporation with heat reuse by a built‐in engine
Authors: Cheng Chen‐Yen , Cheng Sing‐Wang 
Published: June 2004

AbstractA new way of promoting a nonspontaneous process, namely, a built‐in engine, is introduced showing that a process with a large temperature coefficient of free energy change [that is, d(ΔG)T,P/dT] can be utilized to promote a nonspontaneous process which has a small temperature coefficient of free energy change. When such a built‐in engine is incorporated into an evaporating system, heat reuse in the system can be obtained under a constant total pressure condition.An auxiliary system consisting of two organic substances which are partially miscible in a certain temperature range and have a critical solution temperature can be used to serve as a built‐in engine. One substance is added to the boiling mass of an evaporator to lower its boiling temperature, and the other is added to the condensing side to raise the temperature of the condensing mass. Heat of condensation can be effectively utilized in evaporating the boiling mass. Regeneration of the auxiliary system is achieved by taking advantage of the solubility gap.
Concentrated polymer solution: Part II. Dependence of viscosity and relaxation time on concentration and molecular weight
Authors: Williams Michael C. 
Published: June 2004

AbstractA previouly presented molecular theory for non‐Newtonian viscosity in moderately concentrated polymer solutions is extended here to a specific consideration of the influence of solute concentration c and molecular weight M on the limiting viscosity ηo and the relaxation time λ. Estimates of the M,c dependence of several intermediate functions are necessary including that of Kirkwood's friction coefficient. The prediction ηo ∼ (cM0.625)2 is in good agreement with the empirical observation that ηo is a function of the parameter cM0.68, but is inadequate for extremes of M and c. Plausibility arguments are advanced to suggest λ ∼ ηoc−2 rather than λdil. ∼ Mηoc−1 predicted by dilute solution theory and widely accepted. This would explain the utility of the factor c2 used in recent rheological correlations, and would reconcile some conflicting reports of λ(M) measurements.
External flows of viscoelastic materials: Fluid property restrictions on the use of velocity‐sensitive probes
Authors: Metzner A. B. , Astarita Gianni 
Published: June 2004

AbstractThe more pronounced macroscopic features of flows of viscoelastic materials around submerged objects are considered in the light of restriction imposed on the flow by the Deborah number, a dimensionless group representing a ratio of time scales of the fluid and the flow process. It is seen that one major effect is to thicken the boundary layer appreciably in the region of the leading edge or stagnation point of the object in the fluid; depending on the shape of the object this thickening of the boundary layer may be felt for appreciable distances into the velocity field.The influence of these and other effects on the use of probes for determination of point values of the velocity of viscoelastic fluids is considered in some detail. The general effect is to impose strong restrictions on the use of such probes and on the interpretation of measurements made with them. These predicted limitations are supported, in a general way, by recent experimental measurements; thus the present macroscopic analysis appears to define several major effects to be considered in subsquent, more detailed investigations.