bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tube‐wall catalytic reactor cooled by an annular heat pipe
Authors: Parent Y. O. , Caram H. S. , Coughlin R. W. 
Published: June 2004

AbstractCooling a tube‐wall reactor using an annular heat pipe (AHP) is more temperature‐stable, more flexible and more productive than cooling by conventional means. Tube‐wall reactors cooled by an annular heat pipe arrangement exhibit flatter temperature profiles and uniform redistribution of the imposed heat load. The combination of tube‐wall reactor and annular heat pipe is subject to the usual capacity limitations of the heat pipe: sonic flow, boiling heat transfer, liquid entrainment, and capillary flow of the working fluid.
Combustion of carbon residue from oil shale retorting
Authors: Hiskakis Miltiadis , Hanratty T. J. 
Published: June 2004

AbstractThe combustion of a bed of particles impregnated with carbon is considered. An analysis is developed for the combustion wave after it has progressed some distance into the bed. It is shown that the calculations are considerably simplified by choosing a coordinate system that moves with the combustion wave and by neglecting dispersion of heat or mass.
Multiplicity criteria for multireaction networks
Authors: Balakotaiah Vemuri , Luss Dan 
Published: June 2004

AbstractA general method is developed for a systematic determination of criteria predicting steady‐state multiplicity in lumped‐parameter systems in which many irreversible reactions occur simultaneously. The method enables use of criteria derived for simple reaction networks to predict the behavior of more complex networks. The available multiplicity criteria for the single‐ and two‐reaction networks can always be used to write down sufficient multiplicity criteria for any multireaction system. Several examples illustrate the power of the proposed technique.
Diffusion of gases in porous solids: Monte Carlo simulations in the Knudsen and ordinary diffusion regimes
Authors: Abbasi M. H. , Evans J. W. , Abramson I. S. 
Published: June 2004

AbstractPorous solids have been simulated in the computer as assemblages of spheres. When such assemblages contain spheres distributed in size and randomly arranged in space, the structure of the resulting solid resembles that of a real porous solid. Monte Carlo calculations of gas molecule trajectories through the assemblages were carried out for both the Knudsen and ordinary diffusion régimes. Tortuosities calculated from the simulated diffusion “data” fell in the range obtained experimentally by other investigators. Correlations were obtained that enable the prediction of diffusion rates from measurement of the porosity, mean pore size, and standard deviation of the pore size.
Tracer diffusion in methanol, 1‐butanol and 1‐octanol from 298 to 433 K
Authors: Chen S.‐H. , Evans D. F. , Davis H. T. 
Published: June 2004

AbstractDiffusion coefficients of argon, krypton, xenon, methane, carbon tetrachloride and the tetraalkyltins (methyl through butyl) were measured in methanol, 1‐butanol and 1‐octanol over the temperature range 298 to 433 K. With temperature‐dependent solvent diameters fitted from the tracer diffusivity of one of the solutes, a rough‐hard‐sphere theory predicts well the observed tracer diffusivity over the solvent density range in which hard‐sphere computer simulations are available. The Wilke‐Chang correlation predicts diffusion coefficients in the higher alcohols with an average error of 80% and a maximum error of 200%. A correlation of the form Dμp/T = A where p and A depend on solute and solvent size is more successful giving an average error of 7% and a maximum error of 24%.
Theory of hindered sedimentation of polydisperse mixtures
Authors: Zimmels Y. 
Published: June 2004

AbstractThe theory and application of hindred sedimentation is reviewed. Polydisperse mixtures with size and density distributions are considered. A general solution technique is established for steady‐flow regimes where a standard drag correlation for monodisperse systems is applied to each component. Solutions for discrete and continuous particle‐size and density distributions are outlined. Results are presented for the sedimentation of mixtures made up of particles of uniform density and varying size suspended in a fluid with fixed properties. Under these conditions, the sedimentation velocities of the components vary significantly with the size distribution of the particles and the total volume fraction occupied by the particles In this context, topics such as maximum flux of particles, classification and density separation are considered.
Fluidized‐bed reactor model with generalized particle balances. Part I: Formulation and solution
Authors: Overturf B. W. , Reklaitis G. V. 
Published: June 2004

AbstractThe changes to the solid phase which occur within fluidized‐bed gas‐solid reactors may have a significant impact on the performance of this class of reactors, particularly in coal conversion applications. In this paper a particle balance model is developed which accommodates particle distributions dependent on both size and density as well as populations consisting of multiple solids. The fast double collocation method used for solving the associated PDE permits this calculation to be performed within the framework of a Davidson‐Harrison bubbling‐bed model. A modification of the iteration procedure for the emulsion‐phase state variables of the D‐H model is reported which allows the composite reactor model to be executed reliably and efficiently. A general purpose program has been implemented, whose application is presented in a companion paper.
Effective diffusion and conduction in two‐phase media: A unified approach
Authors: Chang Hsueh‐Chia 
Published: June 2004

AbstractA multiscale analysis based on two widely different length scales that exist instagnant two‐phase media is carried out to investigate diffusion and conduction in periodic and random systems. A variational form of the resulting unit cell equations allows one to demonstrate its equivalence to the cell equations of other independent approaches, thus unifying these widely different methods. The variational approach is also shown to facilitate numerical studies and to provide a link between random and periodic media by yielding an upper bound for the effective diffusivity in random media in terms of the periodic one.
Mobilization of oil ganglia
Authors: de la Cruz V. , Spanos T. J. T. 
Published: June 2004

AbstractFollowing secondary recovery processes in conventional light oil reservoirs, more than half the original oil in place may remain trapped as a discontinuous phase. During the previous recovery processes these oil ganglia have been pinched off by capillary forces and remain immobile while the continuous phase which surrounds them is able to flow freely. Furthermore if a portion of this oil is mobilized in a tertiary recovery process the conditions required to apply Darcy's equation to the flow of either phase are violated. These are also problems which are encountered during in‐situ recovery techniques in tar sands where the mobilization of the heavy oil occurs as a discontinuous phase. In this paper the relevant flow equations are derived. Also a parameter is deduced which directly determines the criterion for mobilization.
Convective diffusional deposition and collection efficiency of aerosol on a dust‐loaded fiber
Authors: Kanaoka Chikao , Emi Hitoshi , Tanthapanichakoon Wiwut 
Published: June 2004

AbstractA three‐dimensional stochastic model, which is effective for the convective diffusional deposition of aerosol particles, was developed starting from Langevin's equation. The model was utilized to simulate collection and agglomeration processes of particles on a cylindrical fiber. By obtaining the distribution of captured particles on a fiber and the evolution of the collection efficiency of a dust‐loaded fiber through the simulation, the effect of Peclet number, interception parameter, and the accumulated mass of particles on them were discussed. Further, the collection efficiency of a dust‐loaded fiber was correlated by using a linear function of the accumulated mass of particles in a unit filter volume. Dependence of coefficient in the linear function, collection efficiency raising factor on Peclet number, and interception parameter were also discussed.
Prediction of heat transfer in turbulent falling liquid films with or without interfacial shear
Authors: Yih Siu‐Ming , Liu Jung‐Liang 
Published: June 2004

AbstractA unified approach is proposed for the prediction of heat transfer coefficients in turbulent falling films undergoing heating, evaporation or condensation for both of the cases with or without interfacial shear. A modified van Driest eddy viscosity model, which incorporated a damping factor f and takes into account the effect of variable shear stress, is used to predict the hydrodynamics of turbulent falling films. The calculated film thicknesses are in good agreement with the Nusselt‐Brauer correlations for the non‐sheared film and the Dukler prediction for highly sheared film. Also, by including a van Driest type turbulent Prandtl number model, the asymptotic heat transfer coefficients are accurately predicted and show better agreement with the extensive literature data and correlations than do most of the existing turbulence models proposed to date.
Applicability of axial dispersion model to analyze mass transfer measurements in bubble columns
Authors: Deckwer W.‐D. , Nguyen‐Tien K. , Kelkar B. G. , Shah Y. T. 
Published: June 2004

AbstractThe applicability of axial dispersion model (ADM) for the measurement of the gas‐liquid mass transfer coefficient (kLa) in bubble columns is discussed. It is shown that the misinterpretation of the concentration jump near the column inlet can lead to wrong conclusions regarding the mass transfer rates. It is further illustrated that some reported kLa dependencies on the superficial liquid velocity and the axial distance are resulted from the use of an incorrect model and can be rectified by an application of ADM. Finally, it is shown that ADM can be effectively used to calculate kLa a for: (a) highly viscous liquids, (b) in the presence of chemical reaction, (c) slurry reactors, and (d) the columns with different liquid inlet locations.
Theory on colloidal double‐layer interactions
Authors: Papadopoulos Kyriakos D. , Cheh Huk Y. 
Published: June 2004

AbstractThe potential energy between two interacting colloidal particles is derived by a knowledge of the energy of interaction of two parallel flat plates. The proposed method maps pairs of infinitesimal surface elements from the two interacting bodies to parallel plate‐like elements. The results obtained from this theory are compared with the Derjaquin approximation for large kR and the Levine and Dube approximation for small kR.
Noncatalytic gas‐solid reactions in a vertical pneumatic transport reactor
Authors: Fan Liang‐Shih , Satija Sunil , Kim B. C. , Nack H. 
Published: June 2004

AbstractA heterogeneous model is developed to account for noncatalytic gas‐solid reactions in a vertical pneumatic transport reactor. The model takes into consideration both the positive and negative variations of the solid porosity and the variation of the gas diffusivity with the reaction. The method of lines utilizing the second order centered finite difference scheme for the spatial discretization is employed to obtain the model solution.Experiments utilizing a vertical pneumatic transport reactor of a laboratory scale are performed to study the reaction between limestone and sulfur dioxide generated from coal combustion. The reactor is of 16.2 cm ID and 610 cm in length. The experimental data for sulfur retention are reported for various superficial gas velocities and calcium‐sulfur molar ratios. Verification of the model with experimental data is conducted. The agreement between the model prediction and experimental data is satisfactory.
Slow second‐order reactions in a deflected buoyant jet
Authors: Forney L. J. , Oakes L. A. 
Published: June 2004

AbstractAn integral method including the entrainment hypothesis of Hoult, Fay and Forney (1969) is used to predict the concentration of product formed in a buoyant jet in a crossflow. The analysis is restricted to a slow, irreversible, second‐order reaction with premixed reactants. Reliable laboratory data are presented for the oxidation of nitric oxide by the reaction 2NO + O2 → 2NO2 with excess O2 and these results are correlated with the theory. Additional measurements are recorded to provide information on the magnitude of the turbulent parameters necessary for proper closure of the rate expressions.
Analytical model for excess Gibbs energy of nonspecific liquid metal interactions
Authors: Cox K. R. , Eckert C. A. 
Published: June 2004

AbstractA physical model for the very strong intermolecular forces in liquid metal mixtures is proposed, involving the combined effects of ion‐ion, ion‐electron, and electron‐electron interactions plus the charge density effects on the electron kinetic energy. The resulting excess Gibbs energy expression contains a single cross‐energy parameter which must be evaluated either from the eutectic point or from one mixture datum. The applicability of the model is limited to systems without strong specific solvation, but it does effectively predict both negative and positive deviations from Raoult's law, including the asymmetry arising from size differences. Applications are shown for vapor‐liquid, liquid‐liquid and solid‐liquid equilibria.
Estimation of true moments from truncated data
Authors: Skopp Joseph 
Published: June 2004

AbstractMoment analysis is a powerful tool in reactor bed analysis. Weighted moments is a technique which has been introduced to increase the accuracy of moment estimation. The supposed advantage of weighted moments is reevaluated utilizing an optimum truncation point. The resulting coefficient of variation in the moment estimates is shown to be superior to an arbitrary truncation point for all weighting factors. When an optimum truncation point is used, little advantage is observed for weighted moments.
Regeneration of carbon containing sodium dodecylbenzene sulfonate—cyclic regeneration with steam in fluidized beds
Authors: Umehara Tadashi , Smith J. M. 
Published: June 2004

AbstractCyclic regeneration of activated carbon containing adsorbed sodium dodecyl‐benzene sulfonate (DBS) was studied in fluidized beds at 1119 K and 101.3 kPa. Optimum restoration of adsorption capacity (97.2% per cycle) resulted when gasification with 21.5% steam was continued for 200 s. At that time, about 85% of the DBS added to the carbon during the adsorption process had been removed. Because of the adsorbed inorganic residue from DBS, these results are somewhat different from earlier studies with the sucrose‐carbon system. With sucrose, maximum restoration of adsorption capacity was achieved when a weight equivalent to 100% of the adsorbed sucrose was removed by thermal decomposition and steam gasification.
Optical methods and results of dew point and deposition rate measurements in salt/ash‐containing combustion gases—B2O3(I) deposition rates by interference methods and comparisons with theory
Authors: Seshadri K. , Rosner D. E. 
Published: June 2004

AbstractThis study is focused on deposition rate processes leading to inefficiency and “hot corrosion” in fossil‐fuel‐fired furnaces and engines. The inorganic compounds which deposit on heat exchanger surfaces and blades are formed in combustion product gases when the fuel and/or ingested air contains inorganic impurities. An improved understanding of the coupled thermodynamic, kinetic, and transport processes governing the deposition rate of inorganic oxides and salts from hot gases containing these compounds (or their precursors) can suggest more efficient test strategies and control measures. Accordingly, an optical interference method for accurately measuring the growth rate of deposits well before the onset of run‐off under laboratory burner conditions has been developed.To demonstrate the technique and provide data suitable for theoretical model development, a deliberately simple chemical system and target geometry are used. BCl3(g) is introduced into a premixed C3H8‐air flat flame at atmospheric pressure. The growth rate of B2O3(I) on an electrically heated platinum ribbon is then measured interferometrically over a range of fuel/air ratios and seed levels. However, the very existence of B2O3(I) deposition at the present seed levels and surface temperatures (about 1,200–1,300 K) clearly demonstrates the importance of kinetic restrictions on B2O3(I) gasification reactions. Optically measured film growth rates are obtained at film thicknesses small enough to neglect condensate run‐off, hence they yield vapor deposition rates directly. These deposition rates are found to be in good agreement with the predictions of a recently developed multicomponent mass‐transfer boundary layer (BL) theory, with a constrained equilibrium ((HBO2)3 precluded) boundary condition. Remarkably, at a constant value of the BCl3 flow rate, the Pt ribbon temperature above which there is no B2O3 condensate (i.e., the so‐called dew point) is observed to depend on the fuel/air ratio. Whereas previous equilibrium‐based deposition models cannot embrace such phenomena, a semi‐quantitative argument, based on the nonequilibrium chemistry of B2O3 precursor formation and (HBO2)3‐formation barriers, explains these potentially significant trends. These encouraging results suggest a more general applicability for the optical methods and chemically frozen (CF) BL theory described herein, and demonstrate the important role of heterogeneous and homogeneous kinetic barriers in determining dew points and deposition rates in combustion systems.
Meandering of water rivulets
Authors: Culkin J. B. , Davis S. H. 
Published: June 2004

AbstractWater rivulets are produced on inclined flat plates made of high‐density polyethylene, Mylar, Plexiglas and acetate film. Conditions are obtained for straight rivulets to begin to meander and for measuring rivulets to cease their unsteadiness. These critical conditions are correlated using a one‐dimensional theory of high Reynolds number slender rivulets in which pressure gradients generated by curvature, surface tensionand contact‐angle hysteresis balance.
Generalized correlation for friction loss in drag reducing polymer solutions
Authors: Darby Ron , Chang Hsun‐Fu D. 
Published: June 2004

AbstractThe definition of the pipe flow friction factor has been extended to include the effect of fluid viscoelastic properties on energy dissipation in turbulent tube flow. The resulting friction factor includes a characteristic fluid relaxation time, which can be determined directly from rheological measurements, and reduces to the usual Fanning friction factor for inelastic fluids. The use of this more general friction factor enables turbulent tube flow data for both fresh and shear degraded “concentrated” drag reducing polymer solutions of various concentrations in various tube sizes to be correlated by the usual f vs. NRe relation for Newtonian fluids in smooth tubes.
Modeling of growth rate dispersion of citric acid monohydrate in continuous crystallizers
Authors: Berglund K. A. , Larson M. A. 
Published: June 2004

AbstractA mathematical model for prediction of the crystal size distribution from a continuous crystallizer is presented. The kinetic data used for the model were obtained from batch contact nucleation experiments with citric acid monohydrate. In these experiments, the distribution of growth rates as well as the initial size distribution were estimated. Results from the model indicate that the excess number of crystals usually present at small sizes in continuous crystallizers is due to growth rate dispersion (where crystals of the same size may have different growth rates) and not size dependent growth.
Hydrodynamics of cocurrent gas‐liquid‐solid semifluidization with a liquid as the continuous phase
Authors: Chern Song‐Hsing , Fan Liang‐Shih , Muroyama K. 
Published: June 2004

AbstractThe hydrodynamic behavior of a cocurrent gas‐liquid‐solid semifluidized bed was investigated. A separate investigation was performed on a packed bed and a fluidized bed under gas‐liquid flow conditions similar to that for the semifluidized bed. Parameters of the semifluidized bed under extensive study include pressure drop, gas holdup, onset liquid velocity for semifluidization, and the height of the packed bed section and the fluidized section. The pressure drop of the semi‐fluidized bed obtained experimentally was compared favorably with that predicted by the model equations.
Measurement and modelling of droplet coalescence and breakage in a pulsed‐plate extraction column
Authors: Garg M. O. , Pratt H. R. C. 
Published: June 2004

AbstractDroplet coalescence and breakage rats in a pulsed‐plate extraction column have been measured using the colorimetric method of Hamilton and Pratt (1980). The results were interpreted in terms of rate constants, defined appropriately for the mixer‐settler and emulsion regions of operation respectively, using a discrete population balance model. It is shown that the resulting values of these constants can be used to predict accurately the steady‐state droplet‐size distribution and apparent coalescence rate. Computations for a typical extraction system indicated that the effect of polydispersivity on performance is surprisingly small for the pulsed plate column.
Dynamic behavior of a porous char particle burning in an oxygen‐containing environment: Part II: Transient analysis of a shrinking particle
Authors: Sotirchos S. V. , Amundson N. R. 
Published: June 2004

AbstractThe diffusion and reaction model developed in a previous paper is extended allowing for shrinkage of the char particles. It is shown that possible shrinkage, arising from disintegration of the solid structure at a certain conversion level, modifies severely the extinction behavior of the reacting particles. Specifically, the region of ambient temperature and particle radius in which the predictions of the nonisothermal and of the isothermal versions of the model differ significantly becomes smaller. However, the particle shrinkage does not affect the ignition phenomena observed since a particle usually ignites at low conversion levels where the radius change is still negligible.
Gels as size selective extraction solvents
Authors: Cussler E. L. , Stokar M. R. , Varberg J. E. 
Published: June 2004

AbstractWe have successfully used cross‐linked, partially‐hydrolyzed, polyacrylamide gels to concentrate solutions of high molecular weight solutes. The gels are sizeselective, concentrating solutes whose diameter exceeds 3 nm. They can be easily regenerated by means of pH‐induced changes in gel swelling; this regeneration is consistent with that inferred from existing theories of gel swelling. The resulting separation process is a good alternative to ultrafiltration.
Liquid‐phase diffusion and adsorption of pyridine in porous silica‐alumina pellets
Authors: Van Vuuren D. S. , Stander C. M. , Glasser David 
Published: June 2004

AbstractThe adsorption and effective diffusivity of pyridine dissolved in heptane were measured in silica‐alumina pellets using a specially developed single‐pellet continous‐flow diffusion cell. The measured diffusivities varied between 0.43 × 10−9 and 3.25 × 10−9 m2·s−1; the temperature dependence of the diffusivities indicated that both pore volume diffusion and surface diffusion play a role in the mass transfer.