scholarly journals The influence of vapor on the particle transport in high humid neighborhood environment

2021 ◽  
Vol 2076 (1) ◽  
pp. 012043
Author(s):  
Dan Mei ◽  
Xuemei Xu
Keyword(s):  
Particle Transport ◽  
Street Canyon ◽  
Saturated Vapor ◽  
Flow Characteristics ◽  
Absolute Humidity ◽  
Neighborhood Environment ◽  
Computational Domain ◽  
Discrete Phase Model ◽  
Discrete Phase ◽  
Velocity Pressure

Abstract The particle transport characteristics have a significant effect on the exposure of residents and pedestrians to traffic pollutants in the street canyon. Around the lakeside environment, the diffusion of water vapor affects the flow characteristics of the gas mixture, which has a considerable influence on particle transport in the street canyon. A computational domain containing water bodies from which droplets were emitted by evaporation, a lakeside avenue and architectural groups were constructed. The RNG k-ε turbulence model and discrete phase model were applied to study the velocity, pressure, density of the airflow and particle transport characteristics in the street canyon with the absolute humidity increase (AHI) of 0, 3.8×10-4 g/kg, 1.7×10-3 g/kg, 3.1×10-3 g/kg. The saturated vapor pressure on the surface of droplets was modified by the pressure correction equation, which can limit the evaporation rate of the droplets. The simulation results demonstrated that, the diffusion of vapor could reduce the airflow velocity and increase the air pressure and density. The particle concentration in the street canyon increased with the AHI. Most of the pathogens in the air are transmitted with the flow of particle, and the study has some guiding significance to prevent the transmission of viruses.

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 Research on the flow characteristics of opening unit in the rotor spinning unit

2017 ◽  
Vol 25 (0) ◽  
pp. 18-24
Author(s):  
Yuzhen Jin ◽  
Shihe Zhu ◽  
Jingyu Cui ◽  
Jun Li ◽  
Zuchao Zhu
Keyword(s):  
Negative Pressure ◽  
Flow Characteristics ◽  
Axial Direction ◽  
Effective Area ◽  
Discrete Phase Model ◽  
Roller Speed ◽  
Rotor Spinning ◽  
Removal Process ◽  
Discrete Phase ◽  
Different Diameters

The opening unit is an important device in a rotor spinning unit to comb fibres and remove trash. In this paper, numerical simulation is carried out to study the flow structure in the rotor spinning channel and the trash removal process in the trash removal unit. Firstly the effect of the opening unit on the airflow field in the rotor channel is investigated by singlephase simulation. The result shows that the effective area for fibre conveyance enlarges as the absolute value of negative pressure at the outlet increases, while it decreases as the opening roller speed increases. However, the effect of the negative pressure and the opening roller speed on the length of the vortex in the axial direction is quite small. Secondly the trash separation process in the trash removal unit is simulated using the Discrete Phase Model (DPM). Suitable rotational speeds of particles of different diameters are acquired. These results could provide a valuable reference for parameter selection in the trash-removal process.

scholarly journals Analysis of Flow and Wear Characteristics of Solid–Liquid Two-Phase Flow in Rotating Flow Channel

Processes ◽  
2020 ◽  
Vol 8 (11) ◽  
pp. 1512
Author(s):  
Peng Wang ◽  
Xinyu Zhu ◽  
Yi Li
Keyword(s):  
Wear Rate ◽  
Flow Direction ◽  
Flow Characteristics ◽  
Discrete Phase Model ◽  
Rotating Disc ◽  
Two Phase ◽  
Wear Area ◽  
Severe Wear ◽  
Working Surface ◽  
Discrete Phase

To study the flow characteristics and the wear distribution of pumps at different rotation speeds, a rotating disc with three blades was designed for experiments. Numerical simulations were conducted using a computational fluid dynamics-discrete phase model (CFD–DPM) approach. The experimental and numerical results were compared, and the flow characteristics and wear behaviors were determined. As the speed increased, the particles at the blade working surface aggregated. The particle velocity gradually increased at the outlet of the channel. The severe wear areas were all located in the outlet area of the blade working surface, and the wear area extended toward the inlet area of the blade with increasing speed. The wear rate of the blade surface increased as the speed increased, and an area with a steady wear rate appeared at the outlet area of the blade. When the concentration was more than 8%, the severe wear areas were unchanged at the same speed. When the speed increased, the severe wear areas of the blade produced wear ripples, and the area of the ripples increased with increasing speed. The height difference between the ripples along the flow direction on the blade became larger as the speed increased.

Computational Analysis of Compressor Blade Erosion in a Wet Compression System

2016 ◽  
Author(s):  
Palani Kumar Chidambaram ◽  
Tae Hoon Song ◽  
In Won Kim ◽  
Kwon Hee Lee ◽  
Heuy Dong Kim
Keyword(s):  
Particle Diameter ◽  
Spray Parameters ◽  
Computational Domain ◽  
Water Droplets ◽  
Discrete Phase Model ◽  
Compressor Blades ◽  
Turbine Engine ◽  
Compression System ◽  
Discrete Phase ◽  
Wet Compression

In a gas turbine engine a wet compression system is installed to increase the net power output. However, this may erode compressor blades due to fine water droplets hitting the surface. In the present work, numerical investigations are carried out to study blade erosion by water droplets. The computational domain consists of a rotating blade jig on which four blades are mounted. This represents the simultaneous experiments being carried out. Sliding mesh method is used to incorporate rotary movement of the blades. Water is injected as spray using an impact-pin nozzle. Experimentally measured spray parameters like the flow rate, particle diameter, etc. are given as initial and boundary conditions in the simulations. Discrete Phase Model (DPM) is used to track the particles in the domain. Droplet parameters like average velocity, diameter and number of droplets hitting each cell on the blade surface are monitored. These parameters are then used to predict the rate of erosion on the surface. In this manuscript, the progresses in the prediction of blade erosion at various blade rotational speed (rpm) is reported.

Study on the Flow Characteristics of Shengli Oilfield Super Heavy Oil

2017 ◽  
Vol 10 (1) ◽  
pp. 69-78 ◽  
Author(s):  
Wang Shou-long ◽  
Li Ai-fen ◽  
Peng Rui-gang ◽  
Yu Miao ◽  
Fu Shuai-shi
Keyword(s):  
Pressure Drop ◽  
Pressure Gradient ◽  
Heavy Oil ◽  
Flow Characteristics ◽  
Fluid Viscosity ◽  
Linear Flow ◽  
Start Up ◽  
Non Linear ◽  
Core Permeability ◽  
Velocity Pressure

Objective:The rheological properties of oil severely affect the determination of percolation theory, development program, production technology and oil-gathering and transferring process, especially for super heavy oil reservoirs. This paper illustrated the basic seepage morphology of super heavy oil in micro pores based on its rheological characteristics.Methods:The non-linear flow law and start-up pressure gradient of super heavy oil under irreducible water saturation at different temperatures were performed with different permeable sand packs. Meanwhile, the empirical formulas between start-up pressure gradient, the parameters describing the velocity-pressure drop curve and the ratio of gas permeability of a core to fluid viscosity were established.Results:The results demonstrate that temperature and core permeability have significant effect on the non-linear flow characteristics of super heavy oil. The relationship between start-up pressure gradient of oil, the parameters representing the velocity-pressure drop curve and the ratio of core permeability to fluid viscosity could be described as a power function.Conclusion:Above all, the quantitative description of the seepage law of super heavy oil reservoir was proposed in this paper, and finally the empirical diagram for determining the minimum and maximum start-up pressure of heavy oil with different viscosity in different permeable formations was obtained.

scholarly journals Effects of Blade Parameters on the Flow Field and Classification Performance of the Vertical Roller Mill via Numerical Investigations

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Chang Liu ◽  
Zuobing Chen ◽  
Weili Zhang ◽  
Chenggang Yang ◽  
Ya Mao ◽  
...  
Keyword(s):  
Flow Field ◽  
Pressure Difference ◽  
Continuous Phase ◽  
Classification Performance ◽  
Field Analysis ◽  
Discrete Phase Model ◽  
Roller Mill ◽  
Discrete Phase ◽  
Vertical Roller ◽  
Classification Efficiency

The vertical roller mill is an important crushing and grading screening device widely used in many industries. Its classification efficiency and the pressure difference determine the entire producing capacity and power consumption, respectively, which makes them the two key indicators describing the mill performance. Based on the DPM (Discrete Phase Model) and continuous phase coupling model, the flow field characteristics in the vertical roller mill including the velocity and pressure fields and the discrete phase distributions had been analyzed. The influence of blade parameters like the shape, number, and rotating speed on the flow field and classification performance had also been comprehensively explored. The numerical simulations showed that there are vortices in many zones in the mill and the blades are of great significance to the mill performance. The blade IV not only results in high classification efficiency but also reduces effectively the pressure difference in the separator and also the whole machine. The conclusions of the flow field analysis and the blade effects on the classification efficiency and the pressure difference could guide designing and optimizing the equipment structure and the milling process, which is of great importance to obtain better overall performance of the vertical roller mill.

scholarly journals Enhanced discrete phase model for multiphase flow simulation of blood flow with high shear stress

2021 ◽  
Vol 104 (1) ◽  
pp. 003685042110080
Author(s):  
Zheqin Yu ◽  
Jianping Tan ◽  
Shuai Wang
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Multiphase Flow ◽  
Experimental Verification ◽  
Flow Simulation ◽  
Turbulence Models ◽  
Phase Model ◽  
Force Model ◽  
Discrete Phase Model ◽  
Discrete Phase

Shear stress is often present in the blood flow within blood-contacting devices, which is the leading cause of hemolysis. However, the simulation method for blood flow with shear stress is still not perfect, especially the multiphase flow model and experimental verification. In this regard, this study proposes an enhanced discrete phase model for multiphase flow simulation of blood flow with shear stress. This simulation is based on the discrete phase model (DPM). According to the multiphase flow characteristics of blood, a virtual mass force model and a pressure gradient influence model are added to the calculation of cell particle motion. In the experimental verification, nozzle models were designed to simulate the flow with shear stress, varying the degree of shear stress through different nozzle sizes. The microscopic flow was measured by the Particle Image Velocimetry (PIV) experimental method. The comparison of the turbulence models and the verification of the simulation accuracy were carried out based on the experimental results. The result demonstrates that the simulation effect of the SST k- ω model is better than other standard turbulence models. Accuracy analysis proves that the simulation results are accurate and can capture the movement of cell-level particles in the flow with shear stress. The results of the research are conducive to obtaining accurate and comprehensive analysis results in the equipment development phase.

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.

scholarly journals Predicting the effect of the rib pitch on thermal performance factor of small channels plate heat exchangers fitted with Y and C shapes obstacles

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Sirine Chtourou ◽  
Hassene Djemel ◽  
Mohamed Kaffel ◽  
Mounir Baccar
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Computer Aided Design ◽  
Flow Characteristics ◽  
Plate Heat Exchanger ◽  
Geometrical Parameters ◽  
Computational Domain ◽  
Ansys Fluent ◽  
Plate Heat ◽  
Small Channels

AbstractThis study presents a numerical analysis of a laminar counter flow inside small channels plate heat exchanger fitted with Y and C shape obstacles. Using the Computational Fluid Dynamics CFD, an advanced and modern simulation technique, the influence of the geometrical parameters (such as geometry, rib pitch) on the flow characteristics, the thermal and the hydrodynamics performance of the PHE (plate heat exchanger) is investigated numerically. The main goal of this work is to increase the flow turbulence, enhance the heat transfer and the thermal efficiency by inserting new obstacles forms. The computational domain is a conjugate model which is developed by the Computer Aided Design CAD software Solidworks. The results, obtained with Ansys Fluent, show that the presence of the shaped ribs provides enhancement in heat transfer and fluid turbulence. The CFD analysis is validated with the previous study. The non-dimensional factors such as the Nusselt number Nu, the skin friction factor Cf and the thermo-hydraulic performance parameter THPP are predicted with a Reynolds number Re range of 200–800. The temperature and the velocity distribution are presented and analyzed. The Y ribs and the C ribs offer as maximum THPP values respectively about 1.44 and 2.6 times of a smooth duct.

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