scholarly journals Numerical Simulations of a Gas–Solid Two-Phase Impinging Stream Reactor with Dynamic Inlet Flow

Energies ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1913 ◽  
Author(s):  
Xueqing Liu ◽  
Song Yue ◽  
Luyi Lu ◽  
Wei Gao ◽  
Jianlan Li
Keyword(s):  
Residence Time ◽  
Single Particle ◽  
Particle Motion ◽  
Oscillatory Motion ◽  
Two Phase ◽  
Inlet Flow ◽  
Inlet Velocity ◽  
Particle Residence Time ◽  
The Mean ◽  
Inlet Conditions

Fluid flow characteristics and particle motion behavior of an impinging stream reactor with dynamic inlet flow (both inlet velocity patterns exhibit step variation) are investigated and discussed with the computational fluid dynamics–discrete element method (CFD–DEM). The effect of T (variation period of the dynamic inlet flow) and ∆u (inlet velocity difference) on the motion characteristics of single and multiple particles, as well as the mean particle residence time, are studied and discussed. The research results indicate that, compared with the traditional impinging stream reactor (both inlet velocities are equal and constant) with equal mean inlet velocity (um) within one period, the impinging surface is instantaneously moving and the flow regime is varied with time in the impinging stream reactor with dynamic inlet flow. The impinging stream reactor with dynamic inlet flow provides higher cost performance over the traditional impinging stream reactor, under equal um, in terms of single-particle residence time. Moreover, three new particle motion modes exist in multi-particle motions of the impinging stream reactor with dynamic inlet flow; particles are accelerated by the original or reverse fluid and perform oscillatory motion at least once after an interparticle collision. Whether it is a single particle or multi-particles, the mean particle residence time reaches a maximum value when T/2 is approximately equal to the first particle acceleration time, since the maximum axial kinetic energy increases in every oscillatory motion compared with traditional impinging stream, and the number of oscillatory motions is increasing. The mean residence time of a particle in the impinging stream reactor with a dynamic inlet flow increases with increasing ∆u, since the dynamic inlet conditions and increasing ∆u can continuously supply more energy to particles and thus cause more particles to enter one of the three new modes of particle motion.

Effect of Particle Residence Time on Particle Dispersion in a Plane Mixing Layer

1993 ◽  
Vol 115 (4) ◽  
pp. 751-759 ◽  
Author(s):  
Tsuneaki Ishima ◽  
Koichi Hishida ◽  
Masanobu Maeda
Keyword(s):  
Gas Phase ◽  
Residence Time ◽  
Time Scale ◽  
Characteristic Time ◽  
Mixing Layer ◽  
Particle Dispersion ◽  
Laser Doppler Velocimeter ◽  
Characteristic Time Scale ◽  
Two Phase ◽  
Particle Residence Time

A particle dispersion has been experimentally investigated in a two-dimensional mixing layer with a large relative velocity between particle and gas-phase in order to clarify the effect of particle residence time on particle dispersion. Spherical glass particles 42, 72, and 135 μm in diameter were loaded directly into the origin of the shear layer. Particle number density and the velocities of both particle and gas phase were measured by a laser Doppler velocimeter with modified signal processing for two-phase flow. The results confirmed that the characteristic time scale of the coherent eddy apparently became equivalent to a shorter characteristic time scale due to a less residence time. The particle dispersion coefficients were well correlated to the extended Stokes number defined as the ratio of the particle relaxation time to the substantial eddy characteristic time scale which was evaluated by taking account of the particle residence time.

scholarly journals Numerical Analysis of Single-Particle Motion Using CFD-DEM in Varying-Curvature Elbows

2022 ◽  
Vol 10 (1) ◽  
pp. 62
Author(s):  
Chao Ning ◽  
Yalin Li ◽  
Ping Huang ◽  
Hongbo Shi ◽  
Haichao Sun
Keyword(s):  
Single Particle ◽  
Particle Motion ◽  
Numerical Study ◽  
Area Ratio ◽  
Centrifugal Pumps ◽  
Distribution Law ◽  
Two Phase ◽  
Curvature Ratio ◽  
Critical Components ◽  
Solid Liquid

Centrifugal pumps are the critical components in deep-sea mining. In order to investigate the particle motion in the curved channel of the impeller, three different types of curvature conform to blade profile to simplify the impeller design of pumps. A numerical study is conducted to investigate the flow field in a varying-curvature channel for solid-liquid two-phase flow. The flow of particles within the varying curvature channel is studied by combining the discrete element method (DEM) with computational fluid dynamics (CFD) and a comparison with Particle Image Velocimetry (PIV) test results. The results show that a polyhedral mesh with a small mesh number yields very accurate results, which makes it very suitable for CFD-DEM. Based on this method, the movement of a single particle is compared and analyzed, and the particle-motion law is obtained. The effects of the curvature ratio Cr and area ratio Ar on the motion law for a single particle are studied, and the simulation results are analyzed statistically. The results show that the effect of Cr on both the particle slip velocity and the turbulent kinetic energy only changes its strength, while the distribution law does not change significantly. Compared with the curvature ratio Cr, the area ratio Ar has a greater impact on the particles, and its distribution law becomes clearly different. As the area ratio Ar increases, the arc radius and length of the corresponding particle trajectory decrease.

scholarly journals Simulation of Blood Flow and Nanoparticle Transport in a Stenosed Carotid Bifurcation and Pseudo-Arteriole

2012 ◽  
Vol 4 (1) ◽  
pp. 85-101
Author(s):  
Graham Doig ◽  
Guan H. Yeoh ◽  
Victoria Timchenko ◽  
Gary Rosengarten ◽  
Tracie J. Barber ◽  
...  
Keyword(s):  
Residence Time ◽  
Particle Diameter ◽  
Carotid Bifurcation ◽  
Nanoparticle Transport ◽  
Particle Residence Time ◽  
Flow Through ◽  
The Mean ◽  
Particle Approach ◽  
Wall Interactions

Numerical simulation of flow through a realistic bifurcated carotid artery geometry with a stenosis has been conducted for comparison to experimental measurements. The behaviour of simplified therapeutic nanoparticles in relatively low concentration was observed using a discrete particle approach. The role of size (diameters from 500 nm to 50 nm) in determining particle residence time and the potential for both desirable and undesirable wall interactions was investigated. It was found that mean particle residence time reduced with decreasing particle diameter, and the percentage of particles experiencing one or more wall interactions increased simultaneously. Further simulations were conducted on a scaled-down version of the geometry which approximated the size and flow conditions of an arteriole with capillary branches, and in this instance the mean residence time increased with decreasing particle diameter, owing largely to the greater influence of Brownian motion. 33% of all 50 nm particles were involved in wall interactions, indicating that smaller particles would have a greater ability to target, for instance, cancerous tumours in such regions.

The Effects of Inlet Flow Conditions on Gas-Liquid Two-Phase Flow in a Micro Tube

2007 ◽  
Author(s):  
Shota Hayashi ◽  
Nobuhide Kasagi ◽  
Yuji Suzuki
Keyword(s):  
Heat Transfer ◽  
Pressure Loss ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Phase Flow ◽  
Flow Conditions ◽  
Two Phase ◽  
Inlet Flow ◽  
Annular Flows ◽  
Inlet Conditions

In the present study, the effects of inlet geometry on the microscale two-phase flow patterns have been examined. The relationships among the flow pattern, the void fraction, the pressure loss and the heat transfer coefficient have been also investigated under different inlet flow conditions. At the inlet, a stainless steel tube is inserted into the micro glass tube, of which inner diameter is 300 and 600 μm. The gas and liquid paths and the diameter of the inner tube are interchangeable. The flow patterns are recorded at the inlet and also in the developed region in the micro tubes. The flow patterns observed in the 600 μm tube are bubbly, slug, churn and annular flows, while bubbly and churn flows are not present in the 300 μm tube. For bubbly and slug flows, bubble formation process is found to be strongly affected by the inlet conditions. Accordingly, the pressure loss as well as the heat transfer rate are changed. In addition, the bubble size is not uniquely determined; bubbles of different sizes are observed in repeated experiments under the same inlet flow conditions. On the other hand, for churn and annular flows, the flow patterns are not affected by the inlet conditions.

Study of single-particle residence time in impulse, symmetric and asymmetric coaxial impinging streams

2019 ◽  
Vol 342 ◽  
pp. 118-130
Author(s):  
Xueqing Liu ◽  
Song Yue ◽  
Luyi Lu ◽  
Wei Gao ◽  
Jianlan Li
Keyword(s):  
Residence Time ◽  
Single Particle ◽  
Particle Residence Time

Precipitation and filtration of zinc, magnesium, copper and aluminium hydroxides

1982 ◽  
Vol 47 (12) ◽  
pp. 3362-3370
Author(s):  
Otakar Söhnel ◽  
Eva Matějčková
Keyword(s):  
Residence Time ◽  
Mean Residence Time ◽  
Filtration Resistance ◽  
Filtration Pressure ◽  
Bed Porosity ◽  
The Mean ◽  
Filtration Properties

Filtration properties of batchwise precipitated suspensions of Zn(OH)2, Mg(OH)2 and Cu(OH)2 and continuously precipitated Al(OH)3 were studied. For batchwise precipitated suspensions was verified the theoretically predicted dependence of specific filtration resistance on initial supersaturation and for the continuously precipitated Al(OH)3 the relation between the specific filtration resistance and the mean residence time of suspension in the reactor. Dependences were also recorded between the bed porosity and concentration of precipitated solutions, specific filtration resistance and used filtration pressure and the effect of aging of the batchwise precipitated suspension of Mg(OH)2on its filtration properties. The used CST method for determination of filtration characteristics of Zn(OH)2 suspension was also studied.

scholarly journals Continuous citrate‐capped gold nanoparticle synthesis in a two‐phase flow reactor

2021 ◽  
Author(s):  
Spyridon Damilos ◽  
Ioannis Alissandratos ◽  
Luca Panariello ◽  
Anand N. P. Radhakrishnan ◽  
Enhong Cao ◽  
...  
Keyword(s):  
Particle Size ◽  
Gold Nanoparticles ◽  
Residence Time ◽  
Flow Reactor ◽  
Phase Flow ◽  
Continuous Manufacturing ◽  
Two Phase ◽  
Process Yield ◽  
Au Nps ◽  
Manufacturing Platform

AbstractA continuous manufacturing platform was developed for the synthesis of aqueous colloidal 10–20 nm gold nanoparticles (Au NPs) in a flow reactor using chloroauric acid, sodium citrate and citric acid at 95 oC and 2.3 bar(a) pressure. The use of a two-phase flow system – using heptane as the continuous phase – prevented fouling on the reactor walls, while improving the residence time distribution. Continuous syntheses for up to 2 h demonstrated its potential application for continuous manufacturing, while live quality control was established using online UV-Vis photospectrometry that monitored the particle size and process yield. The synthesis was stable and reproducible over time for gold precursor concentration above 0.23 mM (after mixing), resulting in average particle size between 12 and 15 nm. A hydrophobic membrane separator provided successful separation of the aqueous and organic phases and collection of colloidal Au NPs in flow. Process yield increased at higher inlet flow rates (from 70 % to almost 100 %), due to lower residence time of the colloidal solution in the separator resulting in less fouling in the PTFE membrane. This study addresses the challenges for the translation of the synthesis from batch to flow and provides tools for the development of a continuous manufacturing platform for gold nanoparticles.Graphical abstract

Nitrogen use efficiency: does a trade-off exist between the N productivity and the mean residence time within species?

2008 ◽  
Vol 56 (3) ◽  
pp. 272 ◽  
Author(s):  
Zhi Y. Yuan ◽  
Han Y. H. Chen ◽  
Ling H. Li
Keyword(s):  
Residence Time ◽  
Nitrogen Use Efficiency ◽  
Mean Residence Time ◽  
Negative Relationship ◽  
Controlled Experiments ◽  
Nitrogen Use ◽  
Trade Off ◽  
N Supply ◽  
Use Efficiency ◽  
The Mean

Nitrogen use efficiency (NUE) can be divided into two components, i.e. N productivity (A) and the mean residence time (MRT). Controlled experiments indicate that there is not a trade-off between A and MRT within species, but this theory has not been well tested in field conditions. Here, we studied the A, MRT and NUE of Stipa krylovii Roshev. in a grassland over 4 years of N fertilisation experimentation. The three parameters (A, MRT and NUE) were significantly related to soil N supply and there was a negative relationship between A and MRT within this species (r = –0.775, P < 0.05), i.e. plants with higher A had lower MRT. Our results showed a trade-off between A and MRT within this Stipa species and this observed trade-off was attributed to different responses of A and MRT to soil fertility.

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