bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimization of a continuous through‐circulation dryer
Authors: Thygeson J. R. , Grossmann E. D. 
Published: June 2004

AbstractA mathematical model of a through‐circulation packed bed dryer is presented in this paper. The semitheoretical model treats the case of constant rate drying in a deep bed of granular solids under initially uniform drying conditions. Experimental data for drying in superheated steam, mixtures of superheated steam and air, and air alone showed good agreement with predictions of the model.Based on the model, a static optimization method is developed for optimal operation of a continuous through‐circulation dryer subject to the inequality constraints of maximum permissible air‐horsepower per unit bed area and maximum permissible local final moisture content in the bed. A nonlinear capacity function is defined in terms of the independent drying variables and is maximized under the above nonlinear restraints.
High velocity compressible viscous flow
Authors: Schwartzberg Henry G. , Gurevich Michael 
Published: June 2004

AbstractPressure drops were measured for the high velocity isothermal viscous flow of steam in circular tubes. For the velocities tested, up to 0.48 times the isothermal sonic velocity, these flows obeyed the following equation with an average deviation of 2.4%.

This equation differs from the Poiseuille‐Meyer equation commonly used to correlate isothermal viscous flow in that it includes the term (NRe/3) In (P1/P2) which accounts for the change in momentum caused by expansion. In deriving this equation, the mean velocity, mean squared velocity, and wall shear stress were obtained from the parabolic velocity distribution for normal viscous flow. The velocity profile should flatten as the isothermal Mach number increases, and it is therefore anticipated that somewhere above the range tested the equation will no longer prove applicable. Variants of the equation, which take into account the flattening of the velocity profile in the range tested, did not fit the experimental data quite as well.
A new technique for chemical kinetics at high pressures
Authors: Grieger R. A. , Eckert C. A. 
Published: June 2004

AbstractInformation about the transition state of a chemical reaction is quite useful for the determination of mechanisms and for design of solvents for the reaction. High pressure kinetic studies, if sufficiently accurate, provide the required data. This work reports a new technique developed for measuring rates of chemical reactions in solution at high pressure. This method involves in situ mixing of reactants under pressure and direct sampling for analysis, eliminating large errors of temperature equilibration and time measurement inherent in existing techniques, and thus yielding more accurate results. Experimental results for the Diels‐Alder reaction of isoprene and maleic anhydride are reported at pressures up to more than 6,000 atm.
The periodic viscous sublayer in turbulent flow
Authors: Meek Ronald L. , Baer Alva D. 
Published: June 2004

AbstractThe model of the fluctuating viscous sublayer proposed by Einstein and Li was modified by treating some of the objections to the original formulation without greatly altering the essential simplicity of the concept. The applicability of this model to the description of the important features of turbulent flow and heat transfer in ducts and of the Toms phenomenon was evaluated by comparison of predictions of the model with experimental measurements. The mean period for growth and decay of the sublayer and the magnitudes of the wall‐pressure fluctuations and wall‐temperature fluctuations were compared for the flow of air and liquids. Quantitative spatial features of the periodic sublayer, that is, minimum and maximum sublayer thickness and patch size in the directions normal and parallel to the flow direction, were determined.
Experimental determinations of several thermal properties of a mixture containing 51 mole percent Propane in Methane
Authors: Yesavage V. F. , Katz D. L. , Powers J. E. 
Published: June 2004

AbstractResults of calorimetric determinations are reported for a mixture containing approximately 51 mole % propane in methane. Measurements were made with both isobaric and throttling flow calorimeters in the liquid, critical, gaseous, and two‐phase regions in the temperature range from −250° to +300°F. at pressures of between 100 and 2,000 lb./sq. in. abs. Tables of experimental values of heat capacity, Joule‐Thomson coefficient, and isothermal throttling coefficient are presented, and the values of Cp and ϕ are summarized on parametric plots.Experimental values of enthalpy differences within the two‐phase region determined under both isobaric and isothermal conditions are also reported together with the experimentally determined phase boundary data. A skeleton enthalpy table is presented which is based almost entirely on experimental data obtained in this investigation. Comparisons are made with other published calorimetric data and with calculations based on PVT data.
Optimal feedforward control of concurrent tubular reactors
Authors: Bertran David R. , Chang Kun S. 
Published: June 2004

AbstractOptimal control of concurrent nonlinear tubular reactors for complex reaction system is studied. The jacket side temperature is allowed to vary along the reactor length and with time. The optimal control possesses feedforward component only, and the nonlinear gain may be precomputed. For a Denbigh type of reaction system, if the heat generation is negligible, the control temperature is insensitive to feed concentration variations. With heat generation effect present, the optimal control is time dependent, and the nonlinear feedforward gain is obtained. The gain may be approximated by a linear function to construct a simple linear feedforward control loop which contains a synchronized time delay.
Mixing in viscous liquids
Authors: Coyle C. K. , Hirschland H. E. , Michel B. J. , Oldshue J. Y. 
Published: June 2004

AbstractDetailed data are reported for blend time and turnover time with a 17‐in. impeller operating in an 18‐in. diameter tank. Above 1,500 centipoises, viscosity had no effect on blend time at constant speed. Blend time was inversely proportional to speed.The inner flight of a helical impeller is of value when blending pseudoplastic fluids but has no effect on blend time with Newtonian fluids. The ratio of blend time to turnover time is given, as well as the effect of several different helical impeller geometry variables.
Optimal probability partial control of linear inventory systems
Authors: Kim S. M. , Wilde Douglass J. 
Published: June 2004

AbstractMost processes have more storage levels to control than there are production rates for changing inventories, a situation known as partial controllability. Necessary and sufficient conditions under which all levels can be held within predetermined limits are presented. A control law maximizing the probability of satisfactory operation is developed, together with the computational steps required for its implementation. A simple numerical example is given.
The effect on conversion of flow rate variations in a heterogeneous catalytic reactor
Authors: Denis G. H. , Kabel R. L. 
Published: June 2004

AbstractThe unsteady state behavior of a tubular heterogeneous catalytic reactor, in which significant adsorption effects occur, has been investigated theoretically and experimentally. Transient responses of conversion to step increases and decreases of flow rate as well as to periodic variations in flow rate are considered. A simplified procedure for anticipating gross effects in cyclic processes is suggested.
Effect of fouling on stability of adiabatic packed bed reactors
Authors: Ervin Michael A. , Luss Dan 
Published: June 2004

AbstractThe effect of catalyst fouling on the stability and operation of adiabatic packed bed reactors was investigated for two poisoning mechanisms. The effect of fouling was found to be most predominant for packed beds in which nonunique pseudo steady states can exist. Fouling may cause the reactor to misbehave suddenly, with a violent temperature rise, after a long period of pacific operation.
Pore‐diffusion Mechanisms during vapor‐phase adsorption
Authors: Nemeth Edward J. , Stuart Edward B. 
Published: June 2004

AbstractThe mechanism of diffusion in an absorbent pore was studied by applying adsorption rate data to the Damköhler equation. Most of the data were taken in the multimolecular region of the nitrogen‐silica gel adsorption isotherm. Vapor‐phase and adsorbed‐phase contributions to the total transport were separated. Vapor‐phase transport increased with temperature and was most dominant at relative pressures of 0.4 to 0.6. Adsorbed‐phase diffusivities were of the order of 10−2 — 10−3 sq. cm./sec. and showed some dependence on the amount adsorbed at surface coverages greater than 1.5 molecular layers.
Photodecomposition kinetics of formic acid in aqueous solution
Authors: Matsuura Takeshi , Smith J. M. 
Published: June 2004

AbstractThe photodecomposition of aqueous solutions of formic acid was studied as a model reaction for removing organic pollutants from water. The process was carried out in a tubular‐flow reactor, operated continuously. The cylindrical reactor was irradiated from the outside by placing the cylindrical lamp and the reactor at the foci of an elliptical reflector. Measurements made at differential operating conditions permitted calculation of rates of reaction as a function of formic acid concentration and light intensity for the temperature range 25° to 60°C. Carbon dioxide and carbon monoxide were the only observed products of the decomposition.The rate was first order in absorbed light intensity and between zero and first order in formic acid. These results correspond to a combination of chain and non‐chain kinetics occurring simultaneously. Rate constant ratios and quantum yields were calculated from the data and the kinetics model.A few measurements were made by adding ferric chloride and ferrous chloride to the feed to the reactor. An order of magnitude increase in rate was observed with these sensitizers.
Behavior of countercurrent liquid‐liquid columns with a liquid metal
Authors: Johnson T. R. , Pierce R. D. , Teats F. G. , Johnston E. F. 
Published: June 2004

AbstractPacked columns are being considered for contacting liquid metals with molten salts to extract fission products from spent nuclear fuel. Extraction rates between a liquid cadmium alloy and a liquid chloride salt were measured at 530°C. in a prototype column. With a system of water and a low melting metal alloy, measurements of the pressure drop, limiting flow rates, and hold‐up were made and compared with the predictions of existing correlations. These data indicate that packed columns might be effective contacting devices for pyrochemical processes.
Heat and mass transfer in the wall region of turbulent pipe flow
Authors: Hughmark G. A. 
Published: June 2004

AbstractModels for the laminar sublayer of turbulent pipe flow are reviewed. The observations of the sublayer by Popovich and Hummel and the experimental fluctuation frequencies obtained by Shaw and Hanratty are used with the models to evaluate experimental heat and mass transfer data. The eddy diffusivity model and a parallel conductance model appear to be consistent with the experimental data.
Ultrafiltration of proteins in stagnation flow
Authors: Kozinski A. A. , Lightfoot E. N. 
Published: June 2004

AbstractThe effect of viscosity and diffusivity variations on concentration polarization during the ultrafiltration of protein solutions in two‐dimensional stagnation flows is investigated by numerical integration of the equations of continuity and motion. It is found that these effects are surprisingly small and insensitive to the forms of concentration dependence postulated. The high Schmidt numbers and low permeation rates characteristic of these systems result in considerable simplification of the analysis and permit use of a modified Chilton‐Colburn relation for predicting the onset of sludge formation at the membrane‐solution interface. The predicted dependence on Schmidt number agrees with published experimental data for other boundary‐layer flows and suggests the possibility of improved prediction of equipment performance.
Interfacial mass and heat transfer during evaporation: II. Effect of monomolecular films on natural convection in water
Authors: Navon Uri , Fenn John B. 
Published: June 2004

AbstractThe reduction in evaporation from a water substrate and the accompanying change in heat transport through the water induced by monolayers of cetyl alcohol and stearic acid are investigated. Evaporation resistance of the monolayer and Nusselt number in the water are determined at 2° to 22°C. The evaporation resistance increases with increasing surface pressure of the monolayer. In the presence of natural convection in the water, the Nusselt number decreases during monolayer compression. This reduction is larger than could be expected just from the lowered evaporative heat flux and the resulting reduction in the Rayleigh number. It may be due to a change in the surface hydrodynamic characteristics caused by the monolayer.
Parametric pumping: Modeling direct thermal separations of sodium chloride‐water in open and closed systems
Authors: Sweed Norman H. , Gregory R. Alan 
Published: June 2004

AbstractDirect thermal parametric pumping separations of a NaCl‐H2O‐ion retardation resin system have been investigated. Experimental breakthrough curves and batch parapump runs were used to determine the lumped‐parameter mass transfer coefficient λ and its dependence on velocity and temperature. Computer simulation of additional batch runs verified both the model and the STOP‐GO algorithm used to solve it. Computer estimates of open‐system behavior are presented.
Bubble coalescence in viscous fluids
Authors: de Nevers Noel , Wu Jen‐Liang 
Published: June 2004

AbstractThe gravity‐driven coalescence of 1‐ to 2‐cm. diameter air bubbles in glycerine and in water has been studied by high‐speed cinematography. The resulting coalescence behavior can be correlated by a simple model which assumes that each bubble trails a wake, and that the bubble coalescing from below accelerates when it enters the wake of the preceding bubble and thus overtakes the first bubble. The predictions of the model are not significantly altered by different assumed wake configurations.
Viscoelastic behavior of molten polymers in porous media
Authors: Siskovic Nandor , Gregory Dale R. , Griskey Richard G. 
Published: June 2004

AbstractThe modification of the Blake‐Kozeny equation for porous media flow using the power law has been shown to hold for molten polymers as well as for the previous cases for polymer solutions. The present work extended the correlation of friction factor with Reynolds number an additional three decades.It was also shown, however, that the modified Blake‐Kozeny equation broke down when bed shear rates were in the range of excessive curvature on the polymer flow curves (shear stress‐shear rate). In such cases it is suggested that the Newtonian Blake‐Kozeny equation, together with apparent viscosity data, could be used to correlate such porous media flow of non‐Newtonians.Appearance of viscoelastic effects at the critical Deborah number value of 0.05 predicted earlier were not found to hold. The data of the present investigation show that such a critical value must be at least 0.19 or even higher. This result helps to resolve partially the anomalous results obtained by previous investigators.
Crystallization: Kinetics and design considerations
Authors: Timm D. C. , Cooper T. R. 
Published: June 2004

AbstractThe following nucleation rate and growth rate relationships for the aqueous, continuous, cooling crystallization of potassium dichromate were determined from experimental crystal size distributions: J = 3.9 × 1010 (C – Ceq)0.9; r = 3.0 × 103 (C – Ceq)1.7. Since nucleation rate is of lower kinetic order than growth rate, higher levels of supersaturation will yield crystal distributions with a larger mean size. Therefore for this system, batch or plug‐flow reactors are preferred to continuous‐stirred tanks.
Heterogeneous phase behavior of solid carbon dioxide in light hydrocarbons at cryogenic temperatures
Authors: Jensen Robert H. , Kurata Fred 
Published: June 2004

AbstractSolubilities of solid carbon dioxide in liquid ethane, propane, and n‐butane were measured from the hydrocarbon triple point or mixture eutectic point to the triple point of carbon dioxide, and an experimental uncertainty was determined for each data point. A eutectic point was discovered in the carbon dioxide–n‐butane system at approximately 134°K., with a eutectic composition of approximately 0.25 mole % carbon dioxide. A nonlinear least squares analysis was used to fit the binary solubility data and carbon dioxide‐methane data from the literature to the Wilson equation for the liquid‐phase carbon dioxide activity coefficient. Better agreement with experimental data was obtained by adding two empirical constants to the Wilson equation. This study shows that the Wilson equation is an excellent model for solid carbon dioxide solubility in liquid methane, ethane, propane, and n‐butane, over the entire composition range, and that the Wilson equation provides a better model than do corrections based on regular solution theory.The ternary system carbon dioxide‐methane‐ethane was also studied, and liquid and vapor compositions were measured for each of ten ternary mixtures in solid‐liquid‐vapor equilibrium. Ternary phase diagrams were constructed, and an empirical correlation was derived for solid carbon dioxide solubility in methane‐ethane mixtures above 166°K. An important finding was that solid carbon dioxide is more soluble in some mixtures of methane and ethane than in either of the pure components.
Optimal control policies for tubular reactors experiencing catalyst decay: II. Multiple‐bed semiregenerative reactors
Authors: Ogunye A. F. , Ray W. H. 
Published: June 2004

AbstractThe optimal control problem for multiple beds is formulated and a distributed maximum principle derived. Gradient methods are then used to synthesize the optimal control policies for some examples in three‐bed isothermal and adiabatic reactors. Finally, examples are worked to illustrate the computational algorithm in adiabatic beds when optimal catalyst loading is to be determined, and when it is desired to distribute the feed in an optimal fashion between the beds. Reasonably good convergence was obtained in all the examples, so that the method appears quite feasible for determining optimal control policies in multiple reactors subject to catalyst decay.
Blood‐gas transfer in an axial flow annular exchanger
Authors: Chang Hsin‐Kang , Mockros Lyle F. 
Published: June 2004

AbstractThe rates of hemoglobin saturation and carbon dioxide reduction in blood flowing in an annular‐shaped membrane exchanger were studied theoretically by considering two limiting cases: the fluid‐limited case and the wall‐limited case. The blood is assumed to flow axially with a fully developed laminar profile. In the fluid‐limited analysis the membrane wall is assumed to be infinitely permeable, so the efficiency of the oxygenator depends solely on the rate of gas transport within the blood. In the wall‐limited case the blood is assumed to have infinite transport ability, thus the efficiency of the oxygenator is limited by the diffusion rate through the wall. For realistic radii ratio, the oxygenator is fluid limited, thus suggesting the need for enhanced blood mixing. In the fluid‐limited case the rate of gas transport depends on the radii ratio and a dimensionless length, which is independent of the cylinder sizes. IfPO2= 715 mm. Hg andPCO2= 0 mm. Hg are maintained at both walls, oxygenation is the slower process. For the same flow rate the length required for complete hemoglobin saturation in the annulus with an inner to outer radius ratio of 0.95 is 1/65 of that required in a circular tube.
Precipitate flotation of chromium
Authors: Bhattacharyya Dibakar , Carlton J. Andrew , Grieves Robert B. 
Published: June 2004

AbstractA three‐stage procexsss of reduction of acid chromate (HCrO4−), with NaHSO3followed by precipitation of Cr(III) with NaOH followed by flotation with an anionic surfactant, provides 97% removal of chromium from aqueous suspensions containing 48.3 mg./liter Cr (0.929 mM). The required dosage of surfactant (sodium laurylsulfate) is 0.093 mole SLS/mole Cr, compared to a dosage of 1.1 mole cationic surfactant/mole Cr, used to ion float soluble acid chromate. The precipitate flotation process is pH dependent: below pH 6.3, soluble chromium species become appreciable and the flotation results agree with calculated soluble chromium concentrations; above pH 9.7, the charge of the precipitate is reversed, as indicated by surface potential measurements. The optimum pH range for flotation is 7.0 to 8.8. The effect of initial surfactant concentration on the flotation efficiency is established. Small quantities of calcium enhance the flotation of Cr, while higher concentrations, 0.5 mM and greater, decrease flotation efficiency. For suspensions with a doubled chromium concentration (96.6 mg./liter), the optimum pH range for flotation is lowered and narrowed to 6.3 to 6.5, indicating modifications in particle surface characteristics validated by measurements of surface potential and surfactant adsorption. Eighty‐seven percent flotation is achieved at a 0.093 mole/mole ratio.
Mathematical analysis of sorption experiments
Authors: Duda J. L. , Vrentas J. S. 
Published: June 2004

AbstractA new technique is derived for determining the concentration dependence of diffusion coefficients from sorption experiments. In this analysis the diffusion equation including the effects of phase volume change and volume change on mixing is solved by a weighted residual method to produce approximate analytical expressions which describe the sorption process. It is possible to deduce the concentration dependence of the diffusion coefficient from a single sorption experiment without assuming the form of the diffusivity‐concentration relationship. A direct evaluation of the technique is obtained from the analysis of test data generated by finite‐difference solutions of the equations which portray the sorption process.
Polymerization in a tubular reactor
Authors: Lynn Scott , Huff James E. 
Published: June 2004

AbstractA mathematical model has been developed to predict the variations in temperature, velocity, and composition which occur during anionic polymerization in laminar flow in a tubular reactor. It is found that very large radial gradients in all three are to be expected when a solution containing only solvent and monomer is polymerized. Recycle of part of the product or prepolymerization in stirred‐tank reactors may be used to reduce greatly the distortion of the radial profiles.
Improvement of the performance of a fixed‐bed catalytic reactor by relaxed steady state operation
Authors: Bailey J. E. , Horn F. J. M. 
Published: June 2004

AbstractThe relaxed steady state operation of a tubular fixed‐bed catalytic reactor under control of the inlet composition is investigated. It is shown that the performance of such a reactor can be improved under certain conditions by periodically varying inlet concentrations rather than keeping these concentrations time invariant.
Eqation of state for phase equilibrium: I. Pure component
Authors: Yang Chang‐Lee , Yendall E. F. 
Published: June 2004

AbstractAn equation of state for the two‐phase region whose constants depend only on the critical pressure, the critical temperature, the normal boiling temperature, and the latent heat at the normal boiling point is shown to describe vapor pressure, latent heat, and saturation volumes of methane well.