摘要:

AbstractCarrier‐mediated transport in membranes as a globally nonreactive process is distinguished from film theory with chemical reaction and other facilitated diffusion phenomena. With the concept of stoichiometric and system invariants, an approach is developed for the analysis of carriersediated transport with multiple permeants involving multiple reactions in the membrane. Approximate solutions of the requisite differential equations according to the relative importance of diffusion and reaction rates are reviewed, as well as typical experimental studies. Criteria for evaluating whether a membrane is in the diffusion or equilibrium regime are given, and, in the latter case, the effects of some system parameters are given, for example, binding constants, competitive permeant

ISSN:0001-1541    

DOI:10.1002/aic.690200302

出版商:American Institute of Chemical Engineers    

年代:1974

数据来源: WILEY

摘要:

AbstractProcedures are developed for predicting liquid film controlled mass transfer in gas sparged contactors with and without mechanical agitation. Mass transfer is shown to depend on mean bubble size. Bubble shape, motion, and interface fluctuations are all properties that are associated with bubble size, which, in turn, can be determined from the physical characteristics of the contacting system.Experimental measurements were made on CO2stripping from aqueous solution with air in 0.00252, 0.0252, and 0.252 m3tanks. The vessels were geometrically similar, fully baffled, and equipped with four flat‐blade impellers and spargers. These measurements are used to evaluate earlier correlations and to develop improved scale‐up procedu

ISSN:0001-1541    

DOI:10.1002/aic.690200303

出版商:American Institute of Chemical Engineers    

年代:1974

数据来源: WILEY

摘要:

AbstractTurbulent pipe flow was examined by measuring the radial dispersion of dyed fluid introduced at an axial point source within the flow. From the classical theoretical results of G. I. Taylor it was possible thereby to calculate various parameters that characterize the structure of the turbulent flow field. A comparison was made between water, and aqueous solutions of polyethylene oxide (Polyox) at concentrations up to 50 ppm (by weight). Results indicate that Polyox affects the turbulence in the following ways: (1) intensity is reduced, (2) the energy spectrum is shifted toward low frequency, (3) dispersion occurs largely through large scale motion, and intermittency is increased. Indication is also seen that a simple exponential form for the Lagrangian correlation coefficient is superior to other often recommended models.

ISSN:0001-1541    

DOI:10.1002/aic.690200304

出版商:American Institute of Chemical Engineers    

年代:1974

数据来源: WILEY

摘要:

AbstractA solution is given for unsteady state concentration profiles in an infinitely long composite cylinder resulting from a step‐change in concentration in a large reservoir surrounding the cylinder. The composite cylinder consists of an inner cylinder with diffusivity D1surrounded by a permeable tube with diffusivity D2and has interfacial mass transfer resistances at the cylinder‐tube and tube‐reservoir interfaces. Numerical values are given for the first eight roots and various coefficients of the solution for physical properties typical of tubular (hollow fiber) membranes. These results can be used in the analysis of data from unsteady state mass transfer experiments to determine the permeability of homogeneous tubular membranes. A simple, approximate method for data analysis is suggested for the rapid estimation of the permeability of both homogeneous and asymmetric (skinned) tubular memb

ISSN:0001-1541    

DOI:10.1002/aic.690200305

出版商:American Institute of Chemical Engineers    

年代:1974

数据来源: WILEY

摘要:

AbstractNucleation and crystal growth processes involved in the batch precipitation of photographic emulsions by the addition of silver nitrate to an aqueous solution of bromide and gelatin have been reasonably successfully modeled. Simulation predicts the known increase in average crystal size with increased addition time, with increased temperature, and with increased halide levels. Solubility is related to crystal size by the Gibbs‐Thomson equation. The predicted decrease in the number of crystals during the course of precipitation is similar to published data, but there are quantitative differences. The model is very sensitive to variations in the constant in the growth equation, but not to variations in the constants in the nucleation equatio

ISSN:0001-1541    

DOI:10.1002/aic.690200306

出版商:American Institute of Chemical Engineers    

年代:1974

数据来源: WILEY

摘要:

AbstractTheoretical investigations of viscous heating in the flow of fluids with an exponential dependence of viscosity on temperature have shown that, for a given shear stress, two shear rates are possible. Above a critical value, the stress decreases as the shear rate increases.The present work is an experimental study of this phenomenon in plane and circular Couette flows and in cylindrical Poiseuille flow. ArochlorR1260, a high viscosity Newtonian fluid with an extremely sensitive viscosity‐temperature dependence is used as the test fluid. The results clearly show that two shear rates for Couette flow exist for one measured wall shear stress. Because of the viscosity‐pressure dependence of the fluid, the Poiseuille flow results are inconclus

ISSN:0001-1541    

DOI:10.1002/aic.690200307

出版商:American Institute of Chemical Engineers    

年代:1974

数据来源: WILEY

摘要:

AbstractWhen ultrasound is applied to a liquid reacting system, the reaction rates are often increased. The application of ultrasonics, therefore, provides additional modes of accelerating the reaction rates which are usually not considered by conventional mechanisms. In an attempt to study the effect of ultrasonics on chemical reactions, experimental work was undertaken in which the reaction rates of the hydrolysis of methyl acetate were measured under the presence of ultrasound. The temperature, the vapor pressure with in the cavitating bubbles, the resonance characteristics, the volume of the reacting system, and the intensity and frequency of the ultrasound are all influencing parameters on the reaction rates.

ISSN:0001-1541    

DOI:10.1002/aic.690200308

出版商:American Institute of Chemical Engineers    

年代:1974

数据来源: WILEY

摘要:

AbstractThe problem of synthesizing an optimal multicomponent separation system which is energy integrated is solved by a combined decomposition and dynamic programming technique.Dynamic programming is an optimization technique which allows the solution by decomposition of a multistage or serial optimization problem. Whenever the special serial structure is absent, again decomposition can be tried, but in this case it is by no means obvious how to decompose effectively the given problem into subproblems. In this paper the nonserial problem of synthesizing an energy integrated separation system is solved by decomposing the original problem so that a serial structure results.

ISSN:0001-1541    

DOI:10.1002/aic.690200309

出版商:American Institute of Chemical Engineers    

年代:1974

数据来源: WILEY

摘要:

AbstractLineweaver‐Burk plots of reaction rate data obtained with immobilized enzymes need not be linear even when intrinsic enzyme kinetics follow the simple Michaelis‐Menten rate expression. Theoretical calculations show that mass transfer effects may cause curvature which is concave or convex to the abscissa, depending upon experimental conditions. Consequently, graphical procedures commonly employed for analysis of soluble enzyme kinetics may yield misleading results when applied to immobilized enzymes. Three approaches which follow from the behavior of numerical and asymptotic solutions to the problem are proposed for extraction of intrinsic kinetic informat

ISSN:0001-1541    

DOI:10.1002/aic.690200310

出版商:American Institute of Chemical Engineers    

年代:1974

数据来源: WILEY

摘要:

AbstractMicroemulsions, which are optically transparent oil‐water dispersions, were spontaneously produced upon mixing hexadecane, hexanol, potassium oleate, and water in specific proportions. The viscosity of the microemulsions was measured for several water/oil ratios including the phase‐inversion region. The striking optical and viscosity changes observed at specific water/oil ratios were in agreement with the proposed mechanism of phase‐inversion, namely, water spheres → water cylinders → water lammellae → continuous water phase, for this system. In the phase‐inversion region, the dispersion exhibited birefringence and rheopectic properties. An extremely high viscosity (>100,000 cps) exhibited by the dispersions between water/oil ratios of 2.0 and 3.5 were explained in terms of ion‐dipole association between oleate and hexanol molecules on ad

ISSN:0001-1541    

DOI:10.1002/aic.690200311

出版商:American Institute of Chemical Engineers    

年代:1974

数据来源: WILEY