bluuebunny/crossref_metadata_2025_split huggingface dataset:
A study of unidirectional versus tridirectional heat flux models and the effect of particle size on heat conduction in composite solids
Authors: Fidelle Thomas P. , Kirk R. S. 
Published: June 2004

AbstractThe effect of the assumption of unidirectional heat flux was determined for a well‐known unit cell model used to predict effective thermal conductivities of particulate composites. Predictions obtained for the condition of unidirectional heat flux were compared with those obtained for the more rigorous case of tridirectional heat flux. The latter case required a digital simulation of the model to obtain three‐dimensional temperature distributions. Comparisons were made for two different values of pure component thermal conductivity ratio and for a broad range of phase compositions. Results in each case suggest that the unidirectional heat flux assumption is not a serious limitation.Experimental studies were made of the effects of composition, particle size, and pure component thermal properties on the effective thermal conductivity of three different composite systems. Cylindrical samples of each system were cast from various proportions of their basic constituents. Effective thermal conductivities were calculated from effective thermal diffusivities. The latter were obtained experimentally from the thermal response of the center of each composite sample as it was cooled from room temperature to 0°C. by means of an agitated ice bath. Effective conductivities so obtained were compared with conductivities predicted by the tridirectional simulation and three previously published models. Results show that a recent model that utilizes unidirectional heat flux but permits random phase distribution provides the best predictions of the experimental data presented in this work.Results of the particle size study indicate that there is a minimum ratio of system dimension to particle dimension below which a particulate composite can no longer be considered macroscopically homogeneous and isotropic.
Boundary‐layer flow on a rotary vane
Authors: McCarthy H. E. , Olson J. H. 
Published: June 2004

AbstractThe boundary‐layer flow on a rotating vane is investigated with the integral momentum approximation. A parabolic velocity profile is approached over a significant portion of the vane. The assumption of a parabolic velocity profile yields a closed analytical solution for the radial dependence of the surface velocity. Experimental data obtained agree with the predicted average velocity at the exit of the vane.
The motion of vapor bubbles growing in uniformly superheated liquids
Authors: Pinto Yuda , Davis E. James 
Published: June 2004

AbstractThe motion of simultaneously rising and growing vapor bubblesin a uniformly superheated liquid is analyzed, and the predicted bubble velocities are shown to be in good agreement with available data. Using a quasisteady state approximation to describe the drag, and existing bubble growth theory to describe the growth rate, the equation of motion is solved for two ranges of bubble size encountered in nucleate boiling. For smaller bubbles (R<0.04 cm.) an analytical solution is obtained, and for larger bubbles (R>0.07 cm.) a numerical solution and analytical asymptotic solutions are obtained.
The stability and dynamic behavior of a continuous crystallizer with a fines trap
Authors: Lei Shang‐Jen , Shinnar Reuel , Katz Stanley 
Published: June 2004

AbstractWorking equations are developed for the operation of a continuous crystallizer with a fines trap. A linearized stability analysis reveals that proper operation of the fines trap can stabilize the crystallizer at large crystal product sizes that would otherwise lead to instability. Dynamic studies for the full nonlinear equations are carried out numerically, and stable limit cycles are exhibited around unstable equilibrium points.
Removal of colloidal pollutants by microflotation
Authors: Cassell E. Alan , Matijevíc Egon , Mangravite Francis J. , Buzzell Timothy M. , Blabac Stephen B. 
Published: June 2004

AbstractThe removal of various colloids (humic acid, silica, polystyrene latex, and bacteria) by microflotation in the presence of aluminum salts has been studied as a function of pH. The conditions for efficient separation have been correlated to the stability of these colloids, and it was shown that in all cases rapid flotation occurred when the aluminum salt concentration and the pH adjustment rendered the sols unstable. Particularly high removals were observed over the pH range of aluminum hydroxide floc formation. Microflotation could be utilized as a nonspecific method for simultaneous removal of mixtures of colloidal pollutants.
Multicomponent mass transfer in turbulent flow
Authors: von Behren G. L. , Jones W. O. , Wasan D. T. 
Published: June 2004

AbstractA general treatment of entry region multicomponent mass transfer between a fully developed turbulent flow and a smooth pipe wall has been developed from a basis first derived by Toor.The couled multicomponent equations were reduced to an equivalent binary system by the method of undetermined constants. Numerical solutions for a forced convection, binary diffusion system involving gas‐phase, nonequimolal diffusion were applied to a ternary system. These solutions have been found to compare well with these authors entry region mass transfer data on a ternary acetone‐methonal‐air mixture and with the earlier analogy theories derived for the case of an infinitely long test section.We conclude that there is a significant interaction in some multicomponent systems, enough that the binary theory can not be satisfactorily applied in the design of multicomponent mass transfer systems.
Radiation efficiency of photoreactors
Authors: Hancil V. , Schorr V. , Smith J. M. 
Published: June 2004

AbstractTheoretical expressions are derived for the fraction of the energy, emitted from a UV lamp, which strikes the reactor wall in systems where a reflecting surface is included. Two geometries used in photoreactors are considered: a cylindrical lamp located at the focus of a superimposed parabolic reflecor. The predicted efficiencies are low, particularly for the elliptical reflector—reactor system, because of the energy that escapes through the ends of the system. Experimentally determined efficiencies for the elliptical type are in reasonable agreement with predicted values, suggesting that the theoretical method may be used for estimating efficiencies for different reactor systems.
Effect of inert venting on the stability of autorefrigerated batch reactors
Authors: Luyben W. L. 
Published: June 2004

AbstractRemoval of the exothermic heat of chemical reactons by autorefrigeration (vaporization of a liquid phase) is frequently used in continuous and batch chemical reactors. The vapor thus generated is usually liquified in a condenser and the condensate returned to the reactor.This paper studies the effects of the formation of an inert gas by‐product on the stability and control of batch autorefrigerated reactors.Stability is shown to be strongly influenced by the production of these inerts because their buildup in the condenser reduces heat removal capacity. Inert buildup can be reduced by venting, but excessive venting results in a loss of not only inerts but also of the volatile components in the system. This leads to higher reactor temperaturs, faster reaction rates and instability.Digital simulation of a numerical example illustrates the effects of various parameters.
The permeation of carbon dioxide, oxygen, and nitrogen through weakly basic polymer membranes
Authors: Tajar Joseph G. , Miller Irving F. 
Published: June 2004

AbstractPermeation, diffusion, and solubility coefficients were measured for carbon dioxide, O2 and N2 in the four component membrane system, polyethlenimine–polyvinylbutyral—epoxy (Epon 834)—water, using a variable pressure technique. Extremely high CO2/O2 and CO2/N2 selectivity ratios were obtained. This can be attributed to reversible reactions between the carbon dioxide, water, and polyethylenimine which markedly increases the carbon dioxide solubility in the membrane with respect to those of O2 and N2. The O2 and N2 permeation occurs in the classical manner.The high carbon dioxide selectivity coupled with the good O2 permeability of this membrane makes it potentially useful in an atmospheric control system or in a blood oxygenator.
Kinetics of propane pyrolysis
Authors: Herriott G. E. , Eckert Roger E. , Albright Lyle F. 
Published: June 2004

AbstractA kinetic model based on the most important free radical reaction steps has been developed for propane pyrolysis. The kinetic and product distribution data were obtained over a wide range of conversions at temperatures from 700 to 850°C. and with various amounts of steam or other diluents. The results of the investigation clarify the important reaction steps and the effect of the critical operating variables.
Vapor‐liquid equilibrium in alcohol‐water systems containing dissolved halide salts and salt mixtures
Authors: Meranda David , Furter William F. 
Published: June 2004

AbstractIsobaric vapor‐liquid equilibrium data at atmospheric pressure are reported for 17 systems, each consisting of water, an alchol (methanol or ethanol), and either a salt or a mixed pair of salts having a common anion, dissolved to saturation in the boiling liquid phase. The matris of four salts employed consisted of the sodium and potassium bromides and iodides. Solubility data are reported in terms of saturation salt concentration as a function of alcohol‐water proportionality in the liquid.Some of these salts and salt mixtures were found capable of eliminating the ethanol‐water azeotrope completely. Relative volatility was observed to be enhanced by as much as threefold in certain cases. Orders of effectiveness of both the cations and anions were in agreement with those observed by previous investigators of the effects of electroytes in mixed solvents. The value of the salt effect parameter was observed to undergo major variation as a function of alcohol‐water mixed solvent proportionality in the methanol‐water‐salt systems, but to be remarkably constant throught the ethanol‐water‐salt systems. Synergistic effects of mixed salts on vapor‐liquid equilibrium were observed in certain systems despite their apparent lack in the corresponding salt solubility relationships. In systems where synergistic effects did exist they were found to be dependent stronly on liquid composition, largely lacking in water‐rich regions, and evident only in midrange and alcohol‐rich regions of binary solvent composition. In some of these systems the salt appeared to cause both salting out and salting in of the alcohol in differing composition regions of the same system, the predominating effect depending on the relative proportions of alcohol and water present. This latter effect is in general contradiction with the accepted theories of salt effect in vapor‐liquid equilibrium.
Activity coefficients at infinite dilution for ternary system
Authors: Kojima Kazuo 
Published: June 2004

AbstractA simple thermodynamic expression determining the infinite dilution activity coefficients from the dew point isobar is presented. A flow method measuring the dew point temperature for ternary and binary isobaric systems is proposed. An analysis determining the infinite diluvion ternary activity coefficients for ethanol‐isopropyl alcohol‐water system at 1 atm. is illustrated.
Analysis of entrance and exit effects in a falling cylinder viscometer
Authors: Chen M. C. S. , Swift G. W. 
Published: June 2004

AbstractA variational method has been used to study the entrance and exit effects in a falling cylinder viscometer for creeping and noncreeping flow. The computed result indicate solution convergence for NRe less than 100 and agree with experiment within ± 0.5% for NRe less than 25.
Radiative transfer through a cloud of absorbing‐scattering particles
Authors: Sanders C. F. , Lenoir J. M. 
Published: June 2004

AbstractAn experimental study was made of radiative transfer through a plane‐parallel enclosure of micron‐sized, sphercal aluminim oxide particles and flake‐like graphit particles. By suspending the particles in both carbon tetrachloride and carbon disulfide, transmission measurements were made at wave lengths from 2 to 11 microns with both collimated and diffuse incident radiation. In correlating the diffuse results, the two‐flux model was rearranged so that the cloud transmission was experessed in terms of two cloud scattering parameters. The values of the scattering parameters as determined from the data were correlated with the properties of the cloud.
Thermodynamics of multicomponent reactive nonuniform systems (adsorption)
Authors: Brunet Jean 
Published: June 2004

AbstractCertain systems are characterized by a nonuniform distribution of matter in space. Examples of such systems are liquid‐fluid (1 to 3) and the solid‐fluid interfaces (4). It is the main purpose of this paper to extend thethermodynamics of nonuniform systems to multicomponent reactive mixtures in the presence of an external field and to apply the above formalism to physical adsorption. This amounts to an extension of Hart's original analysis (5 to 7) as well as an improved analysis of the solid‐fluid interface presented recently by Metiu and Ruckensteein (8). Furthermore, various approximate solutions for the solid‐fluid interface are considered, all of which reduce properly to known results.
Optimal feedback control of a class of linear tubular processes
Authors: Lim H. C. , Fang R. J. 
Published: June 2004

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 needed.
Local and macroscopic thermal transport from a sphere in a turbulent air stream
Authors: Galloway T. R. , Sage B. H. 
Published: June 2004

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 transfer.
The role of the liquid phase in the performance of a trickle bed reactor
Authors: Satterfield Charles N. , Way Peter F. 
Published: June 2004

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 limitations.
Stability studies in pipe flows unsing water and dilute polymer solutions
Authors: Berman Neil S. , Cooper Eugene E. 
Published: June 2004

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 effects.
Friction coefficients and self‐diffusivity reduced state correlations and interrelationship
Authors: Ramanan P. , Hamrin C. E. 
Published: June 2004

AbstractTheretical equations for the transport properties of donse gases and liquids require knowledge of the contact pair‐correlation function g2 (σ) and the friction coefficient ζ. Usually this latter quantity is made up of a hard‐core contribution ζH and a soft‐repulsion contribution ζS. Correlations are presented for the reduced friction coefficients ζrH, ζrS, and ζr in terms of reduced density ρ* and reduced temperature T*. These correlations were found to predict the dependence of self‐diffusivity of several substances on temeratures and density in the dense gas region.
Interactions of inter‐ and intraphase gradients in a diffusion limited catalytic reaction
Authors: Kehoe J. P. G. , Butt J. B. 
Published: June 2004

AbstractThe experimental measuremet of inter‐ and intraphase temperature gradients in a single pellet reactor for the Ni‐kieselguhr catalyzed benzene hydrogenation reaction is described. Experimental variables were temperature, feed composition, flow rate (hence heat and mass transfer coefficients) and intrinsic catalytic activity. All parameters required for carrying out calculations were either measured in separate experiments or compared with available independent information. The rather complex interactions between inter‐ and intraphase gradients are well represented by the theory except at conditions of high reaction rate and low convective transport rate. The discrepancies observed at these conditions are apparently due to the development of nonuniform external boundary layers.
Local stability of tubular reactors
Authors: Clough David E. , Fred Ramirez W. 
Published: June 2004

AbstractLiapunov analysis techniques employing a general quadratic functional are used to derive stability conditions for tubular reactor systems. The adiabatic tubular reactor without axial dispersion is shown to be locally stable, which excludes the possibility of multiple steady states, and the reactor with axial dispersion is proven locally stable if a condition involving only system parameters and steady state values is satisfied. Peclet numbers for heat and mass transfer are not specified equal for the latter proof.Results of simulation studies are used to confirm the validity of the derived stability condition, and it is shown that the parametric region of multiplicity is quite well defined. For the nonlinear equations, single steady state cases appear to possess nonuniform stability.
A method of representing the nonisothermal effectiveness factor for fixed bed calculations
Authors: Jouven J. G. , Airs Rutherford 
Published: June 2004

AbstractA parametric representation of the effectiveness factor for a first‐order, nonisothermal irreversible reaction in a catalyst pellet has geen devised that amply covers the realistic range of parameters for the exothermic case. Given the Thiele modulus, Prater temperature, and dimensionless activation energy, the effectiveness factor can be recovered in about 1/1000 sec. (CDC 6600) to an accuracy of better than 5% over most of the range. When heat and mass transfer resistance at the surface is added the time required is about 0.03 sec. This makes fixed bed calculations more than 50 times faster than would otherwise be possible.
Mass transfer of water from single thoria sol droplets fluidized in 2‐ethyl‐1‐hexanol
Authors: Clinton S. D. , Whatley M. E. 
Published: June 2004

AbstractThe rate at which water is extracted from thoria sols was investigated by fluidizing single thoria sol droplets in 2‐ethyl‐1‐hexanol (2EH) and measuring the diameter of a droplet over a period of time until shrinkage no longer occurred. Diameter data from both water and sol drops were obtained at 25°C. The experimental variables were initial drop diameter (0.1 to 0.2 cm), sol molarity \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm (0 to 2}{\rm .5 }\underline M {\rm ThO}_{\rm 2}) $\end{document}, and water concentration in the 2EH (2–12 mg./cc.). The water and sol droplet data were correlated by Equation (5). The single relationship for the fluidized water and sol drops verified that an organic‐phase film surrounding the drop is the rate‐controlling resistance. The sphere Reynolds number was based on the approach velocity and varied from 0.4 to 14. The Schmidt number for the system was fixed at 35,700. During the extraction of water, the mass transfer coefficients for fluidized sol drops were found to depend only on the molarity of the sol. By expressing the mass transfer coefficients as a function of the density difference between the aqueous sol and the organic phase, an equation was derived to predict the gelation time required for any initial sol molarity and drop diameter fluidized in 2 EH at 25°C.
Experimental determination of residence time distributions on commercial scale distillation trays using a fiber optic technique
Authors: Bell Richard L. 
Published: June 2004

AbstractA fiber optic technique for obtaining multiple, simultaneous, point residence time distributions on operating, commercial scale distillation trays is described. The method has sufficient resolution to yield residence time profiles on the tray and to separate tray and downcomer effects. The results indicate severe flow nonuniformities on the tray, which are not accounted for in present models of distillation.