ISSN:0001-1541    

DOI:10.1002/aic.690180203

出版商:American Institute of Chemical Engineers    

年代:1972

数据来源: WILEY

摘要:

AbstractA mathematical model of the centrifugal molecular still has been derived based on a fully developed profile, but negligible normal and tangential velocity components. Thermal gradients, film thicknesses, and evaporation rates calculated from this mathematical expression correlate well with reported literative values as well as with the present data.Mean distillation rates were measured for five pure liquids on a centrifugal still with an effective evaporating surface area of 100 sq. cm. These experimentally obtained rates for liquids exhibiting ideal behavior agreed quite well with theoretical values predicted on the basis of simple kinetic theory. In the case of an associated liquid, however, rate measurements were found to be only 53 to 90% of the theoretical value. Although these low values tend to support the concept of an evaporation coefficient as a true molecular property, there wasevidence that surface irregularities could have accounted for all or at least part of the discrepancy noted.

ISSN:0001-1541    

DOI:10.1002/aic.690180204

出版商:American Institute of Chemical Engineers    

年代:1972

数据来源: WILEY

摘要:

AbstractThe effect of temperature on the reaction rate of grouped species which are consumed by parallel nth order irreversible reactions is investigated. It is shown that when the activation energies of the individual reacting species is aboput equal the temperature effect can be described by an Arrhenius expression. However, when the activation energies of the various reactions are widely spread the Arrhenius dependence may not be adequate unless one assumes that the activation energy of the lump may be temperature and conversion dependent. Unter these conditions the Arrhenius temperature dependence is at best a rough approximation and it is very important to define exactly the experimental method of determining the activation energy. Widely different activation energies for the pseudocomponent may be obtained from different experimental techniques which yield the same value for a single reactant.

ISSN:0001-1541    

DOI:10.1002/aic.690180205

出版商:American Institute of Chemical Engineers    

年代:1972

数据来源: WILEY

摘要:

AbstractOptimal output feedback control low requiring measurment of the output only has been considered for a class of tubular processes. The advantage of this formulation, which requires a single measurement of the output only, over a previous result which requires an infinite number of measurements, has been demonstrated through a heat exchanger example. However, when the terminal time is grater than the residence time of fluid, a time‐delay element is neede

ISSN:0001-1541    

DOI:10.1002/aic.690180206

出版商:American Institute of Chemical Engineers    

年代:1972

数据来源: WILEY

摘要:

AbstractThe local and macroscopic thermal transport from a calorimeter‐instrumented sphere 1.5 in. in diameter located in an air steram ws measured experimentally in the subcritical flow regime. The Reynolds number was varied between 5,200 and 70,200 with artificially induced turbulence level varying from 0.013 to 0.256. Higher turbulence increased thermal transport through the laminar bundary layer prevailing in the forward hemisphere, and significantly retarded the point of separation from about 87° to 106° as measured from stagnation. An increase in the Reynolds number shifted the point of separation forward and altered the behavior in the wake. In the separated wake region, the experimental evidence indicated that the vortex reattached to the rear surface and formed a new boundary layer that resulted in a decrease in the local thermal trans

ISSN:0001-1541    

DOI:10.1002/aic.690180207

出版商:American Institute of Chemical Engineers    

年代:1972

数据来源: WILEY

摘要:

AbstractThe quantity T12 here called the reduced activity coefficient is related to Γ12the mean activity coefficient of a strong electrolyte 12 as follows:\documentclass{article}\pagestyle{empty}\begin{document}$$\Gamma _{12} = \gamma 12^{{1 \mathord{\left/ {\vphantom {1 {z_1 z_2 }}} \right. \kern-\nulldelimiterspace} {z_1 z_2 }}}$$\end{document}where z1and z2are the charge number on the ions. The value of Γ12for electrolyte 12 in an aqueous solution containing the three ions 1, 2, and 3, such as Na+Cl−and Ba++, is to be calculated as follows:\documentclass{article}\pagestyle{empty}\begin{document}$${\rm log}\Gamma _{12} = {\rm log}\Gamma ^ \circ _{12} + {\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$2$}}\left({{\rm X}_{\rm 3} } \right){\rm log}\left({{{\Gamma ^ \circ _{32} } \mathord{\left/ {\vphantom {{\Gamma ^ \circ _{32} } {\Gamma ^ \circ _{12} }}} \right. \kern-\nulldelimiterspace} {\Gamma ^ \circ _{12} }}} \right)$$\end{document}Here Γ°32and Γ°12are for the indicated electrolytes, namely NaCl and BaCl2in this example, at the total ionic strength of the mixture. The term X3represents the fraction m3z32/(m1z12+ m3z32) in whichmrepresents the molality of the indicated ion. Fair success is usually attained with this equation in predicting γ, even at high electrolyte concentrations.Similar equations are proposed for aqueous solutions containing four or m

ISSN:0001-1541    

DOI:10.1002/aic.690180208

出版商:American Institute of Chemical Engineers    

年代:1972

数据来源: WILEY

摘要:

AbstractA method is described for solving the problem: given fixed pressure, temperature, the amounts of the chemical elements, and the chemical potentials of possible chemical species at the pressure and temperature specified, determine the equilibrium composition. The method requires a minimum of judgment on the part of the user.A modification of Naphtali's method for direct minimization of Gibbs' function provides an estimate of the composition of sufficient accuracy to insure convergence of solution, by the Newton‐Raphson method, of the nonlinear equations describing the equilibrium.Problems in treating multiple phaes of unknown stability and chemical species present in small amouts are handled by ignoring unstable phases and small quantitites in the direct minimization until the amounts of the major consitituents have been at least approximately determined. To accomplish this, species temporarily ignored are assigned a ficitious mol fraction so that their re‐entry into the calculation can be established. Truncation errors in the direct minimziation can be tolerated because of the two‐step method.Examples of some of the problems solved are

ISSN:0001-1541    

DOI:10.1002/aic.690180209

出版商:American Institute of Chemical Engineers    

年代:1972

数据来源: WILEY

摘要:

AbstractThe effect of the addition of an inert liquid into a gas‐phase reaction occurring on a solid catalyst was studied using the isomerization of cyclopropane to propylene on a sukuca‐alumina catalyst as the model reaction and one of three hydrocarbon solvents as the liquid. With a nonadsording liquid the intrinsic reaction rate constant is the same in both the gas and the gas‐liquid systems but adsorption of impurities from the liquid or adsorption of the liquid itself can have an enormous retarding effect on the reaction rate. Even i the absece of these effects the addition of a liquid phase decreases the percet conversion and increses the likelihood of occurrence of mass transfer limita

ISSN:0001-1541    

DOI:10.1002/aic.690180210

出版商:American Institute of Chemical Engineers    

年代:1972

数据来源: WILEY

摘要:

AbstractThe response of water and 20 ppm. solutions of Separan AP‐30 and Polyox WSR 301 to the periodic motion of a thin sleeve was measured using a laser Doppler velocimeter. The sleeeve was moved in an axial direction by an external coupling at frequencies from 1/4 to 1.O Hz and at amplitudes of 1/2 to 2 in. The flow filed downstream of the distrbance was found to consist of three regions: 1. a near field with a separation wake from the sleeve moving toward the piep centerline; 2. an intermediate field in which alternate laminar and turbulent slugs passed a point; and 3. a far field with decaying turbulent lfow. Defferences in the behavior of water flows and polymer flows appeared in each region. In the near field, wakes spread faster in water flows. In the intermediate field, the laminar slugs disappeared into turbulence more rapidly in water flows. And in the far field, the turbulence was not as developed in the polymer flows.Detailed statistical evaluations were made on the signals in each region for a Reynolds number of 2000. The response of the dilte polymer polymer solutions appeared to be governed by the initial interaction with the sleeve. Fewer high frequencies were generated than in the pure solvent so the periodic disturbance persisted downstream. In pure water the eddies from the separation wake interacted strongly with the periodic distrurbance leading to rapid decay of the periodic portion. Shear rates were not high enough to attribute the dilute polymer differences to viscoelastic effect

ISSN:0001-1541    

DOI:10.1002/aic.690180211

出版商:American Institute of Chemical Engineers    

年代:1972

数据来源: WILEY

摘要:

AbstractKinetics of the dehydration oft‐butyl alcohol to isobutylene were measured with a semibatch reactor containing liquid reactant and suspended particles of cation exchange resin catalyst [sulfonated copolymer of styrene and divinylbenzene (DVB)]. Effects on rate were determined for variations in temperature (58 to 76°C.), reactant water mole fraction (0.0005 to 0.10), and catalyst pacticle diameter (77 to 620 μ) and crosslinking (2 to 12% DVB).Nearly anhydroust‐butyl alcohol failed to penetrate the shrunken network of the polymer. Reaction ebgan only on particle peripheries, and product water penetrated the gel network and s welled it to allow penetration of the alcohol. Rate consequently increased to a maximum (about 0.5 moles/min. equivalent of catalyst SO3H groups at 76°C.) and then decreased as water competed with reactant fro catalytic sites. A spherical catalyst particle is modeled as a shrinking cetrol core, free of reactant and water, and a swollen shell in which concent rations are independent of position and time. The model fits reaction rate and separate particle swelling data for 80 μ particles of catalyst containing 12% DVB, but it is increasingly inadequate for larger particles and catalysts of lower DVB

ISSN:0001-1541    

DOI:10.1002/aic.690180212

出版商:American Institute of Chemical Engineers    

年代:1972

数据来源: WILEY