Showing papers on "Mass transfer published in 1991"
TL;DR: In this article, the authors assess the potential significance of deviations from local equilibrium for the exchange of mass between residual nonaqueous phase liquids and the aqueous phase in the saturated groundwater zone.
Abstract: The objective of this work is to assess the potential significance of deviations from local equilibrium for the exchange of mass between residual nonaqueous phase liquids and the aqueous phase in the saturated groundwater zone. A one-dimensional convection-dispersion mass balance equation incorporating a first-order interphase mass transfer rate relationship and temporal changes in blob configuration is used to model this system. Analytical and numerical methods are employed to examine the steady state and transient behavior of the system under a variety of hypothetical aquifer conditions and pumping remediation schemes. Sensitivity of the model to several parameters including mass transfer coefficient, blob size and shape, and Darcy velocity is explored. Results of the theoretical assessment indicate that nonequilibrium effects could play a significant role in some contamination scenarios, primarily for large blob sizes and relatively high velocities. Design of soil flushing techniques will be impacted by these conclusions. Uncertainty in several parameter values used in this analysis indicate the need for further experimental investigation of this process.
293 citations
TL;DR: In this paper, the authors investigated the transport of linearly interacting solutes in porous media with the help of residence time distributions, transfer functions, methods of system dynamics, and time-moment analyses.
Abstract: The transport of linearly interacting solutes in porous media is investigated with the help of residence time distributions, transfer functions, methods of system dynamics, and time-moment analyses The classical one-dimensional convection-dispersion equation is extended to two-region (mobile-immobile water) transport by including diffusional mass transfer limitations characteristic of aggregated soils The two-region model is further revised by incorporating the effects of multiple retention sites (in parallel or in series), multiple porosity levels, and arbitrary but steady flow fields It is shown that different physical situations can be represented by a relatively small number of transfer functions containing only two types of parameters: distribution coefficients to account for equilibrium properties and characteristic times reflecting kinetic processes Relevant kinetic processes include convective transport, hydrodynamic dispersion, adsorption-desorption, and physical or chemical mass transfer limitations In most situations, theoretical breakthrough curves are found to be relatively insensitive to the mathematical structure of the transfer function, irrespective of the physical interpretation of the distribution coefficients and the characteristic times in the model This means that alternative physical and chemical interpretations of model parameters can lead to nearly identical breakthrough curves Certain transfer time distributions can lead to quite unusual shapes in the breakthrough curves; these curves strongly depend on the characteristic times and a few operational variables Results of this study show that the transfer time distribution is an extremely useful tool for explaining some unexpected experimental results in the solute transport literature
262 citations
TL;DR: In this article, many thin-layer drying and rewetting equations have been reviewed and discussed, and some suggestions for future coordinated research work arc given, as well as a review of the current state-of-the-art.
Abstract: Thin-layer equations contribute to the understanding of the heat and mass transfer phenomena in agricultural products and computer simulations for designing new and improving existing commercial drying processes. Many different equations have been developed to represent thin-layer drying behaviour of the grains. Many thin-layer drying and rewetting equations are reviewed and discussed. Some suggestions for future coordinated research work arc given.
236 citations
TL;DR: In this paper, a systematic examination of published sedimentary and metamorphosed pelite analyses has revealed evidence of significant mass transfer and volume strain during regional metamorphism, which is not an isochemical process.
Abstract: Systematic examination of published sedimentary and metamorphosed pelite analyses has revealed evidence of significant mass transfer and volume strain during regional metamorphism. Statistical analysis of the data shows that Barrovian zone metamorphism of pelitic schist generally causes increases in the whole-rock concentrations of the low-solubility elements Ti and All The observed increases in Ti and Al contents as functions of metamorphic grade are almost certainly due to residual enrichment caused by the removal of other more soluble species. Application of mass-balance principles to the petite compositional trends indicates that the average pelite may lose as much as 30% of its mass and volume during progressive metamorphism from subgreenschist to amphibolite facies conditions. The bulk of the lost mass is silica, not volatiles. In addition, other elements, particularly Ca, Na, and K, appear to be highly mobile in deep-crustal metamorphism. Contrary to conventional interpretations, it is concluded that the regional metamorphism of pelites is not an isochemical process.
208 citations
TL;DR: The experimental data, which quantitatively express the diffusion coefficient as a function of the cell concentration, are compared with a number of well‐known equations developed for mass transfer in heterogeneous media and a procedure for the theoretical prediction of effective diffusion coefficients in cell‐containing gels is recommended.
Abstract: Eleven experimental investigation of diffusion in gels containing immobilized cells are reviewed. The experimental data, which quantitatively express the diffusion coefficient as a function of the cell concentration, are compared with a number of well-known equations developed for mass transfer in heterogeneous media. Based on this comparison, a procedure for the theoretical prediction of effective diffusion coefficients in cell-containing gels is recommended.
186 citations
TL;DR: In this article, the authors performed experiments on evaporation kinetics of droplets of water, colloidal silica, sodium sulphate and skimmed milk, and the experimental procedure was similar to that proposed by Charlesworth and Marshall (1960, A.I.Ch.E.J.6, 9−23).
170 citations
TL;DR: In this paper, a film theory model for dissolution and precipitation of calcite from a plane surface in a H2O-CO2-CaCO3 solution under turbulent flow conditions is presented.
160 citations
TL;DR: In this article, a mixture of large biochemicals can exhibit complex chromatographic behavior, in addition to mass transfer mechanisms, in the presence of nonequilibrium adaption.
149 citations
TL;DR: In this article, the rate-limited sorption and nonequilibrium transport of several hydrophobic organic chemicals in three low-organic carbon aquifer materials was investigated using miscible displacement experiments performed at two pore water velocities and with very low solution-phase concentrations.
Abstract: The rate-limited sorption and nonequilibrium transport of several hydrophobic organic chemicals in three low-organic carbon (<0.025%) aquifer materials was investigated. Results of miscible displacement experiments performed at two pore water velocities and with very low solution-phase concentrations (30–60 μg L−1) were analyzed using a first-order mass transfer nonequilibrium model, as well as a model employing the local equilibrium assumption. Results of the analyses revealed sorption to be significantly rate limited, possibly by a diffusion-limited mechanism. The impact of rate-limited sorption on transport was dependent upon pore water velocity. The experiments performed at a faster velocity (∼1 cm/h) could be successfully simulated only with the nonequilibrium model, whereas the equilibrium model was adequate for the slower-velocity (∼0.2 cm/h) experiments. Comparison of experimental results to those reported in the literature revealed that time scale has a significant impact on the degree of nonequilibrium observed in, and on the values of rate constants determined from, experiments. Regression equations were developed for the two kinetics-associated parameters contained in the nonequilibrium model: first-order mass transfer constant and fraction of instantaneous sorption.
147 citations
TL;DR: Similarity solutions for buoyancy induced heat and mass transfer from a vertical plate embedded in a saturated porous medium are reported for constant wall temperature and concentration, constant wall heat and flux.
141 citations
TL;DR: In this article, the effects of capillarity, disjoining pressure, gravity and temperature on equilibrium, fluid flow and mass transfer associated with the liquid film are discussed, and the non-equilibrium processes of change-of-phase heat transfer and fluid flow in stationary and in spreading thin films are intrinsically connected.
TL;DR: In this paper, the authors measured the interfacial mass transfer coefficients for the transfer of the proteins α-chymotrypsin and cytochrome c between a bulk aqueous and a reversed micellar phase using a stirred diffusion cell.
TL;DR: In this paper, a 66 dm3 trickle-bed bioreactor was constructed to assess the possibilities of eliminating dichloromethane from industrial waste gases, which was filled with a randomly-stacked polypropylene packing material over which a liquid phase was circulated.
Abstract: A 66 dm3 trickle-bed bioreactor was constructed to assess the possibilities of eliminating dichloromethane from industrial waste gases. The trickle-bed bioreactor was filled with a randomly-stacked polypropylene packing material over which a liquid phase was circulated. The pH of the circulating liquid was externally controlled at a value of 7 and the temperature was maintained at 25 °C. The packing material was very quickly covered by a dichloromethane-degrading biofilm which thrived on the dichloromethane supplied via the gas phase. The biological system was very stable and not sensitive to fluctuations in the dichloromethane supply. Removal of dichloromethane from synthetic waste gas was possible down to concentrations well below the maximal allowable concentration of 150mg/m3 required by West-German law for gaseous emissions. At higher dichloromethane concentrations specific dichloromethane degradation rates of 200 g h−1 m−3 were possible. At very low inlet concentrations, dichloromethane elimination was completely mass transfer limited.
TL;DR: In this article, it is suggested that heat could be transferred from a magmatic source to the region below the lake by a heat-pipe mechanism, commonly associated with geothermal systems.
TL;DR: In this paper, a simple explanation for this similarity can be found if the mass loss, by stellar wind, from the Roche filling star is the driving mechanism behind mass transfer in close binary systems.
Abstract: Stars in close binary systems can suffer two kinds of mass change : 1) mass transfer between the stars, and 2) mass loss completely from the system. The former process occurs when one the stars fills its Roche lobe while the latter may be in the form of a stellar wind. When both of these exist together, observational estimates indicate that the mass-transfer rate and the mass-loss rate are of the same order. A simple explanation for this similarity can be found if the mass loss, by stellar wind, from the Roche filling star is the driving mechanism behind mass transfer
Book•
01 Nov 1991
TL;DR: In this article, the authors define a set of dimensionless numbers for scale-up of a single-screw machine for Newtonian and non-Newtonian solids.
Abstract: 1 Dimensional Analysis- 11 A Brief Historical Survey- 12 Introduction to Dimensional Analysis- 13 Fundamentals of Dimensional Analysis- 131 Physical quantities and the relationship between them- 132 Consistency of secondary units and invariance of physical relationships- 133 Physical dimensions, Systems of dimensions, Dimensional constants- 134 The dimensional matrix and its linear dependence- 135 The ? Theorem- 2 Description of a Physical Process with a full Set of Dimensionless Numbers- 21 The Relevance List for a Problem- 211 Geometric variables- 212 Material parameters- 213 Process-related parameters- 214 Universal physical constants- 215 Intermediate quantities- 22 Determination of a Complete Set of Dimensionless Numbers- 23 The ? Relationship- 24 Reduction of the Size of the Matrix- 25 Change of Dimensional Systems- 3 Similarity and Scale-up- 31 Basic Principles of Scale-up- 32 Experimental Methods for Scale-up- 33 Scale-up under Conditions of Partial Similarity- 4 Treatment of Variable Physical Properties by Dimensional Analysis- 41 Dimensionless Representation of the Material Function- 42 The ? set for Variable Physical Properties- 43 Treatment of non-Newtonian Liquids by Dimensional Analysis- 44 Treatment of Viscoelastic Liquids by Dimensional Analysis- Examples of Practical Application- A Examples from the Field of Mechanical Unit Operations- Introductory remarks- Example A 1:- Power consumption and mixing time for the homogenization of liquid mixtures Design principles for stirrers and the determination of optimum conditions (minimum mixing work P?)- Example A 2:- Power consumption in the case of gas/liquid contacting Design principles for stirrers and model experiments for scale-up- Example A 3:- Power consumption and gas throughput in self-aspirating hollow stirrers Optimum conditions for P/q = min and an answer to the question whether this type of stirrer is suitable for technical applications- Example A 4:- Mixing of solids in drums with axially operating paddle mixer- Example A 5:- Gas hold-up in bubble columns and its dependenceon geometric, physical and process-related parameters- Example A 6:- Description of the flotation process with the aid of two intermediate quantities- Example A 7:- Preparation of design and scale-up data for mechanical foam breakers without knowledge of the physical properties of the foam- Example A 8:- Description of the temporal course of spin drying in centrifugal filters- Example A 9:- Description of particle separation by means of inertial forces- Example A 10:- Conveying characteristics of single-screw machines for Newtonian and non-Newtonian liquids Optimum conditions (P/q = min) and scale-up- B Examples from the Field of Thermal Unit Operations-Heat and Mass Transfer- Introductory Remarks- Example B1:- Steady-state heat transfer in the mixing vessel at cooling and the optimum conditions for maximum removal of the heat of reaction- Example B2:- Steady-state heat transfer in bubble columns- Example B3:- Time course of temperature equalization in a liquid with temperature-dependent viscosity in the case of free convection- Example B4:- Mass transfer in the gas/liquid system in mixing vessels (bulk aeration) and in biological waste water treatment pools (surface aeration)- Example B5:- Design and scale-up of injectors as gas distributors in bubble columns- Example B6:- Scale-up problems relating to continuous, carrier-free electrophoresis- C Examples from the Field of Chemical Reaction Engineering- Introductory remarks:- Example C1:- Continuous chemical reaction processes in a tubular reactor- 1 Homogeneous irreversible reactions of the 1st order- 2 Heterogeneous catalytic reactions of the 1st order- Example C2:- Influence of back-mixing (macromixing) on the degree of conversion in continuous chemical reaction operation- Example C 3:- Influence of micro-mixing on selectivity in a continuous chemical reaction process- Example C4:- Mass transfer limitation of the reaction rate of fast chemical reactions in the heterogeneous material system gas/liquid- Important, Named Dimensionless Numbers- A Mechanical Unit Operations- B Thermal Unit Operations (Heat Transfer)- C Thermal Unit Operations (Mass Transfer)- D Chemical Reaction Engineering- References- A Single Topics- B Books and General Treatises- C Examples of Application
01 Dec 1991-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this article, the energy equation for solidifying dendritic alloys that includes the effects of heat of mixing in both the dendrite solid and the interdendritic liquid is derived.
Abstract: The energy equation for solidifying dendritic alloys that includes the effects of heat of mixing in both the dendritic solid and the interdendritic liquid is derived. Calculations for Pb-Sn alloys show that this form of the energy equation should be used when the solidification rate is relatively high and/or the thermal gradients in the solidifying alloy are relatively low. Accurate predictions of transport phenomena in solidifying dendritic alloys also depend on the form of the solute conservation equation. Therefore, this conservation equation is derived with particular consideration to an accounting of the diffusion of solute in the dendritic solid. Calculations for Pb-Sn alloy show that the distribution of the volume fraction of interdendritic liquid (gL) in the mushy zone is sensitive to the extent of the diffusion in the solid. Good predictions ofgL are necessary, especially when convection in the mushy zone is calculated.
TL;DR: In this paper, the authors show how intraparticle convection affects residence time distribution of inert and linearly adsorbed species in fixed-bed processes and demonstrate how column efficiency is improved by the use of large-pore supports.
TL;DR: In this article, a new set of equations describing the growth and evaporation of small liquid droplets in a pure vapour are presented, which model both mass and heat transfer between the droplet and the vapour, and are suitable for practical calculations at any Knudsen number.
TL;DR: In this article, the performance of both dispersed gas phase and dispersed liquid phase systems under both mass transfer controlled and non-mass transfer controlled conditions was examined. But the performance was limited to a few minutes for these gaseous substrate fermentations.
TL;DR: In this article, a turbulent eddy-based surface renewal theory for condensation and evaporation of saturated vapor onto or from its liquid is proposed, which accurately predicts experimental data for horizontal, concurrent condensation of steam on water.
TL;DR: A sensitivity analysis of the parameters at their values during the experiments revealed that apart from the radius of the spheres and the substrate bulk concentration, the external mass transfer resistance coefficient is the most sensitive parameter for this case.
Abstract: The modeling of the growth of Nitrobacter agilis cell immobilized in kappa-carrageenan is presented. A detailed description is given of the modeling of internal diffusion and growth of cells in the support matrix in addition to external mass transfer resistance. The model predicts the substrate and biomass profiles in the support as well as the macroscopic oxygen consumption rate of the immobilized biocatalyst in time. The model is tested by experiments with continuously operated airlift loop reactors containing cells immobilized in kappa-carrageenan. The model describes experimental data very well. It is clearly shown that external mass transfer may not be neglected. Furthermore, a sensitivity analysis of the parameters at their values during the experiments revealed that apart from the radius of the spheres and the substrate bulk concentration, the external mass transfer resistance coefficient is the most sensitive parameter for our case.
TL;DR: In this article, the authors measured the mass transfer to agglomerate titanium dioxide aerosols produced in a thermal reactor and compared it to mass transfer for spheres of the same mobility.
Abstract: The mass transfer to agglomerate titanium dioxide aerosols produced in a thermal reactor was measured and compared to the mass transfer for spheres of the same mobility. The material transferred to the particles was ultrafine radioactive lead clusters produced via the decay chain of ^(227)Ac. The lead attachment rate was measured with an epiphaniometer, a device that mixes a fixed concentration of radioactive lead atoms with the sample for a period of several minutes and then measures the quantity of lead attached to the particles. In the free-molecular regime, where the particle diameter is small compared with the mean free path of the gas and the diffusing species, previous studies have shown by theory and experiment that the mass transfer to an aerosol is inversely proportional to the particle mobility. This study showed that this is also true for particles in the transition regime, where the particle diameter is comparable to the mean free path. Further, the mass transfer rate is shown to be independent of particle shape for particles of the same mobility, at least when the mean free paths of the gas and the diffusing species are comparable.
TL;DR: In this paper, the authors used the Afmite-element formulation to obtain numerical solutions to the simultaneous moisture and heat diffusion equations describing the moisture removal and heat intake process for an isotropic sphere.
Abstract: Afmite-element formulation is used to obtain numerical solutions to the simultaneous moisture and heat diffusion equations describing the moisture removal and heat intake process for an isotropic sphere. The model is used to solve a sample problem of drying a soybean kernel. The distribution and gradients of temperature and moisture dveloped inside the kernel during the drying process are established. The predicted drying curve for the soybean model compared favorably with experimental results in the literature. This technique is very powerful in explaining the complicated coupled phenomena of heat and mass transfer in general, and drying of biomaterials in particular.
Book•
01 Jan 1991
TL;DR: In this article, ideal isothermal reactors, single-electrochemical reactions kinetics of electrochemical reactions, mechanism determination and multistep processes with interphase mass transport dynamics and real flow in electrolytic reactors are discussed.
Abstract: Introduction to fundamentals ideal isothermal reactors - single-electrochemical reactions kinetics of electrochemical reactions - mechanism determination and multistep processes multiple electrochemical reactions with interphase mass transport dynamics and real flow in electrolytic reactors simultaneous mass transfer and chemical reaction the influence of migration and current and potential distribution on reactor design energy balance, heat transfer and optimization.
TL;DR: In this paper, the properties of a carbon felt electrode have been experimentally investigated with special attention to its possible application in the electrochemical recovery of heavy metals, by means of the reduction of ferricyanide and cupric ions for a flow-by electrode operating under limiting current conditions.
Abstract: The properties of a carbon felt electrode have been experimentally investigated with special attention to its possible application in the electrochemical recovery of heavy metals. The mass transfer process has been studied by means of the reduction of ferricyanide and cupric ions for a flow-by electrode operating under limiting current conditions. An empirical correlation between the Sherwood and Reynolds numbers has been used to compare the experimental data with those obtained by other authors for different porous electrodes.
TL;DR: In this article, a resistance-in-series model is used to describe the pervaporation performance of elastomeric membranes in the removal of volatile organic components from water.
TL;DR: In this paper, two different kinetic models (kinetic models 1 and 2) are used to describe the dynamics of the adsorption mechanism when β-galactosidase is adsorbed onto monoclonal antibody immobilized on porous silica particles.
TL;DR: In this article, the authors developed a mass transfer correlation between heat and mass transfer for droplet evaporation in high-temperature air streams at intermediate Reynolds numbers, which accounts for the effects of convection, droplet heating, surface blowing and variable thermophysical properties.
TL;DR: In this article, a nonlinear evolution equation describing the shape of the film interface as a function of space and time is derived, and its stability is examined using linear theory, showing that when there is either no mass transfer or there is evaporation from the film surface, infinitesimal disturbances decay for small wave numbers and are transiently stable for larger wave numbers.
Abstract: A fixed volume of liquid is placed on a horizontal disk spinning at a constant angular speed. The liquid forms a film that thins continuously due to centrifugal drainage and evaporation or thins to a finite thickness when surface absorption counterbalances drainage. A nonlinear evolution equation describing the shape of the film interface as a function of space and time is derived, and its stability is examined using linear theory. When there is either no mass transfer or there is evaporation from the film surface, infinitesimal disturbances decay for small wave numbers and are transiently stable for larger wave numbers. When absorption is present at the free surface, the film exhibits three different domains of stability: disturbances of small wave numbers decay, disturbances of intermediate wave numbers grow transiently, and those of larger wave numbers grow exponentially.