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This paper reviews a series of cases for which the correct determination of the mass transfer coefficient is decisive for an appropriate design of the system and its operating conditions. The cases are of interest for applications in the energy sector, such as the thermoconversion of a fuel particle, processes in pipes, packed and fluidised beds, and corollary unit operations, such as extraction, absorption, and adsorption. The analysis is carried out by examining the expressions for the determination of the Sherwood number (which contains the mass transfer coefficient), and, when possible, generalised relationships (also in graphic form) have been provided, to offer a useful tool to cognoscenti. [ABSTRACT FROM AUTHOR]

The adsorption isotherms and intraparticle mass transfer coefficients of a novel adsorbent with various VOCs at different temperatures during the desorption process are investigated. Firstly, the adsorption isotherms of an HCP-5 adsorbent with o-xylene and ethyl acetate systems were determined at temperatures ranging from 30 to 160 °C, and the data were fitted using the Langmuir adsorption isotherm equation. Subsequently, a mathematical model for the fixed-bed desorption breakthrough of VOCs was established. By combining with fixed-bed desorption breakthrough experiments, the intraparticle mass transfer coefficients of o-xylene and ethyl acetate during the desorption process at different temperatures were obtained through the least squares method. This study revealed that the intraparticle mass transfer coefficients of o-xylene and ethyl acetate during the desorption process were basically equal. The intraparticle mass transfer coefficients increased and then decreased with temperature during the desorption process. Compared with the adsorption process, the contribution of surface diffusion inside the adsorbent pores to intraparticle mass transfer decreased during the desorption process, leading to a significant decrease in the intraparticle mass transfer coefficients, which were approximately one-twentieth of those during the adsorption process. [ABSTRACT FROM AUTHOR]

The continuous [C] content prediction model in molten steel of the all-scrap electric arc furnace was established through the explicit finite difference method combined with numerical simulation based on the thermodynamics and kinetics of the decarburization reaction. Initially, a method to figure out the average [C] content of mixed input scrap was proposed, which provided a basis for subsequent calculations. Furthermore, scrap melting rate, mixing side-blowing/bottom stirring, and oxygen blowing intensity adjustment of oxygen lance had been considered as the three key elements. Decreasing scrap melting time was beneficial to improving the EAF efficiency because it accounts for 80% of the total operation time. The research found that the scrap melting rate was mainly affected by the solid-liquid phase heat transfer and [C] content transfer, and the heat transfer played a dominant role. Applying mixing side blowing/bottom stirring could lead to an improvement in the mass transfer coefficient of the decarburization reaction, and the value was increased from the range of 0.0059 s−1-0.021 s−1 by using single side-blowing to the range of 0.0079 s−1-0.023 s−1. The mass transfer coefficient could be enhanced by the oxygen intensity adjustment of oxygen lances when mixing side blowing/bottom stirring was used. This was a benefit of deeper jet impact zones on the molten steel surface caused by high oxygen flow. After the model was applied to an industrial site, the prediction accuracy of the endpoint [C] content within the error range of ±0.02% and ±0.01% reached 91.2% and 85.7%, respectively.

The mass transfer from a stagnant CO2 gas pocket to the flowing water in a horizontal pipe was investigated experimentally, considering the application of pH adjustment by injecting gaseous CO2 for raw water in water treatment industries. In the experiments, the variation of the CO2 gas pocket volume and the corresponding pH values of the pipe flow with time under different conditions were recorded. The mass transfer coefficient of the CO2 gas pocket in the pipe flow was then calculated. The results showed that the injection of gaseous CO2 into the pipe flow could effectively adjust the pH. The volume of the CO2 gas pocket decreased exponentially. Different from most studies on bubble mass transfer, it was found that the ambient CO2 concentration could not be neglected in this study due to the large volume of the gas pocket and the restricted space in the pipe. The mass transfer coefficient increased with the increasing ratio of the CO2 injection rate to the water flow rate and exhibited a sharp reduction as the volume of the CO2 gas pocket decreased by about 80%. The outcomes of this paper can contribute to a better understanding of gas bubble mass transfer in pipe flows. HIGHLIGHTS The mass transfer of a large CO2 gas pocket in the horizontal pipe flow was investigated, which has been hardly reported before.; During mass transfer processes, the pH variation of the pipe flow could be divided into three regimes, and the volume of the gas pocket was reduced exponentially.; The CO2 concentration in the pipe flow is important to mass transfer due to the large volume of the gas pocket and the restricted space in the pipe.;

The active ingredients in peppermint are widely used in the pharmaceutical, food, cosmetic, and other industries. The traditional methods for producing peppermint extract through hydrodistillation (HD) and percolation are long process with low efficiency. The aim of this study is the improvement of the extraction performance and the efficiency of the extract obtained from hot percolation via pulsed disk and doughnut columns (PDDC), which is one of the most important pieces of liquid–liquid extraction (LLE) equipment. Peppermint extract was used as the continuous phase in the PDDC. n‐Hexane was considered as the dispersed phase in this column. In this study, the effects of three operating parameters were investigated, including the pulse intensity, continuous phase height, and dispersed phase flow rate, on the extraction efficiency of active ingredients in peppermint. The response surface method (RSM) was used to investigate the effect of these parameters on the extraction efficiency. The efficiency of this column in the extracting of active ingredients from peppermint was measured by UV–vis spectrophotometry, via the absorption rate of the main active ingredients of peppermint (menthol) in the samples, and the efficiency was 75% on average. The experimental and theorical of dispersed phase mass transfer coefficient were evaluated and compared. The results showed that the PDDC improved the extraction and mass transfer. By increasing the flow rate of the dispersed phase and the height of the continuous phase, the extraction efficiency and the mass transfer coefficient were increased. [ABSTRACT FROM AUTHOR]

The electrodeposition process confronts significant challenges arising from mass transfer limitation and residual stress. To address these issues, an innovative method, combining megasonic agitation with coaxial jet electrodeposition, is introduced. This approach aims to enhance mass transfer and mitigate residual stress. First, an electrodeposition nozzle device was designed, and the liquid-phase mass transfer during electrodeposition was analyzed through finite element simulation. Simulation results indicate that the mass transfer coefficient increases with rising megasonic power density. Notably, when the megasonic power density reached 20 W/cm2, the mass transfer coefficient increased from 0.45 × 10−7 m/s to 18.63 × 10−7 m/s, compared to electrodeposition without megasonic agitation. Secondly, electrodeposition experiments were conducted both with and without megasonic assistance. X-ray diffraction (XRD) was employed to measure the residual stress values of the electrodeposited layers. The results reveal that samples processed with megasonic assistance exhibit lower residual stress values compared to those without. Specifically, at a megasonic power density of 10 W/cm2, the residual stress was 94.3 MPa, representing a 37.7 % reduction compared to the residual stress of 151.5 MPa observed in samples without megasonic agitation. Overall, the findings demonstrate that coaxial megasonic agitation can effectively enhance the liquid-phase mass transfer capability during electrodeposition and reduce the residual stress of the electroplated layer. This innovative method presents a promising avenue for improving electrodeposition processes and achieving superior material properties.

This study investigates the design of a stirred batch reactor with scale-up for the degumming of crude palm oil (CPO) using phosphoric acid (H3PO4). Laboratory-scale experiments were conducted in a triple-neck round vessel, followed by a scale-up to a larger-scale flat-bottom stirred tank reactor. Traditional scale-up methods using geometric similarity criteria are ineffective for reactors with different geometries; hence, this work introduces an improved approach using degumming efficiency, measured by gum concentration, as the similarity criterion to design the reactor. Computational Fluid Dynamics (CFD) was employed to model the velocity distribution and mass transfer processes, predicting gum concentration evolution through gum mass balances in the oil and aqueous phases. The simulation results showed that maintaining a minimum impeller speed of 93 rpm in the larger reactor effectively reproduced the best degumming efficiency observed in the laboratory reactor at 500 rpm and 60 °C. A strong correlation (R2 = 0.963) was found between the modeled and empirical Sherwood numbers, indicating successful scale-up. This research demonstrates that degumming efficiency in a laboratory triple-neck round vessel can be numerically reproduced in a larger flat-bottom stirred tank reactor, providing valuable insights into the hydrodynamic characteristics unique to each geometry and marking a pivotal step in reactor scale-up methodologies.

ABSTRACTThe present work focuses on the construction of a counter flow dehumidification test rig where calcium chloride liquid is used as the desiccant and is made to spray on the novel organic packing made of wood shaving with different densities and porosities. The mass flow rate of the air is varied and the performance parameters such as moisture removal rate (MRR), dehumidification effectiveness, coefficient of performance (COP), sensible heat factor (SHR) and mass transfer coefficient have been investigated. Results demonstrated an increase in the relative humidity, mass transfer coefficient and drop in the COP, MRR and dehumidification efficiency with the increase in the flow airflow rate. On increasing the CaCl2 concentration, dehumidification performance parameters such as MRR, COP and mass transfer coefficient are found to be increased. Out of the three different densities tested, 500 kg/m3 shows best performance with MRR, ΔRH and dehumidification effectiveness being 9.7%, 18.7% and 4.9% lower than the Celdek pad when measured at 5 m/s of air velocity for 30% desiccant concentration. Optimisation of the input parameters has been done and the results revealed that air velocity should be maintained within the range of 4–5 m/s to minimise energy consumption and optimum performance.

Radioactive iodine is a representative fission product to be quantified for the safety assessment of nuclear facilities. In integral severe accident analysis codes, the iodine behavior is usually described by a multi-physical model of iodine chemistry in aqueous phase under radiation field and mass transfer through gas-liquid interface. The focus of studies on iodine source term evaluations using the combination approach is usually put on the chemical aspect, but each contribution to the iodine amount released to the environment has not been decomposed so far. In this study, we attempted the decomposition by revising the two-film theory of molecular-iodine mass transfer. The model involves an effective overall mass transfer coefficient to consider the iodine chemistry. The decomposition was performed by regarding the coefficient as a product of two functions of pH and the overall mass transfer coefficient for molecular iodine. The procedure was applied to the EPICUR experiment and suppression chamber in BWR.

Since slag and coal fly ash (CFA) are major global pollutants produced by thermal power plants (TPPs), special attention should be paid to their rational disposal. Scanning electron microscopy (SEM) was used to study the morphology of CFA and it was suggested that the use potential of CFA is high due to the presence of a large number of cenospheres (CSs), that can be recovered mostly by wet methods for the production of the wide range of products with improved properties. However, such decisions regarding the application of the cenospheres are largely related to the problem of their drying after removal. The article is devoted to the investigation of the filtration method as less energy-consuming for the drying of cenospheres. The effect of the drying agent velocity on the mass transfer intensity has been established. The values of mass transfer coefficients have been calculated based on the thin-layer experimental data and equation . Calculated mass transfer coefficients for cenospheres have been correlated by the dimensionless expression , based on which equation has been proposed to calculate the mass transfer coefficients, which is important at the filtration drying equipment design stage.

This study was conducted to investigate the drying kinetics and internal and external mass transfer characteristics of walnuts for an understanding of the drying mechanism. The drying characteristics, mass transfer characteristics, and color of walnut during hot air drying (HAD) were investigated under different initial moisture content (IMC) (0.35, 0.39, and 0.43 g water/g wet mass) and drying temperatures (50, 60, 70, and 80 °C). The results indicated that the IMC and drying temperature both have significant effects on the drying process of walnut, showing the higher the IMC, the longer the preheating time, the smaller the effective moisture diffusivity (Deff) and mass transfer coefficient (hm), and the longer the drying time, but reverse results for drying temperature. The values of Deff and hm for walnut ranged from 4.94 × 10−10 to 1.44 × 10−9 m2/s and 1.24 × 10−7 to 3.90 × 10−7 m/s, respectively. The values of activation energy for moisture diffusion and mass transfer ranged from 21.56 to 23.35 kJ/mol and 28.92 to 33.43 kJ/mol, respectively. Multivariate linear prediction models were also established for estimating the Deff and hm as a function of the HAD process parameters. The drying temperature has a greater effect on the walnut kernel lightness than the IMC. The Verma et al model could be used to describe the HAD process of the walnut. The findings contribute to the understanding of moisture transfer mechanisms in walnuts and have practical value for the evaluation and improvement of drying systems. [ABSTRACT FROM AUTHOR]

Bubble mass transfer is a common phenomenon in industrial applications. In this paper, bubble dynamics in both still and turbulent flow were introduced first, followed by the mass transfer properties of a single bubble and bubble swarms. Then, bubble mass transfer models for different scenarios were summarized, including three classical models, extended models, eddy diffusion and whirlpool theoretical models, and semi- or empirical correlations. Finally, existing methods for mass transfer intensification in industries were reviewed. Despite extensive researches, the mechanism for bubble mass transfer has not been fully understood. Models are commonly limited to some specific conditions and the accuracy is limited, especially for bubble swarms and bubble mass transfer in turbulent and non-Newtonian fluids. Also, the mass transfer intensification methods have their own limitations. Additional exploration of knowledge on bubble mass transfer models and further improvement in mass transfer intensification technologies are still required in the future.

In this study, a simultaneous removal of cadmium, cobalt, and nickel from an aqueous solution through the Green Emulsion Liquid Membrane (GELM) method was carried out. A 7:3 ratio of sunflower oil to kerosene was utilized as the membrane phase stabilized by Span 80 as the emulsifier. D2EHPA as a carrier and HCl as an inner phase were used. Extraction and stripping efficiencies of 97.45% and 98.42% for Cd2+, 96.82% and 97.84% for Co2+, 89.74% and 92.69% for Ni2+, respectively, with the lowest breakage (0.8%) were obtained under the best operating conditions. An extensive investigation of the influence of homogenizer speed, external and internal phase acidity, the HLB value of the surfactant (Tween 80 and Span 80), surfactant and carrier concentrations, volume ratio of the membrane to internal phase, mixer speed, ratio of external to membrane phase emulsification time and extraction time on the stability of membrane, extraction, and stripping efficiencies were carried out. Kinetic analysis of cadmium, cobalt, and nickel extraction was performed using zero, first, and second-order models at optimum conditions. The experimental data fit well with first-order for three metal ions. The coefficient of the total mass transfer (Ft) of cadmium through the GELM technique was 3.28% higher than that of cobalt and 28.61% higher than that of nickel, while the Ft of cobalt is 25.33% higher than that of nickel. Using the recovered membrane, the extraction of the three metal ions for the initial six cycles was extremely efficient under the best conditions.

Jatropha curcas L. seeds are good sources of industrial-grade oil for biodiesel production and feedstock for thermochemical conversion to other biofuels. Freshly harvested seeds are wet and susceptible to deterioration due to enzymatic and microbial activities, excess moisture also limits the efficiencies of biofuel production processes. Hence, they require moisture removal by drying pre-treatment before storage and further industrial processing. Drying characteristics and moisture transfer properties of Jatropha seeds are also needed for the design, analysis and optimization of the process. Jatropha curcas seeds were dehydrated in a convective hot-air dryer at 80 - 140 °C using 1.5 m s − 1 air velocity. Dehydration rates and energy consumption were evaluated from the dehydration data. Coefficients of diffusion and mass transfer as well as activation energy were estimated by the Crank, Dincer-Dost, Biot-Lag factor (Bi-G), Biot-Drying constant (Bi-S), Biot-Dincer (Bi-Di) and Biot-Reynolds (Bi-Re) moisture transfer models. The dehydration kinetics of the seeds were also defined by thin-layer dehydration models. The dehydration rate was enhanced by drying at higher temperatures and occurred in the falling-rate phase. The energies needed to dehydrate the seeds were 0.155 – 0.184 kWh/kg fresh seed at 80 – 140 °C. Diffusion coefficients, moisture transfer coefficients and activation energies evaluated by the models were 0.975 – 3.013 × 10−8 m2 s − 1, 0.316 × 10−6 – 4.88 × 10−6 m s − 1 and 16.1 - 26.8 kJ mol−1 at 80 – 140 °C, respectively. Dincer-Dost, Bi-G, Bi-S, Bi-Di and Bi-Re moisture transfer models aptly predicted dimensionless moisture content profile. The Weibull model was the thin-layer drying model that best described the dehydration kinetics of the seeds. Moisture transfer properties and drying rate of Jatropha seeds can be enhanced and energy requirement minimized by drying seeds at higher temperatures, thus reducing the overall cost of processing seeds and boosting the profitability of biofuel production from the seeds.

This paper reviews a series of cases for which the correct determination of the mass transfer coefficient is decisive for an appropriate design of the system and its operating conditions. The cases are of interest for applications in the energy sector, such as the thermoconversion of a fuel particle, processes in pipes, packed and fluidised beds, and corollary unit operations, such as extraction, absorption, and adsorption. The analysis is carried out by examining the expressions for the determination of the Sherwood number (which contains the mass transfer coefficient), and, when possible, generalised relationships (also in graphic form) have been provided, to offer a useful tool to cognoscenti.

The synthesis of fatty acid methyl ester from soybean oil was examined. A microreactor was used as a reactor, and the results were compared with those by batch reaction. In a batch reaction experiment, the concentration of by-product glycerol was large when methanol/soybean oil ratio was low, which inhibited the mass transfer between methanol and oil, and as a result, reduced fatty acid methyl ester yield. On the other hand, when the reaction was conducted under an emulsion state using a microreactor, the initial reaction rate was significantly increased, achieving a specific interfacial area about 7 times larger than that of the batch reaction. Furthermore, the decrease in reaction rate was suppressed and the space-time fatty acid methyl ester yield was successfully increased. When the reaction was conducted under a segmented flow state, the initial reaction rate decreased because of the smaller specific interfacial area. However, the mass transfer coefficient increased about 30-fold, and furthermore, the phase separation was completed immediately after the reaction. Finally, the high temperature and high-pressure flow operation was conducted using a microreactor, which enabled an efficient fatty acid methyl ester production from soybean oil at 2 – 3 times higher space-time yield with less amount of catalyst and/or methanol use compared to the conventional batch production method.

Cycle voltammetric behaviour of Cu(II)SO4 in aqueous NaCl (supporting electrolyte) has been explored in comprehensive manner. 5 mM Cu2+, 1.0 M NaCl and glass carbon (GC) reveals the optimum response. Two stage electromechanical redox EE mechanism [(Cu2+/Cu+) and (Cu+/ Cu0)] has been explored by using different theoretical and experimental methods. The mass transfer co-efficient, dimensionless parameters and heterogeneous electron transfer rate constant (k0) confirmed the quasi-reversible response of (Cu2+/Cu+) redox couple. The experimental Gileadi (k0) and simulated Digi Sim (k0) values found as 0.052 cm/s and 0.0012 cm/s respectively. The diffusion co-efficient (D) of (Cu2+/Cu+) redox couple computed from 9.96 X 10-6 to 4.43 X 10-6 cm²/s through different quasi-reversible response of (Cu2+/Cu+) through obtained electrochemical and kinetic parameters by using simple, fast, and cost-effective technique. [ABSTRACT FROM AUTHOR]

The aim of this work was to assess the terms associated with mass transfer in the lycopene recovery from the waste of a tomato canning plant. Moringa oleifera Lam oil was employed as solvent. An ultrasonic extraction was carried out on skin and seeds. The operational variables were temperature (skin: 45, 60, 75, 90 ºC; seed: 45, 60, 75 ºC), matrix/solvent ratio (m/v) (1:20, 1:25, 1:30), particle size (skin: < 1, 1-2, > 3.15 mm; seed: < 1, 1-2, > 2 mm) and extract separation method (filtration and centrifugation). Kinetic constant, lycopene concentration on the solid surface, volumetric coefficient of mass transfer and effective diffusivity were determined. The more the kinetic constant increased, the higher the volumetric coefficient of mass transfer was. Effective diffusivity increased with temperature. Activation energy values suggest a possible deterioration of lycopene at temperatures higher than the optimum. The use of M. oleifera oil as solvent should increase the biological value of the lycopene extracts.

The aim of this work was to assess the terms associated with mass transfer in the lycopene recovery from the waste of a tomato canning plant. Moringa oleifera Lam oil was employed as solvent. An ultrasonic extraction was carried out on skin and seeds. The operational variables were temperature (skin: 45, 60, 75, 90 °C; seed: 45, 60, 75 °C), matrix/solvent ratio (m/v) (1:20, 1:25, 1:30), particle size (skin: < 1, 1-2, > 3.15 mm; seed: < 1, 1-2, > 2 mm) and extract separation method (filtration and centrifugation). Kinetic constant, lycopene concentration on the solid surface, volumetric coefficient of mass transfer and effective diffusivity were determined. The more the kinetic constant increased, the higher the volumetric coefficient of mass transfer was. Effective diffusivity increased with temperature. Activation energy values suggest a possible deterioration of lycopene at temperatures higher than the optimum. The use of M. oleifera oil as solvent should increase the biological value of the lycopene extracts. [ABSTRACT FROM AUTHOR]

Studies of phase transition kinetics are important for such supercritical processes as supercritical drying, adsorption, micronization, etc. In supercritical technologies, "organic solvent—CO2" systems are often formed, the properties of which strongly depend on the system parameters. In this article, the kinetic curves of phase transitions in the "2-propanol—CO2" system were investigated experimentally and theoretically. Experimental studies were carried out in a 250 mL high-pressure apparatus at temperatures of 313 and 333 K and pressures of 6.3 and 7.8 MPa with and without the addition of alginate porous gel. Theoretical studies were carried out using the mass transfer equation, the Peng-Robinson equation of state, and the Van der Waals mixing rules, with Python being used for the calculations. The mass transfer coefficients and equilibrium concentrations of CO2 in the liquid phase were determined using the BFGS optimization method. [ABSTRACT FROM AUTHOR]

The challenging task in our ecosystem is to reduce acidic gas emissions to some extent. Many gases are emitted from the industries like H2S, CO, CO2, SO2, NO, and NO2 as exhaust gases. Among these gases, CO2, NO2, and SO2 are acidic, which results in adverse effects on humans, animals, and plants. The increase in the emission of CO2 gases from both anthropogenic and industrial sources resulted in CO2 mitigation studies. CO2 absorption studies were carried out using iron oxide nanofluid with the novel structured packed absorption column. Iron oxide nanoparticles were synthesized and characterized using XRD, SEM, and TEM analysis. Ammonia is used as an absorbent along with iron oxide nanofluid of three different concentrations (0.0001 w/v%, 0.001 w/v%, and 0.0015 w/v%). It was found that the iron oxide nanofluid of 0.0015 w/v% showed an improved % CO2 removal efficiency. This enhanced % CO2 removal efficiency was due to the increased interfacial area of the ameliorated contact between the liquid and gas phases. In addition, the magnetic field was introduced along with the packed column, which increased CO2 removal efficiency by 1.5%.

The removal of lambda-cyhalothrin (LCT) from an aqueous solution was investigated and evaluated by the emulsion liquid membrane (ELM) technique using Span 80 as the surfactant, n-hexane as the diluent, and HCl as the stripping phase. Crucial parameters influencing the stability of emulsions through breakage and extraction efficiency, such as emulsification time, surfactant concentration, contact time, emulsification speed, internal phase concentration, external phase-to-membrane volume ratio, effect of feed pH, mixing speed, and internal phase-to-membrane volume ratio were investigated. The results indicated that 94.7% of LCT could be extracted at a contact time of 8 min under ideal experimental conditions, with a low membrane breakage of 0.48%. Furthermore, the extraction kinetics were investigated and the mass transfer coefficient was estimated. Based on the obtained results, the ELM technique could be a promising alternative method to minimize environmental pollution caused by pesticides to a large extent. [ABSTRACT FROM AUTHOR]

The challenging task in our ecosystem is to reduce acidic gas emissions to some extent. Many gases are emitted from the industries like H2S, CO, CO2, SO2, NO, and NO2 as exhaust gases. Among these gases, CO2, NO2, and SO2 are acidic, which results in adverse effects on humans, animals, and plants. The increase in the emission of CO2 gases from both anthropogenic and industrial sources resulted in CO2 mitigation studies. CO2 absorption studies were carried out using iron oxide nanofluid with the novel structured packed absorption column. Iron oxide nanoparticles were synthesized and characterized using XRD, SEM, and TEM analysis. Ammonia is used as an absorbent along with iron oxide nanofluid of three different concentrations (0.0001 w/v%, 0.001 w/v%, and 0.0015 w/v%). It was found that the iron oxide nanofluid of 0.0015 w/v% showed an improved % CO2 removal efficiency. This enhanced % CO2 removal efficiency was due to the increased interfacial area of the ameliorated contact between the liquid and gas phases. In addition, the magnetic field was introduced along with the packed column, which increased CO2 removal efficiency by 1.5%. [ABSTRACT FROM AUTHOR]

This article presents the results of hydrodynamics and mass exchange in a stirred tank upon the introduction of gas from an open gas vortex cavity into local liquid regions with reduced pressure. It establishes conditions for the intensive dispersion of gas. Velocity fields and liquid pressure behind the stirrer paddles are determined by numerical simulation in OpenFOAM. The gas content value, gas bubble diameters, and phase surface are determined experimentally. The stirrer power criterion is calculated by taking into account the gas content and power input. The experimental mass transfer data based on the absorption of atmospheric oxygen into water during the dispersion of gas from the open vortex cavity in the local liquid regions behind the rotating stirrer paddles are presented. In this case, the energy dissipation from the rotating stirrer reaches 25 W/kg, with a phase surface of 1000 m−1 and a surface mass transfer coefficient of up to 0.3·10−3 m/s. These parameters are obviously higher than the data obtained in the apparatus for mass exchange through surface vorticity. The advantage of the given method for gas dispersion in a liquid is the functional stability of the apparatus regardless of how deep the stirrer is immersed in the liquid or the temperature or pressure of the gas. Apparatuses based on the intensive gas dispersion method allow for varying the mass transfer coefficient and gas content across a broad range of values. This allows establishing a dependency between the experimentally obtained mass transfer coefficient, energy dissipation, and phase surface values. An equation for calculating the mass transfer coefficient is formulated by taking into account the geometric parameters of the stirrer apparatus based on the stirring power and phase surface values. [ABSTRACT FROM AUTHOR]

Development of energy-efficient and high-performance bioreactors requires progress in methods for assessing the key parameters of the biosynthesis process. With a wide variety of approaches and methods for determining the phase contact area in gas–liquid flows, the question of obtaining its accurate quantitative estimation remains open. Particularly challenging are the issues of getting information about the mass transfer coefficients instantly, as well as the development of predictive capabilities for the implementation of effective flow control in continuous fermentation both on the laboratory and industrial scales. Motivated by the opportunity to explore the possibility of applying classical and non-classical computer vision methods to the results of high-precision video records of bubble flows obtained during the experiment in the bioreactor vessel, we obtained a number of results presented in the paper. Characteristics of the bioreactor's bubble flow were estimated first by classical computer vision (CCV) methods including an elliptic regression approach for single bubble boundaries selection and clustering, image transformation through a set of filters and developing an algorithm for separation of the overlapping bubbles. The application of the developed method for the entire video filming makes it possible to obtain parameter distributions and set dropout thresholds in order to obtain better estimates due to averaging. The developed CCV methodology was also tested and verified on a collected and labeled manual dataset. An onwards deep neural network (NN) approach was also applied, for instance the segmentation task, and has demonstrated certain advantages in terms of high segmentation resolution, while the classical one tends to be more speedy. Thus, in the current manuscript both advantages and disadvantages of the classical computer vision method (CCV) and neural network approach (NN) are discussed based on evaluation of bubbles' number and their area defined. An approach to mass transfer coefficient estimation methodology in virtue of obtained results is also represented. [ABSTRACT FROM AUTHOR]

Packed-bed bioreactors are often used for aerobic solid-state fermentation, since the forced aeration supplies O2 and removes metabolic heat from the bed. Motivated by the potential for applications in biorefineries, we review studies conducted on packed-bed bioreactors over the last decade, evaluating the insights these studies provide into how large-scale packed beds should be designed and operated. Many studies have used low superficial air velocities and suffer from preferential airflow, such that parts of the bed are not properly aerated. Moreover, some studies have proposed ineffective strategies, such as reversing the direction of the airflow or introducing air through perforated pipes within the bed. Additionally, many studies have used narrow water-jacketed packed-bed bioreactors, but these bioreactors do not reflect heat removal in wide large-scale packed beds, in which heat removal through the side walls makes a minor contribution. Finally, we conclude that, although some attention has been given to characterizing the porosities, water sorption isotherms and volumetric heat and mass transfer coefficients of substrate beds, this work needs to be extended to cover a wider range of solid substrates, and work needs to be done to characterize how these bed properties change due to microbial growth. [ABSTRACT FROM AUTHOR]

The two major scale-up criteria in continuously stirred bioreactors are 1) constant aerated power input per volume (Pg/Vl), and 2) the volumetric O2 mass transfer coefficient (kla). However, Pg/Vl is only influenced by the stirrer geometry, stirrer speed, aeration and working volume, while the kla is additionally affected by physiochemical properties of the medium (temperature, pH, salt content, etc.), sparging of gas and also by the bioreactor design. The extremophilic archaeon Sulfolobus acidocaldarius, thriving at 75°C and pH 3.0, has the potential for many biotechnological applications. However, previous studies imply that the family Sulfolobaceae might be affected by higher oxygen concentration in the headspace (>26%). Hence, adequate oxygen supply without being toxic has to be ensured throughout the different scales. In this study, the scale-up criteria Pg/Vl and kla were analyzed and compared in a 2 L chemostat cultivation of S. acidocaldarius on a defined growth medium at 75°C and a pH value of 3.0, using two different types of spargers at the same aerated power input. The scale-up criterion kLa, ensuring a high specific growth rate as well as viability, was then used for scaleup to 20 L and 200 L. By maintaining a constant kla comparable dry cell weight, specific growth rate, specific substrate uptake rates and viability were observed between all investigated scales. This procedure harbors the potential for further scale-up to industrial size bioreactors.

Processes of sucrose diffusion inside plant fruits and their generalization require special attention, namely theoretical generalization of experimental data and organization of energy-saving production of candied fruits while preserving the quality of the finished product. This work deals with the experimental and theoretical studies of the kinetics, hydrodynamics and mass transfer of the process of zucchini fruits saturation with sucrose from an aqueous solution. Experimental studies were conducted in static and dynamic modes. In static mode, fruit saturation occurs from an aqueous solution of sucrose in a stationary state of the solution. Dynamic mode occurs under conditions of air bubbling of an aqueous sucrose solution. Specific heat consumption of the studied modes of saturation of zucchini fruits in sugar syrup was theoretically calculated. The kinetic process of changes in the sucrose concentration in zucchini fruits at different rates of air supply for bubbling was studied in detail. It was found that the process kinetics occur in the regions of external and internal diffusion. Based on Fick's law, a generalization of the saturation processes of the particles of zucchini fruits with sucrose in the external diffusion region was carried out using the similarity theory. The existence of three hydrodynamic regimes during fruit saturation in dynamic mode was proved. Criterion equations were derived allowing us to theoretically calculate the mass transfer coefficient under the conditions of three hydrodynamic regimes. From technological and economic points of view, the most expedient process of zucchini fruit particles saturation with sucrose occurs at a syrup temperature of 70°С and a rate of air flow for bubbling from 6 to 8 m/s. The derived criterion equation allows to establish the numerical value of the air pressure for bubbling depending on the air supply rate.

This study was conducted to investigate the drying kinetics and internal and external mass transfer characteristics of walnuts for an understanding of the drying mechanism. The drying characteristics, mass transfer characteristics, and color of walnut during hot air drying (HAD) were investigated under different initial moisture content (IMC) (0.35, 0.39, and 0.43 g water/g wet mass) and drying temperatures (50, 60, 70, and 80 °C). The results indicated that the IMC and drying temperature both have significant effects on the drying process of walnut, showing the higher the IMC, the longer the preheating time, the smaller the effective moisture diffusivity (Deff) and mass transfer coefficient (hm), and the longer the drying time, but reverse results for drying temperature. The values of Deff and hm for walnut ranged from 4.94 × 10−10 to 1.44 × 10−9 m2/s and 1.24 × 10−7 to 3.90 × 10−7 m/s, respectively. The values of activation energy for moisture diffusion and mass transfer ranged from 21.56 to 23.35 kJ/mol and 28.92 to 33.43 kJ/mol, respectively. Multivariate linear prediction models were also established for estimating the Deff and hm as a function of the HAD process parameters. The drying temperature has a greater effect on the walnut kernel lightness than the IMC. The Verma et al model could be used to describe the HAD process of the walnut. The findings contribute to the understanding of moisture transfer mechanisms in walnuts and have practical value for the evaluation and improvement of drying systems.

In this paper, the results of the study on aluminium evaporation from the Al-Zn alloys (4.2% weight) during remelting in a vacuum induction furnace (VIM) are presented. The evaporation of components of liquid metal alloys is complex due to its heterogeneous nature. Apart from chemical affinity, its speed is determined by the phenomena of mass transport, both in the liquid and gas phase. The experiments were performed at 10-1000 Pa for 953 K - 1103 K. A significant degree of zinc loss has been demonstrated during the analysed process. The relative values of zinc loss ranged from 4 to 92%. Lowering the pressure in the melting system from 1000 Pa to 10 Pa caused an increase in the value of density of the zinc evaporating stream from 3.82⋅10-5 to 0.000564 g⋅cm-2⋅s-1 at 953 K and 3.32⋅10-5 to 0.000421 g⋅cm-2⋅s-1 for 1103 K. Based on the results of the conducted experiments. it was found that evaporation of zinc was largely controlled by mass transfer in the gas phase and only for pressure 10 Pa this process was controlled by combination of both liquid and gas phase mass transfer.

Hydrogen sulphide (H2S) emissions in sewer systems lead to several problems such as corrosion, odour nuisances, and health damage to sewer workers. Although the gas is formed in the liquid phase, its effects are noticeable when released into the sewer atmosphere. Until recently, the lack of analytical procedures for continuous monitoring of H2S in the liquid phase, as well as its toxicity, have challenged the quantification of the mass transfer coefficient under real conditions. Because of this, most studies have mainly focused on batch experiments with artificial wastewater and/or oxygen. The aim of this study was to experimentally determine the overall mass transfer coefficient for H2S during intermittent pumping events common in actual sewer systems, using the two-film theory approach and employing online sensors for liquid and gas phase measurements. The mass transfer coefficient was quantified by carrying out 21 experiments with actual wastewater in a 25 m long gravity pipe of a sewer pilot plant located in Berlin (Germany). Results show that the corrected mass transfer coefficient (KLa20) during a pumping event ranged between 0.1 and 8 h−1 with a median value of 4.2 h−1, within the range of the results obtained by the most common empirical models. HIGHLIGHTS Online sensors enable data acquisition for determining the H2S mass transfer coefficients across the liquid–gas interface.; Experiments were carried out in a sewer pilot plant with actual wastewater.; During pumping the KLa20 coefficient for H2S had a median value of 4.2 h−1.;

The current paper focuses on assessing key parameters affecting the extraction of Chlorpyrifos as well as emulsion stability using the emulsion liquid membrane technology. Five parameters affecting the extraction have been studied: homogenizer speed, emulsification time, agitating time, surfactant concentration, and stripping phase concentration taking into consideration the emulsion breaking. Experiments proved that using the resulting optimum values will maximize both extraction and stripping efficiencies (93.8% and 94.7% respectively), while minimizing the emulsion breakage (increasing the stability of emulsion) to 0.73% with no need to employ a carrier agent. A 10 min agitating time, 3% (v/v) Span 80 as a surfactant, 12700-rpm homogenizer speed, 0.25 M HCl as an internal phase concentration, and 5 min emulsification time are chosen to be the optimum parameters' values. A study of extraction kinetics and estimation of mass transfer coefficient was also accomplished (3.89×10-9 m/s). The conclusions of this work can be extended to the removal of other types of pesticides from water. [ABSTRACT FROM AUTHOR]

A compact static mixer for gas–liquid dispersion in pipelines is studied in this paper with a Reynolds averaged two fluid model approach. A procedure based on the lumped parameter solution of a population balance model is applied to obtain the bubble Sauter mean diameter needed to model the interphase forces. The gas distribution in the pipe is analyzed in two different operative conditions and the efficiency of the static mixer is assessed in terms of the gas homogeneity in the pipe section, with low coefficients of variations being obtained. A computational model to obtain the volumetric mass transfer coefficient, kLa, developed for partially segregated systems is applied finding kLa values comparable to those typically obtained with other static mixers. The proposed computational model allows us to locally analyze the oxygen transfer rate by observing the limitations due to gas accumulation behind the body of the static mixer, which leads to the local depletion of the driving force. Geometrical optimization of the static element is proposed, based on the analysis of gas–liquid fluid dynamics and of the interphase mass transfer phenomena. [ABSTRACT FROM AUTHOR]

This research work deals with the performance of high-density polyethylene sheets arranged in splash used as a fill for a cooling tower. “A forced-draught counterflow cooling tower” of 400 mm × 400 mm cross-sectional area and 1.7m in height was built. The fill has been studied theoretically and experimentally. Air rates of 0.6, 1.2, and 1.8 kg/s.m2 were utilized with water flow rates within the range of 1 to 1.6 kg/s.m² . The overall volumetric heat transfer coefficient, volumetric mass transfer coefficient (Mt), and the tower characteristics (Mt/L) are shown to be functions of the air and water flow rates concurrently. Four available input parameters were inlet water temperature, airflow rate, water flow rate, and full height. A computer program was prepared to perform numerical analysis for reducing data sets obtained from the plant. In addition, analysis was carried out for evaluating the volumetric heat and mass transfer coefficients along with the performance coefficient. [ABSTRACT FROM AUTHOR]

The development of energy-efficient solutions for large-scale fermenters demands a deep and comprehensive understanding of hydrodynamic and heat and mass transfer processes. Despite a wide variety of research dedicated to measurements of mass transfer intensity in bubble flows, this research subject faces new challenges due to the topical development of new innovative bioreactor designs. In order to understand the fluid dynamics of the gas–liquid medium, researchers need to develop verified CFD models describing flows in the bioreactor loop using a progressive physical and mathematical apparatus. In the current paper, we represent the results of evaluating the key performance indicator of the bioreactor, namely the volumetric mass transfer coefficient ( k L a ) known as a parameter of dominant importance for the design, operation, scale-up, and optimization of bioreactors, using the developed thermometry method. The thermometry method under consideration was examined within a series of experiments, and a comparative analysis was provided for a number of various regimes also being matched with the classical approaches. The methodology, experiment results, and data verification are given, which allow the evaluation of the effectiveness and prediction of the fluid flows dynamics in bioreactors circuits and ultimately the operational capabilities of the fermenter line. [ABSTRACT FROM AUTHOR]

The desulfurization behavior of 316L stainless steel (STS316L) melt with the CaO-SiO2-CaF2-Al2O3-MgO slag was investigated with different CaO/SiO2 (=C/S) ratio and CaF2 content at 1873 K. As the C/S ratio increased, the sulfide capacity increased, whereas the sulfide capacity of the high C/S (=1.7) slag was not affected by CaF2 content. The overall mass transfer coefficient (kO) increased with C/S ratio, but was constant above a critical C/S value, and it was also constant across varied CaF2 content at relatively high C/S (=1.7) condition. Since the metal condition of the present study was constant, the change in kO was caused by slag phase mass transfer coefficient (ks) and sulfur distribution ratio (LS), which were affected by the physicochemical properties of the slag. Since desulfurization reaction requires consideration of both kinetic and thermodynamic factors, the ‘logCS2−−logη’ (where CS2− is sulfide capacity and η is viscosity), was proposed as a meaningful physicochemical parameter. If the slag basicity is relatively high, at which the kO is equivalent regardless of slag compositions, the desulfurization reaction is controlled by metal phase mass transfer. However, if the slag basicity becomes lower, at which the kO significantly decreases, the desulfurization reaction is assumed to be controlled by slag phase mass transfer and/or mixed controlled process.

The current experimental study looks at how the limiting current density is approached on using rotating 2-stage 4- blade flat turbine promoters to improve mass transfer coefficient in an open electrolytic cell. The mass transfer data are obtained at microelectrodes fixed on the cell wall and electrode support using an electrochemical method. The electrolyte was equimolal in potassium ferricyanide, potassium ferrocyanide and excess sodium hydroxide. The mass transfer coefficients were calculated using limiting current data from a diffusion-mediated electrode reduction reaction at the microelectrodes attached to the electrode supports. The limiting current technique has been particularly chosen in view of its accuracy, simplicity, negligible chemical polarization, and absence of any physical change to the reacting surface even after long exposure. The effects of geometric parameters such as turbine diameter (0.05-0.09 m), blade width (0.005-0.015m), turbine rotational speeds (250-1250 rpm) and electrolyte velocity (0.567x10-3 to 7.93x10-3 m/s) were investigated. The mass transfer coefficients were increased by the turbulence created by rotation of the promoter turbines. The mass transfer correlation was formed in terms of dimensionless numbers: Schmidt number (Sc), Sherwood number (She), rotational Reynolds number (Rer), and flow Reynolds number (Ref).

The dissolution of Ti–N solids in liquid titanium was investigated using experimental and numerical methods. To characterize the dissolution rate and the transport phenomena associated with the dissolution process, cylindrical Ti–N rods were immersed into a molten pool of commercially pure titanium produced using an electron beam button furnace. Tests were conducted for various immersion times to observe the evolution in the rod tip profile and measure the volume loss. Generally, the volume fraction of dissolved solid increases with increasing immersion time. A numerical model has been developed to describe the experimental process and aid in understanding the dissolution process. Overall, the predicted volume loss for different immersion times agrees well with the experimental measurements. An effective mass transfer coefficient, in the range of 4.2 × 10−5 to 4.9 × 10−5 m/s, has been derived based on the model results for the experimental conditions examined (e.g. interface velocities and temperatures in the range of 0.09 – 0.11 m/s, and 1766 – 1778 °C, respectively).

[Display omitted] The electrodeposition process confronts significant challenges arising from mass transfer limitation and residual stress. To address these issues, an innovative method, combining megasonic agitation with coaxial jet electrodeposition, is introduced. This approach aims to enhance mass transfer and mitigate residual stress. First, an electrodeposition nozzle device was designed, and the liquid-phase mass transfer during electrodeposition was analyzed through finite element simulation. Simulation results indicate that the mass transfer coefficient increases with rising megasonic power density. Notably, when the megasonic power density reached 20 W/cm2, the mass transfer coefficient increased from 0.45 × 10−7 m/s to 18.63 × 10−7 m/s, compared to electrodeposition without megasonic agitation. Secondly, electrodeposition experiments were conducted both with and without megasonic assistance. X-ray diffraction (XRD) was employed to measure the residual stress values of the electrodeposited layers. The results reveal that samples processed with megasonic assistance exhibit lower residual stress values compared to those without. Specifically, at a megasonic power density of 10 W/cm2, the residual stress was 94.3 MPa, representing a 37.7 % reduction compared to the residual stress of 151.5 MPa observed in samples without megasonic agitation. Overall, the findings demonstrate that coaxial megasonic agitation can effectively enhance the liquid-phase mass transfer capability during electrodeposition and reduce the residual stress of the electroplated layer. This innovative method presents a promising avenue for improving electrodeposition processes and achieving superior material properties. [ABSTRACT FROM AUTHOR]

To comprehensively utilize Fe and P in oolitic hematite ore, an innovative method was proposed to enhance P enrichment in the reduced iron during the reduction process. The reduced iron was then converted to low-P-containing molten iron and high-P-containing slag in the presence of CaO–SiO2–FeO–Al2O3 slag. In this study, the P content of the final iron after 0–1,800 s dephosphorization was investigated at different slag composition conditions, and the dephosphorization kinetics of the reduced iron was analyzed. The results showed that the P content of the final iron sample decreased rapidly within 600 s of dephosphorization and became almost constant with increasing dephosphorization time to 1,800 s. The basicity, FeO content, and Al2O3 content also affected the dephosphorization rate of the reduced iron. The apparent dephosphorization rate constant ranged from 1.141 × 10−3 to 2.363 × 10−3 g·(cm2·s)−1, and the overall mass transfer coefficient ranged from 2.47 × 10−3 to 3.38 × 10−3 cm·s−1. The rate-controlling step of the dephosphorization process was the mass transfer of P in both the slag and iron phases. The findings of this study provide a theoretical basis for the utilization of refractory oolitic hematite ore.

The desulfurization in metallurgical process is electrochemical reaction in nature. Desulfurization using the electrochemical method was proposed with the CaO-MgO-Al2O3 molten slag covering molten steel. Effect of an applied external DC voltage, which varied from 0 to 8V, was discussed. The results indicated that sulfur in molten steel could be removed effectively with applied external voltage. According to the mechanism analyses of the desulfurization under the applied external voltage, kinetics formulae were developed, and the model calculated results that were in agreement with the experimental values. The transfer coefficient of sulfur in molten slag under electromigration conditions was approximately 2.09×10-5 m·s-1·V-1. The desulfurization of molten steel with molten slag can be promoted by increasing the applied voltage, reducing the partial pressure of atmospheric oxygen, strengthening the stirring intensity of the reaction system, and optimizing the composition and properties of the slag.

The relative importance of the physical resistances to mass transfer have been explored by using halved 13 mm diameter apple-pectin tablets containing caffeine, in different external stirring environments within a beaker containing simulated gastric fluid. The effects of different external (outside of the tablets) mass-transfer resistances to the tablets created through two different stirrer types and stirrer speeds, and different internal (inside of the tablets) mass-transfer resistances created through different tablet concentrations and thicknesses, have been studied. These studies enable internal diffusion coefficients of caffeine through the apple pectin matrix to be estimated, as well as estimating the external mass-transfer coefficients from benzoic acid dissolution, which are in the range of 6.5 × 10-6 m/s – 2.4 × 10-5 m/s for the 0.6 mm thick tablets and 4.0 × 10-6 m/s – 1.6 × 10-5 m/s for the 7 mm thick tablets. The diffusion coefficients for different caffeine concentrations in the apple pectin half-tablets have also been calculated in this study. The diffusivity of caffeine in the 7 mm half-tablets with 1% caffeine through 99% pectin was around (1.8 ± 0.5) × 10-10 m2/s. This study points towards the development of multifilm mass-transfer theory for food digestion to create a more fundamentally based understanding of in-vitro digestion systems as an addition to the use of realistic in-vitro food digestion apparatus and give a better correlation between in-vitro and in-vivo digestion tests.

Flow-Accelerated Corrosion (FAC) is a pipe wall thinning phenomenon to be monitored and managed in the power plants with high priority. Its management has been conducted with conservative evaluation of thinning rate and residual lifetime of piping based on wall thickness measurements. However, in the actual plants, noticeable case of the wall thinning occurred in branch and junction piping (T tube). There is a problem to manage the wall thickness of the part covered by reinforcing plate of the T tube, because measurement of this area is difficult to be conducted with ordinary ultrasonic testing devices due to the presence of the reinforcing plate. In this study, numerical flow analysis for the T tube was conducted, and the wall thinning profile due to the FAC was evaluated by calculating the mass transfer coefficient. It was found that a localized wall thinning distribution occurs in the area where the reinforcement plate of the T tube exists. And this tendency is affected by pipe geometry and Reynolds number. In previous studies, a model that functionalized by pipe geometry and Reynolds number was introduced to predict this wall thinning trend. In this paper, the effectiveness of the proposed decay function was confirmed by comparing it with measurements taken in actual plants. It was shown that the maximum wall thinning rate at the T tube junction, including below the reinforcing plate, can be evaluated conservatively within an appropriate range by making corrections to the proposed decay function that take into account the causes of variation in the actual data.

The spray of water over a basin using a perforated disk accelerates oxygen transfer. The laboratory model, employed in the current work, consists of a vertical riser that discharges water by free fall into a basin. Four fall heights of water of 2.4, 1.8, 1.2, and 0.6 m were investigated to evaluate the performance of this system. This system was also tested at flow rates of 46.8, 93.7, 140.6, and 187.5 mL/s. This study showed that the oxygen mass transfer coefficient was directly proportional to both the fall height and flow rate of water. The maximum standard aeration efficiency (SAE) value was recorded at the maximum fall height of 2.4 m and flow rate of 187.5 mL/s, at which a maximum KLa20 = 1.82 h–1 was recorded. The multilinear regression-based model developed in this study successfully predicted mass transfer coefficient (KLa20) and standard aeration efficiency (SAE values that agree well with actual measurements under given conditions, with a scattering within ±5%. The optimum flow rate and fall height that achieve the minimum operating cost were obtained at certain KLa20 values. The cost of aeration of 1 m3 of water was calculated, ranging from 0.0076 to 0.008 USD/m3. [ABSTRACT FROM AUTHOR]

Processes of sucrose diffusion inside plant fruits and their generalization require special attention, namely theoretical generalization of experimental data and organization of energy-saving production of candied fruits while preserving the quality of the finished product. This work deals with the experimental and theoretical studies of the kinetics, hydrodynamics and mass transfer of the process of zucchini fruits saturation with sucrose from an aqueous solution. Experimental studies were conducted in static and dynamic modes. In static mode, fruit saturation occurs from an aqueous solution of sucrose in a stationary state of the solution. Dynamic mode occurs under conditions of air bubbling of an aqueous sucrose solution. Specific heat consumption of the studied modes of saturation of zucchini fruits in sugar syrup was theoretically calculated. The kinetic process of changes in the sucrose concentration in zucchini fruits at different rates of air supply for bubbling was studied in detail. It was found that the process kinetics occur in the regions of external and internal diffusion. Based on Fick's law, a generalization of the saturation processes of the particles of zucchini fruits with sucrose in the external diffusion region was carried out using the similarity theory. The existence of three hydrodynamic regimes during fruit saturation in dynamic mode was proved. Criterion equations were derived allowing us to theoretically calculate the mass transfer coefficient under the conditions of three hydrodynamic regimes. From technological and economic points of view, the most expedient process of zucchini fruit particles saturation with sucrose occurs at a syrup temperature of 70°С and a rate of air flow for bubbling from 6 to 8 m/s. The derived criterion equation allows to establish the numerical value of the air pressure for bubbling depending on the air supply rate. [ABSTRACT FROM AUTHOR]

Distributions of the pressure and mass transfer coefficient on rotating blades under low-pressure (low-Reynolds-number) conditions were visualized, whereas the latter is closely related to the skin-friction distribution. Two types of optical measurement techniques, lifetime-based pressure-sensitive paint (PSP) measurements and sublimation visualization, were implemented for the experiment inside a low-pressure chamber. For the lifetime-based PSP measurement, different types of PSP were compared, and the one most suitable in low-pressure applications was selected. In addition, the gate time setting for the low-pressure condition was determined. For the sublimation method, naphthalene was selected as the sublimation surface based on previous studies. The rotating blade test model was a 0.3-m-diam rotor system with two rectangular blades with an aspect ratio of two. The experiments were carried out at a rotational speed of 2400 rpm and at an ambient pressure of 10 kPa. The three-fourth-span Reynolds number was 9000. The pitch angle of the blades was set to 0-20 deg. Both methods successfully illustrated clear images of the distribution of pressure and mass transfer coefficients on the upper surface of the blade, and the measurement in the low-pressure environment was successful. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of different operating conditions and the air-to-water ratio (G/L) on the kinetics and the mass transfer coefficient of ammonia (KL) in the air stripping method for removing ammonium ions (NH4+) from wastewater with low concentrations in municipal wastewater treatment plants (WWTPs). The impact of operating conditions including the temperature, initial ammonium ion concentration, pH, and air-to-water ratio (G/L) of

A number of industrial operations are linked to mass transfer. The mass transfer coefficient value is necessary to know when designing the industrial equipment in which mass transfer occurs. There are various mass transfer coefficients, as well as equations for their calculation. However, the value of these coefficients determined according to these equations often has to be corrected for the given conditions. The aim of the article is to state the conversion relations - the correction factors enabling the calculation of the mass transfer coefficients values corresponding to the given conditions.

Using nanoparticles can lead to an increase in mass transfer rate in liquid–liquid extraction systems. Increasing the concentration of nanoparticles in liquids results in the deposition of nanoparticles and thus limits its use in extraction systems. In this paper, the effect of adding a surfactant to nanoparticle in liquid-liquid extraction systems on extraction efficiency is investigated. The effect of surfactant concentration on the extraction efficiency has been investigated both separately and in the presence of nanoparticles. In this research, the effect of continuous and dispersed phase velocity, and pulsation intensity on the hydrodynamic characteristics of the system has been investigated for the first time with the simultaneous use of silica nanoparticles and SDS surfactant in the vertical pulsed packed column.Using hydrodynamic system and in the presence of nanoparticles and surfactant, this research article provides optimum conditions to obtain maximum efficiency with minimum additives and pulsation intensity. ANOVA analysis (three-level Box–Behnken experimental design) has been used to investigate the effective parameters and sensitivity analysis. The results showed that pulsation intensity is the most effective factor on response. With increasing pulsation intensity from 1 to 2.5, the droplet size decreases and hold-up is increased from 0.02 to 0.05 (at Qd=Qc= 2 lit/s) in the system. Also, the effects of adding SiO2 nanoparticles and Sodium dodecyl sulfate (SDS) surfactant into a chemical system on the hydrodynamic characteristics were studied. The results showed that by adding nanoparticles the droplet size decreases while hold-up increases. Finally, a semi-empirical correlation has been proposed to predict the droplet size in terms of operational parameters, the system chemical properties and the nanoparticle volume fraction. It was found that when pulsation intensity, nanoparticle concentration and surfactant concentration were 1.75, 0.1, and 0.05 respectively, extraction efficiency increased to 0.98.