bluuebunny/crossref_metadata_2025_split huggingface dataset:
Developed turbulent transport in ducts for large prandtl or schmidt numbers
Authors: Hanna Owen T. , Sandall Orville C. 
Published: June 2004

AbstractThe problem of developed turbulent heat or mass transfer in a duct is considered for the limit of large σ (Prandtl or Schmidt number). The limiting results depend on the behavior of the eddy diffusivity near the solid surface. Since there is a question about whether this variation begins with ϵ ∝ y+3 + … or ϵ ∝ y+4 + … for y+ near zero, both possibilities are considered. In each case the first three terms of the asymptotic expansion for σ → ∞ are obtained. The first term of the asymptotic expansion agrees with limiting results derived earlier, while the correction terms indicate the errors associated with earlier simplifying assumptions.By proper scalling, it is demonstrated that in the limit of σ → ∞ the results are independent of geometry and boundary conditions for situations involving parallel plates, circular tubes and concentric annuli with either constant surface heat flux or temperature. The correction terms to the σ → ∞ asymptote can be significant, although the effect of Reynolds number on the correction terms is very small.A comparison between a typical numerical integration and the asymptotic formula shows excellent agreement. The asymptotic formulae are used to correlate large Schmidt number mass transfer data.
Optimal design and control in a class of distributed parameter systems under uncertainty–application to tubular reactor with catalyst deactivation
Authors: Nishida N. , Ichikawa A. , Tazaki E. 
Published: June 2004

AbstractUnpredictable variations in the values of plant parameters around their nominal values are often encountered in actual operation of process plants. In order to assure that process performance meets specifications, it is preferable to design and control the process, taking into account the uncertainty in the values of the plant parameters. In this paper, a method to minimize the maximum decrease in the process performance caused by the hypothetical worst parameter variations is proposed. Necessary condition for the worst parameter variations is derived for a class of distributed parameter systems by means of the maximum principle, and then the method for obtaining the optimal design and control subject to the worst parameter variations are discussed. The method is applied to the design of a tubular reactor associated with catalyst activity decay. The reactor obtained is fairly insensitive to the variations in the process parameters while maintaining fairly good performance even at the nominal values of parameters.
The dynamics of a packed gas absorber by the pulse response technique
Authors: Sakata Norihiko , Prados John W. 
Published: June 2004

AbstractThe dynamic response of a packed gas absorber to inlet gas composition changes was investigated by the pulse response technique for the case where absorption was accompanied by pseudo first‐order irreversible chemical raction.The solute‐carrier‐solvent system was carbon dioxide‐air‐0.07 normal aqueous sodium hydroxide solution. The column used was 6.5 in. I.D. Plexiglass packed to a height of 6.15 ft. with either ¼‐in. Raschig rings or ¾‐in. Berl Saddles. Gas flow rates ranged from 1.5 to 10 lb.‐moles/hr./sq.ft. and liquid flow rates ranged from 0 to 200 lb.‐moles/hr./sq.ft. A pulse of carbon dioxide was injected into the inlet air stream and monitored as it entered the packed section. The outlet gas and liquid phase concentrations were continuously monitored as the resulting pulses left the packed section. The pulse response data were reduced to frequency response by digital computer calculations. Reliable data could be obtained over the frequncy range 0 to 5 radians/second.The experimental results were compared with theoretical predictions from the slug flow, axial diffusion, and mixing cell models. Both the mixing cell model and the axial diffusion model satisfactorily predicted the experimental frequency responses over the entire frequency range covered. The slug flow model was found unsatisfactory for predicting gas‐phase amplitude ratios at high frequencies, where axial mixing affected the amplitude ratios. Gas‐phase particle Peclet numbers and overall mass transfer coefficients based on the gas‐phase driving force determined in the present absorption system were in reasonable agreement with the values reported in the literature.
Kinetics of anion exchange accompanied by fast irreversible reaction
Authors: Graham E. E. , Dranoff J. S. 
Published: June 2004

AbstractThe kinetics of binary anion exchange accompained by a fast irreversible reaction at the exchanger surface was studied. Dowex 1, X‐8, in the hydroxyl form was contacted with a strong acid in a well‐stirred batch reactor and concentration‐time data were obtained by electrical conductivity measurements. The process was analyzed assuming rate control by film diffusion, intraparticle diffusion, and a combination of both mechanisms. The results indicated that models based on the individual mechanisms gave quite satisfactory representations of the data under appropriate conditions, but the combined model appears superior in the nominally intraparticle diffusion controlled range. It was also found that severe particle cracking occurs, particularly with larger resin particles, at high solution concentrations. This results in degradation of the particles as well as apparent intraparticle diffusion coefficients that vary during the exchange process. Care must be taken to avoid or to account for this phenomenon.
The kinetics of alkylation of isobutane with propylene
Authors: Langley J. Randolph , Pike Ralph W. 
Published: June 2004

AbstractA 17‐reaction mechanism model was postulated to describe the alkylation of isobutane with propylene using sulfuric acid as the catalyst. The scheme was based on the Schmerling carbonium ion mechanism with modifications introduced to account to iC9 and iC10 formation. Solving the steady state rate equations for the rate constants a set of 17 equations of the form ki = f(rcj, rC k, …)/g (Ci, Ck, …) were obtained. Experimental measurements were made in an ideally mixed, continuous‐flow stirred‐tank reactor, and the necessary data were obtained to compute the rate constants from 65°F to 135°F. The reaction model was found to be valid in the range of 81°F to 135°F using a 95% sulfuric acid catalyst since the rate constants obeyed the Arrhenius theory. The results obtained at 65°F and 95% sulfuric acid showed significant departure from the model. This was possibly due to a change in reaction mechanism. There was an apparent change in selectivity of the catalyst when the concentration was lowered to 90% sulfuric acid. This resulted in increased rates of formation of iC9's and iC10's and decreased rates of formation of iC5's, iC6's and iC8's.
Kinetics of water vapor sorption in a model freeze‐dried food
Authors: Bluestein P. M. , Labuza T. P. 
Published: June 2004

AbstractSorption kinetics experiments were performed at 37 C with microcrystalline cellulose held between dryness and 51% water activity in the absence of other gases. Effective diffusion coefficients (<10−4 cm2/s) were greater than any previously reported for similar experiments. A model based on heat and mass transfer properties of the sample is proposed. The vapor space permeability calculated by application of this model is related to the structure of the microcrystalline cellulose as determined from water desorption isotherm analysis, mercury intrusion porosimetry, and steady state permeability techniques. Microcrystalline cellulose, like some freeze‐dried foods, contains micropores and macropores. During sorption, the macropores are important in determining the balance between the internal and environmental control during the first half of sorption. The micropores, which account for less than 1% of the void volume of the porous matrix but approximately 40% of the surface area, control the mass transfer properties of the sample during the latter stages of sorption. Because of the great difference between their mass transfer properties, the macropores approach local equilibrium faster than the micropores; this phenomenon suggests that changes in the effective diffusion coefficient and permeability as sorption proceeds are related to the structure of the sample rather than to the moisture content itself.
Liquid sorption equilibria of selected binary hydrocarbon systems in type Y zeolites
Authors: Satterfield Charles N. , Cheng Chon S. 
Published: June 2004

AbstractOn NaY and HY, aromatic compounds are selectively adsorbed in preference to paraffins and naphthenes. Smaller aromatic compounds are adsorbed in preference to larger aromatic compounds. All the compounds studied can be sorbed into the pore structure of the zeolites and the selectivies are primarily a reflection of relative affinity for the zeolite and steric effects rather than a sieving effect.
An integral analysis of condensing annular‐mist flow
Authors: Berry Maurice R. , Goss William P. 
Published: June 2004

AbstractThe application of integral techniques to the analysis of a high vapor velocity, two‐phase, annular‐mist, single‐component condensing flow system is presented. A time‐averaged annular liquid film thickness is defined, and appropriate interfacial and wall shear stress correlations are employed to account for the wavy nature of the interface between the entrainment‐laden gaseous core and the axisymmetric annular liquid film. An empirical entrainment correlation is utilized to determine the amount of liquid flowing as entrained particles in the high velocity core region. The velocity and enthalpy distributions in the gaseous core and the annular liquid film are assumed as the power‐law type. The resulting set of four nonlinear ordinary differential equations is solved numerically with the use of a digital computer. A comparison with experimental data for condensing steam is obtained. The analytical model accurately predicts the condenser length necessary for complete condensation and also predicts the dynamic quality, the heat transfer characteristics, and the static pressure distribution throughout the condensation length. The integral analysis presents some insight into the complex mechanisms and interactions which occur in high vapor velocity, two‐phase, annular‐mist flows and also indicates the need for improved experimental techniques to further this understanding.
Convective instability in the presence of a catalytic chemical reaction: Part II. Oscillatory instability
Authors: Wankat P. C. , Schowalter W. R. 
Published: June 2004

AbstractThis is an extension of earlier work in which a linear analysis of hydrodynamic stability was applied to a fluid mixture contained between two horizontal planes. One species diffuses to the lower plane where it is destroyed by a rapid exothermic or endothermic catalytic reaction. In the present work, Galerkin's method has been used to study the importance of oscillatory instability in a system with the more dense species concentrated near the top plane. Results show that, for cases likely to be of physical interest, oscillatory instabilities are not expected.
The computation of optimal singular bang‐bang control I: Linear systems
Authors: Edgar T. F. , Lapidus L. 
Published: June 2004

AbstractA general algorithm for the solution of both singular and bang‐bang control problems is presented. The algorithm utilizes a limiting process and the solution of a constrained linear‐quadratic control problem. The algorithm is applied to problems with both fixed and nonfixed final times. General numerical results for several linear system examples are presented, and two minimum time examples are discussed in detail.
Coupled heat and mass transport in unsteady sublimation drying
Authors: Fox E. C. , Thomson W. J. 
Published: June 2004

AbstractSublimation drying is analyzed by considering coupled heat and mass transport at the ice‐vapor interface. Since, the typical model of sublimation drying assumes a pseudo steady state heat transport limited process, these assumptions are critically analyzed to determine whether they are the cause of some of the limitations of the simplified model. It is shown that although total drying times can be substantially increased if there is heat leakage into the ice core and coupled heat and mass transport, this is not a problem in the conventional sublimation drying of foods. However, the results indicate that consideration of both coupled transport and heat leakage into the core result in time‐varying ice temperatures which could exceed the triple point. In addition, the application of this analysis to the analogous heterogeneous chemical reaction problem is pointed out and appropriate conclusions can be drawn by inference.
Accelerating diffusion with mixed solvents
Authors: Cussler E. L. , Breuer M. M. 
Published: June 2004

AbstractThe experiments reported here show how diffusion rates in liquids can be increased by as much as an order of magnitude by use of coupled diffusion fluxes in mixed solvents. Solutes whose diffusion can be accelerated in this way include simple electrolytes, essential oils, dyes, and antibiotics. These increases are primarily caused by thermodynamic interactions and can be estimated from solubilities.
Salt effect in vapor‐liquid equilibria: Correlation of alcohol‐, water‐, salt systems
Authors: Rousseau R. W. , Ashcraft D. L. , Schoenborn E. M. 
Published: June 2004

AbstractThe isobaric data of Johnson and Further for the systems methanol‐water, ethanol‐water, and 1‐propanol water, each saturated with a variety of common inorganic salts, can be effectively correlated by means of the van Laar, the Wilson, or the Renon equations if pseudo‐activity coefficients for the volatile components are computed using a modified reference fugacity for the liquid phase. This reference fugacity takes into account the lowring of the vapor pressure due to the dissolved salt. Furthermore, the activity coefficients are normalized as required by the above equations.
The extraction of mercuric chloride from acid chloride solutions with trioctylamine
Authors: Caban Reinaldo , Chapman Thomas W. 
Published: June 2004

AbstractThe equilibrium distribution of mercuric chloride between aqueous sodium chloride solutions and a solution of tri‐isooctylamine in xylene has been measured. The dependence on pH, amine concentration, mercury level, and temperature has been determined. At low pH mercury is extracted quite effectively with a distribution coefficient as high as 2,000. At high pH the mercury can be stripped from the organic solution. This extraction system offers the possibility of an effective mercury separation process for chlorine plant brines or chloride‐based mercury leach liquors.A theoretical model of the extraction equilibria is developed to facilitate interpolation of the experimental data.
Mass transfer into dilute polymeric solutions
Authors: Wasan D. T. , Lynch M. A. , Chad K. J. , Srinivasan N. 
Published: June 2004

AbstractMass transfer into dilute polymeric solutions was studied by using a short wetted‐wall column. Oxygen was absorbed into thin films of water and aqueous polymeric solutions. The polymer systems studied included dilute solutions of carboxymethylcellulose, polyethylene oxide, Carbopol, and Cyanamer. All of the above systems were moderately non‐Newtonian with power law indexes less than unity. Methocel (a Newtonian fluid with a power law index of one) was also studied. The flow of liquid films was well within the laminar flow regime.The rheological properties of these solutions as well as equilibrium solubility of oxygen in these solutions were determined. In all of the polymer systems studied except Polyox the equilibrium so ubility of oxygen decreased with an increase in polymer concentration. In Polyox solutions, however, the equilibrium solubility of oxygen increased with an increase in polymer concentration.For all of the systems investigated (including Polyox) the mass transfer coefficient for absorption of oxygen at a given flow rate decreased with an increase in polymer concentration. The mass transfer coefficient was highest for water at all flow rates.The diffusivity of oxygen in all of the systems considered except Polyox was lower than that in water. This was attributed to the increased viscosity of the polymeric solutions. The diffusivity of oxygen in Polyox solutions was higher than it was in water. This was found to be due to the complex chemical reactions which occur in this system. In all of the pseudoplastic systems studied the diffusivity of oxygen increased with increasing wall shear rate (decreasing viscosity).
The wetting behavior of azeotropic systems at atmospheric and reduced pressures
Authors: Boyes Adrian P. , Ponter Anthony B. 
Published: June 2004

AbstractContact angles are reported for the azeotropic systems n‐propanol‐water and benzene‐cyclohexane measured under distillation conditions at total reflux over a pressure range 50 to 760 torr on both copper and polytetrafluoroethylene surfaces. The influences of the solid surfaces, the surface tension positive and negative nature of the liquids, together with the changes accompanying the azeotropic shift with pressure on the wettability, have been established and shown to conform with wetting theory.
Mass transfer to a rotating fluid. Part II. Transport from the base of an agitated cylindrical tank
Authors: Colton Clark K. , Smith Kenneth A. 
Published: June 2004

AbstractMass transfer to the base of an unbaffled cylindrical tank which is agitated by an axially‐mounted impeller is studied experimentally and theoretically. Measured local mass transfer coefficients vary with radial position and fall within theoretical bounds derived for the case of a fluid undergoing solid body rotation above the boundary layer on the base. Average mass transfer coefficients and torque delivered to the base are fitted by consistent theoretical expressions, and an empirical correlation is developed for calculating the average liquid phase mass transfer coefficient.
Precipitate coflotation of orthophosphate and fluoride
Authors: Bhattacharyya Dibakar , Romans John D. , Grieves Robert B. 
Published: June 2004

AbstractOrthophosphate and fluoride are simultaneously precipitated from aqueous solution, 5.26 × 10−3 M. in each, by La (III). The precipitates are cofloated by the anionic surfactant sodium laurylsulfate, with optimum flotation at pH 4.0 and a stoichiometric lanthanum concentration based on LaPO4 and LaF3. Over pH 3.5 to 6.0, better than 95% flotation of the total orthophosphate and precipitated fluoride that‐are present can be floated at a molar sodium laurylsulfate to orthophosphate plus fluoride ratio of 0.023. At lower sodium laurylsulfate concentrations, the flotation decreases at pH 3.5 and 6.0 compared to pH 4.0–5.0; at pH 4.0, an increase in the La(III) concentration decreases the flotation.
Error bounds for approximate solutions to nonlinear ordinary differential equations
Authors: Ferguson Noble B. , Finlayson Bruce A. 
Published: June 2004

AbstractError bounds are provided for approximate solution of systems of nonlinear ordinary differential equations for cases where there is no known exact solution for comparison. Theorems are proved for problems of heat and mass transfer of a multicomponent system in catalyst particles under going chemical reaction. Error bounds are provided for the pointwise error as well as the effectiveness factor. Calculations based on the theorems show the orthogonal collocation method can give results which are proved accurate to 12 digits, thus providing essentially the exact solution. For problems for which the theorems have not yet been proved, the results suggest that the mean‐squared residual gives a good indication of the accuracy since the error decreases as the mean‐squared residual decreases.
Interfacial instability and spontaneous formation of microemulsions
Authors: Shah D. O. , Tamjeedi A. , Falco J. W. , Walker R. D. 
Published: June 2004

AbstractMicroemulsions, which are optically transparent oil‐water dispersions, were spontaneously produced upon mixing hexadecane, hexanol, potassium oleate, and water in specific proportions. The drop‐volume measurements of hexadecane‐water interface in the presence of hexanol or potassium oleate revealed that these surfactants decrease the interracial tension of the hexadecane/water interface. It is proposed that the interaction between these two emulsifiers at the oil‐water interface causes spontaneous negative interfaical tension resulting in interfacial instability and the formation of microemulsions.As the amount of water is increased, the microemulsion exhibits a clear to turbid to clear transition. Unlike the clear regions, the turbid region possesses birefringence. The development of birefringence is also accompanied by a sharp decrease in electrical resistance. High‐resolution (220 Mc) nuclear magnetic resonance data suggest that water exists in two distinct environments or structures in the birefringent region. The electrical, birefringence, and nuclear magnetic resonance data agree with the proposed mechanism of phase‐inversion of microemulsions, which can be described as water spheres to water cylinders to water lamellae to a continuous water phase. The spontaneous formation of such structures (for example, water cylinders and lamellae) presumably depends upon the phase‐volume ratio and the interfacial tension at the oil‐water interface.
Fixed bed desorption behavior of gases with non‐linear equilibria: Part I. Dilute, one component, isothermal systems
Authors: Zwiebel Imre , Gariepy Roger L. , Schnitzer Jay J. 
Published: June 2004

AbstractGeneralized depletion curves for desorption (and breakthrough curves for adsorption) were calculated for a system characterized by the Langmuirtype equilibria and controlled by a film type rate model. The depletion points generally appear sooner than the corresponding breakthrough points, and the desorption profiles are significantly broader than the corresponding adsorption curves. These phenomena may be best explained in terms of the prevailing driving forces. The effects of adsorbate properties and operating variables (inlet composition and flow rate) were established and experimentally substantiated.
Finite element analysis of two‐dimensional slow non‐newtonian flows
Authors: Palit Kalipada , Fenner Roger T. 
Published: June 2004

AbstractA finite element method is applied to isothermal incompressible two‐dimensional slow flows of power‐law fluids. Examples considered are rectangular and axisymmetric converging channel flows, recirculating flows in rectangular channels, and flow round cylinders. Results are successfully compared with both finite difference and analytical solutions. The flexibility of finite element methods makes them very suitable for problems involving complex boundary geometries. The method used is particularly suitable for non‐Newtonian flows and can treat both rectangular and axisymmetric geometries.
Computation of vapor liquid equilibria for hydrogen and light hydrocarbon systems
Authors: Singh Surendra P. , Mukhopadhyay Pranab K. 
Published: June 2004

AbstractGeneralized expressions are presented for Henry's constants and self‐interaction constants required in the Chueh‐Prausnitz method for predicting the vapor‐liquid equilibria for hydrogen and light hydrocarbon systems, The K‐values calculated using the above correlations were compared with the K‐values obtained from the published experimental data in the teperature range of 117 to 422°K. The statistical analysis shows that the cal‐ culated values are about as reliable as the experimental results.