bluuebunny/crossref_metadata_2025_split huggingface dataset:
Laminar flow in the entrance region of a cylindrical tube: Part I. Newtonian fluids
Authors: Sylvester N. D. , Rosen S. L. 
Published: June 2004

AbstractPressure losses at the sharp edged entrance to a cylindrical tube were investigated for glycerine‐water solutions over a Reynolds number range of 6 to 2,000.For the experimental area contraction ratio of 0.0156, the Hagenbach (K) and Couette (K') coefficients are 2.4 and 295, respectively. Comparison with limited previous work shows that both coefficients increase with the area contraction ratio β over range 0<β<0.162.
Effect of fluid viscosity on combined free forced convection flow phenomena in vertical pipes
Authors: Greene Howard L. , Scheele George F. 
Published: June 2004

AbstractDistorted velocity and temperature profiles are measured at low Reynolds numbers for upflow constant flux heating of water and two viscous Newtonian sucrose solutions in a long vertical pipe. HeatedL/D's ranged from 29 to 251. Experimental profiles atL/D= 251 show general agreement with the fully developed profile theory based on natural convection effects, but additional profile distortion, attributed at least in part to radial viscosity variation with temperature, is observed even with water.Natural convection induced transition to disturbed flow occurs for all three liquids as the ratio of heat input to flow rate is increased. The transition process involves the growth in amplitude and radial spread of initially small disturbances. Transition conditions and the dimensionless radial location of the first detectable instability are related to features of the distorted flow fields.
Compressibilities and virial coefficients for methane, ethylene, and their mixtures
Authors: Lee Roy C. , Edmister Wayne C. 
Published: June 2004

AbstractA Burnett type of apparatus was built for 12,000 lb./sq.in. pressure and temperatures of 25° to 100°C. Isothermal expansions were run on methane, ethylene, and four binary mixtures at 25°, 50°, and 75°C., and compressibility factors were derived from the pressure ratio observations.From the experimental data, second and third virial coefficients were derived by two techniques, that is, the slope‐intercept and the multiple regressions curve‐fit of the data by the density‐series virial equation. A comparison of these virial coefficients with those from the different empirical equations of state indicates areas of needed improvements in these equations. Second virial cross coefficients were also obtained.
Numerical simulation of convective diffusion in blood flowing in a channel with a steady, three‐dimensional velocity field
Authors: Weissman M. H. , Hung T. K. 
Published: June 2004

AbstractA numerical study was performed to investigate improvement in mass transfer rates obtainable by introduction of secondary convection into a proposed membrane blood oxygenator. The three‐dimensional Navier‐Stokes equations were solved numerically for the velocity field in channel and the results used in the numerical solution for the local Po2 in the oxygenator. The convective diffusion equation solved is nonlinear, in addition to being three‐dimensional, because of the presence of red cell oxygen sinks.The convection introduced was generated by moving one wall of the blood flow channel laterally to the main flow. Decreases in blood side film resistance up to 5 × 104 were predicted. In the presence of moderate to strong convection, the limiting factor on oxygenation rate is imposed by the membrane situated between blood and gas phases. It appears that a considerable decrease in required blood priming volume would be possible if the method discussed here were implemented.
Dynamic effects of temperature control tray location in distillation columns
Authors: Shunta J. P. , Luyben W. L. 
Published: June 2004

AbstractThis paper presents the results of theoretical and experimental studies of the dynamic effects of varying the location of the temperature control tray in a distillation column. The binary methanol‐water system was studied in a 24‐tray, 8‐in. I.D. column with reflux manipulated to hold the temperature on various trays in the rectifying section of the column.The ultimate gain and ultimate frequency of the temperature feedback control loops were found to decrease as the temperature control tray was moved down the column away from the top. This confirmed the qualitative statements made by many workers and the quantitative work recently reported by Beaverstock.The process natural frequency (or breakpoint frequency) was found, unexpectedly, to increase somewhat as the temperature control tray was moved down the column. This meant that the open‐loop response of tray liquid composition to reflux flow changes was slightly slower for trays near the top of the column. Because of the increasing purity near the top, adjacent trays differed little in composition and the slope of the equilibrium line was flatter. Both contributed to slower dynamic response.In developing a theoretical model for the real system studied, the linear model and solution techniques of Lamb, Pigford, and Rippin and were extended to include nonequimolal overflow effects.
Transient response of a tubular reactor to upsets in flow rate
Authors: Ramaswamy Venkatasub , Stermole F. J. , McKinstry K. A. 
Published: June 2004

AbstractThis study concerns the transient response of a tubular reactor in which a second‐order reaction takes place under isothermal conditions. The reaction studied was the saponification of methyl acetate with sodium hydroxide. Experimental data were obtained in a tubular reactor for flow upsets.Theoretical models using residence time distribution (RTD) techniques have been developed. The study was conducted at 36°C. The reactor was a 13‐ft. long, ¼‐in. diam. copper tube in the form of a spiral with a volume of 110 cc.The agreement obtained between the experimental data and the RTD model predictions was good, verifying that this model is satisfactory for simulation of tubular reactor dynamics. Backmixing was observed in the reactor. This nonideality was accounted for empirically in the RTD model, since backmixing was observed to be mainly a function of flow rate.
Reaction equilibrium of real fluid mixtures
Authors: Gaggioli Richard A. , Nierode Dale E. 
Published: June 2004

AbstractA theoretical approach to equilibrium calculations for homogeneous real fluid mixtures is presented. The overall approach is developed for, although not theoretically restricted to, a corresponding states equation of state, z(Tr, pr). The method is applied to the gaseous ammonia synthesis data of Larson and Dodge. Excellent agreement was attained with the data. Quite significant improvement was observed over the ideal gas and ideal solutions approximations.
A thermodynamic consistency test for adsorption from binary liquid mixtures on solids
Authors: Sircar S. , Myers A. L. 
Published: June 2004

AbstractA thermodynamic consistency test for adsorption from binary liquid mixtures is derived using the Gibbs equation for adsorption. Adsorption data for the liquid mixture pairs A‐B, A‐C, and B‐C on the same adsorbent must be thermodynamically consistent. The consistency test is applied to experimental data for adsorption from the binary liquid mixtures benzene‐cyclohexane, benzene‐n‐heptane and cyclohexane‐n‐heptane on silica gel at 30°C.
A theoretical study of a controlled‐cycled stirred‐tank reactor
Authors: Codell R. B. , Engel A. J. 
Published: June 2004

AbstractA mathematical study was carried out for a stirred reactor in which the feed and product streams were periodically interrupted. The cycled reactor proved superior to a continuous stirred‐tank reactor for first‐ and second‐order reactions, and surpassed a plug‐flow reactor for those cases in which the reaction rate passes through a maximum, such as autocatalytic and exothermic adiabatic reactions. Temperature‐programmed cycled reactors were also studied, but appeared to have little advantage over conventional reactors.
Simultaneous nonisothermal noncatalytic solid‐gas reactions
Authors: Wen C. Y. , Wei L. Y. 
Published: June 2004

AbstractThe kinetics of simultaneous, noncatalytic solid‐gas reaction systems has been analyzed in terms of the selectivity and effectiveness factor, based on the unreacted core shrinking model. The reaction systems discussed include the first‐order independent, parallel, and consecutive reactions with the simultaneous influences of heat and mass transfer. The effects of various chemical and transport properties on the stability, selectivity, and effectiveness factor of the system are discussed. The pseudosteady state approximation is employed to reduce the mathematical difficulties.
Analysis of flow choking of two‐phase, one‐component mixtures
Authors: Klingebiel W. J. , Moulton R. W. 
Published: June 2004

AbstractThe nature of flow choking has been studied as steam‐water mixtures are passed through a tube with ever increasing pressure gradient. Choked flow for two‐phase, one‐component mixtures has been characterized with a separated flow model as resulting from maximization of the ratio of gas to liquid velocities, or slip ratio. Slip ratios at choking were measured and found to increase from 1.2 to 5.0 at 30 lb./sq.in. exit plane pressure with decrease in quality from 0.95 to 0.02. Separated models predict either 9.3 or 28.4 with no quality dependence. The difference is attributed to liquid entrainment. Flow regimes were observed to vary from purely entrained to annular entrained to slug entrained as quality decreased. Normal shock waves were observed in the free jet at qualities above 0.25. Choking flow rates were predicted with an average error of less than 2% with a stagnation energy balance model using an empirically developed slip ratio relation corrected for entrainment.
Adaptive control of a chemical process system
Authors: Ahlgren Theodore D. , Stevens William F. 
Published: June 2004

AbstractModification of parameters in the conventional controller equation usually is necessitated by uncontrollable process parameter drifts which occur during the operation of the large scale continuous processes typically found in the chemical industry. To this end, a normalized version of the model reference adaptive control system, including suitable procedures for adjusting the adaptive loop gains, was developed and demonstrated to provide excellent adaptive performance for a single concentration control loop for a simulated stirred‐tank chemical reactor. The three constants in a conventional PID controller were simultaneously adjusted to accomplish this adaptation. Equally excellent adaptive performance was achieved in an interacting control loop scheme simulated by control of both the concentration and the temperature in the same stirred‐tank reactor. In both cases adaptation was achieved in a time interval which was sufficiently short to make this method of adaptive control feasible for use in a real processing situation. Models needed for implementation of the model reference adaptive control scheme were easily developed. In a real application these models could be easily developed from studies which could take place during prestartup or early operations of the process; hence no a priori knowledge would be required. A wide range of adaptive loop gains was demonstrated to provide a stable overall control system. A high degree of stability was demonstrated for the overall system despite the initiation of large extraneous load upsets occurring during the operation of the adaptive control system.The method presented has not been rigorously proven to be applicable to every real control problem requiring adaptive control. However, the method was demonstrated to be highly effective over a wide range of required controller adjustments in cases similar to those encountered in large continuous processes. Thus the method merits serious consideration for possible implementation whenever adaptive control is required.
Heat and mass transfer in the vicinity of the triple interline of a meniscus
Authors: Wayner P. C. , Coccio C. L. 
Published: June 2004

AbstractEffective experimental and theoretical techniques for studying the heat transfer characteristics of a stationary evaporating meniscus formed on a flat plate immersed in a pool of liquid were developed. Integral heat transfer data were obtained for the four systems: 304 stainless steel‐water, 6061 aluminum‐water, 304 stainless steel‐methanol, and 6061 aluminum‐methanol. High rates of heat transfer were obtained in the triple interline region with a stable meniscus. Detailed descriptions of the heat flux and temperature field were obtained for the stainless steel‐water and stainless steel‐methanol systems. The effect of the evaporation coefficient on the heat flux distribution was evaluated. The heat transfer process in the interline region proved to be more efficient than a simple conduction process in an evaporating liquid meniscus.
Backmixing in multistage agitated contactors‐‐‐a correlation
Authors: Haug H. F. 
Published: June 2004

AbstractA generalized correlation is presented for the backmix ratio in multistage agitated contactors. The backmix ratio is shown to be a function of the ratio of impeller tip speed to superficial flow velocity, and of the column configuration and impeller design. For single‐phase flow and for the continuous phase in two‐phase flow, the following expression is recommended:
Calculation of dispersion coefficients by means of moments
Authors: Horn F. J. M. 
Published: June 2004

AbstractThe problem of evaluating the coefficient of dispersion in a general linear two‐component chromatographic system is equivalent to a steady state source problem in multidimensional Euclidean space. The equivalence of the two physical problems provides an intuitive insight into the contributions of different transport processes to dispersion. For a wide class of systems the dispersion coefficient can be expressed as the maximum of a functional. This can be utilized in the numerical evaluation of dispersion coefficients and in the application of perturbation techniques.
The calculation of unsteady state multicomponent distillation using partial differential equations
Authors: Osborne Adam 
Published: June 2004

AbstractA method is presented for calculating unsteady state multicomponent distillation using partial differential equations. The equations are solved by treating them as continuous in theoretical stage direction and stepped in time. Although some restrictions were placed on the problems actually solved, the method itself is not restricted by number of trays, number of components, number, type or combination of upsets, or by the thermodynamics of the system, and the method readily lends itself to hybrid computer solution.
Control of distillation columns with sharp temperature profiles
Authors: Luyben W. L. 
Published: June 2004

AbstractTemperature control problems are frequently encountered in distillation columns that, as a result of high purity products and an easy separation, have large temperature changes over a few trays. The describing function technique is used in this paper to analyze the stability of this type of column in which a nonlinear feedback control loop for column temperature control manipulates vapor boilup.The cycling usually experienced in these systems is shown to be unavoidable in many cases because the process transfer function has such a high gain that it acts like an on‐off switch. The process also displays nonlinear dynamics: system time constants vary with the magnitude of change in vapor boilup.To overcome these difficulties an adaptive, nonlinear feedback controller is proposed that keeps the loop in a small‐amplitude limit cycle by adaptively changing controller gain. The system is evaluated by digital simulation of a nonlinear model of the column.
Kinetics of noncatalytic, nonisothermal, gas‐solid reactions: Hydrofluorination of uranium dioxide
Authors: Costa Eduardo C. , Smith J. M. 
Published: June 2004

AbstractA single‐pellet, stirred‐tank reactor was used to measure temperatures, compositions, and rates of reaction for the hydrofluorination of UO2.14 at atmospheric pressure. By correlating the rate with conditions at the reacting surface, the activation energy of the first‐order reaction was found to be 6,070 cal./g.‐mole.Since the product forms an unreactive layer around the core of UO2.14, and since the heat of reaction is high, significant concentration and temperature differences develop between the gas phase and the reaction surface. The temperature and rate data were used to calculate the effective diffusivity and thermal conductivity of the product layer under reaction conditions.An adaptation of a pseudosteady state method was developed for predicting the conversion and temperature history of a pellet. Using rate constants for reaction and mass and energy transfer derived from the experimental data, this method gave good results. Predictions with estimated rate constants were poor, indicating that an accurate value was necessary for the effective diffusivity in the product layer.
Slow flow of a non‐newtonian fluid past a droplet
Authors: Wagner Martin G. , Slattery John C. 
Published: June 2004

AbstractThe problem of slow flow past a droplet is considered where both materials may be represented as fluids of grade 3 and where the outer fluid is of infinite extent. Both non‐Newtonian and inertial effects are included in the analysis. A double perturbation technique and the method of matched asymptotic expansions are employed to obtain solutions to the equation of motion.Solutions, in the form of Legendre polynomial series, are obtained for the stream function (both outside and inside the droplet), for the drag force exerted on the droplet, and for the shape of the droplet.The results obtained are in complete agreement with those obtained by other workers for the flow of a Newtonian fluid past a Newtonian droplet and for the flow of a fluid of grade 3 past a solid sphere. Droplet shape predictions are in qualitative agreement with experimentally observed shapes.
Computerized catalytic kinetics: A useful extension of the method of Wei and Prater
Authors: Lombardo E. A. , Hall W. Keith 
Published: June 2004

AbstractAn extension of the method of Wei and Prater has been devised for determining the relative rate constants for an isothermal, first‐order, reversible, three‐component system, namely, the catalyzed isothermal isomerization of n‐butenes. The new method reduces the required work to one experiment.
Heat, Mass, and momentum transfer analogies for the fully developed turbulent flow of power law fluids in circular tubes
Authors: Krantz W. B. , Wasan D. T. 
Published: June 2004

AbstractA new correlation is presented to describe heat and mass transfer at large Prandtl or Schmidt numbers to power law fluids in fully developed turbulent flow in a pipe. The resulting expression for the Stanton number differs from earlier semiempirical correlations in that it is based on a continuous eddy viscosity distribution from the wall to the center of the pipe and contains no adjustable parameters to be determined from heat transfer data. Nusselt numbers determined by the new correlation are in excellent agreement with data on heat transfer to both pseudoplastic and dilatant fluids.
Enzyme kinetics and engineering
Authors: Carbonell R. G. , Kostin M. D. 
Published: June 2004

AbstractThis review article surveys representative literature on enzyme kinetics and engineering published form January 1969 to August 1971. Particlar attention is given to methods of attaching enzymes to solid supports, and to factors, such as pH and temperature, which affect the reaction rate. Recent theories accounting for the high selectivity and high rate of enzyme reactions, calculations taking into consideration the effects of diffusion, methods for analysing kinitic data, and proposals for enzyme reactors are evaluated. Also reviewed are recent methods for extraction of enzymes from cells, procedures for synthesizing enzymes artificailly, and techniques for isolating and purifying enzymes.
The activated calcium sulfate‐water vapor sorption therm
Authors: Jury Stanley H. , Pollock Mark A. , Mattern James W. 
Published: June 2004

AbstractThe sorption isotherms are reported for the β‐soluble anhydrite form of calcium sulfate (Drierite) exposed to moist air at one atmosphere total pressure and 90, 100, 125, 150, 175, and 200°F. A concentration‐temperature coordinate has been identified which when plotted against the amount sorbed caused all isotherms to collapse into a single sorption therm. The latter has been fit by a three‐term expression based on a combination of sorption theories. A graphical comparison is made between a curve calculated from the analytical expression and actual experimental datum points.Curve fitting was done by machine and involved minimizing the square of the deviations. Maximum deviations up to 4% are experienced in the high range. In the low range these tend to increase but so do the experimental errors.
Turbulent diffusion in the core of a pipe with uniform transverse flow at the walls
Authors: Suneja S. K. , Shea R. H. , Wasan D. T. 
Published: June 2004

AbstractAn analysis of point source turbulent diffusion of a gaseous tracer in the core of a circular straight porous pipe with uniform transverse flow at the walls is presented. Time averaged concentration distributions were measured at four distances downstream from a point source located at the axis of a fully developed turbulent flow of air in a 6‐in. pipe. Experiments were run at average velocities between 4.36 and 23.0 ft./sec. (corresponding to Reynolds numbers 12,000 to 66,000) with injection velocities ranging from 0 to 0.170 ft./sec. and suction velocities from 0 to 0.048 ft./sec. The highest injection rate corresponded to 58% by volume of the main stream. Good agreement is obtained between the expeimental and the calculated concentration profiles.The present study shows that the plume width of the disperising tracer is considerably affected by the transverse flow. It also shows that the eddy diffusivity in the pipe core and the radial mass flux increase with fluid injection and decrease with suction through the pipe walls. Also, for increasing values of aspect ratio, they increase in the case of injection and decrease in the case of fluid suction.
Observations of early turbulence in the pipe flow of drag reducing polymer solutions
Authors: Forame P. C. , Hansen R. J. , Little R. C. 
Published: June 2004

AbstractEarly turbulence has for the first time been observed in the flow of very dilute polymer solutions in tubes larger than capillary size. Flow rate‐wall shear stress measurements were conducted in 0.553 and 0.660 cm. diameter pipes. Polyethylene oxide samples of two molecular weights were employed, dissolved in water‐glycerine mixtures with viscosities ranging from 0.0261 to 0.160 poise. The flow rate‐wall shear stress relationship for these solutions corresponded to Poiseuille's Law below a well‐defined onset wall shear stress, at which the Reynolds number was less than the transition value for Newtonian fluids. As the flow rate was increased from the onset condition, however, the wall shear stress became progessively larger than that predicted by the Poiseuille relationship. The onset wall shear stress for the phenomenon increased linearly with solvent viscosity. Its relationship to polymer concentration was dependent on the solvent viscosity. An explanation for early turbulence is suggested on the basis of these results, and the relationship of the phenomenon to turbulent flow drag reduction is discussed.