Numerical simulation of fluid flow in CFB risers: A turbulence analysis approach

Cabezas‐Gómez, Luben; Milioli, Fernando Eduardo

doi:10.1590/s1678-58782005000200006

Cited by 8 publications

(3 citation statements)

References 10 publications

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“…However, there is also a quantitative criterion for the minimum mesh control volume on which the volume averaged Eulerian-Eulerian continuum equations are valid for the solid phase. 41,42,43 Satisfying this condition for the range of volume fractions obtained in all mesh elements is cumbersome when realistic particle sizes and high eccentricities (similar to actual drilling campaigns) are considered: this is an inherent limitation of the continuum assumption employed for large particles, although convergence is always achieved. The application of Lagrangian-Eulerian models (specifically, Macroscopic Particle Models/MPM) tailored towards a more accurate description of large particles (bigger than a single mesh element in the lower annular section) can further reduce the prediction error, but at a higher computational cost.…”

Section: A N U S C R I P Tmentioning

confidence: 99%

CFD modelling and simulation of drill cuttings transport efficiency in annular bends: Effect of particle sphericity

Epelle

Gerogiorgis

2018

Journal of Petroleum Science and Engineering

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Accurate prediction of the flow behaviour of drill cuttings carried by a non-Newtonian fluid in an annular geometry is important for the successful and efficient design, operation, and optimisation of drilling operations. Although it is widely recognised that practical drilling operations hardly involve perfectly spherical cuttings, the relative ease in mathematical description coupled with speedy computation are the main reasons for the prevalence of this simplifying assumption. The possibilities offered by the modification of the interphase exchange coefficient of the Syamlal-O'Brien model as well as its scarce implementation in literature have motivated the authors to delve into this area of research as far as the transport phenomena of non-spherical drill cuttings is concerned. Another aspect of this work was influenced by the need to understand the flow dynamics around bends (horizontal to inclined and inclined to vertical sections) during deviated drilling operations using two high viscosity muds (0.5% CMC and 0.5% CMC + 4% Bentonite mud). The Eulerian-Eulerian model was adopted for this study while considering particle sphericities of 0.5, 0.75 and 1 and diameters of 0.002 m, 0.003 m, 0.004 m, 0.005 m and 0.008 m respectively. It was discovered that particle deposition intensifies at the inclined-to-vertical bend compared to other locations in the flow domain. We also observe increased dispersion effects and transport velocities of non-spherical particles compared to particles of a perfectly spherical geometry. Furthermore, an improvement in the rheological properties of the drilling mud shows a remarkable increase in cuttings transport efficiency especially with the smaller particles. However, increased deposition of larger particles still poses a challenge to the wellbore cleaning process despite this rheological enhancement. The proposed CFD modelling methodology is thus capable of providing critical insight into the dynamics of cuttings transport, and the resulting computational observations are consistent with relevant experimental investigations.

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Section: A N U S C R I P Tmentioning

confidence: 99%

CFD modelling and simulation of drill cuttings transport efficiency in annular bends: Effect of particle sphericity

Epelle

Gerogiorgis

2018

Journal of Petroleum Science and Engineering

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“…The development of a mathematical model for drum type boilers requires a combination of non-linear equations, to describe the evaporation in the vertical tubes and the phase separation in the steam drum as shown by Adam, E.J, Marchetti, and J.L [17]. L. C. Gómez, F. E. Milioli [18], & M.H. Zhang et al [19] studied two phase flow inside the risers, while H.E.…”

Section: Introductionmentioning

confidence: 99%

Boiler Drum-Level Modeling

Tawfeic

2013

JES. Journal of Engineering Sciences

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In this paper, a mathematical model is developed to describe the dynamics of the drum-level of a natural circulation boiler. A boiler-drum is divided into two parts; the upper part contains saturated steam while the lower part contains a steam/water mixture. The ratio of the steam in that mixture is defined in this work as the steam volumetric ratio. On the other hand, balance equations are applied to the drum. The resulting equations are used to model the drum-level. The importance of the resulting model comes from the direct modeling of drum level which is usually computed off-line with the aid of empirical formulas and assumptions. Safe operation of boilers requires perfect level controller which cannot be designed without proper modeling. Simulation of the water level dynamics for step changes in heat rate and steam demand are compared with those in the literature. The results show that the drum level can be obtained from the basic balance equations.

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“…They observed that during fluidization, the motion of solid particles upward in the fluidized bed is in the form of groups or clusters. They observed that the clusters are in the form of horizontal strands.Gomez and Milioli[30] observed that the traditional two fluid model adequately captured the mean macroscopic features of the gas-solid flows in a circulating fluid bed riser. This includes particle clustering along with annular plug flow patterns.…”

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confidence: 99%

Investigation of Rope Formation in Gas-Solid Flows using Flow Visualization and CFD Simulations

Guda¹

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Investigation of Rope Formation in Gas-Solid Flows using Flow Visualization and CFD Simulations Venkata Subba Sai Satish Guda Coal is still one of the widely-used resources for power generation all over the world. Most of the relevant industries use pulverized coal as fuel which is delivered to the furnace by pneumatic conveying. Extensive use of coal has resulted in severe environmental problems due to emissions such as Carbon dioxide, Nitrogen and Sulphur compounds among others. It is postulated that if combustion efficiency is improved, this will lead to significant reduction in pollutant emissions. Combustion efficiency of pulverized coal power plants is influenced strongly by particle size distribution. Most industries use Cyclone Separators (or Classifiers) to separate the larger particles from the smaller ones as part of pre-combustion processes. The sizing and scaling of these classifiers are mostly based on empirical formulations. Detailed 3D numerical studies of these classifiers have not been successful in prediction of experimental observations, hence as such cannot be used as reliable tools for scale up studies. The main reason for this anomaly is believed to be failure of the models in capturing the dynamics of particle behavior in bends and ducts where particles form rope like structures with dense particle clusters. It is then imperative that more study is needed into the understanding of rope or cluster formation in gas-solid flows. My heartfelt thanks and salutations to my grandfather Dr. K. Sivananda Murthy garu for directing me, guiding me and making me achieve my PhD goal. He has always provided solutions to all the problems in such a manner that the problem never existed or reappeared later. Without him, this goal of PhD would have always remained a dream. Of course there is no question of him not being there for me. This degree is dedicated to him.

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Numerical simulation of fluid flow in CFB risers: A turbulence analysis approach

Cited by 8 publications

References 10 publications

CFD modelling and simulation of drill cuttings transport efficiency in annular bends: Effect of particle sphericity

CFD modelling and simulation of drill cuttings transport efficiency in annular bends: Effect of particle sphericity

Boiler Drum-Level Modeling

Investigation of Rope Formation in Gas-Solid Flows using Flow Visualization and CFD Simulations

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