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Mass transfer models for oxygen-water co-current flow in vertical bubble columns

Garcia, Valdemar; Teixeira, João Sobrinho
Fonte: Bentham Science Publishers Publicador: Bentham Science Publishers
Tipo: Parte de Livro
ENG
Relevância na Pesquisa
666.652%
The present work reports a theoretical and experimental study of mass transfer for oxygen-water co-current flow in vertical bubble columns. The axial dispersion of liquid phase was also studied. Experiments were carried out in a 32 mm internal diameter and 5.35 and 5.37 m height columns. The superficial liquid velocity ranged from 0.3 to 0.8 m/s and volumetric flow rate ratio of gas to liquid ranged from 0.015 to 0.25. Mathematical models were developed to predict concentration of gas dissolved in the liquid as function of different physical and dynamic variables for two-phase cocurrent downflow and upflow. We obtained for the ratio of the liquid side mass transfer coefficient to initial bubbles radius, kL/r0=0.12 s-1.

Transferência de massa gás-líquido em coluna de aeração; Mass transfer gas-liquid in column of aeration

SALLA, Marcio Ricardo; SCHULZ, Harry Edmar
Fonte: ABES Publicador: ABES
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
666.652%
Neste trabalho estuda-se a transferência de massa gás-líquido a partir de bolhas de ar para a água, geradas por um difusor de ar, em uma coluna de aeração, mudando a vazão de ar de 400 L/h a 2000 L/h, o nível de água de 0,50 m a 1,80 m, cujas taxas de aplicação superficial de ar variaram de 3,1 L/m².s a 15,4 L/m².s. Várias características hidrodinâmicas foram medidas, tal como a velocidade ascensional das bolhas de ar e seus diâmetros, fundamentais para verificar o coeficiente de transferência de massa que estão na literatura, usando um equipamento laser para velocimetria não-intrusiva. Após os estudos da transferência de massa, foi concluído que a vazão de ar entre 400 L/h e 800 L/h e o nível de água de 1,80 m apresentou a maior eficiência de transferência de massa, garantindo para estas medidas, dentro da coluna em estudo, maior quantidade de oxigênio dissolvido.; The present work is a study of the mass transfer gas-liquid from air bubbles into water, generated by a diffuser of air, in a column of aeration, changing the air flow from 400 L/h to 2000 L/h, the level of water from 0.50 m to 1.80 m, whose taxes of superficial application of air had varied of 3.1 L/m².s to 15.4 L/m².s. Several hydrodynamics characteristics were measured...

Estimation of Mass Transfer Velocity Based on Measured Turbulence Parameters

JANZEN, Johannes G.; HERLINA, H.; JIRKA, Gerhard H.; SCHULZ, Harry E.; GULLIVER, John S.
Fonte: JOHN WILEY & SONS INC Publicador: JOHN WILEY & SONS INC
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
667.8955%
The aim of this study is to quantify the mass transfer velocity using turbulence parameters from simultaneous measurements of oxygen concentration fields and velocity fields. The surface divergence model was considered in more detail, using data obtained for the lower range of beta (surface divergence). It is shown that the existing models that use the divergence concept furnish good predictions for the transfer velocity also for low values of beta, in the range of this study. Additionally, traditional conceptual models, such as the film model, the penetration-renewal model, and the large eddy model, were tested using the simultaneous information of concentration and velocity fields. It is shown that the film and the surface divergence models predicted the mass transfer velocity for all the range of the equipment Reynolds number used here. The velocity measurements showed viscosity effects close to the surface, which indicates that the surface was contaminated with some surfactant. Considering the results, this contamination can be considered slight for the mass transfer predictions. (C) 2009 American Institute of Chemical Engineers AIChE J, 56: 2005-2017; 2010; CAPES[2201/06-2]; CNPq; FAPESP; German Science Foundation (DFG)[Ji18/7-1]

Oxygen mass transfer in a high solids loading three-phase internal-loop airlift reactor

Freitas, Carla Maria Duarte de; Teixeira, J. A.
Fonte: Elsevier Science Publicador: Elsevier Science
Tipo: Artigo de Revista Científica
Publicado em //2001 ENG
Relevância na Pesquisa
666.652%
Determinations of volumetric mass transfer coefficient were conducted in a three-phase internal-loop airlift reactor with an enlarged degassing zone. The effect of parameters such as the airflow rate (riser superficial gas velocities between 0.01 and 0.5 m/s), solids loading (up to 30%, v/v), solids density (1023 and 1048 kg/m3) and the liquid-phase properties on kLa was studied. It was observed that the increase of the airflow rate and the introduction of ethanol enhanced the volumetric mass transfer coefficient in the system. On the contrary, the progressive introduction of solids and a small increase on solids density were responsible for the diminishing of the mass transfer rate. Correlations for the volumetric mass transfer coefficient with the riser superficial gas velocity and solids loading were determined for the two solids density and the two liquid-phases. A good agreement between experimental data and the calculated values was obtained.; Instituto de Biotecnologia e Química Fina. Fundação para a Ciência e a Tecnologia -PRAXIS/2/2.1/BIO/1061/95, GGPXXI/BD/2937/96. EC - INCO-COPERNICUS - no. ERB IC15-CT98-0904.

Temperature and solid properties effects on gas–liquid mass transfer

Ferreira, António; Ferreira, Cecília; Teixeira, J. A.; Rocha, F. A.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2010 ENG
Relevância na Pesquisa
667.5608%
The knowledge about the effect of solid phase properties, at different temperatures, on gas–liquid transfer and the respective physical mechanisms has been poorly studied. In the present work, the temperature and solid properties (size and density) effects on the gas–liquid mass transfer characteristics in a bubble column were experimentally evaluated. Gas–liquid–solid systems formed by air/water/polyvinyl chloride (PVC) beads and air/water/expandable polystyrene (EPS) beads were used. For each system, volumetric liquid side mass transfer coefficient, kLa, was determined under different temperatures (20–35 ◦C), superficial gas velocities (up to 7.2 mm/s), solids sizes (210, 549 and 591 m) and concentration (up to 5 vol.%). The results show that the temperature plays an important role on mass transfer phenomena as kLa increases as temperature is increased. However, temperature does not have, significantly, influence on the solids effect on kLa. In what concerns the effect of the solids on kLa, a negative effect of their presence is observed being this effect more pronounced for the largest particles (for PVC). In addition, for the same solid size, a decrease in kLa occurs when the solid loading increases (observed in both cases...

Effect of Tween 80 on bubble size and mass transfer in a bubble contactor

Belo, Isabel; García-Abuín, Alicia; Gómez-Díaz, Diego; Navaza, José M.; Vidal-Tato, Isabel
Fonte: Wiley Publicador: Wiley
Tipo: Artigo de Revista Científica
Publicado em //2011 ENG
Relevância na Pesquisa
666.652%
Gas absorption in aqueous solutions with Tween 80 and absorption processes based on hydrodynamics and mass transfer is determined. The impact of surfactant concentration on gas holdup and gas-liquid interfacial area is analyzed, observing an increase of these parameters with surfactant concentration. The influence of liquid-phase contamination on the absorption process is investigated on the basis of the liquid-film mass transfer coefficient, removing the effect caused by the presence of a surfactant and the gas flow rate on the interfacial area and, thereby, on the volumetric mass transfer coefficient. The opposite effect on the mass transfer coefficient can be observed which decreases in the presence of the surfactant.

Enhancement of oxygen mass transfer in pneumatical bioreactors using n-dodecane as oxygen-vector

Folescu, Elena; Ferreira, António; Rocha, Fernando; Teixeira, J. A.
Fonte: “Gheorghe Asachi” Technical University of Iasi; Institutul Politehnic din Iasi Publicador: “Gheorghe Asachi” Technical University of Iasi; Institutul Politehnic din Iasi
Tipo: Artigo de Revista Científica
Publicado em //2012 ENG
Relevância na Pesquisa
667.5608%
In biotechnology, oxygen mass transfer is a key parameter involved in the design and operation of bioreactors and it can be analyzed by means of the oxygen mass transfer coefficient (kLa). Due to the fact that oxygen has a very low solubility in an aqueous media (8–10 ppm at 20°C), actively growing cells can consume all the dissolved oxygen very fast, therefore, it has to be supplied continuously into the broths. In conventionally aerated bioreactors, low oxygen solubility combined with slow oxygen transfer rates often results in reduced growth and culture productivity. Due to their higher oxygen solubility, non-toxicity to microbes, antifoaming action, oxygen-vectors addition is one of the most effective methods to improve oxygen mass transfer rate in aerobic fermentations. The aim of this study was to investigate the use of n-dodecane as oxygen-vector in bubble column and air-lift bioreactors, under different working conditions (air superficial velocity, volumetric fraction of the organic phase, medium temperature). The results show that volumetric fraction of oxygen-vector (φ) has a great influence on kLa; in the presence of low volumetric fraction (φ=0.005 (v/v)), the oxygen mass transfer coefficient’s value in bubble column bioreactor was increased by almost 100% at 35°C and for φ=0.02 (v/v) by 5% at 25°C...

O2 mass transfer in an oscillatory flow reactor provided with smooth periodic constrictions : individual characterization of kL and a

Ferreira, António; Teixeira, J. A.; Rocha, F. A.
Fonte: Elsevier BV Publicador: Elsevier BV
Tipo: Artigo de Revista Científica
Publicado em //2015 ENG
Relevância na Pesquisa
668.27766%
In the present work the superficial gas velocities ( u G ) and the oscillatory conditions (frequency and amplitude) effects on the gas–liquid mass transfer process in a novel oscillatory flow reactor provided with smooth periodic constrictions (OFR-SPC) are experimentally evaluated. The liquid-side mass transfer coefficient, k L , and the specific interfacial area, a, are studied individually. The specific interfacial area is obtained using the new automatic image analysis technique developed by Ferreira et al. (2012). The experimental results of volumetric liquid side mass transfer coefficient ( k L a ), Sauter mean diameter ( d 32 ) and gas holdup ( ε G ), and the calculated values of a and k L , are correlated with the superficial gas velocity and the power density ( P / V ), in order to be used in scale-up processes and in comparisons with the literature. The results show that k L a increases with both superficial gas velocity and oscillatory conditions, the last ones having the highest impact on the mass transfer process. The increase in the oscillation motion (frequency and amplitude) results in bubble size reduction (from ∼7 mm, without oscillation, to ∼1 mm, with oscillation), in bubble average residence time increase and...

Estimation of the diffusivities and mass transfer coefficients for pears dried under different methods.

Guiné, Raquel; Barroca, Maria João; Lopes, Paulo; Silva, Vitor; Santos, Mónica; Ferreira, Dulcineia
Fonte: Instituto Politécnico de Viseu Publicador: Instituto Politécnico de Viseu
Tipo: Conferência ou Objeto de Conferência
Publicado em //2010 ENG
Relevância na Pesquisa
668.27195%
Traditionally, in Portugal pears of the variety S. Bartolomeu are dried through an open-air sun exposure. However, this method of drying has some disadvantages, among which not being able to fully guarantee the necessary quality and sanitary standards for commercialization. Hence, the development of alternative drying methods to replace the traditional drying is of great importance nowadays, and the knowledge of the transfer phenomena happening during drying helps to understand these processes. The present work aimed at determining the mass transfer properties of pears for air drying performed in three drying systems: solar stove with forced air convection (STFC), solar stove with natural air convection (STNC) and drying tunnel with hot air from a solar collector (DT). The methodology used to determine the mass transfer properties was a diffusion model, which accounted for shrinkage. The values of the diffusion and mass transfer coefficients for the drying in the three systems were estimated, and from them was possible to conclude that the values of D e in the STNC and DT systems are similar to each other, whereas the STFC system gives a lower value of diffusivity...

Hydrodynamics Characteristics and Gas-Liquid Mass Transfer in a Three Phase Fluidized Bed Reactor

Silva,Edson L.
Fonte: The Brazilian Society of Mechanical Sciences Publicador: The Brazilian Society of Mechanical Sciences
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2001 EN
Relevância na Pesquisa
669.5499%
This paper presents the experimental characterization of hydrodynamics and gas-liquid mass transfer in a three-phase fluidized bed containing polystyrene and nylon particles. The influence of gas and liquid velocities on phase holdups and volumetric gas-liquid mass transfer coefficient was investigated for flow conditions similar to those applied in biotechnological process. The phase holdups were obtained by the pressure profile technique. The volumetric gas-liquid mass transfer coefficient was obtained adjusting the experimental concentration profiles of dissolved oxygen in the liquid phase with the predictions of the axial dispersion model. According to experimental results the liquid holdup increases with the gas velocity, whereas the solid holdup decreases. The gas holdup increases significantly with the increase in gas velocity, and it shows for the three-phase fluidized bed comparable values or larger than those of bubble column. The volumetric gas-liquid mass transfer coefficient increases significantly with an increase in the air velocity for both bubble column and fluidized beds. In addition, in the operational condition of high liquid velocity, the presence of low-density particles in the bed increased the gas-liquid mass transfer...

Mass transfer coefficients in a hanson mixer-settler extraction column

Torab-Mostaedi,M.; Safdari,S. J.; Moosavian,M. A.; Maragheh,M. Ghannadi
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2008 EN
Relevância na Pesquisa
672.1153%
The volumetric overall mass transfer coefficients in a pilot plant Hanson mixer-settler extraction column of seven stages have been measured using toluene-acetone-water system. The effects of agitation speed and dispersed and continuous phases flow rates on volumetric overall mass transfer coefficients have been investigated. The results show that the volumetric overall mass transfer coefficient increases with increase in agitation speed and reaches a maximum. After having reached its maximum, it falls with further increase in agitation speed. It was found that the volumetric overall mass transfer coefficient increases with increase in dispersed phase flow rate, while it decreases with increase in continuous phase flow rate. By using interfacial area, the overall mass transfer coefficients for continuous and dispersed phases are determined from volumetric coefficients. An empirical correlation for prediction of the continuous phase overall mass transfer coefficient is proposed in terms of Sherwood and Reynolds numbers. Also the experimental data of the column investigated are compared with data for various extraction columns. Comparison between theoretical models and experimental results for the dispersed phase mass transfer coefficient shows that these models do not have enough accuracy for column design. Using effective diffusivity in the Gröber equation results in more accurate prediction of overall mass transfer coefficient. The prediction of overall mass transfer coefficients from the presented equations is in good agreement with experimental results.

Mass transfer coeficients in pulsed perforated-plate extraction columns

Torab-Mostaedi,M.; Safdari,J.; Ghaemi,A.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2010 EN
Relevância na Pesquisa
668.27766%
This study examined the mass transfer performance in a pulsed perforated-plate extraction column with diameter of 50 mm using two different liquid systems. Mass transfer coefficients have been interpreted in terms of the axial diffusion model. The effects of pulsation intensity and dispersed and continuous phase velocities on the mass transfer performance have been investigated. Three different operating regimes, namely mixer-settler, transition, and emulsion regimes, were observed when the input energy was changed. Effective diffusivity is substituted for molecular diffusivity in the Gröber equation for prediction of dispersed phase overall mass transfer coefficients. A single correlation is derived in terms of Reynolds number, Eötvös number and dispersed phase holdup for prediction of the enhancement factor in all operating regimes. The prediction of overall mass transfer coefficients from the presented model is in good agreement with experimental results.

Mass transfer performance in pulsed disc and doughnut extraction columns

Torab-Mostaedi,M; Ghaemi,A; Asadollahzadeh,M; Pejmanzad,P
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2011 EN
Relevância na Pesquisa
671.4129%
Mass transfer performance is presented for a 76 mm diameter pulsed disc and doughnut extraction column for the toluene-acetone-water system. The experiments were carried out for both mass transfer directions. The mass transfer data are interpreted in terms of the axial diffusion model, thus accounting for continuous phase axial dispersion. The effect of operating parameters on the overall volumetric mass transfer coefficients has been investigated. The results show that the column performance increases with an increase in pulsation intensity. At high pulsation intensity, however, the overall volumetric mass transfer coefficient decreases due to the production of very fine dispersed droplets. It was also found that the column performance decreases with both an increase in dispersed phase velocity and a decrease in continuous phase velocity. An empirical correlation for prediction of the continuous phase overall mass transfer coefficient is derived in terms of the overall Sherwood number, Reynolds number and dispersed phase holdup for each mass transfer direction. The prediction of continuous phase overall mass transfer coefficients from the presented correlations is in good agreement with experimental data.

Mass transfer of SO2 absorption with an instantaneous chemical reaction in a bubble column

Li,Xiaolei; Zhu,Chunying; Lu,Sumin; Ma,Youguang
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2013 EN
Relevância na Pesquisa
666.652%
Gas absorption accompanied by an instantaneous irreversible chemical reaction in bubble columns has been analyzed theoretically. A mass transfer model based on the Dankwerts surface-renewal model as well as the penetration theory for surface stretch proposed by Angelo et al. was developed, in which the effects of bulk motion and turbulence on mass transfer were taken into account. The analytical expressions for the time-average mass transfer coefficient and the enhancement factor have been obtained. The fast reactive absorption of SO2 from gas mixtures into aqueous NH4HCO3 solution was investigated experimentally in a bubble column reactor to validate the mass transfer model, and the results calculated by the present model agree well with the experimental results.

Analysis of mass transfer kinetics in the biosorption of synthetic dyes onto Spirulina platensis nanoparticles

Dotto, Guilherme Luiz; Pinto, Luiz Antonio de Almeida
Fonte: Universidade Federal do Rio Grande Publicador: Universidade Federal do Rio Grande
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
670.5727%
In this research, the mass transfer kinetics for the biosorption of synthetic dyes (acid blue 9 and FD&C red no. 40) by Spirulina platensis nanoparticles was analyzed under different experimental conditions. The external mass transfer model (EMTM) and the homogeneous solid diffusion model (HSDM) were employed to study the mass transfer kinetics and also to estimate the values of external mass transfer coefficient (kf) and intraparticle diffusion coefficient (Dint). The Biot number (Bi) was used to verify the importance of external mass transfer in relation to intraparticle diffusion. The values of external mass transfer coefficient (kf) ranged from 1.67 × 10−6 to 11.40 × 10−6 cm s−1 and the intraparticle diffusion coefficient (Dint) ranged from 0.70 ×10−14 to 4.30 ×10−14 cm2 s−1. The Biot numbers (0.53 ≤ Bi ≤ 10.33) showed that, for both dyes, the biosorption onto S. platensis nanoparticles was controlled simultaneously by external mass transfer and intraparticle diffusion.

Hydrodynamics and mass transfer coefficient in three-phase air-lift reactors containing activated sludge

Jin, B.; Yin, P.; Lant, P.
Fonte: Elsevier Science SA Publicador: Elsevier Science SA
Tipo: Artigo de Revista Científica
Publicado em //2006 EN
Relevância na Pesquisa
666.652%
This study was to investigate the impacts of operating conditions and liquid properties on the hydrodynamics and volumetric mass transfer coefficient in activated sludge air-lift reactors. Experiments were conducted in internal and external air-lift reactors. The activated sludge liquid displayed a non-Newtonian rheological behavior. With an increase in the superficial gas velocity, the liquid circulation velocity, gas holdup and mass transfer coefficient increased, and the gas residence time decreased. The liquid circulation velocity, gas holdup and the mass transfer coefficient decreased as the sludge loading increased. The flow regime in the activated sludge air-lift reactors had significant effect on the liquid circulation velocity and the gas holdup, but appeared to have little impact on the mass transfer coefficient. The experimental results in this study were best described by the empirical models, in which the reactor geometry, superficial gas velocity and/or power consumption unit, and solid and fluid properties were employed.; http://www.sciencedirect.com/science/journal/02552701; Bo Jin, Pinghe Yin and Paul Lant

DIRECT NUMERICAL SIMULATION OF FLOW AND MASS TRANSFER IN SPACER-FILLED CHANNELS

MAHDAVIFAR, ALIREZA
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
667.369%
Spacer-filled channels are employed in membrane modules in many industrial applications where feed-flow spacers (employed to separate membrane sheets and create flow channels) tend to enhance mass transport characteristics, possibly mitigating fouling and concentration polarization phenomena. In this work direct numerical simulation was performed for the flow in the spacer-filled channels to obtain a better understanding of fluid flow and mass transfer phenomena in these channels. A solute with a Schmidt number of 1 at Reynolds numbers of 300, 500 and 800 (based on the bulk velocity and spacer diameter) was considered. The effect of spacer location was also studied for three different configurations, spacer at the centre of the channel, at off-centre location, and attached to the wall. Instantaneous velocity fields and flow structures such as separation of boundary layer on the walls and on the cylinder, eddies on the walls, recirculation regions and vortex shedding were investigated. A Fourier analysis was carried out on the time series velocity data. Using this analysis the Strouhal number was calculated and the development of the flow towards a broader turbulent state at higher Reynolds number was captured. Other statistical characteristics such as time-averaged velocities and wall shear rates are obtained and discussed. The average pressure loss which represents the operation cost of membrane modules was calculated for the channels and found to be highest for spacer at the centre of the channel and lowest for spacer attached to the wall. Scalar transport equation is directly solved along with Navier-Stokes equation to get the concentration field. Local Sherwood number is obtained on the walls and the relationship between shear stress...

pH influence on oxygen mass transfer coefficient in a bubble column. Individual characterization of kL and a

Ferreira, António; Cardoso, P.; Teixeira, J. A.; Rocha, F. A.
Fonte: Pergamon Press Ltd. Publicador: Pergamon Press Ltd.
Tipo: Artigo de Revista Científica
Publicado em //2013 ENG
Relevância na Pesquisa
666.652%
Experiments were performed in a laboratory scale bubble column (10 L), to investigate the pH influence on oxygen mass transfer coefficient, in order to achieve a better control of biological processes. The liquid-side mass transfer coefficient, kL, and the specific interfacial area, a, were studied individually. The specific interfacial area was obtained using the new automatic image analysis technique developed by Ferreira et al. (2012). The pH was changed by the addition to the system of the most common acids and base used in biological process: hydrochloric acid (HCl), phosphoric acid (H3PO4) and potassium hydroxide (KOH). The results show that aqueous systems containing HCl, H3PO4 or KOH present lower volumetric liquid side mass transfer coefficient, kLa, in relation to pure systems (distilled water), this decrease being not linear. It was found that the specific interfacial area presents higher values in KOH and HCl solutions in comparison with distilled water. However, an opposite behavior was observed in the liquid-side mass transfer coefficient values. The kL behavior on the impure systems was explained based on bubble surface contamination. Higbie's and Fröessling's equations were adapted in the present work in order to be used in bubble dispersion systems.

Viscoelasticity and mass transfer in phenol–CTAB aqueous systems

Varade, Dharmesh; Rodríguez-Abreu, Carlos; Delgado, José Gregorio; Aramaki, Kenji
Fonte: Springer Publicador: Springer
Tipo: Artículo Formato: 19968 bytes; application/msword
ENG
Relevância na Pesquisa
666.652%
7 pages, 8 figures.-- Printed version published Dec 2007.; The rheological and mass transport properties of phenol in micellar solutions of hexadecyltrimethylammonium bromide (CTAB) were studied by rheometry and spectrophotometry. The presence of phenol located between headgroups of the CTAB diminishes the repulsive forces between the cationic groups and induces a sharp increase in viscosity that is attributed to the one-dimensional micellar growth favoring the formation of worm-like micelles. It is found that the mass transfer of phenol between two immiscible phases is significantly retarded by the presence of CTAB. The transfer is particularly slow when the diffusion takes place from a surfactant solution phase to an organic phase. This behavior is attributed to the phenol– surfactant interaction that leads to micellar growth and viscoelastic behavior. However, at elevated temperature, viscosity decreases and mass transfer increases. This particular rheological behavior offers the possibility of regulating the mass transfer, which might be interesting for applications.; DV thanks Japan Society for Promotion of Science (JSPS) for financial support. This work was supported by The Ministry of Education, Culture, Sports, Science...

Effect of Gas Sparging on the Rate of Mass Transfer at Horizontal Cylinders

Taha,A.A.; Ahmed,A.M.; Bayoumy,A.A.
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2003 EN
Relevância na Pesquisa
668.27766%
The rate of mass transfer was studied at (i) a single horizontal cylinder cathode and (ii) a vertical array of closely spaced horizontal cylinders and an array of separated cylinders. The mass transfer coefficients were obtained by measuring the limiting current of the cathodic reduction of alkaline potassium ferricyanide. Variables studied were: cylinder diameter, physical properties of the solution, and nitrogen flow rate. The mass transfer coefficient was found to increase with increasing nitrogen superficial velocity. Decreasing the diameter was found to increase the mass transfer coefficient. The mass transfer data were correlated by the following equations: For single horizontal cylinder cathode: J = 2.138 (Re. Fr)-0.24 For an array of closely spaced cylinders: J = 50.118 (Re.Fr)-0.32 For an array of separated cylinders: J = 100 (Re.Fr)-0.28 Possible practical application of gas sparged array of horizontal cylinders in building electrochemical reactors are discussed.