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Showing papers on "Mass transfer coefficient published in 1988"


Journal ArticleDOI
TL;DR: In this article, it was shown that under certain conditions partially wetted surfaces yield practically the same drying rate as entirely wetted ones, and that less than 1% of the surface needed to be activated in order to give the same reaction rate such as an entirely activated one.

138 citations


Journal ArticleDOI
TL;DR: The hollow fiber contained liquid membrane (CLM) is a thin liquid film contained in the interstices of two sets of intermingled microporous hollow fine fibers as mentioned in this paper.
Abstract: The hollow fiber contained liquid membrane (CLM) is a thin liquid film contained in the interstices of two sets of intermingled microporous hollow fine fibers. Organic CLM-s have been used here for the separation of solutes from an aqueous feed into an aqueous strip. Solutes studied are phenol and acetic acid. The separations are carried out in either hydrophilic or hydrophobic hollow fiber CLM permeator modules, using a variety of organic liquids (e.g., decanol, methyl isobutyl ketone, xylene) as membranes. First-order models have been developed to predict the overall solute transfer coefficients adequately. The transfer coefficient can be enhanced significantly when a chemical reaction is carried out on the strip side using NaOH. The advantages of the CLM structure include operational stability, independent control of membrane phase pressure, automatic replenishment of the lost membrane liquid, and absence of the need for preequilibration. These features are demonstrated here, even for systems with considerable aqueous-organic mutual solubilities.

102 citations


Journal ArticleDOI
TL;DR: In this paper, the reduction and subsequent sulfidation of single cylindrical pellets of ZnFe2O4 have been studied in a microbalance reactor and the time-conversion results during sulfidation are consistent with the unreacted core model assuming the global kinetics are controlled by mass transfer and pore diffusion.

89 citations


Journal ArticleDOI
TL;DR: The dissolution kinetics of ionizable drugs (weak acids or bases) are analyzed with a mathematical model derived from the theory of mass transfer with chemical reaction and the results are shown to be in accord with experimental data taken from the literature.
Abstract: The dissolution kinetics of ionizable drugs (weak acids or bases) are analyzed with a mathematical model derived from the theory of mass transfer with chemical reaction. The model assumes that the overall process is diffusion limited, that all the reactions are reversible and instantaneous, and that dissolution and reaction are limited to the stagnant fluid film adjacent to the solid phase. Dissolution into buffered and unbuffered aqueous solutions are considered separately, with covenient analytical solutions obtained in both cases. In addition, equations for the time to partial and complete dissolution are derived. The dissolution rate is shown to be dependent on the pK a and intrinsic solubility and the medium properties, i.e., pH, buffer capacity, and mass transfer coefficient. Equations of a form analogous to the nonionized case are derived to account explicitly for all these factors, with dissolution rates expressed in terms of the product of a driving force (concentration difference) and resistance (inverse of mass transfer coefficient). The solutions are in an accessible analytical form to calculate the surface pH and subsequently the surface concentrations driving the drug dissolution. Numerical examples to illustrate dissolution into unbuffered and buffered media are presented and the results are shown to be in accord with experimental data taken from the literature.

81 citations


Journal ArticleDOI
TL;DR: In this paper, a mathematical model was developed for the simulation of non-ideal displacement chromatography, which incorporates finite mass transport to the solid adsorbent by using a linear driving force approximation with a coupled external film and internal pore mass transfer coefficient.

70 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that the rate constant for electron transfer across immiscible electrolytes at the potential of zero charge is very convenient for the comparison of measured values with electron transfer theories.

67 citations


Journal ArticleDOI
TL;DR: In this article, a one-dimensional Fickian diffusion model for entrainment of interstitial soil water by overland flow is modified to account for early non-Fickian mass transfer observed during laboratory runoff experiments.
Abstract: A one‐dimensional Fickian diffusion model for entrainment of interstitial soil water by overland flow is modified to account for early non‐Fickian mass transfer observed during laboratory runoff experiments. Modification involves specifying a time‐dependent diffusion coefficient that decreases with time and asymptotically approaches the constant Fickian value with time. Results show that this asymptotic diffusion coefficient varies with the square of the quantity V*K, where V* is shear velocity and k is media permeability. Modifying the model entails the development of type curves for a range of convective time scales, or times of non‐Fickian mass transfer. A graphical curvematching technique using dimensionless cumulative mass loss data provides a means of estimating the entrainment, or mass transfer, coefficient as a function of the convective time scale. This procedure shows that the entrainment coefficient varies linearly with V*k, Reasonable prediction of mass loss results using the asymptotic diffus...

67 citations


Journal ArticleDOI
TL;DR: It was found that the overall reactor mass transfer coefficient KLA could be correlated to the pneumatic power of gas input per total dispersion volume (P/VD) and to the true riser superficial gas velocity JGR for all experimental conditions examined.
Abstract: The interrelationships between the three parts of the air lift reactor, the riser, the downcomer, and gas-liquid separator, were examined with relation to the overall mass transfer in the reactor. This involved studying the mass transfer of oxygen from the gas phase to the liquid phase for 20 different reactor geometries. Both one- and two-sparger systems were studied. It was demonstrated that the gas-liquid separator plays a major role in reactor behavior and must be considered in reactor design. It was found that the overall reactor mass transfer coefficient KLA could be correlated to the pneumatic power of gas input per total dispersion volume (P/VD) and to the true riser superficial gas velocity JGR for all experimental conditions examined. The KLA is directly related to the P/VD with an exponent of approximately 1. "Two-sparger" systems, where an auxiliary gas sparger is placed near the downcomer entrance, have higher ab solute values for KLA than single-sparger systems.

61 citations


Journal ArticleDOI
TL;DR: In this article, a model for particle-fluid heat/mass transfer in multi-particle systems is proposed based on a boundary layer formulation for individual particles in the sphere assemblage, which enables a unified consideration of fixed, distended, fluidized beds as well as isolated spheres.

58 citations


Journal ArticleDOI
TL;DR: In this article, a comprehensive theory of mass transfer with chemical reaction in the presence of a microphase has been developed using Higbie's penetration theory as well as the surface renewal theory due to Danckwerts.

53 citations


Journal ArticleDOI
TL;DR: In this paper, a modified Henry's law coefficient of 1.09 x lo-' kmol/m3. bar can be regarded as constant over the temperature range 293-435 K.
Abstract: Mass transfer coefficients for the solution, without reaction, of oxygen in cyclohexane over a wide range of temperature and pressure have been measured in a flat interface reactor (FIR) and a gas sparged stirred-tank reactor (STR). Solubilities have also been measured and it is suggested that a modified Henry's law coefficient of 1.09 x lo-' kmol/m3 . bar can be regarded as constant over the temperature range 293-435 K. The physical mass transfer coefficient in the STR shows very little variation over this temperature range and a value of 3.5 x m/s can be assumed for 423-435 K. However, coefficients in the FIR increase with agitation rate as expected. The difference is ascribed to interference by neighboring bubbles in the transfer process, when diffusivities are high, and also to the lowering of surface tension at high temperatures. A model proposed by Gal-Or and Resnick is reviewed in its application to the present system.

Journal ArticleDOI
TL;DR: In this paper, the performance of modern dumped and structured packings for application in the field of thermal separation processes is evaluated based on extensive experimental investigations of rectification, absorption, and desorption systems.
Abstract: A report is presented on the performance of modern dumped and structured packings for application in the field of thermal separation processes. The evaluation of the results is based on extensive experimental investigations of rectification, absorption, and desorption systems. The following are indicated: the efficiency in terms of the number of theoretical stages per unit height or in terms of the height of transfer unit or volumetric mass transfer coefficient, the pressure drop per unit height as well as per theoretical stage or per gas phase transfer unit, and the liquid hold-up, whereby either the gas capacity factor or the liquid load was adopted as influencing parameter, and finally the maximum gas capacity factor as a function of the flow parameter. The results are presented in diagrams and tables.

Journal ArticleDOI
TL;DR: In this paper, the mass transfer coefficient of a vertical regular array of two lines of Raschig rings a short horizontal distance apart was measured for unhindered motion and for disturbed motion through a vertically regular array.

Journal ArticleDOI
TL;DR: In this paper, the mass transfer coefficients between solid particles and turbulent liquids were measured in agitated vessels, and a new correlation was presented to support the postulate that fine particles may stay in and move together with microeddies.
Abstract: The mass transfer coefficients between solid particles and turbulent liquids were measured in agitated vessels. For large particles characterized by large values of the specific power group (γ1/3d4/3/v), the measured mass transfer coefficients were in good agreement with Levins and Glastonbury''s correlation. For fine particles less than 100μm, however, the mass transfer coefficient deviated below their correlation, reaching more rapidly the theoretical limiting value Sh = 2 for molecular diffusion in an infinite stagnant fluid. This lends the first quantitative support to the postulate that fine particles may stay in and move together with microeddies. A new correlation for the mass transfer coefficient is presented. The effect of particle density and vessel diameter on the mass transfer coefficients was found to be negligible. Furthermore, the effect of solid particle concentration was found to be of little importance in the range of specific surface area up to at least 3000m2/m3 of liquid.

Journal ArticleDOI
TL;DR: In this article, a two-resistance mass transfer model based on film resistance and homogeneous solid phase diffusion has been presented for acid blue 25 onto peat in a batch adsorption system.

Journal ArticleDOI
TL;DR: In this paper, experiments were carried out on bubble stripping of aqueous solutions of five organic solutes and oxygen dissolved at initial concentrations ranging from 0.008 to 0.04kg⋅m-3.
Abstract: Experiments were carried out on bubble stripping of aqueous solutions of five organic solutes and oxygen dissolved at initial concentrations ranging from 0.008 to 0.04kg⋅m-3. Little interaction was found to exist among the solutes, as far as gas holdup and overall volumetric mass transfer coefficients at low concentrations are concerned. The liquid-side and gas-side volumetric mass transfer coefficients were obtained from measured overall coefficients. Correlations for the liquid-side volumetric mass transfer coefficients were obtained in terms of liquid-phase diffusivity and gas flow rate for two types of gas spargers: single-nozzle and porous-tube spargers. Correlations for the gas-side volumetric mass transfer coefficients were also obtained for these spargers.

Journal ArticleDOI
TL;DR: In this paper, the gas holdup and volumetric mass transfer coefficient of a plunging water jet in an air-water system were investigated and it was shown that kLa is directly proportional to gas hold up in two regions.
Abstract: This is an investigation of the gas holdup and the volumetric mass transfer coefficient of a plunging water jet in an air-water system. We sound kLa to be directly proportional to gas holdup in two regions. For the first time, this has been clarified in the plunging liquid jet system. The volumetric mass transfer coefficient and the gas holdup have been well correlated in terms of the Froude number, liquid jet length, nozzle diameter and vessel diameter.

Journal ArticleDOI
TL;DR: In this paper, the wall-to-liquid mass transfer coefficient, kw, was measured for both surfaces of a coaxially immersed tube and a column wall in packed and fluidi/ed bed systems with gas-liquid concurrent upflow.
Abstract: The wall-to-liquid mass transfer coefficient, kw, was measured for both surfaces of a coaxially immersed tube and a column wall in packed and fluidi/ed bed systems with gas-liquid concurrent upflow. Supplementary measurements of kw were carried out in openpipe liquid flow, gas-liquid two-phase upflow and packed and fluidized beds with single liquid flow. The value of kw in the three-phase fluidized bed increased with increasing gas flow rate, deviating from the value in the liquid-solid fluidized bed and approaching the value in the gas-liquid two-phase upflow, while it passed through a maximum value with respect to the liquid flow rate. The value of kw in the packed-bed operation increased with increasing liquid flow rate and with increasing gas flow rate. The values of kw for the inner tube and the column wall were shown to agree with each other. The values of kw in all the gas-liquid, liquid-solid and gas-liquid-solid systems examined were correlated well by a unified equation in terms of the energy dissipation rate per unit mass of liquid. An analogy existed between wall heat transfer and wall mass transfer in all the multiphase flow systems examined.

Journal ArticleDOI
TL;DR: In this paper, the effect that tight 180° bends have on locally enhancing the mass transfer, over the fully developed tube value, has been examined at Reynolds numbers up to 2.6 × 10 5.

Journal ArticleDOI
TL;DR: In this paper, a novel experimental system, well suited for mass transfer studies in liquids dispersed as droplets in a gas, was constructed, which produces monodisperse droplets by the controlled breakup of a cylindrical jet by a vibrating orifice.

Journal ArticleDOI
TL;DR: In this paper, the authors described the use of china clay for the removal of As(III) from aqueous solution at different concentrations, retention times, temperatures and pH of the solution.
Abstract: The present investigation describes the use of china clay for the removal of As(III) from aqueous solution at different concentrations, retention times, temperatures and pH of the solution. The process of removal follows first order rate expression and the uptake of adsorbate within the pores of china clay is also diffusion controlled. The equilibrium data of As(III) at various temperatures follow Langmuir isotherm. The mass transfer coefficient (sL) of As(III) diffusion has been determined at 20°, 30° and 40°C. Maximum removal was found at pH 8. In order to understand the mechanism of As(III) removal by china clay, thermodynamic parameters were calculated.

Journal ArticleDOI
TL;DR: In this paper, a two-phase two-impinging-stream absorber was operated with a CO 2 -water system, and it proved to offer a high effectiveness with respect to maintainability, operability and versatility, thus making it very attractive device for industrial applications.

Journal ArticleDOI
TL;DR: In this paper, the effects of particle size and liquid and gas flow rates on the solid-to-liquid mass transfer coefficient, Ks, in all the systems were investigated and the mass transfer coefficients were well correlated by the following equation proposed by Ohashi et al. in a packed bed with single liquid flow.
Abstract: Mass transfer from solid particles to liquid in gas-liquid-solid fluidization was experimentally investigated by means of an electrochemical method with 7-9 particle electrodes fixed at various radial positions in a column of 82.9 mm i.d. Supplementary measurements were also conducted for the solid-to-liquid mass transfer in single liquid flow, gas-liquid two-phase upflow and liquid-solid fluidization. The effects of particle size and liquid and gas flow rates on the solid-to-liquid mass transfer coefficient, Ks, in all the systems were investigated and the mass transfer coefficient was well correlated by the following equation proposed by Ohashi et al. for Ks in a packed bed with single liquid flow. Shs = 2 + O.51(E1/3dp4/3/V1)0.06Sc1/3where E is the energy dissipation rate per unit mass of liquid, dp the particle diameter, vl the kinematic viscosity of liquid, Shs the Sherwood number and Sc the Schmidt number. The value of E was expressed by the sum of the kinetic energy supply terms due to viscous drag force across a particle and to gas agitation.

Journal ArticleDOI
TL;DR: In this paper, the authors measured the liquid-phase mass transfer coefficient kL for a single CO2 bubble rising through liquid in a closed tube by observing the change of pressure within the bubble due to gas absorption into the liquid.

Journal ArticleDOI
TL;DR: In this article, the relevance of power dissipation as a criterion for the understanding and prediction of transfer and mixing efficiencies in contactors and chemical reactors is discussed, and it is concluded from the various examples that a direct relationship between the dissipated power and intensity of transfer or mixing can be established only under the two following conditions: local values must be considered at the point where the actual transfer/mixing occur, and not average values over the whole device.
Abstract: The aim of the present paper is the discussion of the relevance of power dissipation as a criterion for the understanding and prediction of transfer and mixing efficiencies in contactors and chemical reactors. After reviewing the approach of Le Goff to the energetic efficiency of exchangers, based on the deviations from Chilton-Colburn analogy, the following processes are studied: mass transfer between a flowing fluid and a reactive solid surface, transfer to a fixed object in a stirred vessel, macro- and micromixing of miscible fluids, and mass transfer in fluid-fluid contractors (especially gas-liquid reactors). It is concluded from the various examples that a direct relationship between the dissipated power and intensity of transfer or mixing can be established only under the two following conditions: local values must be considered at the point where the actual transfer and mixing occur, and not average values over the whole device, and power dissipation must be coupled to transfer or mixing and appear physically as the driving force of the process.

Journal ArticleDOI
TL;DR: In this article, a mathematical model describing the heat and mass transfer processes that occur during sorption of water vapor in a dehumidifier consisting of parallel channels lined on either side width desiccant felt, is presented.
Abstract: A mathematical model describing the heat and mass transfer processes that occur during sorption of water vapor in a dehumidifier consisting of parallel channels lined on either side width desiccant felt, is presented. The model includes both gas-side and solid-side resistances for thermal and mass transport. The moisture transport in the desiccant is expressed by considering both gas phase diffusion and surface diffusion. The heat and mass transfer in the desiccant matrix occurs simultaneously and is coupled by an equilibrium sorption relation which is applied locally within the desiccant. Solutions are obtained by using an explicit finite-difference scheme. The effect of heat and mass transfer Biot numbers and other system parameters on the performance of an adiabatic open-cycle cooling system are investigated.


Journal ArticleDOI
01 Sep 1988
TL;DR: In this paper, an experimental study was carried out on heat and mass transfer rates, growth rates and the density of frost layers on a flat plate in forced convection conditions, where the density and thickness of the frost layers were correlated by the dimensionless parameters introduced in the authors' previous paper.
Abstract: An experimental study was carried out on heat and mass transfer rates, growth rates and the density of frost layers on a flat plate in forced convection conditions. The density and thickness of the frost layers were correlated by the dimensionless parameters introduced in the authors' previous paper [6]. Measured density and thickness of the frost layers are compared with those in natural convection conditions and with those measured by other investigators. It is shown that these parameters can also be used to generalize the density and growth rates of frost layers developed under forced convection conditions.

Journal ArticleDOI
TL;DR: In this paper, a gas cylone is sprayed in the center of a gas cylinder, and the centrifugal field created by the rotating gas accelerates the droplets in radial direction towards the wall.

Journal ArticleDOI
TL;DR: In this article, a new concept of a specific power group, proposed previously for correlating the mass transfer between a liquid and particles fixed in the liquid with a low level of turbulence, is discussed in comparison with the conventional concept of specific power groups from the Kolmogoroff theory.