Showing papers on "Mixing (process engineering) published in 2019"
TL;DR: This review introduces the application of FNP to produce poorly water-soluble drug nanoparticles by controllable mixing devices, such as confined impinging jets mixer (CIJM), multi-inlet vortex mixer (MIVM) and many other microfluidic mixer systems.
94 citations
TL;DR: In this paper, the effect of different mixing strategies on anaerobic digestion of food waste in order to make the waste-to-energy process more energy efficient was investigated, and it was shown that intermittent mixing is an alternative strategy to continuous mixing or unmixing for high efficient biogas production and energy saving.
68 citations
TL;DR: In this paper, the effect of various fuel injections on the mixing rate inside the supersonic combustion chamber was investigated using computational fluid dynamic (CFD) approach to investigate various fuel injection arrangements inside the cavity flame holder.
63 citations
TL;DR: In this paper, the radial segregation of binary mixtures of ellipsoidal particles in a rotating drum was studied and the effect of rotating speed on the degree of segregation was examined.
46 citations
TL;DR: In this paper, the authors studied the rheology of powder incorporation in the conching of chocolate, and found that the input of mechanical energy and staged addition of surfactants combine to increase the jamming volume fraction of the system, thus increasing the maximum flowable solid content.
Abstract: The mixing of a powder of 10- to 50-μm primary particles into a liquid to form a dispersion with the highest possible solid content is a common industrial operation. Building on recent advances in the rheology of such “granular dispersions,” we study a paradigmatic example of such powder incorporation: the conching of chocolate, in which a homogeneous, flowing suspension is prepared from an inhomogeneous mixture of particulates, triglyceride oil, and dispersants. Studying the rheology of a simplified formulation, we find that the input of mechanical energy and staged addition of surfactants combine to effect a considerable shift in the jamming volume fraction of the system, thus increasing the maximum flowable solid content. We discuss the possible microscopic origins of this shift, and suggest that chocolate conching exemplifies a ubiquitous class of powder–liquid mixing.
45 citations
TL;DR: A modified computational fluid dynamics (CFD) method has been utilized to solve the momentum and mass balances for heterogeneous Fenton process in both reactors, introducing a new parameter, named turbulence mixing rate, as a reaction rate for reactive species like hydroxyl radicals.
44 citations
TL;DR: In this paper, a surface acoustic wave (SAW)-based system composed of a straight interdigitated transducer (IDT) is positioned beneath the polydimethylsiloxane (PDMS) microchannel.
Abstract: The realization of efficient mixing of samples inside a microfluidic channel is essential for performing numerous biological assays in miniaturized total analysis systems. The low Reynolds number flows at the microscale create laminar streams inside the microchannel, limiting flow mixing to a molecular diffusion level. In this paper, we propose a simple and efficient acoustofluidic mixing technique inside a single-layered polydimethylsiloxane (PDMS) microfluidic channel. The proposed surface acoustic wave (SAW)-based system composed of a straight interdigitated transducer (IDT) is positioned beneath the PDMS microchannel. Fluorescein dye dissolved in deionized water (sample fluid) and deionized water (sheath fluid) was introduced through the first and second inlets of the PDMS microchannel, respectively. Their flow rates were controlled such that the sample fluid with fluorescein dye was hydrodynamically focused close to the bottom of the microchannel by the sheath fluid. High-frequency (140 MHz) SAWs, generated from the IDT placed right beneath the first outlet, mixed the two fluids under the influence of strong acoustic streaming flows. The mixed samples were then collected at the two outlet ports for further analysis of the mixing efficiency. The developed acoustofluidic mixing device required an input voltage of 12 Vpp at a total flow rate of 50 μl/min to realize complete mixing. At a similar applied voltage, the throughput of the proposed device could be further increased to 200 μl/min with a mixing efficiency of >90%.
42 citations
TL;DR: In this paper, a zeotropic immiscible working fluid was proposed based on the difficult start and easy dry-out with large heat flux of a pulsating heat pipe (PHP).
41 citations
TL;DR: In this paper, the heat transfer enhancement by means of additively manufactured static mixers during liquid water cooling of a horizontal, heated flat plate was investigated, and the mixers were fabricated directly into the flow channels using additive manufacturing and then assembled onto the heated plate.
41 citations
41 citations
TL;DR: In this article, the rationale behind designs and component selection of continuous flow, laboratory-scale supercritical water gasification reactors is analyzed, and strategies for reactant mixing must be evaluated on a system-by-system basis, depending on feedstock and experimental goals, as mixing can affect product yields, char formation, and reaction pathways.
Abstract: Optimizing an industrial-scale supercritical water gasification process requires detailed knowledge of chemical reaction pathways, rates, and product yields. Laboratory-scale reactors are employed to develop this knowledge base. The rationale behind designs and component selection of continuous flow, laboratory-scale supercritical water gasification reactors is analyzed. Some design challenges have standard solutions, such as pressurization and preheating, but issues with solid precipitation and feedstock pretreatment still present open questions. Strategies for reactant mixing must be evaluated on a system-by-system basis, depending on feedstock and experimental goals, as mixing can affect product yields, char formation, and reaction pathways. In-situ Raman spectroscopic monitoring of reaction chemistry promises to further fundamental knowledge of gasification and decrease experimentation time. High-temperature, high-pressure spectroscopy in supercritical water conditions is performed, however, long-term operation flow cell operation is challenging. Comparison of Raman spectra for decomposition of formic acid in the supercritical region and cold section of the reactor demonstrates the difficulty in performing quantitative spectroscopy in the hot zone. Future designs and optimization of SCWG reactors should consider well-established solutions for pressurization, heating, and process monitoring, and effective strategies for mixing and solids handling for long-term reactor operation and data collection.
TL;DR: In this article, a new model for the use in the framework of the Discrete Element Method to simulate the mixing processes of fresh concrete is presented, which provides a representation of liquid transfer from fluid entities or moist solid particles to dryer solid particles, including volume adaptation and mass conservation.
TL;DR: In this article, the impact of a dyed water droplet onto a clear water film was studied and the color contrast in images allowed investigation of mixing process of the like liquids during the rapid dynamic stage and beyond.
Abstract: In order to advance the understanding of the process of droplet impact on wet surfaces, realized in various applications such as droplet-based coating methods (inkjet printing, aerosol-jet, and spray coating), we studied the impact of a dyed water droplet onto a clear water film. The color contrast in images allowed investigation of mixing process of the like liquids during the rapid dynamic stage and beyond. Four Weber numbers (We), in the range of 121–304, and four dimensionless film thickness to droplet diameter ratios (h*), in the range of 0.092–0.367, were considered. The aforementioned numbers correspond to the film thickness of 0.4–1.6 mm, droplet size of 4.36 mm, and impact velocity of 1.4–2.2 m/s. While the experimental database is rather comprehensive and can be used for further detailed analysis, here we focused on less-explored topics of capillary surface waves formed outside the crater and found the wave characteristics and their role in mixing. Within the range of parameters studied here, we found that the outer capillary surface waves were created as a result of perturbing the liquid film by droplet impact, but the wave characteristics such as frequency (400-500 Hz) were not a strong function of the impact We number. We also observed six mixing mechanisms of miscible liquids, including the expansion/compression waves and turbulence created upon impact, stable crown wall formation with an acute wall angle, which causes a tsunami-type of flow, unstable crown leading to fingering and splashing, capillary waves, and molecular diffusion.
TL;DR: Ceramic membranes with satisfactory chemical stability and high mechanical strength have wide chemical industrial applications in treating wastewater at harsh conditions as discussed by the authors, however, the ceramic membranes are not suitable for industrial applications.
Abstract: Ceramic membranes with satisfactory chemical stability and high mechanical strength have wide chemical industrial applications in treating wastewater at harsh conditions. However, the ceramic suppo...
TL;DR: In this article, a new micromixer design (MTB with triangular baffles and circular obstructions) was proposed aiming the combination of three mass transfer enhancements mechanisms: reduction of molecular diffusion path, split and recombination of streams and vortex generation.
Abstract: A new micromixer design (MTB – micromixer with triangular baffles and circular obstructions) was proposed aiming the combination of three mass transfer enhancements mechanisms: reduction of molecular diffusion path, split and recombination of streams and vortex generation. The geometric variables were also optimized considering the mixing performance and the required pressure drop. The optimal design was used for the mixing of different binary mixtures (vegetable oil/ethanol and water/ethanol) under the Reynolds number range from 0.01 to 200 and the chemical reaction process of vegetable oil transesterification with ethanolic solution of sodium hydroxide (biodiesel synthesis). High mixing index (M = 0.99) was observed for the oil/ethanol mixing for several channel heights (200 μm – 2000 μm) and widths (1500 μm – 3000 μm). The geometry W3000H400 (i.e., MTB with channel width of 3000 μm and height of 400 μm) was employed as the millireactor, providing a maximum oil conversion of 92.67% for a residence time of 30 s. For the water/ethanol mixing, the geometry W1500H200 was used. High mixing index (M = 0.99) was observed at very low Reynolds number (Re = 0.1) and also in higher Reynolds numbers of 50 and 100. Moreover, at Re = 0.1, high mixing index (M ≌ 0.90) was obtained already at 3.5 mm of channel length. However, for higher Reynolds number the fluids required longer distances to achieve superior mixing, about 10.5 mm at Re = 100. The MTB, unlike the ones found in the literature, can be used in microdevices (e.g., sensors) with low flow rates and in microdevices with large dimensions (eg, millidevices and milireactors) with high flow rates, allowing an easier application in chemical process aiming the commercial production.
TL;DR: Careful choice of manufacturing process can be used to tune material properties of ASDs to make them more amenable for downstream operations like tableting.
TL;DR: In this paper, the effects of mix on target performance in magnetized liners inertial fusion (MagLIF) experiments at Sandia National Laboratories were analyzed, showing that mix is likely produced from a variety of sources, approximately half of which originates during the laser heating phase and the remainder near stagnation.
Abstract: In magneto-inertial-fusion experiments, energy losses such as a radiation need to be well controlled in order to maximize the compressional work done on the fuel and achieve thermonuclear conditions. One possible cause for high radiation losses is high-Z material mixing from the target components into the fuel. In this work, we analyze the effects of mix on target performance in Magnetized Liner Inertial Fusion (MagLIF) experiments at Sandia National Laboratories. Our results show that mix is likely produced from a variety of sources, approximately half of which originates during the laser heating phase and the remainder near stagnation, likely from the liner deceleration. By changing the “cushion” component of MagLIF targets from Al to Be, we achieved a 10× increase in neutron yield, a 60% increase in ion temperature, and an ∼50% increase in fuel energy at stagnation.
TL;DR: In this paper, the authors derived coupled non-linear governing equations for the transient properties of hydrogels from the point of view of nonequilibrium thermodynamics, and a numerical simulation of the drying process of a hydrogel film attached on a substrate is carried out based on the governing equations and free energy.
Abstract: A polymer network can imbibe copious amounts of water and swell, and the resulting state is known as a hydrogel. In many potential applications of hydrogels, such as ionic cables, stretchable conductors, and fire resistance materials, the properties of hydrogels may change in response to the environment stimuli. However, existing researches about the transient properties of hydrogels usually treat different physical processes (mass diffusion, heat transportation, electric conduction, etc.) separately, ignoring the fact that there exist correlations between them. In the present work, from the point of view of nonequilibrium thermodynamics, the coupled non-linear governing equations for the transient properties of hydrogels are derived. Instead of writing the free energy of hydrogels as a combination of the stretching of polymer networks and mixing with solvent, we derive the free energy in the form of swelling of hydrogels plus stretching of the swollen hydrogels, which is a function of water content and stretch ratio of hydrogels under external forces or constraints. Chemical potential and total deformation of polymer networks are the fundamental parameters to characterize hydrogel states in many previous research. These are hard to determine, and we are less interested in these parameters. The new form of free energy is more suitable to be used in the laboratory or for the application of hydrogels in real situations, and its physical meaning is clearer. At last, a numerical simulation of the drying process of a hydrogel film attached on a substrate is carried out based on the governing equations and free energy. The transient water content distribution, temperature profile and stress field are investigated, which may provide a guide to the diverse applications of hydrogels.
TL;DR: In this article, a single-crystalline bismuth orthoferrite was synthesized by heat treatment of hydroxides co-precipitated in a free impinging-jets microreactor (FIJMR).
Abstract: Nanocrystalline bismuth orthoferrite was synthesized by heat treatment of hydroxides co-precipitated in a free impinging-jets microreactor (FIJMR). The formation of BiFeO3 nanoparticles without other phase impurities, with a narrow crystal size distribution and an average crystal size of about 20 nm, is shown to be possible after heat treatment at 420–440 °C of the hydroxides co-precipitated in a FIJMR. The BiFeO3 nanoparticles obtained under these conditions are single-crystalline. This effect is attributed to the crucial intensification of mixing process compared to the usual types of reactors: the energy dissipation rate for FIJMR estimated as being in the range of 107–108 W/kg, which is several orders of magnitude higher than in almost all types of reactors, and is comparable with the level achieved when using ultrasonic generators. The sizes of the nanocrystals are shown to be consistent with the sizes of the nanoparticles that can be formed in Kolmogorov microvortices that are formed when jets of reagent solutions collide.
TL;DR: In this article, the authors investigated the mixing process and distribution characteristics of a liquid jet injected into a supersonic crossflow with a Mach number of 2.85 in a cavity-based combustor.
TL;DR: In this article, a self compacting recycled aggregate concrete (SCRAC) when the concrete is subjected to high probability of chloride ingress is employed in conjunction with Nan Su mix design method to study the chloride ions ingress of SCRAC.
TL;DR: A failed embankment on a cement deep mixing (CDM)-formed column-improved soft clay deposit in Saga, Japan, has been reported and analyzed as discussed by the authors, based on the results of the field investigation an...
Abstract: A failed embankment on a cement deep mixing (CDM)-formed column–improved soft clay deposit in Saga, Japan, has been reported and analyzed. Based on the results of the field investigation an...
TL;DR: Foams are used as divergent fluids for conformance control in enhanced oil recovery (EOR) operations as discussed by the authors, which is created by mixing a surfactant and a gas in situ in high-permeability reservoirs (e.g., s...
Abstract: Foams are used as divergent fluids for conformance control in enhanced oil recovery (EOR) operations. It is created by mixing a surfactant and a gas in situ in high-permeability reservoirs (e.g., s...
TL;DR: In this paper, the liquid atomization process of a urea-water solution (UWS) dosing system is investigated using optical diagnosis through back-light imaging, where droplet diameter distribution and the droplet velocity (in the axial and tangential components) are quantified under different air flow and injection conditions.
TL;DR: The research has demonstrated that a multi-constituent growth media will not have a significant effect on the properties of concrete in the proportions likely to be released during mixing, which will allow further development of these novel materials by removing one of the key technical barriers to increased adoption.
Abstract: Previous studies of bacteria-based self-healing concrete have shown that it is necessary to encapsulate and separate the self-healing ingredients (bacteria, nutrients, and precursors) in the concrete so that when a crack forms, capsules rupture, which allows the self-healing ingredients to come together and precipitate calcite into the crack. Because of the shearing action in the concrete mixer, there is a chance that these capsules, or other carriers, may rupture and release the self-healing ingredients. This would affect the efficiency of self-healing, but may detrimentally affect the concrete’s properties. This work investigated the effects of multi-component growth media, containing germination and sporulation aids for the bacterial aerobic oxidation pathway, on the basic properties of fresh and hardened concrete instead of the potential self-healing efficiency in a structural service. Tests were carried out to measure the effects of growth media on air content, fluidity, capillary absorption, strength development of cement mortar following corresponding standards, hydration kinetics, setting properties, and the microstructure of cement paste, according to certain specifications or using specific machines. The research has demonstrated that a multi-constituent growth media will not have a significant effect on the properties of concrete in the proportions likely to be released during mixing. This important conclusion will allow further development of these novel materials by removing one of the key technical barriers to increased adoption.
TL;DR: In this paper, two types of cuts have been introduced in the impeller blade: one at the middle of blade and the other from the middle until the tip of blade (referred as Design 3).
01 Jun 2019-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this article, mixing time, slag eye area, and wall shear stress in a ladle fitted with dual plugs have been studied as a function of operating variables, namely, gas flow rate, radial nozzle position, separation angle between nozzles and flow rate partitioning.
Abstract: Mixing time, slag eye area, and wall shear stress in a ladle fitted with dual plugs have been studied as a function of operating variables, namely, gas flow rate, radial nozzle position, separation angle between nozzles and flow rate partitioning. While the mixing time and slag eye area have been experimentally investigated in a scaled water model (with and without a top slag layer), the shear stress on the vessel wall has been studied computationally via a RANS-based turbulent, three-dimensional coupled Eulerian–Lagrangian (VOF-DPM), multiphase flow model. Experimental and computational results have indicated that the mixing, eye area, and wall shear stress depend on the gas flow rate, i.e., while mixing efficiency increases with the increasing gas flow rate, the slag eye area, and wall shear stress, in contrast, become more pronounced with the increasing gas flow, leading to an undesirable operating regime. The radial nozzle position, separation angle between the nozzles and flow rate partitioning at any given flow rate also influence the ladle process performance, influencing the mixing, eye area, and wall shear stress, albeit to a varied degree. Within the range of operating conditions studied, an expected inverse correspondence between mixing time and shear behavior was observed. Experimental and computational results in conjunction have indicated that the best arrangement of porous plugs or gas injection nozzles for superior ladle process performance is dependent on the gas flow rate and is specific to the desired objective (i.e., decreasing the mixing time, or slag eye area and wall shear stress). Hence, a unique gas injection practice cannot and should not be suggested as the optimum for ladle metallurgy in steelmaking. Nevertheless, if the mixing time is the parameter of primary interest, a nozzle configuration with equal flow partitioning (1:1) between the nozzles and identical nozzle radial positions (0.7R/0.7R, 45 deg) should suffice for both low and high gas flow rates. In contrast, a nonidentical nozzle radial position (0.7R/0.5R, 90 deg) and an unequal gas flow rate per nozzle (1:3) appear preferable if both ladle eye and shear stresses, rather than mixing, are the issues of concern.
TL;DR: An effective and low-cost microfluidic device integrated with microscale magnets manufactured with neodymium (NdFeB) powders and polydimethylsiloxane (PDMS) to achieve rapid micromixing between ferrofluid and buffer flow is developed.
Abstract: Ferrofluid-based micromixers have been widely used for a myriad of microfluidic industrial applications in biochemical engineering, food processing, and detection/analytical processes. However, complete mixing in micromixers is extremely time-consuming and requires very long microchannels due to laminar flow. In this paper, we developed an effective and low-cost microfluidic device integrated with microscale magnets manufactured with neodymium (NdFeB) powders and polydimethylsiloxane (PDMS) to achieve rapid micromixing between ferrofluid and buffer flow. Experiments were conducted systematically to investigate the effect of flow rate, concentration of the ferrofluid, and micromagnet NdFeB:PDMS mass ratio on the mixing performance. It was found that mixing is more efficient with lower total flow rates and higher ferrofluid concentration, which generate greater magnetic forces acting on both streamwise and lateral directions to increase the intermixing of the fluids within a longer residence time. Numerical models were also developed to simulate the mixing process in the microchannel under the same conditions and the simulation results indicated excellent agreements with the experimental data on mixing performance. Combining experimental measurements and numerical simulations, this study demonstrates a simple yet effective method to realize rapid mixing for lab-on-chip systems.
TL;DR: In this article, the influence of the gas to liquid volume ratio on the spray formation, jet morphology and scales of turbulence in the nozzle far-field are studied to assess the performance of the external-mixing gas-assisted SpraySyn-nozzle.
Abstract: The synthesis of nanoparticles via flame spray pyrolysis (FSP) is based on a couple of physicochemical steps such as precursor atomization, droplet evaporation, fuel combustion, particle nucleation and growth. Most recent studies on FSP are focused on the particle formation without taking the antecedent precursor atomization and spray formation into account. In the present work, the atomization characteristics under burning and non-burning conditions are investigated by means of laser sheet Mie-scattering images and phase Doppler anemometry. The influence of the gas to liquid volume ratio on the spray formation, jet morphology and scales of turbulence in the nozzle far-field are studied to assess the performance of the external-mixing gas-assisted SpraySyn-nozzle. The turbulent flame spray is characterized by the Kolmogorov length scale and the Kolmogorov shear rate. The droplet–droplet interaction and group combustion behaviour, enabling clouds of merely vaporizing droplets surrounded by a flame sheath, are investigated. The experimentally determined droplet velocities, turbulence length scales and the analysis of group combustion modes allow a deeper insight into the spray flame dynamics and droplet mixing zones.
TL;DR: In this article, a series of experiments were carried out by varying mixing conditions, solid concentration, water salinity and flocculant dosage to study the dependence of the flocculation process on the suspension-flocculusant mixing conditions.
Abstract: The presence of fine and ultra-fine gangue minerals in flotation plants can contribute to sub-optimal valuable ore recovery and incomplete water recycling from thickeners, with the performance of the latter equipment relying on adequate flocculation. In order to study the dependence of the flocculation process on the suspension-flocculant mixing conditions, a series of experiments—chosen using chemometric analysis—were carried out by varying mixing conditions, solid concentration, water salinity and flocculant dosage. To this purpose, two different tailings (both featuring coarse and fine content) were considered and a response surface methodology based on a Doehlert experimental design was used. The results suggest that the operational conditions to optimise the flocculated tailings settling rate and the suspended solids that report to a thickener overflow are not necessarily the same. This is a reasonable outcome, given that the settling rate depends on the coarse aggregates generated in the slurry, while the overflow solids content is governed both by either fine particle content (and its characteristics) or small aggregates. It is inferred that to maximise dewatering performance two stages should be involved—a separate treatment of the thickener overflow to remove fine content and thickening at optimal flocculant dosage to enhance this process.