bluuebunny/crossref_metadata_2025_split huggingface dataset:
Longitudinal dispersion of liquid flowing through fixed and fluidized beds
Authors: Chung S. F. , Wen C. Y. 
Published: June 2004

AbstractLongitudinal liquid mixing in fluidized and fixed beds was studied using sinusoidal and pulse response techniques. The tracer used was light emissive fluorescein dye. A systematical study of liquid phase dispersion by varying particle size, fluid velocity, fraction voids, and particle density was conducted. A generalized correlation applicable to both fixed bed and fluidized bed was obtained. The application of the correlation in predicting the effect of the dispersion on reactor performance was discussed.
Effect of imperfect mixing on autorefrigerated reactorstability
Authors: Luben W. L. 
Published: June 2004

AbstractThis paper discusses the effects of imperfect mixing on the stability of autorefrigerated chemical reactors. Mixing is shown to strongly influence stability in these evaporatively‐cooled systems. A modified van Heerdensteady state stability analysis is presented. Computer simulation of a typical system illustrates the occurrence ofrunaways and local hot spots. Both continuous stirred tank reactors and batch reactors are considered.
Stability of numerical integration techniques
Authors: Distefano G. P. 
Published: June 2004

AbstractThis paper presents the cause of instabilities which arise during the numerical solution of ordinary differential equations. By using the numerical integration routines presently available, one actually approximates the differential equation by a difference equation. If the difference equation is of a higher order than the original differential equation, the approximate solution contains extraneous solutions which are not at all related to the true solution. It is the behavior of these extraneous solutions that one is usually concerned with in a stability analysis.Also presented is a procedure for obtaining a bound on the largest allowable integration step size for a class of chemical engineering problems. A detailed explanation of the procedure is illustrated for unsteady state distillation calculations.
Effects of pore diffusion in the catalytic oxidation of ethylene
Authors: Caretto L. S. , Nobe Ken 
Published: June 2004

AbstractEffects of pore diffusion in the catalytic oxidation of ethylene on copper oxide‐alumina have been studied by varying the catalyst size and maintaining constant the ratio of the tube to the pellet diameter. Hydrocarbon analysis was determined with a flame ionization detector; infrared analyzers were used to determine carbon monoxide and carbon dioxide concentrations. Other reaction products were analyzed with a gas chromatograph. Curvature of the Arrhenius plots and increase in reaction order with temperature indicated a transition region between kinetic control at lower temperatures and pore diffusion control at higher temperatures. A calculation procedure which was developed to predict the conversion considering pore diffusion effects provided satisfactorily agreement between calculated and experimental results.
On the particle size distribution function and the attrition of cracking catalysts
Authors: Gwyn J. E. 
Published: June 2004

AbstractThe rate of attrition of a catalyst sample, of a single particle size, can be expressed by a simple function of initial diameter and time. The initial rate is a function of initial diameter, whereas the decrease in attrition rate of a catalyst of a given size as it ages depends only on time.The attrition equation for a single size of particles is introduced into the particle size distribution function and, through mathematical analyses, yields a relationship for the attrition of a full size‐range catalyst. The form of this relationship, which includes terms for attritability and severity of attrition conditions, is verified by laboratory and commercial attrition data on two full‐range catalysts. The size distribution of an attrited sample is not expressible in simple analytical form, but is readily obtained by numerical analysis.
Evaluation of drying schedules
Authors: Peck Ralph E. , Kauh Jae Y. 
Published: June 2004

AbstractA generalized drying program that can simulate any drying conditions has been solved on a computer. The program includes the variation of humidity, temperature, and wind velocity over drying material. These three variables can be treated as functions of time. The correlations require knowledge of several basic properties of the material to be dried and were solved for the case of one directional heat and mass flow.The computer calculated results are checked with experimental data. The effective diffusivity and the solid surface resistance to mass transfer were evaluated by data obtained in three experiments.Solutions for constant drying conditions are presented in graphical form. Variations of such variables as humidity in a drier can be estimated from these curves but the computer program is more reliable.
Oxidation of hydrogen in a helium stream by copper oxide: Analysis of combined film and pore diffusion with rapid irreversible reaction in a fixed‐bed process
Authors: Scott Charles D. 
Published: June 2004

AbstractDifferential equations were derived to describe the system characterized by a rapid, irreversible reaction of a fluid species in a flowing fluid with a fixed bed of solids in which the reaction rate was controlled by mass transfer of the reacting fluid from the bulk fluid to the reaction site in the solid. Two kinds of mass transfer resistances were assumed, external or film diffusion resistance, and internal pore diffusion resistance. The set of differential equations were solved by a finite‐difference method for both the generalized case and for the specific case of reaction of hydrogen in a stream of helium with fixed beds of copper oxide pellets.The hydrogen‐copper oxide reaction is one step in a proposed method for removal of hydrogen as a contaminant in the helium coolant of nuclear reactors. This reaction was experimentally investigated in tests with both differential and deep beds of copper oxide in the temperature range of 400 to 600°C., at pressures of 10.2 to 30.0 atm., with gas mass flow rates of 0.0050 to 0.050 g./sq.cm.‐sec, and with inlet hydrogen concentrations of 0.0008 to 1.21 vol. %. These tests showed that the system could be described by the two rate‐limiting steps: film and pore diffusion of hydrogen. Differential‐bed tests were used to establish hydrogen transport properties within the porous copper oxide pellets, and tests with deep beds were used to establish external mass transport properties.Generalized breakthrough curves were determined by a computer solution of the mathematical model. These curves can be the basis for design of fixed‐bed copper oxide oxidizers for gas‐cooled, nuclear reactor purification systems and for design of any fixed‐bed system which follows the assumed reaction mechanism.
The growth of single crystals by controlled diffusion in silica gel
Authors: Rubin Bernard 
Published: June 2004

AbstractMonocrystals of calcium tartrate tetrahydrate, neodymium‐doped calcium tartrate tetrahydrate, and cuprous chloride have been grown by controlled diffusion in silica gel using both metathetical and decomplexation reactions. Conditions for the optimum growth of the crystals are given and it is shown how the pH of the gel, the temperature of its formation, the concentration of the reactants which make up the gel, and the concentration of the reactants which result in the crystal are important in attaining good single crystal products. Crystals have been grown up to 11 mm. on edge in three to four weeks, and in many cases take on a form which, to all outward appearances, seem to have been cut and polished.
Oxidation‐reduction reactions in stirred liquid‐liquid systems
Authors: Mansoori G. A. , Madden A. J. 
Published: June 2004

AbstractOxidation‐reduction rates have been determined in stirred liquid‐liquid systems wherein tetravalent cerium ions in a continuous aqueous phase were reduced by tetrachlorohydroquinone contained in dispersed organic droplets. Kinetic data obtained (using low volume fractions (<0.06) of dispersed organic phase) indicate that the rate of reduction of ceric cerium is proportional to the extent of the interfacial area of the stirred liquid‐liquid system. Two possible rate‐limiting mechanisms are discussed to explain the observed kinetic behavior.This liquid‐liquid electron exchange system might find potential use as a chemical tool for measuring changes in interfacial area as influenced by various mixing parameters.
Joule‐Thomson effects in gas mixtures: The nitrogen‐methane‐ethane system
Authors: Ahlert R. C. , Wenzel L. A. 
Published: June 2004

AbstractPressure‐temperature data were obtained along isenthalps for nitrogen, methane, and three ternary nitrogen‐methane‐ethane mixtures. These data were differentiated to obtain Joule‐Thomson coefficients over the temperature range from ambient to 200°K. and at pressures from 165 atm. to about 5 atm. Data for nitrogen was obtained down to 140°K.The resulting Joule‐Thomson coefficients were compared with predictions based on the Beattie‐Bridgeman and Benedict‐Webb‐Rubin equations of state and on the virial equation of state truncated after the third virial coefficient. These comparisons show that the Benedict‐Webb‐Rubin equation could predict the data with a deviation averaging 1.7%. The Beattie‐Bridgeman predictions were highly dependent upon the mixture rules used, with the best set of mixture rules giving an absolute average deviation of 4.8%. Predictions using the virial equation with virial constants obtained from the Lennard‐Jones potential energy function using a geometric mean minimum potential energy deviated from the experimental data by 5%.In all of these comparisons, the virial coefficients of ethane appear to be in greatest uncertainty, and the predictions of mixture data high in ethane least satisfactory. Thus it appears that improved data on the pure components, particularly ethane, are vital to any satisfactory evaluation of mixture properties.
Free volume theory for viscosity of simple nonpolar liquids. Part I. Pure components
Authors: Gubbins Keith E. , Tham M. J. 
Published: June 2004

AbstractAn improved free volume theory is presented, and is shown to predict the variation of viscosity with temperature and pressure satisfactorily for liquids composed of simple, nonpolar molecules, when the density is greater than twice the critical value. Allowance is made for the temperature dependence of the minimum free volume for a jump, and for the density dependence of the activation energy at constant volume. Corresponding states relationships are provided for these quantities, the reducing parameters being the temperature and molal volum at the melting point.
Physical properties of hydrogen sulfide‐water mixtures
Authors: Burgess Mitchell P. , Germann Raymond P. 
Published: June 2004

AbstractCalculations concerning the production of heavy water by the hydrogen sulfide dual‐temperature exchange process require precise data on the physical properties of dry hydrogen sulfide and hydrogen sulfide‐water mixtures for temperatures between 25 and 170°C., and for pressures between 200 and 340 lb./sq.in.abs. However, data on enthalpy of hydrogen sulfide‐water mixtures were not found in the literature, and data published on hydrogen sulfide‐water compositions at equilibrium were given at such large intervals of temperature and pressure that they could not be interpolated accurately enough by ordinary means.

Specific volume and enthalpy of dry, superheated hydrogen sulfide vapor,
Composition of hydrogen sulfide‐water vapor and liquid in equilibrium,
Enthalpy of hydrogen sulfide vapor saturated with water vapor,
Enthalpy of water liquid saturated with hydrogen sulfide vapor,
Deuterium distribution constants for vapor‐liquid equilibrium.
A study was undertaken to express the properties, listed below, with equations suitable for solution on a digital computer and useful in mathematical models of the process.New correlating constants were derived where needed. The equations and typical results are presented in this paper.
Numerical optimization of large interconnected systems
Authors: Davison E. J. , Alas R. 
Published: June 2004

AbstractThis paper describes a numerical procedure for optimizing a large set of interconnected systems with respect to a given index of performance. The method automatically constructs the vector differential equation of the complete system from (a) the vector differential equations describing the behavior of the components of the system and (b) the manner of their interconnection. A hill‐climbing method is then used to select optimum values of the system's parameters to maximize a given index of performance. An example of the procedure applied to a high order system is included.
Optimal control of tubular reactors. Part I. Computational considerations
Authors: Chang K. S. , Bankoff S. G. 
Published: June 2004

AbstractThe necessary conditions for optimization of a system governed by a nonlinear vector first‐order partial differential equation with two (space and time) independent variables, such as governs the unsteady behavior of tubular flow reactors, are derived. Rather general objective functionals and boundary conditions, such as the recycle of unconverted reactant with an appropriate time delay for separation and a free choice of final time, are allowed. A gradient technique in control space is formulated, and it is shown that distinct computational advantages can accrue from the use of the method of characteristics.
Turbulence phenomena in drag reducing systems
Authors: Seyer F. A. , Metzner A. B. 
Published: June 2004

AbstractAn analysis based on the Townsend‐Bakewell model of the eddies in the wall regions of turbulent shear flows shows that viscoelastic fluid properties must lead to significant reductions in the rate of production of turbulent energy. This analysis in turn leads to the proper form of the similarity laws for drag reducing fluids, heretofore deduced empirically.Measurements of the axial and radial turbulence intensities for flow through smooth round tubes are reported, as are measurements of the time‐averaged velocity profiles and the drag coefficients. These indicate that for solutions exhibiting drag reduction at all Reynolds numbers the flow may be transitional to Reynolds numbers of the order of 105. This transitional flow consists of alternating patches of laminar and turbulent fluid, within each of which the flow characteristics are approximately similar to those of Newtonian fluids. At high Reynolds number conditions with the turbulent field fully developed the velocity profile in the core is flatter under drag‐reducing conditions than for turbulent Newtonian fluids, a change dependent on the increased isotropy of the turbulent field of the drag‐reducing fluid. These effects appear to be a result of increases in the time scales of the radial fluctuations caused by the fluid properties.Design calculations based upon the present results suggest that in large diameter pipelines, or in boundary layers on large objects, drag reduction may not be attainable under conditions of practical interest until fluids having relaxation times an order of magnitude larger than those presently available, but with comparable viscosity levels, are developed or, alternately, until fluids exhibiting Weissenberg numbers which do not change with deformation rate, can be found.
Mutually dependent heat and mass transfer in laminar duct flow
Authors: Sparrow E. M. , Chen T. S. 
Published: June 2004

AbstractAn analysis is performed of the strongly coupled heat and mass transfer processes which result from sublimation of mass from the walls of a duct into a flowing gas, the latent heat being provided solely by convective transfer from the gas. The flow is assumed to be laminar and hydrodynamically developed. Results are given for the streamward variations of the bulk and wall temperatures and mass fractions, of the heat and mass transfer rates, and of the local heat transfer coefficient. Representative temperature and mass fraction profiles are also presented. Entrance lengths characterizing the near approach to fully developed conditions are tabulated. Comparisons are made of the present results (based on a parabolic velocity profile) with those based on a slug flow velocity profile. A subsidiary analysis using the Lévěque model is also performed and the results compared with those of the principal solution.
Laminar, nonisothermal flow of fluids in tubes of circular cross section
Authors: Christiansen E. B. , Jensen Gordon E. 
Published: June 2004

AbstractNumerical solutions of the equations of motion and energy are presented in the form of pressure‐loss, flow‐rate relationships for the laminar, nonisothermal flow of Newtonian and non‐Newtonian fluids being heated and cooled in tubes at constant wall temperature. The flow properties are represented by a temperature‐dependent form of the power law equation. The numerical results are shown to be in good agreement with experimental data for a wide range of fluid properties and flow conditions.
Adsorption of carbon monoxide‐nitrogen, carbon monoxide‐oxygen, and oxygen‐nitrogen mixtures on synthetic zeolites
Authors: Danner R. P. , Wenzel L. A. 
Published: June 2004

AbstractExperimental results for the adsorption of the binary gas mixtures oxygen‐nitrogen, oxygen‐carbon monoxide and nitrogen‐carbon monoxide on two synthetic zeolites are reported. In all of these experiments the temperature was −200°F. and the total pressure was 1 atm. Also reported are the isotherms for the three pure gases on the two zeolites at −200°F. The results indicate that these zeolites have a surface selectivity which is independent of any sieving effect based on the size of the adsorbed molecules. It does not appear that the strong separations obtained can be explained in terms of the van der Waals forces which are generally believed to be dominant in physical adsorption. The available methods of predicting binary adsorption data from the pure gas isotherms have been examined.
The effect of surfactants on the flow characteristics of falling liquid films
Authors: Strobel W. J. , Whitaker Stephen 
Published: June 2004

AbstractExperimental values of the wave length and wave velocity have been obtained for dilute solutions of valeric and hexanoic acid for a vertical falling liquid film. The wave length was unaffected by the surfactants for Reynolds numbers in the range 5 to 100; however, the wave velocity was decreased for increased surface concentrations of the two acids. This is in direct contradiction to previous theoretical work, and the explanation for the anomaly is that the free surface velocity is greatly retarded by the adsorption of the surface active agents. In an effort to determine the extent of this retardation, an approximate form of the diffusion equation and the equations of motion were solved subject to boundary conditions describing the effect of the absorbed surfactant on the surface stress. The results indicate that the entrance length can be increased several orders of magnitude by the addition of small amounts of surfactant.
Creeping flow past a fluid globule when a trace of surfactant is present
Authors: Wasserman Melvin L. , Slattery John C. 
Published: June 2004

AbstractThe effects of a trace quantity of a surface‐active agent on creeping flow past a bubble or droplet are investigated. The equations describing mass and momentum transfer are simultaneously solved by a perturbation technique, consistent with the jump mass and momentum balances at the phase interface. The stream function for the velocity distribution is evaluated as an infinite series of spherical harmonics. Galerkin's method, which reduces the partial differential equation of continuity to a set of ordinary differential equations, is used to evaluate the concentration distribution of surfactant.A sample calculation is carried out for relative motion between an air bubble and an infinite body of water which contains a trace of isoamyl alcohol. The relative velocity of the water at an infinite distance from the bubble is found to be highly sensitive to small changes in surfactant concentration from zero, although the bubble varies imperceptibly from a spherical shape.
Low Reynolds number developing flows
Authors: Atkinson Bernard , Brocklebank M. P. , Card C. C. H. , Smith J. M. 
Published: June 2004

AbstractEquations are given that relate the entrance length to Reynolds number for pipe and channel geometries with a flat velocity profile as the initial condition. These equations are linear combinations of the creeping flow and boundary layer solutions. The former is obtained by minimization of the viscous dissipation using the finite element method. The equation for the pipe entrance is shown to be in good agreement with experimental data.
Copolymerization and terpolymerization in continuous nonideal reactors
Authors: Szabo T. T. , Nauman E. B. 
Published: June 2004

AbstractA simple means for predicting composition distributions in copolymers is used to illustrate the strong influence of segregation effects in the reactor. A recycle loop reactor can be used to produce uniform copolymers by narrowing the macroscopic composition distribution, but there is a limiting microscopic distribution which results from probabilistic effects.
A study of the effects of internal rib and channel geometry in rectangular channels. Part I. Pressure drop
Authors: Buonopane Ralph A. , Troupe Ralph A. 
Published: June 2004

AbstractPlexiglas models of rectangular channels were fabricated with various rib shapes to determine the effects of rib and channel geometry on the pressure drop. Pressure drops in twenty‐four individual variations of channel geometry were investigated using plexiglas models.From this investigation, an empirical correlation for the pressure drop across the ribbed section of the channel was determined as a function of the linear fluid velocity and the geometric characteristics of the channels. This empirical correlation involves functions of seven geometric parameters of rib pattern and channel geometry.Ribbed section pressure drops for commercial plate heat exchanger channels were predicted using the geometric characteristics of the commercial plates with the empirical correlations developed from the plexiglas channel studies. The total pressure drop for commercial channels was predicted by adding an average entrance and exit pressure drop to the predicted ribbed section pressure drop.The correlations developed in this work allow one to determine the pressure drop in a ribbed rectangular channel from the geometric characteristics of the ribs and the channel in question.
The flow characteristics of swirl (centrifugal) spray pressure nozzles with low viscosity liquids
Authors: Dombrowski Norman , Hasson David 
Published: June 2004

AbstractA study has been made of the mechanics of flow of low viscosity liquids through swirl spray nozzles. Discharge coefficients and spray angles have been measured for a series of nozzles designed to systematically determine dimensional effects not predicted by frictionless theory, in particular the effect of the ratios of swirl chamber diameter to orifice diameter and of orifice length to orifice diameter. It was found that a unique relationship exists between discharge coefficient and spray angle dependent only upon the value of the orifice length/diameter ratio. This result has been explained on the basis of an ideal flow theory extended to take into account the frictional decay of the vortex motion. A general expression has been derived which permits correlation of the flow characteristics of nozzles covering a wide range of designs.