bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bubble coalescence in fluidized beds
Authors: Lin S. P. 
Published: June 2004

AbstractThe two‐dimensional motion of two circular bubbles moving in train up through a fluidized bed is considered. By using continuum equations of motion for this two‐phase flow situation, neutral coalescence curves are obtained which indicate, for given bubble radii and distance apart, whether or not the bubbles will coalesce. The conclusions are in agreement with the available experimental results.
Entrance region flow of the Bingham fluid in a circular pipe
Authors: Chen S. S. , Fan L. T. , Hwang C. L. 
Published: June 2004

AbstractThe laminar, isothermal entrance region flow of the Bingham fluid in a circular pipe is studied at first by using the momentum integral method and the boundary‐layer equation for the Bingham fluid. In addition to the velocity boundary layer, the existence of the shear stress boundary layer is considered. The solution is valid only near the entry because of limitation of the boundary‐layer model. The Campbell‐Slattery method originally devised for the Newtonian fluid is also used to analyze the Bingham entrance region flow. The results are compared with those obtained through the use of the momentum integral method and those obtained through the use of the variational method by other investigators. While the results obtained in this work appear to be generally reasonable and valid, the results by the other investigators have been found to be somewhat erroneous.
Viscosity of nonpolar gaseous mixtures at normal pressures
Authors: Yoonm Poong , Thodos George 
Published: June 2004

AbstractThe relationship between μ*ξ and TR for nonpolar gases at normal pressures is used to predict the viscosity for their mixtures. For such mixtures, pseudocritical temperatures are used to obtain TR. To establish ξm for a mixture, a binary interaction model has been applied that utilizes composition and the ξ values of the pure components.Viscosities have been calculated for twenty binary systems which include helium and hydrogen. These calculated values produce an average deviation of 1.97% for 148 compositions. This method was also applied to the helium‐neon‐argon ternary system at 100°C. to obtain for four mixtures examined an average deviation of 2.2%.
Kinetics of the Hopcalite‐catalyzed oxidation of carbon monoxide
Authors: Brittan Michael I. , Bliss Harding , Walker Charles A. 
Published: June 2004

AbstractThe oxidation of carbon monoxide with Hopcalite catalyst was studied in an isothermal recycling reactor with special attention paid to the changes of gas phase compositions with time.Conversion‐time data exhibit significant departures from first‐order behavior often ascribed to this reaction. In early stages the reaction rate declines more rapidly than would a first‐order reaction; later the reverse is true. A mechanism, based on careful analyses of the literature and of our observations, is proposed. A kinetic model based on this mechanism is shown to reproduce the data of any run satisfactorily, but there is a considerable variation in values of the constants from run to run.
Separation of gaseous mixtures by permeation through polyethylene film
Authors: Reilly J. W. , Henley E. J. , Staffin H. K. 
Published: June 2004

AbstractThe permeation of polyethylene film by carbon dioxide, ethane, and propane at elevated pressures was investigated. In addition, the separation of mixtues of ethane and propane by permeation was studied.Both hydrocarbon vapors' permeation exhibited pressure dependence, with propane showing the greatest variation over the same range.In the case of the mixture separation study, the achieved degree of separation was lower than would be predicted on the basis of the pure component permeation constants. Moreover, the total flow of vapor through the film was greater than would be expected on the basis of the individual gas flows. This was attributed to an anomalous diffusion phenomenon of ethane in the presence of dissolved propane due to a plasticization of the polymer network.
Transient creeping flow around spheres
Authors: Sy Francisco , Taunton J. W. , Lightfoot E. N. 
Published: June 2004

AbstractAn explicit description is given for the gravitationally induced motion of an initially stationary gas bubble under creeping flow conditions. Analysis has shown that such a solution is good for all values of the Weber number as long as the quadratic terms in velocity are negligible in the Navier‐Stokes equation. It was also determined that the description of transient flow around a sphere from potential flow theory agrees with the short‐time limit of the creeping flow equations as applied to a gas bubble and solid sphere.The necessary steps to obtain a solution for the more general case of a spherical drop with appreciable density and viscosity is presented. Also, numerical comparison of the motion of a gas bubble and a weightless solid sphere shows that the times required to reach a given fraction of terminal velocity are nearly the same.
A model for the thixotropy of suspensions
Authors: Fredrickson A. G. 
Published: June 2004

AbstractA model for the rheological behavior of thixotropic systems is presented. The model is intended for systems exhibiting no elastic or anisotropic effects. It is shown how the constants of the model can be determined by a systematic program of experimentation. It is also shown how the model can be tested and amended, if necessary, by the same program of experiments. The model is advanced for suspensions of rigid, solid particles in liquids; it is not expected to be valid for materials of polymeric constitution or for suspensions of elastic, deformable particles in liquids.
Statistical models for surface renewal in heat and mass transfer. Part IV: Wall to fluidized bed heat transfer coefficients
Authors: Koppel L. B. , Patel R. D. , Holmes J. T. 
Published: June 2004

AbstractHeat transfer coefficients were measured for glass particles at the same wall surface of a fluidized bed for which glass particle residence times were measured in a previous study. The data compared well with theoretical predictions of the dependence of heat transfer coefficients on particle residence times. Heat transfer coefficients for metal particle systems, for which direct measurements of residence times were not available, were predicted with fair accuracy by estimating residence times from a dimensionless correlation proposed in a previous study. The ability of the particle surface renewal models to accurately predict heat transfer coefficients is strong evidence of their physical validity.
An eddy cell model of mass transfer into the surface of a turbulent liquid
Authors: Lamont John C. , Scott D. S. 
Published: June 2004

AbstractExperimental gas absorption studies for bubbles transported in turbulent pipe flow of water strongly indicate that liquid phase controlled mass transfer is due to surface renewal by turbulent eddies. Predictions of transport behavior from the conditions of turbulent flow cannot be made in support of this mechanism because no satisfactory theory of turbulent transport near a gas‐liquid interface is available. This work considers a model of the hydrodynamic behavior near the surface which provides a link between the observed mass transfer behavior and the state of the turbulent field.In this model, the very small scales of turbulent motion are considered to be controlling. These motions are idealized, and their flow and mass transfer behavior are solved analytically. The overall result for eddies of various sizes is related to the turbulent energy spectrum by using only the easily accessible parameter ϵ, the energy dissipation rate. This model gives quantitative agreement to within a factor of 2 for three widely different experimental situations including gas‐liquid and liquid‐solid interfaces. However, the predicted Reynolds number dependence is somewhat higher than the experimental result.The model attempts to clearly define the basic physical process at the interface. Therefore, it indicates the direction for further experimentation needed to clarify the basic relationship between the mass transfer rates in the liquid phase and the hydrodynamic behavior of the turbulent liquid.
Heat transfer to cylinders in a confined jet at high temperature
Authors: Chevalier P. H. , Kubanek G. R. , Gauvin W. H. 
Published: June 2004

AbstractTemperature and velocity measurements were carried out at the center of the test section of an 8‐in. I.D. cylindrical graphite chamber in a confined nitrogen jet issuing from a 40‐kw. D.C. plasma torch. The test section was located 10.5 in. below the torch nozzle, and temperatures and velocities up to 4,300°F. and 120 ft./sec. were obtained.The overall rates of heat transfer by forced convection were measured to water cooled circular and square cylinders in two orientations. Results indicated that, owing to the high level of turbulence of the jet, turbulent boundary layers prevailed in the low range of Reynolds numbers investigated. Correlations are presented in terms of the Nusselt, Reynolds, and Prandtl numbers, with the physical properties of the gas evaluated at the bulk temperature.
Sucrose inversion by partially deactivated ion exchange resin beds
Authors: McGovern Terence J. , Dranoff Joshua S. 
Published: June 2004

AbstractThe inversion of sucrose by partially deactivated ion exchange resin catalysts has been studied in a fixed bed reactor under conditions where intraparticle diffusion of sucrose is slow. Results show that the reaction remains apparently first order for deactivated catalyst. Activity is directly related to hydrogen content of the resin and is also dependent on the nature of the ion used to poison the catalyst.
Motion of liquid drops in non‐Newtonian systems
Authors: Marrucci Giuseppe , Apuzzo Gennaro , Astarita Gianni 
Published: June 2004

AbstractPredictive equations for terminal velocities of liquid drops in Newtonian and non‐Newtonian systems are reviewed. The wave theory analogy is extended to include liquid‐liquid systems. Experimental data obtained with seven different systems are presented. The agreement with predictive equations is satisfactory. Interface rigidity was observed in all the systems investigated.
The calculation of the critical locus curve of a binary hydrocarbon system
Authors: Hissong Douglas W. , Kay Webster B. 
Published: June 2004

AbstractA method of calculating the critical properties of binary hydrocarbon systems is presented which is based upon the rigorous thermodynamic equations for the critical point of a binary mixture. By using these equations together with an equation of state, a completely analytical procedure was developed with the aid of a digital computer. The Redlich‐Kwong and the Dieterici equations of state were chosen for study. The Redlich‐Kwong equation was found superior for predicting critical pressures and temperatures by this method, although the Dieterici equation was better for critical volumes. The two interaction parameters arising from the equation of state were calculated from combining rules or from available experimental critical data on binary systems. To facilitate the latter approach, a mathematical optimization routine was used to find the best values of the interaction parameters for twenty‐one binary hydrocarbon systems for which critical data were experimentally determined. The optimum values of the interaction parameters were correlated as functions of the ratio of molecular weights of the components. These correlations enable one to predict quite precisely the critical properties of the binary systems from the pure component data alone.
Experimental and computational studies of the dynamics of a fixed bed chemical reactor
Authors: Sinai José , Foss A. S. 
Published: June 2004

AbstractExperimental measurements of the temperature response of a fixed bed reactor to sinusoidal disturbances in the feed concentration, temperature, and flow rate show that a simple one‐dimensional mathematical model with distributed thermal capacitance satisfactorily describes the dynamic behavior of the reactor for modest excursions about an operating point. The reaction considered is a liquid‐phase exothermic reaction whose rate depends on the concentration of two reactants and the temperature.A computational analysis reveals that the amplitude and phase of the traveling concentration and temperature waves are influenced in a complex manner by the interaction between the two waves. The interaction, which is treated here as interference between traveling waves, is made complex by the difference in the rates of propagation of the temperature and concentration waves and by the variation of their speeds throughout the bed.
Some mathematical characteristics of menisci and their use in determination of surface tension
Authors: Biery J. C. 
Published: June 2004

AbstractBy expressing the meniscus height and the sine of the angle between the horizontal and a tangent to the meniscus curve as simple exponential functions of radial position, a new calculational procedure for determining surface tensions from menisci has been developed. These simple functions, when combined with the Laplace‐Young equation, generated three useful equations for calculating surface tensions as a function of radial positions. The overall procedure by using the three equations and five smoothing methods was tested on both experimental and calculated menisci. The results from the procedure for the calculated menisci agreed within 1.5% with the original surface tensions used to generate the meniscus. The agreement of values generated with the method and the comparison method previously reported for experimental menisci was within ±8% in general and within ±2% for the best formed menisci.
Spray quenching
Authors: Laskowski Jan J. , Ranz William E. 
Published: June 2004

AbstractA study was made of spray quenching by high velocity gas atomization. A mathematical model of both high and low temperature spray quenching was developed. Data were taken for proving and validity of the model.Experiments were performed on a vertical downward flow of air‐water in a 1.0 in. diameter tube. Injection was by either of two modes. The first was a set of six peripheral liquid jets projecting water perpendicularly into the high velocity airstream. The second mode of liquid injection was by means of a 360° peripheral, annular slot, which laid down a continuous wall film at the point of injection. Air velocities of 430 and 200 ft./sec. and liquid injection rates of from 150 to 1,200 ml./min. were studied. The following physical quantities were measured: liquid fluxes, wall film flow rates, drop size distributions, and median drop size. An attempt was made to measure gas temperature in a dense spray by using two different types of temperature probes, but only liquid temperatures could be detected. A comparison of data with published data and correlations was made.The best quenching conditions obtained were a liquid‐to‐gas mass ratio of 0.25, a Sauter mean drop diameter of 45 μ, and an indicated characteristic quench time of 10−3 sec.
Recoverable shear measurements in a parallel plate rheometerz
Authors: Fruh S. M. , Rodriguez Ferdinand 
Published: June 2004

AbstractA parallel plate rheometer has been devised which permits measurements of shear stresses of 102 to 105 dynes/sq.cm. and shear rates of 10−5 to 1 sec.−1. A linear, air lubricated bearing is used to align the apparatus, and a linear variable differential transformer is used to sense changes in position. With a sample of polyisobutylene and with several samples of poly(dimethyl siloxane), it has been established that a Hookean range exists for each sample at low stresses. Hooke's law in shear states that the modulus is independent of stress, where the modulus is defined as the ratio of the shear stress in steady, creeping flow to the strain which can be recovered after the stress is removed. Other conclusions supported by the present work are that the Hookean range does not extend to stresses which are high enough to cause non‐Newtonian flow, that the modulus decreases with increasing molecular weight although not in direct proportion, and that a sample with a broad molecular weight distribution has a lower modulus than one with a narrow distribution.
Concentration fluctuations and chemical conversion associated with mixing in some turbulent flows
Authors: Torrest Robert S. , Ranz William E. 
Published: June 2004

AbstractMicroconductivity probes were used for the measurement of point values of mean concentrations and root‐mean‐square concentration fluctuations for mixing of salt solutions in turbulent shear flows. Mixing studies covered a range of flow conditions, with Reynolds numbers on the order of 104, and included ducted turbulent jets, dispersion in turbulent pipe flow, a plane mixing zone, and several multiple injection systems. The test sections all had characteristic dimensions of about 2 cm. The results for mixing experiments are compared with available previous work. Lack of resolution for root‐mean‐square concentration fluctuations in some previous work is indicated.Reaction product concentrations for a rapid, second‐order, irreversible reaction in multiple injection systems, the plane jet, and the mixing zone were also obtained. The relation between conversion in reaction experiments and fluctuation level and decay in the equivalent mixing experiments is illustrated.
A modified Redlich‐Kwong equation for supercritical helium and hydrogen
Authors: Vogl Walter F. , Hall Kenneth R. 
Published: June 2004

AbstractA modified Redlich‐Kwong equation of state is developed in which the two parameters are expressed as functions of temperature. The critical values for the two constants in the equation are completely determined by the values of the critical properties of the gas. The optimum values of the constants for each isotherm (Z vs. P) are found, followed by a curve‐fitting routine that obtains the constants as functions of temperature. The resulting equation of state predicts experimental helium compressibility data to within an average of 0.90% absolute error for data in the range 0 < pressure ⩽ 700 atm., 5.26°K. ⩽ temperature ⩽ 1,500°K. For hydrogen, the prediction is to within an average of 0.79% absolute error for temperatures from 34° to 600°K. and pressures up to 2,900 atm.
A modified Redlich‐Kwong equation of state
Authors: Gray Ralph D. , Rent Nancy H. , Zudkevitch David 
Published: June 2004

AbstractA new modification of the Redlich‐Kwong equation of state is presented. The modification follows the procedure suggested by Redlich, Ackerman, et al., in which a deviation function (a function of temperature, pressure, and acentric factor) is added to the compressibility factor from the original equation to improve the agreement with data. The purpose of the present modification was to improve predictions of the Redlich‐Kwong equation in the saturated vapor region up to the critical point while retaining a relatively simple form to make analytical relations for derived properties possible. The equation for pressure correction to vapor enthalpy, derived from the compressibility factor by standard thermodynamic procedures, is also presented. Comparisons of predicted vapor compressibility factors and vapor enthalpy pressure corrections with literature data are given, demonstrating the advantages of the proposed modification when the saturated vapor region is of principal interest.
Drop‐size distributions produced by turbulen pipe flow of immiscible liquids
Authors: Collins S. B. , Knudsen J. G. 
Published: June 2004

AbstractDrop‐size distributions in turbulently flowing dispersion of immiscible liquids were investigated. The observed drop‐size distributions were actually a composite of two superimposed distributions. One is the distribution produced by the injection nozzle and the other is that produced by breakup in the turbulent flow field. A mathematical model was developed which predicted both the shape of the observed distributions and kinetics of the droplet breakup process for the distribution produced by the turbulent flow field.The flowing dispersion composed of water and insoluble organic phase was photographed at 27, 209, 421, and 576 pipe diameters below the mixing jet and at distances of 0.05, 0.1, and 0.4 diam. from the wall. Average flow rates varied from 14 to 20 ft./sec. in the 0.750‐in. I.D. tube. Three organic phases were studied at concentrations ranging from 0.6 to 10% by volume. Dispersed phase viscosity and interfacial tension varied from 1 to 18 cp. and 13 to 40 dynes/cm.No distribution law with any theoretical basis could be found which correlated experimental distributions.The stochastic model describing the breakup process postulates that each breakup event leads to two daughter drops with uniformly distributed volume ratios and a very small satellite droplet. An empirical correlation exists to predict only one of the three parameters of the model.
Iterative methods for solving problems in multicomponent distillation at the steady state
Authors: Billingsley D. S. , Boynton G. W. 
Published: June 2004

AbstractThe multicomponent distillation problem is formulated so that unknown compositions do not appear explicitly either in the equilibrium and material balance equations or in the heat balance equations. Use of this formulation in absolute iteration as well as Newton‐Raphson iteration is discussed. Other types of staged separation processes may be similarly expressed.
Convective diffusion of heat in composite media with heat sources and sinks
Authors: Baker B. S. , Gidaspow Dimitri , Wasan D. T. 
Published: June 2004

AbstractConvective diffusion of heat is a problem which arises in many areas. Since most thermal transport situations involve more than one material insulation, supports, etc., the treatment of composite regions is of interest. In certain systems, namely, those involving chemical or nuclear reactions, heat generation may be either localized or distributed. In this paper a general analytical treatment of this problem is made by using a double Fourier series technique involving an extended orthogonality concept. This treatment is then applied to the solutions of heat transfer situations arising in electrochemical energy conversion systems. Experimental temperature profiles are presented which test the theory.
Kinetics of ozone decomposition and reaction with organics in water
Authors: Hewes C. G. , Davison R. R. 
Published: June 2004

AbstractThe decomposition of ozone in water is found to be second order at pH 2 and 4 with the rate insensitive to pH. At pH 6 the reaction order is 3/2 to 2 and at pH 8 it is first order. Above pH 6 the rate increases rapidly with pH. Ozonation can greatly reduce the organic matter in waste water. The reaction rate of ozone with organics in flocculated secondary sewage effluent is found to depend on the rate of ozone decomposition, which is independent of the subsequent reaction with the organics.
Peak‐time method for measuring thermal diffusivity of small solid specimens
Authors: Harmathy T. Z. 
Published: June 2004

AbstractA simple test method is developed for determining the thermal diffusivity of solids and granular materials by measuring the time at which the peak on a temperature‐time record occurs. It allows the use of small easily prepared specimens and specimens of irregular shape (for example, stones). The tests can be performed at room temperature as well as at high temperatures, and can be repeated in short time intervals.