scholarly journals Effect of a Symmetric Contraction on the Concentration Profiles of a Particle-Laden Slurry

2011 ◽  
Author(s):  
A. Deshpande ◽  
K. Ramisetty ◽  
F. W. Chambers ◽  
M. E. McNally ◽  
R. M. Hoffman
Keyword(s):  
Single Phase ◽  
Solid Phase ◽  
Fluid Dynamic ◽  
Density Ratio ◽  
Primary Phase ◽  
Solid Particles ◽  
Concentration Profiles ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Slurry Concentration

In-line measurements and sample stream withdrawals for on-line and/or at-line measurements of slurries flowing in horizontal pipes can be complicated by nonuniform slurry profiles. More uniform profiles would improve measurements. Area contractions are a common means used to produce more uniform velocity fields for single phase flows. For example, contractions are used to condition the flow entering wind tunnel test sections and make velocity profiles more uniform at venturi throats. It was desired to determine whether area contractions could be used to make slurry concentration profiles more uniform in horizontal pipe flows. An ASME flow nozzle with a contraction diameter ratio of 0.5 was chosen as a well defined geometry to consider in a Computational Fluid Dynamic (CFD) study of the effects of a contraction on slurry concentration profiles. The pipe was 2.8 m long with a 50.8 mm diameter. The entrance of the contraction was placed at 35 pipe diameters from the inlet in fully developed flow. A length of 20 diameters followed the contraction. The slurry had a xylene liquid phase and an ADP solid phase with a density ratio of 1.7. The simulations were performed at primary phase velocities of 2 m/s and 4 m/s, corresponding to Reynolds numbers of 1.4E05 and 2.8E05. Spherical particle diameters of 38, 75, and 150 μm were used at concentrations of 0.05, 0.2, and 0.3. ANSYS FLUENT 12 software was used with the standard k-ε turbulence model and standard wall function. The mixture multi-phase model was used for the two-phase flow. An unstructured tetrahedral meshing scheme was used with 1.4 million elements. The grid was adjusted until the condition 30 < y+ <60 for the mesh point nearest the wall was satisfied. A grid refinement study was performed to insure grid independence. The computational scheme first was validated by comparing pipe flow velocity and concentration profiles to results in the literature. The computations performed with the contraction showed that in all cases the concentration profiles of the solid particles displayed greater uniformity than the profiles in the pipe upstream of the contraction. The effect of the contraction was more pronounced for the larger particles. As in the case of single phase flows, the contraction caused the axial turbulence intensity to decrease. The greater uniformity of the concentration profiles at the exit plane of the nozzle, suggest that the contraction can provide better conditions for performing measurements of a particle-laden slurry.

Computational Study of Slurry Flow in Pipes to Determine Profiles Sensed in Near Infrared Slurry Measurements

2011 ◽  
Author(s):  
V. Pasangulapati ◽  
N. R. Kesana ◽  
G. Sharma ◽  
F. W. Chambers ◽  
M. E. McNally ◽  
...  
Keyword(s):  
Near Infrared ◽  
Volume Fraction ◽  
Solid Phase ◽  
Computational Study ◽  
Solid Volume Fraction ◽  
Density Ratio ◽  
Optical Measurements ◽  
Concentration Profiles ◽  
Horizontal Pipe ◽  
Volume Fractions

It is desired to perform accurate Near Infrared sensor measurements of slurries flowing in pipes leaving large batch reactors. A concern with these measurements is the degree to which the slurry sensed is representative of the material in the reactor and flowing through the pipe. Computational Fluid Dynamics (CFD) has been applied to the flow in the pipe to determine the flow fields and the concentration profiles seen by the sensors. The slurry was comprised of a xylene liquid phase and an ADP (2-amino-4, 6-dimethylpyrimidine) solid phase with a density ratio of 1.7. Computations were performed for a horizontal pipe with diameter 50.8 mm, length 2.032 m, and 1.76 m/s and 3.26 m/s mixture velocities. The corresponding pipe Reynolds numbers were 1.19E+05 and 2.21E+05. The flow through a slotted cylindrical probe inserted radially in the pipe also was considered. Spherical slurry particles with diameters from 10 μm to 1000 μm were considered with solid volume fractions of 12%, 24%, and 35%. Computations were performed with ANSYS FLUENT 12 software using the Realizable k-ε turbulence model and the enhanced wall treatment function. Comparisons of computed vertical profiles of solid volume fraction to results in the literature showed good agreement. Symmetric, nearly flat solid volume fraction profiles were observed for 38 μm particles for all three initial solid volume fractions. Asymmetric solid volume fraction profiles with greater values toward the bottom were observed for the larger particles. Changes in the profiles of turbulent kinetic energy also were observed. These changes are important for optical measurements which depend upon the mean concentration profiles as well as the turbulent motion of the slurry particles.

Experimental Characterization of Particle-Laden Air Flow Across Horizontal Pipe Junctions

2018 ◽  
Author(s):  
Tariq S. Khan ◽  
Mohamed Alshehhi ◽  
Xu Rumin ◽  
Saqib Salam
Keyword(s):  
Mass Fraction ◽  
Solid Phase ◽  
Flow Behavior ◽  
Air Flow ◽  
Industrial Applications ◽  
Solid Particles ◽  
Gas Flows ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Particle Sizer

There are several industrial applications in which two phase solid-gas flows are involved. At times, pipe junctions are involved where flow split takes place. Present study consists of experimental investigation of turbulent gas-solid two-phase flow through horizontal pipe junctions. The effects of air flow rate, branch diameter and pipe orientation at junctions are investigated on mass fraction, phase split and solid particles distribution across the junctions. Silica powder, in the monodispersed size of 15 μm was injected into the pipelines by a micro-feeder. The powder was entrained in an air flow which passed horizontally through a long straight channel of circular pipe with T and Y junctions. The main pipe was 51mm in diameter while the inlet superficial velocity of gas was varied from 5 m/s to 13.5m/s. The particles mass concentration was measured by the aerodynamic particle sizer (APS). Experimental results showed that solid phase split followed air flow split while decreasing the inlet air velocity caused major decrease in the mass fraction at junction pipe. The orientation of junction pipe has a significant effect on the flow behavior along the pipe. These results indicate that the behavior of solid particles is a complex phenomenon in pipe flows.

scholarly journals Computational investigation of liquid-solid slurry flow through an expansion in a rectangular duct

2014 ◽  
Vol 62 (3) ◽  
pp. 234-240 ◽  
Author(s):  
Gianandrea Vittorio Messa ◽  
Stefano Malavasi
Keyword(s):  
Volume Fraction ◽  
Particle Density ◽  
Fluid Model ◽  
Solid Volume Fraction ◽  
Solid Particles ◽  
Rectangular Duct ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Two Fluid Model ◽  
Two Fluid

Abstract The flow of a mixture of liquid and solid particles at medium and high volume fraction through an expansion in a rectangular duct is considered. In order to improve the modelling of the phenomenon with respect to a previous investigation (Messa and Malavasi, 2013), use is made of a two-fluid model specifically derived for dense flows that we developed and implemented in the PHOENICS code via user-defined subroutines. Due to the lack of experimental data, the two-fluid model was validated in the horizontal pipe case, reporting good agreement with measurements from different authors for fully-suspended flows. A 3D system is simulated in order to account for the effect of side walls. A wider range of the parameters characterizing the mixture (particle size, particle density, and delivered solid volume fraction) is considered. A parametric analysis is performed to investigate the role played by the key physical mechanisms on the development of the two-phase flow for different compositions of the mixture. The main focuses are the distribution of the particles in the system and the pressure recovery

scholarly journals Influence of Blade Type on the Flow Structure of a Vortex Pump for Solid-Liquid Two-Phase Flow

Machines ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 353
Author(s):  
Hui Quan ◽  
Yanan Li ◽  
Lei Kang ◽  
Xinyang Yu ◽  
Kai Song ◽  
...  
Keyword(s):  
Flow Structure ◽  
Liquid Flow ◽  
Single Phase ◽  
Solid Phase ◽  
Internal Flow ◽  
Phase Flow ◽  
Centrifugal Pumps ◽  
Two Phase ◽  
Vortex Pump ◽  
Solid Liquid

Vortex pumps have good non-clogging performance owing to their impellers being retracted into retraction cavities, but they are much less efficient than ordinary centrifugal pumps. In this paper, numerical simulations were performed on a model of the 150WX200-20 vortex pump for four different blade types, and the influence of blade structure on pump performance was determined. The simulations revealed the existence of axial vortices in the flow passage between the blades in the impeller region. The geometric characteristics of these axial vortices were more regular in two-phase solid-liquid flow than single-phase liquid flow. The presence of the solid phase reduced the vortex strength compared with the single-phase flow and suppressed the increase in size of the secondary circulation vortex. It was found, however, that the blade shape had a greater influence on the circulating flow than the presence of the solid phase. The flow state of the medium flowing out of the impeller domain had a direct effect on the circulating flow with this effect being related to the law governing the flow of the medium in the flow channel between the blades. It was found that the performance of a front-bent blade was the best and that of a curved blade the worst. This influence of blade type on the internal flow structure was used to further explain the relationship between the internal flow structure and the external characteristics of the vortex pump, the understanding of which is crucial for blade selection and hydraulic optimization.

Distribution of solid particles in a mixed vessel

1990 ◽  
Vol 55 (9) ◽  
pp. 2169-2181 ◽  
Author(s):  
Petr Bílek ◽  
František Rieger
Keyword(s):  
Solid Phase ◽  
Solid Particles ◽  
Concentration Measurement ◽  
Concentration Profiles ◽  
Conductivity Method ◽  
Phase Concentration ◽  
Solid Phase Concentration ◽  
Vessel Bottom ◽  
Vessel Axis

The aim of our research was to study the axial, radial and tangential solid phase concentration profiles in a mixed vessel. The conductivity method was used for the concentration measurement. We accomplished the measurement in eleven points in five heights above the vessel bottom. The points were situated on three vertical planes passing through the vessel axis and on five values of radii. It was determined by means of statistic test of variance if it was possible to measure the concentration only in one point in each distance from the vessel bottom and neglect the radial and tangential concentration differences.

scholarly journals Numerical Simulation of Macrosegregation with Solid Deformation During the Solidification of Steel Ingots Using a Single-Phase/Two-Phase Integrated Model

Metals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 669
Author(s):  
Kangxin Chen ◽  
Houfa Shen
Keyword(s):  
Liquid Flow ◽  
Single Phase ◽  
Solid Phase ◽  
Steel Ingot ◽  
Integrated Model ◽  
Phase Model ◽  
Two Phase ◽  
Deformation Stage ◽  
Solid Deformation ◽  
Steel Ingots

Macrosegregation, a serious defect formed during the solidification of steel ingots, impairs the performance of the final components. To predict macrosegregation caused by thermal-solutal convection and solid deformation, a volume-averaged single-phase/two-phase integrated model is developed. During the deformation stage, the two-phase model coupling the solid deformation and liquid flow in the mushy zone is utilized. Before or after the deformation stage, the motion of the solid phase is neglected, and the single-phase model is solved. A 450 kg steel ingot punching test is considered for application. The results show that when the solid shell of the ingot is being punched, the solid phase in the mushy core at punching height is compressed, and a relative liquid flow is induced. This in turn causes a transition of positive segregation to negative segregation in the compressed mushy core of the ingot. According to numerical sensitivity tests of different punching parameters, as the punching start time and punching velocity increase, the effect of punching on macrosegregation will be smaller. It is demonstrated that the single-phase/two-phase integrated model can predict macrosegregation in the steel ingots which are deformed during solidification.

Three-Dimensional Numerical Simulation of Convective Melting of Solid Particles in a Fluid

1999 ◽  
Author(s):  
Y. L. Hao ◽  
Y.-X. Tao
Keyword(s):  
Volume Fraction ◽  
Solid Phase ◽  
Rectangular Cross Section ◽  
Three Dimensional ◽  
Phase Changes ◽  
Solid Particles ◽  
Preliminary Calculation ◽  
Two Phase ◽  
Closed Set ◽  
Gravity Effects

Abstract A physical model of two-phase flow and heat-mass transfer with the phase changes based on the theory of interacting continua is proposed. All terms in the conservation equations are analyzed and the constitutive equations are presented. A closed set of governing equations describing the convective melting of solid particles in a fluid is obtained. The numerical method is developed for the solution of velocity, temperature, and volume fraction of solid phase for the three-dimensional melting in a rectangular cross-section channel. Preliminary calculation, including gravity effects, shows that the result is reasonable. This study provides a basis for the theoretical and experimental investigation of convective melting of solid particles in a fluid.

scholarly journals Prospects for the application of radiometric methods in the measurement of two-phase flows

2018 ◽  
Vol 180 ◽  
pp. 01001
Author(s):  
Marcin Zych
Keyword(s):  
Environmental Protection ◽  
Solid Phase ◽  
Life Sciences ◽  
Solid Particles ◽  
Gas Mixture ◽  
Gas Flows ◽  
Mathematical Methods ◽  
Two Phase Flows ◽  
Two Phase ◽  
Phase Mixture

The article constitutes an overview of the application of radiometric methods in the research of two-phase flows: liquid-solid particles and liquid-gas flows. The methods which were used were described on the basis of the experiments which were conducted in the Water Laboratory of the Wrocław University of Environmental and Life Sciences and in the Sedimentological Laboratory of the Faculty of Geology, Geophysics and Environmental Protection, AGH-UST in Kraków. The advanced mathematical methods for the analysis of signals from scintillation probes that were applied enable the acquisition of a number of parameters associated with the flowing two-phase mixture, such as: average velocities of the particular phases, concentration of the solid phase, and void fraction for a liquid-gas mixture. Despite the fact that the application of radioactive sources requires considerable carefulness and a number of state permits, in many cases these sources become useful in the experiments which are presented.

Pneumatic transport

1969 ◽  
Vol 39 (2) ◽  
pp. 407-432 ◽  
Author(s):  
P. R. Owen
Keyword(s):  
Fine Particles ◽  
Solid Wall ◽  
Electrostatic Charge ◽  
Difficult Problem ◽  
Solid Particles ◽  
Gas Velocity ◽  
Physical Explanation ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Different Types

Certain aspects of the transport of solid particles by a turbulent airstream are discussed, namely: the conveyance of particles in a horizontal pipe, including those carrying an appreciable electrostatic charge; the mechanism of deposition onto a solid wall; and the behaviour of fine particles in a shear flow, such as that in a round jet.Rough estimates of the effect of the particles on the gaseous turbulence are made, and a primitive physical explanation is offered of the observed velocitylag and pressure drop associated with the transport of particles in a horizontal pipe, under conditions where the influence of the particles’ weight is significant.Attention is drawn to the difficult problem of dynamically scaling a two-phase flow, and to the different types of interaction between the phases which can occur in a pipe according to its size, the gas velocity through it, and the physical characteristics of the particles.The paper is an annotated version of a survey presented to the I.U.T.A.M. Symposium on ‘Flow of fluid-solid mixtures’ held in Cambridge during March 1969.

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