bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental evaluation of nonisotheral solid‐gas reaction model
Authors: Wang S. C. , Wen C. Y. 
Published: June 2004

AbstractThe nonisothermal unreacted‐core‐shrinking model with unsteady state heat transfer analysis has been experimentally evaluated. The system studied is the combustion of a single agglomerated carbon‐fire clay sphere in a thermobalance. By comparing the experimental results with those predicted by the model, it is concluded that the model adequately describes the reaction system under the experimental conditions such that the ash layer diffusion is rate controlling.
Dynamics of moisture diffusion through a partially liquid filled porous matrix
Authors: Murty B. G. K. , Gidaspow Dimitri , Roy Dipak 
Published: June 2004

AbstractModels for unsteady water transport in fuel cell configurations of Bacon‐Pratt and Whitney type are derived. Tests with a specially constructed isothermal cell producing no water and order of magnitude analysis show that diffusion through the liquid alone cannot account for the observed behavior. An analytical solution which includes diffusion in both the liquid and the gas spaces of the matrix is in better agreement with the data than models which consider diffusion in either the liquid or in the gas phase alone.
A new model for granular porous media: Part I. Model formulation
Authors: Payatakes Alkiviades C. , Tien Chi , Turian Raffi M. 
Published: June 2004

AbstractA new model for porous media comprised of monosized, or nearly monosized grains, is developed. In applying this model to a packed bed, the bed is assumed to consist of a series of statistically identical unit bed elements each of which in turn consists of a number of unit cells connected in parallel. Each unit cell resembles a piece of constricted tube with dimensions which are random variables. The problem of flow through each unit cell is reduced, subject to reasonable assumptions, to the determination of the flow in an infinitely long periodically constricted tube. The solution of this flow problem is given in a companion publication. This model, together with the solution of the flow through it, can be used for the modeling of processes which take place in the void space of a bed.As a preliminary test, theoretical friction factor values, based on the proposed model, were compared with experimental ones for two different beds and found to be in good agreement even in the region of high Reynolds numbers where the nonlinear inertia terms are significant.
Liquid densities and liquid enthalpies of hydrogen‐containing hydrocarbon mixtures
Authors: Chueh P. L. , Deal C. H. 
Published: June 2004

AbstractHydrogen, a quantum gas, raises to unique problemsin the estimation of liquid properties of mixtures containing dissolved hydrogen–a problem often encountered in hydroprocessing of hydrocarbons. The liquid density and enthalpy of a hydrogen‐containing mixture in particular are not adequately described by the pseudocritical concept but are best calculated by summing the liquid partial molar quantities of hydrogen and that of hydrogen‐free liquid solvent.Liquid partial molar volumes and enthalpies of hydrogen have been evaluated and the results, including the effects of pressure and composition, presented in generalized equations. These generalized equations are shown to be useful in estimating the liquid density and enthalpy of hydrogen containing mixtures.
Liquid‐vapor equilibria at 112.00 K for systems containing nitrogen, argon, and methane
Authors: Miller R. C. , Kidnay A. J. , Hiza M. J. 
Published: June 2004

AbstractLiquid‐vapor phase equilibria measurements were made at 112.00 K on the binary systems nitrogen‐argon, nitrogen‐methane, and argon‐methane and the ternary system nitrogen‐argon‐methane. Values of gE, the excess Gibbs free energy, have been calculated from the experimental data for all the systems studied. The data and derived gE values for the binary systems were compared with the results of previous investigations with satisfactory agreement.
A generalized hard‐sphere augmented virial equation of state
Authors: Bienkowski Paul R. , Denenholz Howard S. , Chao Kwang‐Chu 
Published: June 2004

AbstractA generalized equation of state is developed by combinin a hard‐sphere equation with a truncated virial equation and generalizing the reduced hard‐sphere diameter as a function of reduced temperature and acentric factor. The new equation quantitatively agrees with Pitzer's table of compressibility factor over wide ranges of gas and vapor states and is always better than the truncated virial equation. Since the terms in the equation are physically meaningful it is capable of being improved systematically by including higher virial coefficients and by using hard‐core equations of state for nonspherical cores. The equation is extended to mixtures with well‐developed combination rules.
Holdup, flooding, and pressure drop in packed columns during countercurrent flow of mercury and water
Authors: Watson J. S. , McNeese L. E. 
Published: June 2004

AbstractThe hydrodynamics of countercurrent flow of liquids with a high density difference cannot be predicted reliably from correlations developed with data on fluids having low densities (usually water and organic solvents). Dispersed‐phase holdup, flooding rates, and pressure drop during countercurrent flow of mercury and water were studied with several packing materials. Results show that, for a given packing, flooding rates and holdup can be correlated in terms of a single parameter, the superficial slip velocity. For the mercury‐water system, this parameter is shown to be proportional to the packing diameter and packing void fraction for Raschig rings and solid cylindrical packing.
Stability of laminar pipe flows of drag reducing polymer solutions in the presence of high‐phase‐velocity disturbances
Authors: Hansen R. J. 
Published: June 2004

AbstractA theoretical study of high‐phase‐velocity disturbances in the laminar pipe flow of drag‐reducing polymer solutions is reported. These disturbances are found to be more stable in a polymer solution with a sufficiently small relaxation time than in a Newtonian fluid. The opposite effect is predicted when the relaxation time exceeds a critical value, however. These results are shown to be consistent with a hydrodynamic instability explanation of the early turbulence phenomenon.
Permeation of gases in polystyrene molded at elevated pressures
Authors: Dale W. C. , Rogers C. E. 
Published: June 2004

AbstractAtactic polystyrene was molded at pressures up to 3000 atmospheres, and the effects of this pressure history were studied by permeability measurements using helium, neon, and argon as probe molecules. The permeabilities were significantly reduced by molding at higher pressures. The diffusion coefficients decreased monotonically with molding pressure, reflecting more extensive interchain cohesion. In contrast, the solubility coefficients showed a broad minimum around a molding pressure of 1000 atm, indicating that changes in local order were induced by higher pressures. These changes were shown to affect permeation, mechanical characteristics, and other properties. An optimum molding pressure somewhat below 1000 atm is indicated for polystyrene.
Effect of specific gravity differences on nonideal mixing of continuous flow systems
Authors: Pelletier Martin P. , Cloutier Leonce 
Published: June 2004

AbstractThe effect of specific gravity differences as a primary factor of nonideal mixing was investigated and demonstrated by means of a combined M‐T (mixed‐tubular) reactor in a simple cylindrical flow tank. Specific gravity differences were provided by a temperature gradient created by a strongly exothermic, second‐order adiabatic chemical reaction. The results also allow investigation of the effects of the inlet feed rate, agitator diameter, and speed on the agitator fraction of the combined reactor.
Dynamic response of some ion‐selective electrodes
Authors: Markovic Patrick L. , Osburn James O. 
Published: June 2004

AbstractThe dynamic responses of five electrodes were measured by pulse testing. The electrodes were three pH electrodes a calcium‐ion electrode, and a chloride‐ion electrode. Measurements were made at temperatures from 1° to 50°C. The responses of their electrodes were analyzed to give the transfer function containing first‐ and second‐order time constants and a dead time.
Calculation of temperature distribution in the human body
Authors: Huckaba Charles E. , Hansen Lynn W. , Downey John A. , Darling Robert C. 
Published: June 2004

AbstractAn improved procedure is presented for the calculation of detailed steady‐state temperature distributions throughout the human body. The efficacy of the proposed computation procedure is demonstrated by comparison of calculated and experimental results for seven studies conducted on four subjects. Core temperatures were predicted within ±0.2°C and deviations for individual skin temperatures generally were within ±0.5°C.
Photopolymerization of acrylamide in an annular flow reactor
Authors: Sandru Dan , Smith J. M. 
Published: June 2004

AbstractRates of homogeneous polymerization of aqueous solutions of acrylamide were measured in an annular flow reactor at 35°C. By independent determinations of the quantum yield for the initiation step and the light intensity, it was possible to identify reaction orders and to calculate ratios of rate constants for the polymerization process.An empirical kinetics model, based upon producing activated molecules solely from initiator (K2S2O8), best fit the data. According to this model the rate is 3/2 order in monomer concentration, 1/2 order in initiator, and proportional to the 1/2 power of the intensity of absorbed radiation. The effect of monomer concentration on the induction period and tlie 3/2 order with respect to monomer indicate a complex initiation process.
Particle size analysis and structure of chromium hydrous oxide sols in the size range of less than 0.5 μm
Authors: Larson R. I. , Fullam E. F. , Lindsay A. D. , Matijevic E. 
Published: June 2004

AbstractParticle size measurements of chromium hydrous oxide sols using electron microscopy and light scattering techniques were in excellent agreement. Comparison was based on the most probable diameter and width of the distribution. The normal, lognormal, and zero‐order logarithmic density functions provided good first‐order approximations to the particle size measurements. The chromium hydrous sols were less than 0.5 μm in size.A closed wet cell specimen holder in an electron microscope was developed to observe, in situ, the chromium hydrous oxide sols. The colloidal particles had a uniform spherical shape with a narrow size distribution. Observation of the particle formation process in the closed wet cell qualitatively supports the mechanism that basic polymeric sulfates act as embryos in the formation of these particles.
Liquid ion‐exchange membranes
Authors: Moore J. H. , Schechter R. S. 
Published: June 2004

AbstractA liquid membrane consisting of an oil layer contained between two aqueous phases was found to leak when used to transport ions selectively from one adjacent phase to another. The source of the difficulty was found to be the formation of a separate aqueous phase within the oil layer. This phase could be eliminated by increasing the pressure within the oil layer.The pressure stabilized membrane was then tested and the observed rates of mass and electrical transport compared with values computed using a mathematical model. The comparisons were satisfactory considering the fact that no adjustable parameters were used to fit the data.
Thermodynamic properties of supercritical fluids and their mixtures at very high pressures
Authors: Breedveld Gerrit J. F. , Prausnitz John M. 
Published: June 2004

AbstractExperimental and estimated PVT data for simple fluids at very high pressures have been correlated with corresponding states theory. Generalized tables and charts are given for density, enthalpy, fugacity, and internal energy for the reduced temperature range 1 to 50 and for reduced pressures to 2000. Consideration is given to possible solidification at very high pressures and to applicability of the reduced charts to quantum fluids, water and ammonia, through temperature‐dependent effective critical constants. The van der Waals two‐fluid model of binary mixtures is used to calculated properties of mixtures including the composition of coexisting phases. The correlations presented here are useful for estimating thermodynamic properties at very high pressures.
Theoretical interpretation of gas oil selectivity data on X‐sieve catalyst
Authors: Pachovsky Roman A. , John Thomas M. , Wojciechowski Bohdan W. 
Published: June 2004

AbstractA six‐parameter multiresponse model based on the catalyst aging theory of Wojciechowski (1968) is applied to experimental selectivity data in gas oil cracking. Within the range of conditions studied, the model gave an adequate fit to the data. It was found that the selectivity curves at various cat/oil ratios were contained within optimum and minimum performance envelopes but that the relationships between these envelopes and the selectivity curves were not quite as simple as had previously been reported for a theoretical example (Campbell and Wojciechowski, 1969). The optimum time‐on‐stream for each of the cat/oil ratios was about one minute. Maximum gasoline production was 59 weight % at 81 weight % total cumulative conversion, resulting in a gasoline efficiency of 72.8%.
Simulataneous heat and mass transfer with and without reactant exhaustion in catalyst particles for reaction with volume change
Authors: Lih Marshall M. , Lin Kan 
Published: June 2004

AbstractAsymptotic analytic expressions for the concentration and temperature profiles as well as effectiveness factor inside porous, thin‐disk shaped catalyst particles have been developed for zeroth‐order exothermic reaction with reactant‐to‐product volume change. The individual and combinative effects of volume‐change, Thiele and thermal Thiele moduli, and of the dimensionless activation energy are discussed. As expected, the expressions revert to those for the corresponding isothermal and constant‐volume cases. Errors arising from the approximation were calculated and found to be quite acceptable.
Liquid diffusion of nonelectrolytes: Part I
Authors: Ghai R. K. , Ertl H. , Dullien F. A. L. 
Published: June 2004

AbstractThis review covers the field of liquid diffusion form the time of the publication of the review article by Johnson and Babb in 1957. In Part I a concise introduction is given to the phenomenological description of the diffusion process, followed by a review of the various theories of and model approaches to diffusion in binary mixtures. These are treated in the following categories: hydrodynamic theories, Eyring's theory and the friction coefficient theories. The predictions are compared with the experimental results throughout the review. Part I will be followed by Part II in November reviewing self‐diffusion, empirical predictive equations, and experimental techniques. A supplement of critical tabulations of all experimental diffusion data since 1956 has been prepared.
Absorption in packed towers with concurrent downward high‐velocity flows—II: Mass transfer
Authors: Gianetto A. , Specchia V. , Baldi G. 
Published: June 2004

AbstractMeasurements were made of mass transfer coefficients with gas and liquid phase controlling resistance using a concurrent flow packed column with a wide range of operating conditions and four types of packing.Mass transfer coefficients were much larger than those obtainable in countercurrent towers.The results were correlated with dissipated energy values. The correlations obtained can be used to determine absorption efficiency. Experimental results show that the use of a high velocity concurrent flow column is particularly suitable when mass transfer is controlled by the liquid phase resistance with chemical reaction in the liquid.
Mass transfer to a plane below a rotating disk at high Schmidt numbers
Authors: Homsy Robert V. , Newman John 
Published: June 2004

AbstractThe Lighthill transformation is used to determine the rate of mass transfer at high Schmidt numbers to a disk imbedded in a stationary plane below a rotating disk. This diffusion‐layer solution breaks down near the center and leading edge of the mass‐transfer disk. Solutions in these regions are reported, and a uniformly valid composite solution for the local Nusselt number is determined along with an expression for the average mass‐transfer rate to the disk.
A new technique for precedence‐ordering chemical process equation sets
Authors: Soylemez Sezer , Seider Warren D. 
Published: June 2004

AbstractAn algorithm that combines structural equation analysis with algebraic rearrangement and substitution has been developed to precedence‐order algebraic chemical process equations. The SWS (Structural Analysis with Substitutions) algorithm selects an output variable for each equation, rearranges the equation to solve for that variable, and reduces the number of equations by substitution. The algorithm has been used for computer generation of Fortran programs to perform meterial and energy balances in the design of chemical processes.
Computational models for cylindrical catalyst particles
Authors: Sorensen Jan P. , Guertin Earl W. , Stewart Warren E. 
Published: June 2004

AbstractA study is made of computational methods for predicting the performance of cylindrical catalyst particles in reactions with nonlinear kinetics. Accurate two‐dimensional collocation solutions are obtained and used to test simplified solution methods. A novel parametric integration method is used to traverse the region of multiple solutions. The local stability of several states is determined.
Motion of particles entrained in a plasma jet
Authors: Lewis J. A. , Gauvin W. H. 
Published: June 2004

AbstractThe motion of small particles (glass microspheres, 30 to 140 microns in diameter) entrained in a free argon plasma jet was studied by means of high‐speed cine streak photography. Radial temperature and velocity profiles as well as axial profiles of temperature, velocity, and argon concentration in the jet were experimentally determined by means of a plasma calorimetric probe. The system was found to be characterized by low relative Reynolds numbers (0.2 to 20) and extremely high deceleration rates (about –2,000 g). Under these conditions, an increase of drag coefficient over that predicted by the standard curve was experimentally observed. This increase was attributed to the nonsteady flow field around the particle (the so‐called “history term” in the equation of motion). A general computer program has been proposed which predicts the particle velocity, acceleration and temperature along its trajectory.
Kinetics of liquid phase xylene isomerization over H‐mordenite
Authors: Hopper J. R. , Shigemura Dennis S. 
Published: June 2004

AbstractA study of the kinetics for the liquid phase isomerization of ortho‐xylene over H‐mordenite has been made at 505°K, 2.76 × 105 N/m2, and 23 mole % toluene diluent. This is the first known study reporting kinetic data for the liquid phase isomerization of xylene over a zeolite catalyst. High activity is indicated by the 80% achievement of para‐xylene equilibrium at 505°K, 2.76 × 105 N/m2, and 0.767 × 10−3 kg/s/kg. Although high selectivity has previously been reported for a specifically prepared zeolite catalyst, the 99+% selectivity of the isomerization reaction with H‐mordenite as indicated by no C9+ aromatics and less than 0.5 mole % benzene in the product is most significant. Catalyst deactivation was also significant. Reaction rate constants are reported for a first‐order reversible triangular model among the xylene isomers with catalyst deactivation incorporated into the model.
Crystal‐size distribution and its interaction with crystallizer design
Authors: Moyers Charles G. , Randolph Alan D. 
Published: June 2004

AbstractRecent progress in understanding crystallization processes is reviewed, especially with regard to the problem of crystal‐size distribution (CSD) and its many interactions with the design, analysis, and operation of crystalizers. This subject is considered from both the researcher's and practitioner's points of view, and special attention is given to the impact of recent theories on crystallizer design and operation.A generalized theory for the analysis and prediction of CSD, based on population balance mechanics, has been developed and tested over the past decade. Predictive design of CSD is now a possibility with the design techniques presented here and using suitable bench‐scale data. Published evaluations of the reliability of design methods utilized in commercial practice would be a valuable asset to the science of crystallization.
A liquid thermistor
Authors: Cussler E. L. 
Published: June 2004

AbstractA liquid thermistor consisting of a salt‐triethylamine‐water solution shows a resistance increase of 100% per degree centigrade over a range of 8°C. Outside this specific temperature range, the resistance changes slowly. The altered resistance results from the phase change at the critical solution temperature. While devices of this type can show major hysteresis and are restricted to specific temperatures, their response is faster than a millisecond.
Effects of diffusion resistance on gasoline selectivity in catalytic cracking
Authors: Pachovsky Roman A. , Wojciechowski Bohdan W. 
Published: June 2004

AbstractThe time on stream theory of catalyst decay is applied to gas oil cracking selectivity data from a static bed reactor operating with a diffusion limited catalyst. It is found that intraparticle diffusion affects the reactions leading to the disappearance of gas oil to a much greater extent than the reaction leading to the recracking of gasoline and catalyst poisoning. Reasons for this behavior are postulated. It is also found that the overall kinetic order for the rate of disappearance of gas oil is decreased with the result that maximum selectivity occurs at a higher conversion value than for a corresponding diffusion‐free catalyst. It is concluded that probably diffusion limitation is not a serious problem with respect to gasoline selectivity in commercial reactors.
Stability of the class II classified product crystallizer with fines removal
Authors: Randolph Alan D. , Beer Gary L. , Keener James P. 
Published: June 2004

AbstractThe stability of crystal‐size distribution (CSD) in the classified product crystallizer with fines removal was investigated using spectral techniques to determine stable solutions of the linearized population balance. The model used to describe the crystallizer assumed rapid growth kinetics (high yield), magma‐dependent secondary nucleation, and recycle of dissolved fines. Fines removal and classified product removal were characterized in the model by piece‐wise constant removal rates (R – 1) and z times the MSMPR removal rate, respectively.Stability regions were presented as critical values of the kinetic nucleation/growth rate exponent i = d(log B°)/d(log G) versus dimensionless parameters of the system. The parameters which influence CSD stability were maximum fines size and removal rate, product classification size and removal rate, and the magama‐characterizing exponent in the nucleation expression. Whether or not dissolved fines are recycled directly back to the crystal magma also influences stability.
Water jet atomization of molten steel
Authors: Grandzol Richard J. , Tallmadge John A. 
Published: June 2004

AbstractData are obtained and a model derived for describing particle size distribution for molten metals atomized by two water jets. The influences of water jet parameters on size distribution and median size are reported and discussed in terms of fundamental quantities and model predictions. The data, which were obtained using fan‐spray jets impinging at an apex angle of 60° to atomize Type 4620 steel, indicated that median size was primarly a function of water jet velocity.