A Numerical Study of Particle Deposition Through Fuel Pebble Bed in HTGR

2018 ◽  
Author(s):  
Qi Sun ◽  
Gang Zhao ◽  
Wei Peng ◽  
Suyuan Yu
Keyword(s):  
Particle Deposition ◽  
Numerical Study ◽  
Three Dimensional ◽  
Intensity Change ◽  
Discrete Phase Model ◽  
Pebble Bed ◽  
Deposition Fraction ◽  
Discrete Phase ◽  
Face Centered ◽  
Fuel Elements

The study on the deposition of graphite dust is significant to the safety of High-Temperature Gas-cooled Reactor (HTGR) due to potential accident such as localized hot-spots and intensity change which is caused by the graphite dust generated by abrasion of fuel elements. Based on the steady flow and three-dimensional face centered structures of fuel pebble bed, the discrete phase model (DPM) were applied to simulate trajectory of graphite dust in conditions of HTGR. To determinate the deposition of particle, the present study introduces a rebound condition with critical velocity by a user defined function. The particle trajectories show most of particle deposition can be summed up as the effect of backflow region, turbulent diffusion and inertial impact. The original trap condition overestimates the deposition fraction especially for large particles compared with involving rebound condition. In addition, the trend of deposition fraction shows as the dimeter of particle increases, deposition fraction decreases first and then increases.

Numerical study on the anti-snow performance of deflectors in the bogie region of a high-speed train using the discrete phase model

2018 ◽  
Vol 233 (2) ◽  
pp. 141-159 ◽  
Author(s):  
Guangjun Gao ◽  
Yan Zhang ◽  
Fei Xie ◽  
Jie Zhang ◽  
Kan He ◽  
...  
Keyword(s):  
High Speed ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Snow Accumulation ◽  
Phase Model ◽  
High Speed Train ◽  
Discrete Phase Model ◽  
Discrete Phase ◽  
Deflector Plate

In this paper, the three-dimensional unsteady Reynolds-averaged Navier-Stokes equations with an RNG double-equation turbulence model and a discrete phase model were used for the investigation of snow accumulation on the bogie of a high-speed train. Two kinds of deflector plates, one installed at the front end and the other at the rear end of the bogie, were proposed to reduce snow accumulation. The accuracy of the CFD methodology was validated against wind tunnel tests. The results showed that high-speed air will impact the plates where snow particles get accumulated. The snow covering on the bogie rarely drifts back into the bogie region with air. The amount of accumulating snow in the optimum models is reduced by 50.58% on average as compared to those in the original models. At the rear end of the bogie, the inclined deflector plate reduced snow accumulation by up to 10.91% compared to the vertical deflector plate.

scholarly journals STUDY OF CALCITE PRECIPITATION IN WELL CONDITIONS USING THE DDPM-DPM APPROACH

2021 ◽  
Vol 51 (2) ◽  
pp. 101-106
Author(s):  
Suellen Freire Rigatto da Cruz ◽  
Fabio De Assis Ressel Pereira ◽  
Daniel Da Cunha Ribeiro ◽  
André Leibsohn Martins ◽  
Oldrich Joel Romero
Keyword(s):  
Particle Deposition ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Computational Effort ◽  
Scale Formation ◽  
Discrete Phase Model ◽  
Calcite Precipitation ◽  
Discrete Phase ◽  
It Application ◽  
Calcium Carbonate Scale

The extraction of oil results in problems such as the scale formation in the various stages of the production process. The scale reduces all or part of the flow conduits, increasing the pressure drop and reducing oil production. In this work the three dimensional, transient, turbulent, biphasic problem is solved by combining the Dense Discrete Phase Model (DDPM) and Discrete Element Method (DEM), to analyze the influence of certain parameters on the particle deposition, which represents the calcium carbonate scale formation, inside the wall of a horizontal pipeline at well conditions. The obtained results show that particle deposition is higher at lower Reynolds numbers. The results also show that the use of DEM model is more representative, but due to the high computational effort required, it application in complex geometries must be carefully evaluated.

Effect of position of the fiber transport channel on fiber motion in the high-speed rotor

2021 ◽  
pp. 004051752110018
Author(s):  
Rui Hua Yang ◽  
Chuang He ◽  
Bo Pan ◽  
Hongxiu Zhong ◽  
Cundong Xu
Keyword(s):  
High Speed ◽  
Channel Model ◽  
Three Dimensional ◽  
Discrete Phase Model ◽  
Transport Channel ◽  
Rotor Spinning ◽  
Fiber Motion ◽  
Discrete Phase ◽  
Airflow Field ◽  
Fiber Transport

The task of the fiber transport channel (FTC) is to transport the fibers from the carding roller to the rotor. Its geometric position in the spinning machine has a strong influence on the characteristics of the airflow field and the trajectory of the fiber motion in both the rotor and the FTC. In this paper, a three-dimensional pumping rotor spinning channel model was established using ANSYS-ICEM-CFD software with three different positions of the FTC (positions a–c). Further, the simulations of air distribution were performed using Fluent software. In addition, the discrete phase model was used to fit the fiber motion trajectory in the rotor. The simulation results showed that among the three types of FTC, position b is the optimal condition. The gradients of airflow velocity in the channel at position b were greater than those of the other two positions, which is conducive to straightening of the fiber.

A numerical study of snow accumulation on the bogies of high-speed trains based on coupling improved delayed detached eddy simulation and discrete phase model

2018 ◽  
Vol 233 (7) ◽  
pp. 715-730 ◽  
Author(s):  
Mingyang Liu ◽  
Jiabin Wang ◽  
Huifen Zhu ◽  
Sinisa Krajnovic ◽  
Guangjun Gao
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Snow Accumulation ◽  
Phase Model ◽  
Detached Eddy Simulation ◽  
Discrete Phase Model ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Flow Mechanisms ◽  
Discrete Phase

A numerical simulation method based on the improved delayed detached eddy simulation coupled with a discrete phase model is used to study the influence of the snow on the performance of bogies of a high-speed train running in snowy weather. The snow particle trajectories, mass of snow packing on the bogie, and thickness of snow accumulation have been analyzed to investigate the flow mechanisms of snow accumulation on different parts of the bogies. The results show that the snow accumulation on the first bogie of the head vehicle is almost the same as that of the second bogie, but the total accumulated snow on the top side of the second bogie is more than 74% higher than that of the first bogie. Among all the components of the bogies, the motors were found to be strongly influenced by the snow accumulation. The underlying flow mechanisms responsible for the snow accumulations are discussed.

Unsteady Modeling of Powdered Activated Carbon Deposition on Collection Electrode of a Lab-Scale Electrostatic Precipitator (ESP)

2012 ◽  
Author(s):  
Yasmin Khakpour ◽  
Herek L. Clack
Keyword(s):  
Activated Carbon ◽  
Particle Deposition ◽  
Electrostatic Precipitator ◽  
Activated Carbons ◽  
Collection Efficiency ◽  
Continuous Phase ◽  
Powdered Activated Carbon ◽  
Computational Domain ◽  
Discrete Phase Model ◽  
Discrete Phase

Particulate sampling in the flue gas at the Electrostatic Precipitator (ESP) outlet during injection of powdered activated carbons (PACs) has provided strong anecdotal evidence indicating that injected PACs can penetrate the ESP in significant concentrations. The low resistivity of PAC is consistent with poor collection efficiency in an ESP and lab-scale testing has revealed significantly different collection behavior of PAC in an ESP as compared to fly ash. The present study illustrates the use of a commercial CFD package — FLUENT — to investigate precipitation of powdered activated carbon (PAC) in the presence and absence of electric field. The computational domain is designed to represent a 2-D wire-plate ESP channel. The governing equations include those covering continuous phase transport, electric potential, air ionization, and particle charging. The particles are tracked using a Lagrangian Discrete Phase Model (DPM). In addition, a custom user-defined function (UDF) uses a deforming boundary condition and a prescribed critical particle velocity to account for particle deposition and dust-cake growth on the electrodes. The effect of Electrohydrodynamics (EHD) induced flow on the ESP collection efficiency under various flow and particle characteristics as well as different ESP configurations are illustrated.

scholarly journals Effect of Air Exchange Rate on Particle Decay in a Cleanroom: A Numerical Study

2019 ◽  
Vol 111 ◽  
pp. 01037
Author(s):  
Yunus Emre Cetin ◽  
Mete Avci ◽  
Orhan Aydin
Keyword(s):  
Exchange Rate ◽  
Turbulence Model ◽  
Recovery Time ◽  
Numerical Study ◽  
Particle Dispersion ◽  
Discrete Phase Model ◽  
Governing Equations ◽  
Air Exchange Rate ◽  
Particle Decay ◽  
Discrete Phase

In this study, particle decay in a cleanroom is investigated numerically. A commercial CFD package, FLUENT, is used in the analysis. The governing equations are solved by using the k-å turbulence model. For particle dispersion, the discrete phase model (DPM) is applied. Four different air change rates (3-10-25-43 ACH) with three particle diameters (0,5-5-10 ìm) are considered. It is shown that 10 ACH satisfies the needs in terms of recovery time.

A Numerical Study on the Large Compressive Deformations of Closed-Celled Rubber Foams

2013 ◽  
Vol 444-445 ◽  
pp. 23-26
Author(s):  
Zhi Geng Fan
Keyword(s):  
Strain Energy ◽  
Potential Model ◽  
Numerical Study ◽  
Three Dimensional ◽  
Face Centered Cubic ◽  
Energy Potential ◽  
Compressive Stresses ◽  
Order Of Magnitude ◽  
Face Centered ◽  
In Cells

Three dimensional (3D) cubic models with spherical pores ranged as Face-Centered Cubic (FCC) lattices are constructed to simulate the microstructures of rubber foams with various relative densities. The Mooney-Rivlin strain energy potential model is adopted to characterize the hyperelasticity of the constituent solid from which the foams are made. Large compressive deformations of closed-celled rubber foams are calculated by the iterative algorithm. Numerical results show that with the decreasing of foam relative densities, the effects of air pressures in cells on foam compressive stresses increase. When the ratio of initial Yangs modulus of cell material to the initial air pressure in cells reaches 2 order of magnitude, the influence of air pressures in cells can neglect.

Numerical Study of the Deposition of Radioactive Nucleoids (Aerosol) in PWR Steam Generator

2021 ◽  
Author(s):  
Muhammad Aadil ◽  
Rab Nawaz ◽  
Ajmal Shah ◽  
Kamran Rasheed Qureshi
Keyword(s):  
Steam Generator ◽  
Numerical Study ◽  
Deposition Efficiency ◽  
Decontamination Factor ◽  
Radioactive Nuclide ◽  
Discrete Phase Model ◽  
Velocity Magnitude ◽  
Discrete Phase ◽  
Steam Generator Tubes ◽  
Secondary Side

Abstract This research presents numerical study of deposition efficiency and decontamination factor of radioactive nuclide in steam generator tubes of a typical 325 MWe PWR. To find out the deposition of aerosol, the discrete phase model (DPM) has been used. The flow has been characterized as compressible, adiabatic, turbulent and wall bounded. When steam generator tube gets ruptured, the radioactive nuclides can escape from primary side and create a radioactive field in the secondary side. This can be harmful for the personnel working at the plant. Therefore, in order to ensure the safety of the plant and personnel, it is important to study the particles deposition on the wall of steam generator tubes. In the present study, a CFD methodology has been first developed and validated with the published results. After methodology validation, it has been applied to the U-tube of a typical PWR steam generator. It has been observed that due to the action of centrifugal force near the bent, the velocity magnitude is high towards the inner wall and the flow separates at the bent entrance. Furthermore, the flow inside the tube is rotational with vortices throughout the domain due to the presence of the bent. Finally, the deposition efficiency and decontamination factor have been calculated and it has been observed that both increase with the increase in particle size due to inertial effects.

Numerical Calculation on the Influence of Missile Exhaust Plume with Mechanical Properties to the Double-Launch Box

2014 ◽  
Vol 978 ◽  
pp. 101-105
Author(s):  
Jing Li ◽  
Yi Jiang
Keyword(s):  
Three Dimensional ◽  
Engineering Application ◽  
Maximum Pressure ◽  
Common Phenomenon ◽  
Discrete Phase Model ◽  
Exhaust Plume ◽  
Discrete Phase ◽  
Unsteady Numerical Simulation ◽  
Multicomponent Model ◽  
Over Time

The adverse impact of the exhaust plume on the inner wall of the vertical launch box and the former friable lid of the adjacent launch box is a common phenomenon, which causes the deformation or damage of the launch container. By using the three-dimensional unsteady numerical simulation, discrete phase model and multicomponent model, the change of the pressure and temperature with time on many monitoring sites are analyzed. The results show that the pressure and the temperature on the edge of the inner wall significantly rise over time after 0.2s. The pressure on the centerline of the inner wall rises over time after 0.2s but the temperature gradually decreases. The maximum pressure on the former friable lid of the adjacent launch box peaks at 0.54s. The conclusion can be regarded as a theoretical reference for engineering application.

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