Understanding Of Mass Transfer Research Articles

Dual-Cation CuAgSe-Based Material: Rapid Mass Transfer in Synthesis and High Thermoelectric Performance Realization.

Understanding mass transfer mechanisms is vital for developing new material synthesis and densification technologies. Ion transport, serving both mass and charge transfer, is essential for the rapid preparation of high-performance fast ionic conductor thermoelectric materials like Zn4Sb3 and Cu2Q (Q = S, Se). In the case of dual-cation fast ion conductor materials like CuAgSe, exploring the relationship between cation transport becomes pertinent. In this study, copper (Cu) and selenium (Se) undergo a reaction in the presence of an electric field (∼15 A), resulting in the formation of the CuSe compound. Subsequent to this initial reaction, a subsequent thermal environment facilitates the interaction among Cu, CuSe, and Ag2Se, culminating in the rapid formation and densification of CuAgSe (with a relative density exceeding 99%) in just 30 s. Evidently, the diffusion of copper ions substantiates a pivotal role in facilitating mass transfer. As a result, CuAg1+xSe samples with different silver contents (x = 0.01, 0.02, 0.03, 0.04 and 0.05) can effectively inhibit cation vacancy, and introduce highly ordered Ag nanotwins to enhance the electrical transport performance. For CuAg1.04Se, a peak ZT value of 1.0 can be achieved at 673 K, which is comparable to the literatures. This work will guide the future electric field-assisted rapid mass transfer of materials.

Natural Convection in Molten Salt Electrochemistry.

Molten salt electrochemistry has been widely used in many fields, especially for metal extraction/refinement. The understanding of mass transfer in molten salts under harsh operation conditions is of great importance to reveal reaction mechanisms and advance fine technologies. It has been generally assumed that natural convection is negligible in stagnant molten salt electrochemistry. Herein, we report an abnormal natural convection in molten LiCl-KCl, with the arising time from 2.37 s at 873 K to 10.13 s at 673 K. Using the concentration correction factor, the derived thickness of the natural convection-diffusion layer (δconv.) was found to be ranging from 128 to 163 μm, much thinner than those in aqueous solutions (∼200 μm). The simulations showed that the notable natural convection resulted from convection-diffusion layer (CDL) convection dominated over the density-driven convection even at high redox concentrations, implying the severe vibration of molten salt systems. To suppress the intense natural convection, we predicted that the use of microelectrodes (with radii less than 23.2 μm for δconv. = 150 μm) would be a promising tool, regardless of their inferior stabilities in high-temperature molten salts at this stage. These innovative findings offer insights into the impact of natural convection on mass transfer in molten salts that have not been previously revealed.

Radial Temperature Profile Measurements to Understand Mass Transfer in Rotating Packed Bed Distillation

Radial Temperature Profile Measurements to Understand Mass Transfer in Rotating Packed Bed Distillation

Post-processing of a lavender flowers solvent extract using supercritical CO2 fractionation

BackgroundSupercritical Fluid Extraction (SFE) was performed using an unconventional material, the solid extract of lavender flowers obtained by liquid solvent extraction and subsequent solvent elimination. MethodsSystematic extraction experiments were carried out at 8 MPa and 40 °C, and the extract was fractionated in semi-continuous mode in the SFE plant. To understand mass transfer phenomena driving the process, CO2 mass flow rates ranging between 0.60 and 1.50 kg/h were used, and yield vs. time curves were obtained. Significant findingsFractionation produced a cuticular waxes selective precipitation in the first separator and the floral fragrance in the second separator. The most abundant species in the extract were τ-cadinol (13%), lavandulol (10.5%), β-caryophyllene (10%), viridiflorene (8.5%), isocaryophyllene (6%), cedrenalol (4.5%), linalool (4%) and 1,8-cineol (4%). The fragrance contained no waxes, indicating that the fractionation was successful. At higher mass flow rates (from 0.90 to 1.50 kg/h), an asymptotic extraction yield of 5.2% w/w was obtained; whereas, at lower mass flow rates, the extraction yield was lower (2.3% w/w) since the vegetable bed was not completely wetted by the extraction fluid. The overall results indicated that an external mass transfer resistance controlled the process.

Mass transfer during surfactant-enhanced DNAPL remediation: Pore-scale experiments and new correlation

Surfactant-enhanced solubilization has been proven successful to remediate aquifers contaminated with non-aqueous phase liquids (DNAPLs). Understanding mass transfer from DNAPLs to the surfactant solution is highly important for improving remediation efficiency. However, the pore-scale mechanisms underlying the effect of surfactants on mass transfer behaviors have not been fully understood. Here we use microfluidic experiments to investigate the fundamental physical processes and quantify the impacts of surfactants on mass transfer rate at the pore scale. We find that surfactants can induce droplet breakup behaviors due to the interfacial disparity of mass transfer strength, resulting in the subsequent micro-movement of daughter blobs due to capillary force. Through image-based measurements, we find a significant inhibition of the mass transfer rates by surfactants at concentrations above the critical micelle concentration, and the inhibition becomes more pronounced as the concentration increases, which can be explained by an increase in stagnant film thickness. But the total mass transfer flux is improved because of the enhanced driving force caused by the surfactant-enhanced concentration gradient. In light of the observed physical processes and the behavior of mass transfer inhibition, we finally develop a new empirical model that explicitly considers the effects of surfactant concentration, DNAPL distribution, effective interface area, and flow rate to predict the mass transfer rate. This work provides pore-scale underpinnings of the mass transfer behaviors and a new mass transfer model considering the effect of surfactants, which improves the understanding of interphase mass transfer processes under the action of surfactants in subsurface hydrological and engineering systems.

PEPT validated CFD-DEM model of aspherical particle motion in a spouted bed

Computational Fluid Dynamics coupled with Discrete Element Method (CFD-DEM) has been used to model the dynamics of aspherical particles in a spouted bed. CFD-DEM results were rigorously validated against high-resolution, three-dimensional experimental data acquired using Positron Emission Particle Tracking (PEPT). A workflow facilitating the direct, detailed, quantitative comparison of experimental and numerical data, and thus validation of CFD-DEM simulations, was developed. Sensitivity analysis considering a wide range of particle properties and drag correlations was carried out. It was observed that the Young’s modulus, Poisson’s ratio, and restitution coefficient do not have a significant effect on the system’s dynamics across the range of parameters explored, and that Gidaspow’s correlation using equivalent intrinsic particle density is an appropriate choice for modelling drag forces. Analysis shows PEPT-validated CFD-DEM models quantitatively capture key features including particle circulation time, particle velocity and occupancy distributions, and the proportion of residence time in the bulk-bed and freeboard regions, all of which are crucial to understanding mass and heat transfer within the system. Our results also demonstrated that models using simple, spherical particles were – with suitably modified friction and drag models – capable of quantitatively reproducing the dynamics of a range of highly aspherical materials.

Effects of Radial and Circumferential Flows on Power Density Improvements of Tubular Solid Oxide Fuel Cells

Improving the power density of SOFC stacks will accelerate their integration into mobile applications. We developed a 3D Multiphysics model validated by experimental results from early studies to examine the effect of radial and circumferential flows on the power density improvements in a micro-tubular SOFC. The inserts were placed inside the fuel channel to generate flow in different directions. The effects of geometric parameters of these inserts on flow and mass transfer in the fuel channel and porous anode were analyzed. We demonstrate that the radial flow enables the fuel to penetrate directly into the porous anode, increasing the local fuel concentration and enhancing the fuel diffusion to the anode triple-phase boundaries. We found that the circumferential flow has a negligible effect on the diffusion process in the anode and on the increase in power density. The impact of local convective and diffusive mass transfer mechanisms on power density improvement is analyzed using the local Péclet number along the axial direction. Enlarging the radial velocity component perpendicular to the porous anode could effectively increase the power density of the micro-tubular SOFC by 37%. This study helps improve our understanding of mass transfer in fuel channels and helps build a foundation for SOFC channel designs and optimizations.

A New Alpine Metallogenic Model for the Pb-Ag Orogenic Deposits of Macôt-la Plagne and Peisey-Nancroix (Western Alps, France)

Understanding mass transfer associated with fluids circulation and deformation in the Alpine orogeny is often complex due to common multistage crystallization. For example, in two emblematic and historic Pb-Ag deposits of the French Alps, Macôt-la Plagne (MP) and Peisey-Nancroix (PN), a sedimentary or orogenic origin is still debated. To discriminate between the metallogenic models of the two deposits, an integrative methodology combining field, microstructural, mineralogical, thermobarometrical, and geochronological data was here applied for establishing detailed Pressure–Temperature–Time–Deformation (P-T-t-d) mineralization conditions. Both deposits are located in Permo-Triassic quartzite of the External Briançonnais domain along the Internal Briançonnais Front (Internal Western Alps). The ore mainly occurs as veins and disseminated textures containing galena, pyrite, and variable content of tetrahedrite–tennantite and chalcopyrite. Quartz porphyroclasts and sulfide microstructures indicate a dynamic recrystallization of the quartzite during the main fluid mineralization episode. Chlorites and K-white micas (phengite) chemical analysis and thermodynamic modeling from compositional maps indicate an onset of the mineralization at 280 °C, with a main precipitation stage at 315 ± 35 °C and 6.25 ± 0.75 kbar. In situ U-Pb dating on monazite, cogenetic with sulfides, gives ages around 35 Ma for both deposits. The integrative dataset converges for a cogenetic MP-PN Alpine Pb-Ag mineralization during deformation in relation to the thrusting of the “Nappe des Gypses” and the Internal Briançonnais at the metamorphic peak.

Gas-liquid interface influencing electronic structure of phenol based on molecular dynamics simulations and theoretical X-ray absorption spectroscopy

The study of atomic-scale molecular properties is vital for understanding mass transfer mechanisms and chemical reactions at the gas-liquid interface of plasma in contact with liquid. In this study, we conducted molecular dynamics simulations based on density functional theory to investigate the influences of the gas-liquid interface on the electronic structure of phenol. The probability distribution of the polar angles of phenol at the gas-liquid interface indicated that the OH group preferred to remain in the liquid phase, contrary to the aromatic ring that preferred to remain in the gaseous phase. The geometric configurations at various polar angles were extracted based on the probability distribution to evaluate the inner-shell X-ray absorption spectra (XAS) of phenol. Moreover, the chemical shifts of all carbon and oxygen atoms were obtained for the atomic-selected merit of XAS. As compared to the gaseous phase, the first transition energies from the O(1s) transition of phenol at the gas-liquid interface decreased by approximately 0.6380 ± 0.3273 eV. Furthermore, the gas-liquid interface disassociated the plane symmetric Cs group and significantly altered the oscillator strengths, thus converting forbidden transition to allowed transition. The data obtained in this study provide insightful guidance for interpreting the experimental XAS and influences of the gas-liquid interface on the molecular electronic structure of phenol.

In-situ plasmonic tracking oxygen evolution reveals multistage oxygen diffusion and accumulating inhibition

Understanding mass transfer processes concomitant with electrochemical conversion for gas evolution reactions at the electrode-electrolyte interface plays a key role in advancing renewable energy storage and conversion. However, due to the complicated diffusion behavior of gas at the dynamic catalytic interfaces, it is still a great challenge to accurately portray mass transfer of gas during electrocatalysis process. Here, we track the diffusion of dissolved oxygen on Cu nanostructured plasmonic interface, which reveals multistage oxygen diffusion behaviors, including premature oxygen accumulation, spontaneous diffusion and accelerated oxygen dissipation. This work uncovers an accumulating inhibition effect on oxygen evolution arising from interfacial dissolved oxygen. With these knowledges, we develop a programmable potential scan strategy to eliminate interfacial gas products, which alleviates the concentration polarization, releases accessible actives sites and promotes electrocatalytic performance. Our findings provide a direct observation of the interfacial mass transfer processes that governs the kinetics of gas-involved multiphases catalysis.

Investigating hydrate formation rate and the viscosity of hydrate slurries in water-dominant flow: Flowloop experiments and modelling

Water dominated flow is typically encountered in mature oil and gas fields after water breakthrough has occurred; gas hydrate formation in these systems is generally associated with a high risk of flowline blockage. With the move towards production of natural hydrate deposits as an abundant source of gas, understanding water dominated flow will become increasingly important, particularly as these systems inherently operate near or within the hydrate equilibrium region. In this work, we present an improved mass-transfer limited hydrate growth rate model, which includes the effect of hydrate slurry viscosification on formation. This is validated through several methane hydrate formation experiments employing a 10 mm ID flowloop operating at high water cut (100 vol% water).The model is based on understanding mass transfer limitations for hydrate slurry systems; the mass transfer coefficient itself was estimated by the small eddy cell model and considers changes in the viscosity and diffusion coefficient due to an increase in hydrate volume fraction. Further, differential effective medium theory was employed to predict the viscosity of the hydrate slurry. The gas-water interfacial area was directly estimated (without any correlations) by employing high quality images captured through an in-line camera instrumented on the flowloop. Experimental results obtained from the flowloop were used to validate the overall growth rate predictions of our model. Overall, this work offers a pathway to improve predictive capabilities for the coming generation of natural gas hydrate production, and to increase confidence in our ability to actively manage hydrate formation for water dominant systems.

Professor Daniel I.C. Wang: A Legacy of Education, Innovation, Publication, and Leadership.

Professor Daniel I.C. Wang: A Legacy of Education, Innovation, Publication, and Leadership.

Insight of organic molecule dissolution and diffusion in cross-linked polydimethylsiloxane using molecular simulation

Polymeric membranes have gained an immense importance for the pervaporation (PV) of biofuels. The PV performance is influenced by several complex elements and significant understanding is empirically fairly difficult. Furthermore, it is essential to specify membrane swelling in different solvents prior to the PV. A molecular dynamics simulation protocol was applied to examine the swelling of cross-linked PDMS membranes in 1-butanol, ethanol, acetone, and water, the dissolution of organic molecule in dilute aqueous solution in PDMS, the PV through these swollen membranes and dissolution rate of guest molecules in membranes. The agglomeration effects of water as well as organic molecules inside cross-linked PDMS membrane during sorption and diffusion processes were also investigated. The effects of predicted cross-linked PDMS on separation performance of membranes, interactions of the guest molecules on the swelling degree and diffusion coefficients follow the experimental trend. The predicted dissolution and diffusion, the diffusion selectivity and mean square displacement of different agglomerated forms of water and alcohol molecules through cross-linked membrane fairly matches the reported experimental results. Moreover, their reliability on the interaction between solvent and polymer, void size distribution and temperature were investigated. The micro level insights into the swelling of cross-linked polymer membranes, dissolution and diffusion of organic molecules and understanding of mass transfer were provided by simulation, which are valuable for making new membranes for high PV performance.

Experimental Studies of Lanthanides Electro-Codeposition in Molten Salt to Evaluate a 1-D Electrorefining Computer Model

Codeposition of elements is an important phenomenon in the analysis and understanding of mass transfer in electrorefining of pyroprocessing. This study investigated the codeposition of lanthanides in molten salt. Mass transport experiments were conducted to examine the accuracy of the 1D electrorefining model, ERAD. Three lanthanides (La, Ce, and Gd) were selected because their standard reduction potentials are close to each other which facilitates codeposition. For the electrodeposition experiments, six electrochemical cells were used with varying ratios of lanthanides and the electrode potential ranging from 0.00 V to 0.15 V. This controlled the codeposition environment. The resulting electrodeposits were analyzed by ICP-OES and compared with the simulation results from ERAD. The ERAD input parameters were determined through electrochemical studies. Theoretical codeposition ratios were also analyzed using polarization curves. The study indicated that the current density of each element played a major role in its codeposition, as did thermodynamically determined reduction potentials. The overall results were comprehensively investigated and showed that ERAD can reasonably show the tendency of the codeposition results obtained from the experiments. With minor revision, it is expected that this 1D computer code could be effectively utilized for modeling the mass transport of the electrorefining process of pyroprocessing.

Analytical Modeling and Computer Simulation of Heat Transfer Phenomena during Hydrothermal Processing Using SOLIDWORKS<sup>®</sup>

Mathematical modeling of unit operations especially in biomaterials processing plays an important part in understanding simultaneous heat and mass transfer and fluid flow phenomena. Hydrothermal/supercritical processes are one such process which utilizes high temperature and pressure to synthesize materials for varied applications. The present study constitutes development of a model incorporating all standard transport equations and transient conditions to predict the behavior of process and thus materials upon heating to high temperature in an enclosed composite (Steel and Teflon (PFA) vessel. Commercial software package SOLIDWORKS® is employed to simulate and output is presented as animations after post-processing. Results yield very useful data and information about process; materials of construction and materials being processed which helps in optimization.

Understanding Mass Transfer Directions via Data-Driven Models with Application to Mobile Phone Data

The aim of this paper is to solve an inverse problem which regards a mass moving in a bounded domain. We assume that the mass moves following an unknown velocity field and that the evolution of the mass density can be described by a partial differential equation, which is also unknown. The input data of the problems are given by some snapshots of the mass distribution at certain times, while the sought output is the velocity field that drives the mass along its displacement. To this aim, we put in place an algorithm based on the combination of two methods: first, we use the dynamic mode decomposition to create a mathematical model describing the mass transfer; second, we use the notion of Wasserstein distance (also known as earth mover's distance) to reconstruct the underlying velocity field that is responsible for the displacement. Finally, we consider a real-life application: the algorithm is employed to study the travel flows of people in large populated areas using, as input data, density profiles (i.e., the spatial distribution) of people in given areas at different time instants. These kinds of data are provided by the Italian telecommunication company TIM and are derived by mobile phone usage.

Characterization of interface properties of fluids by evaporation of a capillary bridge.

The surface properties between two non-miscible fluids are key elements to understand mass transfer, chemistry and bio-chemistry at interfaces. In this paper, surface properties are investigated in evaporating and non-evaporating conditions. A capillary bridge between two large plates (similar to a Hele-Shaw cell) is considered. The temporal evolution of surface forces and mass transfers due to evaporation of the liquid are measured. The force depends on surface properties of the substrate. It is adhesive in the wetting case and repulsive in the non-wetting case. The force is also shown to depend linearly on the volume of the capillary bridge F ∝ V0 and inversely to the height of the bridge. Modelling is performed to characterize both surface force and evaporation properties of the capillary bridge. The evaporation is shown to be diffusion driven and is decoupled from the bridge mechanics.

Process intensification in catalytic wet air oxidation of phenol via coupling gas‐liquid microdispersion with trickle bed reactors

AbstractIntensified trickle bed reactors were developed for catalytic wet air oxidation (CWAO) of phenol, by generating microbubbles before gas/liquid fluid flows along catalyst packed‐beds. By coupling gas‐liquid microdispersion module, phenol disappearance rate significantly increases under the same operating conditions and phenol conversion reaches 92% in 22 seconds at 160°C and 1000 kPa. Effects of operating conditions were studied systematically and results demonstrated characteristics of high‐interaction regime at low Reynolds number. Comparison of effects among mass transfer and reaction steps shows CWAO reaction is controlled by resistance to liquid‐solid mass transfer of phenol in most cases, while gas‐liquid mass‐transfer‐resistance is ignorable. A dimensionless correlation, Sh = 2.29φ−0.91(ReL + ReG)0.04, was established, by considering influences of liquid film thickness and fluid flow situations on liquid‐solid mass transfer coefficient in microbubble‐in‐liquid/catalyst‐particle system. The study would provide an effective method for intensifying CWAO and other liquid‐solid‐mass‐transfer‐resistance‐controlled gas/liquid/solid catalytic reactions and help understand mass transfer mechanism in new gas/liquid/solid system.

Anhydrite solubility in low-density hydrothermal fluids: Experimental measurements and thermodynamic calculations

Thermodynamic predictions of fluid-mineral equilibria significantly expand our ability to test hypotheses regarding mass and heat transfer in geological systems. In many cases, successful development of thermodynamic models relies heavily on experimental measurements. A dearth of experimental data in low-density hydrothermal fluids has prevented calculation of fluid-mineral equilibria at the most extreme temperature-pressure conditions associated with mid-ocean ridge hydrothermal systems. This study compares newly attained anhydrite solubility measurements in low-density NaCl-H2O fluids (410 °C, 25–32 MPa and 450 °C, 36.3–50 MPa) with novel thermodynamic calculations. To address the lack of equilibrium constants at the precise temperature-pressure conditions of the experiments, data are extrapolated from reference conditions as a linear function of the logarithm of water density. Several solubility calculations are performed that vary in the choice of aqueous speciation and activity coefficient model. There is overall good agreement between experimental observations and thermodynamic predictions, indicating the potential for accurate assessment of fluid-mineral equilibria in low-density fluids. However, speciation calculations are non-unique, highlighting uncertainties in aqueous speciation and calculation of activity coefficients that will require further examination. This study represents an important first step in increasing the temperature-pressure conditions over which thermodynamic calculations of fluid-mineral equilibria are possible, with important implications for understanding mass and heat transfer in submarine hydrothermal systems.

Numerical Modeling of Liquid–Liquid Mass Transfer and the Influence of Mixing in Gas-Stirred Ladles

Ladle refining plays a key role in the steelmaking process. During the refining, a bubbly gas stream is used for mixing and to enhance the rate of removal of impurities from the molten steel. A numerical model has been developed to understand mass transfer and mixing behavior in a three-phase gas-stirred ladle. A two-resistance approach was used for the liquid–liquid mass transfer, while the mass transfer coefficient was determined using the Small Eddy theory. The model was validated with experimental data, obtained from a water–oil physical model simulating an industrial ladle with a scale factor of 1/17, valid for axisymmetric gas injection. Three variables were included to study the mass transfer behavior, namely gas flow rate, Q, oil (slag) thickness, h, and oil (slag) viscosity, $$ \mu_{\text{o}} $$ . The gas flow rate ranged from 2.85 L/min to 8.56 L/min to meet industrial operating conditions. It was found that: (1) the volumetric mass transfer coefficient (ka) increases when the gas flow rate (Q) increases; and (2) increasing slag (oil) thickness has a positive influence on mass transfer as it considerably increases the interfacial area and promotes turbulence at the interface. At this range of gas flow rate, the effect of slag (oil) viscosity is limited. A general correlation was established: $$ {\text{ka}} = 0.058Q^{0.459} h^{0.612} $$ . Mixing time was studied within the same flow rate range to observe its influence on the mass transfer. Mixing in the ladle is accomplished in a much shorter time than interphase mass transfer, specifically by two orders of magnitude, which indicates that mass transfer is the rate-limiting step.