bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vapor‐liquid equilibrium constants at infinite dilution determined by a gas stripping method: Ethane, propane, n‐butane, n‐pentane in the methane‐n‐decane system
Authors: Legret D. , Desteve J. , Richon D. , Renon H. 
Published: June 2004

AbstractA new apparatus to measure partition coefficients K at infinite dilution up to 200 105 Pa and 423 K is described. Measurements of the systems: (1) methane‐ethane‐n‐decane and methane‐propane‐n‐decane at 294.25 K; and (2) methane‐n‐butane‐n‐decane at 344.25 K illustrate the reproducibility and good agreement with literature data. In addition, new data were obtained for the system methane‐n‐pentane‐n‐decane at 344.25 K up to 101 105 Pa.
Selective electrorefining with liquid membranes
Authors: Gökalp Mehmet , Hodgson K. T. , Cussler E. L. 
Published: June 2004

AbstractLiquid membranes containing macrocyclic polyethers can be used to electrorefine metals. This purification depends on the selective reaction of the polyether and the metal cation to produce a charged product. The amount of this product is found to be proportional to the square root of the amount of polyester present. Results for silver and copper purification illustrate the ideas involved.
Close‐clearance helical impellers: A physical model for newtonian liquids at low Reynolds numbers
Authors: Chavan V. V. 
Published: June 2004

AbstractWith simple hydrodynamic concepts, a physical model is developed to describe the flow at the wall close to the impeller blade. The parameters of this model were evaluated from the large amount of data on power consumption and checked with some independent data on velocity profiles. Together with the physical insight provided by the model, it helped to obtain general relationships for power and heat transfer coefficients. Equations for the latter were developed using Lévêque's approximation. Agreement between the predicted results and the literature data of several independent studies was rather good. A method to analyze mixing or blending results is also suggested.
Reduced‐order steady‐state and dynamic models for separation processes. Part I. Development of the model reduction procedure
Authors: Cho Y. S. , Joseph B. 
Published: June 2004

AbstractOne of the major difficulties with mathematical models of staged separation systems is the large dimensionality of the process model. This paper is concerned with simple (reduced‐order) steady‐state and dynamic models for processes such as distillation, absorption and extraction. The model reduction procedure is based on approximating the composition and flow profiles in the column using polynomials rather than as discrete functions of the stages. The number of equations required to describe the system is thus drastically reduced. The method is developed using a simple absorber system. In the second part of this paper, the application of the method to nonlinear multicomponent separation systems is demonstrated.
Pressure drop for cocurrent downflow of gas‐solids suspensions
Authors: Kim J. M. , Seader J. D. 
Published: June 2004

AbstractPressure drop for a gas‐solids suspension flowing concurrently downward in a 13‐mm inside‐diameter tube was investigated using 329‐micron spherical glass beads in air. The gas Reynolds number varied from 0 to 30,000 with solids‐loading ratios of up to 20 at a gas Reynolds number of 10,000. The frictional pressure drop for downflow was found to be a weaker function of the solids‐loading ratio than the upflow case using data reported in the literature. Empirical correlation of the two‐phase friction factor, in terms of the gas Reynolds number and a dimensionless parameter, CDEPD/[(1 – Ep)dp], showed that at high solids loadings, particles tend to stabilize the suspension flow. The dimensionless parameter seems to be applicable to a universal pressure drop correlation for solids‐fluid systems, but requires further investigation.
Mechanisms for solids ejection from gas‐fluidized beds
Authors: Levy E. K. , Caram H. S. , Dille J. C. , Edelstein Sergio 
Published: June 2004

AbstractThe bubble eruption process was studied in two‐ and three‐dimensional (2D and 3D) beds using a high‐speed video system for flow visualization. The results show the existence of four different ejection mechanisms; one occurring with singlebubble eruptions in both 2D and 3D beds, two others occurring in 2D and 3D beds with two bubbles coalescing at the bed‐free surface, and the fourth occurring only in 3D beds with bubbles coalescing at the bed surface.
Mechanism of pore formation in reverse osmosis membranes during the casting process
Authors: Neogi P. 
Published: June 2004

AbstractThe process of pore formation during the casting of reverse osmosis membranes is analyzed. The process consists of two steps. The first step is the evaporation step, where the cast polymer solution is allowed to dry for 1 ∼ 100 s. The second step is the gel formation step, where the cast is soaked in water leaving behind the membrane in form of a gel. The evaporation step gives rise to a thin (∼0.1 μm) skin of high density and very small pores which is chiefly responsible for desalination. The gel forms the backing (∼100 to 250 μm) and contains large pores.It is shown that low evaporation rates accompanied by shrinkage during evaporation gives rise to an instability leading to the formation of the skin region. The evaporation effect is fast, is confined to the skin region, and gives rise to very small pores. The gel formation is shown to be a very slow process which cannot interfere with the skin formation due to the vast differences in their rates of formation. It also gives rise to larger pores. All key features of the above experimental observations are explained.The kinetics of the process depend on the diffusion coefficients D and Dp of the solvent and the polymer. However, the main factor is the solution chemistry of the polymer‐solvent system which controls both the effectiveness of the skin and the gel formed. For the first time, the relevant thermodynamic parameters which determine the extent and sizes of pore formation have been obtained.
Model of continuous dispersive flow with interactive deadwater and application to gas‐phase flow in rotary calciners
Authors: Spencer B. B. , Whatley M. E. , Watson J. S. 
Published: June 2004

AbstractA continuous flow model is developed which describes flow through a vessel in which the fluid undergoes axial dispersed plug flow and some of the flid is held back in a deadwater zone. The first three moments of the concentration‐time curve are related to the three parameters of the model, and an equation is presented to predict the outlet concentration from the vessel as a function of time for an impulse input. The model is used to analyze experimental gas‐phase residence‐time distribution (RTD) data collected from a small rotary calciner operated at room temperature. These data are well represented by the model.
Variable volume enzyme reactor with ultrafiltration swing: A theoretical study on CSTR case
Authors: Kim In Ho , Chang Ho Nam 
Published: June 2004

AbstractA new membrane enzyme reactor system is proposed, and its performance is analytically and numerically examined by operational modes. This membrane‐separated, two‐compartmental reactor is operated in a cyclic manner such that ultrafiltration swing is induced either by a pulsatile flow or by an alternating pressure difference. Substrate and product solutins are permeable to the membrane while enzyme is impermeable. In one reservoir, enzyme solution is stored into which substrate is supplied by diffusion‐coupled ultrafiltration and product is removed by the same mechanism into the substrate compartment, which is similar to CSTR in view of fluid mixing and continuous inlet‐outlet flows, but differs from CSTR in a sense that reaction takes place only in the enzyme compartment.The governing model equations are derived and their analytical solutions are obtained for fast reaction and high ultrafiltration with first‐order kinetics. In addition, nonlinear Michaelis‐Menten kinetics problem is solved numerically. As a result, we have found that the system can increase the conversion substantially compared with previous diffusion‐moderated enzyme reactors where diffusion very often can limit the extent of conversion.
Heat and power networks in process design. Part II: Design procedure for equipment selection and process matching
Authors: Townsend D. W. , Linnhoff Bodo 
Published: June 2004

AbstractIn Part I, criteria for heat engine and heat pump placement in chemical process networks were derived, based on the “temperature interval” (T.I) analysis of the heat exchanger network problem. Using these criteria, this paper gives a method for identifying the best outline design for any combined system of chemical process, heat engines, and heat pumps. The method eliminates inferior alternatives early, and positively leads on to the most appropriate solution. A graphical procedure based on the T.I. analysis forms the heart of the approach, and the calculations involved are simple enough to be carried out on, say, a programmable calculator. Application to a case study is demonstrated.Optimization methods based on this procedure are currently under research.
Theoretical model of the boundary condition at a fluid‐porous interface
Authors: Ross S. M. 
Published: June 2004

AbstractAn equation for the volume average fluid velocity in a boundary layer region between a fluid and a porous medium is derived. The result is valid for a general anisotropic porous medium subject to the restrictions imposed by the assumptions made in the analysis. The basic equations of motion for an incompressible Newtonian fluid with negligible inertia are used and a linear map Mij from the volume average velocity 〈v〉 into the point velocity v is assumed to exist. Using scaling arguments, an equation for 〈v〉 is found which reduces to the Darcy equation for a point entirely within the porous medium below the boundary region and to the usual Navier‐Stokes equation for a point entirely within the fluid above the boundary region. The form of the equation contains two of the terms that were originally hypothesized and tested experimentally by Beavers and Joseph (1967). In particular, the following equation is obtained:

where the tensors Kij, Ljmk and Njm are mathematically defined in terms of the map Mij.
Laser doppler measurements of flow in freeboard of a fluidized bed
Authors: Levy Y. , Lockwood F. C. 
Published: June 2004

AbstractOne of the factors which reduces combustion efficiency in a fluidized‐bed combustor is the elutriation of fine coal particles from the freeboard above the bed surface. To our knowledge, data about the real local flow behavior of the two‐phase flow in the freeboard are lacking in the literature. This paper concerns the measurement of the gas and the elutriated particle velocities in the freeboard of a cold fluidized bed using Laser Doppler Anemometry. A special electronic system has been devised to record simultaneously the gas and particle velocities and to indicate the size of the particles. In this paper the apparatus and some preliminary measurements are reported. The most significant observation is that the gas velocity profiles exhibit minima near the bed center and maxima near the walls.
Variable‐volume hollow‐fiber enzyme reactor with pulsatile flow
Authors: Kim In Ho , Chang Ho Nam 
Published: June 2004

AbstractHollow‐fiber device has been used to investigate the effect of ultrafiltration swing on the performance of membrane‐enzyme reactor. Experiments with β‐galactosidase and ONPG have shown that bidirectional ultrafiltration induced by pulsatile flow gives rise to an increase in conversion relative to that obtained at steady operation without ultrafiltration swing. This increase apparently comes from the enhanced mass transfer due to ultrafiltration.
Separating efficiency of a water elutriator
Authors: Biddulph M. W. 
Published: June 2004

AbstractThis paper investigates the separating efficiency of a vertical water elutriator operating on particle mixtures. In particular, comparisons are made with a previously developed mathematical model based on an eddy diffusion mechanism of mixing. Standard mixtures of glass spheres, of uniform size and shape, are used to study the equipment characteristics. It is found that the separating efficiency follows the same trend as predicted by the model and that “wall flow” of particles occurs. This affects the required water velocity, resulting in the equipment producing a top product generally purer than the bottom product.
Separation of benzene and toluene from close boiling nonaromatics by extractive distillation
Authors: Berg Lloyd 
Published: June 2004

AbstractBenzene and toluene are virtually impossible to separate from close boiling nonaromatic hydrocarbons by rectification. Benzene and toluene can be readily separated from similar boiling nonaromatics by using extractive distillation in which the extractive distillation agent is a proper mixture of organic compounds boiling higher than benzene or toluene. A typical extractive distillation agent for benzene is a mixture of phthalic anhydride, maleic anhydride, and adiponitrile; for toluene, phthalic anhydride, maleic anhydride, and glycerol triacetate.
Kinetics of pyrolysis of some fire retardants and treated fabrics
Authors: Gadalla A. M. , Abadir M. F. , Kasem M. Y. , Salem F. T. 
Published: June 2004

AbstractIntermediate phases and reactions occurring on decomposing diammonium hydrogen phosphate, ammonium para molybdate, sodium tungstate dihydrate and ammonium meta vanadate were established by thermal analysis and X‐ray examination.These salts promote fabric degradation at low temperatures but are effective at high temperatures. Diammonium hydrogen phosphate produced maximum amount of gases, absorbed the highest amount of heat and gave the highest fire retardation above 350°C.
Selective adsorption of organic homologues onto activated carbon from dilute aqueous solutions: Solvophobic interaction approach: Part IV. Effect of simple structural modifications with aliphatics
Authors: Belfort Georges , Altshuler G. L. , Thallam K. K. , Feerick Jr C. P. , Woodfield K. L. 
Published: June 2004

AbstractPreferential adsorption of organic compounds onto activated carbon from dilute aqueous solutions is studied to develop a comprehensive theoretical basis for predicting the adsorption of structurally different isomers for different homologous series. The fundamental multidimensional approachof the solvophobic (cϕ) thermodynamic theory is further refined and used to correlate the extent of adsorption for the comprehensive theory with the overall standard net free energy change (ΔGnet/RT) for the association‐adsorption reaction in solution, and for the simplified theory with the cavity surface area of the solute (TSA).Experimental adsorption isotherms of two homologous series (12 aliphatic alcohols and 21 aliphatic ketones) were measured and used to test and compare the cϕ theory with seven independent parameters characterizing the sorbates. Several experimental innovations for measuring equilibrium adsorption isotherms are introduced to reduce the possible loss of sorbate during the procedure and to provide reproducible and reliable results.Comparing the coefficients of linear correlation (r), the results for 12 aliphatic alcohols give greater than 99% confidence that the r‐values are different for ΔGnet/RT and molecular weight (MW). For the 15 aliphatic ketones, greater than 90% confidence interval is obtained for different r‐values for TSA and MW.These results support the contention that simple structural modifications of aliphatic homologous compounds can be used to predict the effect of solute‐solvent‐sorbent interactions on adsorption. The cϕ theory can thus be used to rank‐order adsorption intensity of these compounds from the aqueous phase onto activated carbon.
Experimental and mathematical modeling of three‐dimensional natural convection in an enclosure
Authors: Curlet N. W. E. , Won K. J. , Clomburg L. A. , Sarofim A. F. 
Published: June 2004

AbstractThree‐dimensional natural convection patterns in an enclosure under conditions simulating flow in glass‐making furnaces have been calculated using an approximate method in which solutions for the temperature and velocity fields in orthogonal two‐dimensional planes are superposed. The computational method was tested by comparison with measurements of the temperatures and velocities in an enclosure heated and cooled from above and with a controlled heat loss from the sides. Good agreement was found between measurements and computations under conditions of interest in glass‐making furnaces, wherein the motion in one of the two orthogonal planes is dominant.
Experimental study of deep bed filtration: A stochastic treatment
Authors: Hsu E. H. , Fan L. T. 
Published: June 2004

AbstractA stochastic pure birth process, which describes pore blockage in a filtration process, has been coupled with the Carman‐Kozeny equation to simulate the pressure buildup in deep bed filtration. It has been shown that the resultant one parameter model equation fits adequately the experimental data obtained under the straining dominated condition, and that available data obtained under the adhesion dominated condition can also be described by the model.
Kinetics of short contact time coal liquefaction. Part II: Effect of nature of coal and solvent
Authors: Abichandani J. S. , Wieland J. H. , Shah Y. T. , Cronauer D. C. 
Published: June 2004

AbstractA bituminous coal (Powhatan No. 5) and a subbituminous coal (Belle Ayr) were liquefied in the presence of hydrogen donor solvents. Statistical analyses of the data showed that for contact times up to 10 min, the coal conversion, measured in terms of tetrahydrofuran solubles, was not significantly different for the two coals. However, the subbituminous coal gave more asphaltenes than the bituminous coal.The hydrogen‐donating capacity of the solvent was varied by the addition of hydrogenated phenanthrene to SRC‐II recycle solvent. The results indicated that there are two routes for the formation of oils from coal. One is by adduct formation giving asphaltenes and preasphaltenes, which in turn gives oils, and the other is direct oil formation from coal. The preferred route depends on the hydrogen‐donating capacity of the solvent. The kinetic model, proposed in Part I of this paper, is extended to account for the change in the donor capacity of the solvent.
Coupled boundary layer transport involving particles
Authors: Shaeiwitz J. A. 
Published: June 2004

AbstractParticle deposition by diffusiophoresis and thermophoresis is described using the linearized Fickian multicomponent diffusion equations. For these cases, the diagonal component of the diffusivity matrix for the particle is expected to be much smaller than the other diagonal components. Intuitive arguments, dimensional analyses and the standard interfacial transport theories in multicomponent form suggest that the larger boundary layer due to the larger diffusivity component describes the transition between bulk and surface values for both components.
Anomalous convective diffusion in films of polymeric solutions
Authors: Mashelkar R. A. 
Published: June 2004

AbstractThe process of gas absorption in freely falling films of dilute polymer solutions under different kinematic conditions shows some hitherto unreported and dramatic differences. The absorption rates are reduced when films are generated under rapid stretch conditions over axisymmetric bodies of revolution, whereas they are enhanced when films are generated in a long, wetted wall column. Absorption rates are enhanced on polymer addition in freely falling turbulent films. Possible mechanistic explanations have been offered for these phenomena.
Dynamics and control of an activated sludge process as a mixed culture system
Authors: Takamatsu Takeichiro , Shioya Suteaki , Kurome Hirokazu 
Published: June 2004

AbstractOne of the difficulties encountered in the operation of an activated sludge process is the phenomenon of bulking sludge.In an activated sludge process which is composed of a completely mixed aeration tank and a sedimentation vessel, the dynamic behavior of the system can be analyzed using a mathematical model. The model developed here is based on the kinetics and settleability of the combination of floc‐forming sludge and bulking sludge. The operating conditions that cause the bulking phenomenon are clarified on the phase plane. It is also shown that a type of nonlinear state feedback regulator makes the system stable.
Prediction of the effect of weeping on distillation tray efficiency
Authors: Lockett M. J. , Rahman M. A. , Dhulesia H. A. 
Published: June 2004

AbstractThe reduction in distillation tray efficiency caused by uniform weeping of liquid from the tray has been calculated. Numerical results are presented for all three Lewis cases over the range of variables of interest to tray designers. Analytical equations are given for Lewis' cases 2 and 3 for plug flow of liquid on the tray.
The VIM theory of molecular thermodynamics: Part II: Analytic equation of state of polar fluids
Authors: Alem A. H. , Mansoori G. A. 
Published: June 2004

AbstractVariational inequality minimization (VIM) theory of statistical mechanics is used to derive analytic equations of state for polar fluids. For the pair‐intermolecular potential energy function in the formulation of this theory, the Lennard‐Jones, dipolar, quarupolar, and dipolar‐quadrupolar interactions are used. For the three‐body potential Axilrod‐Teller function is used. The VIM theory has made it possible to derive algebraically analytic expressions for the thermodynamic functions of polar fluids. Thermodynamic properties of carbon dioxide, methyl chloride, ethane, hexane, iso‐butane, and sulfur dioxide in the liquid and vapor phases are predicted with the use of the VIM equation of state. The results of the predictions are shown to be in very good agreement with the experimental data for majority of the fluids which are studied.
Effect of the interfacial viscosities upon displacement
Authors: Stoodt T. J. , Slattery J. C. 
Published: June 2004

AbstractA capillary rise technique was developed for measuring the effect of the surface viscosities upon the displacement of air by liquids in glass capillaries. Measurements were made in two tubes with optically measured radii of 37.5 and 48.6 μm.No surface viscous effects were observed with doubly distilled water or with octane, in good agreement with the Washburn equation. The behavior of a dilute aqueous solution of dodecyl sodium sulfate was easily distinguished from that corresponding to zero surface viscosities. The surface dilatational viscosity was found to be two orders of magnitude greater than the surface shear viscosity. Previous qualitative (Slattery, 1974, 1979) and quantitative (Giordano and Slattery, 1983) theories for the effect of the interfacial viscosities upon displacement are fully supported by this experimental study.
Noncatalytic coal char gasification
Authors: Lee Sunggyu , Angus J. C. , Edwards R. V. , Gardner N. C. 
Published: June 2004

AbstractA simple particle model is used to interpret differential thermogravimetric data taken on the gasification of coal/char with CO2, H2 and H2O. The model takes into account the major physical factors which influence the gasification rate, viz., the changing magnitudes of surface area, porosity, activation energy and effective diffusivity during gasification. Specific reaction rate constants based on surface area and activation energies are extracted from the data. Practical criteria for regimes of reaction rate and diffusion control and for particle isothermality are developed. For isothermal particles at low classical Thiele moduli, the data can be correlated with only one parameter, which has a simple physical interpretation.