Volume Fraction Of Solid Phase Research Articles

Two-Fluid and Discrete Population Balance Model for Simulation of Batch Sedimentation Relevant to Plutonium Reconversion

There are widespread occurrence and application of solid-liquid sedimentation processes among different industries. Therefore, it becomes important to understand the hydrodynamic inside the process equipment and particle agglomeration characteristics. In the present work, solid-liquid sedimentation is analyzed, which will be helpful for the design of continuous process equipment in plutonium (Pu) reconversion. Experiments were carried out in a batch settler to understand solid sedimentation in suspension in terms of varying the overall solid fractions. Euler-Euler two-fluid simulations were performed to investigate the local and overall solid phase volume fraction distributions, position of the active interface (AI) (settling curve), axial solid phase velocity, and pressure distributions during settling, and selected data were compared with the measured data. Further, the discrete population balance model (PBM) with different agglomeration kernels was used with the two-fluid computational fluid dynamics (CFD) model to understand and further improve predictions in terms of the AI position. The variation in number density of the different particles in the settler with time was investigated. The predicted results show that agglomeration is dominant during the sedimentation process and application of the discrete PBM with the CFD model enhances the predictive capability in comparison with the predictions obtained from only the two-fluid model. The results reported using CFD+PBM will aid in the design of continuous process equipment (thickener/precipitator) for Pu reconversion.

Ni agglomeration and performance degradation of solid oxide fuel cell: A model-based quantitative study and microstructure optimization

Nickel agglomeration poses a noteworthy impediment to the commercialization of SOFCs. A comprehensive coupled degradation model is established, encompassing a Ni-particle coarsening model, microstructural parameters, effective mesoscopic parameters, and various transport processes (mass/momentum/heat/charge/multi-species transports), and chemical/electrochemical reactions. The initial anode microstructural parameters are optimized by the comprehensive model and response surface method (RSM). Single-factor analysis shows that within the initial Ni-particle diameter (dNi(t=0)) range of 0.6–0.9 μm, a particle size ratio (R) of 1.0–1.5 between YSZ-particle and Ni-particle, and a solid-phase volume fraction of Ni-particle (ψNi) ranging from 0.35 to 0.55, SOFC demonstrates high power density and a reduced degradation rate. Using the single-factor results, RSM is employed for -anode microstructure optimization, specifying: dNi(t=0) = 0.7 μm, R = 1.0, and ψNi = 0.49. Correspondingly, the average power density at 0.6 V (PD‾0.6V) reaches 2828.5 W/m2, with a degradation rate (Vde) off 0.441 %/1000 h. In comparison to original microstructure parameters (dNi(t=0) = 0.6 μm, R = 1.0, ψNi = 0.4), the optimal SOFC exhibits a remarkable enhancement in electrical performance and durability, with an 11.9 % increase in PD‾0.6V and a 69 % reduction in Vde. The integration of the comprehensive model and RSM presents a promising strategy for predicting performance, refining operation condition, and optimizing electrode microstructure for long-term operating SOFC.

A pore-level 3D lattice Boltzmann simulation of mass transport and reaction in catalytic particles used for methane synthesis

Three-dimensional lattice Boltzmann (LB) simulations were carried out to investigate the mass transport and reaction inside and around catalytic porous particles used in fluidized beds for the synthesis of methane from biogas (H2/CO mixtures). The 3D internal porous structure of a real particle with a size ∼200 μm was assessed with Synchrotron-based X-ray tomography (XTM). Pore-resolved simulations with a suitable LB model for catalytic reactions in microflows revealed that the preferential diffusion of H2 and the resulting inability of CO to penetrate deep inside the pores led to segregated distributions of the two species, hindering reaction in the downstream parts of the particle and rendering CO the deficient reactant. The implications for practical fluidized beds are that, for specific bed zones with a high dense-phase (solid-phase) volume fraction and a predominant flow direction, CO starvation may occur and may thus limit the methane yields. Subsequent parametric studies of spherical particles with a diameter 2R=150 μm and an artificially generated porosity allowed comparisons of LB results with radially symmetric analytical continuum-model solutions. The LB simulations revealed appreciable angular variations in the CO concentration at the external surface (r=R) and the outer layers of particle, especially at the higher investigated Damköhler numbers, which were however diminished as the core of the particle (r→0) was approached. The large angular variations, in conjunction with the skewed CO distributions towards their lower values, led to LB-computed particle effectiveness factors ∼30% lower than the corresponding analytical solutions.

Study on flow and heat transfer characteristics of salt solution ice slurry

As a phase change material, ice slurry allows the storage of thermal energy in the form of latent heat. This has great advantages in terms of reducing energy consumption and environmental protection, and is being widely used. In this study, based on the Eulerian-Eulerian CFD model and the Population Balance Model (PBM), the flow and heat transfer characteristic of salt solution ice slurry was simulation studied, which included the pressure drop, friction coefficient, volume fraction, distribution of ice crystals and local heat transfer coefficient during the flow and solidification of salt solution ice slurry in different conditions. And the experimental system is set up to verify the results of the model and analyze the variation rules of these parameters. The results showed that in salt solutions with different concentrations, when the flow rate and solid phase volume fraction increase, the pressure drop and local heat transfer coefficient of the ice slurry will increase. The surface heat transfer coefficient reached to 2.5 × 103 W m-2 K-1, 2.9 × 103 W m-2 K-1, and 3.2 × 103 W m-2 K-1 when ice crystal volume fraction was 5 %, 10 %, and 15 %, respectively. The study will contribute to understanding of the changes in basic characteristics of salt solution slurry during the flow and phase transition processes.

Numerical simulations of suspensions of rigid spheres in shear-thinning viscoelastic fluids

In multiphase flows, accurately modeling the interaction between the liquid phase of complex fluids and a porous medium of solid spheres poses a fundamental challenge. The dynamics of moderately dense non-colloidal suspensions constituted by static random arrays of mono-disperse spherical particles in non-linear viscoelastic fluids is studied numerically. This numerical study consists of about 9000 different systems, in which the volume fraction ϕ (0.04≤ϕ≤0.2) of the dispersed solid phase, the Reynolds number Re(5≤Re≤50), the solvent viscosity ratio β(0.05≤β≤0.9), the Weissenberg number Wi(0.5≤Wi≤4), and the mobility parameter of the Giesekus model α (0.1≤α≤0.5) were varied to understand the particle's interactions with the viscoelastic suspending fluid. We aim to investigate the relationship between the volume fraction of the dispersed solid phase and the non-linear rheology of shear-thinning viscoelastic fluids with the normalized average drag force ⟨F⟩. In addition, by assessing the flow patterns predicted numerically, we were able to provide a characterization of the velocity and stress fields as a function of the simulation parameters.

Strategies to improve the thermal performance of solar collectors

Abstract The paper evaluates a passive method for heat transfer improvement in heat exchangers, which implies the use of nanofluids. All calculations were carried out with a constant volumetric flow rate. The study examines three fluids with 0–4 % volume concentrations of CuO, MgO, and Al2O3 particles. The results indicate an increase in the heat transfer coefficient with increasing temperature. An Al2O3 nanofluid (4 % concentration) contributed to the best thermal performance. The incorporation of a 4 % content of MgO yielded an augmentation in heat transfer ranging from 15 % to 22 %, whereas an analogous concentration of CuO led to a more substantial enhancement of 25 %. Notably, the introduction of nanoparticles of Al2O3 produces a remarkable augmentation in heat transfer performance, with potential improvements of up to 36 %. The Nusselt number increases with increasing particle volume fraction and Reynolds number, according to results obtained for several nanoparticles (Al2O3, CuO, SiO2, and ZnO) with volume percentages in the range of 1–4 % and nanoparticle diameters of 25–70 nm. For all nanofluids, the time-averaged Nusselt number rises with a solid phase volume fraction increase of less than 5 %.

Strategies to improve the thermal performance of solar collectors

Abstract The paper evaluates a passive method for heat transfer improvement in heat exchangers, which implies the use of nanofluids. All calculations were carried out with a constant volumetric flow rate. The study examines three fluids with 0–4 % volume concentrations of CuO, MgO, and Al2O3 particles. The results indicate an increase in the heat transfer coefficient with increasing temperature. An Al2O3 nanofluid (4 % concentration) contributed to the best thermal performance. The incorporation of a 4 % content of MgO yielded an augmentation in heat transfer ranging from 15 % to 22 %, whereas an analogous concentration of CuO led to a more substantial enhancement of 25 %. Notably, the introduction of nanoparticles of Al2O3 produces a remarkable augmentation in heat transfer performance, with potential improvements of up to 36 %. The Nusselt number increases with increasing particle volume fraction and Reynolds number, according to results obtained for several nanoparticles (Al2O3, CuO, SiO2, and ZnO) with volume percentages in the range of 1–4 % and nanoparticle diameters of 25–70 nm. For all nanofluids, the time-averaged Nusselt number rises with a solid phase volume fraction increase of less than 5 %.

Fluctuation analysis and spatial distribution model of particle concentration in a lab-scale scrubbing-cooling chamber

The motion and distribution of ash from coal gasification during the scrubbing and cooling process are crucial for revealing the fluid flow pattern and improving the efficiency of multiphase separation. Experimental measurements of the local solid holdup (εs) in the liquid pool of a laboratory-scale gas-liquid-solid three-phase scrubbing-cooling chamber were carried out using an optical fiber probe. The fluctuations of εs in time and frequency domains under different operating conditions were discussed. The axial and radial distribution of εs was quantitatively analyzed. The results showed that inter-particle collision and particle-fluid interaction are the key factors leading to a fluctuation in particle concentration. Axial uniformity of particle concentration can be quantified by solid-phase volume fraction, particle Reynolds number, Archimedes number, and Morton number; εs in different regions is expressed according to the degree of influence of bubble wake as a correlation equation consisting only of cross-sectional average solid holdup and dimensionless radial position; a dimensionless expression for εs concerning operating conditions was established.

Research on the thermo-electrochemical behavior during the electrodeposition process of lithium metal battery

Lithium metal batteries (LMBs) are promising renewable energy storage device with higher energy density. During charging/discharging, the electrodeposition or dendrite growth on surface of Li electrode and temperature influence thermo-electrochemical behaviors in LMBs greatly. Coupling electrochemical reaction kinetic equations and thermal relations in electrode, as well as diffusion migrating equations of Li+ ion in electrolyte is employed to investigate the effects of temperature, charging current density, volume fraction of active solid and Li concentration in positive electrode, as well as salt concentration in electrolyte on the entropy production relating to power consumption and Joule heat, as well as cell voltage and overpotential in positive electrode and negative electrode with protrusion surface during charging. More polarization reactions together with larger heat generation take place, and cause more entropy generation in area of protrusion. The voltage efficiency is defined to evaluate thermo-electrochemical behaviors in LMBs, and the higher voltage efficiency occurs with the decrease in charging current density. The 93.6% voltage efficiency can be obtained in the case with solid-phase volume fraction of 0.518 in positive electrode under charging current density of 43.608A/m2. All results from investigation will be beneficial to obtain better thermo-electrochemical behavior in Li metal batteries.

Exploring the potential of hybrid nanofluids for enhanced heat transfer in a duct: A comprehensive study utilizing a phases-interaction driven multiphase mixture model

This study investigates the influence of phases interactions in hybrid nanofluids using a multiphase mixture model. Neglecting phase interaction for Al2O3-Cu leads to Nusselt number difference of 0.05 (volume fraction 0.1%), increasing to 0.6 at volume fraction 2%. Among investigated nanofluids (Al2O3-Au NPs, Al2O3-CuO, Al2O3-TiO2, CuO-Au NPs, CuO-TiO2, TiO2-Au NPs), those with gold nanoparticles exhibit exceptional heat transfer enhancements: Al2O3-Au NPs (63.85%), CuO-Au NPs (64.65%), and TiO2-Au NPs (62.10%) at 3% total solid phase volume fraction. CuO-Au NPs perform best, except at ∼5% volume fraction where Al2O3-Au NPs excel. Optimization shows increasing gold particle volume fractions benefit particularly at higher Reynolds numbers. For CuO-Au NPs, highest average Nusselt numbers are obtained at gold volume fractions of 10%, 20%, 40%, and 60% of total solid phases volume fractions for Reynolds numbers 300, 500, 1000, and 2000, respectively. Moreover, the investigation showed that the performance index generally increases with volume fraction up to 5%, except for hybrid nanofluids with gold particles. Notably, in the presence of gold particles, the performance index rises distinctly up to a volume fraction of 3%, followed by a subsequent decline.

Development of High Strength and High Thermal Conductivity Semi-Solid Magnesium Alloy by Thixomolding Process

This paper investigates the influence of Cu addition on the microstructure, mechanical properties, and thermal conductivity of a semi-solid Mg-10Zn alloy produced by Thixomolding process. Microstructure of the Mg-10Zn alloy consists of α-Mg matrix and Mg2Zn second phase. The formation of Cu3Zn phase was found after the addition of Cu particles. Besides, the volume fraction of solid phase decreased in the Mg-Zn/Cu alloy compared with that of binary Mg-Zn alloy. The yield strength of the alloy was enhanced from 157MPa to 188MPa after Cu addition at the sacrifice of a small amount of ductility. Thermal conductivity, on the other hand, were kept the same level of 115-117 (W/m·K) in the Mg-10Zn alloy and Mg-10Zn/Cu alloy. This work demonstrates the potential for developing Mg alloys with high strength and high thermal conductivity via proper alloy design using Thixomolding process.

Bridging pore scale and macroscopic scale foam structure enhanced channel flow cooling with three-dimensional mesoscale simulations

Metal foams with larger interface areas and higher effective conductivities are widely used to increase heat transfer in engineering applications. To reveal the quantitative relation between the pore scale and the macroscale convective thermal transport, foams immersed in a water cooling channel for two high temperature flat plates were simulated by the mesoscale non-dimensional lattice Boltzmann method. The generated structure parameters are global porosities from 0.70 to 0.95 and pore sizes from 6% to 16% of the square channel height. The flow simulation parameters are macroscopic Reynolds numbers from 50 to 1500 and pore scale Reynolds numbers from 3 to 240. Three-dimensional spirals inside foam pores and behind foam structures, which induce the third spatial direction convection, are observed to be positively related to pore sizes, Reynolds numbers, and the volume fractions of fluid and solid phases, respectively. The pore scale drag and heat transfer coefficient constants are inversely correlated from the pressure drop and heat flux of mesoscale simulation results with deviations of 13.2% and 12.5%, respectively. Together with the pore scale geometry factor and the global porosity, the correlations of pore scale and macroscopic scale drag and heat transfer are bridged by microscopic coefficient constants (0.0004, 4.59, 0.47) and (0.0001, 0.096, 0.50, 0.33), respectively. The cross scale correlations provide a practical tool for further engineering applications of enhancing convective cooling through porous structures.

Two-particle method for liquid–solid two-phase mixed flow

Liquid–solid two-phase flows are a very important class of multiphase flow problems widely existing in industry and nature. This paper establishes a two-phase model for liquid–solid two-phase flows considering multiphase states of granular media. The volume fraction is defined by the solid phase, determining the material properties of the two phases, and momentum is exchanged between the phases by drag and pressure gradient forces. On this basis, a two-particle method for simulating the liquid–solid two-phase flow is proposed by coupling smoothed particle hydrodynamics with smoothed discrete particle hydrodynamics. The coupling framework for the two-particle method is constructed, and the coupling between the algorithms is realized through interphase momentum exchange, volume fraction constraint, and field variable sharing. The liquid phase density changes are divided into two types. One is caused by weak compressibility, and the other is caused by changes in the solid phase volume fraction. The former is used to calculate the liquid-phase flow field, and the latter is used to calculate the two-phase coupling to solve the problem of sudden bulk density changes in the liquid phase caused by changes in particle volume fractions. The two-particle method maintains the dual advantages of the particle method for free interface tracking and material point tracking for particles. The new method is validated using a series of fundamental test cases, and comparison with experimental results shows that the new method is suitable for resolving liquid–solid two-phase flow problems and has significant practical value for future simulations of mudflow motions, coastal breakwaters, and landslide surges.

TPMS metamaterial structures based on shape memory polymers: Mechanical, thermal and thermomechanical assessment

Triply periodic minimal surfaces (TPMS) are a type of metamaterial that get their unusual properties from the topology of microstructure elements, but they provide non-controllable properties. Utilizing shape memory polymer as a base material, it is possible to control the properties of these structures and create significant and reversible changes in the stiffness, geometry, and performance of metamaterials which could be applicable in many application fields. In this work, the thermal, mechanical, and shape memory behavior of 8 SMP-based TPMS structures has been studied in a wide range of the solid phase volume fractions (i.e., 35–65%). In the thermomechanical analysis, we consider the shape recovery%, the force recovery%, and the shape fixity% as the shape memory properties. For this purpose, the structures were simulated using thermo-visco-hyperelastic constitutive equations. Also, the temperature rate and elastic modulus are considered as the representative thermal and mechanical properties, respectively. Results of this study indicate that the best shape memory and mechanical behaviors belong to the Primitive structure at all different Volume fractions. And the best overall performance for different 8 TPMS structures including the best thermal, mechanical, and thermomechanical behavior accrues at VF = 40% and is sorted as FKS > FRD > Diamond > Diamond-type 2 > Gyroid > IWP > Primitive > Neovious.

Behavior of Gas–Solid Two-Phase Flow in a Backward Facing Step - Effect of Interparticle Collisions

Abstract This article presents a computational investigation of the dilute gas–solid flow's loss coefficient and reattachment length in a horizontally placed backward-facing step. The article's primary objective is to study the effect of the interparticle collision and three significant parameters, namely, inlet solid-phase volume fraction (αs=0.002, 0.005), particle size (dp = 70 μm and 200 μm), and solid-particle density (ρs = 1500 kg/m3 and 3000 kg/m3). The numerical procedure uses the Eulerian–Eulerian approach in conjunction with the Kinetic theory of Granular flow and the four-way coupling approach. The outcomes show that the loss coefficient and the reattachment length increase as the interparticle collision intensifies with the system. Moreover, these parameters show higher values with small particle sizes and higher solid-phase volume fractions. The reattachment length is higher with less dense solid particles and higher with heavier solid particles.

Analysis of the lithium electrodeposition behavior in the charge process of lithium metal battery associated with overpotential

The Li dendrite growth with non-uniform electrodeposition on negative electrode surface needs to be reduced in lithium metal batteries (LMB). Coupling Butler-Volmer equation and extended Ohm's law with species transport and heat transfer equations, the effects of electrode solid-phase volume fraction and lithium active material amount in porous positive electrode, Li+ ion concentration in electrolyte and protrusion size under different operating temperatures and charging current densities on the performances of LMB with protrusion on negative electrode surface are numerically analyzed during charging. The higher solid-phase volume fraction and more lithium active materials in positive electrode enlarge LMB specific capacity, and the larger exchange current density and Li+ ion concentration in electrolyte cause higher cell overpotential. The protrusion including its size and number on negative electrode surface influence the electrochemical behaviors in cell during charging, in which the higher operating temperature benefits uniform electrodeposition distribution. The comparisons of deposition height, Li+ ion concentration in electrolyte and electrode overpotential are conducted between under constant current and forward or reverse pulse currents in charging. By applying a reverse pulse current (RPC) and reducing forward current duty cycle, more uniform electrodeposition occurs. All results can be utilized to obtain high-performance operation in LMB.

Electrochemical Change Induced by Spherical Indentation in Lithium-Ion Batteries

Since the Young’s modulus of the separator is weaker than that of the other materials inside a lithium-ion battery, local deformation may cause blockage or rupture of the separator, resulting in internal short-circuit or other disasters. This study collects the stress–strain relationship of various materials within the battery, and combines the mechanical model with the electrochemical model through the coupled relationship between the volumetric strain and the volume fractions of solid and liquid phases. From a two-dimensional electrochemical simulation of a spherical indentation on a layer-structured battery, it is found that there is local negative value of the side reaction overpotential on the negative electrode adjacent to the separator after the battery is deformed. A higher strain will cause a decrease in the negative overpotential, leading to a more serious deposition of lithium during the charge process. The deformation-dependent overpotential is evaluated and the lithium deposition is then quantified. Moreover, the issue of the separator thickness is explored. We find that under an indentation, the thickness does not affect the charging voltage, while a thinner layer will reduce the separator porosity and thus lower the overpotential and increase the chance of lithium deposition.

Mathematical Model Research on the Influence of Fluid Parameter Characteristics on the Solid Fluidization Exploration Process of Hydrate Reservoir

Objective: In order to further study the characteristics of flow parameters in the wellbore during solid fluidization drilling, based on the physical model of solid fluidization exploration of hydrate reservoir, a gas-liquid-solid three-phase flow model is established during the drilling process. Methods: The parameter changes of wellbore pressure, section gas holdup, liquid volume fraction, temperature and wellbore hydrate decomposition rate under the influence of different wellhead choke pressure, displacement and drilling fluid density during solid fluidization are analyzed. Results: The analysis results of the case will show that under different wellhead choke pressures, hydrate begins to decompose at 400m to 500m, and with the increase in wellhead choke pressure, the wellbore pressure and the volume fraction of liquid and solid phase at the same position increase significantly, and the gas production rate and the gas volume fraction decrease. The results also show that under different drilling fluid rates, hydrate begins to decompose at 500m to 550m, and with the increase in drilling fluid rate, bottomhole pressure and wellbore temperature increase, the situation of hydrate decomposition becomes better, and gas volume fraction decreases. Conclusion: With the increase of drilling fluid density, hydrate begins to decompose at 500m to 600m, the wellbore temperature increases, and the hydrate decomposition is delayed. Meanwhile, the difference in the location of hydrate decomposition becomes smaller.

Thermal Management of Solar Photovoltaic Cell by Using Single Walled Carbon Nanotube (SWCNT)/Water: Numerical Simulation and Sensitivity Analysis

Despite the attractiveness of Photovoltaic (PV) cells for electrification and supplying power in term of environmental criteria and fuel saving, their efficiency is relatively low and is further decreased by temperature increment, as a consequence of absorption of solar radiation. In order to prevent efficiency degradation of solar cells due to temperature increment, thermal management is suggested. Active cooling of solar cells with use of liquid flow is one of the most conventional techniques used in recent years. By use of nanofluids with improved thermophysical properties, the efficiency of this cooling approach is improvable. In this article, Single Walled Carbon Nano Tube (SWCNT)/water nanofluid is used for cooling of a PV cell by considering variations in different factors such as volume fraction of solid phase, solar radiation, ambient temperature and mass flow rate. According to the findings, use of the nanofluid can lead to improvement in performance enhancement; however, this is not significant compared with water. In cases using water and the nanofluid at 0.5% and 1% concentrations, the maximum improvement in the efficiency of the cell compared with the cell without cooing were 49.2%, 49.3 and 49.4%, respectively. In addition, sensitivity analysis was performed on the performance enhancement of the cell and it was noticed that solar radiation has the highest impact on the performance enhancement by using the applied cooling technique, followed by ambient temperature, mass flow rate of the coolants and concentration of the nanofluid, respectively. Moreover, exergy analysis is implemented on the system and it is noticed that lower ambient temperature and solar radiation are preferred in term of exergy efficiency.

CFD simulation of gas–solid fluidized bed hydrodynamics; prediction accuracy study

Abstract The present study aims at increasing the prediction accuracy of simulating gas–solid fluidized bed hydrodynamics. Two simulation packages, Fluent and MFIX, were used to predict the pressure drop, voidage, and solid-phase velocities by solving mass, momentum, and energy balance equations. A 2D multi-fluid Eulerian model with the kinetic theory of granular flow (KTGF) was applied to simulate the process by considering two different drag models. The same comparative criterion of average absolute relative deviation (AARD%) was considered to compare the present simulation with the previous works. Compared to the prior works, the minimum decrease in error (AARD% of 5.91%) was 3.17% related to the estimation of the time-averaged voidage by applying the Gidaspow model, while the maximum reduction in error (ARRD% of 5.88%) was 17.35% attributed to the prediction of pressure drop by employing the Syamlal-O’Brien model, both in Fluent software. However, MFIX software was the best CFD tool in predicting time-averaged voidage by AARD% values less than 9% under all conditions. Furthermore, similar patterns in contours were observed for solid-phase volume fraction and gas/solid phase velocities in both simulation tools, which are compatible with results from the literature without any significant difference.