bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance of packed columns: IX. Simulation of a packed column
Authors: Shulman H. L. , Mellish W. G. , Lyman W. H. 
Published: June 2004

AbstractA model is described which may be used to simulate a packed column for countercurrent gas‐phase controlled absorption with liquid‐phase reaction. The model consists of a number of continuous stirred‐tank reactors in parallel with equal volumes and mass transfer areas. A distribution is presented which uses one parameter to determine the fraction of total liquid throughput going to each reactor. The model successfully predicts all responses, including those of Kga versus time for no reaction, Kga versus inlet acid normality, and Kga versus inlet gas concentration for liquid‐phase reaction for the systems ammonia‐water and ammonia‐sulfuric acid. It also explains the increase in mass transfer obtained by pulsing and controlled cycling.
Pressure‐volume‐temperature behavior of carbon tetrafluoride using a variable‐volume cell of bellows design
Authors: Martin J. J. , Bhada R. K. 
Published: June 2004

AbstractThis paper presents data observed for the pressure‐volume‐temperature (P‐V‐T) behavior of carbon tetrafluoride (CF4) below room temperature, and uses these data in conjunction with higher temperature data from the literature to evaluate an equation of state. The P‐V‐T measurements were made via a variable‐volume technique without using a confining liquid. The variable‐volume design makes it possible to cover a range of specific volumes with a single charge, resulting in an efficient operating procedure.A unique bellows design with a 14‐fold volume variation was developed. The bellows contained the compound under study (CF4) and was surrounded by a hydraulic liquid whose pressure could be varied causing the bellows to expand or contract. The volume of the bellows was determined by measuring the volume of the hydraulic liquid. Calibrations were made using a gas (CO2) of known thermodynamic properties. Pressure measurements were made via a differential pressure transducer on three Heise gauges calibrated in place against a Ruska dead‐weight tester. The bellows cell was maintained in a well‐agitated bath whose temperature was measured by a platinum resistance thermometer.The data were taken by charging a known amount of the compound into the bellows and observing the pressure‐volume relationship at a fixed bath temperature. At the end of a run, the charge was recovered, the amount recovered agreeing within 0.01% with the amount charged.The observed data were analyzed graphically on pressure‐volume, pressure‐temperature, and compressibility diagrams. Very good consistency was observed with the higher temperature data from literature. The data were correlated analytically with the Martin equation of state. This equation represents all the data with an average deviation of 0.25%.
Simultaneous effect of macromixing and micromixing on growth processes
Authors: Fan L. T. , Tsai B. I. , Erickson L. E. 
Published: June 2004

AbstractInteraction of macromixing and micromixing in microbiological flow reactors based on a kinetic model of the Michaelis‐Menten type has been treated by considering two general types of flow systems: the system of n continuous stirred‐tank reactors in series (n‐CSTR's in series) and the series combination of a plug‐flow reactor and a continuous stirred‐tank reactor. Systematic schemes to describe the micromixing conditions of a reactor system are presented. Additional micromixing states are considered besides those proposed by Kramers and those proposed by Zwietering if the systems are employed as empirical models of a flow system. When the number of stirred‐reactor units in the system of n‐CSTR's in series is small, micromixing has a significant effect on the growth processes. As the number of reactor units increases, the micromixing effect on the growth processes decreases. The effect of micromixing is also important for a system described by a series combination of a plug‐flow reactor and a continuous stirred reactor. In addition, the exit concentrations from the system having the same residence time distribution and the same degree of segregation may be different from each other. Information obtained in this study is pertinent in the design of biological flow reactors and sewage treatment systems.
Complex reactions in oscillating reactors
Authors: Dorawala T. G. , Douglas J. M. 
Published: June 2004

AbstractPrevious work has shown that perturbation methods are useful for estimating the difference between the time average conversion obtained from an oscillating reactor and the optimum steady state value. The present study extends this approach to complex kinetic mechanisms. Both forced and self‐generated oscillations are studied, and in the latter case both positive and negative feedback control systems are used to alter the shape of the oscillations. The results indicate that large improvements in yields sometimes can be observed for parallel reactions but that only small improvements are possible for consecutive reactions, in the range of system parameters considered.
Turbulent flow of dilute polymer solutions through an annulus
Authors: Rubin Hillel , Elata Chaim 
Published: June 2004

AbstractA semiempirical analysis of the turbulent flow of dilute polymer solutions through an annulus between two coaxial tubes is presented. This analysis is based upon the assumption that the velocity profile is logarithmic in the turbulent region. The thickness of the laminar boundary sublayer is changed by adding polymers to the solvent; this change is different at each wall of the annulus. A series of experiments was conducted in an annular system. The experimental results fit the theoretical predictions quite well.
The dynamics of thin liquid films in the presence of surface‐tension gradients
Authors: Ludviksson V. , Lightfoot E. N. 
Published: June 2004

AbstractThe climbing of Marangoni films up vertical solid surfaces was investigated experimentally and theoretically. The system considered was a nonisothermal plate with its warm end partially immersed in a nonvolatile liquid. Observed film thicknesses and rates of climb were in agreement with an approximate hydrodynamic model obtained by assuming the supply capacity of the film to be rate limiting.The results of this study confirm the hypothesis is that previously observed liquid films formed against gravitational forces above equilibrium menisci are produced by surface‐tension inequalities. It is pointed out that hydrodynamic processes cannot allow for the advancement of the leading edge of Marangoni films and a separate physicochemical process is required to explain spontaneous spreading of these films. Evidence is presented for the formation of much thinner primary films ahead of the secondary bulk films described by hydrodynamics. These primary films appear to be produced by a combination of multilayer adsorption and/or surface diffusion. The kinetics of these diffusional processes may limit spreading rates when surface‐tension gradients become sufficiently large.Finally, the Marangoni films were found to be unstable in a manner hithertonot considered.
The coalescence of drops in liquid‐liquid fluidized beds
Authors: Maraschino Mario J. , Treybal Robert E. 
Published: June 2004

AbstractThe coalescence rates of equisized drops of organic liquids fluidized by water under conditions of mutual saturation were studied. A drop‐size separation technique permitted the direct count of the coalesced drops. Six organic liquids (benzene, cyclohexane, n‐butylacetate, methyl isobutyl ketone, diisobutyl carbinol, and tetrahydrobenzaldehyde) were used, and the coalescence was in all cases total, that is, without formation of small satellite drops.A new hydrodynamic model is presented to calculate the parameters governing the drainage of liquid between two deformable drops in head‐on collision. A parameter from this model permits correlation of the coalescence rates with only two arbitrary constants, provided the ratio of dispersed to continuous liquid viscosities lies between 0.5 and 2. High viscosity ratios or the presence of trace quantities of surfactant greatly depress the coalescence rate, while continued reuse of the dispersed liquid leads to a statistically significant reduction. The presence of a fog of very small droplets increases the coalescence rate.
Accumulation and continuous removal of impurities in fuel cells: I. One‐dimensional model
Authors: Lyczkowski R. W. , Gidaspow Dimitri 
Published: June 2004

AbstractA mode of operation and a design technique have been developed which permit the attainment of continuous purging of impurities directly from the gas compartments of a fuel cell—either anode, cathode, or both—with the realization of minimum reactant loss, most stable voltage and current output, and operating conditions with respect to reactant gas flow and electrolyte inventory. We have found a way to eliminate the complex periodic purge valves and attendant electronics by a fuel cell system which is both simple in structure and operation and which has a high degree of reliability. The technique was suggested by the observation that in dead‐ended fuel cell gas compartments, the inert impurities present in reactant gases tend to accumulate at the dead‐ended portion of the cell. Hence a small amount of bleed should be placed there. This observation has been made analytically by solving numerically a system of two partial differential equations simultaneously.
Pressure drop and holdup in horizontal slug flow
Authors: Greskovich E. J. , Shrier A. L. 
Published: June 2004

AbstractThe Dukler‐Hubbard slug‐flow model is used along with independent correlations for in situ holdup and slug frequency to predict pressure drops for two‐phase slug flow. The holdup and frequency correlations are for the most part based on data for air‐water flowing in a 1.50‐in. pipe. Predictions of pressure drop using this approach are compared with experimental data taken from studies utilizing various systems and pipes from 1.50 to 6.065 in. in diameter. Alternative correlations by Dukler and Hughmark for predicting two‐phase pressure drops and holdup, respectively, are included for comparison. In general, the present approach is at least equivalent to the Dukler‐Hughmark method, and for values of ΔP/L > 0.06 lb./sq. in./ft. appears to be slightly better.
Viscosity of gas mixtures at normal pressures: Binary polar‐nonpolar systems
Authors: Hattikudur U. R. , Thodos George 
Published: June 2004

AbstractAn interaction model is presented for the prediction of viscosities at normal pressures of gas mixtures containing a polar and a nonpolar constituent. This model is based on the principle of corresponding states and requires TR, the viscosity parameter ξ = T/M1/2P for each component, and the value of zc for the polar component.Viscosity measurements available in the literature for several binary systems have been used to establish interaction coefficients which have been correlated to obtain relationships capable of predicting them. This method has been applied to 14 systems for temperatures ranging from 288° to 523°K. to produce an average deviation of 2.64% for 356 experimental values.
The PVT behavior of isopropyl alcohol at elevated temperatures and pressures
Authors: Tseng James K. , Stiel Leonard I. 
Published: June 2004

AbstractExperimental PVT data have been obtained for isopropyl alcohol by the use of a constant‐volume apparatus. Smoothed values of the compressibility factor are presented for temperatures from 200° to 300°C. and pressures from 1,000 to 8,000 lb./sq. in. The experimental data are estimated to be accurate to within 0.4%. The compressibility factor of isopropyl alcohol is also analyzed by the fourth‐parameter approach. It is shown that the normal fluid relationship for the compressibility factor can be extended to polar fluids by the inclusion of linear and quadratic terms in the fourth parameter.
Interfacial shear viscosity at fluid‐fluid interfaces
Authors: Wasan D. T. , Gupta Lalit , Vora M. K. 
Published: June 2004

AbstractFluid‐fluid interfaces containing surface‐active agents or macromolecules exhibit interfacial shear viscosity phenomena. The purpose of this paper is to investigate theoretically the dynamics of liquid‐liquid and liquid‐gas interfaces containing surfactants, and to establish the validity of the proposed model from shear flow data at uncontaminated interfaces.A theoretical analysis for the measurement of interfacial shear viscosity at liquid‐liquid interfaces with an improved viscous traction surface viscometer is presented. The analysis takes into account the finite depths of the two liquids and permits interpretation of the experimental results in terms of interfacial shear viscosities at the liquid‐gas interface in addition to the liquid‐liquid interface. Results of the present analysis clearly show a strong coupling of interfacial and bulk fluid flows.Extensive measurements of the interfacial velocities at a xylene‐water interface were made. A cetane‐water interface was also studied. Interfacial flow data for uncontaminated systems were found to be in excellent agreement with theory.
Models for vapor‐phase and liquid‐phase mass transfer on distillation trays
Authors: Hughmark G. A. 
Published: June 2004

AbstractThree mass transfer models are developed for the vapor phase. The first model assumes a rigid interface between the liquid and vapor and yields the Schmidt number as the correlating variable. The other two models represent a free interface with the penetration theory as the mechanism for one model and eddy diffusion as the mechanism for the other model. Both free interface models correlate experimental data within the error of the data. A liquid‐phase mass transfer model is developed for a free interface and the penetration theory as the mass transfer mechanism. Design equations are developed from this analysis.
Membranes which pump
Authors: Cussler E. L. 
Published: June 2004

AbstractCarrier‐containing membranes which can pump a specific ion from a region of low concentration into a region of high concentration have been constructed. This pumping is a large effect, proportional to the amount of carrier present. The main requirement for this type of transport is that the carrier react competitively with two simultaneously diffusing solutes. One solute is pumped; the second supplies the energy for the pumping. A theory based on the assumption that the two carrier reactions are fast predicts that the amount pumped is proportional to the carrier concentration, that the pumping stops when the concentration gradient of the energy supplying solute reaches zero, and that the effect goes through a maximum when the solubility in the membrane of the solute being pumped decreases. These predictions are in agreement with experimental results for sodium transport across membranes containing a variety of carriers, including stearic acid, lecithin, and monensin.
Solutions for distillation processes treating petroleum fractions
Authors: Taylor D. L. , Edmister W. C. 
Published: June 2004

AbstractThe general solution for multicomponent distillation processes is used to obtain solutions for systems treating petroleum fractions. The integral technique is the basis for this adaptation. Example solutions are presented for a conventional distillation column, a distillation column with a side stream, and an absorber. The design capabilities of the general solution are illustrated by an absorber problem in which the composition of the lean vapor is specified. The amount of absorber oil, a petroleum fraction, required to accomplish this degree of separation is found.
Convective stability in the presence of a catalytic chemical reaction. Part I. Stationary instability
Authors: Wankat P. C. , Schowalter W. R. 
Published: June 2004

AbstractA linear analysis of hydrodynamic stability has been applied to a problem in which a fluid mixture is contained between two horizontal planes. One species diffuses to the lower plane where it is destroyed by a rapid exothermic or endothermic catalytic reaction. Results show that important coupling takes place between thermal and concentration fields. This coupling gives rise to unusual stabilizing or destabilizing effects, depending upon the value of Lewis number. Several examples are discussed. It is also shown how the results can be applied to other problems involving heat and mass transfer.
Joule‐Thomson effects for mixtures of helium‐nitrogen‐methane and hydrogen‐nitrogen‐methane
Authors: Sabnis Suman T. , Wenzel Leonard A. 
Published: June 2004

AbstractExperimental isenthalps and corresponding Joule‐Thomson coefficients are reported for nitrogen and equimolar ternary mixtures of helium‐nitrogen‐methane and hydrogen‐nitrogen‐methane. The estimated precision of the Joule‐Thomson coefficients was within 1.5% of recent literature values.These Joule‐Thomson coefficients are compared with predictions from the virial equation and Beattie‐Bridgman, Benedict‐Webb‐Rubin, and Redlich‐Kwong equations of state. The predicted Joule‐Thomson coefficients are as accurate as predictions for the pure species. Standard mixing rules and methods of combining equations of state constants are satisfactory at higher temperatures. At low temperatures the predictions from the equations of state are poor.
Hydrodynamic stability of marangoni films:II. A Preliminary analysis of the effect of interphase mass transfer
Authors: Wang K. H. , Ludviksson V. , Lightfoot E. N. 
Published: June 2004

AbstractThe stability of vertical laminar falling films subjected to interphase mass transfer and surface‐tension gradients in the direction of flow is investigated by linear perturbation analysis. The perturbations considered are vertical waves or rivulets as described by Ludviksson and Lightfoot for nonisothermal films. Perturbations of this type are thought to lead to the maldistribution of flow observed in distillation and gas absorption by Zuiderweg and Harmens and by Francis and Berg.Three unstable regions are predicted, one corresponding closely to that found by Ludviksson and Lightfoot, and two new ones, previously unreported, resulting from interphase mass transfer across the free surface.These predictions confirm the conclusions of Zuiderweg and Harmens for situations in which surface tension increases upward, and they provide a means of estimating the range of unstable gradients. Experimental evidence for instability predicted when the surface tension increases downward is inconclusive. Further investigation of this region, which is of considerable importance, is recommended.
An experiment on turbulent diffusion in additive solutions
Authors: Wu Jin 
Published: June 2004

AbstractTurbulent diffusion in high molecular weight additive solutions was measured and compared on a laboratory scale by observing the axisymmetric spreading of a cylindrical turbulent cloud in these solutions of various concentrations. Significant suppression of turbulence in additive solutions was observed. The trend of the results as a function of additive concentrations is similar to that of the additive reduction of turbulent frictional resistance.
Optimally sensitive and adaptive control systems
Authors: Weinrich S. D. , Lapidus Leon 
Published: June 2004

AbstractThe sensitivity of optimally controlled systems to parameter variations is examined in this paper. Two general approaches toward compensating for these variations are employed. The first, for open‐loop systems, involves augmenting the performance index with sensitivity terms and minimizing this combined index. The second approach, an adaptive‐type controller, involves estimating those parameter variations that have caused an observed state deviation, and adjusting the control policy in response to this measurement. Numerical examples applied to continuous, discrete‐time, and discrete‐staged systems demonstrate the effectiveness of these approaches in adapting the control policy to parameter variations.
Entrance region flow of polymer melts
Authors: Han Chang Dae 
Published: June 2004

AbstractAn experimental study has been made to investigate polymer melt flow in the entrance region of a circular tube. For the study, a capillary rheometer was used to measure wall normal stresses in polymer melts in the reservoir and along the axis of the capillary. In order to investigate the influence of reservoir diameter on the entrance pressure drops, reservoir‐to‐capillary diameter (DR/D) ratios of 3, 6, 9, and 12 were used, with the capillary length‐to‐diameter (L/D) ratio being 20 and the capillary diameter being 0.125 in. Analysis of the experimental data shows that the entrance pressure drop increases and then levels off as DR/D ratio is increased. A correlation between the dimensionless entrance pressure drop and Reynolds number has been obtained, which follows the creeping flow analysis by Weissberg over the range of the area contraction ratio studied, 0.00694 <β< 0.111.
Process optimization by the “complex” method
Authors: Adelman Alvin , Stevens William F. 
Published: June 2004

AbstractThe “complex” method of M. J. Box has been adapted and used to optimize the design of continuous chemical processes. Such a design involves the extremization of a nonlinear objective function subject of nonlinear equality and inequality constraints. The method consists of finding an original feasible “complex” of solutions, eliminating the worst of these by reflection through the controid of those remaining, and repeating until an optimum has been reached. An example of significant complexity has been solved and the results are reported. The method looks quite promising for use in the optimization of chemical process designs.
Drag reduction in dilute flowing gas‐solid suspensions
Authors: Rossetti Salvatore J. , Pfeffer Robert 
Published: June 2004

AbstractThe effect of solids loading ratio, particle size, and gas Reynolds number on the pressure drop and flow characteristics of a dilute gas‐solid suspension in turbulent pipe flow has been studied experimentally in both vertical and horizontal test sections. Glass beads of 10 to 60μ diameter were used at air Reynolds numbers of 10,000 to 25,000 and solids loading ratios of up to 2.5 Drag reduction was observed in the vertical test section for all of the particles studied, with the 30μ particles yielding a maximum drag reduction of about 75% at a loading ratio of 1.5. In the horizontal test section, drag reduction was observed only with the smallest sized particles, indicating a gravity effect. An explanation of these results based on the particles interacting with the turbulent structure of the gas near the wall has been proposed.
Surface diffusion of adsorbable gases through porous media
Authors: Roybal L. A. , Sandler S. I. 
Published: June 2004

AbstractAn activated diffusion, or site‐hopping, mechanism is used to describe surface diffusion of gases through porous media. This analysis provides a useful and accurate method for correlating data at submonolayer coverages on energetically heterogeneous surfaces. The data needed to use this correlation are surface area and pore structure of the adsorbent, adsorption isotherms at two or more temperatures, and the activation energy for migration. The former quantities are easily determined from Knudsen diffusion and adsorption measurements, while the activation energy can be found from a single permeability measurement. Predictions made in this way show excellent agreement with experimental data.
A new algorithm for the estimation of parameters in ordinary differential equations
Authors: Hwang M. , Seinfeld J. H. 
Published: June 2004

AbstractA new computational algorithm for the estimation of parameters in ordinary differential equations from noisy data is presented. The algorithm is computationally faster than quasilinearization because of the reduction of the number of ordinary differential equations that must be solved at each iteration. A modification is also presented to remove ill‐posedness. The algorithm is illustrated on a simple example.