bluuebunny/crossref_metadata_2025_split huggingface dataset:
Turbulent dispersion in drag‐reducing fluids
Authors: Taylor A. Richard , Middleman Stanley 
Published: June 2004

AbstractTurbulent pipe flow was examined by measuring the radial dispersion of dyed fluid introduced at an axial point source within the flow. From the classical theoretical results of G. I. Taylor it was possible thereby to calculate various parameters that characterize the structure of the turbulent flow field. A comparison was made between water, and aqueous solutions of polyethylene oxide (Polyox) at concentrations up to 50 ppm (by weight). Results indicate that Polyox affects the turbulence in the following ways: (1) intensity is reduced, (2) the energy spectrum is shifted toward low frequency, (3) dispersion occurs largely through large scale motion, and intermittency is increased. Indication is also seen that a simple exponential form for the Lagrangian correlation coefficient is superior to other often recommended models.
Quadratically convergent techniques in linearly constrained optimization
Authors: Husen Gregory J. , Eakman James M. 
Published: June 2004

AbstractMethods for the solution of linearly constrained optimization of a nonlinear objective function are presented and compared. The methods of Fletcher‐Reeves, Fletcher, and Powell are used to generate search directions in the decision variable space. Generalized Kuhn‐Tucker conditions are presented and used to check for a local minimum.
Growth rate of an ice crystal in flowing water and salt solutions
Authors: Vlahakis John G. , Bardhun Allen J. 
Published: June 2004

AbstractThe growth rate of an ice crystal in the basal plane has been measured in subcooled water flowing at velocities of 0.04 to 1 cm/s to test a theory of Fernandez and Barduhn (1967). The theory fits the data in pure water at all velocities and subcoolings studied here and at velocities up to 46 cm/s studied previously. The interfacial tension between ice and water calculated from these data is 33 ± 6 ergs/cm2, a value in good agreement with those determined by others.Measured growth rates of ice from solution do not follow the theory and in fact are as much as 150% higher in 0.5 to 1% NaCl solution than in pure water. High subcoolings and low flow velocities accentuate this anomaly.
Diffusion in nickel oxide pellets–effects of sintering and reduction
Authors: Kim K. K. , Smith J. M. 
Published: June 2004

AbstractDiffusion rates were measured at 25°C and 1 atm by a steady state method in pellets of nonporous nickel oxide particles in order to determine the effects of sintering and chemical reduction. Sintering led to a striking decrease in diffusion flux; tortuosities above 100 were found for highly sintered (porosity 0.03) pellets. Reduction caused a sharp increase in diffusion rate when the original pellet was highly sintered. For an originally unsintered pellet the diffusion rate decreased with extent of reduction.These phenomena were explained quantitatively by using: (1) the random pore model to predict tortuosity factors for an unsintered, unreduced pellet, and (2) the extent of pore interconnections and the fractional reduction to treat the effects of sintering and reduction. In this way an approximate, predictive equation was derived which contained no arbitrary parameters and which required for application only data on porosity and extent of chemical reduction.
Growth of nickel sulfate in a laboratory‐scale fluidized‐bed crystallizer
Authors: Phillips V. Roger , Epstein Norman 
Published: June 2004

AbstractGrowth and dissolution rates of nickel sulfate α‐hexahydrate were measured as functions of the concentration driving force in a laboratory‐scale fluidized‐bed crystallizer for the temperature range 35° to 50°C and the crystal size range 0.5 to 4.0 mm.Dissolution rates at a given temperature and crystal size were first order in the concentration driving force. Growth rates were about one‐quarter of dissolution rates and depended on a higher exponent (around 1.3) of the concentration driving force. This exponent was not significantly affected by variations in crystal size, but decreased as temperature increased. The apparent variation of growth rate itself with crystal size at constant temperature was slight. Growth rates were found to be insensitive to solids concentration.
Surface diffusion of stearic acid on aluminum oxide
Authors: Yang Ralph T. , Fenn John B. , Haller Gary L. 
Published: June 2004

AbstractBy means of infrared internal reflection spectroscopy we measured the time dependence of the surface concentration of stearic acid molecules over a well defined region of the surface. The molecules were diffusing into this region from a source comprising a compressed monolayer or bulk crystalline material outside the field of view. By these measurements in conjunction with solutions to the diffusion equations we determined the diffusion coefficient Ds of stearic acid on the (0001) plane of α‐alumina. We also determined the dependence of Ds upon the amount of water coadsorbed on the surface. When the surface was free of reversibly adsorbed water, Ds had a value of about 2 × 10−7 cm2/s. As the surface coverage of coadsorbed water increased to about a monolayer Ds increased to a maximum value of about 4 × 10−5 cm2/s. With further additions of surface water Ds then decreased and became less than 10−8 cm2/s at coverages slightly less than about two monolayers. In the region of its maximum value the temperature dependence of Ds indicated an activation energy for the diffusion process of about 26 kcal/mole.
Single‐phase chromatography: Solute retardation by ultrafiltration and electrophoresis
Authors: Lee H.‐L. , Reis J. F. G. , Dohner John , Lightfoot E. N. 
Published: June 2004

AbstractIt is suggested that chromatographic separations can be performed very effectively in the absence of a stationary sorbent phase by using small diameter tubes or tube bundles for the column and segregating the solutes radially into the slower moving fluid near the tube walls. Separation is achieved by differential solute retardation whenever the degree of segregation is different for the various solute species present.An approximate analysis and preliminary experimental studies demonstrate the feasibility of using ultrafiltration through the tube wall to achieve solute separation. Preliminary estimates based on our ultrafiltration analysis also show that segregation by electromigration is very promising for electrically charged solutes.
Laboratory reactors and their limitations
Authors: Weekman Vern W. 
Published: June 2004

AbstractChoosing the type of laboratory reactor for evaluating process kinetics may be the most crucial step in an industrial process development program. Not only would a wrong choice result in expensive delays, but data may be obtained which would scale‐up erroneously, leading to a disastrous commercial design. Some of the pitfalls and limitations of various laboratory reactors are discussed for some typically complex industrial reaction systems. A modus operandi is suggested for choosing from among the potential reactors those that have the best chance of supplying the desired data. As is typical of many complex industrial reaction systems, no one reactor turns out to be ideal and many times the building of two or more types is advantageous.
Determination of the kinetics of secondary nucleation in batch crystallizers
Authors: Kane S. G. , Evans T. W. , Brian P. L. T. , Sarofim A. F. 
Published: June 2004

AbstractThe kinetics of secondary nucleation have been determined from measurement of the supersaturation as a function of time following the addition of seed nuclei to a supercooled solution in a well‐stirred batch crystallizer. Population balance mathematics have been used to show that the secondary nucleation kinetics may be inferred from the supersaturation‐time curve. The method has been applied to the determination of the kinetics of the secondary nucleation of ice and found to give results in excellent agreement with those obtained from tedious particle counts. In addition, it has been shown that the moment of the particle size distribution that best correlates the nucleation rate data can be inferred from the initial transient of the supersaturation‐time history.
Mass transfer in laminar flow between parallel permeable plates
Authors: Walker Gary , Davies Terence 
Published: June 2004

AbstractSolutions for the concentration profiles and mass transfer rates are found for various wall Sherwood numbers. Use is made of the confluent hypergeometric function in the solution, and its advantage over the previously used series solution is pointed out. Perturbation solutions are also presented for both large and small values of the wall Sherwood number.
Trajectory calculation of particle deposition in deep bed filtration: Part I. Model formulation
Authors: Payatakes Alkiviades C. , Tien Chi , Turian Raffi M. 
Published: June 2004

AbstractThe packed bed model developed by Payatakes, Tien, and Turian (1973a, 1973b) is used as a basis for the study of particle deposition in deep bed filtration. The size of the particulate matters present in the suspension is assumed to be sufficiently large for Brownian motion to be negligible, but small enough for straining to be unimportant. The prediction of the rate of particle deposition is based on the one‐step trajectory approach. The collector is represented by a unit bed element of the porous media model and the particle trajectory equation is formulated to include the gravitational force, the hydrodynamic force and torque (including the correction for the presence of the unit cell wall), the London force (including the retardation effect, which is shown to be of primary importance under conditions usually met in deep bed filtration systems), and the electrokinetic force. Sample capture trajectories, including the limiting capture trajectories, are given.Based on the limiting trajectories and the assumption of uniform particle distribution at the entrance of each unit cell, the number fractions (of suspended particles) impacted on each unit cell are determined and then used to calculate the fraction impacted on the entire unit collector and also the value of the filter coefficient for a clean bed. It is also shown how the capture trajectory calculation can be used to determine the local rate of deposition along the wall of a given unit cell.
Bisphenol a synthesis: Kinetics of the phenol‐acetone condensation reaction catalyzed by sulfonic acid resin
Authors: Reinicker R. A. , Gates B. C. 
Published: June 2004

AbstractThe industrially important reaction of phenol and acetone to give bisphenol A and water was catalyzed by beads of ion‐exchange resin (sulfonated styrene‐divinylbenzene copolymer) suspended in a batch reactor containing liquid reactants. The data are summarized by a rate equation accounting for reaction in the resin competitively swollen by water, acetone, phenol, and methylcyclohexane.The catalyst is modeled as two phases, each in equilibrium with the liquid: a polar phase consisting of sulfonic acid groups with hydrogeb–nonded acetone and water and a nonpolar phase consisting of the hydrocarbon matrix swollen with organic components. The rate determining step is the electrophilic attack on phenol in the nonpolar phase by a carbonium ion intermediate in the polar phase.Resin cross‐linked with 4% divinylbenzene initially catalyzed acetone conversion at a rate of 5 × 10−4 (moles)/(equiv of acid groups s) at 364°K. An 8% cross‐linked resin was much less active because the rigid polymer matrix was only slightly swollen by phenol, but a more highly cross‐linked resin with macropores and accessible internal surface catalyzed reaction almost as rapidly as the 4% cross‐linked catalyst.
Separations with protein liquid crystals
Authors: Kozinski A. A. , Kizior G. J. , Wax S. G. 
Published: June 2004

AbstractA lyotropic protein liquid crystal was studied experimentally to evaluate its potential as a selective liquid membrane. Concentrated solutions of fibrinogen had nematic like properties under shear and exhibited graded selectivities toward solutes of widely differing sizes when subjected to a two‐dimensional velocity field. The magnitude of the selectivity differences was found to depend on the shear orientated direction of the liquid crystal layer. The selectivity seems to be both a solubility phenomena and a relative diffusion phenomena. These anisotropic layers may have potential as controlled variable selectivity membranes.
Surface diffusion in liquid‐filled pores
Authors: Komiyama Hiroshi , Smith J. M. 
Published: June 2004

AbstractSurface diffusivities of benzaldehyde in liquid‐filled pores of Amberlite particles (polystyrene) were measured at 25°C using water as a solvent. For particles of different surface areas but chemically similar pore surfaces, the intrinsic surface diffusivity Ds' was about the same, but the relative importance of surface to pore‐volume diffusion increased with surface area. For a single type of particle, the adsorption capacity was decreased about twenty‐fold by adding up to 19 mole % methanol to the solvent. This was accompanied by an increase in Ds' from 1.2 × 10−8 to 1.2 × 10−7 cm2/s. These results were interpreted in terms of a two‐step theory for surface migration: (1) formation of a vacant site on the adsorbent surface followed by (2) movement of the adsorbate molecule into the site by breaking the surface‐adsorbate bond. The theory predicts that surface transport will be large when the surface area is high and that the Ds' will be large when the heat of adsorption is low, and when the bond between solvent molecules and the surface is weak.In our studies the surface contribution to intraparticle transport was as much as 20 times the contribution due to pore‐volume diffusion. This ratio increases as the concentration of adsorbate in the liquid decreases.
On the optimization of distributed parameter systems with boundary control: A counter example for the maximum principle
Authors: Gruyaert F. , Crowe C. M. 
Published: June 2004

AbstractA counterexample is given to the strong maximum principle for boundary control of a class of distributed parameter systems. The particular system deals with chemical reactors suffering catalyst decay and is in the class whose members are described by sets of first‐order partial differential equations of the hyperbolic type. It is shown that an optimal control exists and that over any finite time interval in which the control is unconstrained the exit conversion from the reactor remains constant. It is further shown that for certain values of the parameters the optimal control policy violates the necessary conditions of the strong maximum principle for boundary control of distributed parameter systems.
Synthesis of fault tolerant reaction paths
Authors: Powers Gary J. , Cummings Daniel L. , Rathore Ram N. S. 
Published: June 2004

AbstractThe problem of synthesizing an optimal low risk reaction network from unreliable reactions is formulated. An expected cost criterion function for decision‐making is derived both for the case of a continuously operating network of reactions and for the case of reaction paths that involve batch reactions. It is shown that in general the decision space has a nonserial structure and the search for the optimal path will involve use of network search methods. An example is given where the optimal reaction path is synthesized for deoxyribonucleic acid. This example demonstrates the decision‐making strategy for a class of bath reaction systems.
Mass transfer studies across liquid/liquid interfaces (use of an analytical ultracentrifuge)
Authors: Chandrasekhar Sivam , Hoelscher Harold E. 
Published: June 2004

AbstractExperimental data have been obtained using an Analytical Ultracentrifuge, in regions much closer to the interface in immiscible liquid/liquid systems than have hitherto been reported. The water/toluene system was investigated with acetic and propionic acids as the transfer solutes. The direction of mass transfer was from the water to the toluene phase. The data derived from the study indicates that the maximum mass transfer flux in the water/toluene system occurs, not at the interface, but at regions further away from it and that the water/toluene system offers significant interfacial resistance of about 104 s/cm to the transfer of acetic and propionic acids. The water/n‐butanol system was also studied and found to offer negligible resistance to the transfer of acetic acid across the interface.Diffusion coefficients for ethylene glycol, glycerol, and n‐butanol in water were also determined with the Ultracentrifuge. The values derived in this study were reproducible to within 5% and were in close agreement with those derived from classical diffusion experiments.
Two kinds of self‐preserving size spectra of a cloud of particles
Authors: Pulvermacher B. , Ruckenstein E. 
Published: June 2004

AbstractThe population balances describing the time dependence of the size distribution can, under some conditions, be trasformed by means of a similarity transformation into an ordinary integro‐differential equation containing two instead of three variables. If there is compatibility between the transformed equation and the constraints given by the total mass conservation equation and the equation for the total number of particles, a self‐preserving spectrum of the first kind can be obtaiened. There are, however, many situations such as the sintering controlled aging of supported metal catalysts, coagulation of colloidal particles in laminar shear flow, and coagulation of colloidal particles in a turbulent flow when the particles are smaller than the size of the smallest eddy for which, although a similarity transformation is possible, the transformed equation has no solution because of incompatibility with the above mentioned constraints. A second kind of self‐preserving spectrum is suggested for these situations. The new variables are induced from a particular case for which an analytical result is available. A detailed presentation of the sintering controlled aging of supported metal catalysts is presented.
Wall mass transfer in laminar pulsatile flow in a tube
Authors: Patel Rutton D. , McFeeley John J. , Jolls Kenneth R. 
Published: June 2004

AbstractWall mass transfer was measured in fully developed pulsating laminar flow in a tube using the diffusion‐controlled electrode technique. The average Reynolds number, pulsating frequency and amplitude, and length of the mass transfer surface were the independent variables studied. The results are given in the form of the amplitude ratio and phase angle of the pulsating wall transfer rate. At lower frequencies the amplitude and phase were found to be correlated by the variable ωd2 Gz−2/3 in accordance with theory. At higher frequencies an empirical correlation with the variable ωd2 Gz−1/3(L/D)1/3 was found. While this may show some deficiency in the usual theoretical model, it is also possible that other causes such as nondevelopment of the flow are responsible. Time‐averaged transfer rates were found to be only slightly different from the corresponding steady flow transfer rates in the range of variables investigated.
Natural convection with mercury in a uniformly heated vertical channel during unstable laminar and transitional flow
Authors: Humphreys William W. , Welty James R. 
Published: June 2004

AbstractExperimental heat transfer correlations were determined for natural convection in mercury in a uniformly heated vertical channel with width‐to‐height ratios varying from 0.25 to infinity (the single plate limit). Local modified Grashof numbers varied between 108 and 1011. Temperature and velocity profiles were obtained for these same channel configurations and local Grashof numbers. Instantaneous velocity plots indicate the range of conditions studied to proceed from unstable laminar flow well into the transition regime. Heat transfer results are in good agreement with earlier results reported for stable laminar flow which were limited to values of modified Grashof number less than 109.
Steady state chemical process simulation
Authors: Motard R. L. , Shacham M. , Rosen E. M. 
Published: June 2004

AbstractIn recent years process simulation by computer has become an accepted tool in the design and control of chemical processes, but there are still uncertainties and conflicting views about the real benefits relative to cost in both chemical industry and in education.This article surveys the literature of the last three years, exploring the answers to the question: How has chemical process simulation by computer fulfilled expectations in industry and education and what are the major areas of research identifiable at this time?It is concluded that process simulation remains a very dynamic field with a continuous expansion in the areas of application and in the number of users. New subjects requiring research are replacing older areas which have matured.
Quantitative overdesign of chemical processes
Authors: Freeman R. A. , Gaddy J. L. 
Published: June 2004

AbstractOverdesign is applied to chemical processes to account for expected variations in the design data or design conditions. These variables must be treated quantitatively in order to design a process that is certain to perform adequately. Process dependability is introduced as a means of quantifying variable process behavior. Overdesign using the dependability criterion is a stochastic optimization problem. An example problem with three stochastic variables and two design variables is presented to illustrate these procedures.
The behavior of a power‐law fluid flowing through a sudden expansion. Part II. Experimental verification
Authors: Halmos A. L. , Boger D. V. 
Published: June 2004

AbstractExperimental data are presented to verify the numerical model discussed in Part I. The experimental techniques employed for recovering flow patterns and for point velocity measurement are described and justified. The measured reattachment lengths, the recorded flow patterns, and the developing axial velocity field all show excellent agreement with the model predictions.
Sulfur dioxide oxidation in slurries of activated carbon. Part II. Mass transfer studies
Authors: Komiyama Hiroshi , Smith J. M. 
Published: June 2004

AbstractBubble‐to‐liquid, liquid‐to‐particle, and intraparticle mass transport effects were all found to be significant for some conditions in a three‐phase slurry reactor operated for the oxidation of SO2 at 25°C and 1 atm. In particular, intraparticle diffusion was important for particles as small as 99 microns (effectiveness factor = 0.45).Effective diffusivities determined from reaction, desorption, and adsorption data for O2, H2SO4, and SO2 indicated that surface diffusion was appreciable for SO2 but not for oxygen. These results are consistent with the kinetic results in Part I which suggested that the rate‐controlling step was a chemisorption process for oxygen on the pore surface of the carbon particles.
Process reliability analysis
Authors: Henley Ernest J. , Gandhi Satish L. 
Published: June 2004

AbstractThis paper presents a unified approach for obtaining system reliability and availability parameters from block diagram representations of process systems. It starts with computer algorithms for obtaining the minimal paths in a system, then shows how this information can be combined with unit reliability data to obtain the overall system reliability, and the response of system reliability to changes in unit reliability (sensitivities). It then demonstrates how these sensitivities can be used to optimize the system reliability and availability by equipment redundancy. Extension of the methodology to the automated production of system fault trees as well as the mathematical relationship between fault trees and block diagrams are noted.