scholarly journals Numerical Simulation and Experimental Research on Coal Ash Collecting and Grading System

2014 ◽  
Vol 2014 ◽  
pp. 1-12
Author(s):  
Yuanhua Xie ◽  
Xianjin Li ◽  
Liwei Wang ◽  
Hong Yu ◽  
Bing Bai ◽  
...  
Keyword(s):  
Separation Efficiency ◽  
Economic Value ◽  
Coal Ash ◽  
Grading System ◽  
Two Phase ◽  
Optimal Experiment ◽  
Median Diameter ◽  
Fluent Software ◽  
Theoretical Results ◽  
Separation Parameters

The grading separation of coal ash can not only increase its economic value but also decrease its pollution to environment. Based on the jet-attracting flow technology and the gas-solid two-phase flow theory, the force and motion of coal ash particles in airflow were studied firstly. Focused on single coal ash particle, Matlab software was used to simulate the force conditions and separation parameters of various diameter coal ash particles in airflow. Fluent software was used to simulate the nozzle fluidization domain shape and to determine optimal jet flux. According to the theoretical results, a coal ash collecting and grading system was developed. Using the separation efficiency as the evaluation index, the optimal experiment parameters of jet flux, attracting flux, and separation time were obtained. At last, the calculated results and experimental results of coal ash particles median diameter from the first grading separation exit under various attracting fluxes were compared. The reasons that could cause the errors were discussed. This study has significant practical meaning and application value on coal ash collecting and grading separation.

Experimental and Numerical Investigation of Air-Particle Two-Phase Flow in Centrifugal Separator

2000 ◽  
Author(s):  
H. J. Kang ◽  
B. Zheng ◽  
C. X. Lin ◽  
M. A. Ebadian
Keyword(s):  
Velocity Distribution ◽  
Separation Efficiency ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Tangential Direction ◽  
Cylinder Surface ◽  
Centrifugal Separator ◽  
Two Phase ◽  
Dust Collection ◽  
Numerical Solver

Abstract The velocity distributions inside a centrifugal separator with outside and inside diameters of 152.4 mm (6″) and 76.2 mm (3″), respectively, have been investigated experimentally and numerically to obtain optimum separation efficiency. Two 12.7 mm (1/2-inch) holes were drilled on the external surface of the separator to measure the velocity distribution in the separator. Two direction velocities (tangential direction along the cylinder surface and axial along the vertical direction) were measured to compare with the numerical simulation results. A 6060P Pitot probe was employed to obtain the velocity distribution. The dust samples (a mixture of steel particle and dust) from the dust collection box were analyzed using a Phillips XL30 Scanning Electron Microscope. FLUENT code is used as the numerical solver for this fully three-dimensional problem. The fluid flow in the separator is assumed to be steady and incompressible turbulent flow. The standard k–ε model was employed in this study. Non-uniform, unstructured grids are chosen to discretize the entire computation domain. Almost 100,000 cells are used to discretize the whole separator. The constant velocity profile is imposed on the inlet plane. The pressure boundary condition is adopted at outlet plane. Comparing the velocity distribution and separation efficiency from the experiment and the numerical modeling shows that the experimental results and the estimated data agree fairly well and with a deviation within ±10%.

scholarly journals Feasibility Study on Downhole Gas–Liquid Separator Design and Experiment Based on the Phase Isolation Method

2021 ◽  
Vol 11 (21) ◽  
pp. 10496
Author(s):  
Yuntong Yang ◽  
Zhaoyu Jiang ◽  
Lianfu Han ◽  
Wancun Liu ◽  
Xingbin Liu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Gas Phase ◽  
Separation Efficiency ◽  
Dynamic Test ◽  
Phase Flow ◽  
Total Flow ◽  
Total Flow Rate ◽  
Two Phase ◽  
Oil Gas ◽  
Liquid Separator

As oil exploitation enters its middle and late stages, formation pressure drops, and crude oil degases. In production profile logging, the presence of the gas phase will affect the initial oil–water two-phase flowmeter’s flow measurement results. In order to eliminate gas-phase interference and reduce measurement costs, we designed a downhole gas–liquid separator (DGLS) suitable for low flow, high water holdup, and high gas holdup. We based it on the phase isolation method. Using a combination of numerical simulation and fluid dynamic measurement experiments, we studied DGLS separation efficiency separately in the two cases of gas–water two-phase flow and oil–gas–water three-phase flow. Comparative analysis of the numerical simulation calculation and dynamic test results showed that: the VOF model constructed based on k−ε the equation is nearly identical to the dynamic test, and can be used to analyze DGLS separation efficiency; the numerical simulation results of the gas–water two-phase flow show that when the total flow rate is below 20 m3/d, the separation efficiency surpasses 90%. The oil–gas–water three-phase’s numerical simulation results show that the oil phase influences separation efficiency. When the total flow rate is 20 m3/d–50 m3/d and gas holdup is low, the DGLS’s separation efficiency can exceed 90%. Our experimental study on fluid dynamics measurement shows that the DGLS’s applicable range is when the gas mass is 0 m3/d~15 m3/d, and the water holdup range is 50%~100%. The research presented in this article can provide a theoretical basis for the development and design of DGLSs.

scholarly journals The Influence of Combined Turbulators on the Hydraulic-Thermal Performance and Exergy Efficiency of MWCNT-Cu/Water Nanofluid in a Parabolic Solar Collector: A Numerical Approach

2021 ◽  
Vol 9 ◽  
Author(s):  
Yacine Khetib ◽  
Ammar Melaibari ◽  
Radi Alsulami
Keyword(s):  
Solar Collector ◽  
Volume Fraction ◽  
Numerical Approach ◽  
Exergy Efficiency ◽  
Multiphase Model ◽  
Two Phase ◽  
Simpler Algorithm ◽  
Fluent Software ◽  
Parabolic Geometries ◽  
Volume Method

The present research benefits from the finite volume method in investigating the influence of combined turbulators on the thermal and hydraulic exergy of a parabolic solar collector with two-phase hybrid MWCNT-Cu/water nanofluid. All parabolic geometries are produced using DesignModeler software. Furthermore, FLUENT software, equipped with a SIMPLER algorithm, is applied for analyzing the performance of thermal and hydraulic, and exergy efficiency. The Eulerian–Eulerian multiphase model and k-ε were opted for simulating the two-phase hybrid MWCNT-Cu/water nanofluid and turbulence model in the collector. The research was analyzed in torsion ratios from 1 to 4, Re numbers from 6,000 to 18,000 (turbulent flow), and the nanofluid volume fraction of 3%. The numerical outcomes confirm that the heat transfer and lowest pressure drop are relevant to the Re number of 18,000, nanofluid volume fraction of 3%, and torsion ratio of 4. Furthermore, in all torsion ratios, rising Re numbers and volume fraction lead to more exergy efficiency. The maximum value of 26.32% in the exergy efficiency was obtained at a volume fraction of 3% and a torsion ratio of 3, as the Re number goes from 60,000 to 18,000.

Drop Coagulation in Cross-Over Pipe Flows of Wet Steam

1979 ◽  
Vol 21 (5) ◽  
pp. 357-360 ◽  
Author(s):  
J. J. E. Williams ◽  
R. I. Crane
Keyword(s):  
Drop Size ◽  
Chemical Engineering ◽  
Numerical Technique ◽  
Wet Steam ◽  
Coagulation Rate ◽  
Two Phase ◽  
Size Spectra ◽  
Pipe Flows ◽  
The Core ◽  
Median Diameter

A numerical technique is developed for predicting the evolution of drop-size spectra in turbulent, two-phase pipe flows. While relevant to many chemical engineering processes, it is applied here to the crossover pipes of a nuclear wet-steam turbine. Valid expressions for turbulent coagulation rate in the cross-over pipes are available only for drops below about 10 μm diameter in the core flow, and for those exceeding about 20 μm near the pipe wall. Using these expressions, it is found that the rapid formation of large drops in the core allows prediction for only a small fraction of the typical residence time in the pipe, but near the wall the volume median diameter of an initial 20 μm monodispersion can double in 100 ms. Further work is required to validate the technique and extend it to handle the intervening ranges of drop size and turbulence parameters.

Computational and Experimental Investigation of the Vertical Flash Tank Separator Part 1: Effect of Parameters on Separation Efficiency

2019 ◽  
Vol 27 (01) ◽  
pp. 1950005 ◽  
Author(s):  
Raid Ahmed Mahmood ◽  
David Buttsworth ◽  
Ray Malpress
Keyword(s):  
Separation Efficiency ◽  
Fluid Dynamic ◽  
Effective Area ◽  
Working Fluid ◽  
Cfd Simulations ◽  
Liquid Separation ◽  
Two Phase ◽  
Flash Tank ◽  
Tank Design ◽  
The Heat Transfer Coefficient

The flash tank separator is one of the most important components that can be used to improve the performance of a refrigeration cycle by separating the liquid from the gas–liquid two-phase flow and providing the evaporator with only liquid refrigerant. This technique increases the effective area and enhances the heat transfer coefficient in the evaporator. To optimize the size of the vertical flash tank separator for obtaining high separation efficiency, the effect of the size of the vertical flash tank separator needs to be considered. This paper investigates the effect of the size on the liquid separation efficiency of the vertical flash tank separator. This paper also assesses the usefulness of Computational Fluid Dynamic (CFD) in flash tank design, and this is achieved through experiments and simulations on a range of relevant configurations using water as the working fluid. The results revealed that the size has a significant effect on the liquid separation efficiency, as the highest value was achieved by the largest size (VFT-V5). The CFD simulations give a good agreement with the experiments; all the simulations underestimated the liquid separation efficiency by approximately 0.02 over the range of conditions tested.

scholarly journals Numerical Simulation of Solid Particle Erosion in Aluminum Alloy Spool Valve

2019 ◽  
Vol 2019 ◽  
pp. 1-16 ◽  
Author(s):  
Jin-gang Liu ◽  
Gao-sheng Wang ◽  
Tian-heng Peng ◽  
Sheng-qiang Jiang
Keyword(s):  
Particle Size ◽  
Aluminum Alloy ◽  
Prediction Model ◽  
Particle Shape ◽  
Two Phase ◽  
Wear Prediction ◽  
Valve Body ◽  
Fluent Software ◽  
Improved Design ◽  
Spool Valve

Aluminum alloy spool valve body material is prone to severe wear on the wall under the condition of oil contamination. Aiming at this problem, combined with the theory of liquid-solid two-phase flow and erosion wear, the wear prediction model of aluminum alloy sliding valve wall is established based on computational fluid dynamics, and the effects of turbulence and wall materials, particle size distribution, and particle shape on particle motion are discussed. The calculation of the wear prediction model is done with Fluent software. This study predicts the wear of the wall under actual working conditions and calculates the influence of particle size, particle shape, and pressure difference on the wall wear of the aluminum alloy sliding valve. The research results have certain significance for the maintenance and upkeep of aluminum alloy sliding valve wall, improved design, and life prediction.

A Method for Extracting the Time Delay From the Unsteady and Quasi-Steady Fluidelastic Forces in Two-Phase Flow

2013 ◽  
Author(s):  
Teguewinde Sawadogo ◽  
Njuki Mureithi
Keyword(s):  
Time Delay ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Fluid Forces ◽  
Void Fractions ◽  
Fluidelastic Instability ◽  
Measured Time ◽  
Unsteady Fluid ◽  
Theoretical Results

The time delay is a key parameter for modeling fluidelastic instability, especially the damping controlled mechanism. It can be determined experimentally by measuring directly the time lag between the tube motion and the induced fluid forces. The fluid forces may be obtained by integrating the pressure field around the moving tube. However, this method faces certain difficulties in two-phase flow since the high turbulence and the non-uniformity of the flow may increase the randomness of the measured force. To overcome this difficulty, an innovative method for extracting the time delay inherent to the quasi-steady model for fluidelastic instability is proposed in this study. Firstly, experimental measurements of unsteady and quasi-static fluid forces (in the lift direction) acting on a tube subject to two-phase flow were conducted. The unsteady fluid forces were measured by exciting the tube using a linear motor. These forces were measured for a wide range of void fraction, flow velocities and excitation frequencies. The experimental results showed that the unsteady fluid forces could be represented as single valued function of the reduced velocity (flow velocity reduced by the excitation frequency and the tube diameter). The time delay was determined by equating the unsteady fluid forces with the quasi-static forces. The results given by this innovative method of measuring the time delay in two-phase flow were consistent with theoretical expectations. The time delay could be expressed as a linear function of the convection time and the time delay parameter was determined for void fractions ranging from 60% to 90%. Fluidelastic instability calculations were also performed using the quasi-steady model with the newly measured time delay parameter. Previously conducted stability tests provided the experimental data necessary to validate the theoretical results of the quasi-steady model. The validity of the quasi-steady model for two-phase flow was confirmed by the good agreement between its results and the experimental data. The newly measured time delay parameter has improved significantly the theoretical results, especially for high void fractions (90%). However, the model could not be verified for void fractions lower or equal to 50% due to the limitation of the current experimental setup. Further studies are consequently required to clarify this point. Nevertheless, this model can be used to simulate the flow induced vibrations in steam generators’ tube bundles as their most critical parts operate at high void fractions (≥ 60%).

scholarly journals Simulation and experimental research based on carrier gas flow rate on the influence of four-channel coaxial nozzle flow field

2020 ◽  
pp. 002029402096423
Author(s):  
Shi Rui Guo ◽  
Qian Qian Yin ◽  
Lu Jun Cui ◽  
Xiao Lei Li ◽  
Ying Hao Cui ◽  
...  
Keyword(s):  
Flow Field ◽  
Gas Flow ◽  
Simulation Analysis ◽  
Two Phase ◽  
Carrier Gas ◽  
Coaxial Nozzle ◽  
Convergence Point ◽  
Flow Convergence ◽  
Fluent Software ◽  
Carrier Gas Flow

This paper investigates the influence of carrier gas flow on the external flow field of coaxial powder feeding nozzle. FLUENT software was adopted to establish gas-solid two-phase flow. The simulation of powder stream field under different carrier gas flow was also carried out. Results show that the larger the flow of carrier gas is, the higher the gas flow field velocity at the nozzle outlet is. At the same time, the concentration at the convergence point is lower, and the convergent point is maintained at 0.015 m. Under the condition of 4 L/min, the powder flow convergence is good. When it exceeds 4 L/min, powder spot diameter increases. The experiment of powder aggregation and laser cladding forming were completed, which shows that the forming effect is the best one under the condition of 4 L/min. It is consistent with the simulation analysis results and has a high reference to the optimization of the process parameters of coaxial nozzle.

Numerical Simulation of Double Inlet Cylinder Cyclone Using CFD

2013 ◽  
Vol 275-277 ◽  
pp. 558-561
Author(s):  
Xiao Ming Yuan ◽  
Hui Jun Zhao ◽  
Jing Yi Qu
Keyword(s):  
Flow Field ◽  
Volume Fraction ◽  
Separation Efficiency ◽  
Separation Performance ◽  
Two Phase ◽  
Phase Volume Fraction ◽  
Fluid Field ◽  
Cylindrical Cyclone ◽  
Discrete Phase ◽  
New Type

Designed a new type of double inlet cylindrical cyclone. For search the separation performance in a cylindrical cyclone. By use of CFD，applied the RSM turbulence model and Euler two-phase flow method and ASM which to simulate separation process and flow field within a double inlet cylindrical cyclone. Then compared with the single inlet cyclone，obtained velocity distribution. Analyzed the differences of discrete phase volume fraction between different viscosity. The results show that the new-style cyclone caught more stable fluid field and higher separation efficiency. And when the viscosity is about 0.75 kg/m•s， the separation efficiency and stability of the oil core is higher. Preliminary flow field law is shown up.

Comparison of Single-Valued Forecasts in a User-Oriented Framework

2020 ◽  
Vol 35 (3) ◽  
pp. 1067-1080
Author(s):  
Michael Foley ◽  
Nicholas Loveday
Keyword(s):  
Numerical Weather Prediction ◽  
Extreme Events ◽  
Prediction Models ◽  
Weather Prediction ◽  
Economic Value ◽  
Extreme Conditions ◽  
Single Model ◽  
Consensus Forecasts ◽  
Theoretical Results ◽  
Numerical Weather Prediction Models

Abstract We compare single-valued forecasts from a consensus of numerical weather prediction models to forecasts from a single model across a range of user decision thresholds and sensitivities, using the relative economic value framework, and present this comparison in a new graphical format. With the help of a simple linear error model, we obtain theoretical results and perform synthetic calculations to gain insights into how the results relate to the characteristics of the different forecast systems. We find that multimodel consensus forecasts are more beneficial for users interested in decisions near the climatological mean, due to their reduced spread of errors compared to the constituent models. Single model forecasts may present greater benefit for users sensitive to extreme events if the forecasts have smaller conditional biases than the consensus forecasts and hence better resolution of such events. The results support use of consensus averaging approaches for single-valued forecast services in typical conditions. However, it is hard to cater for all user sensitivities in more extreme conditions. This underscores the importance of providing probability-based services for unusual conditions.

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