摘要:

AbstractA network model has been developed to simulate the flow of emulsions and solid particles through porous media. Particle deposition due to direct interception, as well pore plugging by straining are accounted for in the model. The effects of two important factors—the ratio of particle size to pore size, and the fluid velocity—on particle deposition are also investigated. The strength of the model lies in its ability to predict accurately effluent concentration profiles, permeability changes occurring during deep bed filtration, and the evolution of the filter coefficient with time. Model predictions for different particle and pore size distributions of both solid and emulsion particles are in agreement with experimental d

ISSN:0001-1541    

DOI:10.1002/aic.690341102

出版商:American Institute of Chemical Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractThe augmented BACK equation of state for polar fluids is extended to mixtures by introducing mixing rules separately for the nonpolar and polar interactions. Fluid phase equilibria are calculated for polar + nonpolar, and polar + polar mixtures including mixtures of hydrogen‐bonding substances. Enthalpy calculations are illustrated with enthalpy of H2S + N2and heats of mixing of steam mixtures, and carbon dioxide mixtures.Cross interaction coefficients are adjusted for the correlation of data on binary mixtures. Both phase equilibrium and enthalpy data are correlated at the same time with two such coefficients for each binary. The cross interaction coefficients are constants, invariant with temperature, density, or phase stat

ISSN:0001-1541    

DOI:10.1002/aic.690341103

出版商:American Institute of Chemical Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractElectrolyzing sparingly soluble gases as they are absorbed from bubbles can be significantly facilitated by addition of a soluble redox couple which serves to increase both mass and charge transfer rates. A diffusion layer model is used to calculate reaction‐catalyzed mass transfer rates in regions of boundary layer penetration by reactive bubbles for the case of (m,n)‐order irreversible homogeneous reaction. The dissolved redox catalyst is continuously regenerated at the solid electrode surface. Approximate solutions, which relate surface flux to concentration driving force, are in excellent agreement with the numerical solutions under conditions of fast homogeneous reaction and concentrated catalyst (modified Damköhler number and dimensionless catalyst concentration greater than 3). Diffusion layer thickness is calculated from the mass transfer coefficientkpin penetrated regions. A model based on spherical penetrating bubbles is used to determinekpand specific surface areaapof penetrated regions fromkpapvalues that have been measured in gas‐liquid flow through a packed bed. The mass transfer behavior provides useful insight into why the penetration process is so effective in increasing overall reaction

ISSN:0001-1541    

DOI:10.1002/aic.690341104

出版商:American Institute of Chemical Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractMass transfer in sheared, concurrent gas‐liquid flows is investigated theoretically using solutions to the unaveraged advection‐diffusion equation. For sufficiently thick films, the resistance to mass transfer is shown to be confined completely within a thin region in the liquid near the interface and mass transfer coefficients are accurately predicted by an improved numerical technique that uses a velocity field derived from an Orr‐Sommerfeld equation with the time‐varying velocity computed directly from measurements of interfacial waves. The mass transfer coefficients are shown to depend on the magnitude and frequency content of the velocity fluctuations normal to the interface. As the film thickness decreases, transfer resistance extends throughout the film and turbulent mixing in the middle of the film controls the transfer rates. For this region, limiting values of transfer coefficients are predicted well by analytical solutions to the advection‐diffusion equation, which assume a lam

ISSN:0001-1541    

DOI:10.1002/aic.690341105

出版商:American Institute of Chemical Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractThis paper deals with SISO nonlinear processes and their control with state feedback. The Byrnes‐Isidori concept of non‐linear zeros is first reviewed and illustrated with two chemical engineering exemples. This concept is then used to interpret input/output linearizing state feedback as a nonlinear analog of placing poles at the process zeros. This interpretation leads to closed‐loop internal stability conditions for nonlinear processes under input/output linearizing state fee

ISSN:0001-1541    

DOI:10.1002/aic.690341106

出版商:American Institute of Chemical Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractA numerical model has been developed to predict the formation of carbon black particles by benzene pyrolysis. The approach, patterned after the work of Jensen, assumes that particle formation is controlled by four steps: gas phase reactions producing radical species, nucleation, growth and coagulation, and oxidation. In the present model, 15 reactions based on the work of Fujii and Asaba are used to describe the gas phase kinetics in which the phenyl radical is treated as the important intermediate in the formation of carbon black. A discrete distribution of 10 particle radii is also used to approximate the simultaneous growth and coagulation of spherical carbon particles. The results of the model show that a self‐preserving log normal distribution of carbon particles develops after an initial nucleation and growth period. The model results also compare favorably with reactor data. In particular, the numerical model predicts a mass median carbon particle diameter to within 10% of measured value

ISSN:0001-1541    

DOI:10.1002/aic.690341107

出版商:American Institute of Chemical Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractThe population balance for batch aggregation of particulate suspensions is recast in a form that may be solved simply and accurately. The transformed equation is deduced with the introduction of only one additional parameter, which is found to be a constant for all cases. The transformed equation is tested by comparison with some analytical solutions with which it is found to be in excellent agreement. In particular, the equation is shown to predict correctly the rate of change of total particle number and volume. Compatible descriptions of linear growth and nucleation are developed with similar success.The method is then applied to modeling thein vitrogrowth and aggregation of kidney stones (calcium oxalate monohydrate crystals). It is found that these phenomena are well described by McCabe's ΔLlaw, a size‐independent coalescence kernel, and first‐order kinetics. Simulated particle size distributions and their moments are in excellent agreement with the experimental res

ISSN:0001-1541    

DOI:10.1002/aic.690341108

出版商:American Institute of Chemical Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractA new approach is presented to overcome load disturbance problems. Based on the parallel cascade control structure, the primary controller is designed for the servo response, and the secondary controller is designed for the disturbance‐rejection purpose. A perfect disturbance‐rejection controller is derived for the secondary loop. Simulation studies show that improvement in load responses can be achieved for some cases. However, for some other cases, parallel cascade control simply worsens the load responses as a result of interaction between primary and secondary loops. A new interaction measure for load disturbance (γ) is proposed to determine whether improved load responses is achievable using cascade control structure. More importantly, the interaction measure also quantifies the margin of improvement that can be achieved over conventional single‐loop control. A design procedure for improved load responses was proposed. The simulation results show that the new approach offers a simple and effective alternative for disturbance‐r

ISSN:0001-1541    

DOI:10.1002/aic.690341109

出版商:American Institute of Chemical Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractThe effect of viscoelasticity on the kinetics of the shear‐induced flocculation of colloids has been investigated theoretically and experimentally. A numerical technique for such three‐dimensional problems called global residual minimization (GRM) has been developed as an alternative to finite element and finite difference methods. In the GRM method, minimization of the residual of the momentum balance is used as the selection criterion for the velocity‐field solution. Trajectory simulations were carried out for spheres in a corotational Jeffreys fluid at a variety of Weissenberg numbers,We. ForWe≤ 0.01, the effect of viscoelasticity is found to be negligible. ForWe= 1.0, flocculation rates are enhanced. ForWe= 10.0, a possibly large reduction in flocculation rate is indicated.Experiments were conducted using 600 nm radius polystyrene spheres in hydroxyethyl cellulose solutions. At shear rates corresponding roughly toWe= 10.5 and 15.3, the flocculation rates were found to be at least an order of magnitude less than the rate expected in a Newtonian fluid. It is postulated that this reduction in flocculation rate is caused by the viscoelasticity of the suspendin

ISSN:0001-1541    

DOI:10.1002/aic.690341110

出版商:American Institute of Chemical Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractIn cocurrent downflow of a gas and a liquid through a packed column, a transition from trickling flow to pulsing flow is observed as one increases the flow rates. A simple macroscopic model for the two‐phase flow is analyzed to examine whether this regime transition should be viewed as the loss of stability of a steady state or the loss of existence of any solution for the steady‐state equations of motion. The former appears to be a more reasonable interpretation and an explicit algebraic criterion for the onset of pulsing is presen

ISSN:0001-1541    

DOI:10.1002/aic.690341111

出版商:American Institute of Chemical Engineers    

年代:1988

数据来源: WILEY