Presence Of Mass Transfer Research Articles

Ionic mass transfer in presence of turbulence promoters in a circular conduit

Ionic mass transfer in a circular conduit in the presence of ring promoter assembly is measured by limiting current technique using diffusion controlled electrochemical reactions (reduction of ferricyanide and oxidation of ferrocyanide). A supporting rod on which rings are mounted at equidistance is concentrically fixed in the conduit of 0.05 m I.D. to augment the mass transfer rates. Cross-sectional diameter of the ring is changed from 0.0065 m to 0.0125 m and the spacing in between the rings is varied from0.03 m and 0.15 m respectively. The improvement in mass transfer coefficients is up to 6.5. The data are correlated by the following dimensionless equation. ▪

Drop Sizes in Liquid Membrane Dispersions

The effect of hydrodynamic conditions and physical properties on the characteristics of an emulsion dispersion in a stirred tank was studied in the presence of mass transfer, in an attempt to identify the parameters for Sauter mean diameter data correlation in emulsion liquid membranes. The organic phase of the water-in-oil emulsion contained the cadmium extractant Cyanex 302 and an emulsion stabilizer, and the dispersion continuous phase was an aqueous solution of phosphoric acid containing cadmium. Variations in emulsion viscosity and interfacial tension were achieved by changing the extractant and surfactant concentrations. The dispersion drop size distribution was measured from photographs taken with a high-speed video camera system attached to an endoscope. It was found that the emulsion physical properties, emulsion swelling, and operating conditions were interrelated in a complex way. However, emulsion swelling seemed to lump together the effect of some of the parameters on globule size, which made possible the development of a simple correlation for the Sauter mean diameter in terms of We-0.6, emulsion swelling percentage, and empirical correction factors for emulsion viscosity and dispersed-phase holdup. A modified Rosin−Rammler probability distribution function fitted well the globule size distribution data.

Extractive Separation of Praseodymium and Neodymium by Di(2-Ethylhexyl) Phosphoric Acid in the Presence of Water-Soluble Complexing Agents Using an Electrostatic Liquid-Liquid Contactor

A novel type of liquid-liquid contactor was developed in which a DC electric field effectively functioned by dispersing an aqueous phase very finely into an organic phase, agitating the organic phase with the droplets and separating both phases. That is, the hydrodynamic behaviour was performed without any other means such as liquid dispersers, agitators and settlers. Both phases contacted satisfactorily in a crosscurrent flow in the contactor. The population behaviour of the droplets in the contactor was examined in terms of the dispersed phase holdup and the size distribution of the droplets. The droplet size in the electric field showed different results in the absence and in the presence of mass transfer. The extraction characteristics of praseodymium (Pr) and neodymium (Nd) from an aqueous phase containing a water soluble complexing agent (EDTA, DTPA and their mixtures) to an organic phase (ISOPAR M) containing an extractant (D2EHPA) were also experimentally examined. Mass transfer results showed that the higher the applied voltage, the better was the degree of separation of both metals. This is attributed in part to an increase in the frequency of the coalescence-redispersion of the droplets and of the droplet formation.

Kinetics of iron oxide reduction from CaO‐MgO‐FeOn‐SiO2 slags by silicon dissolved in liquid iron

At steelmaking temperatures, the kinetics of slag‐metal reactions is usually determined by mass transfer. This occurs in two ways: normal mass transfer which is induced by stirring, and mass transfer by interfacial convection induced by interfacially active elements like oxygen and sulphur. In the present work, mass transfer during the reduction of iron oxide from a basic slag by silicon dissolved in liquid iron was studied under defined conditions of gas stirring by argon in MgO crucibles with 1500 g iron and 250 g slag. The variations of the FeO content in the slag and the silicon content in the iron during the reaction were measured by sampling. Trials were carried out with stirring gas flow rates between 1 and 20.4 l/h(STP). The experimental data were evaluated with the multi‐component transport model in order to determine the mass transfer coefficients of the reaction components. Simultaneously, the coefficients of normal mass transfer were calculated with the boundary layer theory of liquid‐liquid mass transfer for non‐turbulent flow conditions. The measured mass transfer coefficients were by a factor 2.5 larger than the theoretically calculated. The difference indicates the presence of mass transfer by interfacial convection. Mass transfer by interfacial convection is superimposed to normal mass transfer.

Slip flow in a two-component plasma model with radiative heat transfer

The paper studies the flow of a low density thermally radiating two-component plasma in the presence of mass transfer and Hall current. Since the density is low, an optically thin grey gas approximation is adopted for the radiative heat transfer. Also, at high temperatures, the Arrhenius activation energy is important. For fully developed flow, the problem is modelled by coupled nonlinear differential equations from the incompressible Navier-Stokes equations, together with slip boundary conditions. Exact solutions are inconceivable, but various asymptotic solutions are derived, and these solutions are discussed quantitatively.

Structure Formation in Heterogeneous Polymer Mixtures in the Presence of Mass Transfer across Interfaces

Structure Formation in Heterogeneous Polymer Mixtures in the Presence of Mass Transfer across Interfaces

Binding kinetics of antigen by immobilized antibody: influence of reaction order and external diffusional limitations

The influence of reaction order and external mass transfer limitations on the binding kinetics of antigen in solution to antibody covalently or non-covalently attached to a cylindrical fiber-optic biosensor is presented. Both single-step and dual-step binding of antigen to antibody is considered. The rate of attachment of antigen to antibody is linear for all reaction orders in the time frame (100 min) considered. The rate of attainment of saturation levels of antigen in solution close to the surface is very rapid (within 20 min). An increase in the presence of mass transfer (denoted by a Damkohler number increase) decreases the saturation level of the antigen close to the surface, and the rate of antigen attachment to the antibody covalently or non-covalently bound on the surface for one-half, one, one and a half, and second-order reaction. As intuitively expected, an increase in the initial antigen concentration in solution increases the saturation level of the antigen close to the surface, and the rate of antigen attachment to the antibody covalently bound on the surface for all the reaction orders considered. Non-dimensional plots presented in the analysis help extend the analysis to different antigen-antibody systems. A decrease in the external diffusional limitations has an effect of decreasing the effect of reaction order on the saturation levels of antigen close to the surface and the rate of attachment of the antigen in solution to the antibody on the surface.

Constancy of period in TX Ceti

A slightly improved period (P=0.d7408401) of the eclipsing binary system TX Ceti has been given, which is based on all available times of minima. The O-C diagrams based on the period given in PPEN (1980) and based on the new period, have been given. The period of TX Ceti shows fair constancy between the time interval 1928 to 1988. The present O-C diagrams do not confirm, either the presence of a third body or the presence of mass transfer as suggested earlier.

Steady state hydrodynamics and mass transfer characteristics of a karr extraction column

AbstractThe steady state hydrodynamics of the holdup in a 15 cm column agree quite well with mechanistic predictions at conditions approaching flooding. In the presence of mass transfer (acetic acid from the dispersed kerosene phase to the continuous water phase), the holdup data below flooding are not well predicted by the model due to enhanced droplet coalescence. The prediction of holdup at flooding is a function of the ratio of the flow rates but is independent of the physicochemical properties of the extraction system, and therefore can be used to estimate the flooding holdup regardless of the occurrence of mass transfer. In the second part of the paper, steady state mass transfer characteristics of the column were also simulated using a mechanistic model. Despite the difficulty of estimating parameters such as the mass transfer coefficient, the model curves could be arbitrarily adjusted to fit observed exit concentrations. These steady state results provide useful insights on the non‐linearity of the system from a control viewpoint.

Radio emission from symbiotic variables: CI Cygni, Z Andromedae, and EG Andromedae - Temporal variability as clues to the nature of symbiotics

A continuing survey of interacting binary systems has yielded first detections of the symbiotic variables CI Cyg and EG And and reproduced previous flux measurements for Z And. The CI Cyg observation implies considerable radio variability for some symbiotics, while the radio flux from Z And indicates this object has been reasonably stable in the radio for years. Rapid radio variability may indicate the presence of mass transfer through an accretion disk. 27 refs.

Photoelectric study of AW UMa

UBV photoelectric photometry of the eclipsing binary system AW UMa has been presented. A slightly improved period of 0 . d 4387304 has been given. The colour of the system has been discussed. Eccentricity is present in the system. Light and colour curves show that intrinsic light variations may be present in the system. The presence of mass transfer is a possibility.

Mass transfer effects in polycondensation reactors wherein functional groups are not equally reactive

AbstractThree simplified models of polycondensation reactors are considered in which the condensation product is continuously removed by application of vacuum. Reversible polycondensation reactions of monomers violating the equal reactivity hypothesis have been simulated in these reactors. The effect of various rate and reactor design variables on the molecular weight distribution (MWD) and its moments is studed. It is observed that when the reverse reactions are rapid, the results are fairly sensitive to the level of vacuum applied and to the mass transfer resistance; whereas when the forward reactions predominate, results lie very close to earlier plots for the corresponding irreversible polymerizations. These reactor variables then have relatively small influence on the MWD. Splitting of the MWD curves for odd and even values on n is observed under certain conditions, the effects being more pronounced in the presence of mass transfer than in its absence.

Liquid-liquid jet breakup under conditions of relative motion, mass transfer and solute adsorption

A linear hydrodynamic stability analysis of a liquid jet in relative motion through a second liquid in the presence of mass transfer between them predicts a significant effect of mass transfer direction and driving force and solute adsorption on jet length. Results of experiments in which acetone transfers between benzene jets and water in the presence and absence of adsorbing surfactant agree qualitatively with most of the predictions of the theory.

Mass transfer in presence of unconfined interfacial convection

Mass transfer in presence of unconfined interfacial convection

Distribution of a trace element in a boundary layer with mass transfer

A theory is presented for the downstream distribution of a tracer injected into a boundary layer of a flat plate or cone with self-similar mass transfer. The tracer, which is injected over a finite length of the surface, is assumed to be chemically inert. Its behavior is controlled by a frozen diffusion equation. The assumption of constant density-viscosity product, and unit Schmidt number results in a linear partial differential equation for the seed mass fraction. This is solved analytically in series form by separation of variables, and numerically by a finite difference technique. It is shown that far downstream of the tracer injection region the analytical results reduce to a simple form; namely, the mass concentration profile is proportional to the local shear even in the presence of mass transfer. However, near the tracer injection region, even the first ten terms are insufficient to yield profiles comparable to those produced by the numerical integration scheme.

Measurement of Contact Angles in the Presence of Mass Transfer

Low distillation and absorption efficiencies in gas/liquid contacting equipment have been attributed to liquid film breakdown and underwetting. A study of a model simulating these conditions has resulted in observations of contact angles when mass transfer is occurring.

AN INTEGRAL METHOD FOR CALCULATING HEAT AND MASS TRANSFER IN LAMINAR BOUNDARY LAYERS

An integral method previously used successfully in several kinds of boundary layer problems has been extended to treat simultaneous heat and mass transfer in a binary-mixture laminar boundary layer when the pressure is uniform. The principal results are two pairs of dual integral relations arising from solutions to the integral concentration and energy equations. One pair connects the surface mass transfer rate and surface concentration of injected gas; the other relates surface temperature and heat transfer rate in the presence of mass transfer. Only the cases of helium and air injection into an undissociated air stream are discussed in detail, but the method can be applied to problems involving other gases. The approximate results agree quite well with some numerical solutions and with recent experimental results for which no numerical solutions are available.

Surface Renewal and Molecular Diffusion in Interphase Mass Transfer

IN 1953 Lewis and Pratt1 described violent spontaneous movements of the liquid-liquid interface which they observed during measurements of interfacial tension in the presence of mass transfer by the drop-weight method. These phenomena have since been investigated more fully2–5. It is now generally accepted that they are due to the formation of local gradients of interfacial tension caused by local variations of solute concentration at the interface as the result of mass transfer.