| 1. |
- van Ommen, J.R., et al.
(författare)
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Optimal placement of probes for dynamic pressure measurements in large-scale fluidized beds
- 2004
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Ingår i: Powder Technology. - : Elsevier BV. - 1873-328X .- 0032-5910. ; 139:3, s. 264-276
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Tidskriftsartikel (refereegranskat)abstract
- Pressure data sampled at sufficiently high frequency (typically 20 Hz or higher) can yield much information about the hydrodynamic state of a fluidized bed. Since part of the pressure waves travelling through large (industrial) fluidized beds is only detectable in a limited area of the bed, pressure measurements need to be performed at several positions to cover the whole bed. We examine these local pressure waves (caused by, e.g., passing bubbles or coalescing bubbles) in a 0.80 m i.d. bubbling fluidized bed of Geldart B particles. Experiments and simulations are performed to determine the intensity decrease as local pressure waves propagate from their origin. A new spectral method is applied to determine the degree of coherence for pressure signals measured at two different positions in a fluidized bed. For a superficial gas velocity of 5u(mf), local pressure waves can be detected up to a radial distance of about 0.5 m from their origin; this distance is somewhat lower for lower gas velocities. This means that the radial spacing of pressure probes should not exceed 1 m. For large diameter beds with a bed height below 1.5 m, a set of probes at a single level and at several radial positions is sufficient to observe or monitor the dynamic state of the complete bed; the probes should preferably be placed at a height of 30% to 40% of the total bed height.
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| 2. |
- Benavides, Aldo, 1978, et al.
(författare)
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Comparison of experimental and simulation results for turbulent gas-solid riser flow
- 2008
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Ingår i: Circulating Fluidized Bed Technology IX. Proceedings of the 9th International Conference on Circulating Fluidized Beds, CFB-9. May 13-16, 2008. Hamburg, Germany..
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Konferensbidrag (refereegranskat)abstract
- This paper compares measurements of the radial solids concentration in a riser with CFD simulations. An Eulerian model based upon the kinetic theory for granular flow, extended with models describing turbulence modulation and dispersion, is used to treat the particulate phase. Coupling between momentum equations of the gas and particulate phases is taken into account via a mean drag force formulation. Solids distribution profiles over three horizontal planes are measured by the use of optical probes. The pressure drop is used to estimate an average solids concentration profile along the riser. The comparison is reported for a single superficial gas velocity and solids mass flux.
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| 3. |
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| 4. |
- van Ommen, Ruud, et al.
(författare)
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Computational validation of the scaling rules for fluidized beds
- 2006
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Ingår i: POWDER TECHNOLOGY. ; 163:1-2, s. 32-40
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Tidskriftsartikel (refereegranskat)abstract
- The scaling rules using dimensionless groups are investigated using CFD simulations of two scaled fluidized beds with diameters of 15 and 36 cm. Three sets of dimensionless groups are used: the simplified set, the full set, and the full set extended with a dimensionless pressure group. Voidage and pressure data for the two scales are compared using different analysis techniques. The full set gives the largest differences between the two scales. The simplified set and the extended set perform better, but neither lead to complete similarity between the two scales.
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| 5. |
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| 6. |
- Andersson, Bengt, 1947, et al.
(författare)
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Computational fluid dynamics for engineers
- 2011
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- © B. Andersson, R. Andersson, L. Håkansson, M. Mortensen, R. Sudiyo, B. vanWachem, L. Hellstr ¨om 2012. Computational fluid dynamics, CFD, has become an indispensable tool for many engineers. This book gives an introduction to CFD simulations of turbulence, mixing, reaction, combustion and multiphase flows. The emphasis on understanding the physics of these flows helps the engineer to select appropriate models to obtain reliable simulations. Besides presenting the equations involved, the basics and limitations of the models are explained and discussed. The book combined with tutorials, project and power-point lecture notes (all available for download) forms a complete course. The reader is given hands-on experience of drawing, meshing and simulation. The tutorials cover flow and reactions inside a porous catalyst, combustion in turbulent non-premixed flow, and multiphase simulation of evaporation spray respectively. The project deals with design of an industrial-scale selective catalytic reduction process and allows the reader to explore various design improvements and apply best practice guidelines in the CFD simulations.
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| 7. |
- Benavides, Aldo, 1978, et al.
(författare)
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Eulerian-Eulerian prediction of dilute turbulent gas-particle flow in a backward-facing step
- 2009
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Ingår i: International Journal of Heat and Fluid Flow. - : Elsevier BV. - 0142-727X. ; 30:3, s. 452-461
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Tidskriftsartikel (refereegranskat)abstract
- A numerical study of turbulent gas-particle flow in a two-dimensional, vertically oriented backward-facing step is compared with literature data. The dispersed phase is modeled by an Eulerian approach based upon the kinetic theory of granular flow (KTGF) including models for describing the dispersed phase interactions with the continuous phase. The modeling of turbulent motion within the dispersed phase and the correlation between gas and particle velocity fluctuations are discussed. In addition, closure relations for the dispersed phase are extended to incorporate interstitial fluid effects. The continuous phase turbulence is modeled by a kappa - epsilon model. This work demonstrates that treatment of turbulent characteristics is a key element in predicting the dispersed phase mean motion and turbulence modulation in the continuous phase. The derived models are implemented in a commercial code and simulation results are compared with benchmark experimental data for three particle classes with distinctive particle Stokes number, particle Reynolds number and mass-loading. In general, reasonable predictions are achieved. (c) 2009 Elsevier Inc. All rights reserved.
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| 8. |
- Benavides, Aldo, 1978, et al.
(författare)
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Numerical computation of turbulent gas-particle flow in a backward-facing step
- 2008
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Ingår i: Proceedings 7th International Symposium on Engineering Turbulence Modelling and Measurements - ETMM7. Limassol, Cyprus, 4-6 June 2008.. ; 1, s. 144-149
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In the present article, a numerical study of turbulent gas-particle flow in a vertically oriented backward-facing step is compared with literature data. The dispersed phase is simulated by an Eulerian approach based upon the kinetic theory for granular flow, including interaction with the continuous phase. The modeling of turbulent motion within the dispersed phase as well as the correlation between gas and particle velocity fluctuations are discussed. This work demonstrates that treatment of such quantities is essential to correctly describe the particulate phase distribution and turbulence modulation in the gas phase. In addition, closure relations for the dispersed phase are extended to incorporate the influence of the continuous fluid. The derived models are validated with benchmark experimental results of a planar sudden expansion turbulent flow including particles. In general, good agreement is found between model predictions and experimental data.
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| 9. |
- Benavides, Aldo, 1978, et al.
(författare)
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Numerical computation of turbulent gas-particle flow in a backward-facing step. Model comparison with experimental data
- 2008
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Ingår i: Proceedings 11th International Conference on Multiphase Flow in Industrial Plants, MFIP 2008. September 7-10, Palermo, Italy.. - 888819813X ; , s. 63-70
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Konferensbidrag (refereegranskat)abstract
- In the present article, the predictions of two models describing turbulent gas-particle flow in a vertically oriented backward-facing step are compared to each other and with literature data. The first model is an Eulerian approach based upon the kinetic theory of granular flow, including turbulence modulation and interaction with the continuous phase. The gas-phase turbulence is predicted by use of a k-epsilon dispersed turbulence model, including inter-phase energy transfer between gas and particle fluctuating motions. The second model also uses an Eulerian approach coupled to a k-omega turbulence model. The latter model considers the transport of particles to the near-wall region due to turbulence intensity gradients, and particulate phase influences on the gas flow. It is shown that the combined effect has an impact on the two-phase flow. The derived models are validated with benchmark experimental results of a planar sudden expansion turbulent flow including particles.
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| 10. |
- Benavides, Aldo, 1978, et al.
(författare)
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Numerical simulation and validation of dilute turbulent gas-particle flow with inelastic collisions and turbulence modulation
- 2008
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Ingår i: Powder Technology. - : Elsevier BV. - 1873-328X .- 0032-5910. ; 182:2, s. 294-306
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Tidskriftsartikel (refereegranskat)abstract
- This work describes a theoretical and numerical study of turbulent gas-particle flows in the Eulerian framework. The equations describing the flow are derived employing Favre averaging. The closures required for the equations describing the particulate phase are derived from the kinetic theory of granular flow. The kinetic theory proposed originally is extended to incorporate the effects of the continuous fluid on the particulate phase behavior. Models describing the coupling between the continuous phase kinetic energy and particulate phase granular temperature are derived, discussed, and their effect on the flow predictions is shown.The derived models are validated with benchmark experimental results of a fully developed turbulent gas-solid flow in a vertical pipe. The effect of the models describing the influence of turbulence on the particle motion as well as the turbulence modulation due to the presence of particles is analyzed and discussed.
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