bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hot‐film anemometry measurements of turbulence in pipe flow: Organic solvents
Authors: Patterson Gary K. , Zakin Jacques L. 
Published: June 2004

AbstractLongitudinal turbulence intensities, autocorrelations, and energy spectra have been measured in the flow of toluene, benzene, and cyclohexane in smooth, round 1‐ and 2‐in. I.D. tubes. These measurements were made with a constant‐temperature hot‐film anemometer and covered radial positions from the center to r/a = 0.85 in the 2‐in. tube and to r/a = 0.75 in the 1‐in. tube.The turbulence intensity data were found to be similar to those obtained for air in a 10‐in. pipe by Laufer. A slight diameter effect was observed, the intensities in the 1‐in. tube being slightly lower than those in the 2‐in. tube at equal Reynolds numbers.The energy spectra were similar to the spectrum reported by Lee and Brodkey for water. The spectra reached higher frequencies at the lowest measurable energy levels for higher velocities. There was little effect of tube diameter or radial position on the spectra from the center to r/a = 0.85. A short inertial subrange with a log‐log slope of −5/3 seemed evident in high velocity spectra, and the log‐log slope of −7 was approached at high frequencies by the lowest velocity spectrum.The peak energy dissipation frequencies for all the energy spectra measured were approximately proportional to bulk mean velocity to the 1.4 power with little effect of tube diameter or radial position from the center to r/a = 0.85.Integral scales of the turbulence were proportional to bulk mean velocity to a power less than one for a given tube. These measurements indicated that the ratio of integral scale to pipe diameter is not a function of Reynolds number only.Microscale values were relatively independent of velocity and pipe diameter.
Dynamics of a tubular reactor with recycle: Part II. Nature of the transient state
Authors: Reilly M. J. , Schmitz R. A. 
Published: June 2004

AbstractA theoretical study of the transient state of a plug‐flow tubular reactor with recycle is presenred for a model in which axial dispersion of heat and mass is negligible. A qualitative description of the temporal behavior near the steady state is obtained from an analysis of the linearized transient equations, and some large‐scale transient characteristics are studied by means of numerical solution of the nonlinear transient equations. A cursory study of the application of the Liapunov's direct method to predict regions of asymptotic stability is also presented. Numerical examples illustrate sustained oscillatory behavior as well as the transient nature of systems with multiple steady states.
Transition and film boiling from horizontal strips
Authors: Kesselring R. C. , Rosche P. H. , Bankoff S. G. 
Published: June 2004

AbstractMeasurements of heat flux and surface temperature fluctuations are reported for transition and film boiling of Freon 113 from flattened horizontal stainless steel tubes. The strip width is found to have a definite effect upon the heat flux in the film boiling regime. Photographic measurements indicate the absence of any appreciable long‐range periodicities, from which it is inferred that random turbulent effects are quite important. Also, a spectrum of bubble diameter, frequencies, and spacings is observed. On the other hand, some short‐time spatial periodicities were observed, and the theoretical values of the parameters fell well within the experimental range. Based upon the photographic and heat transfer measurements, a recommended expression for the minimum heat flux was developed.
Forced convection mass transfer: Part IV. Increased mass transfer in an aqueous medium caused by detached cylindrical turbulence promoters in a rectangular channel
Authors: Watson J. S. , Thomas David G. 
Published: June 2004

AbstractEnhanced rates of mass transfer in aqueous systems were studied with an electrochemical technique. Detached turbulence promoters (cylinders supported away from the surface) were shown to cause increases in mass transfer in aqueous systems in a manner similar to that observed in gaseous system. As in air studies, peaks in the local rate of mass transfer were observed directly beneath the cylinders and a wake effect was observed downstream from the cylinders.
A method of finding simultaneously the values of the heat transfer coefficient, the dispersion coefficient, and the thermal conductivity of the packing in a packed bed of spheres: Part I. Mathematical analysis
Authors: Turner G. A. 
Published: June 2004

AbstractThe response of a packed bed to a sine wave of temperature in a stream of fluid through it will depend upon the amount of dispersion in the resistance to transfer between fluid and solid, and the thermal properties of the soild. A method is presented that allows the effects of these three phenomena on the amplitude and phase angle to be unravelled and hence all their magnitudes to be computed simultaneously. It thus presents a way of determining these three quantities in situations where they were previously obtainable either with great uncertainty or not at all. The method requires measurements of the relative amplitudes and phase angles at three frequencies, and (preferably) at ω → 0 as well, all to be carried out with high accuracy.
Limiting relation for the eddy diffusivity close to a wall
Authors: Son Jaime S. , Hanratty Thomas J. 
Published: June 2004

AbstractExperiments on mass transfer for fully developed flow in a pipe show that the eddy diffusivity for mass close to the wall is described by the functionality

The best interpretation of presently available data in a pipe and in an annulus is given by the following, more explicit relation

The evidence for this latter relation is not as conclusive as one would like. Accurate measurements of concentration profiles close to a wall are needed.
The phase and volumetric relations in the helium—n‐butane system: Part I. Phase and volumetric behavior of mixtures of low helium concentration
Authors: Jones Allan E. , Kay Webster B. 
Published: June 2004

AbstractThe P‐V‐T‐x phase relations of helium—n‐butane system were measured in the region of low helium content (up to 10.4 mole % helium). The system exhibits the gas‐gas equilibrium originally predicted by Kamerlingh‐Onnes and Keesom. The term gas‐gas equilibrium is applied because the critical temperatures of the mixtures are higher than the critical temperature of either component. This behavior is quite unlike that observed in most binary systems, in which the critical temperature of the mixtures lie between those of the pure compounds. As a consequence of the shape of the critical locus curve, the system exhibits isothermal retrograde condensation of the second kind.
On a conjecture of Aris: Proof and remarks
Authors: Luss Dan , Amundson Neal R. 
Published: June 2004

AbstractIn this paper a conjecture of Aris is proved to be correct, that of all catalyst particles of fixed volume for isothermal first‐order chemical reactions the spherical particle has the lowest effectiveness factor. The method of proof uses a process of symmetrization. Some conjectures are also made about other chemical reactions. The method of proof is also valid for two‐dimensional domain (infinite cylinder).
Diffusion and chemical reaction in isobutylene hydration within cation exchange resin
Authors: Gupta Vijai P. , Douglas W. J. M. 
Published: June 2004

AbstractThe chemical reaction and diffusion rate parameters were determined for the hydration of liquid isobutylene to t‐butanol with a cation exchange resin catalyst. High reaction rates were found to result from a high diffusivity of isobutylene within the resin catalyst. Both the high value for diffusivity and its negative temperature coefficient are consistent with the transport mechanism within the resin, being that of surface diffusion of isobutylene in an adsorbed state.
Some new results on momentum and heat transfer in compressible turbulent free jets
Authors: Tomich John F. , Weger Eric 
Published: June 2004

AbstractThe results of an analytical and experimental study of compressible, axially symmetric, turbulent free jets exhausting into quiescent air are presented. A finite‐difference technique was used to obtain a general solution which has eliminated the need for the simplifying assumptions required in previous investigations. The jet Mach number and jet temperature ratio have been found to be the only two initial jet properties which are necessary to characterize the dimensionless velocity and temperature variations in this type of jet. Modifications of dynamic eddy transfer coefficients given in the literature are used in the solution An experimental program was carried out to obtain data on free jet velocity and temperature variation at high initial jet temperatures and high subsonic Mach numbers where there has been a lack of experimental data. The numerical solutions of the time‐averaged conservation equations have been shown to agree well with the experimental data of the present study and of previous investigations.
Part V. Quasilinearization and state‐constrained systems
Authors: Rothenberger B. F. 
Published: June 2004

AbstractThe quasilinearization algorithm is examined as a means of determining the optimal control of a nonlinear tubular reactor system with state constraints. It is shown that the use of penalty functions in an unconstrained algorithm can effectively solve the constrained problem. The method is quadratically convergent to the optimal control and seems more successful than methods which require gradients in the computation.
An experimental investigation of the flow of aqueous non‐Newtonian high polymer solutions past a sphere
Authors: Turian Raffi M. 
Published: June 2004

AbstractThe terminal velocities of spheres falling in aqueous solutions of hydroxyethyl cellulose and polyethylene oxide were determined with ruby and steel spheres. For each sphere the terminal velocity was obtained in seven cylinder sizes covering a range of sphere‐to‐cylinder diameter ratio from 0.0067 to 0.18. The data were used in an extrapolation to correct for the cylindrical wall effect. Several alternative extrapolation procedures for estimating the zero shear viscosity were attempted and the results were compared. An empirical correlation for the drag coefficient was developed in terms of the Ellis parameters of the fluids, and the Faxén wall correction for Newtonian flow. the correlation gives the drag coefficient within 4% for all cases in which the quantity ηvt/Dτ1/2 is less than 0.3.
Flow of viscoelastic fluids through porous media
Authors: Slattery John C. 
Published: June 2004

AbstractLocal volume averaging of the equations of continuity and of motion over a porous medium is discussed. For steady state flow such that inertial effects can be neglected, a resistance transformation is introduced which in part transforms the local average velocity vector into the local force per unit volume which the fluid exerts on the pore walls. It is suggested that for a randomly deposited, although perhaps layered, porous structure this resistance transformation is invertible, symmetric, and positive‐definite. Finally, for an isotropic porous structure (the proper values of the resistance transformation are all equal and are termed the resistance coefficient) and an incompressible fluid, the functional dependence of the resistance coefficient is discussed with the Buckingham‐Pi theorem used for an Ellis model fluid, a power model fluid, a Newtonian fluid, and a Noll simple fluid. Based on the discussion of the Noll simple fluid, a suggestion is made for the correlation and extrapolation of experimental data for a single viscoelastic fluid in a set of geometrically similar porous structures.
The calculation of heat transfer coefficient for combustion driven transverse oscillations in a gas‐air burner
Authors: Dent J. C. 
Published: June 2004

AbstractIn this paper a method is presented for the computation of the heat transfer coefficient in a gas‐air burner in the presence of combustion‐driven transverse mode oscillations. By considering the oscillations in pressure within the chamber to be small compared with the mean chamber pressure, and to be known, methods of acoustics may be used to determine the average energy density of the acoustic waves at the wall. Consideration of this acoustic energy to create greater mixing in the boundary layer enables the heat transfer problem to be considered by the Dankwerts‐Mickley model for turbulent heat exchange. With suitable definition of a friction velocity in terms of the friction velocity v* for fully developed turbulent pipe flow and the root mean square particle velocity of the acoustic wave (ar.m.s.ω), it is found that agreement exists between the computed ratio of heat transfer coefficients, with and without combustion‐driven oscillations and the experiments of Zartman, which appear to be the only experimental data for transverse oscillations in a gas‐air burner.
Prediction of pressure drop for two‐phase, two‐component concurrent flow in packed beds
Authors: Turpin Jim L. , Huntington R. L. 
Published: June 2004

AbstractTwo‐phase, gas‐liquid concurrent flow in packed beds was investigated with the use of an air‐water system and 2‐, 4‐, and 6‐in. diameter columns packed with tabular alumina particles of 0.025 and 0.027 ft. diameters. Total pressure drop, column operating pressure, and liquid saturation were measured as functions of gas flow rate, fluid temperatures, and flow direction at several constant liquid flow rates for each column.Correlation of the frictional pressure loss was achieved in terms of a defined two‐phase friction factor and a second correlating parameter which is a function of the liquid and gas Reynolds numbers. A viscosity correction factor was required to extend the friction factor correlation to include liquid viscosities widely divergent from that of water.The liquid saturation data for both upward and downward flow were correlated in terms of the ratio of mass flow rates of the respective phases.
A conjugate inequality for general means with applications to extremum problems
Authors: Eben Carl D. , Ferron John R. 
Published: June 2004

AbstractInequalities are derived for a general class of convex‐functional means which may contain negative weights. Specific cases include the arithmetic‐mean–geometric‐mean inequality and other power‐mean inequalities. These inequalities make possible the solution of a wider class of extremum problems than are susceptible to the classical means with positive weights. In particular, it is shown that the geometric programming algorithm may in some cases be extended to functions with negative coefficients. A weaker result is derived for application without restrictions on the signs of the coefficients or variables. This leads to a computational scheme which is useful in the solution of certain classes of nonlinear programming and inequality‐constrained multistage optimization problems.
An analytic solution for the dynamics of a packed adiabatic chemical reactor
Authors: Crider J. E. , Foss A. S. 
Published: June 2004

AbstractLocally linearized equations for dynamic disturbances from a steady state have been solved analytically for an adiabatic chemical reactor with chemically inert packing and a homogeneous chemical reaction. The solutions, in the form of transfer functions, include the effects of heat capacity of the packing and heat transfer between the packing and the fluid, as well as the coupling effects of chemical reaction and the associated heat generation.Several limiting cases of the transfer functions are discussed and the transfer functions are simplified by an approximation of the temperature dependence of the reaction rate. Frequency responses and step responses of the reactor are calculated from the transfer functions.
The correlation of vapor‐liquid equilibria of light hydrocarbons in paraffinic and in aromatic solvents at low temperatures and elevated pressures
Authors: Van Horn Lloyd D. , Kobayashi Riki 
Published: June 2004

AbstractA correlational procedure was developed to predict the vapor liquid equilibrium behavior of light hydrocarbons in heavier hydrocarbon solvents at low temperatures and elevated pressures. The method is applicable to paraffinic as well as aromatic solvents.The method employed the Benedict‐Webb‐Rubin equation of state to predict the vapor phase fugacities. Methane liquid fugacities in the various hydrocarbon solvents were based upon Henry's law which included terms to account for compositional and pressure effects. The liquid fugacities for ethane and propane were calculated using infinite dilution data to modify empirically the Scatchard‐Hildebrand equation. Excellent agreement between the correlated and low‐temperature data available on this class of systems was obtained.
Laminar dispersion in capillaries: Part V. Experiments on combined natural and forced convection in vertical tubes
Authors: Reejhsinghani N. S. , Barduhn Allen J. , Gill William N. 
Published: June 2004

AbstractAn approximate theory for transient dispersion with combined free and forced convection in vertical tubes is developed and tested experimentally. It is found that the dispersion coefficient in such systems depends on a parameter α, which is defined by Equation (38). The analytical expression developed for the dispersion coefficient, Equation (33), is found to be a reasonably good approximation in the range −50 < α < 300.Experimental results are reported for a rather wide range of parameters for tubes with both 1 1/2 and 5 mm. diameters.It is found that the extent of dispersion is enhanced significantly when lighter fluid is on the bottom and displaces a heavier one. On the other hand, the dispersion coefficient is inhibited when the situation is reversed. It is found that these effects are not symmetrical with respect to the absolute magnitude of the parameter α as is illustrated in Figure 12.
Turbulent flow in concentric annuli
Authors: Clump Curtis W. , Kwasnoski Daniel 
Published: June 2004

AbstractAn eddy diffusivity model was developed and used to predict velocity distributions for turbulent flow of air in annuli. Comparison of distributions calculated by the model with experimental data shows that good agreement between calculated and measured values can be attained for core‐to‐shell ratios from 0.001 to 0.990. The significant advantage of using a diffusivity model to predict velocity distributions lies in the inherent ability to consider systems with nonlinear stress distributions.
A study of the effect of sample size on the analysis of power mixtures
Authors: de Chazal L. E. Marc , Hung Yen‐Chi 
Published: June 2004

AbstractOne of the greatest difficulties in the analysis of mixing operations for powders is that of specifying the degree of mixedness in a quantitative manner. This problem is studied for on idealized model. A precise index of the degree of mixing is found for this model, which holds promise of being useful for real mixtures. It is shown that samples of a single size provide all the necessary information. The effect of sample size is defined quantitatively, and a minimum sample size is recommended.
Mass transfer between immiscible liquid metals
Authors: Pasternak Alan D. , Olander Donald R. 
Published: June 2004

AbstractThe extraction of lanthanum and barium from single falling drops of the uranium‐chromium eutectic into magnesium was studied at 1,000°C. Because of the short contact times involved, the data best fit the stagnant diffusion model for lanthanum. For barium, the fraction extracted was governed by external resistance of the magnesium phase. Drop velocities were adequately represented by the Hu‐Kintner correlation.
Stability of reaction on a spherical particle
Authors: Winegardner D. K. , Schmitz R. A. 
Published: June 2004

AbstractThis paper presents a theoretical study of the stability of chemical reaction on the external surface of a single spherical particle in stagnant surroundings. The analysis, which invokes methods of linear stability theory, yields necessary and sufficient conditions for stability of a steady state solution to small disturbances for the cases of very small and very large solid thermal conductivity. It is shown that heat losses from the solid surface may lead to transient behavior which is characteristically different from that for adiabatic surfaces, and that the unsteady state is strongly affected by the thermal capacity of the solid material. A numerical example is employed to illustrate the possible significance of unstable situations.
Comparison of kinetic and diffusional models for solid‐gas reactions
Authors: Ishida M. , Wen C. Y. 
Published: June 2004

AbstractA comparison of the kinetic and diffusional models for solid‐gas reactions occurring in a spherical particle is presented. The similarities and differences of the unreacted‐core shrinking model and the homogeneous model are examined in light of the rate‐controlling factors. In view of the similarity of the two models, it is shown that erroneous conclusions in regard to the mechanism and the activation energies may be drawn from an analysis of the experimental data. A more versatile model is presented in order to augment the two models so that wider varieties of solid‐gas reaction systems may be treated. The concept of effectiveness factors in solid‐gas reactions is introduced, and the influence of diffusion is ascertained.
Solids mixing in fluidized beds
Authors: Woollard I. N. M. , Potter O. E. 
Published: June 2004

AbstractThe movement of solids associated with the rise of a single gas bubble in an incipiently fluidized bed has been determined. The bulk volume, measured at the porosity of incipient fluidization, of tracer solid which is transported across the original interface between undyed glass spheres in the upper region and dyed glass spheres (tracer solid) in the lower region, is approximately 30% of the bubble volume. The measurements relate to bubble volumes from 14 to 200 ml. in a glass column, 4 in. diam. Solids used were glass spheres of diameter 380 μ. The profile created when a bubble rises through a layer of fluidized tracer solids into the fluidized solids above the tracer layer has been approximately determined. The distance by which the solids were displaced upward, due to the passage of the bubble, was found to be greater than would have been the case if the behavior were that of a sphere in an inviscid liquid.
Concentration‐dependent time‐lag measurements
Authors: Phillips J. R. , Dodge B. F. 
Published: June 2004

AbstractIn gas‐metal permeation, diffusion is normally considered to be the rate‐controlling step. In addition, the diffusivity is usually taken to be independent of concentration. Under these conditions, the time lag (a characteristic of the system which depends on the time required to achieve steady state flow) is found to be (and theoretically should be) independent of the gas pressure applied to the inlet surface of the metal membrane. Furthermore, the time lag can then be directly related to the diffusivity of the system.In this paper, data on the hydrogen type 321 stainless steel system are presented which show a pronounced effect of pressure on measured values of the time lag. Taken alone, these data can be explained either by a concentration‐dependent diffusivity or by resistance to flow at the metal surface. From steady state data it is shown that surface resistance is the better explanation. A model of the permeation process is presented which is consistent with the time lag data, and an estimate is made of the diffusivity of hydrogen in type 321 stainless steel.The variables studied were hydrogen pressure at the entrance surface of the membrane (0.1 to 30.0 atm.), temperature (300° to 800°C.), and membrane wall thickness (0.0252 to 0.2475 cm.).