Inter-phase Transfer Research Articles

Boosting Interfacial Ion Transfer in Potassium-Ion Batteries via Synergy Between Nanostructured Bi@NC Bulk Anode and Electrolyte.

Using high-capacity alloy-type anodes can greatly advance potassium-ion batteries (PIBs). However, the primary limits are unstable solid electrolyte interphase (SEI) and tough interfacial ion transfer associated with large-size K+ during electrochemical (de)alloy reactions. Here, we achieve excellent energy storage performance of PIBs via the synergy between a nanostructured Bi@N-doped carbon (Bi@NC) bulk anode and a KPF6-dimethoxyethane (DME) electrolyte. The Bi@NC material with a high tap density of 3.81 g cm-3 is prepared by simply pyrolyzing a commercial Bi salt yet affords a favorable nano/microstructure consisting of Bi nanograins confined in 3D ultrathin N-doped carbon shells, facilitating electron/ion transport and structural integrity. Detailed impedance spectroscopy investigation unveils that K+ transport through SEI at the Bi@NC anode, rather than the desolvation of K+, dominates the interfacial K+ transfer. More importantly, spectroscopic and microscopic characterizations provide clear evidence that the interplay between Bi@NC anode and optimized KPF6-DME electrolyte can produce a unique SEI layer containing Bi3+-solvent complex that enables the activation energy of interfacial K+ transfer as low as 25.9 kJ mol-1, thereby ultrafast charge transfer at Bi@NC. Consequently, the Bi@NC anode in half cells achieves exceptional rate capability (206 mAh g-1 or 784 mAh cm-3 at 120C) accompanied by high specific capacity (331 mAh g-1 or 1261 mAh cm-3) and long cycle life (running 1400 cycles at 15C with a tiny capacity fading rate of 0.013% per cycle). Moreover, the Bi@NC anode and KPF6-DME electrolyte are also compatible with a potassium Prussian blue cathode and assembled full PIBs achieve stable cyclability (87.3% capacity retention after 100 cycles at 2.5C) and excellent rate performance (65.1% capacity retention upon increasing rates from 1 to 20C).

Study on the characteristic of boiling expansion process of superheated LPG and its vapor cloud explosion

Liquefied Petroleum Gas (LPG) is stored in liquid form under high pressure conditions. Once the tank fails, LPG will leak in gaseous form hundreds of times its liquid volume. LPG inside the storage tank will undergo a violent boiling process leading to pressure rebound in the tank. In serious cases, boiling liquid expanding vapor explosion (BLEVE) will happen. And the leaking LPG will mix with air to form a flammable vapor cloud that can explode. Therefore, it is necessary to study the violent boiling process inside the LPG vessel after rupture, the leakage diffusion process in the surrounding environment and the vapor cloud explosion process. In this paper, CFD software FLUENT was used to conduct numerical simulation of the inter-phase transfer of mass and heat inside the vessel when LPG leakage happens, and the transient pressure inside the vessel was analyzed. The results obtained from the simulation are in good agreement with the experimental data under the same conditions which provides the validity verification of the phase transition during boiling process of LPG. A three-dimensional numerical model of LPG release process after the failure of a cylindrical vessel was established. The realizable k-ε model and eddy-dissipation model were used to simulate the explosion process of LPG after the release. The pressure, temperature and thermal radiation distribution of the explosion flow field were obtained so the damage range of LPG after explosion can be analyzed, which has certain guiding significance for the risk assessment of LPG.

Voltammetric studies of glutathione transfer across arrays of liquid-liquid microinterfaces for sensing applications.

The simple and facilitated transfer of tripeptide glutathione across the water/2-nitrophenyl octhyl ether interface was studied via cyclic voltammetry at interface between two immiscible electrolyte solutions (ITIES). The micro-perforated membrane prepared with a laser with a femtosecond pulse was used for mechanical stabilization of the interface. The method of cyclic voltammetry was used to study the passive and facilitated interfacial transfer of glutathione and its complex with the crown ether dibenzo-18-crown-6 (DB18C6).The glutathione mass transfer mechanism was established and substantiated, the diffusion coefficients, thermodynamic characteristics of interphase transfer and the constant of complexation of the glutathione by DB18C6 were determined. Square wave voltammetry based on facilitated transfer was used for more accurate and sensitive determination of glutathione low detection limit (0.8μM) with wide linear dynamic range (from 3.0 to 80μM) was reached. The influence of various potentially interfering ions on the voltammetric determination of glutathione has also been investigated. The method developed was applied to determine glutathione in aqueous solutions and malt extract.

Numerical investigation of aqueous graphene nanofluid ice slurry passing through a horizontal circular pipe: Heat transfer and fluid flow characteristics

Ice slurry is an attractive phase-change cold storage medium that offers excellent thermal performance, thus rendering it a good prospect for applications in renewable energy storage, power peak-cutting, and valley filling. In this study, a computational fluid dynamic (CFD) numerical framework is employed based on the particle dynamics approach of an Euler-Euler two-fluid model coupling interphase transfer mechanisms. Thermal transport of a water-based graphene nanofluid ice slurry moving in the turbulent regime in a horizontal circular straight pipe is simulated and described. During the flow, the ice crystals tend to cluster on the top of the horizontal pipe, according to the findings, while uniformity of the crystal size distribution improves with an increase of velocity and the ice packing factor (IPF). Under the conditions of inlet IPF of 10% and heat flux q = 8000 (W m−2), the heat transfer coefficient on the heated section wall is increased by around 9% and 15%, respectively, as compared to pure water ice slurry and water. However, since the nanofluids have a higher viscosity than water, the pressure drop of nanofluid ice slurry is about 5% higher than that of pure water ice slurry in the same working environment.

Analysis of Ozonation Processes Using Coupled Modeling of Fluid Dynamics, Mass Transfer, and Chemical Reaction Kinetics.

The efficacy of oxidation of recalcitrant organic contaminants in municipal and industrial wastewaters by ozonation is influenced by chemical reaction kinetics and hydrodynamics within a reactor. A 3D computational fluid dynamics (CFD) model incorporating both multiphase flow and reaction kinetics describing ozone decay, hydroxyl radical (•OH) generation, and organic oxidation was developed to simulate the performance of continuous flow ozonation reactors. Formate was selected as the target organic in this study due to its well-understood oxidation pathway. Simulation results revealed that the dissolved ozone concentration in the reactor is controlled by rates of O3(g) interphase transfer and ozone self-decay. Simulations of the effect of various operating conditions showed that the reaction stoichiometric constraints between formate and ozone were reached; however, complete utilization of gas phase ozone was hard to achieve due to the low ozone interphase mass transfer rate. Increasing the O3(g) concentration leads to an increase in the formate removal rate by ∼5% due to an enhancement in the rate of O3(g) interphase mass transfer. The CFD model adequately describes the mass transfer occurring in the two-phase flow system and confirms that O3(g) interphase mass transfer is the rate-limiting step in contaminant degradation. The model can be used to optimize the ozone reactor design for improved contaminant degradation and ozonation efficiency.

Practicality of methyl acetate as a co-solvent for fast charging Na-ion battery electrolytes

Rapid research and technological improvements on Na-ion batteries (NIBs) are making them the most practicable complementary device for lithium-ion batteries (LIBs). Moreover, the high Na-ion diffusion kinetics offers several fast charging electrode materials that are attractive for high power applications. Lowering interphase and charge transfer resistances via innovative electrolytes design, while not scarifying lifetime, is however essential to secure such applications. Herein, we report the effect of low viscous ester based co-solvents in improving the conductivity of Na-ion based electrolyte. Our new electrolyte formulation shows excellent power capability charging the 18650 cell to 84% state of charge (SOC) within ∼10 min. Additionally it improved low temperature cyclability, but with a slightly reduced high temperature performance against our co-solvent free electrolyte. We believe that the guideline taken here will pave the way towards finding a better compromise between ultrafast charging and high temperature applications for reaching optimum performance.

Linear and Non-Linear Stability Analysis for Thermal Convection in A Bidispersive Porous Medium with Thermal Non-Equilibrium Effects

The linear instability and nonlinear stability analyses are performed for the model of bidispersive local thermal non-equilibrium flow. The effect of local thermal non-equilibrium on the onset of convection in a bidispersive porous medium of Darcy type is investigated. The temperatures in the macropores and micropores are allowed to be different. The effects of various interaction parameters on the stability of the system are discussed. In particular, the effects of the porosity modified conductivity ratio parameters, and , with the inter-phase momentum transfer parameters and, on the onset of thermal Convection are also considered. Furthermore, the nonlinear stability boundary is found to be below the linear instability threshold. The numerical results are presented for free-free boundary conditions.

수직 원관에서의 메탄의 포화 유동 비등에 관한 수치해석적 연구

In this study, a numerical study on saturated flow boiling of methane is carried out in a smooth vertical pipe. The pipe has a diameter of 8 mm and length 1 m. The simulation is performed under the condition of mass flux of 52.36-150.31 kg/㎡s, heat flux range of 7,950.7-31,858.9 W/㎡, and outlet pressure of 0.7 MPa. The analysis for saturated flow boiling is implemented with taking into account the phase change process, wall boiling and inter-phase momentum transfer models. Simulation results are compared with the theoretical values and experimental results found in the literature. According to the simulation results, the vapor quality shown in the simulation is lower than that predicted by the theoretical values. However, the variation of the vapor quality with respect to heat flux shows similar trend to the theoretical value. The heat transfer coefficient is mainly dependent on the heat flux and not significantly affected by the mass flux. This means that the main mechanism of saturated flow boiling heat transfer is nucleate boiling.

A meshless Lagrangian particle-based porosity formulation for under-resolved generalised finite difference-DEM coupling in fluidised beds

An under-resolved coupling strategy for the discrete element method (DEM) and the weakly compressible (WC) generalised finite difference method (GFD) is proposed. A novel filtering technique is proposed that allows for the recovery of a continuum porosity field in an arbitrary domain from DEM information. This allows fine spherical DEM particles to be treated in an under-resolved fashion using well-established drag relations for dynamic porous media to determine the fluid forces acting on them. To handle the momentum balance between phases, an inter-phase momentum transfer scheme is proposed as well. Verification and validation of the coupling strategy is performed. This includes comparisons to a fully-resolved WCGFD scheme when the associated computational cost allows for it. This strategy's benefits are seen when simulating a fluidised bed with an evolving fluid domain. It is shown that both under-resolved and fully-resolved dynamic information can seamlessly be treated with this scheme.

Improving inter-phase charge transfer via defect passivation for efficient Quasi-2D (BA)2(FA)8Pb9I28 perovskite solar cells

There has been extensive investigation into phase orientation and phase distribution for improving charge transfer in 2D perovskites-based PSCs, but very few reports have focused on the enhancement of inter-phase charge transfer by passivation. In this work, a synergetic strategy is developed by introducing hydrochloric acid and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as additives to modulate phase distribution and passivate defects in (BA)2(FA)n−1PbnI3n+1 (n = 9) quasi-2D perovskite films. In this process, perovskite films with suppressed phase segregation and PCBM molecules coated along the grain boundaries are obtained. PCBM is found to reduce the trap density by compensating defects, which accelerate inter-phase charge transfer and restrain nonradiative recombination, resulting in improved performance of quasi-2D PSCs. As a consequence, a high PCE of 15.01% with negligible hysteresis for quasi-2D PSCs is achieved.

Extinction of incident hydrogen/air detonation in fine water sprays

Two-dimensional numerical simulations with Eulerian–Lagrangian method are conducted to study propagation and extinction of stoichiometric hydrogen/air detonations in fine water sprays. Parameterized by water mass loading and droplet size, a detonation extinction map is predicted. Detonation extinction occurs with larger mass loading and/or smaller droplet size. General features of water droplets and local detonation frontal structures are well captured. Numerical soot foils are used to characterize the influence of mass loading and droplet size on the detonation wave. The results also show that the detonation cell size increases with increased mass loading or decreased droplet size. Analysis on unsteady detonation extinction process is performed with the evolutions of detonation frontal structure, spatial distribution of thermochemical variables, and interphase transfer rates (mass, energy, and momentum). Moreover, the chemical explosive mode analysis reveals that for stable detonation, thermal runaway dominates behind the Mach stem, while chemical propensities of autoignition and thermal runaway appear alternately behind the incident wave. When the induction zone length increases as the reaction front (RF) and shock front (SF) are decoupled, localized burned pockets surrounded by the autoignition chemical explosive mixture can be observed. In addition, the interactions between detonation wave and water droplets demonstrate that the energy and momentum transfer have more direct interaction with SF and RF than the mass transfer. The interphase transfer rates increase with the water mass loading. Under the same mass loading, the smaller the droplet size, the larger the interphase transfer rates. However, the size of fine water droplets has a limited influence on the interphase momentum exchange. Moreover, high energy and mass transfer rates are observed at the onset of detonation extinction, and they gradually decrease when the reaction and detonation fronts are decoupled.

CFD simulation of continuous non-catalytic gas–solid reaction with uniform particle size distribution

Non-catalytic fluidized bed reactors (FBRs) have been utilized in various industries. In this study, a computational fluid dynamics (CFD) model, involving a combination of transport processes, intrinsic kinetics, and flow structure, is established and validated to investigate the continuous gas–solid reaction. The simulated results indicate that the solid conversion rate is determined by the solid reaction rate and the mass flow rate. Traditional interphase transfer models have been proven to overestimate the momentum and mass transfer coefficients, and cause deviations in the predicted results. The gas–solid reaction rate, obtained from the structure-based model, depends on reaction time and bed position owing to the variations in the overall reaction rate constant and the non-uniform gas–solid flow structure. The period longer than twice the time required for complete conversion of particle has little effect on the solid conversion process, because of the higher internal diffusion resistance and the wider residence time distribution of particles. The mass transfer during the bubble phase also contributes to the reaction process. Therefore, this study provides a methodology for the CFD simulation of continuous non-catalytic FBRs.

Technologies for Chemical Utilization of Imitation Recipes and Components of Special Products on a Chemical Basis

There are problems of destruction of educational and simulation formulations and components of special chemical-based products and degassing formulations based on organic solvents. Their solution requires the search for cost-effective and environmentally friendly solutions and approaches to their disposal, especially paying attention to the fact that it is practically impossible to completely free the components of products from toxic chemicals. In turn, it is necessary to minimize toxic and unpleasant-smelling emissions into the atmosphere during neutralization and destruction. The purpose of the work is to propose chemical methods for neutralizing and disposing of toxic substances and foul-smelling compounds during the disposal of educational and simulation formulations and special tools. To neutralize compositions based on odorant substances, it is advisable to use compounds of oxidizing-chlorinating action, quaternary ammonium bases and a co-catalyst. The role of each of the used components of the formulation is established. Sodium hypochlorite is an oxidizer, «Katamin AB» is an interphase transfer catalyst that ensures the transfer of anion from the aqueous phase to the organic one, methanesulfonic acid is a co-catalyst that ensures the reaction in both the aqueous and organic phases. The optimal quantitative and qualitative composition of the degassing formulation for neutralizing odorants is considered. The composition of the formulation should include the following components, expressed in % by weight: an aqueous solution of sodium hypochlorite (5%) «Whiteness» – 99.0; dimethylalkyl(C 8 -C 18 ) benzylammonium chloride «Katamin AB» – 0.5; methanesulfonic acid – 0.5.

Development of a novel two-phase flow solver for nuclear reactor analysis: algorithms, verification and implementation in OpenFOAM

A porous medium-based representation of nuclear reactors and complex engineering systems more in general can significantly reduce simulation and modelling costs, while preserving a reasonable degree of accuracy via regime map-based correlations for modelling physical interactions. This paper presents a segregated algorithm for the simulation of dispersed two phase flows in such systems treated as porous media in an Eulerian framework. The global algorithm pertaining to the coupling between the mass, momentum and energy conservation equations solution is discussed and implemented via the finite volume OpenFOAM programming library. In the context of pressure–velocity coupling, a novel implementation of the Partial Elimination Algorithm for the treatment of the inter-phase momentum transfer term is developed. It is found to perform better than existing implementations for a number of cases with important momentum coupling between phases. A conclusive verification of the overall solution algorithm is performed with the Method of Manufactured Solutions and order-of-accuracy testing. From an implementation perspective, the performance of the algorithm in parallel strong scaling up to 4096 cores is assessed and proves to be in line with OpenFOAM-based code standards.

Assessment of one-dimensional models used in the simulation of gas-liquid flows in vertical degassing columns

The present research aims to assess and analyze one-dimensional two-fluid models used in simulating gas-liquid dynamics and interphase transfers in degassing columns. The assessment of two-fluid models is based on benchmark measurement data carried out over a long period of time, both on dissolved gas concentrations in Lake Nyos at different depths and on the gas-liquid jet heights at the outlet of the degassing columns installed from 2001. The results of the numerical simulations with different two-fluid models were compared and their confrontation with the experimental data were discussed with respect to the sensitivity of the models to the different closures and hypotheses. The numerical analysis has led to a benchmark assessment of mono-dimensional two-fluid models in their capacity to account for the complexities associated with the different couplings between the dynamic aspects and interphase mass transfer phenomena that occur in degassing columns.

Efficient projection kernels for discontinuous Galerkin simulations of disperse multiphase flows on arbitrary curved elements

In this work, we develop projection kernels for Euler-Lagrange point-particle simulations of disperse multiphase flows on arbitrary curved elements. These kernels are employed in a high-order discontinuous Galerkin framework for projecting the action of the particles to the Eulerian mesh. Instead of commonly used isotropic kernels, such as a Gaussian-type kernel, we construct an anisotropic polynomial-based smoothing function that preserves the compactness of the discontinuous Galerkin method on high-aspect-ratio elements and maintains an acceptable computational cost. At the same time, it mitigates inaccuracies associated with larger particles and numerical instabilities arising from the Dirac delta function and low-order kernels. Specifically, the geometric mapping of a physical element to the reference element is exploited to construct a kernel that is elliptical in 2D and ellipsoidal in 3D. We also develop a strategy to conserve interphase transfer near boundaries, particularly on curved elements. This strategy employs a high-order polynomial approximation to appropriately rescale the interphase source terms in an efficient manner. The compatibility of the proposed methodology with different types of meshes is investigated. We then apply it to a number of particle-laden flow configurations, including supersonic dusty flow over a flat plate, moving shocks interacting with clouds of particles, and hypersonic dusty flows over blunt bodies.

Effect of Stefan flow on the drag force in flow past random arrays of spheres

Stefan flow is a mass flow perpendicular to the particle surface induced by the reaction or component diffusion occurring inside particles. It significantly affects the interphase transfer process in gas–solid reacting flows. In this work, a second-order immersed boundary-lattice Boltzmann method (IB-LBM) is adopted for analyzing the influence of Stefan flow on the drag force in flows past fixed random arrays of spherical particles. The effect of Stefan flow is introduced by assigning specific fluid velocities at Lagrangian markers on the sphere surface. The simulation results show that the drag force exerting on particles decreases as the Stefan Reynolds number increases. The drag force reduction caused by Stefan flow is weakened as the solid volume fraction increases. This is because the thick boundary layer caused by Stefan flow on each particle is suppressed by Stefan flow from their neighboring particles. Based on the simulation results, a novel drag correction coefficient is developed, which considers the joint influence of the Stefan Reynolds number, particle Reynolds number and solid volume fraction.

A review on numerical modelling of flashing flow with application to nuclear safety analysis

The flashing flow is a relevant multiphase phenomenon in many technical applications including nuclear safety analysis, which has been the subject of intense research for several decades. Numerical studies have evolved from one-dimensional to multi-dimensional. A variety of methods has been proposed, while a broad consensus does not exist yet. The present work aims to present an overview of available models and assess their limitations and perspectives by conducting an extensive literature survey. The final focus was put on recent progresses of computational fluid dynamics simulations. Some consensus on modelling interfacial slip, phase change mechanism and bubble size is identified. Since flashing scenarios often accompanying with high void fraction and broad bubble size range, a poly-disperse two-fluid model is recommended. Thermal phase change model is superior to pressure phase change, relaxation and equilibrium models for practical flashing problems, however incorporation of pressure effects is desirable. Major challenges comprise improving closure models for interphase transfer, bubble dynamics processes, interfacial area as well two-phase turbulence. For this purpose, high-resolution high quality experimental data are important, which are lacking in many cases. Considering that heterogeneous gas structures often exist in flashing flows, multi-field approaches able to handle different shapes of gas-liquid interface and including the shape effect in closure models are recommended for further study.

Numerical modelling and investigation of microwave heating and boiling phenomena in binary liquid mixtures using OpenFOAM

To understand Microwave (MW) heating and boiling of binary liquid mixtures, a new multiphysics model was developed. The new model solves Maxwell's equations for the electromagnetic field distribution. Concerning the coupled dispersed and segregated vapor-liquid flow during MW boiling, it was modelled based on a hybrid Two-Fluid-Volume-of-Fluid method. As for the modelling of heat and mass transfer, Two-fluid energy and species conservation equations were solved, with new dispersed and segregated interphase heat and mass transfer closures formulated using appropriate interface jump conditions combined with vapor-liquid equilibrium relations. The new model showed reasonably good agreement with the experimental data. The capability of the model to simulate MW heating, superheating, superboiling, and interphase transfer phenomena in methanol-water mixture (heated in a multi-mode MW cavity) was demonstrated, and the associated physics was investigated. The simulation results revealed three underlying mechanisms that lead to superheating (up to 9.5°C at 300 W) in binary mixtures, namely limited bubble nucleation, inefficient mixing, and higher interfacial saturation temperature compared to that in bulk liquid (about 2°Chigher). Besides, the results also showed that the increase of heating time mainly increases the amount of superheat rather than the superheat temperature. It was also found that MW superheating tends to reduce the mass fraction of the lighter component in the released vapor (by up to 2%). In the subsequent study, the effects of several operating conditions were examined. The simulation results generally showed that higher liquid methanol concentration, higher MW power, rectangular sample geometry, and smaller sample volume lead to higher superheat intensity, but poorer methanol concentration in the vapor released. The new model and findings could open up new avenues for the design and improvement of processes such as MW-assisted synthesis, extraction, biodiesel production, and distillation.

Sensitivity of macroscopic transport calculations to uncertain microscale relationships during metal alloy solidification

The formation of grains during metallic solidification results in a multiphase system consisting of many moving interfaces. Models have been formulated in terms of variables describing the microscopic details of interface motion during solidification, but the computational cost prohibits their extension to the length scale of industrial castings. For this reason, macroscopic transport equations are mathematically formulated using averaging methods to replace the instantaneous description of interfaces. The most common approach is the volume-averaged, Eulerian approach relying on both the proper derivation of macroscopic field equations as well as uncertain interfacial conditions used to account for the average behavior of the interphase transfer occurring on the sub-grid length scale. In this work, common models used to describe the microsegregation occurring during solidification are evaluated in terms of the uncertainty of parametric inputs invoked in each model and their effect on macroscale predictions. We show that the qualitative macroscale predictions are not significantly changed by using more sophisticated microsegregation models, however significant uncertainty in input parameters used to describe the unresolved sub-grid interface is accumulated. Therefore, the use of simplified models is preferred until the uncertainty in model inputs can be reduced.