bluuebunny/crossref_metadata_2025_split huggingface dataset:
Falling cylinder viscometer for non‐Newtonian fluids
Authors: Ashare Edward , Bird R. Byron , Lescarboura Jaime A. 
Published: June 2004

AbstractIt is shown how previous analyses of the falling cylinder viscometer for Newtonian fluids can be extended to non‐Newtonian fluids. Specific relations are given for the velocity of descent for several simple non‐Newtonian viscosity functions. A differentiation procedure is presented whereby the non‐Newtonian viscosity for a fluid can be deduced from velocity of fall measurements. In the course of the development, some useful approximate expressions for axial non‐Newtonian flow in annuli are developed. Finally, a comparison of the Ellis and power law models is made by an analysis of the axial annular flow data of Frederickson and of McEachern.
Confined wakes: A numerical solution of the Navier‐Stokes equations
Authors: Paris Jean , Whitaker Stephen 
Published: June 2004

AbstractA numerical solution of the two‐dimensional Navier‐Stokes equations is presented for the confined wake formed by the merging of two‐plane Poiseuille flow streams. The system of finite‐difference equations for the stream function and vorticity is solved by the Peaceman‐Rachford elimination method for Reynolds numbers of 1, 50, 387, and 647. While the stability of the numerical method is not a problem for this range of Reynolds numbers, the number of points in the finite‐difference network (and hence the computation time) does become burdensome.At high Reynolds numbers, the primary boundary‐layer simplification is imposed to yield a set of parabolic equations for the vorticity and stream function. These equations are solved by a straightforward “marching” technique, thus providing a solution with a minimum of computational effort. The “boundary‐layer equations” presented in this paper are not subject to the order to obtain the Prandtl boundary‐layer equations. The method outlined here represents an approximate solution for high Reynolds numbers, which gives surprisingly good agreement with the complete solution.
Nonlinear least squares analysis of catalytic rate models
Authors: Kittrell J. R. , Hunter W. G. , Watson C. C. 
Published: June 2004

AbstractConventional data generation and analysis procedures used to select a descriptive Hougen‐Watson reaction rate model have been reviewed and some statistical objections to these conventional procedures have been presented. In an attempt to assess the practical importance of these objections, a recently published example was analyzed with both conventional techniques and nonlinear least squares procedures, which more closely conform to theoretical weighting requirements. Comparisons were made between the results of the conventional linear least squares analysis of isothermal data and those of nonlinear least squares analyses of both isothermal and nonisothermal data. It was found that the nonlinear least squares procedures were useful for a rational selection of an acceptable model and estimation of its parameters.General observations were made concerning good regions for further experimentation if a discrimination among rival models is desired. Additional well‐designed experiments were found to be necessary to allow a reduction of the confidence region of the parameters of the Hougen‐Watson models to an acceptable size.
Chemical reaction in the turbulent wake of a cylinder
Authors: Saidel G. M. , Hoelscher H. E. 
Published: June 2004

AbstractA rapid, irreversible, second‐order chemical reaction in the turbulent wake of a cylinder was studied. A hypothesis relating the correlation of the fluctuating concentrations directly to the mean concentrations of the reacting species was found applicable, at least, when tested for a pseudo first‐order reaction system.Experimentally, the mean concentration profiles of a colored reactant were obtained with and without reaction by time‐exposure photographs. Since the reactant changed from colored to colorless during reaction, the rate of reaction could be determined directly from the rate of color disappearance.Both the reaction rate and the turbulent intensity divided by the half‐width of the wake were found to be inversely proportional to the distance from the source for x/d values from 35 to 180. This indicates a direct relationship between them. Consequently, the concentration correlation function also may be related directly to the turbulent intensity divided by the wake half‐width.In addition, it is shown that the rate of reaction is faster in the center of the wake than it is toward the edges.
Multicomponent vapor‐liquid equilibria at high pressures: Part II. Thermodynamic analysis
Authors: Chueh P. L. , Muirbrook N. K. , Prausnitz J. M. 
Published: June 2004

AbstractThermodynamic analysis is applied to high‐pressure vapor‐liquid equilibria in binary and multicomponent mixtures containing one or more noncondensable components. A thermodynamic consistency test is described, and a modification of van Laar's model is given for representing adjusted activity coefficients in binary and multicomponent liquid solutions up to the critical composition. With only experimental data used on the two binaries at 0°C., vapor‐liquid equilibria are calculated for the carbon dioxide–nitrogen–oxygen ternary at high pressures. Brief reference is made to the possibility of air separation by high‐pressure absorption in liquid carbon dioxide.
A study of slip ratios for the flow of steam‐water mixtures at high void fractions
Authors: Vance William H. , Moulton R. W. 
Published: June 2004

AbstractA technique employing the impulse plate principle was developed whereby the ratio of the average vapor‐to‐liquid velocities (slip ratio) for flowing two‐phase mixtures could be measured accurately at high vapor volume fractions. Data were collected for steam‐water mixtures flowing adiabatically in a horizontal ½‐in. tube. Flow conditions were in the spray annular and dispersed flow regimes and covered a pressure range of 30 to 80 lb.f/sq.in.abs., flow rates of 200 to 800 lb.m/(sec.)(sq.ft.), and steam qualities of 0.02 to 0.8. The experimental slip ratios, ranging between 1 and 3.5, decreased with increasing quality and pressure and increased with increasing mass velocity and pressure gradient.A theoretical analysis in which an idealized dispersed flow model was used indicated that the observed average slip ratios were caused largely by local slip between vapor and entrained droplets and that high local slip ratios may be attained near critical flow rates due to the simultaneously occurring steep pressure gradients.The total pressure gradients, computed by adding the Martinelli‐Nelson frictional pressure drop prediction to the acceleration pressure gradients calculated by the use of an empirical correlation of the slip ratio data, deviated from the experimental values by an average of only 14%.
The condensing of low pressure steam on vertical rows of horizontal copper and titanium tubes
Authors: Young Edwin H. , Briggs Dale E. 
Published: June 2004

AbstractHeat transfer data are presented for condensing steam at 2 in. Hg absolute pressure on the outside of nine copper and nine titanium horizontal tubes in a vertical row. The condensing coefficient correction factor was maximum for the top titanium tube and was 46% higher than the correction factor for the top copper tube. The difference between the correction factors for titanium and copper tubes diminished with the number of tubes in a vertical row to 8% higher than the correction factor for copper tubes with six to nine tubes in a vertical row.
Flow and turbulence in a stirred tank
Authors: Cutter Louis A. 
Published: June 2004

AbstractPhotographic measurements have been made of the mean and fluctuating components of velocity of water in a fully baffled stirred tank. Confirmation of much of the photographic data was obtained with a Kiel impact tube. Eulerian correlation coefficients and also Eulerian scales of turbulence were calculated from the photographic data. The Eulerian scale was of the same order as the blade dimensions, a result consistent with earlier measurements on the turbulence behind grids.Equations have been developed to describe the flow of energy and the conservation of angular momentum in the impeller stream of a stirred tank with a radial flow impeller and vertical baffles. These are simplifications of the Navier‐Stokes equations and the energy equation. They relate energy, angular momentum, and pressure to the mean and fluctuating components of velocity in the impeller stream.The equations derived are used with the photographic data on mean and fluctuating velocities to estimate the angular momentum at different radial sections of the tank and to calculate the flow of energy through these sections. The estimates are compared with more accurate values of the total torque and energy determined with a torque table.
Enthalpy determinations on the helium‐nitrogen system
Authors: Mage David T. , Katz Donald L. 
Published: June 2004

AbstractExperimental isobaric heat capacity and differential latent heat measurements have been made on the helium‐nitrogen system. Compositions studied were nominal 5, 25, 50, and 100% helium in nitrogen over the range 0 to 2,000 lb./sq.in.abs. and −250° to 50°F.These data, combined with the previously reported work on nitrogen and the Joule‐Thomson coefficients of Roebuck, are used to construct the complete pressure‐enthalpy‐composition network over the investigated limits of pressure and temperature.The enthalpies obtained from experimental heat capacity and Joule‐Thomson data are compared with enthalpies computed from PVT data. The changes of phase determined by differential latent heat measurements are compared with literature vapor‐liquid equilibrium data.This information is used to prepare pressure‐enthalpy diagrams for all the mixtures investigated. A three‐dimensional representation of the data on a pressure‐enthalpy‐composition diagram is presented. Constructions are outlined from which heats of mixing and partial molal enthalpies can be obtained.The thermodynamic network developed is believed accurate within 1% and should be of use to those concerned with low‐temperature separation of helium from nitrogen.
Dynamics of a tubular reactor with recycle: Part I. Stability of the steady state
Authors: Reilly M. J. , Schmitz R. A. 
Published: June 2004

AbstractAn analysis of the stability of a plug‐flow tubular reactor with recycle is presented for a model in which axial dispersion of heat and mass is neglected. A method is developed which permits determination of stability or instability for small disturbances immediately upon attainment of the steady state solution. The method, which is applicable to a large class of recycle processes, is based on a Newton‐Raphson iteration technique for steady state solution and on the stability theory of nonlinear difference equations. The feasibility of the method is demonstrated by means of numerical examples which illustrate the occurrence of steady state multiplicity and unstable situations.
The finite‐difference computation of natural convection in a rectangular enclosure
Authors: Wilkes J. O. , Churchill S. W. 
Published: June 2004

AbstractA study is made of the natural convection of a fluid contained in a long horizontal enclosure of rectangular cross section with one vertical wall heated and the other cooled. Two‐dimensional motion is assumed. The governing vorticity and energy transport equations are solved by an implicit alternating direction finite‐difference method. Transient and steady state isothermals and streamlines are obtained for Grashof numbers up to 100,000 and for height‐to‐width ratios of 1, 2, and 3.
Dynamic characteristics of perforated distillation plates operating at low loads
Authors: Chan B. K. C. , Prince R. G. H. 
Published: June 2004

AbstractAnalysis of the equations describing the instantaneous vapor and liquid flow through the holes of perforated distillation plates at low loads shows that periodic and stable pressure oscillations will always be set up between plates. These oscillations are expected to have amplitudes of the order of 0.1 in. of water and frequencies of a few cycles per second, values which are in accord with observation and which may be used as the basis for a model from which the seal point of the plates may be predicted.
Effects of interfacial instability on film boiling of saturated liquid helium I above a horizontal surface
Authors: Frederking T. H. K. , Wu Y. C. , Clement B. W. 
Published: June 2004

AbstractFilm boiling above a horizontal surface has been investigated theoretically and experimentally at standard gravity and 1 atm. Theoretical film boiling results for conventional fluids have been extended, on the basis of interfacial instability due to gravity, to include liquefied gases properties, such as low viscosity and small surface tension. In the experiments, primarily ordinary liquid helium I has been studied to extend the range of the film boiling Rayleigh numbers (based upon Laplace's reference length) from about 107 (reported for room temperature liquids) to values of the order of magnitude unity. The heat transfer data taken at surface excess temperatures ΔT (above the boiling point) between 80° and 300°K. have been correlated with a theoretical model which presumes the absence of any scaling length (Laplace length) associated with surface tension. At low ΔT the experimental results have been found to agree with a model which presumes a negligible influence of a scaling length due to surface tension and absence of detectable viscosity effects.
Surface motion and gas absorption
Authors: Muenz Kurt , Marchello J. M. 
Published: June 2004

AbstractThe influence of small surface waves on mass transfer from pure gases into water has been investigated. Small amplitude progressive two‐dimensional waves were mechanically generated at the liquid surface for the wave studies. Control experiments with nonwaved surfaces were also conducted. An effective diffusivity was used to correlate the data. Marked increases in mass transfer over that predicted by molecular diffusion for the no‐wave control runs are attributed to natural convection motions, and are probably caused by density and surface tension variations.
Simultaneous axial dispersion and adsorption in a packed bed
Authors: Chao Raul , Hoelscher H. E. 
Published: June 2004

AbstractA study has been made of simultaneous axial dispersion and solid‐fluid mass exchange in a packed‐bed adsorber. Four different and mutually exclusive controlling mechanisms for the solid‐fluid mass exchange rate are considered. A dimensionless parameter K characterizes this interphase mass transfer. The Peclet number characterizes axial dispersion.An impulse‐response technique was used to obtain simultaneously values of the axial Peclet number and the rate parameter K in the adsorption column. Values of the Peclet number obtained under conditions of interphase mass transfer were found to be significantly smaller than the values measured under pure mixing (no surface activity) conditions.The mathematical model used to analyze the results includes the particular case of no surface activity with results previously found from the dispersion model. One result not previously derived from the dispersion model was found and tested experimentally.
An analytical study of laminar counterflow double‐pipe heat exchangers
Authors: Nunge Richard J. , Gill William N. 
Published: June 2004

AbstractAn orthogonal expansion technique for solving a new class of counterflow heat transfer problems is developed and applied to the detailed study of laminar flow concentric tube heat exchangers. The exchanger problem is solved for fully developed laminar velocity profiles, negligible longitudinal conduction in the fluid streams and in the exchanger walls, and with fluid properties which are independent of the temperature.A description of the variation of the local Nusselt numbers and the temperature at the wall between the two streams is given. Also reported are bulk temperature changes in the two streams and mean overall Nusselt numbers. It is shown that for long exchangers, which are of some industrial importance, asymptotic Nusselt numbers exist in counterflow as in single‐phase and cocurrent systems. Numerical values of asymptotic Nusselt numbers are reported for a wide range of parameters. Comparisons are made with single‐stream solutions such as the Graetz problem, with empirical correlations of experimental data, and with cocurrent flow exchangers.To solve this problem it was necessary to derive new orthogonality relations, and also expressions for determining positive and negative sets of eigenvalues and eigenvectors. Satisfaction of inlet boundary conditions at both ends of counterflow exchangers requires a complete set of eigenfunctions and thus one must use both the positive and negative sets.
Transmethylation reactions of monomethyl and dimethylamine over montmorillonite in a flow system
Authors: Restelli Edward F. , Coull James 
Published: June 2004

AbstractIn this work the transmethylation reactions of monomethylamine and dimethylamine were investigated under steady state conditions in a flow system. A differential reactor was employed with montmorillonite as the catalyst and the initial rates of these reactions were measured isothermally. Mass velocities through the reactor were sufficiently high to eliminate bulk stream diffusion to the catalyst interface as a possible rate‐controlling step of the reaction process. Pore diffusion was checked experimentally and shown to impose no limit on reaction rates.The controlling phenomena of the reactions were determined by applying the Freundlich and Langmuir adsorption isotherms to the experimental results in the form of initial reaction rate vs. average partial pressure of reactant at constant temperature. Velocity constants and Arrhenius equations for these controlling processes were also determined.
Accessibility of surface to gases diffusing inside macroporous media
Authors: Hedley W. H. , Lavacot F. J. , Wang S. L. , Armstrong W. P. 
Published: June 2004

AbstractA method for measuring flow porosity with values from 35 to 100% of the open porosity measured is described. The accuracy of electrical conductivity measurement to obtain net diffusibilities was verified for media containing at least 75% of pore volume with radii greater than five mean free paths. It is pointed out that long dead‐end pores feeding into larger diameter flow pores can contribute to the effective diffusion coefficient inside porous media, and methods of estimating their length and maximum possible contribution to diffusion are described.
Binary physical adsorption of argon and nitrogen on fixed beds of activated silica gel
Authors: Camp David T. , Canjar Lawrence N. 
Published: June 2004

AbstractThe physical adsorption and desorption of argon and nitrogen on fixed beds of 18 × 20 mesh silica gel at −78.5°C. and 1 atm. have been studied. Binary mixtures containing 5.52, 10.34, 51.0, 90.16, 95.13 mole % nitrogen, as well as pure argon and pure nitrogen, were used. Superficial gas velocities were varied from 0.10 to 0.27 ft./sec. Concentration vs. time curves were obtained at bed depths of 5.3, 8.6, and 12.0 in.Resistance to mass transfer from the gas stream to the outside surface of the particles was found to be negligible. The rate is limited due to mass transfer from the outside surface to the internal surface of the particle. The data were correlated by the integrated Rosen diffusion solution with D = 9.60 (10−8) sq.ft./sec. or alternatively, by the Hiester and Vermeulen integrated model with kp = 0.23 sec.−1.
Bulk flow in diffusion coefficient studies
Authors: Board W. J. , Spalding S. C. 
Published: June 2004

AbstractThe viewpoint is taken that bulk flow terms in the general equation of molecular diffusion must be measured in apparatus which offers no constraint to the molecular flux in either direction. It is proposed to carry this out in a miniaturized experiment operating with one side of the diffusion gradient as an infinite sink. Dimethyl acetamide–water diffusivities computed from such an experiment were found to be 7.02 × 10−6 sq.cm./sec. over a wide range of compositions. These are compared with values showing considerably wider variation with composition, namely, 2.45 to 7.00 × 10−6 sq.cm./sec. by estimating methods and 11.45 to 14.05 × 10−6 sq.cm./sec. by large cell experiments. Arguments are presented in support of the values obtained by the proposed method operating on a nonideal binary N, N‐dimethyl acetamide and water.
Viscosity profiles, discharge rates, pressures, and torques for a rheologically complex fluid in a helical flow
Authors: Savins J. G. , Wallick G. C. 
Published: June 2004

AbstractQuantitative predictions are presented to show how the axial discharge rate and pressure gradient and angular velocity and torque become coupled when a fluid exhibiting a shear‐dependent viscosity behavior is subjected to a helical flow field. The numerical scheme developed here is completely general and applicable to a wide choice of constitutive equations. For purposes of illustration only, results are described for an Oldroyd type of constitutive equation. The coupling effect is illustrated for different relative speeds of the cylinders, axial flow rates, axial pressure gradients, and ratios of cylinder diameters. The most interesting consequence of the coupling effect is that the axial flow resistance is lowered in a helical flow with the result, for example, that for a given applied axial pressure gradient, the axial discharge rate in a helical flow field is higher than in a purely annular flow field.
Performance of fouled catalyst pellets
Authors: Masamune Shinobu , Smith J. M. 
Published: June 2004

AbstractEquations are developed for the bulk rate of a gaseous reaction on a porous catalyst whose activity changes with time due to a decrease in active surface. The performance is evaluated in terms of a pellet effectiveness factor which is a function of time and a Thiele (diffusion‐reaction) modulus. By a stepwise numerical technique, the equations can be solved without resort to assumptions regarding the distribution of fouled surface within the pellet. The method is applicable at isothermal conditions for any form of the rate equations for the main and fouling reactions and for any diffusivity‐concentration relationship.To illustrate the method, results are given for first‐order isothermal reactions for three types of fouling processes. For a series form of self‐fouling, a catalyst with the lowest intraparticle diffusion resistance gives the maximum activity for any process time. In contrast, for parallel self‐fouling a catalyst with an intermediate diffusion resistance is less easily deactivated and can give a higher conversion to desirable product, particularly at long process times.A simpler solution is possible by supposing that the shell model represents the disposition of fouling material in the pellet. It is shown that for parallel self‐fouling and independent fouling this model gives reasonably good results, even when the reaction resistance for the main reaction is important. However, the shell concept does not appear suitable over a range of conditions when the fouling is of the series type.The single‐pellet effectiveness factors can be used to determine the effect of fouling on the conversion in a fixed‐bed reactor. To illustrate the method of approach curves of conversion as a function of time and position in the bed are presented for a parallel, self‐fouling reaction system. The results show the influence of intraparticle diffusion on the overall effects of fouling.