bluuebunny/crossref_metadata_2025_split huggingface dataset:
Liquid bridges between cylinders, in a torus, and between spheres
Authors: Erle Michael A. , Dyson D. C. , Morrow Norman R. 
Published: June 2004

AbstractThe stability of a capillary liquid bridge of given volume between two small, solid, equal, separated spheres is investigated by formulating and treating a minimum energy problem in the calculus of variations and by experiment. A conjecture is made that in the case of two solutions one and only one is minimizing, and that the case of one solution represents the limiting stable bridge. This theory agrees accurately with our stability experiments. Furthermore, it is possible to predict the cohesive force. For the case of spheres in contact, the theory presented here is in agreement with some experimental work and also with the theory of Fisher and calculations of cohesive force based on Melrose and Wallick's solution to the bridge problem. For the case of separated spheres, the agreement with the only available experimental data is excellent except for close separations.
Bubble growth by coalescence in gas fluidized beds
Authors: Argyriou Dimitris T. , List Harvey L. , Shinnar Reuel 
Published: June 2004

AbstractBubble size and distribution of bubble sizes were studied in an air fluidized bed, 11.5 in. in diam. and 3 ft. high, by taking motion pictures of the bubbles breaking the top surface of the bed and by determining the size of the bubbles from the film. The distribution of bubble volumes at a given bed height was expressed as a gamma distribution with parameters obtained from the observations. A statistical mechanical method proposed by Hulburt and Katz for studies in agglomeration of particles was used in the mathematical formulation of the problem. A proposed mechanism of bubble growth by coalescence in gas fluidized beds resulted in a one parameter model. Comparisons of the distributions predicted by the model to the experimentally obtained profiles yielded the parameter of the model.
Interfacial mass and heat transfer during evaporation: I. An experimental technique and some results with a clean water surface
Authors: Navon Uri , Fenn John B. 
Published: June 2004

AbstractA vacuum sweeper probe of a type introduced by previous investigators was evaluated for use in the study of heat and mass transfer during evaporation. A simple theory of the probe behavior was formulated and checked by experimental measurements over a substantial range of operating conditions. The results revealed that in the interpretation of experimental data the validity of some assumptions usually made is strongly dependent upon seemingly minor features of probe construction and operation. Errors as large as 200% were encountered when the gas flow distribution in the probe was not symmetrical. Consequently, some results now in the literature are open to question.To test the technique and theory as well as to introduce a subsequent study of the effect of monolayers on evaporation, the evaporation rate from a clean water surface was measured over a temperature range of 2° to 22°C. The role of natural convection was clearly reflected in the increase of Nusselt number as the water bulk temperature passed through the density inversion at 4°C. A relation between Nusselt and Rayleigh numbers was determined and found to be consistent with earlier results of others.
Multicomponent separation calculations by linearization
Authors: Naphtali Leonard M. , Sandholm Donald P. 
Published: June 2004

AbstractA new approach to separation calculations has been developed which has many practical advantages. The equations of conservation of mass and energy and of equilibrium are grouped by stage and then linearized. The resulting set of equations has a block‐tridiagonal structure which permits solution by a simple technique. Thus a new way to apply the Newton‐Raphson technique to separation calculations is devised. The method has been tried on a number of problems chosen to exhibit characteristics which cause other solution technique to fail. Most problems are solved with ten iterations or less.
Transient creeping flow around fluid spheres
Authors: Sy Francisco , Lightfoot E. N. 
Published: June 2004

AbstractA description of transient behavior of a spherical liquid drop rising or falling in a quiescent continuous field has been obtained by numerical methods. It is found that for the same disperse phase to continuous phase density ratio, the transient behavior of a liquid drop is usually intermediate between that of a gas bubble and a solid sphere. However, at the region where V/V∞ of a solid sphere is approximately equal to that of a gas bubble, the liquid drop generally has a higher value of V/V∞ than either the gas bubble or the solid sphere.For short times, behavior of a liquid drop is shown to be in agreement with that obtained from potential flow theory.
Laminar dispersion in Jeffery‐Hamel flows: Part I. Diverging channels
Authors: Gill William N. , Güceri Ülkü 
Published: June 2004

AbstractDispersion in flow in diverging channels, where the velocity decreases with axial distance is studied. Numerical experiments indicate:

At sufficiently large values of the angle of divergence and Peclet number, both axial and transverse molecular diffusion play minor roles in the dispersion process, and the system is dominated by convection. This is in marked contrast to parallel wall systems.
A dispersion model, given by Equation (15), is shown to exist for such flows for limited ranges of the Peclet number and angle of divergence.
At sufficiently large values of dimensionless time, the dependence of concentration on both axial position and time can be represented by a single similarity coordinate. This behavior is predicted by both the numerical solutions of Equation (3) and analytical solutions of the dispersion model.
On the thermodynamics of nonuniform systems
Authors: Metiu H. , Ruckenstein E. 
Published: June 2004

AbstractTwo methods are presented for the treatment of the nonuniform systems. Both have as a starting point the approximation of the real system by a succession of uniform systems (cells). In one of them, the nonuniformity is taken into account by attributing a free energy to the separating surfaces between the cells, while in the other by considering that the cells are under the action of an “external field” created by the nonuniformity.A distinction between small and large nonuniform systems is made by comparing the thickness of the nonuniform system with the length of the interval in which the nonuniformity is decaying. For small systems the intensive properties depend on the thickness of the system and thus some supplementary effects, as for instance the disjoining pressure, occur.An expression for the “external field” based on the formalism of the radial distribution function is proposed.A large number of phenomena, such as surface tension, adsorption, disjoining pressure, nucleation, the vapor pressure of a liquid imbibing a porous medium, the influence of a solid surface upon a chemical reaction, are treated in a unitary manner by means of the present approaches.Some previous equations such as those of Cahn‐Hilliard and of Hill are derived in a different manner or justified.The objections raised by Widom against the continuous approaches are discussed.
A Lagrangian algorithm for equality constrained generalized polynomial optimization
Authors: Blau Gary E. , Wilde Douglass J. 
Published: June 2004

AbstractA procedure for optimizing generalized polynomial functions occurring widely in engineering design problems is presented. Equality constraints of the same form can be handled. The technique involves driving to zero the gradient of a Lagrangian function by a Newton‐Raphson method. A nonlinear transformation so simplifies the derivatives needed for Newton‐Raphson iteration that they are given in closed form. The initial estimate needed to start the algorithm need not be feasible. Successive systematic adjustment of Lagrange multipliers is accomplished, and an unambiguous procedure for starting multipliers is given. All implicit computations are linear. Convergence is not proven, but successful computational results for the design of a reactor exchanger pump system in eight variables and with five constraints are presented.
Catalytic reduction of nitric oxide with various hydrocarbons
Authors: Ault J. W. , Ayen R. J. 
Published: June 2004

AbstractConversion data for the reduction of nitric oxide with C1 to C8 hydrocarbons over a bariumpromoted copper chromite catalyst were obtained in an integral flow reactor operated at atmospheric pressure and temperatures of 225°C to 525°C. In general, an increase in carbon number in the hydrocarbon studied resulted in a decrease in the required temperature for a given nitric oxide conversion. For a given carbon number the required temperature for a given nitric oxide conversion decreased with degree of saturation. The data were fitted to empirical rate expressions.
Thermal conductivity of mixtures of argon‐helium, argon‐nitrogen, and argon‐neon
Authors: Peterson Jon N. , Hahn Thomas F. , Comings E. W. 
Published: June 2004

AbstractA secondary concentric cylinders cell was used to measure the thermal conductivity of binary mixtures of argon‐nitrogen, argon‐helium, and argon‐neon approximately 20, 40, 60, and 80 vol. % at 75°C, and pressures to 2,800 atm. Measurements were made also on the pure gases argon and nitrogen.
Van der Waals forces in a three‐phase system
Authors: Sherony D. F. , Kintner R. C. 
Published: June 2004

AbstractAn analysis is made of the Van der Waals forces of two different species when separated by a third continuous component. Results show that under certain circumstances, attractions as well as repulsions can exist between the two different species. The theory is applied to a fibrous bed coalescer to determine what type of material would best serve as a coalescence medium.
Transient flow in the hydrodynamic entrance regions of long closed ducts
Authors: Downing Carl G. 
Published: June 2004

AbstractVelocity profiles were calculated for transient fluid flow in the hydrodynamic entrance regions of a long narrow slit and of a long tube. The solutions were obtained by use of a linearized momentum equation. An estimate was also made of the manner in which the resistance to flow of the entrance region develops with time.
Multiparameter adaptive process control via constrained objective functions
Authors: Ryan Philip J. , Crandall Edward D. 
Published: June 2004

AbstractA method has been developed for applying classical minimization techniques to forms of algebraic performance indices for use in optimal adaptive control systems. Essentially, the derivative of a general objective function is constrained to be equal to the integrand of a desired integral performance index. This generates a set of linear algebraic equations, the solution of which results in an algebraic objective function which is explicit in the system parameters. Derivatives of this function can be taken with respect to the controllable parameters, set equal to zero, and solved for the settings which minimize the performance index over time. Alternatively, the function itself may be searched for its minimum on the controllable parameters.The method has been applied to a stirred tank chemical reactor with an exothermic first‐order reaction in which heat removal was accomplished by cooling coils. The cooling water flow rate was controlled by a proportional‐plus‐integral controller and by a three‐mode controller. The adaptive control system adjusted the controller settings periodically. The plant, which was third‐order, was controlled to a second‐order dynamic reference model. The responses to both initial offsets (start‐up problem) and disturbances in system parameters were investigated. In all cases, the adaptive control system performance was markedly superior to that for the unadapted, ordinary feedback control system.
Turbulent momentum transfer in two‐phase cylindrical Couette flow
Authors: Gandhi Ravi , Estrin Joseph 
Published: June 2004

AbstractTorque measurements were made in experiments carried out using a cylindrical Couette apparatus with the inner cylinder rotating and the outer one stationary. The fluid systems employed consisted of distilled water, 50% distilled‐water glycerine solutions, and these with several concentrations of suspended polystyrene spheres (through 40 on 70 mesh). The parameters employed by Bjorklund and Kays were found to correlate the data successfully when suspension viscosities were used for the two‐phase systems.
Fugacity and vapor pressure of nonpolar liquids at low temperatures
Authors: Chao K. C. , Greenkorn R. A. , Olabisi Olagoke , Hensel B. H. 
Published: June 2004

AbstractAvailable generalized correlations of fugacity coefficients of nonpolar liquids are reexamined in their lower temperature ranges, and these correlations are extended to a reduced temperature of 0.35. Generalized functions are constructed from literature data on vapor pressures and liquid densities. Two sets of functions are presented with w and zc, respectively, as third parameter. The results fulfill a need for basic information in the engineering of cryogenic systems.The same vapor pressure data are correlated in a generalized form down to Tr = 0.35 to give a one‐parameter family of reduced vapor pressures curves. The correlation is compared with data on simple fluids, normal fluids, polar substances, and quantum fluids.
Diffusion and reaction in ideal multicomponent systems: II. Behavior away from equilibrium
Authors: Solomon R. L. , Hudson J. L. 
Published: June 2004

AbstractAn analysis is made of diffusion and chemical reaction in an isothermal multicomponent fluid. Transient gas‐phase reaction in a one‐dimensional nonflow system and steady state gas‐phase or surface reaction in a tubular reactor are considered. The equations are linearized around some state away from equilibrium. Multicomponent and binary diffusivity expressions are used and a series of reactions of varying complexity is considered. The possibility of oscillations increases as the complexity of the reactions is increased. These oscillations occur with time in the nonflow system and with space‐time in the tubular reactor, and it appears that any reacting mixture which oscillates in one of these two systems will also oscillate in the other.
Sufficiency conditions for constrained extrema
Authors: Law Victor J. , Fariss Robert H. 
Published: June 2004

AbstractSufficiency conditions for equality constrained extrema are formulated in terms of a transformed set of coordinates by means of a generalized inverse of the constraint Jacobian matrix. This procedure produces a computationally simple and efficient method for testing sufficiency of a previously established stationary point. Computation of Lagrange multipliers is also facilitated by the method.
Rates of sorption and diffusion of hydrocarbons in zeolites
Authors: Riekert Lothar 
Published: June 2004

AbstractThe kinetic patterns of sorption, desorption, and sorbate exchange have been studied for several C2‐C5 hydrocarbons in synthetic zeolites of the mordenite, T and Y structures. The rate observations can best be represented by a model of sorption on interstitial sites in the solid, rather than by a model based on the analogy with macroporous sorbents. Two cases of interstitial diffusion have to be distinguished for this purpose. The number of vacant sites changes in time during the process of sorption, whereas it can remain constant if one sorbate is exchanged against another one. Rate measurements for both types of processes are reported and their interrelation is discussed.
Mass and energy transfer between a confined plasma jet and a gaseous coolant
Authors: Smith Dean L. , Kadlec Robert H. , Churchill Stuart W. 
Published: June 2004

AbstractMass and energy transfer between confined plasma and coolant gas streams was studied experimentally. Argon was used as the plasma gas and nitrogen was used as the coolant gas. The temperature profiles present in the mixing region were determined by optical‐spectrographic methods. Both the electronic excitation temperature of the argon atoms and the rotational temperatures of the nitrogen molecules were determined. The compositions and axial velocities present in the plasma coolant mixing region were determined by sampling probe methods.The measured nitrogen temperatures were found to be much lower than the argon temperatures present at the same point in the flow. The difference could be explained on the basis of incomplete mixing and thermal equilibration on the microscopic scale. The composition profiles indicated that direct induction of coolant into the high‐velocity plasma jet and the formation of a recirculation eddy increased the mixing of plasma and coolant.From the standpoint of carrying out a chemical reaction in the plasma jet, the results indicate that the mixing of a reactant injected into a plasma jet reaction chamber with the plasma would be very rapid but that the internal energy modes of the reactant molecule might not be fully excited during the short residence time in the high‐velocity flow.
Mathematical model of heavy water extraction and distillation
Authors: Burgess M. P. 
Published: June 2004

AbstractA mathematical model of the heavy water production facility at the Savannah River Plant, an installation of the U.S. Atomic Energy Commission at Aiken, South Carolina, operated by E. I. du Pont de Nemours and Company, was developed because measured production rates, even when averaged over one‐month periods, are inadequately precise for process control. With this model the instantaneous steady state production rate for any set of process conditions is calculated with precision. Therefore the model is used to establish process set points for achieving production goals, to study the effect of important process variables on these goals, and to evaluate proposed changes of equipment. In fact, with only minor changes in the computer program, several features of a newly designed heavy water plant are being evaluated.
Absorption and desorption accompanied by a reversible reaction
Authors: Porter K. E. , Cantwell A. D. C. , McDermott C. 
Published: June 2004

AbstractThe processes of absorption and desorption with reversible reaction are compared theoretically for reactions of the type A ⇌ nB. With the same concentration difference between bulk and interface, it is found that in general, the rate of desorption is lower than that of absorption. Under certain conditions the difference may be as much as 35%.The analysis is based on the penetration theory. The numerical solution introduces a new transformation of the time and distance variables (based on the error function) which reduces the computing time required. An analytical examination of the penetration theory equations provides an explanation of the results of the numerical solution.
Correlation of second virial coefficients through potential function parameters
Authors: Kunz Robert G. , Kapner Robert S. 
Published: June 2004

AbstractAn analytical technique based on the method of least squares has been developed to fit experimental second virial coefficients to the functional form derived from the Lennard‐Jones (6–12) potential. Both the functional form and the normal equations of the least squares fit are rigorously derived. Because of the implicit, nonlinear dependence upon one of the adjustable parameters, a computer solution of the normal equations is required. Second virial coefficient data for a large number (60) of materials, including hydrocarbons, halides, alcohols, and cyclic compounds, have been extracted from published sources, carefully evaluated for consistency, and fitted to the Lennard‐Jones potential function.Force constants for these materials as determined from fitting the data in this uniform manner have been found to be related to structural parameters. The final correlation, with the potential well‐depth related to critical temperature and the collision diameter calculated from a set of group contributions with appropriate corrections for polarity and/or association, produces average deviations between computed and experimental second virial coefficients of 10 to 15% or 100 cc./g.‐mole, whichever is greater. In many cases the agreement is much better.
Induced transport in pulsating flow
Authors: Horn F. J. M. , Kipp R. L. 
Published: June 2004

AbstractThe dispersion coefficient is evaluated in a general linear chromatographic system in which the velocity field is time periodic. Computations are carried out in detail for two examples. In the first example there are two phases and the flow pattern is simple. In the second example there is only one phase and the flow pattern is complex. The latter example is closely related to Taylor diffusion. Depending on the relative size of certain dimensionless parameters, one can distinguish four regions of different qualitative behavior of the system: molecular diffusion region, Taylor region, constant amplification region, and boundary transport region.
Synthesis of system designs: III. Toward a process concept generator
Authors: Siirola J. J. , Powers G. J. , Rudd D. F. 
Published: June 2004

AbstractPrinciples are developed for the computer‐aided generation of initial process flowsheets. The invention of a process concept is analogous to the proof of a multihypothesis/multiconclusion theorem, a mental activity which has been simulated on the computer. Techniques of artificial intelligence are combined with the concept of equivalence class matching and information flow logic to develop a working, computerized process synthesizer. This is part of a continuing project on the development of principles of process invention.
Confined jet mixing in the entrance of a tubular reactor
Authors: Seider Warren D. , Churchill Stuart W. 
Published: June 2004

AbstractThe equations for the conservation of momentum and mass were solved numerically for the region downstream from the exit of an axial jet into a confined annular stream of the same fluid. An implicit, alternating direction method was used. Numerical results were obtained for radius ratios of 0.281, 0.470, and 0.563 over a range of jet‐to‐annular velocities from 0.85 to 2.77. The values for the limiting case of the entrance region in pipe flow are in good agreement with the values of Christiansen and Lemmon and Ventras, Duda, and Bargeron. Solution of the equations for the conservation of chemical components produced results for component transfer in agreement with the experimental compositions obtained by Wood for jet mixing. Representative calculations were carried out for a chemical reaction. The results indicate the efficiency of the mixing process for this type of reactor.Experiments were carried out with water and dye to define the conditions under which the assumption of steady, laminar jet mixing is valid. The experiments also indicated the conditions and location of turbulent breakup of the jet.