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Showing papers on "Mass transfer coefficient published in 2016"


Journal ArticleDOI
TL;DR: In this paper, the flow regimes and mass transfer rates in five complex micro-reactors with different mixing mechanisms were investigated using the two-phase alkaline hydrolysis of 4-nitrophenyl acetate.

92 citations


Journal ArticleDOI
TL;DR: In this article, an analysis is performed to study the bioconvection flow with heat and mass transfer of nanofluid containing gyrotactic microorganisms along a vertical wavy cone.

74 citations


Journal ArticleDOI
TL;DR: In this paper, the liquid-side controlled mass transfer process in a rotating packed bed (RPB) equipped with a surface-modified nickel foam packing (SNP), which is a hydrophobic structured packing, was examined.

71 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of employing sonication on the diffusion of sodium salt (NaCl) and a salt replacer (SR) into pork meat was investigated and the mass transfer equation was solved using the Runge-Kutta method.
Abstract: Summary In an attempt to reduce the high intake of dietary salt, the processed meat industry is continuously looking for alternative solutions for salt replacement. The objective of this study was to investigate the effect of employing sonication on the diffusion of sodium salt (NaCl) and a salt replacer (SR) into pork meat. Ultrasound-assisted brining experiments were carried out using 5% NaCl or SR at power levels of 9.0 and 54.9 W cm−2 for 120 min. Samples were assessed for cooking loss, water mobility, deformation, while thermal behaviour was analysed using differential scanning calorimetry (DSC). Experimental data obtained were used to estimate the mass transfer coefficient of the brining process. The mass transfer equation was solved using the Runge–Kutta method. Results showed that the ultrasonic treatment had a low influence on the mass transfer of salt into pork samples. Only at high ultrasonic power was the mass transfer coefficient higher than the static brining. This study has improved our understanding of the effect of sonication on diffusion of NaCl and SR in pork meat and will enable a more systemic approach to future healthy meat product development.

67 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present experimental results for the heat transfer coefficient during flow boiling of refrigerants R134a, R245fa and R600a inside small diameter tubes plus a new heat transfer predictive method.

66 citations


Journal ArticleDOI
TL;DR: In this paper, the authors examined the convective heat transfer of nanofluid past a wedge subject to first-order chemical reaction, heat generation/absorption and suction effects.
Abstract: The aim of the present study is to examine the convective heat transfer of nanofluid past a wedge subject to first-order chemical reaction, heat generation/absorption and suction effects. The influence of wedge angle parameter, thermophoresis, Dufour and Soret type diffusivity are included. The local similarity transformation is applied to convert the governing nonlinear partial differential equations into ordinary differential equations. Shooting method integrated with fourth-order Runge-Kutta method is used to solve the ordinary differential equations. The skin friction, heat and mass transfer rates as well as the effects of various parameters on velocity, temperature and solutal concentration profiles are analyzed. The results indicate that when the chemical reaction parameter increases, the heat transfer coefficient increases while the mass transfer coefficient decreases. The effect of chemical reaction parameter is very important in solutal concentration field compared to velocity and temperature profiles since it decreases the solutal concentration of the nanoparticle.

64 citations


Journal ArticleDOI
TL;DR: In this article, the authors presented a rate-based model of an absorber packed column for simultaneous absorptions of acid gases into methyldiethanolamine (MDEA) aqueous solution.

63 citations


Journal ArticleDOI
TL;DR: In this article, a new type of solar air collector and air to air heat recovery unit were added to the infrared dryer to reduce specific energy consumption, and three-dimensional (3-D) computational fluid dynamic (CFD) simulation was used to investigate drying kinetics of melon slices.

62 citations


Journal ArticleDOI
TL;DR: Overall, this work showed that it was possible to extract accurate mass transfer and dispersion information from experimental breakthrough curves using a 1-D axial dispersed plug flow model when they were measured both inside and outside the bed.
Abstract: This work examined in detail the a priori prediction of the axial dispersion coefficient from available correlations versus obtaining both it and mass transfer information from experimental breakthrough data and the consequences that may arise when doing so based on using a 1-D axially dispersed plug flow model and its associated Danckwerts outlet boundary condition. These consequences mainly included determining the potential for erroneous extraction of the axial dispersion coefficient and/or the LDF mass transfer coefficient from experimental data, especially when nonplug flow conditions prevailed in the bed. Two adsorbent/adsorbate cases were considered, i.e., CO2 and H2O vapor in zeolite 5A, because they both experimentally exhibited significant nonplug flow behavior, and the H2O-zeolite 5A system exhibited unusual concentration front sharpening that destroyed the expected constant pattern behavior (CPB) when modeled with the 1-D axially dispersed plug flow model. Overall, this work showed that it was...

60 citations


Journal ArticleDOI
28 Dec 2016
TL;DR: In this work, the concentration process of three different tea extracts using the osmotic evaporation (OE) process, was studied and the effect of the OE process on the content of phenolic compounds and antioxidant activity was evaluated.
Abstract: In this work, the concentration process of three different tea extracts (medicinal Rosil No. 6, Black, and Forest Fruit teas) using the osmotic evaporation (OE) process, was studied. The effect of the OE process on the content of phenolic compounds and antioxidant activity was evaluated. The concentration process was carried out in a hollow-fibre membrane contactor with an effective surface area of 0.54 m2. The tea extract was circulated through the shell side of the contactor, while a concentrated osmotic solution (CaCl2 5 M) was circulated inside the fibres. The flux, the driving force, and the mass transfer coefficient were evaluated. A decrease of the water flux over time was observed and was attributed only to the decrease of the driving force, caused by the dilution of the osmotic solution. Using a surface area/feed volume ratio of 774 m2·m−3, it is possible to reach a tea concentration of 40% (w/w) in 5 h, with a constant water flux and without losing the phenolic content and antioxidant potential in most teas.

57 citations


Journal ArticleDOI
Bin Xu1, Hongxia Gao1, Xiao Luo1, Huiying Liao1, Zhiwu Liang1 
TL;DR: In this article, a bench-scale absorption column packed with high efficiency Sulzer DX-type packing was used to determine the volumetric overall mass transfer coefficient (K G a v ) for CO 2 absorption into an aqueous solution of DEEA.

Journal ArticleDOI
TL;DR: In this paper, the volumetric mass transfer coefficient, kmAekmAe has been calculated for diverse electrode structures from limiting current measurements for Ce(IV) ion reduction in a laboratory, rectangular channel flow cell.

Journal ArticleDOI
TL;DR: In this article, a variety of microporous hydrophobic flat sheet membranes of polyvinylidene fluoride (PVDF) and expanded polytetrafluoroethylene (ePTFE) were employed over a range of hot brine temperatures, 65-85°C.

Journal ArticleDOI
TL;DR: In this paper, an attempt to implement the model equations for continuous systems has been made, where an adequate experimental investigation has been obtained by carrying out adsorption experiments both on batch and in continuous devices by using a model system that is represented by aqueous methylene blue over silica.

Journal ArticleDOI
TL;DR: In this paper, mass transfer studies were done to evaluate the rate-limiting step in the adsorption of phenol from aqueous solution onto Lantana camara.
Abstract: Adsorption is one of the important treatment methods for the removal of pollutants from wastewater. The determination of rate controlling step in the process is important in the design of the process. Therefore, in the present work, mass transfer studies were done to evaluate the rate-limiting step in the adsorption of phenol from aqueous solution onto Lantana camara. Different mass transfer models were used to find the rate-limiting step and also to find the values of external mass transfer coefficient and diffusion coefficient. The Biot number was found to investigate the importance of external mass transfer to intraparticle diffusion. From the various models studied and the Biot numbers obtained, it was found that the adsorption on Lantana camara was controlled by film diffusion. The sensitivity analysis was performed to study the significance of the model parameters on the adsorption process.

Journal ArticleDOI
TL;DR: In this article, the authors used a lumped parameter model to quantify the mass transfer coefficient in batch mode and a distributed model to describe the extraction in a slug (stratified) flow in a micro-channel.
Abstract: Liquid-liquid extraction is an important mass transfer operation in the chemical, food processing and pharmaceutical industries. Our work focuses on experimentally quantifying mass transfer performance in a well stirred batch vessel and in stratified flow and slug flow in micro-channels. Extraction of propionic acid from toluene to water is chosen as a test system. The distribution of propionic acid in toluene and water at equilibrium was found to be non-linear. The batch experiments were carried out both with a flat interface and as a well-mixed dispersed system. The continuous experiments were carried out in micro-channels with a square cross-section. A lumped parameter model was used to quantify the mass transfer coefficient in batch mode. A lumped (distributed) model was used to describe the extraction in a slug (stratified) flow in a micro-channel. The overall extraction performance is characterized as a function of residence time of the phases and the hydrodynamics. It was found that the micro-channel gives a superior extraction performance in the slug flow regime as compared to the well mixed batch system although both have comparable sizes of the dispersed phase. This is attributed to the strong internal circulations induced by shear in the slug flow regime.

Book ChapterDOI
01 Jan 2016
TL;DR: This chapter considers how to formulate and describe elementary diffusion and mass transfer problems in fluid systems and develops a differential equation, and a solution containing arbitrary constants evolves.
Abstract: In Chapters 2 and 7, we demonstrated the development of differential equations pertinent to momentum and energy transport in simple fluid systems. In this chapter, we consider how to formulate and describe elementary diffusion and mass transfer problems in fluid systems. We use practically the same procedure in this situation as we did previously; we develop a differential equation, and a solution containing arbitrary constants evolves. These constants are evaluated by applying boundary conditions that specify the concentration or the mass flux at the bounding surfaces. Again, we demonstrate the principles involved by considering specific examples, but first let us reconsider the general situation.

Journal ArticleDOI
TL;DR: The semi-continuous cultivation system had shown the possibility to partially harvest microalgae biomass during the exponential growth phase and thus, shorten the overall cultivation time in the subsequent cycles (elimination of lag phase) which resulted in higher biomass production.
Abstract: A 56 L compressed-air aerated bubble column photobioreactor (BC-PBR) was used to cultivate Chlorella vulgaris under indoor conditions via semi-continuous cultivation method. The effects of hydrodynamics and gas–liquid mass transfer limitations towards the biomass production of C. vulgaris at different compressed-air aeration rates were studied. The optimum biomass production of microalgae was achieved at compressed-air aeration rate of 0.16 VVM, with superficial velocity, U G of 0.185 m s − 1 . The experimental volumetric gas–liquid mass transfer coefficient, k L a L (CO 2 ), was 4.5 × 10 − 3 s − 1 under the optimum growth condition. Besides that, the physical properties such as density, viscosity and surface tension remained constant throughout the semi-continuous cultivation mode. Low biomass production was observed at the highest aeration rate (0.19 VVM), which indicated that shear sensitivity has significant effect on microalgae growth in BC-PBR. Apart from that, the effect of shear stress on the growth of C. vulgaris was also reported, especially on the reproduction of microalgae cells. The semi-continuous cultivation system had shown the possibility to partially harvest microalgae biomass during the exponential growth phase and thus, shorten the overall cultivation time in the subsequent cycles (elimination of lag phase) which resulted in higher biomass production.

Journal ArticleDOI
TL;DR: In this paper, a simulation of an industrial spiral wound reverse osmosis (RO) feed channel under typical plant operating conditions is investigated using fully-coupled three-dimensional computational fluid dynamic (CFD) simulations with a detailed spacer geometry.

Journal ArticleDOI
TL;DR: The utility of CFD as a tool to predict size distribution of bubbles as a function of process parameters and an efficient approach for obtaining optimized mixing conditions in the reactor is demonstrated.
Abstract: Mixing in bioreactors is known to be crucial for achieving efficient mass and heat transfer, both of which thereby impact not only growth of cells but also product quality. In a typical bioreactor, the rate of transport of oxygen from air is the limiting factor. While higher impeller speeds can enhance mixing, they can also cause severe cell damage. Hence, it is crucial to understand the hydrodynamics in a bioreactor to achieve optimal performance. This article presents a novel approach involving use of computational fluid dynamics (CFD) to model the hydrodynamics of an aerated stirred bioreactor for production of a monoclonal antibody therapeutic via mammalian cell culture. This is achieved by estimating the volume averaged mass transfer coefficient (kL a) under varying conditions of the process parameters. The process parameters that have been examined include the impeller rotational speed and the flow rate of the incoming gas through the sparger inlet. To undermine the two-phase flow and turbulence, an Eulerian-Eulerian multiphase model and k-e turbulence model have been used, respectively. These have further been coupled with population balance model to incorporate the various interphase interactions that lead to coalescence and breakage of bubbles. We have successfully demonstrated the utility of CFD as a tool to predict size distribution of bubbles as a function of process parameters and an efficient approach for obtaining optimized mixing conditions in the reactor. The proposed approach is significantly time and resource efficient when compared to the hit and trial, all experimental approach that is presently used. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:613-628, 2016.

Journal ArticleDOI
TL;DR: In this article, the potentialities of using a membrane contactor based on a dense skin Poly (Phenylene Oxide) (PPO) hollow fiber module for CO 2 absorption from biogas by pressurized water through simulations and experiments were evaluated.

Journal ArticleDOI
TL;DR: In this article, the overall adsorption rate of Reactive Black 5 dye (RB5) on chitosan based materials was elucidated using diffusional models and fundamental aspects, such as, geometry of the adsorbents and swelling effects were considered.
Abstract: The overall adsorption rate of Reactive Black 5 dye (RB5) on chitosan based materials was elucidated using diffusional models. Fundamental aspects, such as, geometry of the adsorbents and swelling effects were considered. Chitosan based materials (powder and film) were prepared from shrimp wastes and characterized regarding to the fundamental features for adsorption. Experimental decay curves were obtained under different conditions of stirring rate and initial dye concentration. The data were modeled according to the external mass transfer and diffusional models. The kL (external mass transfer coefficient), Dep (effective pore diffusion coefficient) and Ds (surface diffusion coefficient) values were estimated. For both adsorbents, it was found that the surface diffusion was the intraparticle diffusion mechanism governing the adsorption rate of RB5, since its contribution was higher than 92 % regardless the position and time. The Ds values ranged from 2.85 × 10−11 to 5.78 × 10−11 for chitosan powder and from 4.15 × 10−11 to 12.12 × 10−11 cm2 s−1 for chitosan films. The RB5 adsorption was faster when chitosan powder was used, mainly at higher stirring rates and initial dye concentrations. The swelling effect was most pronounced for the chitosan films, where, provided an increase of about 65 times in the Ds value.

Journal ArticleDOI
TL;DR: In this article, a review of micro-packed beds with liquid-solid mass transfer coefficients (kLS) is presented, and the correspondence of kLS values with macro-scale correlations is discussed.
Abstract: Studies on micro-packed beds were reviewed pointing out major contributions with their key findings. Negligible mass transfer resistance and temperature gradients in micro-packed beds enables access to intrinsic kinetic data. Small scales also provide safety for extreme conditions and production of hazardous materials. Hydrodynamic studies in micro-packed beds suggest that stronger capillary forces give rise to hydrodynamic differences between macro- and micro-packed beds. Also, studies reach consensus that deviations from plug flow are minimal. Mass transfer studies in micro-packed beds have been mostly coupled with kinetic studies and results are typically reported as overall mass transfer coefficients two orders of magnitude higher than those in macro-scale. Among the reviewed studies, mass transfer has been identified as the scarcest in coverage and therefore a complementary work was performed on liquid-solid mass transfer coefficients (kLS) in micro-packed beds. Experiments were performed within the diffusion-limited regime and the correspondence of kLS values with macro-scale correlations was discussed. It was found that in single-phase liquid flow, micro-scale kLS is closely predicted by macro-scale correlations. Comparison between macro- and micro-scale showed that volumetric mass transfer coefficients are higher in the latter due to higher solid-liquid interactions in confined volumes and high surface-to-volume ratios.

Journal ArticleDOI
TL;DR: In this paper, mass transfer rates were measured in a serpentine micro-reactor with a hydraulic diameter of 0.7mm using the two-phase alkaline hydrolysis of 4-nitrophenyl acetate.

Journal ArticleDOI
TL;DR: In this article, a preliminary study of axial concentration profiles in a bubble column is given, based on the available experimental data found in the literature, and experimentally determined values are used.

Journal ArticleDOI
TL;DR: In this article, the application of nanofiltration membranes to remove multiple contaminants such as fluoride, arsenic, sulfate and nitrate, was investigated, and the central composite design was applied to evaluate the influence of transmembrane pressure, cross-flow velocity and initial concentration of each solute on rejection and flux.
Abstract: The application of nanofiltration membranes to remove multiple contaminants such as fluoride, arsenic, sulfate and nitrate, was investigated. The central composite design was applied to evaluate the influence of transmembrane pressure, cross-flow velocity and initial concentration of each solute on rejection and flux. The predictive quadratic models were developed for each response and the analysis of variance was applied to test the response surface models. The average rejection for the NF90 membrane was observed to be 95, 98, 87, and 76% for SO4, As, F, and NO3, respectively, whereas the NF270 membrane rejected the said ions around 90, 94, 57, and 60%, respectively. The NF270 membrane delivered 1.5 times better flux than the NF90 membrane. The experimental results were successfully predicted by the multiple solute models. Membrane resistance, permeability coefficient and mass transfer coefficient were also established for each membrane. The gel layer thickness was determined to better understand the hydrodynamics and it validated the assumption of negligible fouling.

Journal ArticleDOI
22 Mar 2016-Langmuir
TL;DR: Different control mechanisms for different surfactants are analyzed based on the range of t/t(m), and a criterion time ratio using a simplified characteristic mass transfer time, t(m)*, is finally proposed for predicting the appearance of dynamic interfacial tension.
Abstract: Varied interfacial tension caused by the unsaturated adsorption of surfactants on dripping droplet surfaces is experimentally studied. The mass transfer and adsorption of surfactants, as well as the generation of fresh interfaces, are considered the main factors dominating the surfactant adsorption ratio on droplet surfaces. The diffusion and convective mass transfer of the surfactants are first distinguished by comparing the adsorption depth and the mass flux boundary layer thickness. A characterized mass transfer time is then calculated by introducing an effective diffusion coefficient. A time ratio is furthermore defined by dividing the droplet generation time by the characteristic mass transfer time, t/tm, in order to compare the rates of surfactant mass transfer and droplet generation. Different control mechanisms for different surfactants are analyzed based on the range of t/tm, and a criterion time ratio using a simplified characteristic mass transfer time, tm*, is finally proposed for predicting t...

Journal ArticleDOI
TL;DR: In this paper, the effect of hydrophilic silica nanoparticles on mass transfer in liquid-liquid extraction process was experimentally investigated using the ternary chemical system toluene-acetic acid-water.

Journal ArticleDOI
TL;DR: In this article, the performance of bubble column humidifier and dehumidifier is investigated experimentally under sub-atmospheric pressure for the humidifier, and elevated pressures for the deHumidifier.

Journal ArticleDOI
21 Mar 2016
TL;DR: In this article, the characteristics of several different types of diffusion layers were systematically examined to improve the performance of activated carbon air cathodes used in microbial fuel cells (MFCs).
Abstract: The characteristics of several different types of diffusion layers were systematically examined to improve the performance of activated carbon air cathodes used in microbial fuel cells (MFCs). A diffusion layer of carbon black and polytetrafluoroethylene (CB + PTFE) that was pressed onto a stainless steel mesh current collector achieved the highest cathode performance. This cathode also had a high oxygen mass transfer coefficient and high water pressure tolerance (>2 m), and it had the highest current densities in abiotic chronoamperometry tests compared to cathodes with other diffusion layers. In MFC tests, this cathode also produced maximum power densities (1610 ± 90 mW m−2) that were greater than those of cathodes with other diffusion layers, by 19% compared to Gore-Tex (1350 ± 20 mW m−2), 22% for a cloth wipe with PDMS (1320 ± 70 mW m−2), 45% with plain PTFE (1110 ± 20 mW m−2), and 19% higher than those of cathodes made with a Pt catalyst and a PTFE diffusion layer (1350 ± 50 mW m−2). The highly porous diffusion layer structure of the CB + PTFE had a relatively high oxygen mass transfer coefficient (1.07 × 10−3 cm s−1) which enhanced oxygen transport to the catalyst. The addition of CB enhanced cathode performance by increasing the conductivity of the diffusion layer. Oxygen mass transfer coefficient, water pressure tolerance, and the addition of conductive particles were therefore critical features for achieving higher performance AC air cathodes.