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The 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. [ABSTRACT FROM AUTHOR]

Convective drying is one of the most commonly employed preservation techniques for food. However, the use of high temperatures and extended drying times often leads to a reduction in product quality and increased energy consumption. To address these issues, hybrid processes combining convective drying with more efficient methods are frequently employed. This study investigates the convective rotary drying of carrot (cv. Nantes), assisted by microwaves and ultrasound, using a hybrid rotary dryer. In total, four distinct drying programs—comprising one convective and three hybrid approaches—were evaluated. The study assessed drying kinetics, energy consumption, and product quality. The use of ultrasound increased the drying rate by 13%, microwaves by 112%, and microwaves and ultrasound together by 140%. The use of microwaves reduced energy consumption by 30%, whereas ultrasound resulted in a slight increase. All processes resulted in a significant reduction in water activity. Ultrasound decreased the color difference index, while microwaves increased it compared to convective drying. [ABSTRACT FROM AUTHOR]

Pumpkin seeds swagger a wealthy vitamin and mineral composition. They contain vitamins (A, B, C, K, D, E), minerals (calcium, selenium, zinc, magnesium, copper, potassium, press, manganese and phosphorus), a few amino acids such as glutamic, linolenic and arginine, and greasy plant acids. The Peclet number includes the peripheral rotation speed of the RTS condenser tube. In our case, the Peclet number reflects how the heat transfer to the grain layer due to convection, when the RTS capacitor rotates, relates to the heat transfer due to the thermal conductivity of the grain layer. Thus, in the first drying period, the determining factors for mass transfer will be the conditions at the phase boundary – the mode of air movement outside the grain, the area of the grain, the surface temperature of the RTS condenser. In total, pumpkin seeds contain 12 essential and eight nonessential amino acids. [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.

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]

A method is proposed for determining the coefficient of ozone mass transfer between the gas phase and an aqueous solution of HCl + NaCl. The method is based on minimizing the functional of discrepancy between the dependences of the specific reaction rate of O3 with Cl–(aq) on the concentration of hydrogen ions determined from experiment and obtained from reference data. The method also allows estimation of the true Henry constant in acidic solutions of chlorides. [ABSTRACT FROM AUTHOR]

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.

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.

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.;

Phosphorus is a critical impurity in solar cell that deteriorates the photovoltaic convection efficiency of solar cell. Phosphorus removal from metallurgical grade silicon by injecting H 2 and Ar-50%H 2 mixture during the Al–Si solvent refining was investigated. With gas injecting into the Al–Si melt, the phosphorus concentration in the refined Si decreased with an increase of the injecting time. When the gas injecting time was 2.5 h, the removal fraction of phosphorus increased to 93%, an improvement of 63% compared with 57% without Ar–H 2 injection. The effects of H 2 proportion, gas refining temperature, and Si proportion in the alloy were investigated. The kinetics of phosphorus removal with Ar–H 2 injection were clarified. The mass transfer coefficient of phosphorus was 9.07 × 10−9 m/s during the Ar–H 2 -assisted solvent refining process. Three mechanisms of phosphorus removal were discussed for this gas-solvent composite refining process. These results demonstrate that H 2 or Ar–H 2 gas injecting treatment is an effective strategy to further improve the phosphorus removal and reduce the cost during Al–Si solvent refining. • The removal fraction of P increased to 93% with Ar–H 2 injection refining process. • The mass transfer coefficient of P was 9.07 × 10−9 m/s during solvent refining. • The kinetics of P removal with Ar–H 2 injection were clarified. • H 2 injection is an effective way to improve the P removal during solvent refining. [ABSTRACT FROM AUTHOR]

In this work, external mass transfer phenomena around hydrogen selective Pd-based membranes were analyzed experimentally and mathematically modelled. A supported Pd-Ag membrane was tested in pure hydrogen and in hydrogen/nitrogen mixtures using three different membrane lengths. Pressure, temperature, gas flow rate and feed composition were varied to obtain an elaborate dataset that could be used for analysis and modelling. Strong influences of concentration polarization and hydrogen depletion were observed. Various empirical correlations describing gas phase mass transfer around a tubular membrane from literature were tested, but none of them yielded a sufficiently accurate prediction of concentration polarization observed in the experiments. Therefore, a new Sherwood correlation was fitted using the dataset. The obtained correlation (Sh = 1.846 ∙ G z 0.60) showed significantly improved predictive behavior for the system used in this work and represents a potentially powerful tool for the modelling of membrane separators for pure hydrogen production. • H2 separation of Pd-based membranes is influenced by concentration polarization and hydrogen depletion. • In this work, extensive experiments were performed with a PdAg membrane at three different lengths. • The experimental dataset was used to evaluate the accuracy of multiple mass transfer correlations. • The new Sherwood correlation(s) showed significant improvement compared to literature. [ABSTRACT FROM AUTHOR]

Selenium (Se) is an important nutritional element which exists at very low concentrations, easily accumulates via the food chain and creates adverse effects such as a deprived reproduction rate and diminutive growth in human and aquatic organisms. So, it has become a severe concern around the world. We explore electrocoagulation using Al and Fe electrodes and activated sludge process (ASP) in batch process and also in an integrated process to remove Se. The optimized parameters of the current density in the batch process were: 6.7 and 5.7 mA/cm2 for Al and Fe, respectively. The mass transfer coefficient has been estimated through numerical modelling for batch and integrated processes using the equations K = and K = ; the energy consumption and metal dissolution were 138240 and 384 MWh/m3, 60 and 3.58 g, respectively. The response surface methodology (RSM) was implemented in Box−Benken design to assess the parametric optimization, and the validation of experimental data was done using ANOVA and regression analysis. The obtained p-values and model F-values were 0.000 and 63.09 for Al and 0.000 and 79.98 for Fe, which indicated the significance of the model. The chemical oxygen demand (COD) reduction values estimated along with Se reduction in real effluent treatment were above 90 and 60% in electrolytic and 80% in an integrated ASP with very high-cost efficiency. The results assure that this proposed hybrid work will provide a higher reduction, improved energy and cost efficiency for the effluent with indeterminate influent Se and COD concentration. The proposed model also helps to make predictions of removal efficiency without requiring an extensive time and cost burden. [ABSTRACT FROM AUTHOR]

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 boundary conditions for describing the mass transfer of carbon from oxygen-free low-pressure atmospheres into steel during vacuum carburizing are analyzed. The effect of the content of carbide-forming alloying elements on the values of the carbon potential of low-pressure acetylene atmospheres is determined depending on the temperature of the process of vacuum carburizing. Temperature dependences of the carbon mass transfer coefficient are derived. [ABSTRACT FROM AUTHOR]

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.

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.

In view of the close relationship between gas-liquid mass transfer performance and flow regime, the coaxial mixer was selected as the research object, and the effects of rotation mode, inner impeller diameter, gas flow rate, and viscosity on flow regimes were experimentally investigated. The results showed that the main growth interval of the mass transfer coefficient was the loading regime, and the critical complete dispersion regime was an efficient and economic operation condition. In this state, the co-rotation mode had a low-power advantage compared to the counter-rotation mode. The anchor speed and gas flow rate could improve mass transfer performance, but at the expense of higher power consumption. Although it was easier to achieve the complete dispersion regime with a larger diameter impeller, the mass transfer performance was reduced at this time. The viscosity had a significant negative influence on gas-liquid dispersion and mass transfer performance. In terms of impeller combinations, PBTD+Anchor and RT+Anchor performed well in low and high viscous systems, respectively. In addition, applying the artificial neural network model to estimate the N cd for the coaxial mixer correlated with the studied parameters to recognize the complete dispersion regime. [Display omitted] • The critical complete dispersion regime was the most efficient operating condition. • Effects of rotation mode, inner diameter impeller, gas flow rate, and liquid viscosity were investigated. • PBTD+Anchor and RT+Anchor performed well in low- and high-viscous systems, respectively. • Mathematical model for accurate estimation of the N cd of the coaxial mixer were established. [ABSTRACT FROM AUTHOR]

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]

Silicone rubber materials may be subject to mechanical strains which can affect the transport properties of small molecules loaded in the materials such as plasticizers and active molecules, hence deteriorating their intended mechanical properties or affecting their performance as carriers of active molecules. Therefore, it is important to understand the effects of mechanical strains on transport of small molecules in the silicone rubber matrix. In this work, silicone rubber sheets loaded with 2 wt% triacetin were stretched and held at four different lengths up to 125% engineering strain. The mass transfer coefficients and diffusion coefficients of triacetin in the strained silicone rubber were determined by monitoring the release of triacetin using headspace gas chromatography–mass spectrometry. It was found that there was no significant change of diffusion coefficient as the applied strain increased, which might result from two microstructure changes that had conflicting effects on diffusion: chain orientation and free volume deformation. [ABSTRACT FROM AUTHOR]

The adsorptive removal of methylene blue (MB) from its aqueous solution using citric acid-modified arjun bark powder as an adsorbent was studied. Initially, the adsorbent was characterized by various analytical techniques (SEM, BET, FTIR, and pHpzc). After characterizing the adsorbent, it was used for carrying out batch study on the biosorption of MB. The batch experiments revealed a very high percentage removal of MB of about 100%. The batch experiment results followed Temkin isotherm. The maximum monolayer adsorption capacity observed was 512.82 mg/g at natural pH of 7.5. The Freundlich isotherm constant was found to be 300.15 l/g. The Temkin isotherm constant was found to be 21.32 l/mg. The sorption energy was calculated from the Dubinin–Radushkevich isotherm model, and it was found to be 10 kJ /mol. On the other hand, results followed the pseudo-second-order kinetic model. The energy of activation in the present study was estimated to be 10 kJ/mol. The adsorptive mass transfer coefficient was calculated to be 1.65 × 10–7 m/s, and the value of diffusivity was found to be 2.27 × 10–11. [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.

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 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.

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.

In this research, a granular Eulerian multiphase model coupled with heat and mass transfer was used to simulate the convective drying process of iron ore fines. The CFD model was validated with experimental data for different air temperatures and air velocities. Convective drying experiments were performed using laboratory-scale equipment in order to obtain drying kinetics data for iron ore fines at air temperatures up to 140 °C and air velocities up to 15 m/s. The drying system had combined characteristics of fluidized bed and pneumatic transport. Numerical results showed good agreement with experimental data (average RMSE of 3.9 × 10−3) for the moisture content for nine drying air conditions. Since the coupled momentum, heat and mass transfer model could accurately and validly estimate the drying rate for iron ore fines according to the local conditions of the drying air in laboratory-scale equipment, it has potential for application in CFD simulations of industrial-scale equipment. [ABSTRACT FROM AUTHOR]

The essential oil and effluent of herbs contain various active components, of which flavonoids are a big family. The wastewater of chamomile obtained from hydrodistillation is used as a continuous phase in the rotating disk column. Also, n-hexane was chosen as the dispersed phase. This study investigates the extraction of flavonoids using liquid–liquid extraction and examines the theoretical and empirical relations for mass transfer coefficients and effective diffusivity in chamomile effluent. The operating parameters are the rotor speed, dispersed phase flow rate, and continuous phase height. The response surface method has been considered, and a new empirical model has been proposed to predict the extraction efficiency as a function of operating parameters applying an optimal design. The results showed that the extraction efficiency ranges from 25% to 50%. A simultaneous increase in operating parameters increases extraction efficiency, but the continuous phase height has an almost negligible effect. Moreover, the individual and overall volumetric mass transfer coefficients have been increased by increasing the rotor speed and dispersed phase flow rate. The comparison of the experimental mass transfer coefficient with Newman, Kronig-Brink, and Handlos-Baron's equations showed a good agreement of experimental data with the ones obtained from the Newman equation because of the rigid droplets. [ABSTRACT FROM AUTHOR]

Numerical and experimental studies were carried out for the analysis of hydrodynamics and volumetric mass transfer coefficient (kLa) in a cross-T junction microchannel for gas–liquid, two phase flow system. Initially, CO2–water hydrodynamics simulation was performed using ANSYS-FLUENT 2021 R2 and volume of fluid technique. Through the numerical simulation, fluctuation in pressure drop with variation in volume fraction was calculated for the slug flow in a 1 mm hydraulic diameter microchannel. After that mass transfer equations were coupled with the flow equations for CO2–ethyl glycol, CO2–water, and CO2–ethyl alcohol systems to understand the mass transfer mechanism using two film theory concepts. Computational fluid dynamics model was validated by comparing results with the experimental data. An empirical co-relation was also developed to measure the bubble length with its position in the direction of fluid flow. CO2 and solvents velocities were 0.21–0.424 m/s for both the phase. Effect of solvents and film thickness (0.01–0.05 mm) on volumetric mas transfer coefficient were investigated at different temperatures range i.e., T = 298.15 K and 303.15 K (experimental approach) and 298.15–318.15 K (numerical approach). The results obtained in numerical simulation and experimental work show that the total volumetric mass transfer coefficient (range 0.1–0.8 1/s) increases with the gas velocity however, it decreases with increasing film thickness (0.01–0.05 mm) and temperature (T = 298.15 K and 303.15 K). The present work gives an advantage over the conventional channel (e.g., packed bed column) and the other type of T-junction microchannel (e.g., symmetric T-junction) by providing a high mixing rate, interfacial area, and high mass transfer rate. [ABSTRACT FROM AUTHOR]

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 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.

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 mass transfer and mixing performance in the static mixers with three twisted leaves (TKSM) were investigated by the computational fluid dynamics coupled population balance model. A high-precision and efficient gas-liquid two phase model were evaluated by considering several drag models based on experimental bubble size distributions. The bubble size prediction matched well with experimental data and the mean relative error of Sauter mean diameter (d32) between the prediction and experiment values is 4.93 %. The drag correction factor considering hindering effect of small bubbles can improve the accuracy of cumulative probability distribution (CPD) prediction by 10.06 %. Bubble breakup capacity is quantized via gas-liquid interfacial area, and an empirical correlation between Eo and bubble aspect ratio (γ) have been proposed to predict morphological characteristics of bubble swarms. The effect of liquid Re on the mass transfer rate is much more significant than that of gas volume fraction (αd). The coefficients of variation profiles show that RL-TKSM has better mixing efficiency compared with LL-TKSM and perfect mixing could be achieved after seven mixing elements. The micro mixing efficiency of RL-TKSM is 1.06–1.14 times that of LL-TKSM, which indicates that RL-TKSM has excellent mixing and mass transfer performances. [ABSTRACT FROM AUTHOR]

Carbon dioxide absorption using amine based solvents is a well‐known approach for carbon dioxide removal. Especially with the increasing concerns about greenhouse gas emissions, there is a need for an optimization approach capable of multifactor calibration and prediction of interactions. Since conventional methods based on empirical relations are not efficiently applicable, this study investigates use of Response Surface Methodology as a strong optimization tool. A bubble column reactor was used and the effect of solvent concentration (10.0, 20.0 and 30.0 vol%), flow rate (4.0, 5.0 and 6.0 L min−1), diffuser pore size (0.5, 1.0 and 1.5 mm) and temperature (20.0, 25.0 and 30.0°C) on the absorption capacity and also overall mass transfer coefficient was evaluated. The optimization results for maintaining maximum capacity and overall mass transfer coefficient revealed that different optimization targets led to different tuned operational factors. Overall mass transfer coefficient decreased to 34.7 min−1 when the maximum capacity was the desired target. High reaction rate along with the highest absorption capacity was set as desirable two factor target in this application. As a result, a third scenario was designed to maximize both mass transfer coefficient and absorption capacity simultaneously. The optimized condition was achieved when a gas flow rate of 5.9 L min−1, MEA solution of 29.6 vol%, diffuser pore size of 0.5 mm and temperature of 20.6°C was adjusted. At this condition, mass transfer coefficient reached a maximum of 38.4 min−1, with a forecasted achievable absorption capacity of 120.5 g CO2 per kg MEA. [ABSTRACT FROM AUTHOR]

The experimental procedure is developed and tested on a laboratory scale and using layered samples of manmade geomaterials. Within the dual-permeability model, the procedure enables determining parameters that govern fluid flow and poroelastic deformation in fractured porous rock masses, namely, fracture permeability and mass transfer coefficient , as well as their dependence on stresses . The testing procedure is proposed and implemented. In the procedure, under the stepwise increasing normal stress , the stationary flow rates and are measured in a quasiregular fractured porous sample at the preset pressure difference: using a standard setup () and in closed end-face fractures (). The mathematical model of the experiment is constructed, and the analytical solution of the problem on stationary flow is obtained: pressure patterns in fractures, and stress-dependence of flow rates. The experimental data interpretation algorithm enables calculating and by the recorded flow rates and . It is shown that the permeability is proportional to , and remains almost unchanged. [ABSTRACT FROM AUTHOR]

The study of impurity removal kinetics in the refining and purification of industrial silicon is essential to refine the purification process and improve impurity removal efficiency. In this paper, influencing rules of slag system compositions, a mass ratio of slag to silicon (slag/silicon), and refining time with impurity aluminum content in industrial silicon were investigated by slagging refining experiments. The values of apparent rate constant (kAl) and mass transfer coefficient (βAl) of aluminum acquired from refining time and its corresponding impurity content were 1.42 × 10–4 s−1 and 7.90 × 10–7 m·s−1, respectively. Experimental results showed that the rate of silicon loss increases slightly with the increase of refining time during slagging refining compared to gas blowing refining. The influence of refining time on silicon loss during slagging refining is much less than that of gas blowing refining, which was more suitable for the refining operation of industrial silicon. [ABSTRACT FROM AUTHOR]

Particle dissolution in stirred vessels is a unit operation commonly encountered in several production sectors, such as the mineral, pharma and chemical industries. It is commonly conducted batch-wise under time-dependent conditions, a circumstance that complicates model set-up. This paper presents a set of models for simulating batch dissolution of polydisperse particles in stirred vessels. These models cover all scenarios of particle batch dissolution, regardless of whether the initial particle quantity exceeds or falls short of achieving solution saturation. Consequently, they address cases where particles are either completely dissolved or remain partially undissolved. The models also account for both single-sized and multi-sized particles. Convenient model simplifications are also provided for the cases of final solute concentration much smaller than saturation (low final concentration models). All models are successfully experimentally validated. The single-size large final concentration model is employed to set up experimental runs that, apart from their use in predictive simulations, may be employed for simultaneously measuring mass transfer coefficient and interfacial solute concentration using suitable experimental runs. The ability to measure interfacial solute concentration is also exploited for assessing whether it coincides, or not, with the solute saturation concentration, a common assumption when dealing with solid-liquid mass transfer, which in the present case is found to hold true. The simpler single-size low-final-concentration model is very convenient for measuring the mass transfer coefficient alone. Finally, the multi-size model is utilised to evaluate the sensitivity of the estimated mass transfer coefficient in the single-size model to the particle size range employed during experimental measurements of mass transfer coefficients. • A comprehensive set of models is presented for particles dissolution in stirred vessels. • Models are employed for measuring mass-transfer coefficient and interfacial concentration. • The case of particles with size distribution is also tackled. [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 °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]

A novel multiscale flow battery simulation approach is presented. Therefore, the mass transfer coefficient (MTC) is extracted from the 3D‐resolved microscale simulations, transferred to the homogenized cell scale and compared to empirical formulations from literature. The models are parameterized with an organic system and experimentally validated on the microscale. It resolves the real geometry of the electrode microstructure obtained by experimental image reconstruction from microtomography. It accounts for flow, mass, and coupled charge transport using Butler–Volmer kinetics. It is suitable to study power density as a function of concentration, velocity, and discharge rate. The MTC is extracted under transfer‐limiting operating conditions. Bulk and surface concentrations of active material and the reaction rate are used. The 2D homogenized cell‐scale model considers half‐cell single species transport and reduced order reaction. The extracted MTC is implemented as a function of state of charge (SOC) and velocity, distinctive for specific initial concentration and discharge rate. It is used to calculate the reaction rate for evolving species in the electrode and is investigated in a parameter study. The approach is compared to empirical formulations of the MTC based on velocity. It can be shown that the MTC is one order of magnitude higher and depends significantly on SOC. [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%.