bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimum design of conventional and complex distillation columns
Authors: Srygley J. M. , Holland C. D. 
Published: June 2004

AbstractA method is proposed for achieving the optimum design, in the sense of minimum plates, for conventional and complex distillation columns for any set of specifications directly dependent on product purity which might be imposed by the designer. The method uses the calculational procedure of Theiele and Geddes, the θ‐method of convergence, and sequential‐search procedures. Illustrative examples chosen from a large number of design problems solved by this method are presented.
The study of multicomponent gas‐solid equilibrium at high pressures by gas chromatography: Part II. Generalization of the theory and application to the methane‐propane‐silica gel system
Authors: Gilmer H. B. , Kobayashi Riki 
Published: June 2004

AbstractThe mathematical relation for the retention volume for elution chromatography has been extended to include the case of a multicomponent elution gas mixture in which all the components are adsorbed appreciably on the adsorbent. The total adsorption, component adsorption, and the K values or the ratio of the gas‐phase concentration to the adsorbed‐phase concentration for each component are related to the retention volume for the components as measured by a technique which distinguishes the molecules in the elution gas from those in the perturbing sample. Radioactively traced hydrocarbons are used in the application to obtain the retention volumes appropriate for the theory.The relations derived were applied in studying the adsorption of methane‐propane mixtures on silica gel up to a pressure of 1,000 lb./sq. in. abs. The internal consistency of the propane adsorption data with the propane infinite dilution data and the methane data with the pure methane adsorption data obtained by a gravimetric method is demonstrated.
Measurement of the void fraction in two‐phase flow by x‐ray attenuation
Authors: Pike R. W. , Wilkins Bert , Ward H. C. 
Published: June 2004

AbstractThe use of an x‐ray tube that emits a spectrum of energy was shown to be an effective source of monoenergetic radiaton for the measurement of the void fraction in two‐phase, steam‐water flow with the proper selection of the tube wall thickness, x‐ray tube operating conditions, collimation, and traverse time. Assuming monoenergetic radiation, equations were derived for the local and average void fraction and the statistical error associated with the measurement, and were confirmed to be applicable by using the mock‐up technique. This consisted of simulating the two‐phase, steam‐water flow patterns of the experimental system with mock‐ups of Lucite and air. Exprimental data are presented to show that confidence could be placed in the measurements to within the probable statistical error, as all deviations of the measured values of the void fraction from the actual values were less than the probable error. Local and average void fractions for steam‐water, two‐phase flow are given. Application to other systems can be inferred from these results.
Mixing effects in a spray‐column heat exchanger
Authors: Letan Ruth , Kehat Ephraim 
Published: June 2004

AbstractTemperature profiles were measured in a spray‐column heat exchanger 7.5 cm. in diameter and 167 cm. long between the inlets of warm kerosene and cold water. The temperature jump, at the inlet of the continuous phase, is a measure of the amount of mixing in the column and is a function of holdup and ratio of flow rates of the two phases. At holdup the temperature jump had a minimum value of 0.24.A physical model for heat transfer in a spray column based on hydrodynamic principles is proposed. Heat is transferred from drop to wake downstream of drop. Wakes are shed and mixed with the bulk water flow. New material enters the wake and is spilled out at higher temperatures.The physical model is applied to explain the data on temperature jumps in spray‐column heat exchangers and the data on concentration jumps in spray‐column extractors.
Adsorption kinetics in fixed beds with nonlinear equilibrium relationships
Authors: Tien Chi , Thodos George 
Published: June 2004

AbstractPrevious work by the authors on ion exchange kinetics for systems having nonlinear equilibrium relationships has been extended. Computer studies have produced additional concentration—bed length–time relationships for values of αo  5, 10, and 50. This information and the results obtained previously for values of αo  100 and 1,000 provide an extensive variation of the parameter αo for design applications. The composite results are represented graphically.
Suction nucleate boiling of water
Authors: Wayner P. C. , Kesten A. S. 
Published: June 2004

AbstractSuction nucleate boiling (consisting of saturated pool boiling on a porous heat source with the generated vapor exhausting through the pores) was investigated experimentally and theoretically. The experimental results demonstrated that: (1) interfacial free energy can be used to direct the flow of liquid and vapor in a desired direction and to separate vapor from liquid at the point of vapor generation; (2) the heat transfer coefficient for suction nucleate boiling is higher than that associated with normal boiling; and (3) a porous heat exchanger can be designed to give stable transition from nucleate to film boiling. The theoretical analysis, which was based on experimental observations, indicated that extremely high heat fluxes and heat transfer coefficients are possible with small pores. Comparison of the experimental and theoretical results demonstrated that the full potential of suction nucleate boiling was not attained in the experiments and indicated some of the experimental refinements neededto attain this potential.
Gas‐liquid mass transfer in cocurrent froth flow
Authors: Heuss J. M. , King C. J. , Wilke C. R. 
Published: June 2004

AbstractThe absorption of ammonia and oxygen in horizontal cocurrent gas‐liquid froth flow in a 1‐in. I.D. pipe has been investigated. At superficial liquid rates between 2 × 106and 3.2 × 106lb./(hr.)(sq.ft.) and superficial gas rates between 5 × 103and 18 × 103lb./(hr.)(sq.ft.), the length of a transfer unit in both systems was between 0.5 and 4.0 ft. The effects of distance and temperature were also investigated.With the use of James and Silberman's data on bubble size and distribution in froth flow to estimate average bubble sizes, the gas‐phase‐controlled ammonia absorption data could be explained by the model of unsteady state transfer from a stagnant sphere. With the use of an interfacial‐area estimate from the ammonia results, the liquid‐phase‐controlled oxygen absorption data were correlated by a Sherwood number characterizing the transfer from the bubbles, a Reynolds number characterizing the turbulence within the system, and the void fraction.
Analysis of heterogeneous catalytic reactions by nonlinear estimation
Authors: Lapidus Leon , Peterson T. I. 
Published: June 2004

AbstractIntegral conversion catalytic data have been studied by nonlinear estimation to determine whether the Langmuir‐Hinshelwood heterogeneous catalytic models are more valid than the simpler homogeneous noncatalytic forms, and whether it is possible to discriminate among models. The experimental system chosen for this study was the vapor phase dehydration of ethanol. Data for a similar hypothetical catalytic system were also generated and analyzed to highlight the effects arising in the ethanol dehydration case.Nonlinear estimation is shown to be a valuable adjunct in the study of reaction kinetics and mechanism. For the hypothetical system, the correct model was found to provide the best fit to the data. Linear regression, coupled with the usual criterion that models are acceptable if all parameter estimates are positive, did not provide this discrimination. For the experimental system of ethanol dehydration, as corroborated by the hypothetical system, such problems as degeneracy of the heterogeneous rate equations and comparatively large errors in measurement are shown to be obscuring factors in determining the best model. When these effects are involved, it is doubtful that the Langmuir‐Hinshelwood equations are more warranted than the simpler homogeneous forms.
Vapor‐liquid equilibrium in the methane–n‐hexane–nitrogen system
Authors: Poston Robert S. , McKetta John J. 
Published: June 2004

AbstractBecause varying amounts of nitrogen are found in hydrocarbon mixtures, a knowledge of vapor‐liquid equilibrium ratios for hydrocarbon‐nitrogen system is needed for petroleum reservoir studies and refinery calculations. Presented here are results of a quantitative investigation which shows how the K values of methane and n‐hexane change when varying amounts of nitrogen are added to mixtures of the two hydrocarbons.Analyses of equilibrium phases at different conditions of temperature and pressure in order to completely describe the phase equilibria of the system are presented. Temperature intervals of 60°F., starting at 100°F., and going up to 340°F. were used. At each temperature equilibrium samples were taken at 500 lb./sq.in.abs. and the pressure increased in 500 lb./sq.in.abs. intervals with samples taken at each interval up to 5,000 lb./sq.in.abs. or the critical pressure, whichever was lower.
Correlations of selectivity parameters for separations extractions of hydrocarbons with fluorochemicals
Authors: Munson M. S. B. 
Published: June 2004

AbstractThe equation In β12  ε12 xs2/T adequately represents the variation of the separation factors for the extraction of hydrocarbon mixtures with fluorochemicals. The selectivity parameter ε12 is a measure of the selectivity of a solvent for hydrocarbons 1 and 2 which is independent of the experimental conditions. With a given solvent it is possible to develop a correlation between εji for pairs of hydrocarbons and the heats of vaporization of these hydrocarbons. A group contributions method is also successful in correlating the selectivity parameters. The three fluorochemicals in these experiments, (C4 F9)3N, C7 F14, and C8F16O, had essentially the same selectivity for hydrocarbon separation which one would expect on the basis of their essentially identical solubility parameters.
Flow behavior of viscoelastic fluids in the inlet region of a channel
Authors: Metzner A. B. , White J. L. 
Published: June 2004

AbstractThe behavior of viscoelastic fluids in the inlet region of a channel formed by two parallel flat plates has been analyzed with a Rivlin‐Ericksen approximation to describe the fluid properties. It was found that viscoelasticity changed the entry length; both the magnitude and direction of this change predicted to depend upon the detailed fluid properties. These predictions of the change in the entry length were seen to find some qualitative support in available experimental evidence.The directions for further analysis, based primarily on the important observation that these materials may exhibit solidlike behavior in the immediate vicinity of the entrance, are indicated. This solidlike behavior is seen to be closely related to “melt fracture” and similar instability phenomena common to these materials; it serves to explain directly the otherwise perplexing observations concerning the similarity of such fluid fracture phenomena in materials as divergent in their properties as viscoelastic polymeric systems and inelastic dilatant slurries.
Effective wall heat transfer coefficients and thermal resistances in mathematical models of packed beds
Authors: Crider J. E. , Foss A. S. 
Published: June 2004

AbstractExpressions are derived for an effective wall heat transfer coefficient useful in one‐dimensional representations of heat transport in packed beds. These expressions are obtained with two mathematical models of a cylindrical packed bed: a partial differential model and a finite stage model. These expressions relate the effective wall heat transfer coefficient, which is a local coefficient, to the actual wall heat transfer coefficient and the bed diameter (and the radial Peclet number in the partial differential model) in regions of the bed where similar temperature profiles obtain. These relations involve a single dominant root of an equation characteristic of the heat balance equations of each model.From these relations, expressions for an effetive thermal resistance of the bed are obtained. For each model, this bed resistance is found to be an approximately linear function of the bed diameter and to be rather insensitive to the actual wall heat transfer coefficient. For each model, an approximate bed resistance is found that is not dependent upon the actual wall heat transfer coeficient and with which the effective wall heat transfer coefficient can be estiamted with an error of less than 7%.
Analysis and design of gas flow reactors with applications to hydrocarbon pyrolysis
Authors: Trombetta Michael L. , Happel John 
Published: June 2004

AbstractThe analysis and design of gas flow reactors are customarily based on a plug flow model. Because of transverse concentration and temperature gradients, however, kinetic constants and reactor lengths based on the plug flow model may be in gross error. This paper presents an approximate method of analysis which accounts for the effects of these gradients. We examine a gas in laminar flow which supports a first‐order irreversible reaction. Compressibility effects are considered, and the diffusion fluxes are calculated with the full ternary diffusion equations. Instead of solving exactly the full equations of change which describe this system, the well‐known Pohlhausen technique is adapted and approximate solutions which satisfy the integral forms of these equations are sought. This reduces the problem to the solution of a set of ordinary differential equations, which are integrated numerically. The main result is a set of graphs giving correction factors to be applied to plug flow kinetic constants and reactor lengths. Although primary interest is in hydrocarbon pyrolysis systems, the integral method graphs are applicable to other reaction systems.
Evaporation from falling saline water films in laminar transitional flow
Authors: Unterberg Walter , Edwards D. K. 
Published: June 2004

AbstractAn analytical and experimental study was made of the evaporation from pure and saline water films flowing down a heated vertical surface at Reynolds numbers between 160 and 600. Visual observation showed free surface evaporation. Film continuity was poor for pure water, but good for saline water, because of the influence of temperature and salinity on surface tension gradients. Evaporation rates were predicted by (1) a constant‐property boundary‐layer type of laminar analysis; (2) the constant‐property Dukler “eddy” treatment; and (3) a variable property laminar analysis that took into account the boiling point elevation due to salinity. The experimental evaporation rates could be correlated by dimensionless moduli arising out of the laminar analyses, but best quantitative agreement was found with the Dukler eddy treatment.
Direct contact heat transfer with change of phase: Effect of the initial drop size in three‐phase heat exchangers
Authors: Sideman Samuel , Hirsch Gideon , Gat Yehuda 
Published: June 2004

AbstractThe initial drop size of volatile fluids evaporating within immiscible, nonvolatile liquids was experimentally related to the overall heat transfer coefficient in single and multiparticle systems. Coalescence and turbulence diminish the effects of the initial size, which are thus limited to the lower part of the exchanger where single‐drop characteristics are maintained. Condensation data of single bubbles are in good agreement with the single‐drop relationship.
The influence of gravitational force on gas absorption in a packed column
Authors: Vivian J. E. , Brian P. L. T. , Krukonis V. J. 
Published: June 2004

AbstractCarbon dioxide was desorbed from water in a packed column mounted on a large centrifuge. By varying the centrifuge rotational speed, the total body force acting upon the liquid was varied from 1 to 6.4 times the normal gravitational force. The results, obtained for ¾ in. Rasching ring packing, showed kLa varying with the body force to a power between 0.41 and 0.48, the exponent being larger at lower liquid flow rates. This effect of gravity is compared with penetration theory predictions and with those inferred from dimensional analysis and the effect of packing size.
Partial oxidation of o‐xylene in melts containing vanadium pentoxide
Authors: Satterfield Charles N. , Loftus Jordan 
Published: June 2004

Abstracto‐Xylene vapor in nitrogen was partially oxidized by bubbling it through a melt of the 39 wt. % vanadium pentoxide‐potassium sulfate eutectic at temperatures from 528° to 598°C. The principal product was o‐tolualdehyde; some benzene and traces of phthalide were formed but no organic acids. These products are similar to those found in o‐xylene oxidation over a solid vanadium oxide catalyst, except for the absence of acid products but are far different from the product distribution found from homogeneous oxidation with air. The rate of reaction per unit of gas‐melt interface was approximately equal to that reported for oxidation of o‐xylene in air on an unsupported fused vanadium oxide catalyst. With o‐xylene‐air mixtures bubbled through either a vanadium pentoxide‐potassium sulfate eutectic melt or vanadium pentoxide‐potassium pyrosulfate melt, homogeneous reaction obscured any contribution from heterogeneous processes.
Obtaining precise parameter estimates for nonlinear catalytic rate models
Authors: Kittrell J. R. , Hunter W. G. , Watson C. C. 
Published: June 2004

AbstractA method is reviewed which allows data points to be chosen in such a fashion that precise estimates of the parameters in nonlinear reaction rate models can be obtained. This method allows each future data point to be selected such that the confidence region of the estimated parameters is smaller with it than with any other possible data point within the region of experimentation. This procedure is applied for Hougen‐Watson models with hypothetical experimental data which were generated with the guidance of an example from the current chemical engineering literature. It is found that, for the same number of data points, the parameters in the model can be estimated eighteen times more precisely by using this suggested experimental design than by another commonly used design. Confidence regions are presented for the parameters of the Hougen‐Watson models with two types of designs.It is found that the positions of the data points in the well‐designed experiments are more sensitive to the functional form of the model than to the current estimates of the magnitudes of the parameter values.
Mechanism of dispersed‐phase mass transfer in viscous, single‐drop extraction systems
Authors: Johns L. E. , Beckmann R. B. 
Published: June 2004

AbstractThe theory of solute extraction in viscous single‐drop systems is extended to show (1) the dependence of the asymptotic Nusselt number on the Peclet number from NPe = 0, the molecular diffusion limit, to NPe = ∞, the Kronig and Brink limit, and (2) the dependence of the diffusion entry region Nusselt number on the Peclet number and the initial concentration profile.A numerical solution of the diffusion equation, limited to dilute solute concentrations and solute transport by viscous convection and molecular diffusion, is presented from which the nature of the Nusselt number is deduced. The observed oscillatory behavior of the Nusselt number in the diffusion entry region, as NPe → ∞, is given a simple physical interpretation in terms of the circulation period of the drop liquid.The model is based upon the Hadamard stream function which theoretically is limited to creeping flow; however some experimental evidence indicates that flow fields similar to the Hadamard stream function exist at continuous phase Reynolds numbers of the order of ten.
Momentum, heat, and mass transfer in turbulent non‐Newtonian boundary layers
Authors: Skelland A. H. P. 
Published: June 2004

AbstractThe boundary‐layer equations and a Blasius type of relationship between f and NRe gen are used to derive expressions for velocity distribution, local boundary‐layer thickness, local shear stress, and total drag force for the turbulent boundary‐layer flow of a power law non‐Newtonian fluid across a flat plate at zero incidence. Relationships are derived for the velocity at the edge of the laminar sublayer and for the thickness of the laminar sublayer.An analogy between heat and momentum transfer is then used to obtain expressions for local and mean values of the heat transfer coefficient in a turbulent thermal boundary layer for power law materials flowing over flat plates. Analogous extensions to mass transfer are indicated.A tentative criterion is suggested for characterizing the transition from laminar to turbulent boundary‐layer flow of power law fluids.Relationships combining the effects of a part laminar, part turbulent boundary layer are presented.
Identification and adaptation in control loops with time varying gain
Authors: Mellichamp D. A. , Coughanowr D. R. , Koppel L. B. 
Published: June 2004

AbstractA method is presented to apply the gain identification procedures developed in a companion paper to a control system. The method employs a small identification tank which follows the control tank; the identification tank is perturbed to estimate the gain of the process (controlled tank system). The effects of load changes on the identification system are minimized by this approach.The results of analog and digital computer simulations of this adaptive process are given. Both a general system with linear change in gain and a pH control system with a step change in concentration of the buffer species are studied. Process gain changes up to 20:1 are introduced.It is concluded that an adaptive control system of this type can be designed to maintain good control characteristics in a process experiencing wide gain variation. Criteria are presented to aid in the design of an adequate identifier.
Effect of ultrasonic waves on mass transfer rates of selected fluids
Authors: Fogler H. Scott , Timmerhaus Klaus D. 
Published: June 2004

AbstractThe application of ultrasonic energy to a fluid in a capillary has resulted in greatly increased rates of mass transfer (of the order of 800 to 2,000% above that without insonation) to occur at specific heights in the capillary. Reproducible results with several selected fluids (carbon tetrachloride, acetone, ethanol, and methanol) have shown that these specific heights are always at the half wavelengths of the particular fluid investigated. The mathematical model developed herein predicts that at these half wavelengths, the fluid particle displacement of the ultrasonic wave becomes quite large, exceeds the threshold value necessary for the stability of the surface waves, and causes droplets to be ejected into the vapor above the surface in the form of a fog. The resulting decrease in the diffusional path length of the ejected fluid provides the final mechanism for an increased mass transfer from the capillary tube.