Showing papers on "Mass transfer coefficient published in 1976"
TL;DR: In this article, the theory of diffusional release of a solute from a polymeric matrix where the initial loading of solute is less than or greater than the solubility limit has been reviewed and extended.
194 citations
TL;DR: In this article, the authors investigated the effect of the oil phase on the bubble-to-emulsion mass transfer coefficient and showed that the effect is independent of the volume fraction of n-alkans and oleic acid.
82 citations
TL;DR: In this paper, the authors have developed a new system for the measurement of effective interfacial area, a, by the chemical method which allow the use of hydrocarbon solvents, such as toluene, xylene, etc; polar solvent,such as benzyl alcohol, cyclohexanol, etc.
58 citations
TL;DR: In this paper, the mass transfer coefficient kls was measured over a range of flow rates of gas Ug = 0-100 cm and liquid Ul = 0.05-25 cm in a column packed with spheres of three different diameters.
Abstract: Mass transfer coefficient kls was measured over a range of flow rates of gas Ug= 0-100 cm.s-1 and liquid Ul=0.05-25 cm.s-1 in a column packed with spheres of three different diameters d=2.8-12.7 mm. The systems used were the dissolution of benzoic acid in water and diffusionlimited oxidation of brass with dichromate ion in sulfuric acid solution. The effect of Ug on kls is not found at all in gas continuous flow, is the greatest in pulse flow and becomes less significant again in dispersed bubble flow. The value of kls increases rapidly around the transition from gas continuous to pulse flow. The enhancement factor β (=kls in two-phase flow/kls in single-phase flow) increases from 1.2 to 2 with increasing d in gas continuous flow while it equals the reciprocal of liquid holdup in pulse and dispersed bubble flows. A liquid-film analogy in gas continuous flow and a single-phase analogy in pulse and dispersed bubble flows are proposed and the experimental results are examined in the light of them.
54 citations
TL;DR: In this article, a method for calculating the mass transfer coefficient in a biological film system, under turbulent flow conditions, is presented, and it is experimentally found that fluid velocity has a positive effect on the rate of substrate utilization when the system is operated in other than the kinetic regime.
Abstract: A method for calculating the mass transfer coefficient in a biological film system, under turbulent flow conditions, is presented. It is experimentally found that fluid velocity has a positive effect on the rate of substrate utilization when the system is operated in other than the kinetic regime. A correlation is developed which indicates a dependence of the mass transfer coefficient on the fluid velocity raised to the 0.7 power.
49 citations
TL;DR: In this article, a model to estimate the mass transfer coefficient in aqueous solutions of surfactants has been proposed, where the effect of a surfactant has been expressed by introducing the retardation coefficient, which indicates the degree of a retardation of surface flow at the gas-liquid interface.
45 citations
TL;DR: In this paper, mass transfer rates have been measured for bubbles containing ozone injected into an air-fluidized two-dimensional bed of particles, and the experimental value is consistent with a model which bases mass transfer purely on the throughflow predicted by Murray.
37 citations
TL;DR: In this article, the authors investigated the effect of governing parameters on the occurrence of multiple steady states in axial dispersion and external gas-to-solid heat and mass transfer.
36 citations
TL;DR: From chromatographic adsorption experiments, ad-sorption equilibrium constants and particle-to-gas mass transfer coefficients were determined by fitting tracer output signals in the time domain this paper.
35 citations
TL;DR: A very high-efficiency liquid-liquid chromatographic (LLC) system based on 5- and 20-μm diameter porous silica microspheres was used to effect radiochemical separations of metal ions that required very large decontamination factors and/or high speeds.
29 citations
TL;DR: In this article, the semi-empirical model of limiting current on flow-through porous electrodes, as described before by Sioda, is compared with the usual presentation of mass transfer processes involving mass transfer coefficients and dimensionless correlations.
TL;DR: In this paper, the axial dispersion in the liquid-phase of a gas-liquid downflow through a packed column was studied with air and water flowing concurrently in a 8.0 cm diameter column with glass spheres of 0.12, 0.26 and 0.43 cm.
Abstract: The axial dispersion in the liquid-phase of a gas-liquid downflow through a packed column was studied with air and water flowing concurrently in a 8.0 cm diameter column with glass spheres of 0.12, 0.26 and 0.43 cm. The impulse response was calculated numerically from the two signals measured at two cross-sections in the bed. The response was characterized by both a peak and a very long tail, and could be represented satisfactorily by using the PDE model in which the mass transfer between the dynamic and the stagnant holdups in addition to the axial dispersion in the dynamic holdup was taken into account. Four parameters appearing in the PDE model were determined by means of the time domain curve fitting method. Peclet number which was based on the actual velocity in the dynamic holdup ud had a constant value of 0.43 for Re''(=udρdp/μ) 400. The volumetric mass transfer coefficient was correlated as a function of particle size, liquid and gas velocities. The total liquid holdup agreed well with the literature data. The fraction of the dynamic holdup varied in the range of 0.6 to 0.95 depending on the particle size and the gas and the liquid velocities. The correlation of the dynamic liquid holdup was given graphically.
01 Sep 1976-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this paper, the partial pressure of oxygen and the gas-film mass transfer coefficient on the particle surface were separately evaluated in gas bubbles and in the emulsion phase, and the calculated fractional reaction coincided well with the experimental results.
Abstract: Kinetics of oxidation of ZnS particles in a batch-type fluidized bed were studied at temperatures between 800 and 910°C. A two-phase model was employed for the fluidized bed, and the partial pressure of oxygen and the gas-film mass transfer coefficient on the particle surface were separately evaluated in gas bubbles and in the emulsion phase. The calculated fractional reaction coincided well with the experimental results. The difference in O2 partial pressure between gas bubbles and emulsion phase was found to be fairly large especially under the vigorous fluidizing condition. Furthermore, it was shown from the mathematical model that the reaction of ZnS particles in the gas bubbles is negligible because of the extremely low solid concentration and that the overall rate of reaction in the emulsion phase is virtually controlled by the rate of gas-film mass transfer at higher temperature. The resistance of interfacial reaction within the particle also becomes significant when the temperature is lowered.
TL;DR: In this article, the Danckwerts' pseudo-first order reaction method was used for the determination of interfacial area and mass transfer coefficients on sieve plates, and the results of investigations of the kinetics of the chemical reactions involved are also given.
TL;DR: In this article, the application of oscillatory flows to electrochemical processes was found to increase the rate of mass transfer and improve the quality of deposit and various mechanisms to which this phenomenon is attributable are discussed and expressions for the average rate ofmass transfer, resulting thereof, are derived.
Abstract: The application of oscillatory flows to electrochemical processes was found to increase the rate of mass transfer and improve the quality of deposit. Various mechanisms to which this phenomenon is attributable are discussed and expressions for the average rate of mass transfer, resulting thereof, are derived. Comparison with experimental data indicates that the stretched-film concept, although an oversimplification of the physical situation, is most successful in correlating the data.
TL;DR: In this paper, the authors found that mass transfer from fixed volume drops with forced internal circulation increases at Reynolds numbers which corresponded to those observed for the development of internal circulation patterns within the drop.
Abstract: The presence of internal circulation in forming liquid drops has a significant effect on mass transfer rates. For the systems studied, no circulation was observed below a Reynolds number of 9.7. For Reynolds numbers between 9.7 and 34.4, transition from zero circulation to complete circulation during the entire drop formation period occurred. In studies on the rate of mass transfer from fixed volume drops with forced internal circulation, increases in mass transfer rates were found at Reynolds numbers which corresponded to those observed for the development of internal circulation patterns within the drop.
TL;DR: In this paper, the effect of forced turbulence on interfacial mass transfer between two liquid phases is investigated and a theoretical model is derived on the assumption that the mass transfer is controlled by unsteady diffusion into the vortices of the viscous subrange of the range of universal equilibrium.
TL;DR: In this paper, the performance of a cocurrent up-flow this paper with glass beads was studied using the oxidation reaction of sodium sulfite, at a reaction temperature of 20°C.
Abstract: Packed-bed cocurrent up-flow reactors gave better results than conventional trickling flow reactors in hydrodesulfurization of heavy oil. To find the characteristics of this up-flow type reactor, liquid-phase mass transfer coefficient, gas-liquid interfacial area and gas holdup in a column packed with 0.1, 0.28 or 0.43 cm glass beads were studied using the oxidation reaction of sodium sulfite. Experiments were carried out at a reaction temperature of 20°C. Superficial liquid and gas velocities based on empty column, ul and ug, were 1-6 and 0.5-6cm/sec, respectively, for any size of glass beads. With the values of ul and ug, glass beads bed remained stationary, expanded or fluidized. Stagnant gas holdup was observed under the condition of ul
TL;DR: In this paper, the effect of uniform and non-uniform magnetic fields on cathodic mass transfer during dc electrolysis in cylindrical cells is analyzed and the absence of a limiting current past moderate magnetic fields strengths is experimentally demostrated.
TL;DR: In this paper, the free convection mass transfer behavior of horizontal screens has been investigated experimentally using an electrochemical technique involving the measurement of the limiting currents for the cathodic deposition of copper from acidified copper sulphate solutions.
Abstract: The free convection mass transfer behaviour of horizontal screens has been investigated experimentally using an electrochemical technique involving the measurement of the limiting currents for the cathodic deposition of copper from acidified copper sulphate solutions. Screen diameter and copper sulphate concentration have been varied to provide a range ofSc.Gr from 22×108 to 26×1010. Under these conditions, the data for a single screen are correlated by the equation:Sh=0.375(Sc.Gr)0.305 Results have been compared with previous work on free convection at horizontal solid surfaces where mass transfer coefficients are somewhat lower.
TL;DR: In this paper, a correlation for the volumetric mass transfer coefficient was developed semi-empirically based on the analogy between mass and momentum transfer in vertical upward two-phase flow by desorbing carbon dioxide from liquid phases of water, aqueous glycerine and malt honey.
Abstract: Liquid-side volumetric mass transfer coefficients were obtained in vertical upward two-phase flow by desorbing carbon dioxide from liquid phases of water, aqueous glycerine and malt honey. Measurements were made mainly in the froth and the wavy annular flow using tubes of 10, 18 and 25 mm i.d. A correlation for the volumetric mass transfer coefficient was developed semi-empirically based on the analogy between mass and momentum transfer. Experimental data were correlated by two equations in dimensionless form corresponding to the two flow mechanisms of pseudo-laminar flow and turbulent flow.
TL;DR: Batch 316-type cellulose acetate membranes were characterized in terms of pure water permeability constant, solute transport parameter, and mass transfer coefficient with a reference system of aqueous sodium chloride solution as discussed by the authors.
Abstract: Batch 316-type cellulose acetate membranes were characterized in terms of pure water permeability constant, solute transport parameter, and mass transfer coefficient with a reference system of aqueous sodium chloride solution. These membranes were used in the determination of reverse osmosis characteristics such as product rate and solute separation in the case of uranium sulfate solutions of different concentrations (100 to 8000 ppm) in the feed solutions. A long-term test extending over a week has been carried out with dilute uranium solutions. Reverse osmosis treatment of synthetic mine water sample showed satisfactory performance of the membranes in the separation of metal ions.
TL;DR: In this paper, the authors measured dispersion and mass transfer coefficients for Bandera, Berea, Cottage Grove, Noxie and Torpedo sandstones ranging in permeability from 12 to 420 md.
Abstract: Linear dispersion and mass transfer coefficients were measured for Bandera, Berea, Cottage Grove, Noxie and Torpedo sandstones ranging in permeability from 12 to 420 md. Experimental data were obtained from analysis of effluent concentration changes resulting from a step increase of the influent tracer concentration. Brine and a tritium-labeled brine solution were used as tracers. Coefficients of dispersion were calculated by comparing the experimental data with solutions of the diffusion equation by three methods: (1) analytical solution of the diffusivity equation, (2) a graphical method, and (3) numerical, finite difference, solution. The three methods yielded equivalent results. Tailing of the effluent response curves was interpreted by introducing two additional parameters to the diffusivity equation: (1) the immobile fluid fraction of the porous medium determined independently by capillary pressure measurement and (2) a mass transfer coefficient to account for tracer interaction with the immobile fluid fraction. The Berea sandstone exhibited the sharpest displacement front and the least amount of tailing, making it the best selection for experiments in which steep displacement fronts are encountered, such as miscible displacement. Molecular diffusion measurements were used to calculate tortuosity factors for each of the five sandstones using two pairs of gases: hydrogen--air and hydrogen--nitrogen.more » These results are equivalent to tortuosities independently determined by electrical conductivity measurements.The coefficient of dispersion and the tortuosity of sandstones are shown to be excellent parameters for characterization of geologic materials for the study of fluid flow properties.« less
TL;DR: In this article, the influence of vectored suction or injection on the flow and heat transfer at the stagnation point of a two-dimensional body and an axisymmetric body with allowance for the effects of variable gas properties was studied.
Abstract: The paper studies the influence of vectored suction or injection on the flow and heat transfer at the stagnation point of a two-dimensional body (a cylinder) and an axisymmetric body (a sphere) with allowance for the effects of variable gas properties. The analysis is based on the boundary-layer equations in dimensionless form for the steady compressible fluid with variable properties in the stagnation region of a two-dimensional or an axisymmetric body with tangential and normal surface mass transfer under similarity requirements. It is shown that the variation of the density-viscosity product across the boundary layer has a strong effect on the skin friction and heat transfer. This gives rise to a point of inflection which can be removed by suction and by increasing the wall temperature. The skin friction and heat transfer are significantly affected by the pressure gradient parameter.
TL;DR: In this article, the reverse osmosis separation behavior of some metal salts of Cu2, Ni2 +, Fe3+, and A13+ have been studied in terms of pure water permeability constant, solute transport parameter, and mass transfer coefficient with a reference system of aqueous sodium chloride solution.
Abstract: Reverse osmosis separation behavior of some metal salts of Cu2 +, Ni2 +, Fe3+, and A13+ have been studied. The cellulose acetate membranes used were characterized in terms of pure water permeability constant, solute transport parameter, and mass transfer coefficient with a reference system of aqueous sodium chloride solution. The importance of the chemical species present in solution and its effect on the degree of separation has been illustrated. Correlation between the percent solute separation and the equilibrium constant for the formation of ion-pairs in solution has been established. Reverse osmosis treatment has been applied to an acid mine-water solution, and the suitability of this process is discussed.