bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics of catalytic cracking selectivity in fixed, moving, and fluid bed reactors
Authors: Weekman Vern W. , Nace Donald M. 
Published: June 2004

AbstractA kinetic mathematical model of catalytic cracking is described which accounts for conversion and gasoline yield in isothermal fixed, moving, and fluid bed reactors. The model has been tested and verified by using laboratory moving bed data with a commercial gas oil and catalyst. It is shown that under certain conditions, the selectivity behavior and maximum gasoline yield of fixed, fluid, and moving bed reactors will be identical. Maximum gasoline yield is defined in terms of both the kinetic parameters and the process variables for fixed, moving, and fluid bed reactors.
An experimental study of steady state multiplicity and stability in an adiabatic stirred reactor
Authors: Vejtasa S. A. , Schmitz R. A. 
Published: June 2004

AbstractSteady state and transient characteristics of an adiabatic, continuous flow, stirred reactor were studied in experiments employing the exothermic reaction between sodium thiosulfate and hydrogen peroxide in aqueous solution. Results illustrate the multiplicity of steady states in this system over a range of residence times. Temperatures of unstable states were attained experimentally by observing the effect of perturbations from stable temperatures. The observed steady states of the reactor under various mixing conditions are shown to be in good agreement with the predictions of a mathematical model which is based on the assumptions that mixing is perfect and that a single independent chemical reaction occurs. Less exact quantitative agreement between theoretical and experimental unsteady performance is accounted for in terms of the sensitivity of the unsteady state to small errors in the system parameters and the existence of appreciable extraneous heat capacities of the experimental equipment.
Heat transfer from boundary layers undergoing an acceleration induced reverse transition
Authors: Talmor Eliyahu , Weber Norman 
Published: June 2004

AbstractAn experimental and analytical investigation of heat transfer in an acceleration induced transitional flow regime is presented. A previously developed criterion for the onset of reverse transition of turbulent boundary layers is combined with a theory of forward transition to derive the effect of free‐stream turbulence intensity on the critical value of an acceleration parameter for two initial velocity profiles within the turbulent boundary layer. The results are consistent with experimental observations.Local heat transfer measurements were obtained along converging walls of rectangular flow channels having convergence angles of 45, 60, and 70 deg. Free‐stream turbulence (1.6 to 11%) was induced by grids upstream of the start of convergence, and the local Reynolds number were varied by variation in channel size and stagnation pressures (200 to 500 lb./sq.in. abs.) at a gas stagnation temperature of 1,500°R.The results indicate a two‐stage reverse transition process along the converging wall with a forward transition between the two stages of reverse transition. The local Nusselt numbers obtained over a wide range of an acceleration parameter are correlated with the local Reynolds number, the acceleration parameter at the start of convergence, and the local flow area contraction ratio. The corrlation is in the form of laminarization paths having negative slopes for (NNu)r/(NPr)0.4 vs. (NRe)r at common area ratios. Local values of free‐stream turbulence intensity are required for proper application of the reverse transition criterion in conjunction with the heat transfer correlation presented.
Viscous incompressible non‐Newtonian flow around fluid sphere at intermediate Reynolds number
Authors: Nakano Yoshisuke , Tien Chi 
Published: June 2004

AbstractApproximate expressions of velocity profile and drag coefficients have been obtained for viscous incompressible non‐Newtonian flow over a fluid sphere in the intermediate Reynolds number range.The equations of motion of both external and internal fluids are satisfied by using Galerkin's method. The internal fluid is assumed to be Newtonian, while the external is assumed to be non‐Newtonian and can be described by the power law model. Furthermore, the condition that the tangential stress is transmitted across the fluid‐fluid interface without diminution is also satisfied with Galerkin's condition.Comparisons are also made between the predicted results and the experimental data available in the literature. The possible reasons for the discrepancy are also discussed.
The effect of surface active agents on liquid‐liquid mass transfer rates
Authors: Mudge Lyle K. , Heideger William J. 
Published: June 2004

AbstractAn interferometric investigation of the transfer of n‐ and iso‐butyl alcohols from water to carbon tetrachloride revealed the existence of large interfacial resistances (500 to 2,500 sec./cm.) attributable to the presence of surface active agents. Evidence of a solute‐surfactant interaction has been obtained with sodium dodecyl sulfate and sodium tetradecyl sulfate, but the effect appears to be much less pronounced with the shorter chain length surfactant or with the branched chain alcohol.
Iterative techniques in optimization: II. The linearity difficulty in dynamic programming and quasilinearization
Authors: McDermott Colin , Lee E. S. , Erickson L. E. 
Published: June 2004

AbstractThe quasilinearization technique is used to overcome the dimensionality difficulty in dynamic programming. The advantage of this approach is that not only the dimensionality or the fast memory requirement can be reduced, but the computation time required can also be reduced considerably. A technique is also devised to overcome the linearity difficulty encountered in this reduction in dimensionality. To illustrate the approach, the three dimensional crosscurrent extraction problem is solved as a one‐ and a two‐dimensional problem in the dynamic programming algorithm. Only approximately 1 min. is required to solve this one‐dimensional problem. However, if this problem were solved as a three‐dimensional problem, computation time of the order of hours would be required.
Determination of the mechanisms causing and limiting separations by column crystallization
Authors: Gates W. C. , Powers J. E. 
Published: June 2004

AbstractThe process of column crystallization at total reflux and steady state was analyzed mathematically and experimentally in order to determine the mechanisms by which separations are achieved and limited. The results of the study indicate that separation is produced by the formation of crystals in the freezing section and by interphase mass‐transfer in the adjacent purification section. The separation is mainly limited by axial eddy diffusion in the liquid phase.Data from three binary chemical systems were used in the study. The first system, m‐chloronitrobenzene‐m‐bromonitrobenzene, forms a solid solution with a small phase separation (less than 6 wt. %) and was the primary subject of this study. The second system, azobenzenestilbene, forms a solid solution with a phase separation which exceeds 20 wt. %. The third system, benzene‐cyclohexane, has essentially no solid solubility in the range of compositions for which data on separation have been reported (½ to 3 wt. % cyclohexane).Four mathematical models of column crystallization were developed and compared with experimental data. These models were based on different sets of assumptions as to the mechanisms which control the overall separation. The model which is consistent with experimental data was used to evaluate mass transfer coefficients and effective liquid‐phase diffusivities. Diffusivities varied between 1.3 and 4.6 sq. cm./sec., and mass transfer coefficients varied between 0.07 and 0.64 cm./sec. in reasonable agreement with results obtained in studies of liquid‐liquid extraction in pulsed columns.
Invariant imbedding, iterative linearization, and multistage countercurrent processes
Authors: Lee E. Stanley 
Published: June 2004

AbstractThe equations for multistage countercurrent operations are difference equations of the boundary‐value type, which are generally solved by trial and error or iterative procedures. The invariant imbedding concept is used to solve these boundary‐value problems as initial‐value problems. It is shown that by the combined use of invariant imbedding and iterative linearization, a sequence of estimator equations for the missing terminal conditions is obtained. These estimator equations can be used to obtain the desired terminal conditions and the number of stages required to perform a specified separation.
Natural convection distorted non‐Newtonian flow in a vertical pipe
Authors: DeYoung Scott H. , Scheele George F. 
Published: June 2004

AbstractThe equations of motion and energy are solved numerically for fully developed laminar flow of a power law fluid in a vertical pipe with constant heat flux at the wall. Density is assumed to be the only temperature dependent physical property of the fluid. Temperature profiles, velocity profiles, and Nusselt numbers are presented as functions of the power law exponent and the ratio of the Grashof number divided by the Reynolds number.
Adsorption of multicomponent mixtures by solid adsorbents
Authors: Gonzalez Agustin J. , Holland C. D. 
Published: June 2004

AbstractA procedure based on kinetic principles is presented for the development of models for the adsorption of mixtures of gases in any number of layers by solid adsorbents. Equations of state for two‐dimensional gas mixtures which are thermodynamically consistent with the adsorption models are also presented. The constants in the adsorption models for mixtures are obtained from the isotherms for the pure components. Good accuracy for the predicted adsorption of mixtures for the data available was obtained by use of a model for the adsorption of mixtures in bimolecular layers.
A correlation for the prediction of interaction energy parameters for mixtures of small molecules
Authors: Hiza M. J. , Duncan A. G. 
Published: June 2004

AbstractLow temperature, phase‐equilibria data for binary systems containing hydrogen, helium, and neon were used to develop a correlation relating deviations from the geometric mean combining rule for the characteristic energy parameter to the ionization potentials of the component species. With the exception of oxygen systems, this relatively simple relationship correctly predicts published deviations, determined by different methods, for a number of systems within expected uncertainties. It is shown that consideration of attractive forces only, as done by Hudson and McCoubrey, is inadequate for such predictions.
Calculation of solubility parameters of polar compounds
Authors: Konstam Aaron H. , Feairheller William R. 
Published: June 2004

AbstractA graphical method is presented for calculating solubility parameters and molar volumes of functional groups, as well as for calculating solubility parameters of high molecular weight members of a homologous series from data on low molecular weight members. These functional group solubility parameters and molar volumes have been used to extend the values of \documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt {EV} $\end{document} presented earlier by Small. Finally, it is shown that the use of group contributions to calculate cohesive energy is limited by the lack of information available on the intramolecular energies of interaction of functional groups on the same molecule.
Optimal control of a continuous flow stirred tank chemical reactor
Authors: Javinsky Martin A. , Kadlec Robert H. 
Published: June 2004

AbstractThe time optimal control problem for jacket cooled continuous flow stirred tank reactor (CSTR) with an exothermic, irreversible, second‐order, homogeneous, liquid‐phase reaction (the saponification of ethyl acetate) was solved with the maximum principle and phase plane analysis. Both experimental studies and analogue computer simulation studies were conducted.The overall performance of the experimental system agreed very well with the performance of the corresponding system simulated on an analogue computer. However, there were enough differences in the observed and predicted operating states and switching curves to warrant the conclusion that the experimental performance can be significantly improved if experimental results are used to modify the results predicted with computer analysis. These differences were attributed to uncertainties in the model and the values of the model parameters as well as nonrandom (and unforeseen) measurement errors.
The purification of Helium Gas by physical adsorption at 76°K
Authors: Kidnay A. J. , Hiza M. J. 
Published: June 2004

AbstractThe physical adsorption isotherms for three methane‐helium mixtures, two nitrogen‐helium mixtures, and one methane‐nitrogen‐helium mixture were measured at 76°K. and pressures of 2 to 65 atm. on a coconut shell charcoal. The adsorption isotherms of the pure components (nitrogen, methane, and helium) were also determined over the appropriate pressure ranges.Methods for predicting the mixture adsorption isotherms by using only the pure component isotherms are discussed and are shown to be adequate for these systems.The concentration vs. time or breakthrough curves were also measured for both the binary and ternary mixtures at a number of different flow rates. Mass transfer coefficients for both the gas phase and the absorbed phase were obtained from these breakthrough curves.
Numerical treatment of fully developed laminar flow in helically coiled tubes
Authors: Truesdell L. C. , Adler R. J. 
Published: June 2004

AbstractLaminar flow in helically coiled tubes is treated numerically. Fully developed axial and secondary velocities are calculated for both circular and elliptical cross sections. Only closely wrapped helices, that is, helices with modest pitch, are considered. Ten solutions with Deans numbers up to 200 have good accuracy. Two additional solutions with Deans numbers up to 280 are approximate.
Optimal stochastic control of nonlinear systems
Authors: Seinfeld John H. 
Published: June 2004

AbstractAn algorithm is proposed for the feedback control of nonlinear systems, the observations of which are corrupted with noise of unknown statistics. The feedback loop contains a nonlinear Kalman filter, which produces sequential least‐square estimates of the state of the system, and a controller designed to minimize an instantaneous performance criterion based on the state estimates. The scheme requires the on‐line integration of n(n + 3)/2 differential equations, where n is the number of unknown states and parameters. The scheme is applied to the feedback control of a CSTR with a first‐order exothermic reaction the temperature measurements of which are corrupted with random noise.
Unsteady state behavior of multicomponent distillation columns: Part II: Experimental results and comparison with simulation during start‐up at total reflux
Authors: Howard G. Michael 
Published: June 2004

AbstractExperimental concentration profiles throughout a fourteen plate column approaching steady state at total reflux were obtained for mixtures of benzene, toluene, and ethylbenzene. The concentration profiles are characterized by a large movement of the middle component, toluene, through the column so that its maximum concentration shifts from plate to plate until steady state is reached.Computer runs were made in which the column variables were specified to be, as nearly as possible, those observed or calculated for the experimental runs. The computer results indicated the same behavior as the experimental runs, and the concentration profiles were in fair agreement. Thus, the computer model and calculation procedure used could replace the real column for many purposes. Inaccuracies in the computer simulation are due more to inadequate information about the characteristics of the real column than to deficiencies of the computer model.
Chromatography of nonadsorbable gases
Authors: Cerro Ramon L. , Smith J. M. 
Published: June 2004

AbstractChromatographic techniques are used with nonadsorbable and slightly adsorbable tracers to evaluate mass transfer parameters in packed beds. If accurate values of intraparticle diffusivities are to be obtained, it appears that long beds of relatively large particles must be used. Otherwise the moments of the chromatographic peaks are too small for accurate analysis. With adsorbable gases, such precautions are not necessary, and, in addition, the adsorption rate constant can be estimated. However, the intraparticle diffusivity determined for adsorbable gases can include a contribution due to surface migration. The method is applicable to all types of porous particles used as catalysts or catalyst carriers.A combination of measurements of slightly adsorbable and nonabsorbable tracers can be used to approximate the adsorption rate constant for a slightly adsorbable gas such as nitrogen.
Experimental and theoretical investigation of continuous flow column crystallization
Authors: Henry Joseph D. , Powers John E. 
Published: June 2004

AbstractA theoretical and experimental investigation of the separation achieved in a column crystallizer which utilizes a spiral conveyor was conducted to determine the effect of variables associated with continuous flow operation. A system that exhibits negligible solid solubility was used. Several feed mixtures containing less than 31,000 p.p.m. weight cyclohexane in benzene were employed. The principal variables evaluated in this study in a column of constant length were the feed position, internal crystal rate, and flow rates of terminal streams. A mathematical model is developed which considers axial dispersion and mass transfer between the liquid adhering to the crystals and the bulk liquid. The model satisfactorily explains the effect of the variables associated with continuous flow operation and shows that axial dispersion is more dominant in continuous flow than in total reflux operation. It is shown that multiple pass or cascade operation is necessary to produce material of purity higher than a critical level which is related to the feed composition. This occurs because of impurities in the crystal phase which are likely caused by volumetric inclusions.
Fog formation in boundary value problems
Authors: Toor H. L. 
Published: June 2004

AbstractFor a Lewis number one gas, the equations of energy and diffusion state that if local equilibrium exists in a fog region, fog may form in a continuous manner, but it may be vaporized only discontinuously at the boundary between fog and nonfog regions. The local rate of formation of fog is proportional to the square of the local gradient of temperature or concentration. A class of solutions to the transport equations has been obtained for problems in which no vaporization occurs at the fog boundary. Under these conditions, the temperature and concentration at the boundary of the fog region are both shown to be constant at values that depend only upon the initial and/or boundary values of temperature and concentration and upon the equilibrium curve.
Optimal operation of a variable‐volume stirred tank reactor
Authors: Lund Monty M. , Seagrave Richard C. 
Published: June 2004

AbstractFor certain classes of chemical reactions, it is possible to increase the yield of the desired products by choosing appropriate variable‐volume operating policies. An analysis of the steady state and semibatch operation of a stirred tank reactor demonstrates operating policies for both the isothermal and adiabatic case to maximize the steady state yield and to produce an improved semibatch yield. Computations carried out by using an analogue computer with a digital logic expansion system demonstrate further relationships between yield increase and operating policy.
Vapor‐liquid equilibrium in alcohol‐water systems containing dissolved acetate salts
Authors: Meranda David , Furter William F. 
Published: June 2004

AbstractIsobaric vapor‐liquid equilibrium data at atmospheric pressure are reported for seven systems, each consisting of water, an alcohol (methanol or ethanol), and an anhydrous acetate salt (of sodium, potassium, barium, or calcium) dissolved to saturation in the boiling liquid phase. These systems are intended to complete a matrix about the single system ethanol‐water‐potassium acetate for which data were reported previously.Solubility data are reported in terms of saturation salt concentration as a function of alcohol‐water proportionality in the liquid. Sodium acetate as well as potassium acetate was found capable of eliminating completely the ethanol‐water azeotrope.Major differences in the effects of these salts as compared to those reproted for other salts in the salt‐effect literature were observed. Systems were discovered in which the salt appeared to cause both salting out and salting in of the alcohol in differing composition regions of the same system, the predominating effect depending on the relative proportions of alcohol and water. Systems were also discovered in which the salt salted‐in the component in which it was less soluble. Both observed effects are in contradiction with previously accepted theories of salt effect in vapor‐liquid equilibrium.
Steady state technique for measuring fluxes and diffusivities in binary liquid systems
Authors: Rao S. S. , Bennett C. O. 
Published: June 2004

AbstractA steady state experimental technique for measuring fluxes of the components and diffusivities in binary liquid systems has been developed. Steady state diffusion is established through a sintered glass diaphragm of ultrafine porosity with a known concentration difference across the diaphragm. The concentrations are maintained by a flow of solution on one side of the diaphragm and an infinite sink on the other side. The fluxes and diffusivities are calculated from the measured flows and compositions. A syringe pump capable of delivering extremely small flow rates with good reproducibility is used to pump the solution past the sintered glass diaphragm. The diffusion cell design permits an accurate control of pressure drop across the diaphragm so that fluxes can be measured both with and without pressure gradients. The diffusion cell was calibrated by using the hydrochloric acid‐water system.Three binary systems, ethanol‐benzene, aniline‐benzene, and aniline‐carbon tetrachloride were chosen for diffusion studies. Diffusivity‐composition data for these systems at 25°C. were used to test the existing correlations for the concentration dependence of binary diffusivity. Of these, the empirical correlation of Vignes (11) represents the data satisfactorily. In addition, experimental molar diffusion flux ratio data for the above systems at 25°C. with no pressure gradients are reported and found to be essentially equal to the ratio of molar volumes of the components.
Conformal solution correlation for the nitrogen‐oxygen‐argon system
Authors: Calvin William J. , Smith Buford D. 
Published: June 2004

AbstractA correlation based on conformal solution theory has been developed for the excess properties of the nitrogen‐oxygen‐argon systems. A better method for calculating the conformal parameters makes possible the simulataneous correlation of the three excess properties FE, HE, and VE. Each binary is characterized by a k12, c12 set which represents corrections to the geometric and arithmetic mean combination rules. These binary constants predict the ternary data. Also, the correlation based on data at one atm. (77° and 84°K.) predicts the FE data accurately up to the critical points (110° to 120°K.).