bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of suspension density on crystal size distribution
Authors: Larson M. A. , Timm D. C. , Wolff P. R. 
Published: June 2004

AbstractThe concept of a continuous mixed suspension–mixed product removal crystallizer was used both as an analysis and experimental tool to study the effects of suspension density on crystal size distribution. If the crystals present in suspension are not a source of nuclei, larger crystals will be obtained in the presence of higher suspension densities. If the rate of new particle formation is proportional to the amount of crystals present, the crystal size obtained will not be changed by the suspension density level. There was evidence of nucleation rate dependency on the quantity of suspended crystals in the two systems studied experimentally.
Effect of nucleation kinetics on the dynamic behavior of a continuous crystallizer
Authors: Timm Delmar C. , Larson Maurice A. 
Published: June 2004

AbstractThe nucleation kinetics of three materials were related to the growth kinetics using steady state data obtained at various degrees of supersaturation. The power models obtained from the three crystallizaitons exhibited widely different kinetic orders. These materials were then crystallized under unsteady state conditions in a mixed suspension–mixed product removal crystallizer and the transient size distributions were determined. The unsteady state model previously developed by Randolph and Larson was solved on a digital computer for the three systems. Good agreement was obtained. It was found that unsteady state experiments have some advantages over steady state experiments in determining the kinetic order of nucleation.
A generalized B‐W‐R equation of state
Authors: Edmister W. C. , Vairogs J. , Klekers A. J. 
Published: June 2004

AbstractThe Benedict‐Webb‐Rubin Equation of State has been generalized by expressing the eight constants as functions of critical pressure, critical temperature, and acentric factor. An evaluation of the resulting generalization against the observed P‐V‐T data of thirteen hydrocarbons and carbon dioxide shows 0.3 to 2.0% average deviations of the calculated pressures from the observed, as compared with 0.2 to 1.4% when using the individual (that is, nongeneralized constants for each component). Standard errors of estimate for 1,464 experimental data points were 0.0089 for the proposed generalization vs. 0.0084 for the original B‐W‐R Equation.
Small scale tests for attrition resistance of solids in slurry systems
Authors: Bjorklund I. S. , Dygert J. C. 
Published: June 2004

AbstractIn many present day solids‐liquid contacting processes and slurry transport systems, the attrition rate of the solid particles is of primary technical and economic concern. Particle size degradation in a transport pipeline may make the delivered solids entirely unsatisfactory for the intended use, or separation of fines from the liquid phase and makeup of attrited solids may be so costly that an otherwise attractive process becomes unacceptable.Pilot scale tests to measure attrition in a slurry system are often costly and very time consuming. For this reason small scale tests have been developed for screening candidate systems prior to pragmatic pipe‐loop or pilot‐plant tests. Two of these test methods, crushing tests on individual particles, and annulus flow in a rotating cup apparatus, appear to give useful data on the relative attrition resistance of various solids and to provide a basis for estimating the attrition rate to be expected in a flowing system.Results obtained by using these test methods with silica gel in hexane and with molecular sieve particles in kerosene yielded some information as to the predominant mechanisms of attrition for these two types of solids. The brittle, glasslike silica gel appears to fail through impact fracture of small to medium size chips from the large particles, while attrition of molecular sieves results from surface abrasion, probably due to failure of the binder material, and yields only extremely fine products of attrition.This paper, which is based on a rather limited amount of preliminary experimentation, has been prepared in the hope that it may stimulate additional work on the development of useful standardized procedures for evaluating attrition resistance of solids.
Role of concentration level of the nondiffusing species in turbulent gas phase mass transfer at ordinary mass transfer rates
Authors: Wasan Darshanlal T. , Wilke Charles R. 
Published: June 2004

AbstractNumerical solutions to the diffusion‐convection equations are obtained with a digital computer to establish the role of concentration level of the nondiffusing species in nonequivolume diffusion in fully developed turbulent flow of gases in pipes. Results indicate that under ordinary mass transfer rates for a system at constant Schmidt and Reynolds numbers product of the gas‐phase mass transfer coefficient and the log mean partial pressure of the nondiffusing gas is nearly constant both in the mass transfer entry region and in the fully developed region. These results are compared with the experimental data on vaporization and absorption processes.We show that the effect of the mass transfer section length on the rate of turbulent mass transfer is quite significant. Furthermore, the results of the diffusion—convection analysis are in better agreement with experimental data for sections of finite length than results calculated from the momentum‐mass transfer analogy. The two methods agree in the limit for tubes of infinite length.
A kinetic theory of catalysis and mass transfer in a cylinder
Authors: Shendalman L. H. 
Published: June 2004

AbstractThe diffusion and mass transfer of a trace component in a background gas in a cylinder, is treated according to a relaxation transport equation. The system is assumed isothermal and at rest. An expression for an effective axial diffusivity is found which goes to the appropriate high and low density limits. Numerically, this diffusivity is similar to one half of the harmonic mean of the high density diffusivities, which is often used as an empirical extrapolating formula.The radial mass transfer problem results in an integral equation which is solved numerically for all Knudsen numbers.The case of catalytic reaction on the walls is considered in detail. Rarefaction effects become important under conditions of fast reaction. The problem of sublimation or evaporation from a cylinder wall can be treated by the same equations.
Stability of adiabatic packed bed reactors. Effect of flow variations and coupling between the particles
Authors: Vanderveen John W. , Luss Dan , Amundson Neal R. 
Published: June 2004

AbstractA simple cell model is used for the determination of necessary and sufficient conditions for the stability of an adiabatic fixed bed reactor. These conditions are stronger than those obtained by considering only a perturbation of a single particle. Because of the nonuniqueness of the steady state profiles certain pathological effects can occur when the flow rate of the reactant is changed. Geometric coupling between the particles and heat transfer by radiation give rise to further complexities. Examples are given in which the trends predicted by the models have been observed experimentally by Wicke and Frank‐Kamenetskii.
On the theoretical calculation of friction factors for laminar, transitional, and turbulent flow of newtonian fluids in pipes and between parallel plane walls
Authors: Hanks Richard W. 
Published: June 2004

AbstractVarious modifications of the Prandtl mixing‐length model for turbulent momentum transport in pipes and between parallel plane walls are discussed. The most complete modification, due to Gill and Scher, is improved by replacing one of their two empirical constants by a theoretically calculable parameter. The new theory is compared with experimental data from the literature and found to reproduce frictional resistance data accurately for all values of the Reynolds number. It is somewhat in error for velocity profiles at high Reynolds numbers, but accurately reproduces velocity profile data in the transition region. The new theory represents the first accurate semi‐theoretical calculation of frictional resistance coefficients for all regimes of flow (laminar, transitional, and turbulent) for both pipes and parallel plane ducts, and of velocity profiles in the transitional flow regime in either geometry.
Coupled energy and multicomponent mass transfer in dispersions and suspensions with residence time and size distributions
Authors: Gal‐or Benjamin , Padmanabhan Lakshminarasimha 
Published: June 2004

AbstractAn analytical solution for the transport equation is presented for the case of coupled energy and multicomponent mass transfer in an ensemble of spherical drops, bubbles or solid particles. The solution is used to evaluate the total interfacial transfer rates in a population with particle size and residence time distributions. Using matrix notation and appropriate transformations, the partial differential equations are solved for each phase by using an integral operator whose kernel is the residence time distribution for the flow system. The method of attack is illustrated by solving the transport equations for fine dispersions or suspensions with high hold‐up values and presence of adventitious surface active agents.
A comparison of theoretical and experimental results for the internal dissolution of soluble cylinders by water in Laminar flow
Authors: Straight Frank , Baasel W. D. 
Published: June 2004

AbstractA boundary layer solution applicable to a certain general type of mass transfer operations was developed by Baasel and Smith (1). When the solution was adapted to the systems of condensation of a vapor from noncondensing gases and absorption of a gas into a wetted wall column, the temperature and interfacial area could not be completely controlled. To overcome these difficulties, the rate of internal dissolution of a hollow cylinder of benzoic acid was experimentally measured and compared to the theoretically predicted values.The ratios of the predicted rates to the observed rates fell, with the exception of two runs out of twenty nine, between 0.622 and 1.303. It was therefore concluded that the finite difference techniques used to obtain a mathematical solution were valid. However, it was observed that the assumption of unidirectional diffusion was possibly not valid. It was concluded that for systems in which the ratio of the total molar density of the fluid to the saturation concentration of the material being transferred was large, in the approximate range of 700 to 2,700, the boundary layer approach corresponded to the Leveque approximation of the classical Graetz solution for heat transfer for fluids with a parabolic velocity distribution.
Nonuniform initiation of photoreactions. III. Reactant diffusion in single‐step reactions
Authors: Hill F. B. , Reiss N. , Shendalman L. H. 
Published: June 2004

AbstractThe influence of nonuniform initiation on conversion in single‐step photoreactions is examined theoretically. Reaction types studied include reaction following absorption by reactant and photosensitized reaction. The batch slab reactor and the laminar flow tubular reactor with outside radiation are considered. In the case of reaction following absorption by reactant in the batch slab reactor, nonuniform initiation is found to have no influence on conversion, whereas for the other combinations of reaction and reactor its presence requires the specification of diffusion as well as kinetic parameters in order to characterize the conversion history unequivocally. The characteristics of conversion histories in the presence of nonuniform initiation are determined, and the influence of nonuniform initiation on chemical measurements of radiation and on tubular reactor performance in the neighborhood of laminar‐turbulent flow transitions is discussed.
Hydroisomerization of normal pentane over a zeolite catalyst
Authors: Voorhies Alexis , Bryant Philip A. 
Published: June 2004

AbstractThe most active zeolite hydroisomerization catalyst found during the course of a series of screening experiments was palladium impregnated hydrogen mordenite. The high activity of hydrogen mordenite catalyst was also reported by research workers of the Shell Oil Company. (11) Typical conditions used in this study were 550°F., 450 lb./sq.in. gauge, 8 g. of n‐pentane fed /h./g. of catalyst, and a hydrogen/pentane molar ratio of 3.4.Process variable studies have shown that neither gas toparticle mass transfer, intraparticle (macro‐pore) diffusion, nor the chemical reactions at the palladium sites are rate limiting. The data can be correlated by a mathematical model based on the assumptions that a first‐order, reversible isomerization reaction on the mordenite acidic sites is rate‐controlling, and the apparent rate constant is an Arrhenius function of thetemperature of the system.The pressure dependency of the reaction rate constant is consistent with a dual‐site mechanism and Langmuir adsorption isotherms.
The nonsteady flow of fluids through expansible tubes
Authors: Sheppard Robert G. , Osburn James O. 
Published: June 2004

AbstractA digital computer solution of the equations of fluid motion predicts the pressures in an expansible tube through which liquid is flowing.To obtain a stable solution, it is necessary to assume that the rate of change of area with time is proportional to the rate of change of velocity with time. This assumption is shown to be a reasonable one.Calculations for the rate of travel of pressure pulses are in good agreement with experimental results.
Free convective effects on stokes flow mass transfer
Authors: Pearson R. S. , Dickson P. F. 
Published: June 2004

AbstractFree convective effects on forced convective mass transfer in the Stokes flow region were studied experimentally by using a single drop in a liquid‐liquid system.Liquids used to form the drops were methyl acetate or 2‐ethoxyethyl acetate with distilled water as the continuous medium. Spherical drops were formed on the capillary tip of a 0.58 cm. O.D. capillary glass tube centered in a 2.5 cm. O.D. pyrex tubular flow cell.Results are presented graphically as NSh vs. NPe, NSh vs. NRe, and NSh/NRa1/4 vs. NPe to show the variation of mass transfer with flow rate and free convection. The range of variables was 10 ≤ NPe ≤35,000; 0.1 ≤ NRe ≤ 30; 578 ≤ NSc ≤ 1,149; and 12.3 ≤ NGr ≤ 75.7.Satisfactory comparisons were also made with other investigators' findings.Results substantiate that at low flow rates (Reynolds number < 10, Peclet number < 1,000) free convective effects either reinforce or interfere with mass transfer. This interference takes place until flow becomes high enough to overcome interfering effects of free convection.
The pseudoparticulate expansion of screen‐packed gas‐fluidized beds
Authors: Capes C. E. , McIlhinney A. E. 
Published: June 2004

AbstractA study has been made of the expansion characteristics of beds of uniformly sized spherical particles of lead, nickel, sand, glass, and plastic that have been fluidized with air, carbon dioxide, and helium in columns packed with open‐ended cylindrical screen packing. The addition of packing to a gas‐fluidized bed limits the bubble size, prevents slugging and allows beds of high aspect ratio to expand smoothly in a manner similar to the behavior of liquid‐fluidized beds. Moreover, much of the experimental data for gas‐fluidized screen‐packed beds have yielded straight lines on a Richardson‐Zaki type of plot, again similar to the expansion of liquid‐fluidized beds. The conditions necessary for this pseudoparticulate behavior in packed gas‐fluidized beds are discussed. A correlation, based on the analysis given by Richardson and Zaki for liquid‐fluidized beds, is proposed to relate bed porosity with gas velocity, density and viscosity, particle size and density, and bed diameter.
Calorimetric determination of the isothermal effect of pressure on the enthalpy of methane and two methane‐propane mixtures
Authors: Dillard D. D. , Edmister W. C. , Erbar J. H. , Robinson R. L. 
Published: June 2004

AbstractBy using an isothermal throttling calorimeter, built for recirculating vapor operation, the effects of pressure on the enthalpy of methane and two methane‐propane (93.9 and 86.2% methane) mixtures were measured. Pure methane was run at 150°F. and the two mixtures were studied at 90, 150, and 200°F. The pressures for these experiments were 500, 1,000, 1,500, and 2,000 lb./sq.in.abs.The resulting data were compared with similar data from other sources for these same systems and conditions. Agreement is good with enthalpy values obtained from both experimental volumetric and Joule‐Thomson data.Prediction methods for the isothermal pressure effect on the enthalpy are compared with these data. These methods demonstrate the reliability of the Redlich‐Kwong and Benedict‐Webb‐Rubin equations and Pitzer's corresponding states correlation for calculating isothermal enthalpy changes for these systems and conditions.
Bounding chemical reactor transients by estimation of growth or decay rates
Authors: Wang F. S. , Perlmutter D. D. 
Published: June 2004

AbstractIf the transient equations of a plug flow tubular reactor are transformed into a set of corresponding ordinary differential equations, stability information for the former may be obtained graphically from knowledge about the transients of the latter. The analysis presented in this paper combines this simplification with the definitions and theorems of Weiss and Infante to propose a method of direct computation whereby transient bounds may be found for this important class of distributed‐parameter chemical reactor systems.
A theory of laminar flow stability
Authors: Hanks Richard W. 
Published: June 2004

AbstractThe success enjoyed by a laminar flow stability parameter that I previously developed as a generalization of the critical Reynolds number of laminar turbulent transition has occasioned considerable interest in the phenomenological theory underlying the parameter. In this paper an analysis of laminar flow stability is presented which leads naturally to the parameter in a much different manner than originally proposed. The stability parameter is seen to represent the coupling ratio between the rate of change of angular momentum of a deforming fluid element and its rate of loss of momentum by frictional drag. At a certain critical value of this coupling ratio, the element becomes unstable to rotational disturbances. If such disturbances are present, the basic nonlinearity of the momentum transfer process guarantees rapid amplification and generation of a turbulent eddy. The consequnces of the theory are examined for two special fixed boundary classes of motion. The physical interpretation of the parameter is compared with conventional interpretations of the Reynolds number and found to be more fundamentally sound. The application of the theory to moving boundary flows, such as the Couette viscometer, is also discussed and an important physical difference is pointed out.
Mass transfer driving forces in packed and fluidized beds
Authors: Wilkins George S. , Thodos George 
Published: June 2004

AbstractThe evaporation of n‐decane into air from the surface of Celite particles, has been used for the establishment of mass transfer factors for both packed and fluidized bed systems. For these calculations log mean partial pressure differences were used. Actual concentration profiles of the transferable component were also experimentally measured by monitoring, at different bed heights, the concentration of n‐decane vapor present in air used as the carrier gas. This was made possible through the use of an extremely sensitive hydrocarbon analyzer. The resulting profiles were used to obtain, by graphical integration, the actual driving force prevailing for each run. A nearly one‐to‐one correspondence was found to exist between the actual driving force and the corresponding log‐mean value for both packed and fluidized bed runs.
Sensitivity of a class of distributed parameter control systems
Authors: Seinfeld John H. 
Published: June 2004

AbstractA sensitivity matrix is defined as a measure of trajectory deviations to small parameter variations of both open and closed loop controlled nonlinear parabolic and first‐order hyperbolic systems. In general the parameters may enter through the system equations or the boundary conditions and may be time or spatially dependent. The introduction of a positive measure of the sensitivity, the norm of the sensitivity matrix, into the performance index is shown to be effective in limiting the trajectory deviations due to the parameter variations. The open and closed loop control of a double pipe heat exchanger is analyzed with the open loop problem solved by an approximate procedure. The sensitivity reformulation is successful in reducing trajectory sensitivity, however at the cost of decreased overall performance.
Surface rheological properties of foam stabilizers in nonaqueous liquids
Authors: Mannheimer R. J. 
Published: June 2004

AbstractThe rheological properties of foam stabilizers have been measured with an improved canal viscometer that provides absolute values of surface shear viscosity and yield strength. Studies conducted in room air confirmed previous reports of complex non‐Newtonian film properties for oil soluble surfactants at the air‐oil interface. Both shear and time dependent behavior were observed in which the apparent surface viscosity increased with decreasing rotational speed. Surface viscosities were low at all fresh interfaces but generally increased with the age of the surface over a period of several hours to several days. Experiments conducted in a controlled humidity environment have established that the phenomenon of aging in room air is due to adsorption of moisture from the gas by the surfactant film. Preliminary results indicate that the shear dependency of films in a high humidity environment can be approximated by a Bingham Plastic model which characterize their rheological behavior in terms of a Newtonian surface viscosity and yield value.
A theoretical study on diffusion in pulsating flow
Authors: Fagela‐Alabastro Estrella B. , Hellums J. D. 
Published: June 2004

AbstractA theoretical study has been made on the effect of pulsations in the flow field on interphase mass transfer. The phenomenon is of interest in studies of the cardiovascular system as well as in traditional engineering applications. The physical situation studied corresponds to fully developed flow in a long conduit with a periodic pressure gradient. The mass transfer problem was solved analytically for low amplitude pulsations for the two limiting cases of very small and very large frequencies. In addition, several numerical solutions were developed in the intermediate region where the asymptotic solutions are least accurate. The solutions taken together give a good quantitative overall view of the phenomenon.One of the most interesting and unexpected results is that at very low frequencies it is possible for a pulsatile flow to yield a lower interphase mass flux than a steady Poiseuille flow with the same velocity.
Stability of high dimensional nonlinear systems using Krasovskii's theorem
Authors: Berger Albert J. , Lapidus Leon 
Published: June 2004

AbstractLiapunov's direct method is used to establish a finite region of asymptotic stability for nonlinear systems with an arbitrary number of state variables. The procedure is a geometric one in multidimensional space which uses the Fletcher‐Powell minimization technique to find the maximum time derivative of the Liapunov function on the closed Liapunov hypersurface. Three detailed examples are presented, the first being the classical 2‐variable CSTR with heat transfer and the third being a 32‐variable 16‐stage model of an adiabatic tubular reactor with axial diffusion.