bluuebunny/crossref_metadata_2025_split huggingface dataset:
On filtering in delay systems with continuous dynamics and discrete‐time observations
Authors: Padmanabhan L. 
Published: June 2004

AbstractFilter equations for linear delay systems with continuous‐time dynamics and discrete‐time measurements are derived by separating the estimation problem into prediction between measurements and updating at a measurement. The result is the analog of the well‐known Kalman filter for the nondelay case. A computational technique for implementing the filter is indicated and illustrated by an example of a scalar system with a delay in the dynamics as well as measurement.
Determination of liquid‐mixture solubility parameters and interaction energy densities
Authors: Lui Peter C. K. , Donnelly Harold G. 
Published: June 2004

AbstractIntegral, isothermal heat‐of‐condensation values for continuously generated vapors of various constant‐composition mixtures, along with the isothermal densities of the condensates, enable the calculation of the cohesive energy densities of solutions. Data for the complete range of composition of the chloroform‐acetone system and for a major portion of the chloroformdiethyl ether system at 35°C are reported. From these data, the specificinteraction‐energy density for each system is calculated, based upon an extension of the Scatchard‐Hildebrand Regular Solution Theory.The essential equality of the specific‐interaction energy‐density values for the two systems indicates a preponderance of the same kind of hydrogen bonding (CH‐‐‐O) in each.
Enhancement of stagnation flow heat and mass transfer through interactions of free stream turbulence
Authors: Galloway T. R. 
Published: June 2004

AbstractAt the forward stagnation point of a bluff body the laminar flow is influenced by externally generated free‐stream turbulence, such as from grids, in such a way that heat and mass transport are significantly enhanced above their normal values. The basis of this enhancement is an unsteady, threedimensional flow pattern formed at the forward stagnation point and triggered or altered by the free‐stream turbulence. Such complex flows can be interpreted as roll cells oriented with their axes parallel to streamwise coordinates. Such roll cells have been observed by other investigators using special experimental visualization techniques. This complex flow was introduced into the momentum and transport equations, which were then solved numerically to produce the relationships between Nusselt, Reynolds, and Prandtl numbers and free‐stream turbulence. Not only were these relationships nearly identical with earlier established empirical correlations, but they revealed in addition a strong augmentation for high Prandtl number flows. Predictions in slurry flows around bluff bodies were also found to be reasonable.
Restricted diffusion in liquids within fine pores
Authors: Satterfield Charles N. , Colton Clark K. , Pitcher Wayne H. 
Published: June 2004

AbstractThe effect on the liquid‐phase effective diffusivity in fine pores of the ratio of solute molecular diameter to pore diameter and of preferential solute adsorption was studied by measurements on homogeneous silicaalumina bead catalyst (pore diameter = 3.2 nm). A proposed empirical correlation is based on the investigation of a variety of binary systems of paraffins and aromatic hydrocarbons and of aqueous solutions of sugars.
Adsorption and molecular association in the Burnett apparatus
Authors: Eubank Philip T. , Kerns William J. 
Published: June 2004

AbstractPhysical adsorption errors accumulate in the isothermal Burnett PvT apparatus. The equations describing this sequential phenomena plus diagnostic methods and correction procedures are given. Shift of the apparent volume ratio, the prinicipal indication of significant adsorption, is related to the difference between the surface and volume ratios. The effect of adsorption on the usual Burnett graphs follows from real and simulated data examples. Isochoric coupling as related to the adsorption problem is fully reviewed.Experiences with chemisorption are related and explained for the first time. Molecular association, which is properly measured by the Burnett apparatus, is compared to adsorption where the two phenomena coexist.
Wake phenomena in a liquid‐liquid fluidized bed
Authors: Yeheskel Jacob , Kehat Ephraim 
Published: June 2004

AbstractMeasurements of the size and rate of shedding of wakes of drops, average drop holdup and velocity of the continuous phase as functions of drop size for kerosene, hexane, and benzene dispersed in water in a liquid‐liquid fluidized bed are reported. The average drop size ranged between 3.3 and 4.8 mm. The water velocity was 5.0 to 12.05 cm/s. The average drop hold up was 0.065 to 0.560.The ratio of wake to drop volume was 0.2 to 2.4, and the rate of wake shedding, reported as time of wake transfer units, was 0.7 to 2.4. At low drop holdups, the effect of single drops and groups of drops is dominant. At high drop holdups, the effect of neighboring drops and wakes is dominant. The wake size is correlated with slip velocity and can be calculated from empirical holdup measurements.
Selective membrane transport
Authors: Reusch C. F. , Cussler E. L. 
Published: June 2004

AbstractCyclic Polyethers acting as mobile carriers in facilitated transport can cause changes of as much as three orders of magnitude in the fluxes of various cations across liquid membranes. The cyclic polyether dibenzo‐18‐crown‐6 (2,3,11,12‐dibenzo‐1,4,7,10,13,16‐hexaoxacyclooctadeca‐2,11‐diene) was used in this work to achieve such a large selectivity. The results show that a primary factor leading to the selectivity is the ratio of unsolvated cation radius to polyether central ring radius. The implication is that by selecting a polyether with a desired central ring radius, any two cations of slightly different radius can be separated efficiently.
Simultaneous heat and mass transfer from multicomponent condensing vapor‐gas systems
Authors: Schrodt J. Thomas 
Published: June 2004

AbstractMulticomponent vapor condensation in the presence of noncondensing gas has been analyzed using numerical solutions to a set of linearized rate equations that describe the simultaneous heat and mass transfer to the condensate film. For specific examples of methanol and water and ethanol and toluene condensing from turbulent air streams in vertical tube and on horizontal tube condensers, it is shown that the alcohol concentrations in both the liquid and gas phases increase as condensation from initially superheated, alcohol‐rich gas phases progresses; the liquid phases also become richer in alcohol. The mass fluxes of the vapors vary with their respective mass transfer coefficients and local concentration driving forces. In the vertical tube condensers, the flux of the alcohols go through maximums. Gas phase saturation is approached as the mixtures cool and the final traces of vapor become more difficult to condense. Interface properties are computed from limited VL equilibrium data, heat of solution data, and a predictive equation. The techniques of solution and analysis have general application to the design of cooler‐condensers in either vertical or horizontal configurations.
Optimization by direct search and systematic reduction of the size of search region
Authors: Luus Rein , Jaakola T. H. I. 
Published: June 2004

AbstractA direct search procedure utilizing pseudo random numbers over a region is presented to solve nonlinear programming problems. After each iteration the size of the region is reduced so that the optimum can be found as accurately as desired. The ease of programming, the speed of convergence, and the reliability of results make the procedure very attractive for solving nonlinear programming problems.
Momentum transfer through packed beds of various particles in the turbulent flow regime
Authors: Gauvin William H. , Katta Satyanarayana 
Published: June 2004

AbstractThe flow of air through packed beds of solid and hollow particles of a wide range of geometries was studied, with particular reference to the effect of the particle shape on the pressure drop in the turvbulent range. A method of analysis based on the concept of stagnant void fraction and the principle of drag additivity has been developed. Equations for estimating the stagnant voidages for various particle shapes arranged in a random pattern in a packed bed were derived. A new type of friction factor based on this approach was correlated satisfactorily with a shape factor. The momentum transfer data were also correlated with the sphericity of the particles.
Activity coefficients–aqueous solutions of polybasic acids and their salts
Authors: Meissner Herman P. , Peppas Nikolaos A. 
Published: June 2004

AbstractA method of predicting activity coefficients of polybasic acids and their salts in strong aqueous solutions is presented. Application of the calculation of decomposition pressures of SO2 over sodium sulfite‐bisulfite systems and of CO2 over carbonate‐bicarbonate systems is illustrated.
Interfacial areas of liquid‐liquid dispersions from light transmission measurements
Authors: McLaughlin C. M. , Rushton J. H. 
Published: June 2004

AbstractA mathematical model simulating light transmission through liquid‐liquid dispersions has been developed. Numerical solutions of the model for various drop size distributions show that the fraction of parallel light which passes through a dispersion is a unique function of a dimensionless group, here named the Transmission Number, regardless of the drop size distribution. The results, which were verified by actual light transmission experiments, show that the interfacial area of a liquid‐liquid dispersion can be calculated from a light reading provided that the light detector receives only parallel light. Application of the results to other two‐phase dispersions is indicated.
An experimental evaluation of Kalman filtering
Authors: Hamilton James C. , Seborg Dale E. , Fisher D. Grant 
Published: June 2004

AbstractThe effectiveness of the stationary form of the discrete Kalman filter for state estimation in noisy process systems was demonstrated by simulated and experimental tests on a pilot plant evaporator. The filter was incorporated into a multivariable, computer control system and resulted in good control despite process and/or measurement noise levels of 10%. The results were significantly better than those obtained when the Kalman filter was omitted or replaced by conventional exponential filters. In this application the standard Kalman filter was reasonably insensitive to incorrect estimates of initial conditions or noise statistics and to errors in model parameters. The filter estimates were sensitive to unmeasured process disturbances. However this sensitivity could be reduced by treating the noise covariance matrices R and Q as design parameters rather than noise statistics and selecting values which result in increased weighting of the process measurements relative to the calculated model states.
An experimental study of the control of condensate subcooling in a vertical condenser
Authors: Archambault Jean‐Paul , Jauffret Jean‐Paul , Luyben William L. 
Published: June 2004

AbstractTemperature control of subcooled reflux in a distillation column was studied experimentally using coolant flow rate as the manipulative variable. Methanol vapor was condensed and subcooled at one atmosphere in a vertical heat exchanger with 210 copper tubes (0.77 cm I.D., 91.5 cm long). Cooling water flowed countercurrently through the shell side (20.6 cm I.D.).A proportional‐integral feedback controller provided good temperature control at normal design throughputs. But dynamic control performance deteriorated at low throughputs (or large areas). Thus the normal conservative design practice of providing excess area in this type of condenser leads to poorer temperature control.
Radiation fields inside an elliptical photoreflector with a source of finite spatial dimensions
Authors: Cerd́a Jaime , Irazoqui Horacio A. , Cassano Alberto E. 
Published: June 2004

AbstractUsing the Extense Source Formulation (Irazoqui et al., 1973a), a radiation distribution model for the tubular lamp‐elliptical reflector system was developed for predicting energy density profiles inside the elliptical cavity of the system.It introduces a significant improvement over the linear‐lamp models since it avoids any form of singularities in the prediction of radiation energy density profiles at the focal points of the elliptical reflector. Also, all lamp and reflector dimensions are parameters of the model.Calculated results agree well with published experimental data for a similar lamp reflector set up.One of the most important conclusions is the absence of uniform irradiation from all radial directions at the reactor location.
Bubble‐free expansion of gas‐fluidized beds of fine particles
Authors: Donsì G. , Massimilla L. 
Published: June 2004

AbstractFive different fine powders with average particle size of about 100 microns or smaller were fluidized with air over their respective bubblefree ranges of fluidization. Photographs taken through the front transparent wall of the column showed that the beds contained cavities and microchannels whose sizes were of the same order of magnitude as the particle size. It is shown that interparticle van der Waals adn capillary forces play an important role in the bubble‐free expansion of small particles. Measurements of bed expansion and average particle drag coefficients are consistent with the proposed role of interparticle forces.
Independent reactions in the presence of isomers
Authors: Whitwell J. C. , Dartt S. R. 
Published: June 2004

AbstractIn reacting systems, the number of independent chemical reactions, the number of components, and the number of chemical chemical species are generally assumed to be so related that the sum of the first two equals the third. Standard methods of obtaining the number of independent reactions (that is, formation equations or rank of the element‐by‐species matrix) may fail when chemical isomers appear in reactant streams, product streams, or both. The errors encountered with various types of isomers are delineated in this paper along with corrective measures. The element‐by‐species matrix is judged to be more suitable as a starting point than formation equations when matrix size and number of manipulations are considered.
Topics in computer‐aided design: Part I. An optimum tearing algorithm for recycle systems
Authors: Pho T. K. , Lapidus L. 
Published: June 2004

AbstractThe concepts of ineligible streams and two‐way edge reduction are extended to simplify the signal flow diagram of a recycle process flow sheet graph. The solution to a tearing problem can be obtained readily by repeated reduction of ineligible streams and two‐way edges. When this fails, a branch and bound method will guarantee optimality at the expense of a few enumerations.
Compressibility factor of polar fluids in the gaseous and liquid regions
Authors: Stipp Gordon K. , Bai S. D. , Stiel Leonard I. 
Published: June 2004

AbstractThe tables of Pitzer et al. for the compressibility factor of nonpolar substances have been extended to polar fluids for the gaseous and liquid regions for reduced temperatures from 0.8 to 1.15 and reduced pressures from 0.2 to 6.0. Available experimental PVT data for polar fluids were related to the acentric factor and fourth parameter at constant reduced temperature and pressure by a quadratic least squares procedure. The resulting relationships reproduced the data utilized with good accuracy for the entire region considered.
Collision breeding: A function of crystal moments and degree of mixing
Authors: Desai R. M. , Rachow J. W. , Timm D. C. 
Published: June 2004

AbstractAn experimental procedure based on continuous crystal seeding was developed which can explicitly determine the fundamental relationship between collision breeding and the leading moments of the crystal size distribution. For the aqueous, cooling crystallization of potassium dichromate, the analysis determined that only the mass moment was successful in correlating observations subject to crystal seeding.It was also observed that mixing may have a pronounced effect on the nucleation rate but that kinetic orders for collision breeding and growth rate were independent of mixing.
Influence of mixing on the performance of periodic chemical reactors
Authors: Lee C. K. , Bailey J. E. 
Published: June 2004

AbstractThe interaction between imperfect mixing and cyclic operation is examined for several continuous polymerizations in stirred‐tank reactors. The reactor is represented by a mixed model involving two interconnected ideal stirred vessels. Cyclic fluctuations in the concentration of a chain transfer agent during Ziegler‐catalyzed olefin polymerization can yield molecular weight distributions significantly different from those of a conventional steady state reactor. This result is consistent with the available experimental data. It is especially interesting that the cyclic reactor effluent with a modified molecular weight distribution is of approximately time‐invariant composition when the period of cycling is on the order of the reactor holding time. Imperfect mixing has a lesser effect on cycled reactors for free‐radical and polycondensation polymerization than it has on cycled olefin polymerization reactors.
Analysis of fixed bed sorption: Flue gas desulfurization
Authors: Bourgeois Sidney V. , Groves Frank R. , Wehe Albert H. 
Published: June 2004

AbstractTemperature and concentration profiles are obtained by solution of the coupled nonlinear differential equations which describe transient operation of an adiabatic fixed bed reactor. The unreacted‐shrinking core mechanism describes the multiple, irreversible, exothermic gas‐solid reactions. Numerical integration is accomplished by a predictor‐corrector scheme which is programmed in Fortran IV language. The influence of kinetic parameters, heat and mass diffusivities within pellets, temperature variation of properties, gas velocity, bed and particle dimensions, inlet gas temperature and composition, and initial bed temperature on reactor performance are studied for sulfur dioxide removal from flue gases by fixed beds of copper oxide. Comparison with commercial reactors is in qualitative agreement.
Generalized f/P, ZT and ZP values for liquids at low reduced temperatures
Authors: Hsi Chu , Lu Benjamin C.‐Y. 
Published: June 2004

AbstractThe three‐parameter correlation of Pitzer et al. for fugacity coefficients (f/P) has been extended to liquids in the 0.5 ≤ Tr ≤ 0.8 and 0.2 ≤ Pr ≤ 9.0 region. In addition, values of the derivative compressibility factors ZT and ZP have also been obtained in the same region. This extension is based on the generalized correlation of the compressibility factor Z recently reported. The isothermal coefficient of bulk compressibility βT compiled by Rowlinson has been employed with the pressure effect on βT taken into consideration. The correlation for f/P obtained in this work is compared with that of Curl and Pitzer at Tr = 0.8, Chao et al. at Tr from 0.50 to 0.70, and that of Carruth and Kobayashi in the 0.50 ≤ Tr ≤ 0.64 region. Using the tabulated ZP and ZT values \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{H^* - H}}{{T_c }},{\rm }\left ({\frac{{\partial V}}{{\partial P}}} \right)_T $\end{document}, and \documentclass{article}\pagestyle{empty}\begin{document}$ \left ({\frac{{\partial V}}{{\partial T}}} \right)_P $\end{document} have been calculated and compared satisfactorily with the corresponding values derived from literature data. In addition, a correlation of vapor pressures of both hydrocarbons and nonhydrocarbons is also presented. The agreement between this correlation and those reported by Pitzer et al. and Carruth and Kobayashi is very satisfactory.
A simple algorithm for the time‐optimal control of chemical processes
Authors: Beard John N. , Groves Frank R. , Johnson Adrain E. 
Published: June 2004

AbstractA simple algorithm for the time‐optimal control of chemical processes during setpoint changes, in processes which can be described by a second‐order lag plus dead time model, is described. Knowledge of the unsteady state model parameters is not required because the algorithm uses a dimensionless phase plane on which the switching curves are independent of system parameters for a given forcing function. The algorithm gives the parameters of a second‐order lag plus dead time model as a by product of the setpoint change. It is easily tuned and is relatively insensitive to changes in the process dynamics. The algorithm does not require a large computer or long computing times and has been implemented on both analog and digital computers in controlling computer simulated systems.
Coagulation of lead chloride aerosol in the presence of water vapor
Authors: Ranade M. B. , Wasan D. T. , Davies R. 
Published: June 2004

AbstractPolydisperse submicronic lead chloride aerosols were generated from melt phase under dry and humid conditions. The particle size and concentration increased with increasing generation temperature. The aerosol particles generated in a dry atmosphere were pherical while the aerosol particles generated in humid atmosphere showed development of crystallinity at the surface.Coagulation rates of the aerosol generated in a dry atmosphere were measured at room temperature under different humidities. The coagulation rates were in goodagreement with Smoluchowski's theory, modified to include the effect of polydisperisity and were unaffected by humidity. The interaction of lead chloride particles with the water vapor was characterized by a process of adsorption a the interfce. The coagulated aerosol exhibited a chain structure for humidities lower than 70% and, at higher humidities, compact agglomeration was observed.
Fault tree synthesis for chemical processes
Authors: Powers Gary J. , Tompkins Frederick C. 
Published: June 2004

AbstractThis paper outlines the concepts for a systematic approach to the safety analysis of chemical processing systems. A procedure for automatically generating fault trees is presented. The fault trees describe nearly all the failure modes for the system under analysis. The fault tree generation procedure uses information on (1) the description of the system (detailed flowsheet), (2) physical and chemical properties of materials in and around the system, and (3) unit models which describe the behavior of the units within the system and which are assembled to describe the behavior of the complete system. The unit models are connected to form an information flow structure for the complete processing system. Unit failure models are also defined for common chemical units. By systematically defining hazard states and searching the information flow structure for the system, it is possible to generate fault trees for the complete process. An analysis of the fault trees can reveal the important failure modes for the process.
Facilitated transport via carrier‐mediated diffusion in membranes: Part I. Mechanistic aspects, experimental systems and characteristic regimes
Authors: Schultz Jerome S. , Goddard Joe D. , Suchdeo Shyam R. 
Published: June 2004

AbstractCarrier‐mediated transport in membranes as a globally nonreactive process is distinguished from film theory with chemical reaction and other facilitated diffusion phenomena. With the concept of stoichiometric and system invariants, an approach is developed for the analysis of carriersediated transport with multiple permeants involving multiple reactions in the membrane. Approximate solutions of the requisite differential equations according to the relative importance of diffusion and reaction rates are reviewed, as well as typical experimental studies. Criteria for evaluating whether a membrane is in the diffusion or equilibrium regime are given, and, in the latter case, the effects of some system parameters are given, for example, binding constants, competitive permeants.