Showing papers in "Aiche Journal in 1976"
TL;DR: In this article, a generalized flow regime map based on this theory is presented, which is used for determining flow regime transitions in two-phase gas-liquid flow, and the mechanisms for transition are based on physical concepts and are fully predictive.
Abstract: Models are presented for determining flow regime transitions in two-phase gas-liquid flow. The mechanisms for transition are based on physical concepts and are fully predictive in that no flow regime transitions are used in their development. A generalized flow regime map based on this theory is presented.
2,420 citations
TL;DR: In this paper, a model for the initial particle deposition in a deepbed filter with a sphere-in-cell porous media model was presented, and the results indicated that deposition occurs under favorable surface interactions.
Abstract: This paper presents a model for the initial particle deposition in a deepbed filter with a sphere-in-cell porous media model used. The analysis includes all the relevant mechanisms, and the results indicate that deposition occurs under favorable surface interactions. A semiempirical expression relating collection efficiency and operating parameters is presented.
745 citations
TL;DR: A review of available fundamental information focuses on thermal decomposition of coal in inert gas and in hydrogen, with emphasis on the effects on yield of products exerted by time, temperature, heating rate, pressure, hydrogen partial pressure, and particle size, and on the development of chemical and transport models of engineering importance as discussed by the authors.
Abstract: The fundamental understanding of coal and its behavior under gasification conditions is far from complete, but significant insights into the complex chemical and physical phenomena have been achieved. This review of available fundamental information focuses on thermal decomposition of coal in inert gas and in hydrogen, with emphasis on the effects on yield of products exerted by time, temperature, heating rate, pressure, hydrogen partial pressure, and particle size, and on the development of chemical and transport models of engineering importance.
636 citations
TL;DR: Experimental and theoretical work on the rheological properties of suspensions is reviewed in this paper, with particular emphasis placed on the nature of the approximations made, so that purely empirical formulas can be clearly separated from those having a theoretical basis.
Abstract: Experimental and theoretical work on the rheological properties of suspensions are reviewed. Attention is focused on systems consisting of rigid, neutrally buoyant particles suspended in Newtonian fluids; no restrictions, however, are placed on the concentration of the particles or on the forces acting in the suspension. The assumption that an effective viscosity depending solely on the volume fraction of the particles suffices to describe the rheology of suspensions is examined and shown to be inadequate. Indeed, the experimental evidence strongly supports the view that suspensions behave macroscopically as non-Newtonian fluids whose rheological properties are influenced by a large number of factors; these factors are listed. The various theories that have been put forward to explain the flow of suspensions are discussed, with particular emphasis placed on the nature of the approximations made, so that purely empirical formulas can be clearly separated from those having a theoretical basis. Suggestions for future work, both theoretical and experimental, are provided.
466 citations
TL;DR: The experimental observations and the extent of theoretical understanding of the instabilities in shear and extensional flows in polymeric liquids are discussed in this paper, where the experimental observations are compared with theoretical understanding.
Abstract: Instabilities which arise in shear and extensional flows in the processing of polymeric liquids are reviewed. The experimental observations and the extent of theoretical understanding of the instabilities are discussed.
406 citations
TL;DR: In this article, a predictive kinetic model for fluid catalytic cracking (FCC) was developed, which involves lumped species consisting of paraffins, naphthenes, aromatic rings, and aromatic substituent groups in light and heavy fuel oil fractions.
Abstract: A predictive kinetic model has been developed for fluid catalytic cracking (FCC). The kinetic scheme involves lumped species consisting of paraffins, naphthenes, aromatic rings, and aromatic substituent groups in light and heavy fuel oil fractions. The kinetic model also incorporates the effect of nitrogen poisoning, aromatic ring adsorption, and time dependent catalyst decay. The rate constants for these lumped species are invariant with respect to charge stock composition. The predictive capabilities of the model have been verified for wide ranges of charge stocks and process conditions.
371 citations
294 citations
TL;DR: In this paper, a method to predict the height of the wall layer and the interfacial drag in annular flow under conditions that the flow rate of the entrained liquid is known is developed from measurements on air-water flow in circular tubes.
Abstract: A method to predict the height of the wall layer and the interfacial drag in annular flow under conditions that the flow rate of the entrained liquid is known is developed from measurements on air-water flow in circular tubes. Flow conditions are found to be characterized by a generalized Martinelli flow parameter.
254 citations
TL;DR: In this article, a flash photomicrographic method and modified dye-light transmittance technique are employed to measure size distributions and mixing frequencies in a turbulently agitated flow vessel.
Abstract: A flash photomicrographic method and modified dye-light transmittance technique are employed to measure size distributions and mixing frequencies in a turbulently agitated flow vessel. This liquid-liquid dispersion is nearly spatially homogenous. Mixing frequencies are strongly dependent on impeller speed and moderately dependent on holdup fraction.
232 citations
TL;DR: In this paper, a mathematical model including intraparticle transport and chemical reaction within the particles (grain theory) has been developed to simulate this sulfur dioxide sorption reaction, and the model has been applied to simulate the reaction of sulfur dioxide and oxygen with limestones.
Abstract: Experimental measurements of the reaction of sulfur dioxide and oxygen with limestones have demonstrated substantial influence of the geologic origin of the stone, its porosity and particle size, gaseous concentration of sulfur dioxide, and temperature on the course of reaction and the conversion (that is, the degree of utilization of the limestone content of the particles as a sorbent for sulfur dioxide). A mathematical model including intraparticle transport and chemical reaction within the particles (grain theory) has been developed to simulate this sulfur dioxide sorption reaction.
207 citations
TL;DR: In this paper, an exact matrix method of solution to the Maxwell-Stefan equations is used for calculating multicomponent gas phase mass transfer coefficients and transfer rates. But the results are seen to be exact matrix analogues of classical binary relations and may also be applied as an approximation to describe liquid phase transport.
Abstract: Convenient expressions for calculating multicomponent gas phase mass transfer coefficients and transfer rates are obtained by use of an exact matrix method of solution to the Maxwell-Stefan equations. The results are seen to be exact matrix analogues of classical binary relations and may also be applied as an approximation to describe liquid phase transport.
TL;DR: In this article, the mechanics of isothermal melt spinning are studied for a viscoelastic liquid with a power law viscosity and a constant shear modulus, and the onset of the draw resonance instability, the magnitude of diameter fluctuations in the unstable region, and a second stable region at high draw ratio are predicted accurately.
Abstract: The mechanics of isothermal melt spinning are studied for a viscoelastic liquid with a power law viscosity and a constant shear modulus. Steady state velocities and stresses are in agreement with experiment. The onset of the draw resonance instability, the magnitude of diameter fluctuations in the unstable region, and a second stable region at high draw ratio are predicted accurately.
TL;DR: In this article, a model for simultaneous heat transfer, mass transfer, and chemical reaction in the oxidation of carbon monoxide over platinum containing monoliths is presented. But the model is not suitable for predicting the behavior of the Nusselt number.
Abstract: Mathematical models are developed which account for simultaneous heat transfer, mass transfer, and chemical reaction in the oxidation of carbon monoxide over platinum containing monoliths. A two-dimensional model is shown to predict unusual behavior of the Nusselt number in the presence of rapid reaction. However, a simpler one-dimensional model is adequate for predicting monolith behavior.
TL;DR: The stability of a thermally stratified, saturated porous media through which mass is being ejected is considered theoretically in this paper, where the stability parameter is a flow modified D'Arcy-Rayleigh number and is a function of a single scalar variable.
Abstract: The stability of a thermally stratified, saturated porous media through which mass is being ejected is considered theoretically. The stability parameter is a flow modified D'Arcy-Rayleigh number and is a function of a single scalar variable, the dimensionless through-flow strength. Results of both linear and energy theory are given, and it is seen that the fluid can lose stability by either a buoyantly driven mode or by a continuous analogue of the Saffman-Taylor mode. (auth)
TL;DR: In this paper, the orthogonal collocation method is applied to solve the mathematical model of a monolith catalytic converter, in which the reaction takes place in a porous catalytic layer deposited on the wall of a tube.
Abstract: The orthogonal collocation method is applied to solve the mathematical model of a monolith catalytic converter, in which the reaction takes place in a porous catalytic layer deposited on the wall of a tube. A sequence of models is developed, with the most complicated one involving transient heat and mass transfer in three dimensions.
TL;DR: In this article, the effects of gas velocity and particle diameter on the electrification of a metal pipe were examined both theoretically and experimentally with particular attention to the collision between particles and pipe wall.
Abstract: Electrostatic characteristics in gas-solids flow in a metal pipe are studied both theoretically and experimentally with particular attention to the collision between particles and pipe wall. Effects of gas velocity and particle diameter on the electrification are also examined.
TL;DR: In this article, a series of mathematical models for a monolith catalytic converter to oxidize carbon monoxide in automobile exhaust are presented, including axial conduction in the wall, diffusion and conduction of the gas in a transverse direction perpendicular to the flow direction, multiple steady states, and transients giving wall temperatures exceeding the adiabatic temperature.
Abstract: Calculations are done for a series of mathematical models for a monolith catalytic converter to oxidize carbon monoxide in automobile exhaust. Phenomena studied include axial conduction in the wall, diffusion and conduction in the gas in a transverse direction perpendicular to the flow direction, multiple steady states, and transients giving wall temperatures exceeding the adiabatic temperature.
TL;DR: In this article, a spherical droplet in creeping flow with an arbitary surface tension gradient at its interface is dervied to show theoretically that the terminal velocity is reduced and that interfacial velocity is retarded, especially near the rear of the droplet, when a trace of surfactant is present in the exterior phase and when surface aging is controlled by diffusion.
Abstract: Stream functions are dervied for a spherical droplet in creeping flow with an arbitary surface tension gradient at its interface. The stream functions are used to show theoretically that the terminal velocity is reduced and that the interfacial velocity is retarded, especially near the rear of the droplet, when a trace of surfactant is present in the exterior phase and when surface aging is controlled by diffusion.
TL;DR: The countercurrent backmixing model of a fluidized bed reactor predicts axial concentration profiles quite different from those suggested by simple two-phase models as discussed by the authors, which can also be distinguished in terms of the dependence of conversion on operating variables.
Abstract: The countercurrent backmixing model of a fluidized bed reactor predicts axial concentration profiles quite different from those suggested by simple two-phase models. The models can also be distinguished in terms of the dependence of conversion on operating variables.
An experimental study of ozone decomposition in a reactor of 22.9 cm diameter has provided extensive data for comparison with backmixing and two-phase models which incorporate bubble size variation. The measured profiles show a minimum concentration within the bed at gas velocities above a critical value, as predicted only by the backmixing model. The effect of operating variables on the shape of the profiles is also well accounted for by this model. The backmixing model is further supported by good agreement between predicted and measured reactant conversion. In particular, the variation of conversion with rate constant and gas velocity is fitted more accurately by the backmixing model than by two-phase models.
TL;DR: In this paper, the authors present a commentary on the status of application of modern control theories to industrial chemical processes, and the difficulties encountered in the implementation of advanced control to chemical reactors are critically examined in order to determine the reasons for its limited success.
Abstract: This paper presents a commentary on the status of application of modern control theories to industrial chemical processes. The difficulties encountered in the implementation of advanced control to chemical reactors are critically examined in order to determine the reasons for its limited success to date. Chemical processes, very often poorly understood because of the physicochemical complexities, are nonlinear, highly interacting, spacially dependent, and continuously disturbed by many uncharacterized noises. It is time-consuming and expensive to develop advanced control methods for these systems because few of the available theories can be applied directly. Thus, we often find it difficult to economically justify advanced control projects.
TL;DR: In this paper, a mathematical model was developed for representing the reduction of hematite disks with a mixture of hydrogen and carbon monoxide, and experimentally measured values were used for the porosity and the effective pore diffusivities were calculated from pseudo binary formulas.
Abstract: On the assumption of shrinking core behavior, a mathematical model was developed for representing the reduction of hematite disks with a mixture of hydrogen and carbon monoxide. In the model, experimentally measured values were used for the porosity, and the effective pore diffusivities were calculated from pseudo binary formulas. Literature data were used for the activation energies of the reactions, while the preexponential factors were obtained by data fitting. The model was found to provide a good means for representing experimental measurements of Szekely and El-Tawil (1976), both with regards to the effect of temperature and gas composition.
TL;DR: In this paper, a free-radical polymerization with kinetic equations taking into account monomer, polymer, and solvent transfer and initiation, termination, propagation, and inhibition reactions was studied both experimentally and by simulation to determine the performance of various Kalman filters, with feasible measurements used.
Abstract: A free-radical polymerization with kinetic equations taking into account monomer, polymer, and solvent transfer and initiation, termination, propagation, and inhibition reactions was studied both experimentally and by simulation to determine the performance of various Kalman filters, with feasible measurements used.
TL;DR: In this paper, the surface integration growth kinetics of potash alum crystals were evaluated in terms of the step model of crystal growth and the results emphasize the importance of independently measuring growth kinetic before secondary nucleation kinetics can be calculated from MSMPR experiments.
Abstract: Overall growth and dissolution rates of potash alum crystals have been measured over the size range 3 to 70 μm. The derived surface integration growth kinetics, which are found to be linear with respect to supersaturation and strongly size dependent, are evaluated in terms of the step model of crystal growth. The results emphasize the importance of independently measuring growth kinetics before secondary nucleation kinetics can be calculated from MSMPR experiments.
TL;DR: In this article, the authors analyzed the equilibrium data for the sorption of oxygen, nitrogen, carbon monoxide, and methane in 5A molecular sieve in terms of a simple theoretical model isotherm.
Abstract: Equilibrium data for the sorption of oxygen, nitrogen, carbon monoxide, and methane in 5A molecular sieve are analyzed in terms of a simple theoretical model isotherm. The model provides an excellent correlation of the single-component isotherms over the entire concentration range, and it is shown that equilibrium data for sorption of binary mixtures of these gases are correctly predicted by the model using the parameters (Henry constants and molecular volumes) derived from analysis of the single-component isotherms. The model predicts that mixtures of two sorbates with equal molecular volumes should show approximately ideal solution behavior in the adsorbed phase. The experimental data of Lederman for the sorption of nitrogen-methane mixtures show the expected behavior over a wide range of pressures.
TL;DR: Experimental residence time distribution functions for the liquid and solids conveying processes by a screw conveyer and for the polymer in a plasticating extruder were obtained by using a radioactive tracer technique as discussed by the authors.
Abstract: Experimental residence time distribution functions for the liquid and solids conveying processes by a screw conveyer and for the polymer in a plasticating extruder were obtained by using a radioactive tracer technique. A comparison was made between the experimental results and several theoretical models available for melt extrusion and mixing processes.
TL;DR: Transient diffusion of n-butane, isobutane and 1-butene in synthetic CaX(Na) spherical pellets was studied in a constant volume, well-stirred system as mentioned in this paper.
Abstract: Transient diffusion of n-butane, iso-butane, and 1-butene in synthetic CaX(Na) spherical pellets is studied in a constant volume, well-stirred system. The intracrystalline diffusion coefficients are in the order of 10−14 cm2/s, and the activation energy is about 7.0 Kcal/g-mole. Experimental data agree well with a mathematical model developed to describe transient diffusion.