scholarly journals Probing Differences in Mass-Transfer Coefficients in Beaker and Stirrer Digestion Systems and the USP Dissolution Apparatus 2 Using Benzoic Acid Tablets

Processes ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 2168
Author(s):  
Timothy A. G. Langrish ◽  
Chao Zhong ◽  
Lizhe Sun
Keyword(s):  
Mass Transfer ◽  
Benzoic Acid ◽  
Reynolds Numbers ◽  
Operating Conditions ◽  
External Mass Transfer ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Rate Limiting Step ◽  
Dissolution Apparatus ◽  
Rate Limiting

Measurements of external mass-transfer coefficients for dissolution have been made with benzoic acid tablets with a diameter of 13 mm and approximately 3 mm thick, using two different dissolution systems. One system has been a beaker with a platform for the tablet and either 80 mL or 120 mL of water, with three different types of stirrers, and the other has been a USP dissolution apparatus 2 (paddle) with either 200 mL or 900 mL water. Various stirring speeds have also been used in the different pieces of equipment. The same mass-transfer coefficient may potentially be obtained from the same tablet by adjusting the operating conditions in the two different devices. The ranges of the external mass-transfer coefficients measured in both devices overlapped significantly, with the range being 0.193–4.48 × 10−5 m s−1 in the beaker and stirrer system and 0.222–3.45 × 10−5 m s−1 in the USP dissolution apparatus 2. Dimensional analysis of the results, using Sherwood and Reynolds numbers, shows that the Ranz–Marshall correlation provides a lower bound for estimates of the Sherwood numbers measured experimentally. Calculations of time constants for mass transfer suggest that mass transfer may be a rate-limiting step for dissolution and food digestion under some circumstances. The range of mass-transfer coefficients measured here is representative of other measurements from the literature, and the use of the Ranz–Marshall correlation supports the suggestion that this range of values should be generally expected in most situations.

scholarly journals The Need for Accurate Osmotic Pressure and Mass Transfer Resistances in Modeling Osmotically Driven Membrane Processes

Membranes ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 128
Author(s):  
Endre Nagy ◽  
Imre Hegedüs ◽  
Danyal Rehman ◽  
Quantum J. Wei ◽  
Yvana D. Ahdab ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Osmotic Pressure ◽  
Water Flux ◽  
Operating Conditions ◽  
Structural Parameter ◽  
External Mass Transfer ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
The Real ◽  
Parameter Values

The widely used van ’t Hoff linear relation for predicting the osmotic pressure of NaCl solutions may result in errors in the evaluation of key system parameters, which depend on osmotic pressure, in pressure-retarded osmosis and forward osmosis. In this paper, the linear van ’t Hoff approach is compared to the solutions using OLI Stream Analyzer, which gives the real osmotic pressure values. Various dilutions of NaCl solutions, including the lower solute concentrations typical of river water, are considered. Our results indicate that the disparity in the predicted osmotic pressure of the two considered methods can reach 30%, depending on the solute concentration, while that in the predicted power density can exceed over 50%. New experimental results are obtained for NanoH2O and Porifera membranes, and theoretical equations are also developed. Results show that discrepancies arise when using the van ’t Hoff equation, compared to the OLI method. At higher NaCl concentrations (C > 1.5 M), the deviation between the linear approach and the real values increases gradually, likely indicative of a larger error in van ’t Hoff predictions. The difference in structural parameter values predicted by the two evaluation methods is also significant; it can exceed the typical 50–70% range, depending on the operating conditions. We find that the external mass transfer coefficients should be considered in the evaluation of the structural parameter in order to avoid overestimating its value. Consequently, measured water flux and predicted structural parameter values from our own and literature measurements are recalculated with the OLI software to account for external mass transfer coefficients.

Hydrodynamic and Mass Transfer Parameters in Agitated Reactors Part II: Gas-Holdup, Sauter Mean Bubble Diameters, Volumetric Mass Transfer Coefficients, Gas-Liquid Interfacial Areas, and Liquid-Side Mass Transfer Coefficients

2005 ◽  
Vol 3 (1) ◽  
Author(s):  
Romain Lemoine ◽  
Badie I Morsi
Keyword(s):  
Mass Transfer ◽  
Benzoic Acid ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Gas Holdup ◽  
Operating Conditions ◽  
Organic Liquids ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Transfer Parameters

The equilibrium gas solubility (C*), gas-holdup (eG), Sauter mean bubble diameter (dS), volumetric mass transfer coefficient (kLa), gas-liquid interfacial area (a) and mass transfer coefficient (kL) of N2, O2 and air were measured in an agitated reactor operating in surface-aeration (SAR), gas-inducing (GIR) or gas-sparging (GSR) modes in pure toluene and three mixtures of organic liquids (toluene-benzoic acid-benzaldehyde) aimed at simulating the continuous liquid phase toluene oxidation (LPTO) under wide ranges of temperatures (300-453K), pressures (1-15 bar), mixing speeds (13.3-20.0 Hz), superficial gas velocities (0.000-0.004 m/s in the GSR) and liquid heights (0.171-0.268m in the SAR and GIR).C* values of the gases in the organic liquids were calculated using a modified Peng-Robinson Equation-of-State and kLa data were determined using the Transient Physical Absorption technique. The bubble size distributions as well as dS were obtained from the Photographic method, and eG values were measured through the Dispersion Height technique using the reactor’s Jerguson windows. From eG, dS and kLa experimental values, a and kL were calculated under various operating conditions. The Central Composite Statistical Design and analysis technique was used to study the effect of operating conditions on the hydrodynamic and mass transfer parameters.At constant temperature, the equilibrium solubilities (C*) of the three gases in all liquids used appeared to increase linearly with pressure and obey Henry’s Law, however, the values exhibited minima with increasing temperature. The C* values were found to increase with increasing gas molecular weight, and decrease with the addition of benzaldehyde and benzoic acid to pure toluene. A dimensionless form of Arrhenius-type equation, in which the activation energy was dependent of temperature, was developed to predict Henry’s law constant for the three gases in toluene and mixtures with a regression coefficient > 99%.In the SAR, increasing N, T or decreasing H increased eG, a, kL and kLa, and decreased dS, whereas increasing P, decreased eG, a, kL and kLa. In the GIR, increasing N or decreasing H increased eG, a, kL, kLa and dS. Also, increasing T increased and then decreased eG and a; increased kL and kLa; and decreased dS. In addition, increasing P did not affect these hydrodynamic and mass transfer parameters under the operating conditions used. In the GSR, increasing N, T and UG increased eG, a, kL and kLa. Also, increasing N and T, or decreasing UG decreased dS.The addition of benzaldehyde and benzoic acid to pure toluene was found to significantly affect the hydrodynamic parameters (dS and eG), in the GSR and GIR, especially at low temperature due to formation of froth, which led to the enhancement of kLa. The hydrodynamic and mass transfer parameters obtained indicated that the behavior of the SAR was mainly dependent on kL, whereas those of the GSR and GIR were strongly affected not only by kL, but also by a. Statistical correlations were also developed to predict the hydrodynamic and mass transfer parameters obtained in this study with confidence levels > 95%. These correlations could be used to model, design and scale-up the LPTO process in agitated reactors.

Liquid-liquid mass transfer studies in various stirred vessel designs

2015 ◽  
Vol 31 (4) ◽  
Author(s):  
Reza Afshar Ghotli ◽  
Abdul Raman Abdul Aziz ◽  
Shaliza Ibrahim
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Interfacial Area ◽  
Operating Conditions ◽  
Experimental Results ◽  
Dispersed Phase ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Wide Range

AbstractA general review on correlations to evaluate mass transfer coefficients in liquid-liquid was conducted in this work. The mass transfer models can be classified into continuous and dispersed phase coefficients. The effects of drop size and interfacial area on mass transfer coefficient were investigated briefly. Published experimental results for both continuous and dispersed phase mass transfer coefficients through different hydrodynamic conditions were considered and the results were compared. The suitability and drawbacks of these correlations depend on the operating conditions and hydrodynamics. Although the results of these models are reasonably acceptable, they could not properly predict the experimental results over a wide range of designs and operating conditions. Therefore, proper understanding of various factors affecting mass transfer coefficient needs to be further extended.

scholarly journals The flow and mass transfer characteristics of concentric gas-liquid flow in an advanced static mixer

2020 ◽  
pp. 24-24
Author(s):  
Huibo Meng ◽  
Zhonggen Li ◽  
Yanfang Yu ◽  
Mengqi Han ◽  
Shuning Song ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Liquid Flow ◽  
Operating Conditions ◽  
Static Mixer ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Local Mass ◽  
Transfer Characteristics ◽  
Local Mass Transfer ◽  
Gas Liquid Flow

The fluid dynamic and mass transfer characteristics of concentric upward gas-liquid flow were studied in the industrial static mixer with four equally spaced helical inserts (FKSM). The numerical simulations of gas volume fraction in Kenics mixer had a good agreement with the numerical and experimental results provided by Rabha et al. The characteristics of radial gas void fraction and local mass transfer coefficients in the FKSM were evaluated under different operating conditions. The velocity profiles of concentric air phase accelerated by the bubble forces firstly became sharp and narrow until z/l=-3.27 and then slowly decreased and stabilized at z/l=-1.5 before entering the first mixing element. Some extra unimodal profile of radial gas holdup gradually generated near the rectangle cross sections of mixing elements. The ?G gradually enlarged from r/R=0.2 to r/R=0.55 and then weakened from r/R=0.65 to r/R=0.874. The air void fractions in the bulk flow region decreased with the increasing initial uniform bubble diameter. The inlet effect of first leading edge enhanced the air phase dispersion and local mass transfer coefficients sharply increased from 2.04 to 3.69 times of that in the inlet. The local mass transfer coefficients in each mixing group had unimodal profiles.

scholarly journals Influence of Hydraulic Pressure on Performance Deterioration of Direct Contact Membrane Distillation (DCMD) Process

Membranes ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 37 ◽  
Author(s):  
Seung-Min Park ◽  
Sangho Lee
Keyword(s):  
Mass Transfer ◽  
Direct Contact ◽  
Membrane Distillation ◽  
Operating Conditions ◽  
Hydraulic Pressure ◽  
Transfer Coefficients ◽  
Hydrophobic Membrane ◽  
Mass Transfer Coefficients ◽  
Efficient Operation ◽  
Direct Contact Membrane Distillation

Direct contact membrane distillation (DCMD) is a membrane distillation (MD) configuration where feed and distillate directly contact with a hydrophobic membrane. Depending on its operating conditions, the hydraulic pressures of the feed and distillate may be different, leading to adverse effects on the performance of the DCMD process. Nevertheless, little information is available on how hydraulic pressure affects the efficiency of DCMD. Accordingly, this paper investigates the effect of external hydraulic pressure on the process efficiency of DCMD. Gas permeabilities of MD membranes were measured to analyze the effect of membrane compaction by external pressure. Mass transfer coefficients were calculated using experimental data to quantitatively explain the pressure effect. Experiments were also carried out using a laboratory-scale DCMD set-up. After applying the pressure, the cross-sections and surfaces of the membranes were examined using a scanning electron microscope (SEM). Results showed that the membrane structural parameters such as porosity and thickness were changed under relatively high pressure conditions (>30 kPa), leading to reduction in flux. The mass transfer coefficients were also significantly influenced by the hydraulic pressure. Moreover, local wetting of the membranes were observed even below the liquid entry pressure (LEP), which decreased the rejection of salts. These results suggest that the control of hydraulic pressure is important for efficient operation of DCMD process.

Evaporation at a Liquid Surface Due to Jet Impingement

1986 ◽  
Vol 108 (2) ◽  
pp. 411-417 ◽  
Author(s):  
E. M. Sparrow ◽  
S. W. Celere ◽  
L. F. A. Azevedo
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Water Surface ◽  
Liquid Surface ◽  
Jet Impingement ◽  
Separation Distance ◽  
Operating Conditions ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Air Jet

Experiments were performed to determine mass transfer coefficients for evaporation from a water surface on which an air jet impinged. During the course of the experiments, parametric variations were made of the jet velocity and diameter, the separation distance between the jet origin and the water surface, the diameter of the water surface, and the degree of insulation of the water containment pan. It was found that for all of the investigated operating conditions, the dimensionless mass transfer coefficient varied with the 0.8 power of the jet Reynolds number. Furthermore, the transfer coefficient decreased linearly as the separation distance between the jet origin and the water surface increased, with the most significant decreases occurring at relatively small values of the surface-to-jet diameter ratio. At larger diameter ratios, the transfer coefficient was relatively insensitive to the separation. In general, the larger the diameter of the water surface, the lower the transfer coefficient. Comparisons with the literature showed that the dimensionless mass transfer coefficients for impingement on a liquid surface are lower than those for impingement on a solid surface.

scholarly journals Atenolol removal by nanofiltration: a case-specific mass transfer correlation

2020 ◽  
Vol 81 (2) ◽  
pp. 210-216 ◽  
Author(s):  
Alexandre Giacobbo ◽  
Elisa Veridiani Soares ◽  
Andréa Moura Bernardes ◽  
Maria João Rosa ◽  
Maria Norberta de Pinho
Keyword(s):  
Mass Transfer ◽  
Membrane Fouling ◽  
Concentration Polarization ◽  
Membrane Separation ◽  
Film Theory ◽  
Operating Conditions ◽  
Transfer Coefficients ◽  
Specific Mass ◽  
Mass Transfer Coefficients ◽  
Mass Transfer Correlation

Abstract Concentration polarization is a phenomenon inherent to membrane separation operations and as a precursor of membrane fouling is frequently related to the decrease in the performance of these operations. In the present work, a case-specific mass transfer correlation was developed to assess the concentration polarization when nanofiltration, in different operating conditions, was applied to treat a pharmaceutical wastewater containing atenolol. NF runs with two membranes, two atenolol concentrations and three feed circulating velocities were conducted, and the corresponding experimental mass transfer coefficients were determined using film theory to describe the concentration polarization phenomenon. Higher velocities led to higher mass transfer coefficients and, consequently, lower concentration polarization. These mass transfer coefficients were correlated with the circulating velocity (Re), the solute diffusivity (Sc) and the membrane permeability (LP+) (the membrane is a permeable interface with effect on the concentration profiles developed from the interface towards the bulk feed), yielding the following correlation Sh = 1.98 × 104Re0.5Sc0.33LP+0.32. The good agreement between the calculated and the experimental results makes this correlation a valuable tool for water practitioners to predict and control the concentration polarization during atenolol-rich wastewater treatment by nanofiltration, thereby increasing its productivity and selectivity.

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