scholarly journals Flow behaviour and local concentration of coarse particles-water mixture in inclined pipes

2017 ◽  
Vol 65 (2) ◽  
pp. 183-191 ◽  
Author(s):  
Pavel Vlasak ◽  
Zdenek Chara ◽  
Jiri Konfrst
Keyword(s):  
Particle Size ◽  
Gamma Ray ◽  
Dominant Mode ◽  
Solid Particles ◽  
Flow Behaviour ◽  
Coarse Particle ◽  
Narrow Particle Size Distribution ◽  
Local Concentration ◽  
Water Mixture ◽  
Mixture Flow

AbstractNarrow particle size distribution basalt pebbles of mean particle size 11.5 mm conveyed by water in the pipe sections of different inclination were investigated on an experimental pipe loop, consisting of smooth stainless steel pipes of inner diameterD= 100 mm. Mixture flow-behaviour and particles motion along the pipe invert were studied in a pipe viewing section, the concentration distribution in pipe cross-section was studied with the application of a gamma-ray densitometer. The study refers to the effect of mixture velocity, overall concentration, and angle of pipe inclination on chord-averaged concentration profiles and local concentration maps, and flow behaviour of the coarse particle-water mixtures. The study revealed that the coarse particle-water mixtures in the inclined pipe sections were significantly stratified, the solid particles moved principally close to the pipe invert, and for higher and moderate flow velocities particle saltation becomes the dominant mode of particle conveying.

scholarly journals Experimental investigation of coarse particles-water mixture flow in horizontal and inclined pipes

2014 ◽  
Vol 62 (3) ◽  
pp. 241-247 ◽  
Author(s):  
Pavel Vlasák ◽  
Zdeněk Chára ◽  
Jan Krupička ◽  
Jiří Konfršt
Keyword(s):  
Dominant Mode ◽  
Solid Particles ◽  
Coarse Grained ◽  
Water Mixture ◽  
Mixture Flow ◽  
Horizontal Pipe ◽  
Pressure Drops ◽  
Steel Pipes ◽  
Inner Diameter ◽  
Inclined Pipes

Abstract The effect of solid concentration and mixture velocity on the flow behaviour, pressure drops, and concentration distribution of coarse particle-water mixtures in horizontal, vertical, and inclined smooth stainless steel pipes of inner diameter D = 100 mm was experimentally investigated. Graded basalt pebbles were used as solid particles. The study revealed that the coarse-grained particle-water mixtures in the horizontal and inclined pipes were significantly stratified. The solid particles moved principally in a layer close to the pipe invert; however for higher and moderate flow velocities, particle saltation became the dominant mode of particle conveyance. Frictional pressure drops in the horizontal pipe were found to be markedly higher than in the vertical pipe, while the frictional pressure drops in the ascending pipe increased with inclination angle up to about 30°.

EFFECT OF PIPE INCLINATION ON COARSE-GRAINED PARTICLE-WATER MIXTURES FLOW

2020 ◽  
Vol 23 (2) ◽  
Author(s):  
Pavel Vlasak ◽  
◽  
Zdenek Chara ◽  
Jiri Konfrst ◽  
Jan Krupicka ◽  
...  
Keyword(s):  
Concentration Distribution ◽  
Gamma Ray ◽  
Solid Phase ◽  
Dominant Mode ◽  
Coarse Grained ◽  
Local Concentration ◽  
Water Mixture ◽  
Pressure Drops ◽  
Inclined Pipes ◽  
Pipe Inclination

The effect of the mixture velocity, solid concentration, and pipe inclination on the coarse-grained particle–water mixtures flow behaviour, concentration distribution, and pressure drops were experimentally studied in horizontal, vertical, and inclined pipes of inner diameter D=100 mm. Graded basalt gravel was used as a solid phase. The local concentration distribution was studied with the application of a gamma-ray densitometer. The study revealed the stratified flow pattern of the coarse particle-water mixture in horizontal and inclined pipes. The particles moved principally close to the pipe invert, and particle saltation becomes the dominant mode of particle conveying for higher and moderate flow velocities. The frictional pressure droops in ascending pipe increases with increasing pipe inclination up to about 30 degrees, then gradually decreases. For the pipe inclination lower than about 30°, the effect of pipe inclination on local concentration distribution was not significant. The in-situ concentration reached higher values in the ascending than in the descending sections.

scholarly journals Experimental investigation of fine-grained settling slurry flow behaviour in inclined pipe sections

2019 ◽  
Vol 67 (2) ◽  
pp. 113-120
Author(s):  
Pavel Vlasák ◽  
Zdeněk Chára ◽  
Václav Matoušek ◽  
Jiří Konfršt ◽  
Mikoláš Kesely
Keyword(s):  
Concentration Distribution ◽  
Flow Behaviour ◽  
Narrow Particle Size Distribution ◽  
Local Concentration ◽  
Slurry Flow ◽  
Pressure Drops ◽  
Fine Grained ◽  
Limit Velocity ◽  
The Difference ◽  
Inclined Pipe

Abstract For the safe and economical design and operation of freight pipelines it is necessary to know slurry flow behaviour in inclined pipe sections, which often form significant part of pipelines transporting solids. Fine-grained settling slurry was investigated on an experimental pipe loop of inner diameter D = 100 mm with the horizontal and inclined pipe sections for pipe slopes ranging from −45° to +45°. The slurry consisted of water and glass beads with a narrow particle size distribution and mean diameter d50 = 180 µm. The effect of pipe inclination, mean transport volumetric concentration, and slurry velocity on flow behaviour, pressure drops, deposition limit velocity, and concentration distribution was studied. The study revealed a stratified flow pattern of the studied slurry in inclined pipe sections. Frictional pressure drops in the ascending pipe were higher than that in the descending pipe, the difference decreased with increasing velocity and inclination. For inclination less than about 25° the effect of pipe inclinations on deposition limit velocity and local concentration distribution was not significant. For descending pipe section with inclinations over −25° no bed deposit was observed.

The Influence of Particle Size on Viscosity in Thixo Material

2012 ◽  
Vol 504-506 ◽  
pp. 333-338 ◽  
Author(s):  
Siri Harboe ◽  
Michael Modigell
Keyword(s):  
Particle Size ◽  
Solid Fraction ◽  
Silicone Oil ◽  
Solid Particles ◽  
Flow Behaviour ◽  
Liquid Viscosity ◽  
Complex Flow ◽  
Unknown Parameters ◽  
Shear Dependent Viscosity ◽  
Process Route

In thixo casting and forming processes, the forming alloy is in a semi solid state - a suspension of solid particles in a liquid matrix. As known from suspension rheology, the solid fraction, particle size distribution, particle shape, surface properties, state of agglomeration etc. determine the complex flow behaviour of the material. In thixo forming, the flow behaviour determines the quality of the produced parts, and it is essential to quantify the flow behaviour to optimize the process route. The goal of the present work was to evaluate the effect of particle size and state of agglomeration on the flow properties in a thixo material-analogue suspension, and to establish an easily applicable model to describe the non-Newtonian behaviour of a thixo material. For this purpose, experiments were conducted applying synthetic suspensions (built up of mono-disperse glass spheres in silicone oil) with behaviour analogue to thixo material. The advantage of synthetic suspensions is that parameters such as particle size and shape can be controlled in a simple manner and hence the number of unknown parameters is decreased. The experimental results show influence of shear rate, solid fraction, particle size and liquid viscosity. A model to determine the shear dependent viscosity was set up. This model was based on the Krieger-Dougherty equation for the relation between viscosity and solid fraction, and on the generally accepted theory that the state of agglomerations is influenced by shear. The model could successfully display the degree of shear thinning and takes into account the influence of particle size. However, it was found that the relation of the viscosity of the suspension and the liquid viscosity was non-linear. This does not correspond to the Krieger-Dougherty equation.

Energy Loss in Snow-Water Mixture Flow

2003 ◽  
Author(s):  
Mikio Sasaki ◽  
Takahiro Takeuchi ◽  
Hiroshi Takahashi
Keyword(s):  
Specific Gravity ◽  
Energy Loss ◽  
Friction Factor ◽  
Pure Water ◽  
Solid Particles ◽  
Water Mixture ◽  
Solid Concentration ◽  
Mixture Flow ◽  
Snow Water ◽  
Relative Friction

Energy losses in the solid-water mixture flow where the density of solid is nearly equal to that of fluid were observed in horizontal pipelines. The observation was carried out to investigate the influence that the specific gravity of the solid particles exerted on the energy loss. A relative friction factor based on the friction factor of the pure water flow becomes larger as the solid concentration increases in the mixture flow of solid particles with the specific gravity 0.86 and 1.04. The relative friction factor is given with the Froude number, the solid concentration and the specific gravity of solid.

scholarly journals Effect of pipe inclination on flow behaviour of fine-grained settling slurry

2019 ◽  
Vol 213 ◽  
pp. 02094
Author(s):  
Pavel Vlasak ◽  
Zdenek Chara ◽  
Vaclav Matousek ◽  
Jiri Konfrst ◽  
Mikolas Kesely
Keyword(s):  
Concentration Distribution ◽  
Gamma Ray ◽  
Deposition Velocity ◽  
Narrow Particle Size Distribution ◽  
Local Concentration ◽  
Horizontal Pipe ◽  
Pressure Drops ◽  
Fine Grained ◽  
Inclined Pipe ◽  
Pipe Inclination

The effect of flow parameters of fine-grained settling slurry on the pressure drop-velocity relationship, deposition limit velocity and local concentration distribution was studied in an experimental pipe loop of inner diameter D = 100 mm with inclinable pipe sections for pipe inclination ranging from – 45° to +45°. The slurry consisted from water and narrow particle size distribution glass beads of mean diameter d50 = 0.18 mm. The concentration distribution was studied with application of a gamma-ray densitometry. The deposition velocity was defined as the flow velocity at which stationary deposit started to be formed at the pipe invert. The study revealed the stratified flow pattern of the studied slurry in inclined pipe sections, for slurry velocities below to the deposition limit sliding or stationary bed were created in ascending pipe sections. For low pipe inclination (α < ± 25°) the effect of inclination on local concentration distribution was not significant. Mean transport concentration for descending flow was lower than that for the ascending flow Deposition limit in inclined pipe was slightly lower than that in horizontal pipe. Frictional pressure drops in ascending pipe were higher than that in descending pipe, the difference decreased with increasing velocity and inclination.

Investigation of the different particle size dust releases from rigid filter candles during pulse-jet cleaning

2021 ◽  
pp. 095440622110179
Author(s):  
Xin Luan ◽  
Zhongli Ji ◽  
Longfei Liu ◽  
Ruifeng Wang
Keyword(s):  
Particle Size ◽  
Critical Role ◽  
Operating Conditions ◽  
Solid Particles ◽  
Dust Particles ◽  
Cleaning Efficiency ◽  
Term Operation ◽  
Cleaning Performance ◽  
Experimental Apparatus ◽  
Pulse Jet

Rigid filters made of ceramic or metal are widely used to remove solid particles from hot gases at temperature above 260 °C in the petrochemical and coal industries. Pulse-jet cleaning of fine dust from rigid filter candles plays a critical role in the long-term operation of these filters. In this study, an experimental apparatus was fabricated to investigate the behavior of a 2050 mm filter candle, which included monitoring the variation of pressure dynamic characteristics over time and observing the release of dust layers that allowed an analysis of the cleaning performance of ISO 12103-1 test dusts with different particle size distributions. These results showed the release behavior of these dusts could be divided into five stages: radial expansion, axial crack, flaky release, irregular disruption and secondary deposition. The cleaning performance of smaller sized dust particles was less efficient as compared with larger sized dust particles under the same operating conditions primarily because large, flaky-shaped dust aggregates formed during the first three stages were easily broken into smaller, dispersed fragments during irregular disruption that forced more particles back to the filter surface during secondary deposition. Also, a “low-pressure and long-pulse width” cleaning method improved the cleaning efficiency of the A1 ultrafine test dust from 81.4% to 95.9%.

Penetration Dynamics of Solid Particles into Liquids High-Speed Experimental Results and Modelling

2005 ◽  
Vol 473-474 ◽  
pp. 429-434 ◽  
Author(s):  
Olga Verezub ◽  
György Kaptay ◽  
Tomiharu Matsushita ◽  
Kusuhiro Mukai
Keyword(s):  
Contact Angle ◽  
Particle Size ◽  
Aqueous Solutions ◽  
Particle Velocity ◽  
Weber Number ◽  
High Speed ◽  
Solid Particles ◽  
Bulk Liquid ◽  
Distilled Water ◽  
Critical Weber Number

Penetration of model solid particles (polymer, teflon, nylon, alumina) into transparent model liquids (distilled water and aqueous solutions of KI) were recorded by a high speed (500 frames per second) camera, while the particles were dropped from different heights vertically on the still surface of the liquids. In all cases a cavity has been found to form behind the solid particle, penetrating into the liquid. For each particle/liquid combination the critical dropping height has been measured, above which the particle was able to penetrate into the bulk liquid. Based on this, the critical impact particle velocity, and also the critical Weber number of penetration have been established. The critical Weber number of penetration was modelled as a function of the contact angle, particle size and the ratio of the density of solid particles to the density of the liquid.

Optimum air-demand ratio for maximum aeration efficiency in high-head gated circular conduits

2014 ◽  
Vol 70 (5) ◽  
pp. 871-877 ◽  
Author(s):  
Fahri Ozkan ◽  
M. Cihat Tuna ◽  
Ahmet Baylar ◽  
Mualla Ozturk
Keyword(s):  
Froude Number ◽  
High Speed ◽  
Water Mixture ◽  
High Speed Flow ◽  
Mixture Flow ◽  
Speed Flow ◽  
Aeration Efficiency ◽  
High Head ◽  
Closed Conduit ◽  
Air Vent

Oxygen is an important component of water quality and its ability to sustain life. Water aeration is the process of introducing air into a body of water to increase its oxygen saturation. Water aeration can be accomplished in a variety of ways, for instance, closed-conduit aeration. High-speed flow in a closed conduit involves air-water mixture flow. The air flow results from the subatmospheric pressure downstream of the gate. The air entrained by the high-speed flow is supplied by the air vent. The air entrained into the flow in the form of a large number of bubbles accelerates oxygen transfer and hence also increases aeration efficiency. In the present work, the optimum air-demand ratio for maximum aeration efficiency in high-head gated circular conduits was studied experimentally. Results showed that aeration efficiency increased with the air-demand ratio to a certain point and then aeration efficiency did not change with a further increase of the air-demand ratio. Thus, there was an optimum value for the air-demand ratio, depending on the Froude number, which provides maximum aeration efficiency. Furthermore, a design formula for aeration efficiency was presented relating aeration efficiency to the air-demand ratio and Froude number.

Electroacoustic Study of n-Hexadecane/Water Emulsions

2001 ◽  
Vol 54 (8) ◽  
pp. 503 ◽  
Author(s):  
Linggen Kong ◽  
James K. Beattie ◽  
Robert J. Hunter
Keyword(s):  
Particle Size ◽  
Zeta Potential ◽  
Volume Fraction ◽  
Sodium Dodecyl ◽  
Surfactant Solution ◽  
Minimum Size ◽  
Water Mixture ◽  
Concentrated Suspensions ◽  
Minimum Concentration ◽  
Median Diameter

n-Hexadecane-in-water emulsions were investigated by electroacoustics using a prototype of an AcoustoSizer-II apparatus. The emulsions were formed by passing the stirred oil/water mixture through a homogenizer in the presence of sodium dodecyl sulfate (SDS) at natural pH (6–7). With increasing oil-volume fraction, the particle size increased linearly after 5 and also after 20 passages through the homogenizer, suggesting that surface energy was determining particle size. For systems in which the surfactant concentration was limited, the particle size after 20 passages approached the value dictated by the SDS concentration. With ample surfactant present, the median diameter was a linear function of the inverse of the total energy input as measured by the number of passes. There was, however, a limit to the amount of size reduction that could be achieved in the homogenizer, and the minimum size was smaller at smaller volume fractions. Dilution of the emulsion with a surfactant solution of the same composition as the water phase had a negligible effect on the particle size and changed the zeta potential only slightly. This confirms results from previous work and validates the equations used to determine the particle size and zeta potential in concentrated suspensions. The minimum concentration of SDS that could prevent the emulsion from coalescing for the system with 6% by volume oil was 3 mM. For this dilute emulsion, the particle size decreased regularly with an increase in SDS concentration, but the magnitude of the zeta potential went through a strong maximum at intermediate surfactant concentrations.

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