bluuebunny/crossref_metadata_2025_split huggingface dataset:
Volatiles loss during atomization in spray drying
Authors: Kieckbusch Theo G. , King C. J. 
Published: June 2004

AbstractLosses of volatile acetates have been measured in the vicinity of pressure nozzles during spraying of sucrose and maltodextrin solutions. Large losses occur very near the atomizer, where only a small portion of the water has evaporated. The effects of atomizer design, nozzle pressure, sucrose concentration, air flow rate, air temperature and liquid feed temperature have all been measured. Correlation of volatiles loss vs. percent water evaporation accounts for most of the effects of changes in spray pattern and drop size distribution. Individual contributions of gas and liquid phase mass transfer are determined from the relative retentions of acetates of different molecular weight and from the effect of sucrose concentration. In the expanding film at the nozzle, both gas and liquid phase resistances are important, but the losses become entirely liquid phase controlled once drops are formed.
Heat transfer from two‐phase boundary layers on isothermal cylinder: Influence of drop trajectory
Authors: Lu Christopher C. , Heyt John W. 
Published: June 2004

AbstractThe influence of drop trajectories on boundary layer structure and heat transfer coefficient is determined for a binary spray flow over the upstream surface of an isothermal cylinder. Governing equations are solved for drop trajectories upstream of the cylinder, the laminar liquid boundary layer adjacent to the cylinder surface, and the outer laminar vapor boundary layer. Velocity, temperature, and mass concentration profiles throughout the double boundary layers are shown to depend on flow parameters involving drop size and velocity. The critical conditions for which the liquid film dries out are identified for a range of drop size and velocity, defining the transition from the liquid film to the dry wall flow regime. Theoretical results for heat transfer are shown to correlate existing experimental data.
The extended Graetz problem with prescribed wall flux
Authors: Papoutsakis Eleftherios , Ramkrishna Doraiswami , Lim Henry C. 
Published: June 2004

AbstractAn analytical solution is obtained to the extended Graetz problem with prescribed wall flux, based on a selfadjoint formalism resulting from a decomposition of the convective diffusion equation into a pair of first‐order partial differential equations. The solution obtained is simple, computationally efficient and in striking contrast with incomplete numerical efforts in the past.
Transport phenomena in solids with bidispersed pores
Authors: Neogi P. , Ruckenstein E. 
Published: June 2004

AbstractExisting analyses for transport phenomena in bidisperse porous media assume that the microparticles act as uniformly distributed point sinks. This article provides an analysis which determines under what conditions the point sink approximation is valid. For random packing, the concentration field inside a pellet is described by its ensemble average, i.e., the average over all possible ways in which the microparticles can be packed into the pellet. For these averaged quantities, we formulate the transport equations for a solid with bidisperse pores which provide the criteria of validity of the point sink approximation.
Permeation cascades for the separation of krypton and xenon from nuclear reactor atmospheres
Authors: Stern S. A. , Wang S.‐C. 
Published: June 2004

AbstractMultistage permeation cascades have been designed for the removal of radioactive krypton and xenon from nuclear reactor atmospheres. These cascades could serve for the decontamination of the atmosphere within a reactor containment dome following a nuclear accident and for other applications of interest to the nuclear industry. The stages of the cascades are assumed to consist of permeator modules using silicone rubber capillaries as separation membranes. All stages are to be operated in a countercurrent mode with shell‐side feed.It is shown that it is possible to design an ideal cascade for the separation of multicomponent mixtures by matching the concentrations of a suitable key component in interstage streams that are mixed. This procedure minimizes the cascade volume and power requirement. It is also possible to design a cascade with constant stage cuts in its enriching and stripping sections that approximates the performance of an ideal cascade. The krypton and xenon content of a feed mixture containing about 1 × 10−3 mol% Kr and 1 × 10−2 mol% Xe in air can be lowered by factors of 103 and 108 respectively in a 27‐stage permeation cascade. Methods of reducing the number of stages and the effects of irradiation on the membrane performance are also discussed.
Mathematical modeling of catalytic converter lightoff: Single‐pellet studies
Authors: Oh Se H. , Cavendish James C. , Hegedus L. Louis 
Published: June 2004

AbstractA detailed mathematical model of a single catalyst pellet has been developed to describe its behavior under transient conditions encountered during the warmup period of automobile exhaust catalytic converters. In contrast to the converter models previously reported in the literature, this model is capable of describing the time‐dependent behavior of a composite catalyst pellet, and thus provides a convenient means of examining the effects of poison penetration and various noble metal impregnation strategies in the activity‐time (rather than activity‐temperature) domain.Extensive calculations were carried out to investigate the effects of various catalyst design parameters and converter operating conditions on the lightoff behavior of a spherical, platinum‐alumina catalyst pellet. Due to the complex kinetics of the CO and hydrocarbon oxidation reactions, catalyst lightoff was found to exhibit interesting behavior with respect to variations of the system's design parameters and operating conditions. Graphs are presented to illustrate the parameteric sensitivity of these effects.
Modeling pulverized coal conversion in entrained flows
Authors: Sprouse K. M. 
Published: June 2004

AbstractA detailed description of pulverized coal conversion in one‐dimensional entrained flows has been formulated and correlated to hydrogasification data from the Rockwell International Flash Hydropyrolysis (FHP) reactor using bituminous coals. This analysis contains physical and chemical descriptions which have not been included in previous mathematical models. These descriptions provide further important insights into the nature of entrained flow coal gasification.
Photo‐assisted heterogeneous catalysis with optical fibers II. Nonisothermal single fiber and fiber bundle
Authors: Marinangeli R. E. , Ollis D. F. 
Published: June 2004

AbstractA previous paper (Marinangeli and Ollis, 1977) considered light transport in a single optical fiber which was coated with a heterogeneous photoassisted catalyst. This paper analyzes simultaneous mass, heat, and light transport in a catalyst on a single fiber, and in a likely large‐scale configuration, a bundle of parallel, catalyst‐coated optical fibers. The dimensionless temperature rise is dominated by energy released by light absorption, with the heat of reaction contributing to a lesser degree.
Hydrodynamic effect of surfactants on gas‐liquid oxygen transfer
Authors: Lee Y. H. , Tsao G. T. , Wankat P. C. 
Published: June 2004

AbstractAn experimental investigation of the hydrodynamics at the surface region of the liquid reveals that the soluble surfactants (sodium lauryl sulfate, glucose oxidase, and bovine serum albumin) affect both the length and the velocity scales of liquid eddies approaching the surface, which results in a decrease in mass transfer.
Simultaneous measurement of interfacial area and mass transfer coefficient in three‐phase fluidized beds
Authors: Dhanuka Vinodkumar R. , Stepanek Josef B. 
Published: June 2004

AbstractThe technique of simultaneous measurement of the mass transfer coefficient and the interfacial area (Robinson and Wilke, 1974) was used to measure the volumetric liquid‐phase mass transfer coefficient \documentclass{article}\pagestyle{empty}\begin{document}$\left({k_L \underline a} \right)$\end{document}, the interfacial area \documentclass{article}\pagestyle{empty}\begin{document}$\left({\underline a} \right)$\end{document} and the true liquid‐phase mass transfer coefficient (kL) in three‐phase fluidized beds. The eddy‐cell model of Lamont and Scott (1970) was found to give a reasonable fit to the kL data, if the proportionality constant is modified. The \documentclass{article}\pagestyle{empty}\begin{document}$k_L \underline a$\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$\underline a$\end{document} data were correlated by empirical equations. Some information on bubble diameter was deduced from the interfacial area and holdup measurements.
Adsorption of binary and ternary hydrocarbon gas mixtures on activated carbon: Experimental determination and theoretical prediction of the ternary equilibrium data
Authors: Costa E. , Sotelo J. L. , Calleja G. , Marrón C. 
Published: June 2004

AbstractExperimental binary and ternary equilibrium data for the adsorption of hydrocarbon mixtures of methane, ethane, ethylene, and propylene on activated carbon at 20°C are presented and discussed. Reproduction of binary adsorption equilibria and prediction of ternary adsorption equilibria exclusively with data of binary systems have been carried out using a real adsorbed solution theory, which requires the calculation of the activity coefficients for the components in the adsorbed phase.Predicted equilibrium data are found to be in excellent agreement with experimental values using Wilson and UNIQUAC equations to calculate the activity coefficients. The real absorbed solution theory provides a much more accurate method for predicting multicomponent adsorption equilibria than the ideal adsorbed solution theory.
A branched pore kinetic model for activated carbon adsorption
Authors: Peel Russell G. , Benedek Andrew , Crowe Cameron M. 
Published: June 2004

AbstractA branched pore kinetic model for aqueous phase activated carbon adsorption is presented in which the carbon particle is separated into rapidly and slowly diffusing regions. The model was developed to overcome problems arising from a single rate parameter analysis and is shown to describe experimental data well. In addition to very different rates of transport in the two regions, parameters estimated by regression analysis indicated differences in the adsorptive characteristics.
Measurement and application of limiting activity coefficients
Authors: Eckert C. A. , Newman B. A. , Nicolaides G. L. , Long T. C. 
Published: June 2004

AbstractInfinite dilution activity coefficients (γ∞) in binary liquid mixtures are data of wide practical and theoretical applicability, but their extensive use has been hindered by the experimental limitations of classical vapor‐liquid equilibrium techniques. Two new experimental methods for accurate γ∞ determinations are presented. These techniques, both faster and more accurate than classical methods, are complementary, and their applicability to different types of binary systems is discussed.
Distribution equilibrium between a bulk phase and small pores
Authors: Glandt E. D. 
Published: June 2004

AbstractThe pore‐bulk distribution coefficient K for a solute species is calculated by modelling the solute molecules as hard spheres. K is expanded in a virial‐type series in powers of the bulk‐phase concentration. The leading term is the Henry's law constant. The next two coefficients are reported for three pore shapes.
Gas‐phase combustion in fluidized beds
Authors: Stubington J. F. , Davidson J. F. 
Published: June 2004

AbstractKerosine or propane was injected near the base of a small, air‐fluidized bed of sand at 940°C. The fraction of fuel burnt within the bed was determined from a heat balance, for various particle sizes, fluidizing velocities, and bed depths.Assuming the initial formation of a train of fuel vapor bubbles, theoretical analysis indicated two stages of combustion: (1) rapid consumption of the oxygen initially between fuel vapor bubbles; (2) slow consumption of oxygen initially outside the fuel vapor region by radial diffusion of oxygen and fuel vapor, analogous to a diffusion flame.Comparison of experiment with theory gave effective radial diffusion coefficients of the same order of magnitude as the molecular diffusion coefficient. It was inferred that combustion occurs largely by a diffusion flame within the bed, with diffusion through the particulate phase being the rate‐controlling step. This explains why fuel distribution is so important in attaining efficient combustion.
Effect of chemical modifiers on borax crystal growth, nucleation and habit
Authors: Randolph A. D. , Puri A. D. 
Published: June 2004

AbstractThe effects on the fine‐crystal CSD of various surface active and ionic additives were studied for the sodium tetraborate decahydrate (borax) system. The organic modifiers used were effective at the ppm level. Surface active agents inhibited nucleation rate, while ionic additives increased nucleation. A simultaneous reduction in both the linear‐crystal growth rate and the degree of polycrystalline growth was observed in both cases. These effects correlated with modifier concentration in the liquor, but not with modifier/solids ratio. Borax exhibits classical magma and RPM‐dependent secondary nucleation and the results were well‐correlated with a conventional power‐law kinetic model.
Drop size and continuous‐phase mass transfer in agitated vessels
Authors: Skelland A. H. P. , Lee Jai Moon 
Published: June 2004

AbstractContinuous‐phase mass transfer coefficients and drop sizes in agitated vessels are correlated with operating variables and physical properties of liquid‐liquid systems. In formulating mass transfer coefficients, a realistic mechanism has been developed, involving periodically varying rates of surface renewal associated with droplet circulation through varying degrees of turbulence around the vessel. Relationships are obtained for optimized design and scale‐up.
Effect of external diffusion on deactivation rates
Authors: Krishnaswamy S. , Kittrell J. R. 
Published: June 2004

AbstractAlteration in concentration‐independent catalyst decay rates due to the presence of finite external and internal mass transfer resistances is examined. Analytical expressions for external and overall time‐dependent catalytic effectiveness are developed. Analysis of diffusion‐limited catalyst deactivation in flow reactors is discussed.
Wrong‐way behavior of packed‐bed reactors: 1. The pseudo‐homogeneous model
Authors: Mehta P. S. , Sams W. N. , Luss D. 
Published: June 2004

AbstractA sudden reduction in the feed temperature to a packed‐bed reactor leads to a transient temperature rise, which is referred to as the wrong‐way behavior. A pseudo‐homogeneous plug‐flow model is used to analyze the structure of this transient behavior. The key parameters which determine the magnitude of this response are the dimensionless adiabatic temperature rise, activation energy, heat transfer capacity, coolant temperature, magnitude of temperature drop and length of the reactor. A simple expression is derived for predicing the maximum transient temperature rise.
Heat and mass transfer in hygroscopic capillary extruded products
Authors: Fortes Mauri , Okos Martin R. 
Published: June 2004

AbstractThis work presents an analysis of heat and mass transfer of extruded corn meal. Isotherm, thermal conductivity, drying and center temperature data were experimentally obtained for the cylindrically extruded product.Modeling of the drying process was made by incorporating the mechanistic and irreversible thermodynamics approaches for determining heat and mass transfer in capillary‐porous media. The proposed model shows that both liquid and vapor fluxes can be expressed in terms of the same driving‐forces, namely, temperature and equilibrium moisture content gradients. A search technique allowed for the evaluation of both liquid and vapor conductivities.
An experimental investigation of stability and multiplicity of steady states in a biological reactor
Authors: DiBiasio David , Lim H. C. , Weigand W. A. 
Published: June 2004

AbstractThe existence of multiple stable and unstable steady states in a continuous stirred tank biological reactor (CSTBR) was demonstrated experimentally for the first time. These experiments resulted in the determination of growth rate, yield and intermediate metabolite concentration data entirely from continuous culture. This information was used to qualitatively interpret the stability behavior in terms of the biochemistry and bioenergetics of substrate metabolism.
Aerosol formation in reacting gases: Theory and application to the anhydrous NH3‐HCL system
Authors: Dahlin R. S. , Su Ja‐An , Peters L. K. 
Published: June 2004

AbstractAerosol formation in reacting gases is treated in terms of the gas‐phase reaction, homogeneous nucleation of the reaction product, and particle growth by parallel mechanisms. In the absence of foreign nuclei, nucleation of the gas‐phase reaction product is described by classical homogeneous theory with a nonequilibrium correction factor included; particle growth by diffusion, surface reaction, and cluster scavenging are examined. The predicted contribution of the latter mechanism increases with increasing supersaturation ratio due to a shift in the distribution of cluster sizes in accordance with a Boltzmann‐type steady‐state distribution. Illustrative results predict a nucleation burst during which the formation of nucleating monomer by chemical reaction competes with the loss of monomer due to diffusion to the surface of the freshly formed particles. In addition, conditions under which cluster scavenging can dominate are shown.The particle‐size spectra predicted using the theory are compared with experimentally measured size spectra of NH4Cl particles formed by the gas‐phase reaction of NH3 and HCl. The size spectra were measured using an electrical aerosol size analyzer and an optical counter at the outlet of a continuous flow reactor after residence times ranging from 2 to 50 seconds. Reactant concentrations of 2.1 × 10−5 to 4.1 × 10−4 mol/m3 (0.5 to 10 ppm) were studied at 23 to 26°C and near atmospheric pressure. The predicted size spectra showed good agreement with the experimental results. At reactant concentrations below 4.1 × 10−4 mol/m3, the predominant particle growth was apparently by diffusion of the monomer in the noncontinuum range. Based on analysis of other data, cluster scavenging became more significant at reactant concentrations greater than about 8 × 10−4 mol/m3, and coagulation was not significantly important. Furthermore, these studies implied a microscopic surface free energy for NH4Cl of approximately 0.051 N/m.
Effect of flow direction on conversion in isothermal radial flow fixed‐bed reactors
Authors: Balakotaiah Vemuri , Luss Dan 
Published: June 2004

AbstractSingular perturbation solutions are used to derive criteria predicting the influence of change in flow direction on the conversion in an isothermal radial‐flow, fixed‐bed reactor. It is shown that when the reaction does not involve a change in the number of moles, the outward flow direction is the preferred one for any reaction with a convex rate expression. The inward flow direction is a better choice for any reaction with a concave rate expression. A more intricate behavior occurs for reactions involving a change in volume. Analytical approximations and numerical solutions indicate that the influence of flow direction on the conversion is rather small.
A framework for description of mechanical mixing of fluids
Authors: Ottino J. M. , Ranz W. E. , Macosko C. W. 
Published: June 2004

AbstractMechanical mixing of fluids interpreted as deformation of contact interfaces between materials or originally designated material surfaces, can be described by continuum mechanical arguments. The idea is developed at two levels.Part I: Exact kinematical description of mixing of fluids with negligible interfacial tension.Part II: Description of mixing of fluids with negligible interfacial tension in terms of intermaterial area density.The approach provides a unified mathematical description of the mechanical mixing of fluids.
Solubilities of carbon dioxide, hydrogen sulfide and nitrogen mixtures in methanol
Authors: Rousseau R. W. , Matange J. N. , Ferrell J. K. 
Published: June 2004

AbstractPreviously published data for the six binary combinations that can be formed from CO2, H2S, N2 and methanol are used to obtain parameters of the four‐suffix Margules equation describing liquid solution behavior. The vapor phase is described by the Soave modification of the Redlich‐Kwong equation of state. Isothermal binary data are fit well by these equations. The effects of temperature on the Margules parameters are significant and, except for N2‐containing mixtures, the parameters were taken to be inversely proportional to absolute temperature.Experimental data were obtained for multicomponent mixtures of CO2, H2S, N2 and methanol. Model predictions were tested against these data. Comparisons of predicted and measured values of bubble point pressure and equilibrium vapor compositions are satisfactory.
Connection between relative gain and control loop stability and design
Authors: McAvoy T. J. 
Published: June 2004

AbstractThe objective of this paper is to point out the relationship between the relative gain array (RGA) and control system stability and design. Rigorous stability limits are presented for a general 2 × 2 system for several cases involving both steady state and dynamic interactions. These stability limits explicity involve the RGA. Two specific examples of interaction in distillation models are also discussed.
Diffusion and reaction in a stagnant boundary layer about a carbon particle, part 7: Transient behavior and effect of water vapor
Authors: Sundaresan S. , Amundson Neal R. 
Published: June 2004

AbstractThe dynamics of carbon combustion is studied. It is shwon that the carbon particle will not ignite if the furnace temperature is below a certain critical value. In addition, carbon particles display thermal instabilities which can be delayed or eliminated by increasing the water vapor concentration and/or the furnance temperature.
Wall effects in laminar flow of fluids through packed beds
Authors: Cohen Yoram , Metzner A. B. 
Published: June 2004

AbstractA model which accounts for the effect of a confining wall and the resulting voidage variations near it on the flow behavior in packed columns is proposed.The model, which is restricted to columns randomly packed with spheres of uniform size, reasonably describes the pressure drop‐flow rate relationship for both linear and non‐Newtonian fluids. The mass flux distribution is also studied in order to provide an insight into processes in which the flow behavior near the wall may be important.
Collection efficiency of cyclone separators
Authors: Dietz P. W. 
Published: June 2004

AbstractBased on terLinden's (A. J. terLinden, “Investigations into Cyclone Dust Collectors,” IME Proc., 160, 233, 1949) experimental observations, a three‐region model is proposed for the fluid flow in a cyclone. Within each region, turbulence is assumed to promote mixing of the suspended particles. Incorporation of this mixing concept into the three‐region model allows an analytic expression for the collection efficiency of the cyclone to be developed.The theoretical result is compared with data obtained in the high temperature, high pressure exhaust from a pressurized fluidized bed combustor.