Varying Volume Fractions Research Articles

Effect of Particle Orientation on Heat Transfer in Arrays of Prolate Particles

Direct Numerical Simulations have been carried out to study the forced convection heat transfer of flow through fixed prolate particles for a variety of aspect ratios ar = {5/4, 5/3, 5/1} with Reynolds number (Re) up to 100. Three variations of the solid volume fraction c = {0.1, 0.2, 0.3} with four Hermans orientation factors S = {−0.5, 0, 0.5, 1} are studied. It has been found that changes in S cause prominent variations in the Nusselt number. In general, Nusselt number increases with the decrease of S. For all three aspect ratios, the Nusselt number remains a linear function of S at different c and Re. Therefore, it is concluded that, for heat transfer from prolate muti-particle system, the effects of orientations cannot be ignored. A new correlation for Nusselt number has been developed for arrays of prolate particles using the simulation data as a function of Re, c, S and ar.

Heat transfer studies in a plate heat exchanger using Fe2O3-water-engine oil nanofluid

Improving the heat transfer performance of conventional fluid creates significant energy savings in process Industries. In this aspect, an experimental study was performed to evaluate the heat transfer performance of Fe2O3-water (W)-engine oil (EO) nanofluid at different concentrations and hot fluid inlet temperatures in a plate heat exchanger. Experiments were conducted by mixing Fe2O3 nanoparticles (45 nm) in a W-EO mixture base fluid with volume fractions of 5% EO + 95% W and 10% EO +90% W. The main aim of the present study was to assess the impacts of nanoparticle volume fraction and hot fluid inlet temperature variations on the heat transfer performance of the prepared nanofluid. The convective heat transfer coefficient, Reynolds, Prandtl, and Nusselt numbers were determined based on the experimental results. The result shows that at the hot fluid inlet temperature of 75 ?C, the increase in Nusselt number and convective heat transfer coefficient are optimum at 0.9 vol. % nanoparticle for both the base fluid mixtures. The increase in heat transfer coefficient is because of the Brownian motion (increasing thermal conductivity) effect, motion caused by the temperature gradient (Thermo-phoretic), and motion due to concentration gradient (Osmophoretic). If the volume fraction of the nanoparticle increases, then the Reynolds number increment is higher than the Prandtl number decrement, which augments the Nusselt number and convective heat transfer coefficient.

Numerical Assessment of Nanofluid Natural Convection Using Local RBF Method Coupled with an Artificial Compressibility Model

In this paper, natural heat convection inside square and equilateral triangular cavities was studied using a meshless method based on collocation local radial basis function (RBF). The nanofluids used were Cu-water or -water mixture with nanoparticle volume fractions range of . A system of continuity, momentum, and energy partial differential equations was used in modeling the flow and temperature behavior of the fluids. Partial derivatives in the governing equations were approximated using the RBF method. The artificial compressibility model was implemented to overcome the pressure velocity coupling problem that occurs in such equations. The main goal of this work was to present a simple and efficient method to deal with complex geometries for a variety of problem conditions. To assess the accuracy of the proposed method, several test cases of natural convection in square and triangular cavities were selected. For Rayleigh numbers ranging from to , a validation test of natural convection of Cu-water in a square cavity was used. The numerical investigation was then extended to Rayleigh number , as well as -water nanofluid with a volume fraction range of . In a second investigation, the same nanofluids were used in a triangular cavity with varying volume fractions to test the proposed meshless approach on non-rectangular geometries. The numerical results appear to be in agreement with those from earlier investigations. Furthermore, the suggested meshless method was found to be stable and accurate, demonstrating that it may be a viable alternative for solving natural heat transfer equations of nanofluids in enclosures with irregular geometries.

NUMERICAL INVESTIGATIONS OF A SWIRLING TWO-PHASE AIR-WATER UPWARD FLOW IN STRAIGHT AND CONVERGENT VERTICAL PIPE

In this study, a numerical study is presented to analyze the flow parameters such as longitudinal and transverse velocities, hydrodynamic pressure, and volume fraction inside a vertical pipe. A vertical ascending swirl flow is established with the specified boundary conditions and compared between straight and convergent geometry pipes. Normalized film thickness is found to vary between 0.4 and 0.6, where the numerical output data from the present study resemble wire-mesh sensor data from literature. Convergent pipe flow includes the variation of hydrodynamic pressure thereby affecting the slug and bubble flow region. Longitudinal and transverse velocities are plotted against time and compared at the three inspection planes near the inlet, mid-portion, and outlet, respectively. In order to understand the effectiveness of rotational effect of gas and liquid phases, the vorticity components are studied. Parameters such as Q-criterion and vortex stretching term indicate the straining and shearing flow near the peripheral and core regions. The temporal volume fraction variation at the output section indicates the increase in the output liquid yield of convergent pipe outlet by 17%.

Effect of Hollow Glass Microsphere (HGM) on Impact and Flexural Properties of High-Density Syntactic Foam Based Epoxy Composites

Syntactic foam composite offers versatile application possibilities in marine, structural, aerospace industries due to their good tensile, flexural, and compressive strength, corrosive resistance, high specific strength and modulus, light weight nature. Their porous structure is by mixing hollow particles called microspheres as fillers into matrix materials such as polymer, metal or ceramic etc. In this study, a high-density hollow glass microsphere is used to fabricate syntactic foam by mixing it with epoxy resin. Five different compositions 5, 10, 15, 20 and 25 vol% of hollow glass microspheres were varied in fabricating the syntactic foam. Impact and flexural properties were investigated on the syntactic foam. All the compositions of the volume fraction variations of hollow glass microsphere content in the syntactic foam increased more than the neat epoxy. The highest impact resistance, flexural strength and flexural modulus is at 5 vol%, 113.12 kJ/m2, 86.7 MPa, and 80 GPa respectively with 25.2%, 38.29%, and 33.25% increase respectively more the neat epoxy while the specific impact and flexural strength is at 25 vol% with 53.78% and 57.77% increase respectively more than the neat epoxy.

Mixture of an ionic liquid and organic solvent at graphene: interface structure and ORR mechanism.

Aprotic lithium-oxygen batteries are attracting the attention of the scientific community due to their outstanding theoretical performance, which, however, still has not been achieved in practice. One of the promising directions for improving the stability of Li-O2 batteries is electrolyte design, which would provide good cyclability, inhibition of parasitic processes, and high energy density. In recent years, there has been progress in the use of ionic liquids in the composition of the electrolyte. The present work reveals possible explanations of the influence of the ionic liquid on the mechanism of the oxygen reduction reaction by the example of a combined electrolyte from an organic solvent DME and an ionic liquid Pyr14TFSI. Molecular dynamics modelling of the interface between a graphene electrode and an organic solvent DME with a variable volume fraction of the ionic liquid shows the influence of the electrolyte structure at the interface to the kinetics on the adsorption and desorption stages of oxygen reduction reaction reactants. The obtained results suggest the promotion of a two-electron oxygen reduction reaction mechanism through the formation of solvated O22-, which may explain the reduced recharge overpotential reported in experiments.

Magnetized Tri-hybrid Nanofluids flow with binary Chemical Reaction and activation Energy through the porous Surfaces

Hybrid nanofluids are important to researchers because of their industrial applications due to their high heat transfer rates. Tri hybrid different types of nanoparticles are discussed here with Newtonian fluids under the effect of MHD. The most important chemical reaction associated with mass transfer and activation energy parameters hasbeen discussed in detail. The current research focuses on two-dimensional fluids with heat transfer enhancement flowing over a porous surface. The mathematical modeling of the problem, as well as empirical relations for nanoparticle materials, is expressed as PDEs, which are then translated into ODEs using appropriate variables. The Runge–Kutta and shooting methods are combined to solve the problems of the created coupled differential system. Variations in nanoparticle volume fraction at the lower and upper walls of porous plates, as well as heat transfer rate measurements, are computed using controlling physical factors. The impact of flow-related variables on the axial, radial, and temperature components of velocity and temperature distribution is also assessed.

Pengaruh Fraksi Volume dan Orientasi Serat Pada Komposit Hibrid Berpenguat Serat Gambas serta Eceng Gondok Terhadap Kekuatan Bending

Wood is increasingly difficult to obtain due to the use of excess wood. Many efforts were made to replace wood, one of which was composite material. This study aims to determine the most optimal bending strength with the influence of variations in volume fractions and fiber orientation in hybrid composites with luffa fibers and hyacinth fibers. In making composites using the hand lay-up method with alaklization treatment on gambas and hyacinth fibers using 5% NaOH which is varied with the volume fraction used in this study with the ratio of resin: hyacinth: gambas is (60%:20% :20%),(70%:15%:15%), as well as (80% :10%:10%) and the orientation of the fibers with the arrangement of the luffa / hyacinth / luffa layer is (0°/ 45 °/ 90°), (0˚/45˚/0˚), (90˚/0˚/90˚). Bending testing was performed with ASTM D790 standard and hypothesis testing using the two-way ANOVA method. From the results of bending testing, the most optimal strength value was found, which was 43.33 N / mm2, where the value was not higher than the bending strength value in the multiplex, which was 17.53 N / mm2. Meanwhile, the results of hypothesis testing are that there is an influence on the volume fraction factor, the direction of fiber orientation and the interaction with bending forces.

Reconsideration of surface tension and phase state effects on cloud condensation nuclei activity based on the atomic force microscopy measurement

Abstract. Dicarboxylic acids are ubiquitous in atmospheric aerosol particles, but their roles as surfactants in cloud condensation nuclei (CCN) activity remain unclear. In this study, we investigated CCN activity of inorganic salt (sodium chloride and ammonium sulfate) and dicarboxylic acid (including malonic acid (MA), phenylmalonic acid (PhMA), succinic acid (SA), phenylsuccinic acid (PhSA), adipic acid (AA), pimelic acid (PA), and octanedioic acid (OA)), mixed particles with varied organic volume fractions (OVFs), and then directly determined their surface tension and phase state at high relative humidity (over 99.5 %) via atomic force microscopy (AFM). Our results show that CCN-derived κCCN of studied dicarboxylic acids ranged from 0.003 to 0.240. A linearly positive correlation between κCCN and solubility was obtained for slightly dissolved species, while negative correlation was found between κCCN and molecular volume for highly soluble species. For most inorganic salts and dicarboxylic acids (MA, PhMA, SA, PhSA and PA), a good closure within 30 % relative bias between κCCN and chemistry-derived κChem was obtained. However, κCCN values of inorganic salt–AA and inorganic salt–OA systems were surprisingly 0.3–3.0 times higher than κChem, which was attributed to surface tension reduction, as AFM results showed that their surface tensions were 20 %–42 % lower than that of water (72 mN m−1). Meanwhile, semisolid phase states were obtained for inorganic salt–AA and inorganic salt–OA and also affected hygroscopicity closure results. Our study highlights that surface tension reduction should be considered when investigating aerosol–cloud interactions.

Optimization of Two-Phase Ejector Mixing Chamber Length under Varied Liquid Volume Fraction.

The ejector performance varies with the mixing chamber length which is largely dependent on the fluid liquid volume fraction at the inlet. In this study, numerical simulations are conducted to optimize two mixing chamber lengths of a two-phase ejector under varied liquid volume fractions of 0-0.1 in two inlet fluids. The main findings are as follows: (1) The two optimal lengths of constant-pressure and constant-area mixing chambers are identified within 23-44 mm and 15-18 mm, respectively, when the primary inlet fluid is in two-phase; (2) the two optimal lengths are 2-5 mm and 9-15 mm, respectively, when the secondary inlet fluid is in two-phase; (3) when both inlets are in two-phase, the two optimal lengths are ranged in 5-23 mm and 6-18 mm; (4) little liquid within inlet fluid has a significant influence on ejector performances; and (5) optimal constant-pressure mixing chamber length and the sum of the two optimal lengths increase with the primary flow inlet liquid volume fraction but decrease with that of the secondary flow inlet.

Numerical Simulation of Mixing between Sequential Fluids in a Pipeline Considering Real Conditions

AbstractThe mixing behavior of two sequential petroleum products resulting from convection and diffusion mechanisms was numerically modeled. To this end, the initial mixing that happens during the fluid change in the pipeline was considered. A numerical code was also developed, and two‐dimensional volume fraction variations of a 100‐m‐long, 16‐in‐diameter pipe were calculated. The model was validated by comparison with field data in a real pipeline. The results showed a significant difference in mixing length between the old and new conditions. When the actual conditions were used, the error in the results was reduced from 62 to 12 %. Overall, it was discovered that if available correlations are modified on the basis of the initial mixing, they can also produce good results in short pipelines.

Quantitative assessment of machine-learning segmentation of battery electrode materials for active material quantification

X-ray computed tomography (CT) is an important tool for studying battery electrode microstructures but relies on robust segmentation for validity. Here, several approaches to applying accessible machine-learning segmentation software to segment open-source lithium-ion battery (LIB) electrode tomograms are followed to identify the optimised methodology that minimises variation in active material volume fraction quantification across three users. Iterative, manual training across seven cross-sectional slices (<5%) of a tomogram is identified as an optimal balance between variance and user interaction, where 10–25% of each slice was trained. This approach is applied to lab-based X-ray CT data and compared with data obtained by focused-ion beam/scanning electron microscopy slice-and-view tomography. Variation in active material volume fraction between users is lower for at least one of these two approaches (10% or 25%) when applied to raw LIB cathode tomograms, versus unsupervised techniques such as simple and watershed segmentations. On average, the absolute volume fraction values are closer to that acquired by the correlated technique, most closely matching for high-resolution data. The present analysis provides an optimised approach for using open-source software to apply machine-learning segmentation when quantifying active material volume fractions in cutting-edge LIB electrodes, providing a more robust route to active material quantification.

Analisis Kekuatan Bending Komposit Lamina Serat Ijuk Anyam dan Serat Ijuk Acak bermatriks Polyester

The current automotive industry uses composite materials as an alternative material to replace metal or plastic, due to the advantages of composite materials that have biodegradable properties and support environmental sustainability. Composite materials can be used as car body protectors, as a protector composite materials must withstand compressive loads. Referring to this, the research will be carried out through flexural testing. Study aim is to analyze variations of fiber volume fraction effect to the flexural strength. Method of making composite materials using hand layup then press mold, variations in fiber volume fraction 25%, 30%, 35%, 40%, and 45%. Flexural testing is carried out according to ASTM D-790. The morphology analysis was also carried out on the fractures of result of flexural test. Flexural testing results show that the highest flexural strength is founded in the fiber volume fraction 50% and the lowest flexural strength is founded in the fiber volume fraction 25%, 724.4 MPa and 435.8 MPa, respectively. A suitable composition in the fiber volume fraction of 40% can produce an optimal bond between the matrix and the fiber. Observing the morphology of the fracture and the cross-section of the fracture flexural testing results, it was found that there were fiber fractures with the characteristics of fiber pullout and delamination in each test specimen.

Numerical investigation on forced convection enhancement within an oil cooler through the simultaneous use of porous media and nanofluid

Traditional strategies for improving heat transmission in industrial systems include nanofluids and porous inserts. In these kinds of systems, increasing the rate of thermal transmission can also be accomplished by utilizing porous materials that have a higher thermal conductance. Al2O3, CuO, and ZnO in engine oil (20w50) nanofluid are studied numerically in three dimensions to see how they affect forced convection in a porous media oil cooler. Within the oil cooler, the porous medium was placed. A two-phase mixture model was used in conjunction with the Darcy–Brinkman–Forchheimer equation indicating the drag forces to simulate nanofluid flow in porous media. In addition, utilizing temperature laboratory data, a more specific thermophysical feature of the fluid was identified and characterized. ANSYS-FLUENT, a commercial computational fluid dynamics (CFD) software, is used to partition the governing equations using the finite volume method. In addition, the thermal boundary parameters of the oil cooler walls were made to be temporally constant and spatially uniform. The effects of varying volume fractions (ranging from 0% to 5%), Darcy number (ranging from 10−2 to 102), overall Nusselt number, pressure reduction, and the performance evaluation criteria (PEC) were analyzed and compared for a variety of distinct nanoparticles. The increased Darcy number (10−2 to 102) had a significant effect on the enhanced heat transfer coefficient, according to the data. In light of the findings, it can be deduced that the high-volume percentage of the nanoparticles will improve thermal transmission and, more significantly, the PEC factor. Furthermore, the given variables were compared, leading to the creation of diagrams for different variables.

Trabecular bone ontogeny tracks neural development and life history among humans and non-human primates

Trabecular bone-the spongy bone inside marrow cavities-adapts to its mechanical environment during growth and development. Trabecular structure can therefore be interpreted as a functional record of locomotor behavior in extinct vertebrates. In this paper, we expand upon traditional links between form and function by situating ontogenetic trajectories of trabecular bone in four primate species into the broader developmental context of neural development, locomotor control, and ultimately life history. Our aim is to show that trabecular bone structure provides insights into ontogenetic variation in locomotor loading conditions as the product of interactions between increases in body mass and neuromuscular maturation.Our results demonstrate that age-related changes in trabecular bone volume fraction (BV/TV) are strongly and linearly associated with ontogenetic changes in locomotor kinetics. Age-related variation in locomotor kinetics and BV/TV is in turn strongly associated with brain and body size growth in all species. These results imply that age-related variation in BV/TV is a strong proxy for both locomotor kinetics and neuromuscular maturation. Finally, we show that distinct changes in the slope of age-related variation in bone volume fraction correspond to the age of the onset of locomotion and the age of locomotor maturity.Our findings compliment previous studies linking bone development to locomotor mechanics by providing a fundamental link to brain development and life history. This implies that trabecular structure of fossil subadults can be a proxy for the rate of neuromuscular maturation and major life history events like locomotor onset and the achievement of adult-like locomotor repertoires.

An Energy Minimization Approach to Twinning with Variable Volume Fraction

In materials that undergo martensitic phase transformation, macroscopic loading often leads to the creation and/or rearrangement of elastic domains. This paper considers an example involving a single-crystal slab made from two martensite variants. When the slab is made to bend, the two variants form a characteristic microstructure that we like to call “twinning with variable volume fraction.” Two 1996 papers by Chopra et al. explored this example using bars made from InTl, providing considerable detail about the microstructures they observed. Here we offer an energy-minimization-based model that is motivated by their account. It uses geometrically linear elasticity, and treats the phase boundaries as sharp interfaces. For simplicity, rather than model the experimental forces and boundary conditions exactly, we consider certain Dirichlet or Neumann boundary conditions whose effect is to require bending. This leads to certain nonlinear (and nonconvex) variational problems that represent the minimization of elastic plus surface energy (and the work done by the load, in the case of a Neumann boundary condition). Our results identify how the minimum value of each variational problem scales with respect to the surface energy density. The results are established by proving upper and lower bounds that scale the same way. The upper bounds are ansatz-based, providing full details about some (nearly) optimal microstructures. The lower bounds are ansatz-free, so they explain why no other arrangement of the two phases could be significantly better.

Direct numerical simulations for assessment of gas-solid drag models in two-dimensional random arrays of particles

The momentum exchange between the phases plays a vital role in modelling of gas–solid flows and it is mathematically described by drag models. However, no consensus exists on which drag model gives the most accurate prediction of the drag force, and, despite the increase in available computing power, the same drag models are used in two-dimensional and three-dimensional simulations. In this study, direct numerical simulations of gas flow through multiple random configurations of static monodisperse particles are performed. The variations of solid volume fraction and particle Reynolds number are in the ranges of 0.05–0.4 and 13.7–136.9, respectively. The drag force exerted on particles is calculated and properly averaged. Based on the simulation results, thirteen drag models are compared and correction factors are introduced using the stochastic gradient descent algorithm. The correction factors provide a simple adjustment for the models to be used in 2D modelling.

Fluidization regimes of dense suspensions of Geldart group A fluidized particles in a high aspect ratio column

Fluidization regimes were studied in numerous papers with applications in risers in which gas velocity is the main driving force. The situation is different when a tube is immersed in a fluidized bed vessel in which a pressure is imposed to move the particle upward. The particle-in-tube solar receiver concept is based on this latter operation mode with the aim to heat particles at high temperature with concentrated solar energy. This study identifies the fluidization regimes in a pressure-driven system that includes a secondary aeration to control the air velocity in the tube. Bubbling, slugging, turbulent and fast fluidization regimes are determined thanks to temporal pressure signal processing methods and a regime map is plotted. The transition velocities are significantly lower than in classical risers. The local slip velocity is defined as the governing parameter of the flow structure and the variation of the local particle volume fraction is discussed.

Role of microstructure heterogeneity on deformation behaviour in additive manufactured Ti-6Al-4V

The influence of two different bi-lamellar microstructures, with varied volume fractions of primary alpha lamellae (αp) and secondary alpha lamellae (αs), on the mechanical performance of laser powder bed fusion fabricated Ti-6Al-4V has been investigated. A low and high αp volume fraction variant was created by different solution heat treatment temperatures. Scanning transmission electron microscopy (STEM) was performed on both materials to give a comprehensive assessment of the local microstructure and element partitioning effects. Deformation experiments, combined with high resolution digital image correlation (HRDIC), enabled a detailed comparison of 2D slip patterns at progressive strain increments during tensile loading, with the underlying microstructure collected using electron backscattering diffraction based grain orientation mapping. In both microstrural variants, shear strain was mainly observed in the coarse αp lamellae, suggesting that the constituent was softer than the fine αs regions. This strength difference is not attributed to potential different levels of Al-based solid solution strengthening as a result of element partitioning. Instead, the strength difference was attributed to the fine β ligaments formed in-between the αs during ageing. The low αp volume fraction variant, i.e. high-volume fraction of αs, displayed a significant increase in yield strength compared to the high αp volume fraction variant without compromising ductility through increased heterogeneous plasticity and an enhanced strain hardening rate.

Predicting the elasto-plastic response of short fiber reinforced composites using a computationally efficient multi-scale framework based on physical matrix properties

Predicting the nonlinear mechanical response of short fiber reinforced composites (SFRCs) is a crucial and challenging task. In this paper, a computationally efficient multi-scale strategy is proposed to predict the anisotropic elasto-plastic behavior of SFRCs using the intrinsic mechanical behavior of the pure polymer and fibers without the requirements for reverse engineering. In doing so, different simple unit cells are first examined to find the one that can adequately describe the nonlinear mechanical response of SFRCs' representative volume elements (RVE) with aligned fibers. Considering the effects of packing configuration, fiber aspect ratio, volume fraction and material properties, the performance of different unit cells is investigated. Then, the homogenized mechanical responses of unit cells are linked to Hill's anisotropic plasticity model to correlate the mechanical response of the suggested unit cell to the continuum domain. Using the pseudo-grain approach and a numerical orientation averaging framework, the effects of fiber misalignment are taken into account. A multi-step homogenization strategy is also employed to consider the variation of fiber orientation tensor and volume fraction through the thickness. Finally, the validity and robustness of the proposed multi-scale strategy are extensively investigated based on the RVE-generated results and the available experimental observations.