bluuebunny/crossref_metadata_2025_split huggingface dataset:
Particle attrition in shear flow of concentrated slurries
Authors: Karabelas A. J. 
Published: June 2004

AbstractA first order kinetic formulation of brittle particle attrition is suggested. Experimental data show that it applies to coal particle attrition in Couette flow. These data reveal that particles are reduced by loss of surface protuberances, which are much smaller than their mean diameter. It is also shown how changes of the size spectrum, due to shearing, can be predicted.
Geothermal chemical engineering
Authors: Axtmann Robert C. , Peck Lawrence B. 
Published: June 2004

AbstractA major, national program to exploit geothermal energy requires creative chemical engineering solutions to a wide array of difficult problems. With some overlap, most of the problems fall into these categories: resource development and management, energy extraction and utilization, power cycle design and optimization, environmental engineering, and corrosion and scaling of equipment. Reinjection of waste fluids, insofar as it proves feasible, will affect the shape of the solutions in all categories.Convective hydrothermal reservoirs, the most accessible and well characterized of geothermal resources, are immense, permeable media in which heat and mass transport are coupled with chemical reaction. Despite decades of effort, no satisfactory physical or mathematical model exists for any reservoir. Even less is known about the hot rock and geopressured resources, which also may be utilized ultimately.Electric power production receives primary emphasis in the United States, both in terms of current utilization and of research and development. Worldwide, however, the total power devoted to agricultural activities, space heating and cooling, and process heat applications is greater than that to electric power conversion.Because hydrothermal reservoirs are low temperature (<350°C) sources of corrosive fluids, much current development effort aims at power cycles that promise enhanced efficiencies and that avoid some of the problems of corrosion and scaling. Among the candidates are several binary cycles which employ secondary working fluids, and the total flow concept, which utilizes two‐phase flow from the production wells.Once thought to be all but negligible, the environmental effects of geothermal installations have recently been subjected to informed scrutiny and found nonnegligible. Among the problem areas are gaseous effluents including hydrogen sulfide, mercury, radon, ammonia, and H3BO3 and aqueous emissions that contain heavy metals. Reinjection of waste geothermal fluids would ameliorate many environmental impacts but could be complicated by silica deposition in equipment and in the underground reservoir.
Dynamics of aerosol coagulation and condensation
Authors: Ramabhadran T. E. , Peterson T. W. , Seinfeld J. H. 
Published: June 2004

AbstractThe dynamic behavior of aerosol size distributions under the influence of coagulation and growth by heterogeneous condensation of gaseous species is studied. Analytical solutions are obtained to the integro‐differential equation governing the aerosol size distribution density function. Two modes of coagulation (constant and linear coagulation constants) and two modes of condensation (growth independent of particle volume and linearly dependent on particle volume) are considered. The interaction of the two growth mechanisms on aerosol size distributions is elucidated.
A test particle approach to flow classification for viscoelastic fluids
Authors: Tanner Roger I. 
Published: June 2004

AbstractThe formulation of the Deborah and Weissenberg dimensionless numbers for viscoelastic fluids by means of a scheme based on the response of hypothetical tracer test particles having the form of elastic dumbbells is presented. By considering the dynamics of these test particles, we can classify flows as being either strong or weak. Consideration of the amount of stretching of a swarm of dumbbells in one relaxation time also provides a definition of the Weissenberg number. A simple workable definition of the Deborah number is given, and, finally, the ideas are applied to a viscoelastic lubrication case, to an inlet flow, and to the flow through porous media.
Separation sequence synthesis by a predictor based ordered search
Authors: Gomez M. Alejandro , Seader J. D. 
Published: June 2004

AbstractA predictor based ordered search procedure is used to scan the graph representing all possible separation sequences for a given multicomponent separation process. The algorithmic procedure is expedited by utilizing an heuristic cost function to obtain lower bound estimates of the cost of separators not yet designed. Considerable reduction in search space occurs. Optimal and near optimal sequences are readily generated.
Application of the limiting current method to mass transfer in packed beds at very low reynolds numbers
Authors: Appel Peter W. , Newman John 
Published: June 2004

AbstractThe limiting current technique is used to obtain mass transfer coefficients at very low Reynolds numbers (Re < 0.1) in a packed bed consisting of stainless steel spheres. The data show that for Re < 0.015, the Nusselt numbers are below those predicted by existing empirical correlations. The results are discussed in the light of some mathematical models for packed beds reported in the literature and show semiquantitative agreement with the values predicted by Sorensen and Stewart (1974a).
The interfacial drag and the height of the wall layer in annular flows
Authors: Henstock William H. , Hanratty Thomas J. 
Published: June 2004

AbstractA method to predict the height of the wall layer and the interfacial drag in annular flow under conditions that the flow rate of the entrained liquid is known is developed from measurements on air‐water flow in circular tubes. Flow conditions are found to be characterized by a generalized Martinelli flow parameter.
Explaining solubilization kinetics
Authors: Chan A. F. , Evans D. Fennell , Cussler E. L. 
Published: June 2004

AbstractSolubilization rates of fatty acids in pure detergent solutions are controlled by mixed micelle desorption and diffusion. Solubilization rates in partially saturated detergent solutions also involve exchange of fatty acids between the solid and the solution. These conclusions depend on models like those used in gas‐solid catalysis and in tracer diffusion.
The effect of flow maldistribution on conversion in a catalytic packed‐bed reactor. Part I. Analysis
Authors: Choudhary Manoj , Szekely Julian , Weller Sol W. 
Published: June 2004

AbstractThrough the statement of the vectorial form of the Ergun equation, combined with a differential component balance, a formulation was developed describing the velocity fields and reactant concentration profiles in an isothermal packed‐bed reactor in which the gas flow is nonuniform. This flow maldistribution was caused by both the preferential flow near the wall, inherent in most systems, and by the deliberate arrangement of the solid packing in the bed. The numerical solution of the governing equations showed that a nonuniform flow field had a very strong effect in distorting the concentration isopleths, particularly at intermediate conversion levels.
Simulation of an electrochemical carbon dioxide concentrator
Authors: Abdel‐Salam Omar E. , Winnick Jack 
Published: June 2004

AbstractThe performance of an electrochemical device for the concentration of carbon dioxide from the atmosphere of a spacecraft cabin is analyzed. The removal rates as well as the concentration distributions of the different species are calculated for any set of operating conditions by a model which embodies the fundamental electrolyte properties and design parameters.
Enzymatic regeneration of ATP. I. Alternative routes
Authors: Langer Robert S. , Hamilton Bruce K. , Gardner Colin R. , Archer Michael C. , Colton Clark K. 
Published: June 2004

AbstractProspects for enzymatic synthesis processes on an industrial scale depend upon development of a practical process for ATP regeneration. The relative merits of various routes to ATP regeneration involving chemical synthesis, whole cells or organelles, or cell free enzymes are evaluated. The most promising route involves one or more enzyme incorporating the reaction catalyzed by acetate kinase for ADP phosphorylation.
Mass transfer and internal circulation in forming drops
Authors: Burkhart Lawrence , Weathers P. W. , Sharer P. C. 
Published: June 2004

AbstractThe presence of internal circulation in forming liquid drops has a significant effect on mass transfer rates. For the systems studied, no circulation was observed below a Reynolds number of 9.7. For Reynolds numbers between 9.7 and 34.4, transition from zero circulation to complete circulation during the entire drop formation period occurred. In studies on the rate of mass transfer from fixed volume drops with forced internal circulation, increases in mass transfer rates were found at Reynolds numbers which corresponded to those observed for the development of internal circulation patterns within the drop.
Periodic cycling of plate columns: Discrete residence time distribution
Authors: Furzer I. A. , Duffy G. J. 
Published: June 2004

AbstractThe discrete residence time distribution applies to systems under periodic control. A system consisting of a plate column has been modeled to allow the generation of the discrete residence time distribution. The parameters in the model have been evaluated by measurements of entrainment, holdup, and the step response of the column under direct computer control. A least‐squares minimization technique provided confirmation of the modeling procedures.
A comprehensive correlating equation for laminar, assisting, forced and free convection
Authors: Churchill Stuart W. 
Published: June 2004

AbstractA correlating equation for assisting convection was developed by combining correlating equations for pure free and pure forced convection. These component equations are based on laminar boundary‐layer theory for an isothermal, vertical plate. Theoretical values for assisting convection indicate that the third root of the sum of the third powers gives the best representation, as contrasted with the choice and rationalization of the second or fourth power by prior investigators.This expression was modified by the addition of a limiting value Nuo to obtain a better representation below the domain of boundary‐layer theory and was generalized for uniform heating and for spheres and horizontal cylinders by the appropriate choice of the characteristic length.
Mechanics of nonisothermal polymer melt spinning
Authors: Fisher Robert J. , Denn Morton M. 
Published: June 2004

AbstractSpin line tension, diameter attenuation, and the onset of the draw resonance instability are determined for a viscoelastic polymer melt, taking into account the changes in physical properties resulting from cooling of the filament. The theory predicts the experimentally observed stabilization of very short and very long filaments.
Stirred‐tank mechanical power requirement and gas holdup in aerated aqueous phases
Authors: Hassan Ibrahim T. M. , Robinson Campbell W. 
Published: June 2004

AbstractGas holdup and the ratio of the turbulent regime mechanical power consumed in aerated compared to that in nonaerated aqueous phases were measured in two laboratory sized tanks. Standard six‐blade turbine (D/T = 1/3), six‐blade paddle (D/T = 1/3), and four‐blade paddle (D/T = 2/3) impellers were used over a wide range of impeller rotational speed and gas sparging rate. For all systems, the power ratio results were found to fit a semitheoretical correlation (derived from dimensional analysis) involving the impeller Weber number, the aeration number, and the ratio of dispersion and liquid densities. Empirical correlations for gas holdup in water, aqueous solutions of nonelectrolytes, and an aqueous electrolyte solution are given. The overall results lead to the conclusion that power ratio and gas holdup correlations are highly specific to a particular impeller type and are also dependent on the tank size and the liquid phase physicochemical properties.
Thermodynamics of the sulfur dioxide‐seawater system
Authors: Abdulsattar Abdul H. , Sridhar Srinivasan , Bromley Leroy A. 
Published: June 2004

AbstractThe solubility of sulfur dioxide in seawater in the range 10° to 25°C and 10−5 to 1 molal is predicted based on a simplified chemical model. Estimates are also given of the resulting pH and the attendant distribution of sulfur and carbon dioxide species. Sulfur dioxide is considerably more soluble in seawater or other naturally alkaline waters than in pure water.
Drop sizes in annular gas‐liquid flows
Authors: Tatterson David F. , Dallman John C. , Hanratty Thomas J. 
Published: June 2004

AbstractThe droplets that appear in annular gas‐liquid flows are formed by the eruption of wavelets from the surface of the wall layer. Ninety per cent of the volume of this dispersed liquid is carried by only about 10% of the drops. We find, as suggested by Wicks and Dukler, that the distribution of drop sizes can be characterized by an upper limit, log normal function with only one of the three parameters, the volume median diameter, a strong function of flow conditions. A method for predicting the average diameter is suggested which is consistent with a theoretical interpretation based on a Kelvin‐Helmholtz mechanism, whereby the destabilizing force is the pressure variation over the wavelets.
Diffusional boundary‐layer resistance for membranes with low porosity
Authors: Malone Dermot M. , Anderson John L. 
Published: June 2004

AbstractDiffusional mass transfer across membranes with uniform but low pore densities was studied experimentally as a function of stirring rate and pore area fraction. The results were analyzed in terms of a stagnant film boundary‐layer model specially formulated for a heterogeneous membrane containing discrete pores. The overall membrane diffusional resistance is linearly related to the inverse of the pore area fraction of the membranes for a constant stirring rate. An equivalent boundary‐layer thickness can be defined which is independent of membrane properties but a unique function of stirrer speed. These experimental boundary‐layer thicknesses are greater by a factor of 3 than those predicted by a published Sherwood number correlation determined for homogeneous surfaces, but the stirring rate dependence is in excellent agreement with this same correlation.
Model of transient aerosol particle deposition in fibrous media with dendritic pattern
Authors: Payatakes Alkiviades C. 
Published: June 2004

AbstractWhen a suspension of fine solid particles in a gaseous medium flows through a fibrous filter, particles deposit on the fibers forming chainlike agglomerates known as dendrites. This deposition pattern is responsible for the intrinsically transient behavior of the filter, leading to drastic increases of the filtration efficiency and of the pressure drop. Related phenomena are observed when aerosols flow through other types of porous media (for example, granular beds), or next to duct walls, around immersed objects, etc. A theoretical model of the particle dendrite growth was proposed recently by Payatakes and Tien. Here a revised and generalized version of that model is developed. The following major revisions are made: allowance is made for collisions with a particle in a given dendrite layer that lead to retension in the same layer, radial as well as angular contributions to deposition are considered, and the dendrite layer adjacent to the collector is allowed to contain more than one particle. These changes lead to a substantially more realistic theoretical model. Expressions for the transient behavior of a filter of differential thickness are obtained, based entirely on first principles. These, as it has been shown in a previous publication, can be used to predict the dynamic behavior of a macroscopic fibrous filter. The use and behavior of this model is demonstrated in the simple case of deposition by pure interception. The present treatment of deposition by pure interception is more rigorous than and supersedes that adopted in previous works.
Mass transfer at high Péclet numbers for creeping flow in a packed‐bed reactor
Authors: Fedkiw Peter , Newman John 
Published: June 2004

AbstractAn isotropic, homogeneous packed‐bed reactor is modeled as an array of sinusoidal periodically constricted tubes (PCT). The effective asymptotic bed‐Sherwood number has been calculated for mass transfer at large Péclet number with a constant wall concentration and creeping flow hydrodynamics. The bed friction factor has also been calculated. The results for these macroscopic bed quantities depend upon two ratios of the microscopic PCT period length, average radius, and sinusoidal amptitude.
Binary gas diffusion of methane‐nitrogen through porous solids
Authors: Chen Lillian Lung‐yu , Katz Donald L. , Tek M. Rasin 
Published: June 2004

AbstractDiffusion rates of nitrogen and methane have been measured across ten porous solids at 35°C and 1 atm by a steady state flow method. The porous plugs used were cylindrical in shape, with diffusion occurring in the direction of the axis. Diffusion data were taken with porous cores either dry or saturated with liquids. Water and n‐heptane were used as saturating liquids.The rather complex internal structure of porous solids were indirectly characterized through some auxiliary measurements. These included porosity, permeability, and electrical resistivity factor (yet another indirect measurement of tortuosity).The effective diffusion coefficients were correlated for the gas phase diffusion as a function of porosity. The ratio of effective diffusion coefficient to the open space diffusion coefficient (De/Do) was correlated for dry cores using the properties approximately characterizing the pore structure.
Photoassisted heterogeneous catalysis with optical fibers: I. Isolated single fiber
Authors: Marinangeli Richard E. , Ollis David F. 
Published: June 2004

AbstractRecently reported varieties of photoassisted heterogeneous catalysts are summarized. A cylindrical, light carrying, optical fiber coated with a catalyst layer is evaluated as a novel configuration for all such light assisted catalysis. Equations are obtained which describe the light intensity in the fiber and its surrounding catalyst layer. A dimensionless group of the form Φ = (4αcβcdL)/(df) [d = dc for dc < λ, d = 0(λ) for dc > λ] determines the relative influence of light loss by all absorption and scattering to light transported in the fiber length. An effectiveness factor ηI for heterogeneous photoassisted catalysis is determined for reactions which are first order in intensity and without mass transport limitations. Asymptotic forms of ηI are ηI = 1.0 (Φ ≪ 1.0) and ηI = Φ−1 (Φ ≫ 1.0).
Vertical distribution of dilute suspensions in turbulent pipe flow
Authors: Karabelas A. J. 
Published: June 2004

AbstractClosed‐form expressions are presented for predicting vertical concentration distribution of the dispersed phase in the turbulent core of pipe and channel flow. Experimental data obtained with spherical particles, of mean diameter d50 comparable to the Kolmogorov microscale, are in good agreement with model predictions. The average value of dimensionless lateral particle diffusivity, ζ = ε/Ru*, determined from these data is approximately 0.25, that is, fairly close to previously reported measurements with much coarser particles.
An alternate to the Dengler and Addoms convection concept of forced convection boiling heat transfer
Authors: Mesler Russell B. 
Published: June 2004

AbstractCurrent literature describes forced convecting, boiling heat transfer as primarily convective heat transfer. The original evidence for this concept, reported by Dengler and Addoms, was reexamined and found misinterpreted. Nucleate boiling data, instead, correlate with their data. Subsequent use of the concept in correlations and models now requires close scrutiny.
Influence of drag reducing additives on mixing and dispersing in agitated vessels
Authors: Quraishi A. Q. , Mashelkar R. A. , Ulbrecht J. J. 
Published: June 2004

AbstractThe influence of the addition of drag reducing polymers and fibers on two transport processes in mechanically agitated liquid systems is examined. The first one concerns the determination of mixing times, which were found to be insignificantly to moderately increased in the drag reducing systems. The second one concerns the determination of the critical RPM at which complete suspension of solid particles occurs. It was shown that this was unaffected in the drag reducing systems. The results of this work can be applied to fermentation processes, biological reactors with flocs, and metallurgical processes. The theoretical implications of this work are to be seen in the association of polymeric and fibrous drag reducing additives with different parts of the turbulent spectrum.
Crystal size distribution dynamics in a classified crystallizer: Part II. Simulated control of crystal size distribution
Authors: Beckman James R. , Randolph Alan D. 
Published: June 2004

AbstractControl of sustained limit‐cycle instability in crystal size distribution (CSD) was simulated for a class II (high yield) crystallizer equipped with a fines destruction system and product classifier. Control was simulated by proportional control of nuclei density using fines destruction rate as the manipulated variable. The control constant necessary to eliminate instability was theoretically predicted and agreed with the constant found via simulation. Poorer control of CSD (inability to completely eliminate limit cycles) was predicted using slurry density and slurry withdrawal rate as the measured and manipulated variables, respectively. Development of techniques for fine crystal population measurements to estimate nuclei density are necessary for implementation of the former control scheme. The suggested nuclei density control scheme is effective both in minimizing CSD transients and for elimination of instability.
Predicting the combustion rate of pulverized fuel from its initial size distribution
Authors: Leesley M. E. 
Published: June 2004

AbstractIt is assumed that for pulverized fuel, the weight fraction W with a size larger than x can be expressed as W = exp(−bxn). This paper describes the theoretical development and experimental evaluation using pulverized anthracite burning at 30 lb/hr of a method of predicting the combustion rate of a pulverized fuel from the constants b and n in the above equation.
Absorption of sulfur dioxide into aqueous sodium hydroxide and sodium sulfite solutions
Authors: Hikita Haruo , Asai Satoru , Tsuji Tadashi 
Published: June 2004

AbstractThe rates of absorption of pure sulfur dioxide into aqueous sodium bisulfite, sodium hydroxide, and sodium sulfite solutions with and without a surface active agent were measured at 25°C using a liquid jet column. For the sulfur dioxide‐sodium hydroxide system, the rate of absorption into the solution without surface active agent was higher than that into the solution with surface active agent, indicating the existence of the interfacial turbulence. The absorption rates obtained for the present system under the conditions of no interfacial turbulence were in good agreement with the theoretical predictions based on the penetration theory.