scholarly journals Hydrodynamic analysis of a liquid-solid fluidized bed via cfd-dem simulations, stability analysis, and tomography

2021 ◽  
Author(s):  
Hussein Zbib
Keyword(s):  
Stability Analysis ◽  
Fluidized Bed ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Percentage Error ◽  
Particle Interactions ◽  
Particle Volume ◽  
Computational Fluid Dynamics Cfd ◽  
The Difference ◽  
Dem Model

A coupled computational fluid dynamics (CFD) and discrete element method (DEM) model was developed to analyze the fluid-particle and particle-particle interactions in a 3D liquid-solid fluidized bed (LSFB). The CFD-DEM model was validated using the Electrical Resistance Tomography (ERT) experimental method. ERT was employed to measure the bed-averaged particle volume fraction (BPVF) of 0.002 m glass beads fluidized with water for various particle numbers and flow rates. It was found that simulations employing the combination of the Gidaspow drag model with pressure gradient and virtual mass forces provided the least percentage error between experiments and simulations. It was also found that contact parameters must be calibrated to account for the particles being wet. The difference between simulations and experiments was 4.74%. The CFD-DEM model was also employed alongside stability analysis to investigate the hydrodynamic behavior within the LSFB and the intermediate flow regime for all cases studied.

scholarly journals Hydrodynamic analysis of a liquid-solid fluidized bed via cfd-dem simulations, stability analysis, and tomography

2021 ◽  
Author(s):  
Hussein Zbib
Keyword(s):  
Stability Analysis ◽  
Fluidized Bed ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Percentage Error ◽  
Particle Interactions ◽  
Particle Volume ◽  
Computational Fluid Dynamics Cfd ◽  
The Difference ◽  
Dem Model

A coupled computational fluid dynamics (CFD) and discrete element method (DEM) model was developed to analyze the fluid-particle and particle-particle interactions in a 3D liquid-solid fluidized bed (LSFB). The CFD-DEM model was validated using the Electrical Resistance Tomography (ERT) experimental method. ERT was employed to measure the bed-averaged particle volume fraction (BPVF) of 0.002 m glass beads fluidized with water for various particle numbers and flow rates. It was found that simulations employing the combination of the Gidaspow drag model with pressure gradient and virtual mass forces provided the least percentage error between experiments and simulations. It was also found that contact parameters must be calibrated to account for the particles being wet. The difference between simulations and experiments was 4.74%. The CFD-DEM model was also employed alongside stability analysis to investigate the hydrodynamic behavior within the LSFB and the intermediate flow regime for all cases studied.

Computational Investigation of Hydrodynamics in a Turbulent Fluidized Bed of FCC Particles

2012 ◽  
Vol 550-553 ◽  
pp. 2903-2907
Author(s):  
Jian Chang ◽  
Kai Zhang
Keyword(s):  
Fluidized Bed ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Computational Investigation ◽  
Dense Phase ◽  
Particle Volume ◽  
Turbulent Fluidized Bed ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method ◽  
Superficial Gas Velocity

The hydrodynamics in a high and narrow turbulent fluidized bed of FCC particles is investigated by using computational fluid dynamics (CFD) method. The axial bed density, particle volume fraction and particle velocity in the fluidized bed are predicted and compared with the experiments. The results indicate that there exist two different coexisting regions in the bed: a bottom dense and an upper dilute region. As increasing superficial gas velocity, bed density decreases in the dense phase whilst increases in the dilute phase. In this high and narrow turbulent fluidized bed, however, the bed density decreases sharply even in the dense phase because of the wall restriction. The hydrodynamics resembles slug flow at the initial fluidization stage; as a steady fluidization is achieved, the fluidized bed produces larger bubbles than the conventional one.

scholarly journals Characterization of Particle Flow in a Free-Falling Solar Particle Receiver

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Clifford K. Ho ◽  
Joshua M. Christian ◽  
David Romano ◽  
Julius Yellowhair ◽  
Nathan Siegel ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Numerical Models ◽  
Particle Volume Fraction ◽  
Particle Flow ◽  
Particle Interactions ◽  
Particle Volume ◽  
Power Cycles ◽  
Particle Velocities ◽  
Free Falling ◽  
Measured Particle

Falling particle receivers are being evaluated as an alternative to conventional fluid-based solar receivers to enable higher temperatures and higher efficiency power cycles with direct storage for concentrating solar power (CSP) applications. This paper presents studies of the particle mass flow rate, velocity, particle-curtain opacity and density, and other characteristics of free-falling ceramic particles as a function of different discharge slot apertures. The methods to characterize the particle flow are described, and results are compared to theoretical and numerical models for unheated conditions. Results showed that the particle velocities within the first 2 m of release closely match predictions of free-falling particles without drag due to the significant amount of air entrained within the particle curtain, which reduced drag. The measured particle-curtain thickness (∼2 cm) was greater than numerical simulations, likely due to additional convective air currents or particle–particle interactions neglected in the model. The measured and predicted particle volume fraction in the curtain decreased rapidly from a theoretical value of 60% at the release point to less than 10% within 0.5 m of drop distance. Measured particle-curtain opacities (0.5–1) using a new photographic method that can capture the entire particle curtain were shown to match well with discrete measurements from a conventional lux meter.

Numerical Simulation of the Flow Characteristics of 35t/h Internally Circulating Fluidized Bed

2014 ◽  
Vol 529 ◽  
pp. 272-276
Author(s):  
Yu Lin Chen ◽  
Qing Wang ◽  
Cong Cong Liu ◽  
Jian Xin Ge
Keyword(s):  
Fluidized Bed ◽  
Oil Shale ◽  
Circulating Fluidized Bed ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Flow Characteristics ◽  
Circulating Fluidized Bed Boiler ◽  
Particle Volume ◽  
Eulerian Model ◽  
Recirculation Flow

The gas-solid flow characteristics of the 35t/h oil shale-combustion circulating fluidized bed boiler (Developed by Wangqing Longteng Energy Development Co., Ltd) was simulated using Eulerian-Eulerian model (EEM), which was based on the kinetic theory of granular. The distribution of particle volume fraction and the distribution of particle velocity revealed the mechanism of the internal recirculation flow of particles in the furnace. The simulation results provided a reference for the flow structure optimization of the inner circulating fluidized bed and the enlargement of the inner circulating fluidized bed boiler.

scholarly journals Gelation of Anisotropic Colloids with Short-Range Attraction

2020 ◽  
Vol 36 (1) ◽  
Author(s):  
Dang Minh Triet ◽  
Truong Quoc Tuan ◽  
Tran Van Thien
Keyword(s):  
Volume Fraction ◽  
Casimir Effect ◽  
Particle Volume Fraction ◽  
Building Blocks ◽  
Colloidal Gels ◽  
Particle Interactions ◽  
Particle Volume ◽  
Jones Potential ◽  
Structural Modifications ◽  
Key Factor

Gels are dilute connected networks that form solids at very low particle volume fraction with rich rheological properties. The kinetic process of gelation is central to understand the flow of complex fluids. Here, we report a simulation study of colloidal gelation formed by anisotropic colloids with attractive Lennard-Jones potential. These forces quasi-model the critical Casimir effect far from the critical solvent fluctuations acting on colloidal patches. By tuning the depths of the patch-to-patch particle interactions and the selected colloidal patches, we dynamically arrest the colloids to form gels. We find that thermal density fluctuation is the key factor to activate colloidal cluster space spanning: the balance between clustering and break-up mechanism plays a major role in the gelation process of anisotropic systems. These results offer new opportunities for studying the structural modifications of colloidal gels formed by anisotropic particles, and shed light on non-equilibrium behavior of anisotropic colloidal building blocks.

scholarly journals Study on Microstructure Effect of Carbon Black Particles in Filled Rubber Composites

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Li Hong Huang ◽  
Xiaoxiang Yang ◽  
Jianhong Gao
Keyword(s):  
Particle Size ◽  
Carbon Black ◽  
Polymer Nanocomposites ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Uniaxial Tensile ◽  
Particle Volume ◽  
Carbon Particles ◽  
The Difference ◽  
Microstructure Effect

The cross sections of blended natural/styrene-butadiene (NSBR) composites filled with different volume fractions of carbon particles were observed using a Quanta 250 scanning electron microscope. In addition, the sizes and distributions of the carbon particles were analyzed using Nano Measurer. A two-dimensional representative volume element model (RVE) for a rubber composite reinforced with circular carbon particles was established, and the uniaxial tensile behaviors of polymer nanocomposites with different particle size distribution patterns were simulated using the ABAQUS software. The results showed the following. (1) For the random models, if the difference of particle size was larger and particle distance was closer, stress distribution would be denser as well as the stress concentration would become greater. However, if the difference of particle size was small, for the case of same particle volume fraction, the particle size has little influence on the macromechanical properties whether the average size is large or small. (2) The correlation between the volume fraction and distribution of the carbon particles revealed that when the volume fraction of carbon black particles was larger than 12%, clusters between carbon particles in the polymer nanocomposites could not be avoided and the modulus of the composites increased with an increase in the cluster number.

scholarly journals Performance improvement of double-tube gas cooler in CO2 refrigeration system using nanofluids

2015 ◽  
Vol 19 (1) ◽  
pp. 109-118 ◽  
Author(s):  
Jahar Sarkar
Keyword(s):  
Performance Improvement ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Cooling Capacity ◽  
Inlet Temperature ◽  
Refrigeration Cycle ◽  
Particle Volume ◽  
Transcritical Carbon Dioxide ◽  
The Given ◽  
Theoretical Analyses

The theoretical analyses of the double-tube gas cooler in transcritical carbon dioxide refrigeration cycle have been performed to study the performance improvement of gas cooler as well as CO2 cycle using Al2O3, TiO2, CuO and Cu nanofluids as coolants. Effects of various operating parameters (nanofluid inlet temperature and mass flow rate, CO2 pressure and particle volume fraction) are studied as well. Use of nanofluid as coolant in double-tube gas cooler of CO2 cycle improves the gas cooler effectiveness, cooling capacity and COP without penalty of pumping power. The CO2 cycle yields best performance using Al2O3-H2O as a coolant in double-tube gas cooler followed by TiO2-H2O, CuO-H2O and Cu-H2O. The maximum cooling COP improvement of transcritical CO2 cycle for Al2O3-H2O is 25.4%, whereas that for TiO2-H2O is 23.8%, for CuO-H2O is 20.2% and for Cu-H2O is 16.2% for the given ranges of study. Study shows that the nanofluid may effectively use as coolant in double-tube gas cooler to improve the performance of transcritical CO2 refrigeration cycle.

A simulation and experimental study on particle volume fraction of PMMA suspension in centrifugal fields

2021 ◽  
Author(s):  
Yosephus Ardean Kurnianto Prayitno ◽  
Tong Zhao ◽  
Yoshiyuki Iso ◽  
Masahiro Takei
Keyword(s):  
Experimental Study ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Particle Volume
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