bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transient diffusivity measurements in catalyst pellets with two zones of differing diffusivities
Authors: Chou Tai‐Sheng , Hegedus L. Louis 
Published: June 2004

AbstractTransient 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.
SCP production on C1 compounds
Authors: Papoutsakis Eleftherios , Lim Henry C. , Tsao George T. 
Published: June 2004

AbstractGiven 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

AbstractDraw 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

AbstractThe 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

AbstractExperimental 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

AbstractPhotographs 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

AbstractFeedback 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

AbstractAn 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

AbstractPerturbed‐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

AbstractThe 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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractThis 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.
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

AbstractFor 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

AbstractThe 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

AbstractThe 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

AbstractRates 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

AbstractRemoval 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

AbstractStarting 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

AbstractThe 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 asNsh = 0.77 NRe0.418 NSc1/3The 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

AbstractCharacteristics 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

AbstractAn 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

AbstractThe 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

AbstractThis 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.