摘要:

AbstractPart II of the review paper covers the self‐diffusion theories and their comparison with experimental results. This is followed by a review of empirical and semi‐empirical predictive equations of mutual and self‐diffusion coefficients. Recent developments in experimental techniques for measuring liquid diffusivities are discussed in the last section. A supplement of experimental diffusion data since 1956 is avai

ISSN:0001-1541    

DOI:10.1002/aic.690200102

出版商:American Institute of Chemical Engineers    

年代:1974

数据来源: WILEY

摘要:

AbstractVarious techniques of molecular thermodynamics and solution theory have been applied, through the transition state theory, to problems in chemical kinetics. These include experimental techniques for ascertaining the structure and properties of the transition states for various classes of reactions, plus analytical methods for using this information to predict the effect of solvents or reactant structure on chemical reaction rates. Such methods provide the chemical engineer with an additional parameter to use in the optimal design of reaction systems–that is, the chemistry of the reaction itsel

ISSN:0001-1541    

DOI:10.1002/aic.690200103

出版商:American Institute of Chemical Engineers    

年代:1974

数据来源: WILEY

摘要:

AbstractFormulas relating the rate of filtrate flow in a sectioned disk filter to the process variables are derived. It is demonstrated that an optimum inner radius which yields a maximum flow of filtrate can be chosen. Flow rates for drum and disk filters operating under similar conditions are compared.

ISSN:0001-1541    

DOI:10.1002/aic.690200104

出版商:American Institute of Chemical Engineers    

年代:1974

数据来源: WILEY

摘要:

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.

ISSN:0001-1541    

DOI:10.1002/aic.690200105

出版商:American Institute of Chemical Engineers    

年代:1974

数据来源: WILEY

摘要:

AbstractThe behavior of an immobilized enzyme reactor utilizing asymmetric hollow fibers is simulated using a theoretical model. In this reactor, an enzyme solution contained within the annular open‐cell porous support structure of the fiber is separated from a substrate flowing through the fiber lumen by an ultrathin dense membrane impermeable to enzyme but permeable to substrate and product. The coupled set of model equations describing the behavior of this reactor represents an extended Graetz problem in the fiber lumen, with diffusion through the ultrathin fiber skin and reaction in the microporous sponge region. Exact analytic expressions for substrate concentration profiles throughout an idealized fiber which incorporate the membrane and hydrodynamic mass transfer resistances are obtained for a first‐order enzyme reaction, and numerical techniques for their evaluation are given. This analysis is extended to yield a numerical finite difference solution for nonlinear Michaelis‐Menten reaction kinetics, which is shown to agree with the analytic solution, asKm/C0, the ratio of the Michaelis constant to the initial substrate concentration, becomes large (

ISSN:0001-1541    

DOI:10.1002/aic.690200106

出版商:American Institute of Chemical Engineers    

年代:1974

数据来源: WILEY

摘要:

AbstractThe objective of this work was to study the undesirable oscillating behavior which can develop on distillation trays. This takes the form of violent lateral movements of the gas/liquid mixture, causing premature flooding and reduced efficiency. It has been demonstrated that entrainment is significantly increased by the presence of oscillations. A simple predictive method by which a designer may evaluate the likelihood of oscillations occurring is proposed. It is concluded that columns of greater than about 1.0 m diam. operating at atmospheric pressure or above are unlikely to oscillate. However, reduced pressure columns of greater diameter may oscillate. A very simple mesh baffle system which completely prevents oscillations developing is described.

ISSN:0001-1541    

DOI:10.1002/aic.690200107

出版商:American Institute of Chemical Engineers    

年代:1974

数据来源: WILEY

摘要:

AbstractA theoretical and experimental investigation of the pumping characteristics of the normal stress extruder was made. The theoretical model requires only material property data and extruder dimensions and rotation speed to evaluate the main velocity field, flow rate, and pressure. The flow from the extruder was measured for two viscoelastic polymer solutions and a polymer melt as a function of gap setting and angular velocity. These measurements were in reasonable agreement with the proposed model.

ISSN:0001-1541    

DOI:10.1002/aic.690200108

出版商:American Institute of Chemical Engineers    

年代:1974

数据来源: WILEY

摘要:

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 r

ISSN:0001-1541    

DOI:10.1002/aic.690200109

出版商:American Institute of Chemical Engineers    

年代:1974

数据来源: WILEY

摘要:

AbstractThe kinetic mechanisms of fuel nitrogen conversion to NO and N2in a diffusion flame were investigated. A simple model of a diffusion flame in which the reaction zone has a finite thickness was developed. The purpose of this model was to allow the testing of complex kinetic mechanisms of pollutant formation under conditions where the fuel and oxidant feed rates are controlled by diffusion. A simple kinetic mechanism in which fuel nitrogen was simulated by nitrogen atoms showed the correct functional dependence of nitric oxide emissions on fuel nitrogen content. The model also predicts a significant effect of combustion intensity and temperature on fuel nitrogen conversion. For the hydrogen air diffusion flame the Zeldovich reaction mechanism could account for the production of N2as well as NO.

ISSN:0001-1541    

DOI:10.1002/aic.690200110

出版商:American Institute of Chemical Engineers    

年代:1974

数据来源: WILEY

摘要:

AbstractRates were measured at 25°C for the adsorption of benzaldehyde from an aqueous solution into particles of Amberlite, or activated carbon, suspended in the solution. The data for monodisperse, Amberlite particles (mean pore radius = 50Å) showed significant intraparticle diffusion resistance over the entire particle size range 200 to 900 microns (diameter). Intraparticle diffusivities were larger (tortuosity factor ∼ 0.35) than expected from pore‐volume diffusion in the liquid‐filled pores.For the activated carbon particles (of the same size) which have a bidisperse pore‐volume distribution (pore diameter range 15 to 104Å), the effect of intraparticle diffusion was much less important and separation of the external diffusion resistance to obtain a precise value of the intraparticle diffusivity was not possible. However,Devalues are larger than for Amberlite and much greater than the molecular diffusivity of benzaldehyde in liquid‐filled pores. The unusually high intraparticle diffusivity seems most likely to be due to interpreting dynamic adsorption data for a bidisperse porous particle with a theory involving but one

ISSN:0001-1541    

DOI:10.1002/aic.690200111

出版商:American Institute of Chemical Engineers    

年代:1974

数据来源: WILEY