Download or read book Numerical Study of Optical Concentration Measurements for a Turbulent Slurry Pipe Flow written by Netaji Ravikiran Kesana and published by . This book was released on 2009 with total page 159 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Numerical Modelling of Medium Slurry Flow in a Vertical Pipeline written by Artur Bartosik and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The study deals with the modelling and experiments of vertical solid-liquid turbulent flow with narrowly sized solid particles of average diameters equal to 0.125¬†mm, 0.240¬†mm and 0.470 mm, and solid concentrations by volume from 10% to 40%, called medium slurry. The physical model assumes that the slurry with solid particles surrounded by water is flowing upward through a vertical pipeline with solid concentrations from 10,Äì40% by volume. Experiments with such slurries clearly indicated enhanced damping of the turbulence, which depends on the diameter of the solid particles. The mathematical model constitutes conservative equations based on time averages for mass and momentum. The closure problem was solved by taking into account the Boussinesque hypothesis and a two-equation turbulence model together with an especially designed wall damping function. The wall damping function depends on the average diameter of the solid particles and the bulk concentration. The predictions,Äô results were successfully compared with the measurements. The study demonstrates the importance of solid particle diameter and showed that using a standard wall damping function gives higher friction compared to measurements. The main objective of this study is to present a mathematical model for medium slurry flow in a vertical pipeline, including a specially designed wall damping function, and to demonstrate the influence of solid particle size on frictional head loss. The effect of mean particle diameter and solid concentration on frictional head loss has been discussed and conclusions were formulated.
Download or read book Slurry Flow written by C A Shook and published by Elsevier. This book was released on 2013-10-22 with total page 337 pages. Available in PDF, EPUB and Kindle. Book excerpt: Slurry Flow: Principles and Practice describes the basic concepts and methods for understanding and designing slurry flow systems, in-plan installations, and long-distance transportation systems. The goal of this book is to enable the design or plant engineer to derive the maximum benefit from a limited amount of test data and to generalize operating experience to new situations. Design procedures are described in detail and are accompanied by illustrative examples needed by engineers with little or no previous experience in slurry transport. The technical literature in this field is extensive: this book facilitates its use by surveying current research results and providing explanations of mechanistic flow models. This discussion of background scientific principles helps the practitioner to better interpret test data, select pumps, specify materials of construction, and choose measuring devises for slurry transport systems. The extensive range of topics covered in Slurry Flow: Principles and practice includes slurry rheology, homogeneous and heterogeneous slurry flow principles, wear mechanisms, pumping equipment, instrumentation, and operating aspects.
Download or read book On line Slurry Viscosity and Concentration Measurement as a Real time Waste Stream Characterization Tool 1998 Annual Progress Report written by and published by . This book was released on 1998 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: This project seeks to develop an on-line sensor to measure the viscosity of dense slurries. This report summarizes work after two years of a three year project. The flow behavior of slurries is important for many of the proposed unit operations to be used in the conveying and processing of tank wastes. One alternative for determining the rheological properties of such materials is to obtain samples and test them off-line using conventional rheometers. Such a protocol is not practical for a wide variety of wastes. Rather, it is the goal of this work to find on-line, in-process techniques for measurement. There are two systems that the authors have propose examining: (1) Nuclear magnetic resonance imaging (NMRI), and, (2) Ultrasonic Doppler Velocimetry. Central to both of these techniques is the measurement of velocity profiles in pipe flows. For the NMRI measurements, the presence of particles has two principal effects on the NMRI velocity profiles: a decrease in signal intensity and image blurring. Similar effects are observed in turbulent flows due to the local random fluctuations in the flow. This similarity has led us to turbulent flow using NMRI. The governing equations for the signal obtained by NMRI are the Bloch-Torrey equations. Previously, the author showed a relationship between turbulent fluctuations and spatial signal intensity variations, assuming isotropic turbulence. However, this assumption does not reflect the true nature of turbulence in a pipe flow where the turbulence is not isotropic. In the new work the Bloch-Torrey equations will be solved by first, time averaging and then employing a turbulence model for pipe flow. The purpose of the time averaging is to smooth the fluctuations of time scale smaller than that of NMRI data acquisition. After this work with single phase fluids, the authors shall undertake NMRI experiments of slurry flow. Various operational parameters will be optimized during the experiments to obtain velocity profile of the flow. Pressure drops will also be recorded to obtain shear stress distribution. Plot of shear stress versus the shear rate, obtained from the velocity profile, will yield the shear viscosity over a wide range of shear rate. The velocity images will also be analyzed to compare the effects of fluctuations with those of turbulent flow experiments For single phase fluids, the NMRI and the UDV work will be compared with measurements using LAV. In their LAV, flow apparatus, the working fluid, water, is gravity fed from a reservoir into a horizontal one inch Pyrex tube, 180 diameters in length. The system enables traverses of the optical probe in the horizontal and vertical directions, with a resolution of 200 micrometers. Radial distributions of the axial component of velocity were obtained at a location 150 diameters from the tube entrance. Measurements in the laminar regime indicate a precision of within one percent, as indicated by the root mean square fluctuations. In the turbulent regime, radial profiles of the mean and fluctuation velocities agree with literature values. In the laminar regime, symmetry of the radial velocity distribution was observed in the horizontal plane passing through the axis, but was not in general observed in the vertical plane passing through the axis. Further investigation revealed that the asymmetry was a result of buoyancy due to heat transfer between the working fluid and the surroundings, even though the pipe was not actively heated or cooled. Temperature differences as little as 1 degree Celsius were found to result in significant asymmetry. To have a reproducible result in the laminar regime, it was necessary to control the reservoir temperature to within 0.1 degree Celsius.
Download or read book Slurry Flow in Vertical Pipes written by Robert H. Wing and published by . This book was released on 1972 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 836 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Numerical Study of Turbulent Pipe Flow written by David Masser Irwin and published by . This book was released on 1990 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Progress Report on Friction Loss of Slurries in Straight Tubes written by Glenn Murphy and published by . This book was released on 1954 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Numerical Study of Fully Developed Turbulent Pipe Flow written by Yansi Zhang and published by . This book was released on 1996 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1961 with total page 1096 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Particle Concentration Measurements in a Centrifugal Slurry Pump Using an A Scan Ultrasound Technique written by John Michael Furlan and published by . This book was released on 2011 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the design of slurry transport equipment used in a variety of industries, the effects of solid particle concentration on hydraulic performance and wear need to be considered. An ultrasound A-mode imaging method has been developed to obtain local particle concentration measurements in slurry flows. Acoustic properties of slurry flows including velocity, backscatter, and attenuation as a function of volume fraction of solid particles, are examined in this study using various transducers. The most suitable transducer is selected to obtain concentration measurements in slurry flows. The technique is used to obtain concentration profiles in a homogeneous (vertical flow) and a non-homogeneous (horizontal flow) slurry flow of soda lime glass beads (195 μm diameter) and water through a one inch diameter loop with solid particle concentrations ranging from 1-10 % by volume. For horizontal flow, profiles are obtained for average flow velocities of 1.2, 2.0, 3.0, and 3.5 m/s. The algorithm developed utilizes acoustic backscatter and attenuation measurements obtained from the homogeneous loop as calibration data in order to obtain concentration profiles in other (i.e. non-homogenous) flow regimes. A computational study using FLUENT is performed and a comparison is made with the experimental results. A reasonable agreement between the experimental and computational results is observed in the one inch pipe. Following transducer selection and refinement and validation of the technique, it is employed to obtain local particle concentration measurements at multiple locations within the casing of a centrifugal slurry pump. A comparison is made between the experimental results and computational results using a two phase Eulerian-Eulerian finite element model. Computational fluid dynamics (CFD) and Experimental results at locations F→I share the same trends and relative patterns for differing locations but have substantial differences in magnitude. The CFD consistently shows higher concentration magnitudes than the experimental data. These differences are most likely a result of an un-matched casing inlet concentration boundary condition.
Download or read book Optical Measurements of Mixing Processes in Turbulent Fluid Flows written by Huixin Li and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many processes in chemical engineering and oceanography rely on fluid mixing. This thesis focuses on optical measurement techniques to experimentally investigate miscible liquid-liquid mixing and gas-liquid mixing. Previous numerical studies have examined the turbulent small-scale mixing, which is experimentally challenging because of the limited spatial resolution of the measurement techniques. A further difficulty emerges for active fluid mixing. When fluids of different densities, such as water and ethanol are mixed, experimental measurements for the small-scale fluctuations in turbulence are impeded by the optical distortion due to the spatio-temporally varying refractive index field. In this thesis, in order to investigate small-scale liquid-liquid mixing, an upscaled T-mixer was built with a height of 40 millimetres. A planar laser-induced fluorescence (PLIF) with high resolution was employed in proof-of-concept experiments concerning the T-junction. The results indicate that measuring the small-scale mixing in the viscous-convective range where the velocity does not fluctuate, but the scalar does, is possible. Subsequently, long inlet channels were added to the T-junction and the particle image velocimetry (PIV) technique was used to verify the fully developed laminar flows and to investigate the flow regimes for different Reynolds numbers. It was found that the present setup can achieve inlet conditions with fully developed laminar flows when the Reynolds number is smaller than 1100. The setup was validated by repeating the flow regimes in previous studies. However, small temperature differences had a weak effect on flow regimes, which should be avoided in the next measurements. Overall, high-quality measuring of the small-scale mixing dynamics in the T-mixer is now within reach. For active mixing with fluids of different densities, mixing usually causes optical measurement errors. In this thesis, a ray tracing simulation method is used in a three-dimensional flow to quantify the measurement errors of the flow velocity and flow acceleration for tracer-based velocimetry, i.e., particle tracking velocimetry (PTV). The flow field is from a direct numerical simulation of single-phase turbulent mixing of two miscible fluids. The measurement errors increase with increasing the refractive index difference. The errors of both velocity and acceleration are attributed to the spatial and the spatio-temporal gradients of the refractive indices. Since PTV, PIV and PLIF share the same working principles based on geometric optics, the findings are also assumed to hold for the measurements of other techniques. The thermal effect in the T-mixer on the measurement errors is subsequently estimated and found to be negligible. Finally, gas-liquid mixing is examined, in which a weakly soluble gas is transferred across the gas-liquid interface. This process is related to the climate balance and depends on surface waves and turbulence underneath the water in the ocean. Utilizing the refraction at the interface and optical displacements, a synthetic Schlieren method is developed to measure the surface topography. This method is implemented in experiments and allows high-accuracy measurements of free surface waves. This makes it feasible to implement simultaneous measurements of surface waves, mass transportation and turbulence under the water.
Download or read book Energy Research Abstracts written by and published by . This book was released on 1992 with total page 806 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Development of an On line Concentration Sensor for Slurry Flow Through Large diameter Pipes written by James F. Klausner and published by . This book was released on 1998 with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Velocity and Concentration Fluctuations in Concentrated Solid liquid Flows written by Seyed Abdolreza Hashemi and published by . This book was released on 2013 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: The aim of this research was to investigate experimentally the turbulent flow of concentrated slurries in horizontal pipelines and to improve the fundamental understanding of mechanism(s) that govern these. High speed Electrical Impedance Tomography (EIT) was combined with advanced signal processing techniques to develop a measurement procedure to obtain solids concentration distributions and turbulent intensity profiles in a highly concentrated solid-liquid mixture. Specific Energy Consumption (SEC), which is a measure of transport eficiency, was used to find the optimum operating condition for heterogeneous (settling) slurry flows. The effects of solids concentration, mixture velocity and particle diameter on SEC were determined using the equivalent-fluid and near-wall lift models for fine- and coarse-particle slurries, respectively. The analysis shows that the minimum SEC occurs at a solids concentration of approximately 30% by volume. Model predictions were compared with the results of numerous experimental studies. In spite of the utility of phenomenological models, such as the near-wall lift model, many fundamental questions in solid-liquid flows remain. Issues include the poor understanding of the mechanisms that govern these complex flows, and the lack of local parameters measured and available for model validation studies. Among the various parameters, solids and liquid concentration fluctuations and turbulent intensities are arguably the most important pieces of information that need to be measured. In horizontal slurry pipe flows, solids velocity and concentration fluctuations were measured for concentrated sand-water mixtures (20 - 35% solids by volume). Slurries of narrowly sized sand (d50 = 100 um) were tested in a 52 mm (i.d.) pipe loop at different mixture velocities (2 - 5 m/s) that were significantly above the deposition velocity. The results showed that the magnitude of the local solids concentration fluctuations is greater near the pipe wall and increases as the mixture velocity increases. Additionally, the concentration fluctuations are greater near the pipe invert, particularly at lower mixture velocities and/or concentrations where the solids concentration profiles are asymmetric. Experiments were also carried out in a 10.16 cm (i.d.) solid-liquid fluidized bed using 2, 3 and 4 mm mono-sized spherical glass beads with water as the continuous phase. A reduced solids concentration in the central region of the bed, which is known to occur during the bubbly (aggregate) fluidization regime, was observed. This study provides further insight into the dynamic behaviour of liquid-solid fluidized beds through the measurement of local solids concentration fluctuations.
Download or read book Pipeline Flow of Coarse Particles in Fluids with Yield Stresses written by and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Horizontal pipe flow of coarse particle slurries with carrier fluids which exhibited yield stresses were examined. Experimental measurements were made to investigate the effect the fluid yield stresses had on the transport of the coarse particles (1.7 mm and 4.4 mm) in a 52 mm diameter pipeloop. These results were used to evaluate two numerical models intended to describe these flows. Experimental tests used clay suspensions which were found to follow the Bingham fluid model. The suspensions had large yield stresses (3 to 25 Pa) which were capable of supporting the particles when the fluid was stationary. These particles were relatively large in relation to the pipe size. Slurry flows were mostly laminar but turbulent flows were also observed. The first numerical model considered the laminar flow of slurries by representing them as continua with a viscosity which varied with position in the pipe. A finite element method was used to predict the velocity distribution in the pipe from a specified pressure gradient and coarse particle concentration profile. This velocity distribution was then used to predict the concentration distribution based on a dispersive mechanism in laminar flow. The second numerical model was also mechanistically based and represented the slurries as two stratified layers with different coarse particle concentrations. This model was used for both laminar and turbulent flow. The effects of the fluid yield stresses on model predictions were considered.
Download or read book Theoretical Chemical Engineering Abstracts written by and published by . This book was released on 1986 with total page 954 pages. Available in PDF, EPUB and Kindle. Book excerpt:
