scholarly journals Two-phase flow in channels with non-circular cross-section of pneumatic transport of powder material

2018 ◽  
Vol 22 (Suppl. 5) ◽  
pp. 1407-1424
Author(s):  
Sasa Milanovic ◽  
Milos Jovanovic ◽  
Zivan Spasic ◽  
Boban Nikolic
Keyword(s):  
Cross Section ◽  
Numerical Experiments ◽  
Circular Cross Section ◽  
Pneumatic Transport ◽  
Secondary Flows ◽  
Solid Particles ◽  
Stress Model ◽  
Two Phase ◽  
Initial Flow ◽  
Numerical Grid

The paper presents a numerical simulation of two-phase turbulent flow in straight horizontal channels of pneumatic transport with non-circular cross-section. For the granular flow simulation, we have chosen the flow of solid particles of quartz, flour, and ash in the flow of air, which is transporting fluid. During the modeling of the flow, the transported solid particles are reduced to spherical shapes. A correction of the stress model of turbulence is performed by taking into account the influences of the induction of secondary flows of the second order in the gas phase. The full Reynolds stress model was used for modeling the turbulence, and the complete model is used for the turbulent stresses and turbulent temperature fluxes. All numerical experiments were conducted for the same initial flow conditions and a single uniform grid was adopted for all numerical experiments. The flow is observed in a straight channel of a square cross-section and dimensions of sides of 200 mm and the length of 80 Dh. During the simulation, the fineness of the numerical grid was also tested, and the paper shows results of the numerical grid of the highest resolution beyond which the fineness does not influence the obtained results. The paper offers graphics of velocities of the solid particles transported by the transporting fluid (air) along the channel.

scholarly journals TWO-PHASE TURBULENT FLOW IN STRAIGHT HORIZONTAL CHANNELS WITH A SQUARE CROSS-SECTION TAKING INTO ACCOUNT THE INFLUENCE OF VERTICAL FORCES

2018 ◽  
pp. 019
Author(s):  
Saša Milanović ◽  
Miloš Jovanović ◽  
Živan Spasić ◽  
Boban Nikolić
Keyword(s):  
Turbulent Flow ◽  
Cross Section ◽  
Cross Sections ◽  
Flow Direction ◽  
Reynolds Stress Model ◽  
Secondary Flows ◽  
Solid Particles ◽  
Stress Model ◽  
Two Phase ◽  
Mesh Density

The paper presents a numerical simulation of a two-phase turbulent flow in pneumatic transport through straight horizontal channels with a square cross-section. The transport of solid particles of ash and flour is taken as the two-phase flow, while air is chosen for the transporting fluid. The motion of solid particles occurs due to the aerodynamic forces of the transporting fluid. The paper considers the motion of solid particles by taking into account the influence of vertical forces, which act on the transported solid particles. In flow modelling, the transported solid particles are reduced to spherical shapes. The stress model of turbulence is corrected by taking into account the influence of the induction of secondary flows of the second kind in the gas phase. The full Reynolds stress model is used to model the turbulence, with the application of the complete model for turbulent stresses and turbulent temperature fluxes. The paper presents the results of the numerical grid with the highest resolution above which the increase of the mesh density does not affect the obtained results. The diagrams of the positions of the transported solid particles are provided for cross-sections normal and parallel to the flow direction.

Concentration Profiling Of Two Phase Flow In A Gravity Flow Rig Using Optical Tomography

2012 ◽  
Author(s):  
Sallehuddin Ibrahim ◽  
Mohd Fua’ad Rahmat ◽  
Mustafa Musbah Elmajri ◽  
Mohammad Amri Mohammad Yunus
Keyword(s):  
Cross Section ◽  
Two Phase Flow ◽  
Optical Tomography ◽  
Solid Particles ◽  
Gravity Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Tomography System ◽  
Infra Red ◽  
Tomography Method

Matlamat kertas kerja ini ialah untuk membentangkan penyelidikan tentang penggunaan kaedah tomografi optik menggunakan penderia–penderia infra merah untuk pemantauan masa nyata terhadap zarah–zarah pepejal yang dialirkan oleh rig aliran graviti. Penderia terdiri daripada dua projeksi cahaya orthogonal dan dua projeksi cahaya melintang untuk membentuk deretan atas dan bawah menjadi empat projeksi selari. Penumpuan pancaran daripada satu sumber cahaya dan mengalirkannya melalui rejim aliran yang memastikan keamatan pancaran dikesan pada bahagian yang bertentangan disambungkan kepada agihan dan pekali serapan bagi fasa–fasa yang berbeza dalam laluan pancaran. Maklumat pada aliran yang diperolehi oleh penderia-penderia yang dipasang di bahagian atas dan bawah akan dijadikan dalam bentuk digital oleh sistem perolehan data sebelum ia dihantar ke sebuah computer untuk dianalisis untuk memaparkan keratan silang imej. Penyelidikan ini berjaya dikembangkan dan diuji menggunakan sebuah sistem tomografi infra merah untuk memaparkan kepekatan aliran dwi fasa dalam rig aliran gravity. Kata kunci: Profil kepekatan; aliran dwi fasa; tomografi optic; infra-merah; aliran pepejal The objective of this paper is to present research on the use of an optical tomography method using infra–red sensors for real–time monitoring of solid particles conveyed by a gravity flow rig. The sensor comprised two orthogonal and two diagonal light projections to form upstream and downstream arrays in a total of four parallel projections. Collimating the radiated beam from a light source and passing it through a flow regime ensures that the intensity of radiation detected on the opposite side is linked to the distribution and the absorption coefficients of the different phases in the path of the beam. The information on the flow captured using upstream and downstream infra-red sensors is digitized by the DAS system before it was passed into a computer to be analyzed in order to reconstruct the cross section image. This investigation successfully developed and tested an infra–red tomography system to profile the concentration of two phase flow in a gravity flow rig. Key words: Concentration profiles; two phase flow; optical tomography; infra–red; solid flow

Turbulence Generated Secondary Flows in Ducts of Non-Circular Cross-Section

1982 ◽  
Vol 24 (3) ◽  
pp. 119-127
Author(s):  
W. J. Seale
Keyword(s):  
Cross Section ◽  
Circular Cross Section ◽  
Secondary Flows ◽  
Algebraic Expression ◽  
Rod Bundle ◽  
Stress Models

The use of algebraic stress models in the prediction of secondary flows in straight ducts of non-circular cross-section is found to be unsatisfactory and to give inconsistent results in the sub-channels within a rod bundle. An algebraic expression is presented which allows the source of axial vorticity to be calculated directly and without iteration. The expression is shown to reproduce secondary velocities in square and triangular ducts, and in a duct consisting of two inter-connected subchannels.

Two-Phase Flow (Oil and Water) in Ducts with the Elliptical Cross-Section: Modeling and Simulation

2019 ◽  
Vol 24 ◽  
pp. 61-75
Author(s):  
J.L. de Oliveira ◽  
A.G. Barbosa de Lima ◽  
R. Pereira Ramos ◽  
H. Luma Fernandes Magalhães ◽  
W.R. Gomes dos Santos ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Aspect Ratio ◽  
Cross Section ◽  
Operating Cost ◽  
Circular Cross Section ◽  
Elliptical Cross Section ◽  
Two Phase ◽  
Elliptical Cross ◽  
Ansys Cfx ◽  
Velocity Pressure

In the oil industry, pipelines (circular ducts) are widely used for the transportation of oil and yours derived. Because of their advantages, such as low operating cost and increased safety during transportation, pipelines have become indispensable for transporting oil in large quantities and for long distances. As an alternative to this problem, the transport of oil and water can be accomplished using ducts with an elliptical cross-section. Thus, this work has the objective of studying the flow of oil and water in cylindrical ducts with an elliptical cross-section by using the Ansys CFX software. Results of the velocity, pressure and volumetric fraction distributions of the oil and water phases are presented and analyzed. By applying the same inlet velocity to oil and water, revealed that the elliptical duct, with aspect ratio equal to 5.0, has a pressure drop less (84.2%) than the pressure drop obtained for one duct of circular cross-section (aspect ratio equal to 1.0).

Investigation of Particle-Laden Flow in a Straight Duct Using Large Eddy Simulation

2007 ◽  
Author(s):  
M. Fairweather ◽  
J. Yao
Keyword(s):  
Large Eddy Simulation ◽  
Fluid Phase ◽  
Particle Dispersion ◽  
Secondary Flows ◽  
Solid Particles ◽  
Duct Flow ◽  
Mean Flow ◽  
Two Phase ◽  
Eddy Simulation ◽  
Large Eddy

A particle-laden turbulent flow in a square duct is predicted using large eddy simulation (LES). The simulation is performed for a Reynolds number of 35,500, and correctly predicts the existence of secondary flows and their effects on the mean flow. The results are also in good qualitative agreement with experimental data obtained at different Reynolds numbers. One-way coupling is assumed between solid particles and the fluid, and a particle equation of motion, including Stokes drag, lift, buoyancy and gravity force terms, solved using a Lagrangian particle tracking technique. Three sizes of particle (1, 50 and 100 μm) are considered, and results demonstrate that size has a significant effect on particle dispersion and deposition in the duct flow. As particle size increases, therefore, they tend to settle on the floor of the duct, with less dispersion in the fluid phase. The study demonstrates the usefulness of LES for nuclear waste processing applications since secondary flows occur in many practically-relevant flows, and since it is desirable that the two-phase waste mixture is kept as homogeneous as possible to prevent, or at least discourage, the settling out of solid particles to form a bed which can promote pipe blockages.

Discrete and asymptotic approximations for one stationary radiative–conductive heat transfer problem

2020 ◽  
Vol 35 (3) ◽  
pp. 127-141
Author(s):  
Andrey A. Amosov ◽  
Nikita E. Krymov
Keyword(s):  
Heat Transfer ◽  
Boundary Value Problem ◽  
Cross Section ◽  
Numerical Experiments ◽  
Transfer Problem ◽  
Circular Cross Section ◽  
Conductive Heat Transfer ◽  
Asymptotic Approximations ◽  
Heat Conducting ◽  
Conductive Heat

AbstractSpecial discrete and asymptotic approximations are proposed for the boundary value problem describing a stationary radiative–conductive heat transfer in a system of absolutely black heat-conducting rods of circular cross-section. Results of numerical experiments are presented to confirm the efficiency of proposed approximations.

Numerical investigation of the effect of water/Al2O3 nanofluid on heat transfer in trapezoidal, sinusoidal and stepped microchannels

2019 ◽  
Vol 30 (5) ◽  
pp. 2439-2465 ◽  
Author(s):  
Vahid Jaferian ◽  
Davood Toghraie ◽  
Farzad Pourfattah ◽  
Omid Ali Akbari ◽  
Pouyan Talebizadehsardari
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Cross Section ◽  
Cross Sections ◽  
Volume Fraction ◽  
Pure Water ◽  
Circular Cross Section ◽  
Reynolds Numbers ◽  
Two Phase ◽  
Content Type

Purpose The purpose of this study is three-dimensional flow and heat transfer investigation of water/Al2O3 nanofluid inside a microchannel with different cross-sections in two-phase mode. Design/methodology/approach The effect of microchannel walls geometry (trapezoidal, sinusoidal and stepped microchannels) on flow characteristics and also changing circular cross section to trapezoidal cross section in laminar flow at Reynolds numbers of 50, 100, 300 and 600 were investigated. In this study, two-phase water/Al2O3 nanofluid is simulated by the mixture model, and the effect of volume fraction of nanoparticles on performance evaluation criterion (PEC) is studied. The accuracy of obtained results was compared with the experimental and numerical results of other similar papers. Findings Results show that in flow at lower Reynolds numbers, sinusoidal walls create a pressure drop in pure water flow which improves heat transfer to obtain PEC < 1. However, in sinusoidal and stepped microchannel with higher Reynolds numbers, PEC > 1. Results showed that the stepped microchannel had higher pressure drop, better thermal performance and higher PEC than other microchannels. Originality/value Review of previous studies showed that existing papers have not compared and investigated nanofluid in a two-phase mode in inhomogeneous circular, stepped and sinusoidal cross and trapezoidal cross-sections by considering the effect of changing channel shape, which is the aim of the present paper.

Sign in / Sign up

Export Citation Format

Share Document