bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improvement of mass transfer coefficient in reverse osmosis by oscillatory flow
Authors: Thayer W. L. , Pageau Lucien , Sourirajan S. 
Published: March 2009

AbstractThis paper describes a laboratory apparatus for confined feed liquid reverse osmosis operation. In this apparatus, the mass transfer coefficient on the high pressure side of the membrane is increased by sweeping the membrane surface at a predetermined frequency by a back and forth movement of the feed liquid itself through an adjustable narrow channel in the cell. The utility of the technique for improving membrane performance is illustrated.
A generalised approach to the fluid dynamics of particulate systems part 2: Sedimentation and fluidisation of clouds of spherical liquid drops
Authors: Barnea E. , Mizrahi J. 
Published: March 2009

AbstractIn a recently published paper(1), it has been demonstrated that the drag coefficient—Reynolds number relationship for a single spherical solid particle may be applied to multi‐particle systems as well, provided that modified definitions of the drag coefficient and Reynolds number incorporating suitable functions of the particles volume fraction are used.This generalised approach is now extended to include the case of a fluid dispersed phase. This done by incorporating a function of the ratio of the phase viscosities, based on theoretical derivations due to Hadamard—Rybczinski and Taylor in the modified definition of Reynolds number.All available experimental data (88 points from 3 sources, on 12 different liquid‐liquid systems) were recalculated and correlated on this basis.
Absorption with first order chemical reaction into turbulently flowing liquids
Authors: Stepanek J. B. , Achwal S. K. 
Published: March 2009

AbstractThe damped turbulence model has been applied to the problem of absorption with a first order chemical reaction through a gas‐liquid interface into a turbulently flowing liquid. An analytical solution has been obtained in terms of Gauss hypergeometric functions. A further investigation has shown that the solution is fairly insensitive to the boundary condition inside the liquid phase. A simpler solution has also been obtained with a negligible loss of accuracy.
Synthesis of optimal process flowsheets by an infeasible decomposition technique in the presence of functional non‐convexities
Authors: Stephanopoulos George , Westerberg Arthur W. 
Published: March 2009

AbstractAn infeasible decomposition method based on the two‐level optimization procedure is proposed for the structural parameter method for synthesis of optimal process flowsheets. A penalty term is used to guarantee the success of the method in the presence of functional non‐convexities very often encountered in chemical process design. The convergence characteristics of the primal and dual problems have been considered and a computational procedure which will enhance the convergence rates for both problems is proposed. The use of the suggested strategy is illustrated in the synthesis of a simple reactor‐separator system.
The effect of line length for inclined slurry pipelines at shutdown
Authors: Shook C. A. , Mcleod D. J. 
Published: March 2009

AbstractThe behaviour of inclined slurry pipelines at shutdown was studied using different active lengths of pipe. The ultimate settled condition was found to depend on pipe slope in the same fashion as for much shorter pipes. Pressure changes observed at the bottom of the slope gave a good indication of the time scale of the settling/flow process. A preliminary interpretation of the process is provided by a model in which inertial forces, compressibility effects and axial variations of velocities are neglected.
Radial liquid distribution in cocurrent two‐phase downflow in packed beds
Authors: Sylvester Nicholas D. , Pitayagulsarn Punya 
Published: March 2009

AbstractRadial liquid distribution was measured experimentally for cocurrent, two‐phase downflow in packed beds. The effects of bed length, water and air flow rates, and type of packing were determined. The experimental data were obtained in the gas‐continuous, transition and pulsing trickling‐flow regimes. For all finite air rates, the liquid velocity profiles were approximately flat with the maximum average velocity occurring at the center of the packed column. Increasing the air rate increased the center liquid velocity. The gas rate effect was more pronounced in shorter beds. At higher gas rates the liquid rate had less effect on the radial liquid distribution than at lower gas rates. Operation at higher liquid rates resulted in a flatter radial liquid veilocity profile. It was observed that the bed of pellets operated at high liquid rate and low gas rate was unstable. Increasing the bed height increased the stability of the system and a better liquid distribution was obtained. The effects of water flow rate, bed length, and packing type on the shape of the liquid velocity profiles were minor.
A study of the combined effects of kinetic parameters and flow models on conversions for second order reactions
Authors: Lindfors Lars‐Eric 
Published: March 2009

AbstractThe present paper is a study of the interplay between kinetic parameters and different flow patterns and its effect on fractional conversions for second order reactions with arbitrary stoichiometry and arbitrary ratios between the initial concentrations of the reactants. The models studied are the normal, segregated and maximum‐mixed axial dispersion and tanks‐in‐series models. The calculations required have been performed with the aid of digital simulation and the results are presented in diagrams making possible the determination of the fractional conversion for ten different models.When plotted as a function of a reaction rate group the absolute value of the difference between the conversions for the normal and segregated models always attains its highest value for the limiting model represented by complete backmixing, while this difference is zero for the opposite limiting model, i.e. plug flow. In the case of maximum‐mixed and normal models this difference attains its highest value between plug flow and complete backmixing, but the exact value is dependent on other parameter values. The diagrams indicate that it is more important to choose the proper model for certain parameter combinations than for others: the maximum difference between the conversions for different models is about 8%; the lowest is zero.
Effects of charge stock composition on selectivity in the cracking of neutral distillates
Authors: Pachovsky Roman A. , Wojciechowski Bohdan W. 
Published: March 2009

AbstractGasoline selectivity in the catalytic cracking of four neutral distillates, varying only in wax content, has been studied over a range of temperatures. It has been found that the cracking rate constants leading to gasoline and to undesirable products, as well as the gasoline recracking rate constant, increase linearly with the mole fraction of wax in the feed. At the same time the activation energies for the primary rate constants decrease with increasing wax content of the feed, while the activation energy for gasoline recracking is not affected by feed composition.We also find that the various components of the feed crack quite independently of one another and do not interact in any way. There appears to be no synergistic interactions between the wax‐free fraction and the wax in the feed.In spite of the large difference between reaction rate constants reported here and those previously reported for the cracking of a mid‐continent gas oil by Pachovsky and Wojciechowski16, the Optimum Performance Envelopes for all the chargestocks we have studied are very similar. Our results indicate that the major differences between gas oils we have studied lie in their “reactivity”; in other words, in their relative rates of conversion at a given set of conditions.
On fluidized bed‐to‐surface heat transfer
Authors: Zabrodsky S. S. , Antonishin N. V. , Parnas A. L. 
Published: March 2009

AbstractDevelopment of new techniques has stimulated new interest in fluidized bed‐to‐surface heat transfer phenomena. In this paper a short critical review of major recent works on the subject as well as comments on the validity of some general concepts and of “small scale” equations available are presented. It appears that these concepts can serve as a basis for future development of reliable design equations for large commercial equipment and for analysis of its performance. Examples of the analysis of imperfectly understood observations are presented.
The measurement and prediction of temperatures at the free interface of falling water films under heat transfer
Authors: Borodin A. S. , Picot J. J. C. 
Published: March 2009

AbstractThis paper describes an experimental measurement of temperatures at the free liquid interface of distilled water films falling vertically downwards on the outside surface of a copper tube heated internally by a countercurrent circulating liquid. An infrared radiometer was used for the temperature measurements. A prediction for these temperatures is made by solving numerically the governing equations of momentum, continuity and energy. Experimentally estimated temperature profiles were employed as the wall temperature boundary conditions. Internal turbulence eddies and surface wave celerity were considered in the numerical solution by using the eddy diffusivity profile of Mills and Chung. Good agreement between experiment and theory was obtained
Effect of axial dispersion on interphase mass transfer in packed absorption columns
Authors: Mathur V. K. , Wellek R. M. 
Published: March 2009

AbstractGas phase axial mixing parameters and interphase mass transfer coefficients were determined simultaneously for gas‐liquid flow in a packed column. It was found that axial mixing in the gas phase increases with increases in liquid flow rate, packing size, and packing height. The behavior of apparent and true mass transfer coefficients indicates a decrease in axial mixing with increases in gas flow rates. Gas phase Peclet numbers obtained were about two to three times greater than reported than reported by workers using transient tracer techniques under similar conditions. Correlations for apparent and true overall liquid phase mass transfer coefficients are presented.
Analytical approximate solutions for simultaneous absorption with reaction
Authors: Sada Eizo , Kumazawa Hidehiro , Butt M. A. 
Published: March 2009

AbstractAn analytical approximate solution for simultaneous absorption of two reacting gases into an inert liquid is presented assuming a non‐linear concentration profile for gaseous species A. The approximate enhancement factors of A and B show a closer agreement with the exact enhancement factors on the basis of film theory than do those in any existing paper. The same suggested concentration profile is successfully applied to the problems of simultaneous absorption of two reacting gases in a reactive liquid and of three reacting gases in an inert liquid.
Hydrodynamic study of gas and solid flow through a screen‐packing
Authors: Claus G. , Vergnes F. , Goff P. Le 
Published: March 2009

AbstractMany drawbacks of conventional gas fluidized beds can be avoided by filling the column with a fixed wire‐screen Raschig ring packing of high voidage. Such systems have been studied in batch and countercurrent continuous mode. Excellent fluidization occurs with relatively coarse particles but not with smaller particles. In batch systems, the expansion is given by a Capes and McIlhinney type power law and the contribution of the packing to support the bed can be up 20 percent of the weight of solid. In countercurrent systems, for each gas velocity two operating points can occur: the dilute or the dense phase bed in the same way as for gas liquid flow. All increases in the flow of the solid or in the dilution of the bed lead the packing to support a greater part of the grains.
An investigation of the operating parameters of a low energy wet scrubber for fine particulates
Authors: Douglas P. L. , Dullien F. A. L. , Spink D. R. 
Published: March 2009

AbstractTests performed on an inexpensive, low energy wet scrubber are described. The device employs a centrifugal fan, operated at 550–750 rpm, and co‐current spray nozzles producing a relatively fine spray, from 20μ to 180μ. The fan acts as the prime mover of air, as contacting device, agglomerator, and precipitator. Variations in the scrubber's collection efficiency with changes in fan speed, water flow rate, nozzle position and with particle size in the range 0.1–3μ. have been studied.
An experimental study of mass transfer in rotating couette flow with low axial reynolds number
Authors: Strong A.B. , Carlucci L. 
Published: March 2009

AbstractAn experimental investigation has been undertaken to determine the oxygen transfer rate of a rotating Couette flow oxygenator for low axial annular flow rates. The purpose of this study was to determine if such a device might provide a rational basis for the subsequent design of a blood oxygenator for respiratory support in clinical situations. Using oxygen and degassed water as an analog to oxygen and blood the Sherwood number was determined as a function of the axial Reynolds number and the Taylor number. Results show that oxygen transfer rates can be enhanced by at least ten times over that of the non‐rotating situation, the flow being laminar with vortex flow superposed. The present results were correlated as Sh vs. Ta/Tac over the range of parameters studied.
An investigation of oxygen transfer rates to flowing films of various electrolyte solutions
Authors: Raymond Dale R. , Zieminski Stefan A. 
Published: March 2009

AbstractIn this work the mass transfer coefficient for the absorption of oxygen was measured for solutions of K2SO4, (NH4)2SO4, Na2SO4, MgSO4, MnSO4, Al2(SO4)3, NaCl, AlC13 under conditions of nearly horizontal, thin, essentially laminar, flowing films. The results showed a systematically ordered dependence of the mass transfer coefficient on the hydration where the values of the mass transfer coefficient decrease with the decreasing entropy. This effect becomes progressively more pronounced with increasing charge of the cations. Finally, although the entropy of hydration has a strong influence on the changes in the coefficient, it does not have a common linear relationship for the investigated ions.
PVT study of trifluoromethane by the burnett method
Authors: Belzile J. L. , Kaliaguine S. , Ramalho R. S. 
Published: March 2009

AbstractPVT data for trifluoromethane were obtained by means of a three‐reservoir Burnett cell. Compressibility factors corresponding to seven isotherms (0, 25, 50, 75, 100, 150 and 200°C) were obtained experimentally, encompassing pressures up to 16.5 MPa (2,400 psia). Second and third virial coefficients were calculated for these seven temperatures, and parameters for the Stockmayer potential functions were obtained. The degree of molecular association for trifluoromethane was evaluated by the procedure proposed by Lambert and coworkers. Enthalpy and entropy of dimerization were also estimated.
Interfacial viscoelastic properties of adsorbed surfactant and polymeric films at fluid interfaces
Authors: Mohan V. , Malviya B. K. , Wasan D. T. 
Published: March 2009

AbstractThe viscous and elastic properties of fluid interfaces play an important role in the stability of foams and emulsions as well as in the selection of surfactants for tertiary oil recovery. These properties were determined for aqueous solutions of surfactant, polymer, and polymer plus surfactant systems using a deep channel surface viscometer. The surface rheology of the adsorbed film was represented in terms of the two‐parameter Maxwell model. Depending on the system investigated, the films were found to be either viscoelastic, purely viscous, neither viscous nor elastic, or rigid.
The role of paraffin wax in the formation of minor products in the catalytic cracking of petroleum distillates over la‐y
Authors: John Thomas M. , Wojciechowski Bohdan W. 
Published: March 2009

AbstractAn investigation of the role of paraffin wax in the catalytic cracking of wax‐bearing petroleum distillates has been carried out in a fixed‐bed reactor containing La‐Y catalyst over a temperature range from 482° to 524°C.By using the concept of initial product selectivity derived from the time‐on‐stream theory of catalyst decay, it was found that increasing the wax content of the feedstocks resulted in an increase in the yield of C5+ gasoline and a decrease in the yields of most of the gaseous products and of coke. Ethane and propylene and the olefin content of the gasoline increased in yield with the addition of wax. The mixing of cracking feedstocks has only a linear effect on the reactivity and no synergistic effects in any of the observed properties of the reaction are in fact observed.
Additivity rules for the prediction of the density of aqueous solutions containing mixed‐type solutes
Authors: Teng Tjoon‐Tow , Sangster James , Lenzi Fabio 
Published: March 2009

AbstractDensities of ternary aqueous solutions of mixed‐type solutes have been measured at 25°C to high concentration. Two methods, the one isopycnotic (same density) and the other based on ionic strength, have been used to predict the densities of these solutions. The isopycnotic method proved to be the more accurate.The two methods have been applied in reverse to calculate densities of supersaturated binary aqueous solutions of NaCl and KCl. The methods give concordant results for each salt Deviation parameters for the methods are presented, with a discussion of their use.
Optimal inlet temperature control of reactors with catalyst decay
Authors: Gruyaert F. , Crowe C. M. 
Published: March 2009

AbstractThe constant conversion policy which has been shown to be optimal in certain classes of optimal control problems for reactors with decaying catalyst is examined here for the inlet temperature control in a tubular reactor where the catalyst decay is a function of the composition. A single irreversible reaction is considered where the rate expression is a product of separate functions of temperature, concentration or conversion and catalyst activity. The catalyst decay rate expression is also a product of separate functions of the same variables. A proof of the constant exit conversion property is given for problems where the decay rate is of first‐order with respect to the catalyst activity.
Bubble swarm characteristics in bubble columns
Authors: Kumar Akhilesh , Degaleesan T. E. , Laddha G. S. , Hoelscher H. E. 
Published: March 2009

AbstractNew correlations have been proposed for estimation of gas phase holdup, characteristic velocity, interfacial area for mass transfer and mean bubble size of bubble swarms under dispersed and fluidized operation of bubble columns employing single — and multi‐orifice distributors. The analysis of results include available literature data of other investigators.
Low peclet number heat transfer in the thermal entrance region of parallel‐plate channels with unequal wall temperatures
Authors: Wu Ray‐shing , Cheng K. C. , Ou Jenn‐Wuu 
Published: March 2009

AbstractThe problem of low‐Peclet‐number thermal entry heat transfer for plane Poiseuille flow in parallel‐plate channels with uniform but unequal wall temperatures is approached by the eigenfunction expansion method utilizing the Gram‐Schmidt orthonormalization procedure. The formulation considers axial heat conduction and allows upstream heat penetration through the thermal entrance. Numerical results are obtained for the case with entrance condition parameter θ0 = 1 and Peclet number Pe = 1, 5, 10 and 50. The effect of Peclet number on temperature distributions in both upstream and downstream regions is studied. At Pe = 50, the concept of thermal boundary layer is applicable and the present series solution does not yield physically reasonable temperature distribution locally near the upper plate at the thermal entrance. The difficulty may be attributed to the nature of thermal boundary conditions at the thermal entrance and the transition from elliptic problem to parabolic problem with the increase of Peclet number.
Rising behavior of air bubbles in superposed liquid layers
Authors: Mori Yasuhiko H. , Komotori Kazunari , Higeta Kazuya , Inada Junji 
Published: March 2009

AbstractAn air bubble that passes through a horizontal interface from a lower layer of Freon‐113 to an upper layer of aqueous glycerol forms a two‐phase bubble in the upper layer as a result of entrainment of a certain volume of Freon‐113 from the lower layer. The volume of entrained Freon‐113 and the rise velocity of such a two‐phase bubble have been measured. The former increases with an increase of the bubble size irrespective of the viscosity of the upper liquid. The latter is somewhat lower than that of a normal air bubble of the same size.
Comparison of methods for measuring interfacial areas in gas‐liquid dispersions
Authors: Landau J. , Boyle J. , Gomaa H. G. , Al Taweel A. M. 
Published: March 2009

AbstractInterfacial areas were determined for gas‐liquid systems in a column with transparent walls by the chemical and two physical methods: photography and light attenuation. The advantages of the different methods are discussed and improvements in the physical methods are described. By using a Data Tablet Digitizer, the photographic technique provides additional information on the gas dispersion without increasing the amount of work needed for analysis of the photographs. Use of the light attenuation technique is extended to conditions when multiple scattering and stray light must be taken into account; it can then be used up to values of optical path densities equal to 80.
An explanation for an apparent failure of the box‐hill procedure for model discrimination
Authors: Bajramovic R. , Reilly Park M. 
Published: March 2009

AbstractFroment and Mezaki made an early attempt to verify, by using real experimental results, that the Box‐Hill procedure could accomplish more efficient model discrimination than less sophisticated procedures. They found rapid convergence but the conclusion varied, depending on the conditions of the initial experimental trials. In attempting to remedy this inconsistency several workers have found changes in the Box‐Hill method which can eliminate it. In this investigation an explanation of the failure is sought and found in terms of the requirements of the method. It is shown that direct application of the unmodified procedure is successful if the dependent variable is chosen so as to minimize the effect of errors in the independent variables even though this means changing the form of the model from linear to nonlinear in the parameters.
Heat transfer to laminar flow with temperature — dependent heat generation
Authors: Mori S. , Inoue T. , Tanimoto A. 
Published: March 2009

AbstractTwo problems were solved theoretically on the heat transfer to circular tube flow with internal heat source. The one problem is to maintain the mixed‐mean temperature of fluid at the inlet temperature. The other is a conjugated problem with a uniformly specified temperature at the outside surface of the wall, accounting for the wall conduction.From the numerical example for the former, it is shown that the mixed‐mean temperature can be controlled within 15% error under the estimated condition.From the numerical results for the latter, it is concluded that the influence of wall conduction is more serious than the case without heat generation.
Continuous multi‐particle crystal growth in vertical cones
Authors: Ishii Tsutomu , Fujita S. , Johnson A. I. 
Published: March 2009

AbstractEquations of continuity and motion for dispersed two‐phase flow with phase growth are derived and a one‐dimensional steady state solution of these equations is obtained for the design and operation of a vertical cone as a continuous crystallizer. This solution is verified by semi‐continuous and continuous crystal growth experiments. Cones having divergence angles below about 7° were found to be suitable as continuous classifying crystallizers and an approximate flooding range was found.