bluuebunny/crossref_metadata_2025_split huggingface dataset:
Liquid‐solid mass transfer in packed beds with downward concurrent gas‐liquid flow
Authors: Satterfield Charles N. , Van Eek Michael W. , Bliss Gary S. 
Published: June 2004

AbstractMass transfer coefficients were determined by measuring the rate of solution of cylindrical 3 or 6 mm benzoic acid tablets into water in the presence of flowing nitrogen, helium, or argon. Gas flow rates varied from 0 to 1.6 kg/(m2·s) and liquid flow rates from 0.5 to 25 kg/(m2·s), resulting in hydrodynamic flow patterns varying from trickle to turbulent pulse types of flow. In the pulse regime, the mass transfer coefficient was markedly affected by gas flow rate but did not depend on gas density explicitly if correlated in terms of an energy dissipation function.
Hydrodynamics of drop formation from a hydrocarbon film around a sphere placed in a moving aqueous phase
Authors: Calteau Jean P. , Aurelle Yves , Roques Henri L. 
Published: June 2004

AbstractThe study of the coalescence of secondary dispersions passing through a granular packing has led to the consideration of drop formation from a hydrocarbon film around a single sphere placed in the flux of an aqueous phase. An analogue mock‐up study led to a mathematical model for relating the diameter of the drop to various parameters participating in the phenomenon. A relationship enabling reasonably accurate calculation of the diameter of a drop formed by means of such a sphere placed in a stationary or mobile aqueous phase for a wide range of Reynolds numbers and Bond numbers is proposed.
A sparse computation system for process design and simulation: Part I. Data structures and processing techniques
Authors: Lin T. D. , Mah R. S. H. 
Published: June 2004

AbstractAs an alternative to tearing, symbolic permutation may be used to facilitate data processing rather than dimensional reduction in equation solving, permitting a reduction in computing effort without introducing any deleterious effects on the numerical convergence. Data structures and processing techniques suitable for this purpose have been successfully devised and tested. A program incorporating these techniques has been implemented on a CDC 6400 computer and used to solve irreducible systems of up to 551 linear and nonlinear equations.
Part II. A performance evaluation based on the simulation of a natural gas liquefaction process
Authors: Mah R. S. H. , Lin T. D. 
Published: June 2004

AbstractSPARSCODE was evaluated based on the simulation of natural gas liquefaction using multicomponent refrigerants. Results obtained on four cases containing 179 to 573 equations show a computing time reduction by a factor of 40 to 250 in equation solving and an overall reduction by a factor of 4 to 30 for the simulation.
A comprehensive experimental investigation of tubular entry flow of viscoelastic fluids. Part II. The velocity field in stable flow
Authors: Cable P. J. , Boger D. V. 
Published: June 2004

AbstractCenter‐line velocities and developing velocity profiles are presented for viscoelastic fluids flowing in a 2:1 and 4:1 abrupt entry contraction. Two flow regimes are clearly identified: a vortex growth regime and a divergent flow regime. Dramatic differences in the velocity field are observed and discussed for the two flow regimes. A kinematic model based on the velocity field data is proposed for vortex growth flow.
Optimum design of chemical plants with uncertain parameters
Authors: Grossmann I. E. , Sargent R. W. H. 
Published: June 2004

AbstractA new strategy is proposed for the optimum design of chemical plants whose uncertain parameters are expressed as bounded variables. The design is such that the plant specifications will be met for any feasible values of the parameters while optimizing a weighted cost function which reflects the costs over the expected range of operation. The strategy is formulated as a nonlinear programme, and an efficient method of solution is derived for constraints which are monotonic with the parameters, a case which arises frequently in practice. The designs of a pipeline with a pump, of a reactor‐separator system, and of a heat exchanger network, all with uncertain technical parameters, illustrate the effectiveness of the strategy for rational overdesign of a chemical plant.
Vapor‐liquid equilibrium: Part V. Data reduction by maximum likelihood
Authors: Van Ness H. C. , Pedersen Finn , Rasmussen Peter 
Published: June 2004

AbstractA systematic study is presented of the objective functions applicable to the reduction of vapor‐liquid equilibrium data by regression procedures based on the principle of maximum likelihood. Numerical results are based on a set of artificial x‐y‐P data constructed so as to conform to the assumptions that underlie proper application of this principle.
An experimental study of the rheological behavior of surface films
Authors: Addison J. V. , Schechter R. S. 
Published: June 2004

AbstractA constitutive equation has been developed to relate surface stresses to the deformational history of an interface. To verify the applicability of the equation to real surface films, experimental studies involving spread and adsorbed monolayers have been conducted using the deep‐channel surface rheometer operated both under the conditions of oscillatory and constant floor motion. The results reported here are the first obtained using an oscillatory system.Experimental results indicate that both spread and adsorbed monolayers can exhibit viscoelastic behavior which may be represented by the model. Furthermore, it has been found that for three long chain, fatty acid films, spread on a pH 6.1 aqueous substrate, surface shear viscosity and surface elasticity increase with film pressure and molecular weight. The observed rheological behavior was found to be strongly pH dependent.
Optimal design of multistage adsorption‐bed systems
Authors: Sung Edmond , Han Chang Dae , Rhee Hyun‐Ku 
Published: June 2004

AbstractThe operation of two arrangements of multistage adsorption beds, parallel and series, was analyzed, and the optimal design problem of minimizing the capital and operating costs of the multistage adsorption bed systems was formulated. Solution of the optimization problem was obtained by using the Fibonacci search scheme. For the purpose of the study, data on the adsorption of liquid on activated carbon were taken from the literature for both single solute and multisolute adsorption systems and was used to derive the expressions for adsorption rate and the equilibrium relationship. Details of the performance of the optimally designed multistage adsorption bed systems are presented in terms of the physical and design parameters.
An analytical study of ultrafiltration in a hollow fiber artificial kidney
Authors: Papenfuss Heinz D. , Gross Joseph F. , Thorson Steven T. 
Published: June 2004

AbstractA theoretical investigation of ultrafiltration through hollow fibers used in artificial kidney applications is presented. The hollow fibers are considered to be cylindrical tubes with ideally selective semipermeable walls which retain cellular particles (red and white cells, platelets) and plasma proteins in the blood perfusing the fibers. In contrast, water and species of low and medium molecular weight can freely permeate the membranes. The assumption is made that secondary flows avoid the formation of concentration boundary layers at the wall. Proper nondimensionalization of the equations for axial and radial transport results in the identification of parameters which are important in the characterization of the ultrafiltration through semipermeable tubes. Perturbation analyses for small values of these parameters lead to sets of differential equations which were solved analytically. These closed form solutions demonstrate the influence of hydraulic conductivity of the fiber walls, geometry, and axial and transmembrane pressure drop on the efficiency of hollow fiber artificial kidneys.
Solution of material balances for flow sheets modeled with elementary modules: The constrained case
Authors: Sood Mohinder K. , Reklaitis G. V. 
Published: June 2004

AbstractFlow sheet material balance calculations are greatly simplified if all process input streams, reaction stoichiometry, and conversions, as well as all stream and component split fractions, are specified. Yet in many applications, especially those arising in process design, the available material balance specifications can take on many alternate forms. Each of these additional specifications can readily be expressed as a linear or nonlinear constraint equation involving species or total flow rates.In this paper, an approach is developed for incorporating such specifications within the computational framework for solving unconstrained material balance problems. The linear as well as the nonlinear constraints are accommodated by generating a parametric solution to the underlying unconstrained problem. The parameters are determined by solving simultaneously first the linear and then the nonlinear constraint equations. Only as many equations are solved iteratively as there are nonlinear constraints.
Use of a finite‐stage transport concept for analyzing residence time distributions of continuous processes
Authors: Rogers Reed S. C. , Gardner Robin P. 
Published: June 2004

AbstractThis study is concerned with the derivation and application of the finite‐stage transport concept for modeling residence time distributions (RTD's) originally proposed by Adler and Hovorka (1961). This six‐parameter model is shown to be more versatile and accurate than the common two‐parameter tanks‐in‐series or axial dispersion models. Radioactive tracer results are given for a number of particulate unit processes with special emphasis on wet‐discharge ball mills.
Kinetics of step polymerization with unequal reactivities
Authors: Gandhi K. S. , Babu S. V. 
Published: June 2004

AbstractThe kinetics of step polymerization involving a monomer with unequal reactivities has been obtained. The polydisperity index (PDI) has also been calculated both as a function of conversion and the initial stoichiometric ratio. It has been shown that the usually assumed maximum value of 2 for PDI can lead to erroneous molecular weight.
The dynamic behavior of a CSTR: Some comparisons of theory and experiment
Authors: Schmitz R. A. , Bautz R. R. , Ray W. H. , Uppal A. 
Published: June 2004

AbstractMathematical methods employed recently in a theoretical study by Uppal et al. (1974) are applied to the second‐order homogeneous reaction between sodium thiosulfate and hydrogen peroxide and are combined with experimental investigations of that reaction using a nonadiabatic continuous stirred tank reactor (CSTR). A complete portrayal of the expected behavior of that reaction system is presented in parameter space. Some new experimental studies of reactor instabilities are presented and linked to that portrayal. Close agreement is shown between theoretical predictions and experimental data.
Rheological characteristics of solid‐liquid mixtures
Authors: Ackermann Norbert L. , Shen Hung Tao 
Published: June 2004

AbstractThe relationship between the shear stress and strain rate of a mixture consisting of solid particles suspended in a Newtonian fluid depends upon the physical properties of the mixture as well as kinematic features of the flow. Functional relationships for rheological properties of mixtures are derived and compared to measured results obtained by previous investigators.
Kinetics of fixed‐bed adsorption: A new solution
Authors: Liaw C. H. , Wang J. S. P. , Greenkorn R. A. , Chao K. C. 
Published: June 2004

AbstractA new solution is obtained to the kinetics of a fixed‐bed adsorber in response to a step change in feed concentration for a linear equilibrium system with consideration for the resistance to mass transfer in both the mobile and stationary phases. The differential equations of continuity and mass transfer are integrated upon simulating the intraparticle concentrations with a parabola. The results agree with Rosen's rigorous but complex solution in the range of conditions of practical interest. The present solution is more convenient for computer application for the calculation of breakthrough curves.
A gas convection model of heat transfer in large particle fluidized beds
Authors: Adams Ronald L. , Welty James R. 
Published: June 2004

AbstractA steady gas convection model of heat transfer to a horizontal cylinder immersed in a large particle gas fluidized bed has been developed. The model is based upon the hypothesis that the large particles will be isothermal and includes the effect of radiation as well as interstitial turbulence.Results of calculations based on the model, for a two‐dimensional bubbling bed, indicate that a single bubble, having a diameter equal to the cylinder diameter, has a relatively small influence on the total heat transfer.
Simulation models for intraparticle deactivation: Scope and reliability
Authors: Downing D. M. , Lee J. W. , Butt J. B. 
Published: June 2004

AbstractAn experimental and modeling study of the dynamic behavior of an individual catalyst pellet as influenced by deactivation and dilution has been made. The reaction system employed was benzene hydrogenation over nickel/kieselguhr catalyst pellets diluted with 10% graphite, 10% silica, or undiluted; thiophene was employed as the catalyst poison.A one‐dimensional effective transport model was developed, and the parameters for this model were determined principally from separate off line experiments or steady state experimental information. The adequacy of the model was determined from a direct comparison of the experimental and computed time‐temperature profiles.
Steady nonionic countergradient transport through membranes by coupled diffusion
Authors: Notter R. H. , Tam Y. M. , Min S. 
Published: June 2004

AbstractCoupled diffusion generated countergradient transport through membranes is analyzed by experimental and theoretical means. Membrane wedge interferometer experiments on an ethanolwater‐cellophane membrane system show that net countergradient mass transfer of the less permeable component ethanol may be generated over a wide concentration range. A theoretical analysis of an idealized membrane separating two binary bulk solutions is developed to display further the major features of diffusional coupling effects, and good agreement between observed and predicted countergradient transport characteristics is shown.
A kinetic study of ozone‐phenol reaction in aqueous solutions
Authors: Li K. Y. , Kuo C. H. , Weeks J. L. 
Published: June 2004

AbstractThe present research concerns mechanism and rate of reaction between dissolved ozone and phenol in homogeneous solutions. The stopped‐flow technique was employed to obtain absorbances during reactions; the kinetic experiments were conducted at temperatures varying from 5° to 35°C in aqueous solutions with pH values ranging from 1.5 to 5.2.The kinetic data indicated that the absorbance of a mixed solution increased rapidly in the very early portion of the reaction and then declined slowly in the remaining period. The rate of reaction in the early period was first order with respect to both phenol and ozone concentrations. The rate constant increased with pH value and temperature, and an activation energy of 5.74 K cal/mole was obtained. Further tests showed that the dissolved ozone was consumed completely in the first period and that in the second period the intermediate products were decomposed without depletion of ozone. Catechol, o‐quinone, hydroquinone, oxalic acid, humic acid, and a dimer were identified from mass spectra as products of the ozonization reaction.A free radical mechanism, with initiation of an electrophilic reaction for the formation of catechyl radical, has been proposed to explain the experimental data for phenol‐ozone reaction in aqueous solutions. According to the proposed mechanism, the reaction path through the attachment to ortho position is much more favorable compared with that through the paraposition because of geometric advantage, though quinones and hydroxyphenol can be formed through parallel paths. The products of reaction detected in this research, therefore, are accountable by this mechanism. A rate equation derived on the basis of this mechanism also agrees well with that observed from the kinetic experiments.
Periodic cycling of plate columns: Mass transfer with nonideal liquid draining
Authors: Furzer I. A. 
Published: June 2004

AbstractMathematical modeling of a periodically cycled plate column has been completed by using a liquid bypass model to describe nonideal liquid draining. A numerical solution over a wide range of parameters provides a closed envelope of feasible solutions. A region of this envelope encloses favorable operating values of the parameters, while the other region is unfavorable. Measurements of the parameters for nonideal liquid draining in a 600 mm diameter column fitted with sieve plates lead to predictions of only small improvements in separation performance. Modifications to the column intervals are required to move the parameters into a more favorable position in the solution envelope.
Maintaining sparsity in process design calculations
Authors: Stadtherr Mark A. 
Published: June 2004

AbstractSparse linear systems in bordered block‐triangular form can be efficiently solved by block‐triangular splitting, a new technique that provides a drastic reduction in the fill‐in (loss of sparsity) that occurs in the direct solution of such systems. This technique is applicable in the iterative solution of the large systems of nonlinear equations that arise in the equation oriented approach to process simulation and design calculations.
Flow through tubes with sinusoidal axial variations in diameter
Authors: Deiber J. A. , Schowalter W. R. 
Published: June 2004

AbstractAn iteration technique has been developed to solve the equations of motion for flow of an incompressible Newtonian fluid through a circular tube with a radius which varies sinusoidally in the axial direction. The iteration is essentially geometric; one proceeds from a solution for flow through a tube in which the wavelength of diameter change in the axial direction is arbitrarily large to a solution for the wavelength and amplitude of interest. Theoretical predictions of inception of secondary flow are in good agreement with experiments.
Power consumption and gas capacity of self‐inducting turbo aerators
Authors: Zundelevich Yury 
Published: June 2004

AbstractA theoretical and experimental analysis of self‐inducting turbo aerator performance was carried out based on the theory of water jet injector operation. It was shown that the aerator's injection coefficient is completely determined by only two dimensionless groups, CH and EuG, between which there is a single valued dependence on whose basis generalization of experimental data is possible. An analytical expression for the optimality criterion or aerator performance index, accounting for aerator gas capacity, power consumption, and submergence, has been obtained in terms of CH and EuG with only one adjustable parameter. From the above two dependencies, a methodology was developed for determining optimal operating conditions, by means of which all the data necessary for the optimal design can be obtained from the results of bench scale experiment.
On the kinetics of coal oxidation
Authors: Avison N. L. , Winters R. M. , Perlmutter D. D. 
Published: June 2004

AbstractA series of seven coals of different ranks and from various locations were heated in air under relatively mild conditions to measure the rates of oxidation and the production of carbonic gases in the effluent stream. The gas flow rate, coal particle size, and reactor temperature were changed as independent variables. Each sample was exposed for from 6 to 9 hr under atmospheric pressure at temperatures in the range of 200° to 250°C. The results show two kinds of rate behavior depending primarily on the relative porosity of the coal under study. The small pore coals followed the expectations of the earlier Kam‐Hixson‐Perlmutter (KHP) model, but the large pore coals gave rates sensitive to transport effects. Correlations were also obtained on the ratio of carbon dioxide and carbon monoxide produced and on the relationship between the carbon content of an exposed coal and its heating value.
Criteria for selective path promotion in electrochemical reaction sequences
Authors: Sakellaropoulos George P. 
Published: June 2004

AbstractAn analysis of consecutive electrochemical reactions is presented with some emphasis on organic electrocatalytic sequences. The effect of potential and electrode kinetic parameters on reaction selectivity and on current and rate distribution is examined in two model electrochemical reactors with channel flow or with complete mixing. Results and some examples demonstrate that the electrolyte potential is the most significant parameter for selectivity control of complex series reactions in electrochemical processing or energy generation. Criteria developed for selectivity and current or rate variation provide the basis for the design of electrochemical reactors and for optimal operation considerations with multiple electrode reactions. Such criteria and analyses apply to a number of working electrode configurations operating with ionic as well as molecular reactants.
Water limitation in the C‐H‐O system over iron
Authors: Sacco Albert , Reid R. C. 
Published: June 2004

AbstractCarbon dioxide and hydrogen will react over iron at 800° to 1 000°K and 1 bar pressure yielding water, carbon monoxide, methane, and carbon. In addition, iron oxides and carbides form during reaction. Phase diagrams are used to analyze this complex reaction system. Data are presented which suggest that the formation of magnetite (Fe3O4) or wustite (FexO) inhibits carbon formation. The water yield thus observed is limited by the time dependent iron‐iron oxide‐gas equilibrium. Preliminary data also suggest that the formation of carbides has little effect on water yield.
The growth of competing microbial populations in a CSTR with periodically varying inputs
Authors: Stephanopoulos Gregory , Frederickson A. G. , Aris Rutherford 
Published: June 2004

AbstractThe operation of a periodically forced chemostat (CSTR) in which two microbial populations compete for the same nutrient has been examined. Easily implemented criteria for the stability of the resulting cycles have been obtained, using the Floquet stability theory. After examining several possibilities it was found that stable periodic trajectories of coexistence can be achieved: (a) when the dilution rate of the chemostat is properly varied in a periodic manner between two values so chosen that the growth of one population is favored by the first and the growth of the other population is favored by the second, (b) when a certain percentage of biomass and growing medium is harvested periodically from the chemostat, and (c) when both the dilution rate and the concentration of the substrate in the feed are varied simultaneously and in a periodic manner.
An equation for predicting third virial coefficients of nonpolar gases
Authors: De Santis Roberto , Grande Biagio 
Published: June 2004

AbstractAn empirical correlation for calculating third virial coefficients of nonpolar gases is developed in agreement with the corresponding states theorem. This equation requires the use of a third parameter which can be estimated from molecular parameters. The method is reliable, even for systems where no experimental data are available. The extension to mixtures involves one interaction constant for all possible binary sets.