bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal cracking of light hydrocarbons and their mixtures
Authors: Froment Gilbert F. , Van De Steene Boudewijn O. , Vanden Berghe Philip J. , Goossens A. G.
Published: June 2004

The kinetics and product distributions of the thermal cracking of binary and ternary mixtures of ethane, propane, n‐ and i‐butane were determined in a pilot plant under conditions of residence time, temperature, total pressure, and dilution as close as possible to those prevailing in industrial operation. The kinetics and yields observed with ternary mixtures were compared with those obtained with binary mixtures and with pure components. The experimental selectivities were compared with those which would be obtained from separate cracking and subsequent addition of the product streams. The deviations between the two can be predicted by means of the so‐called global kinetics selectivities, which are based upon the selectivities obtained from the pure components cracking and upon the global rates of cracking of the feed components in the mixture.
A rigorous method for predicting the critical properties of multicomponent systems from an equation of state
Authors: Peng Ding‐yu , Robinson Donald B.
Published: June 2004

This paper shows how the rigorous critical state criterion enunciated by Willard Gibbs can be used with a recently formulated two‐parameter equation of state to obtain an analytical solution to the problem of predicting the critical properties of defined multicomponent mixtures. Comparisons are made between predicted and experimental values for several systems containing paraffin hydrocarbons and related materials.
Formation of an air‐water two‐phase flow
Authors: Adler Pierre M.
Published: June 2004

The geometrical parameters of injection devices are shown to have almost no effect on the resulting two‐phase flow, while they influence the pressure drop owing to its formation. The predominant hydrodynamic parameter is the ratio of the mean superficial velocities. A simplified analysis leads to good agreement with experimental results. The different causes of pressure drops are quantified.
Flow of slurries in pipelines
Authors: Turian Raffi M. , Yuan Tran‐Fu
Published: June 2004

Pressure drop correlations for flow of slurries in pipelines were developed for each of the following four flow regimes: flow with a stationary bed, saltation flow, heterogeneous flow, and homogeneous flow. A total number of 2 848 data points, comprised of 1 912 collected from the published literature together with 936 taken using our own test pipelines and relating to ranges of the pertinent variables extensive enough to span all four flow regimes were used as the basis of these correlations. Also, these data were used in developing an associated quantitative regime delineation scheme. The correlations provide an improved predictive capability over previously available procedures and are also broader in scope. The delineation procedure developed here permits straightforward classification of the data according to the flow regime prevailing, and it is moreover inclusive of all the data and is self‐consistent.
Transport of nitrate ion in unsteady, unsaturated flow in porous media
Authors: Hildebrand Margaret A. , Himmelblau David M.
Published: June 2004

A simplified model of nitrate ion transport (and other nonadsorbing solutes) in unsteady, unsaturated flow in porous media has been developed. The model represents nitrate flow in infiltration and drainage in sand quite well and can be applied to unsaturated flow in other homogeneous media with only minimum extra experimental data needed to describe the medium.
Vacuum stripping of refrigerants in water sprays
Authors: Lin Wen‐Cheng , Rice Philip A. , Cheng Yung‐Sung , Barduhn Allen J.
Published: June 2004

The number of overall liquid transfer units as a function of the total pressure, flow rate, and nozzle height has been measured for the removal of butane and F‐22 refrigerants from water for a flat spray nozzle in a vacuum spray chamber. The number of transfer units increases with the flow rate and with the total pressure with the increase proportional to 0.2 power of the Weber number in which the gas density is used. NOL also increases linearly with length, but more than two‐thirds of the mass transfer always takes place in liquid sheet attached to the nozzle. Because the rate of mass transfer in a spray chamber is much greater than in a packed column, vacuum spray stripping is recommended for the removal of refrigerants from water and brine in the freezing and hydrate processes for desalination and other slightly soluble gases from aqueous solution in other processes.
Absolute evaporation rates for some polar and nonpolar liquids
Authors: Lednovich Sandra L. , Fenn John B.
Published: June 2004

A method was developed for providing continuously wiped and, therefore, clean liquid surfaces in vacuo. By means of a mass spectrometer detector, the absolute evaporation flux from such clean surfaces was measured for diethylene glycol, glycerine, dibutyl phthalate, and oleic acid. The molecular flux from equilibrium vapor was also measured by the same detector. The ratio of the former to the latter, the evaporation coefficient, was found in each case to be close to unity and independent of the temperature.
Vapor‐liquid equilibrium of hydrogen/tetralin system at elevated temperatures and pressures
Authors: Simnick J. J. , Lawson C. C. , Lin H. M. , Chao K. C.
Published: June 2004

A flow type of apparatus is built to give equilibrium gas and liquid samples at elevated pressures and temperatures while minimizing thermal decomposition. Saturated vapor and liquid compositions and K values are determined with this apparatus for the binary system hydrogen/tetralin (1,2,3,4‐tetrahydronaphthalene) at four temperatures from 189.6° to 389.1°C, and seven pressures from 20 to 250 atm. Vapor pressures of tetralin are determined with the same apparatus, and values are reported at the four temperatures of this work.
Vacuum‐spray stripping of sparingly soluble gases from aqueous solutions: Part I. Mass transfer from streams issuing from hydraulic nozzles
Authors: Simpson Stuart G. , Lynn Scott
Published: June 2004

Carbon dioxide, oxygen, Freon 114, and butane were stripped from deionized water, sodium chloride solutions, and freshly acidified seawater in a vacuum‐spray chamber using three types of hydraulic nozzle. Purely physical desorption was found for each gas/liquid system.

For both conical‐spray and fan‐jet nozzles, the bulk of the gas was shown to desorb from the thin liquid sheet issuing from the nozzle, that is, before droplet formation occurs. Behavior was explained semiquantitatively by a mathematical model of the diffusion in the sheet. This model was also shown to predict well the desorption from the laminar liquid sheets formed by jet impingement nozzles. For turbulent flow in jet impingement nozzles, the fit of the model was again semiquantitative.
Separation of proteins via semicontinuous pH parametric pumping
Authors: Chen H. T. , Hsieh T. K. , Lee H. C. , Hill F. B.
Published: June 2004

A semicontinuous pH parametric pump for separating proteins was experimentally investigated using the model system haemoglobin and albumin on a Sephadex ion exchanger. The pump considered had a center feed between an enriching column and a stripping column and was operated batchwise during upflow and continuously during downflow. Various factors affecting separations were examined. It was shown that parametric pumping is capable of separating proteins with high separation factors.
Multivariable computer control of a butane hydrogenolysis reactor: Part I. State space reactor modeling
Authors: Jutan Arthur , Tremblay J. P. , MacGregor J. F. , Wright J. D.
Published: June 2004

A state space model is developed for an existing nonadiabatic packed‐bed reactor which experiences axial and radial concentration and temperature gradients resulting from highly exothermic reactions involving several chemical species. The set of partial differential equations is reduced from three to two dimensions using orthogonal collocation. Further use of orthogonal collocation on the quasi steady state version of the differential equations results in a set of coupled algebraic and differential equations from which a linearized low‐order state space model is obtained. The model parameters are estimated from reactor data, and the fitted model is used for design and implementation of a multivariable stochastic control schemes on the reactor. These applications are described in parts II and III of this paper.
Effect of dimethyl sulfoxide on drug permeation through human skin
Authors: Chandrasekaran S. K. , Campbell P. S. , Michaels A. S.
Published: June 2004

The effect of the presence of dimethyl sulfoxide (in admixture with water) on the sorption and permeation rate of scopolamine base in human skin in vitro has been measured as a function of drug concentration in aqueous solution. The equilibrium sorption of scopolamine by skin from solution appears to be unaffected by the presence of even high concentrations of dimethyl sulfoxide in the solution phase. In the absence of a transdermal gradient of DMSO (or water), the permeability of skin to scopolamine in the presence of DMSO is about twofold higher than in its absence, suggesting that the diffusivity of scopolamine in the stratum corneum is somewhat elevated by the solvating action of DMSO.

When, however, a gradient of DMSO concentration is impressed across the skin (irrespective of whether that gradient is of the same or opposite sign to that of the drug), the permeability of the skin to scopolamine is increased by one to two orders of magnitude. Microscopic examination of the skin subjected to such treatment reveals marked swelling, distortion, and intercellular delamination of the stratum corneum, which is only partially reversible following complete extraction with water. These effects are believed due to development of very high osmotic stresses produced within the stratum corneum, as both water and DMSO are transported into the tissue.
Deposition of solid particles on a collector: Formulation of a new theory
Authors: Wang Chiu‐Sen , Beizaie Masoud , Tien Chi
Published: June 2004

Two concepts concerning the deposition of particles from suspension onto a collector, the shadow effect due to deposited particles and the singular and random behavior of approaching particles, are presented and discussed. Based on these concepts, a new theory of particle deposition is proposed and procedures for the simulation of deposition process outlined. The simulation results give the rate of deposition and the deposit morphology. Potential applications of this model to a number of technical problems are outlined.
Simulation of particulate systems using the concept of the interval of quiescence
Authors: Shah B. H. , Ramkrishna Doraiswami , Borwanker J. D.
Published: June 2004

A simulation procedure is presented in this work which can analyze the behavior of any dispersed phase system consisting of particles whose random behavior is specified in terms of probability functions. The procedure distinguishes itself from its predecessors in being free from arbitrary discretization of time or any other parameter along which the system evolves, and its ability to predict the behavior of randomly behaving small populations. Where population balance equations, which describe the behavior of particulate systems, cannot be readily solved, the simulation technique presented herein represents an efficient alternative to the modeling of such systems. Tables and a flow chart are given which would enable the use of the method for any system with specified particle behavior.
Properties and structure of polymeric alloys
Authors: Shen Mitchel , Kawai Hiromichi
Published: June 2004

Because of the generally immiscible nature of polymers, multicomponent polymers or polymeric alloys often exhibit microphase separation. The morphologies of these heterogeneous materials are determined not only by the composition of the system, but also by the processing conditions. The resulting microstructures exert a profound influence on the properties of the polymeric alloys. The purpose of this review is to discuss the more recent advances in the investigation of the relation between the structure of the polymeric alloys and their properties. An understanding of this relationship would be important in being able to tailor make better materials and exploit the unique properties of these materials for engineering applications.
Pore diffusion in packed‐bed reactors containing immobilized glucoamylase
Authors: Swanson Steven J. , Emery Alden , Lim Henry C.
Published: June 2004

Conversion was measured in small packed‐bed reactors containing immobilized glucoamylase in a range of variables in which diffusion was an important limitation. Three sets of data involving two carriers and two temperatures agreed satisfactorily with the theory of simultaneous reaction and diffusion.

Several reactors were designed for 99% conversion, and the results show that diffusion is a small problem when feed concentration is high but a serious problem at low concentration, requiring careful design of the catalyst. The particle size needed to eliminate the effect of diffusion is shown as a function of length.
Collocation solution of creeping newtonian flow through periodically constricted tubes with piecewise continuous wall profile
Authors: Neira Mariano A. , Payatakes A. C.
Published: June 2004

A collocation solution of creeping Newtonian flow through periodically constricted tubes is obtained. The profile of the wall of the type of tube considered is piecewise continuous, composed of symmetric parabolic segments. A transformation of the domain of interest into a rectangular one is obtained, which allows satisfaction of all boundary conditions. The collocation solution gives the stream function in terms of the new independent variables and can easily be converted to the original cylindrical coordinates. Axial and radial velocity components are obtained in analytical form, and the pressure drop is calculated from a volume integration of the viscous dissipation function as well as from line integration of the Navier‐Stokes equation. The results are compared with the finite‐difference solution by Payatakes et al. (1973b) and are found in good agreement. Differences between the two solutions are attributed mainly to discretization error in the finite‐difference solution. The analytical expressions obtained from the collocation solution can be used together with porous media models of the constricted unit cell type for the modeling of processes taking place in granular porous media.
Droplet size spectra generated in turbulent pipe flow of dilute liquid/liquid dispersions
Authors: Karabelas A. J.
Published: June 2004

Experiments were carried out with water dispersed in hydrocarbons at various flow rates. The measured size spectra can be well represented by either an upper limit log‐probability function or a Rosin‐Rammler type of equation with constant parameters and only one variable, the maximum drop diameter dmax or d95. The latter can be predicted satisfactorily by a correlation based on the Hinze/Kolmogorov model of droplet breakup.
Transient diffusivity measurements in catalyst pellets with two zones of differing diffusivities
Authors: Chou Tai‐Sheng , Hegedus L. Louis
Published: June 2004

Transient pulse diffusivity measurements were carried out in a pellet string reactor. The outer skin of the catalyst spheres was partially obstructed by contaminants, and the objective was to determine the diffusivity both in this obstructed skin and also in the unobstructed core.

Conservation equations were formulated which describe the transient diffusion process in catalyst pellets with two interconnecting regions of differing diffusivities. The shape of the elution curve from a packed bed with axial dispersion was computed by numerical inversion of the Laplace transformed solutions for a Dirac delta function input.

The calculations indicated that if an appropriate residence time is chosen, the elution curve shape should be sensitive to the differing diffusivities of the two zones in the catalyst pellets.

The experimental peak shapes were analyzed by the Fourier analysis technique and the diffusivities were extracted by the Constrained Simplex optimization routine. The results showed good resolution of the different diffusivities in the skin and the core of the catalyst pellets.
Parametric studies in industrial distillation: Part I. Design comparisons
Authors: Tedder D. William , Rudd Dale F.
Published: June 2004

Minimum cost surfaces compare eight distillation systems separating ternary feeds. The region of optimality for a design varies with the species separated, but some tower configurations are always preferred at particular feed compositions.
SCP production on C1 compounds
Authors: Papoutsakis Eleftherios , Lim Henry C. , Tsao George T.
Published: June 2004

Given the partial oxidation products of methane as the chemical feedstock for single‐cell protein (SCP) production, their conversion efficiency is optimized by optimal selection of the pertinent microorganisms that can utilize the feedstocks. The coenzymes of the three oxidation steps from methanol to formaldehyde to formate and carbon dioxide as well as the pathway involved in carbon fixation determine the cell‐mass yield. Microorganisms which follows the ribulose monophosphate cycle and which have coenzymes which are linked to the maximum production of ATP (for example, NAD linked dehydrogenases), should be searched for economical production of SCP. Batch growth rate and yield data are limited in utilization and interpretation, and care should be exercised in their use. The subject of this case study, Methylomonas EP‐1, gives an optimal cell mass yield of 65% and a stable chemostat operation at space velocities as high as 0.58 hr−1.
Theory of draw resonance: Part I. Newtonian fluids
Authors: Hyun Jae Chun
Published: June 2004

Draw resonance in isothermal spinning is explained by using kinematic wave theory. The throughput wave equation and the expression for the throughput wave velocity are derived from the governing equations of the system, that is, the continuity, momentum, and constitutive equations. A comparison is made between twice the wave residence time and the threadline residence time from the spinneret to the take‐up in order to find the stable and draw resonance regions in terms of the drawdown ratio. For Newtonian fluids, the critical drawdown ratio to cause the onset of draw resonance is 19.744.

Part II will deal with draw resonance in the spinning of power law fluids and Maxwell fluids using the same wave theory. Calculation of the draw resonance amplitude when the drawdown ratio exceeds the critical values for Newtonian, power law, and Maxwell fluids will be explained in Part III.

To be published at a later date.
Inferential control of processes: Part II. The structure and dynamics of inferential control systems
Authors: Brosilow Coleman , Tong Martin
Published: June 2004

The static estimator of part I is incorporated into a dynamic control system. The system structure minimizes output feedback and thereby achieves stability even in the event of significant modeling errors. This inherent stability permits the use of simple and economical lead‐lag compensation for the estimator and controller portions of the system. The overall system response to disturbances is similar to that of feed‐forward control systems.

The proposed control system structure is used to infer and control the overhead and bottoms product compositions of a simulated multicomponent distillation. Product compositions are inferred from selected stage temperature and process flow measurements. Inferential control system response to various disturbances is comparable or superior to that of a tuned composition feedback control system for both single product control and for simultaneus overhead and bottoms product control.
Measurement of the surface ages of water jets
Authors: Davies J. T. , Makepeace R. W.
Published: June 2004

Experimental values of the surface velocities vs of water jets have been obtained by high speed flash cine photography of talc particles on the surfaces of both laminar and turbulent jets. Values of the surface ages as defined variously by Defay and Hommelen (1958), Hansen (1964), and Harper (1973) have been obtained from our data for both pure water and for dilute solutions of surface active agents.

We find, by comparison with published entry length corrections for gas absorption, that x/vs gives the most reasonable age of the surface at any distance x along a jet of pure water.

If a surface active agent is present in the water, the amount of adsorption of a few millimeters downstream from the nozzle is of the order ten times greater than calculated for laminar jets and five to six times greater than calculated for turbulent jets at Ren = 18 800. This we ascribe to liquid circulation in the jet adjacent to the nozzle, caused by the Marangoni surface flow, which also reduces vs significantly.
Velocity distributions in die swell
Authors: Whipple Bruce A. , Hill Christopher T.
Published: June 2004

Photographs of tracer particles were used to measure axial and transverse velocity components throughout the entire die swell region in a slit die. Laminar extrusion was investigated for two fluids: a viscoelastic concentrated solution of a polyacrylamide in glycerin and water and a highly viscous, nearly Newtonian, silicone oil. The die swell region extends upstream to the viscometric flow region and downstream to the relaxed portion of the extrudate. The data are used to evaluate several theories of die swell.
Phase‐plane analysis of feedback control of unstable steady states in a biological reactor
Authors: Dibiasio David , Lim Henry C. , Weigand William A. , Tsao George T.
Published: June 2004

Feedback control of an open loop, unstable, continuous flow, stirred‐tank biological reactor was investigated theoretically using several microbial growth models. The closed loop system can be made globally stable, but constraints on the manipulated variable can lead to as many as five steady states, which are either saddle points or locally stable nodes.
Hydrodynamic stability of thin liquid films flowing down an inclined plane with accompanying heat transfer and interfacial shear
Authors: Yih Siu‐Ming , Seagrave Richard C.
Published: June 2004

An analysis is made on the influence of heat transfer and interfacial shear on the hydrodynamic stability of thin liquid films flowing down an inclined plane. The linear stability of the flow is determined by a successive perturbation solution of the governing Orr‐Sommerfeld equation modified to include the effects of temperature on viscosity. Stability criteria are presented which show that a cooled wall is destabilizing, while a heated wall is stabilizing. The surface perturbation stresses of the concurrent gas shear are also shown to be destabilizing factors. Neutral stability curves are presented and compared with the isothermal case.
Perturbed hard chain theory for fluid mixtures: Thermodynamic properties for mixtures in natural gas and petroleum technology
Authors: Donohue M. D. , Prausnitz J. M.
Published: June 2004

Perturbed‐hard‐chain theory for pure fluids, proposed previously by Beret, is modified slightly to yield better pure‐component results. More important, it is extended to multicomponent mixtures.

The perturbed‐hard‐chain theory is a synthesis of the polymer solution theories of Flory and Prigogine and the perturbed‐hard‐sphere theories of Alder and Barker and Henderson. The resulting equation of state is applicable to simple as well as complex molecules (for example, heptane, naphthalene, polystyrene). It can be used to calculate both gas and liquid phase properties. Extension of perturbed‐hard‐chain theory to mixtures is based on a one‐fluid model without, however, making the usual assumption of random mixing.

The perturbed‐hard‐chain theory has been applied to most fluids commonly encountered in natural‐gas and petroleum refining operations. The theory gives good agreement with experiment for pure‐component and fluid‐mixture properties including vapor pressures, liquid densities, enthalpies, and K factors. Molecular parameters have been obtained for forty‐five pure components and for more than sixty binary mixtures. Ternary and higher mixtures require no additional parameters.
A comprehensive experimental investigation of tubular entry flow of viscoelastic fluids: Part I. Vortex characteristics in stable flow
Authors: Cable P. J. , Boger D. V.
Published: June 2004

The characteristics of a vortex found at the entry of a 2:1 and 4:1 contraction for viscoelastic fluids is investigated. Two distinct flow regimes are identified in the contraction flow field: a vortex growth regime and a divergent flow regime. In the vortex flow regime, rheological forces are found to dominate the flow, with the vortex detachment length being a linear function of the Weissenberg number. In the divergent flow regime, the flow is found to diverge at the center line upstream of the vortex detachment plane, and the vortex size decreases with increasing flow rates. Inertial forces are important in the divergent flow regime. The entry flow characteristics for the 2:1 and 4:1 contraction are quantified in terms of the vortex detachment length as a function of Reynolds and Weissenberg number over the range of 0:2 < N′Re < 200 and 0.10 < NWS < 0.7.
Transient gas‐liquid flow in horizontal pipes: Modeling the flow pattern transitions
Authors: Taitel Yehudah , Lee Naugab , Dukler A. E.
Published: June 2004

The theory for predicting flow pattern transition under transient flow conditions is developed and compared with experiment. This work represents an extension of the methods presented by Taitel and Dukler (1976) for steady state flows. Under transient conditions, flow pattern transitions can take place at flow rates substantially different than would occur under steady flow conditions. In addition, flow patterns can appear which would not be expected for a slow change in flow rates along that same path. Methods are presented for predicting the flow rates at which flow pattern transitions will take place during flow transients. The method also reveals when spurious flow patterns will appear.
Vapor‐liquid equilibria in multicomponent aqueous solutions of volatile weak electrolytes
Authors: Edwards T. J. , Maurer Gerd , Newman John , Prausnitz J. M.
Published: June 2004

A molecular‐thermodynamic correlation is established for calculating vapor‐liquid equilibria in aqueous solutions containing one or more volatile electrolytes: ammonia, carbon dioxide, hydrogen sulfide, sulfur dioxide, and hydrogen cyanide. The correlation is similar to that presented in 1975, but the domain of application has been increased. The present correlation holds from about 0° to 170°C and for ionic strengths of about 6 molal; for the weak electrolytes considered here, this corresponds to total concentrations between 10 and 20 molal. To represent activities at these high concentrations, activity coefficients are expressed as a function of molality by Pitzer's equation. Required parameters are estimated from data reduction or from correlations.

Special attention is given to the ternary systems ammonia‐carbon dioxide‐water and ammonia‐hydrogen sulfide‐water. Calculated equilibria are in satisfactory agreement with the severely limited experimental data now available.
Bubble motion and mass transfer in non‐Newtonian fluids: Part I. Single bubble in power law and Bingham fluids
Authors: Bhavaraju S. M. , Mashelkar R. A. , Blanch H. W.
Published: June 2004

The Sherwood number and drag coefficient for a single gas bubble moving in a power law fluid and a Bingham plastic fluid are obtained using perturbation methods. The perturbation parameters for power law and Bingham plastic fluids are m (= n – 1/2) and E (= R/U), respectively. It is found that in the case of power law fluid, mass transfer and drag increase with increasing pseudoplasticity. These theoretical results are found to be in good agreement with the available experimental data and the data obtained in the present study. In the case of Bingham plastic fluid, mass transfer and drag are found to increase with increase in the Bingham number NB (= 2ε). Contours of plug flow regions, where local stresses are less than the yield stress, are obtained as a function of the Bingham number NB. These results qualitatively predict the zero terminal velocity observed for bubble motion in liquids with very high yield stress. They are also in good agreement with the trends of the results obtained previously for solid sphere motion in Bingham plastic fluids.
Stratified turbulent‐turbulent gas‐liquid flow
Authors: Cheremisinoff Nicholas P. , Davis E. James
Published: June 2004

This paper is an experimental and theoretical study of horizontal stratified gas‐liquid two phase flow in a circular tube. Both phases are considered to be in turbulent flow, and the liquid phase flow field is modeled by applying eddy viscosity expressions developed for single phase flow. The pressure drop and in situ volume of liquid are predicted from the gas and liquid flow rates, physical properties, and pipe size by means of an iterative procedure which terminates when calculated gas and liquid pressure drops match. The iterative design procedure is compared with new data for air‐water flow in a smooth tube of 63.5 mm ID and with data available in the literature. For conditions corresponding to small amplitude interfacial waves, the average deviation between predicted and experimental results is 24.3% for the pressure drop and 7.7% for the holdup. For roll wave conditions, the corresponding average deviations are 4.6 and 26.4% for pressure drop and holdup, respectively. These results are substantially better than the predictions obtained using the Lockhart‐Martinelli correlations.
Dynamic response of the carbon dioxide electrode
Authors: Donaldson Terrence L. , Palmer Harvey J.
Published: June 2004

Complex relationships among multiple chemical species during unsteady diffusion and reaction are shown to cause hysteresis, pH dependent response rates, and general nonfirst‐order transient behavior in agreement with common experimental observations. Response improvement by enzymic catalysis of the carbon dioxide hydration reaction also is considered.
A comprehensive experimental investigation of tubular entry flow of viscoelastic fluids: Part III. Unstable flow
Authors: Cable P. J. , Boger D. V.
Published: June 2004

For every viscoelastic fluid studied in the contraction geometry, it was found that increasing the flow rate beyond a certain limit resulted in disturbance to the stable entry flow patterns described in Parts I and II. An examination of the development of the entry flow disturbances was carried out using still and cine photography. Still photographs are presented to illustrate the characteristics of the unstable flow patterns. The time varying nature of the flow has been recorded on a cine film Flow Patterns in Abrupt Entry Flow of Viscoelastic Fluids which is available for loan. Critical condition criteria for the onset of the periodic flow disturbances were obtained in terms of the fundamental fluid properties and are presented and compared with other suggested criteria for the onset of unstable entry flow of viscoelastic fluids.
Feasibility of separation processes in liquid‐liquid solid systems: Free energy and stability analysis
Authors: Jacques Malcolm T. , Hovarongkura A. David , Henry Joseph D.
Published: June 2004

The feasibility of new solid/liquid separation processes, such as solids removal from oil and certain tertiary oil recovery techniques, can be evaluated by a thermodynamic stability analysis of possible liquid‐liquid‐particle configurations. The thermodynamic stability and hence feasibility of two possible liquid‐liquid‐particle separation process is predicted by use of a free energy analysis. Stability is shown to depend primarily on droplet/particle size ratio (n) and three phase contact angle (θ). Stability criteria are presented which can be applied to many particle and liquid separation processes.
Correlation of pure component Gibbs energy. Using UNIFAC group contribution
Authors: Fredenslund Aage , Rasmussen Peter
Published: June 2004

The UNIFAC group contribution method has already proved highly valuable for predicting excess Gibbs energies of liquid mixtures and hence vapor‐liquid equilibria. The solution of groups concept is extended to cover the total Gibbs energy of any system, pure or mixed, relative to a well‐defined standard state. The result is a correlation which is capable of predicting simultaneously pure component vapor pressures and standard Gibbs energies of formation and mixture vapor‐liquid equilibrium compositions. The results presented strongly support the approach and indicate that the method should be further developed.
Effectiveness factors and mass transfer in trickle‐bed reactors
Authors: Herskowitz Mordechay , Carbonell R. G. , Smith J. M.
Published: June 2004

Rates of hydrogenation of α‐methyl styrene were measured at 40.6°C and 1 atm in a recycle, trickle‐bed reactor using a palladium/aluminum oxide catalyst. Data for different hydrogen concentrations in the gas and liquid feed streams suggested that except, at high liquid flow rates, on part of the outer surface of the catalyst the mass transfer limitation was very small, indicating a gas covered type of surface. A procedure was developed for evaluating effectiveness factors for the nonuniform boundary conditions existing when part of the particle surface is covered by gas.
Catalytic removal of sulfur, nitrogen, and oxygen from heavy gas oil
Authors: Furimsky Edward
Published: June 2004

Removal of sulfur, nitrogen, and oxygen from heavy gas oils is affected by the chemical composition of supported molybdate catalysts. Cobalt and nickel, when added to these catalysts, have a promoting effect on these reactions. However, the relative rates always follow the same trend; that is, the hydrodesulfurization is the fastest, followed by hydrodenitrogenation and hydrodeoxygenation.
A thermodynamic approach to heat integration in distillation systems
Authors: Umeda Tomio , Niida Kazuo , Shiroko Katsuo
Published: June 2004

Starting from a conventional distillation system without heat integration, a series of bottlenecks from the viewpoint of energy conservation is sequentially found by a thermodynamic analysis using a heat availability diagram, and modified systems are evolutionally synthesized as the result of debottlenecking. The present approach has made possible a unified interpretation of various energy integrated distillation systems with multieffect columns, intercondensers/interreboilers, heat pumps, etc.
Kinetics and mass transfer in a fluidized packed‐bed: Catalytic hydrogenation of ethylene
Authors: Farrell Robert J. , Ziegler Edward N.
Published: June 2004

The kinetics of ethylene hydrogenation to ethane are studied in a 7.0 cm diameter fluidized packed‐bed reactor. The fixed packing, 1.27 cm nickel on alumina catalyst, is used in conjunction with both −48/+100 mesh alumina and −50/+170 mesh glass inert fluidized particles. Reactant mixture is passed through the reactor at velocities sufficient to fluidize the inerts. Conversions from 0 to 91% are observed over the temperature range 56° to 261°C and flow rate range 10 to 800 cm3/s.

The mass transfer coefficient and reaction rate constant are simultaneously evaluated from integral conversion data. The mass transfer coefficient between the interstitially fluidized bed and the catalyst surface is correlated in dimensionless form as

Nsh = 0.77 NRe0.418 NSc1/3

The correlation is significant at the 95% confidence level that is, r = 0.59, p′ > 0.

Predictions of conversion using both the mass transfer coefficient correlation and a Langmuir‐Rideal reaction expression are in good agreement with experimental data. The effects of contact time and catalyst diameter on conversion are also presented. Film diffusion influences become limiting at temperatures above 100°C at the velocities studied. Diffusional resistances were found to be important at Reynolds numbers below 100, at 186°C. No significant difference in reaction rate was found between fluidized alumina and glass inert particles under comparable operating conditions.
Characteristics of macromolecular gel layer formed on ultrafiltration tubular membrane
Authors: Nakao Shin‐Ichi , Nomura Tsuyoshi , Kimura Shoji
Published: June 2004

Characteristics of the gel layer were investigated by direct measurement of its concentration treating polyvinylalcohol and ovalbumin aqueous solutions, using cellulose acetate tubular ultrafiltration membranes. The concentration of the gel layer was not constant but a function of bulk concentration and feed velocity. The mass transfer coefficient obtained agreed with Deissler correlation. There was a definite correlation between the resistance of the gel layer and its concentration.
An equation of state for polyatomic fluids
Authors: Mohanty Kishore K. , Ted Davis H.
Published: June 2004

An equation of state has been developed for convex nonspherical particles with nonpolar and multipolar forces. The effects of nonsphericity and multipolarity on phase behavior are characterized by a geometric shape parameter and an energy fluctuation parameter, respectively. The equation performs for real fluids better than the Van der Waals equation and as well as the Redlich‐Kwong and Peng‐Robinson equations.
Advances in deep bed filtration
Authors: Tien Chi , Payatakes Alkiviades C.
Published: June 2004

The main problems which are relevant to a fundamental understanding of deep bed filtration are the nature of and the conditions leading to the retention of particles throughout a filter bed, the change of the filter media structure due to deposition, and its effect on filter performance. The purpose of this review is to discuss in a systematic manner the more recent advances in the investigation of all these problems. A reasonably complete understanding of the pertinent phenomena is essential for the establishment of a comprehensive deep bed filtration theory which can be used as a basis of rational design.
Heat transfer with stratified gas‐liquid flow
Authors: James Davis E. , Cheremisinoff Nicholas P. , Guzy Christopher J.
Published: June 2004

This article presents a method for predicting local Nusselt numbers for heat transfer to a stratified gas‐liquid flow for turbulent liquid/turbulent gas conditions. A mathematical model based on the analogy between momentum transfer and heat transfer is developed and tested, using heat transfer and fluid mechanics data taken for air/water flow in a 63.5 mm I.D. tube. The fluid mechanics parameters required for the prediction of the heat transfer characteristics are obtained in the manner outlined elsewhere. Liquid phase Nusselt numbers predicted by the analogy are shown to be in agreement with experimental results for large and small amplitude wavy interfacial conditions. The circumferential average gas phase Nusselt numbers are in rough agreement with the Dittus‐Boelter equation for single phase flow based on flow through a conduit of irregular shape. There is a tendency for the average gas phase Nusselt numbers to scatter about predicted values because of the effects of splashing and droplet deposition on the tube wall in the vicinity of the gas‐liquid interface.
The influence of the freeboard region in a fluidized bed catalytic cracking regenerator
Authors: De Lasa Hugo I. , Grace John R.
Published: June 2004

A model is developed for a fluidized bed reactor with the dense phase region treated by conventional two‐phase models. Conversion in the freeboard is obtained based on particle trajectories predicted from drag considerations. The model is applied to an industrial‐scale catalytic cracking regenerator. It is shown that the freeboard region can have an important influence on the overall conversion in the unit.
Computation of phase and chemical equilibrium: Part II. Phase‐splitting
Authors: Gautam Rajeev , Seider Warren D.
Published: June 2004

A phase‐splitting algorithm is coupled with the Rand method to improve its efficiency and reliability when the phase distribution is unknown at equilibrium. The coupled algorithm works well to give phase‐splits in the metastable region where most stability tests fail. Exhaustive tests show fine performance in the region near liquid‐liquid phase envelopes for systems with at least one partially miscible binary pair.
Computation of phase and chemical equilibrium: Part III. Electrolytic solutions
Authors: Gautam Rajeev , Seider Warren D.
Published: June 2004

Methods for estimating the properties of electrolytic solutions are reviewed, with emphasis on molecule‐molecule, molecule‐ion, and ion‐ion interactions. The algorithms of Parts I and II, to search for global minimum in Gibbs free energy, are extended to handle electrolytes and compared with an algorithm using k‐values. Results are presented for SO2‐H2O and H2S‐NH3‐H2O systems and agree with experimental values.
Diffusion of gases through surfactant films: Interfacial resistance to mass transfer
Authors: Nguyen Ly L.‐A. , Carbonell R. G. , Mc Coy B. J.
Published: June 2004

A model is proposed for mass transfer of gases across surface‐active films and into an aqueous phase. The interfacial region (1) obeys local equilibrium conditions, (2) has a capacity for the dissolved gases greater than the solubility in water, and (3) has a diffusion coefficient three orders of magnitude less than for that in water. The model is solved for and compared with three different experiments: the transient diffusion through monomolecular films into quiescent liquids studied by Plevan and Quinn (1966), the gas absorption through surfactant films into falling liquid films investigated by Emmert and Pigford (1954), and the frequency response of concentration pulses in surfactant films reported by Whitaker and Pigford (1966). The model consistently describes these experiments previously explained by three different models that either ignored the capacitance of the film or assumed local non‐equilibrium.
Axial dispersion through tube constrictions
Authors: Weaver David W. , Ultman James S.
Published: June 2004

Tracer gas dispersion was measured for laminar flow through three different tube constrictions, at orifice Reynolds numbers between 10 and 5000 and Schmidt numbers of 0.213 and 0.769. Each constriction generates a confined jet which significantly enhances axial dispersion at intermediate Reynolds numbers ranging from 100 to 1000.
Kinetics of non‐isothermal sorption in molecular sieve crystals
Authors: Ruthven Douglas M. , Lee Lap‐Keung , Yucel Hayrettin
Published: June 2004

A mathematical model is developed to describe non‐isothermal sorption kinetics and used to interpret experimental uptake curves for CO2 in 4A zeolite and for CO2 and in C5H12 in 5A zeolite. The model assumes that the dominant mass transfer resistance is intracrystalline diffusion while the major resistance to heat transfer is the external heat transfer between the adsorbent sample and the surroundings. It gives a good representation of the kinetic behavior over a wide range of conditions. Both the extreme cases of isothermal diffusion and complete heat transfer control are demonstrated experimentally. Intermediate situations, in which the uptake rate is controlled by the combined effects of diffusion and heat transfer, are demonstrated as well. The parameters derived from the model are consistent, reproducible, and agree well with a priori estimates. The model provides a useful theoretical basis for the analysis of rapid sorption processes for which the non‐isothermal approximation is invalid.
Cluster diffusion in liquids
Authors: Cussler E. L.
Published: June 2004

Diffusion in concentrated, non‐ideal liquid solutions may take place not only through motion of single molecules but also through movement of groups of molecules, or “clusters.” Analyzing this cluster diffusion leads to predictions that the diffusion coefficient can vary with the square root of the usual activity corrections to diffusion. These predictions seem consistent with experiments, particularly in highly non‐ideal solutions.
Studies in the synthesis of control structures for chemical processes: Part I: Formulation of the problem. Process decomposition and the classification of the control tasks. Analysis of the optimizing control structures
Authors: Morari Manfred , Arkun Yaman , Stephanopoulos George
Published: June 2004

Part I of this series presents a unified formulation of the problem of synthesizing control structures for chemical processes. The formulation is rigorous and free of engineering heuristics, providing the framework for generalizations and further analytical developments on this important problem.

Decomposition is the underlying, guiding principle, leading to the classification of the control objectives (regulation, optimization) and the partitioning of the process for the practical implementation of the control structures. Within the framework of hierarchical control and multi‐level optimization theory, mathematical measures have been developed to guide the decomposition of the control tasks and the partitioning of the process. Consequently, the extent and the purpose of the regulatory and optimizing control objectives for a given plant are well defined, and alternative control structures can be generated for the designer's analysis and screening.

In addition, in this first part we examine the features of various optimizing control strategies (feedforward, feedback; centralized, decentralized) and develop methods for their generation and selective screening. Application of all these principles is illustrated on an integrated chemical plant that offers enough variety and complexity to allow conclusions about a real‐life situation.
Stochastic simulation of the motion, breakup and stranding of oil ganglia in water‐wet granular porous media during immiscible displacement
Authors: Ng K. M. , Payatakes A. C.
Published: June 2004

The problem of immiscible displacement of oil ganglia arises in connection with oil bank formation and attrition during enhanced oil recovery with flooding. A stochastic simulation method is developed here, which enables prediction of the fate of solitary ganglia during immiscible displacement in water‐wet unconsolidated granular porous media. This method takes into account the local topology of the porous medium; the initial size, shape and orientation of the oil ganglion and the capillary number. For each ganglion size, hundreds of realizations are performed with random ganglion shapes for a 100 × 200 sandpack. These results are averaged to obtain probabilities of mobilization, breakup and stranding as functions of capillary number and ganglion size. Axial and lateral dispersion coefficients are obtained as functions of the average ganglion velocity. The results from the solitary ganglion analysis can be used with the ganglion population balance equations developed in a companion publication (Payatakes, Ng and Flumerfelt, 1980) to study the dynamics of oil bank formation.
Effect of sludge funneling in gravity thickeners
Authors: Dixon D. Christopher
Published: June 2004

The performances of cylindrical and conical thickeners are compared by means of calculations, using published data on the properties of a suspension. Experimental data on the operation of cylindrical thickeners indicate that sludge funneling at the bottom of such thickeners has a large effect and is a possible cause of observed discrepancies between theory and experiment.
Conjugate unsteady heat transfer from a droplet in creeping flow
Authors: Abramzon Boris , Borde Irene
Published: June 2004

The phenomenon of unsteady heat transfer from a spherical droplet or solid particle moving slowly in a different fluid is analyzed, for the case in which the thermal resistances of the dispersed and continuous phases are comparable. The effect of the Peclet number (over the range 0 ⩽ Pe ⩽ 1,000) and of the internal circulation of the droplet on the development of temperature fields is investigated. The energy equations for the interior and exterior of the droplet are solved by the finite‐difference method of alternating directions. The results are compared with a number of previously published approximate models.