The Experts below are selected from a list of 10497 Experts worldwide ranked by ideXlab platform
Zh X Zeng - One of the best experts on this subject based on the ideXlab platform.
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a two scale second order moment particle turbulence model and simulation of dense gas particle Flows in a riser
Powder Technology, 2006Co-Authors: Zh X Zeng, L X ZhouAbstract:Abstract A two-scale second-order moment particle turbulence model is developed, based on the concept of particle large-scale fluctuation due to turbulence and particle small-scale fluctuation due to collision. It is then used to simulate dense gas–particle Flows in a riser. The predicted results are in reasonable agreement with the experimental results and show the core-Annulus Flow structure observed in experiments. It is seen that the two-scale model is somewhat better than kf–ef–kp–ep–θ two-phase turbulence model and the single-scale second-order moment two-phase turbulence model (USM–θ model).
L X Zhou - One of the best experts on this subject based on the ideXlab platform.
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a two scale second order moment particle turbulence model and simulation of dense gas particle Flows in a riser
Powder Technology, 2006Co-Authors: Zh X Zeng, L X ZhouAbstract:Abstract A two-scale second-order moment particle turbulence model is developed, based on the concept of particle large-scale fluctuation due to turbulence and particle small-scale fluctuation due to collision. It is then used to simulate dense gas–particle Flows in a riser. The predicted results are in reasonable agreement with the experimental results and show the core-Annulus Flow structure observed in experiments. It is seen that the two-scale model is somewhat better than kf–ef–kp–ep–θ two-phase turbulence model and the single-scale second-order moment two-phase turbulence model (USM–θ model).
Weiyong Ying - One of the best experts on this subject based on the ideXlab platform.
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ldv measurements of particle velocity distribution and annular film thickness in a turbulent fluidized bed
Powder Technology, 2017Co-Authors: Yongzheng Li, Tao Li, Haitao Zhang, Weiyong YingAbstract:Abstract Local particle velocity and annular film thickness in a 4.8 m-high, 0.15 m-ID turbulent fluidized bed (TFB) were determined with a Laser Doppler Velocimeter (LDV) at several axial heights. The effects of superficial gas velocities (0.47–0.94 m/s), initial bed heights (0.3–0.5 m), and particle sizes (mean diameter is 164 μm and 89 μm, respectively) on particle velocity and annular film thickness were investigated at ambient conditions. When superficial gas velocity or initial bed height was increased, the radial profile of particle velocity became significantly non-uniform. Additionally, the core-Annulus Flow pattern was observed in TFB. The annular film layer narrowed along the axis, but widened with the increase of initial bed height or superficial gas velocity. When compared particles with diameter of 164 μm, the smaller particles were more sensitive to the change of operating conditions. The particles with diameter of 89 μm showed more non-uniform radial profiles of particle velocity and a wider Annulus. Based on effects of operating conditions, measurement height, and particle sizes, a new correlation was developed to predict the annular film thickness in turbulent fluidized bed. A good agreement was obtained between the predicted results and experimental data.
Kenneth E. Gray - One of the best experts on this subject based on the ideXlab platform.
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Investigating the effects of plug viscosity on annular pressure drop and cuttings transport in a concentric Annulus
Journal of Natural Gas Science and Engineering, 2020Co-Authors: Shiraz Gulraiz, Kenneth E. GrayAbstract:Abstract The API recommended approach to model the rheology of a drilling fluid is to use the Herschel Bulkley equation. This equation breaks down as shear rate approaches zero and predicts infinite viscosity at zero shear rate limit. In an Annulus, shear rate can drop to values approaching zero and the use of Herschel Bulkley equation in Flow models can lead to inaccurate prediction of drilling hydraulics. This paper investigates the effects of zero shear rate viscosity, called plug viscosity, on annular pressure drop and cuttings transport predictions in a concentric Annulus. Flow is modeled using the mixture model approach and is simulated using computational fluid dynamics (CFD) methodology. The rheology of the drilling fluid is characterized using a modified bi-viscosity function. The first half of this paper examines the effect of common drilling parameters on the existence of plug zones, regions with zero shear rate viscosity, whereas the second half of this paper investigates the effects of plug viscosity on annular pressure profile and cuttings transport. The results show that plug viscosity has a significant impact on annular pressure profile and cuttings transport predictions. The same set of Herschel Bulkley parameters can produce different values of annular pressure drop and volumetric cuttings concentration if plug viscosity is ignored. Therefore, to accurately predict annular pressure profile and cuttings transport, it is imperative that plug viscosity is incorporated in the rheological functions.
Boping Liu - One of the best experts on this subject based on the ideXlab platform.
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A CFD-PBM model considering ethylene polymerization for the Flow behaviors and particle size distribution of polyethylene in a pilot-plant fluidized bed reactor
Powder Technology, 2015Co-Authors: Yu Che, Zhou Tian, Zhen Liu, Rui Zhang, Yuxin Gao, Enguang Zou, Sihan Wang, Boping LiuAbstract:Abstract In large-scale industrial fluidized bed reactors (FBRs) for polyethylene (PE) production, the prediction of the interactions between polymerization, gas–solid two phase Flow and particle kinetics is very challenging. This paper aims at providing a new insight into the effects of ethylene polymerization on the particle Flow behaviors and particle size distributions (PSDs) of PE in a pilot-plant FBR via a CFD-PBM modeling approach. An Eulerian–Eulerian two-fluid model involving ethylene polymerization kinetics is coupled with a population balance model (PBM) to track the polymer PSDs. The particle growth, aggregation and breakage are taken into account in the PBM. The predicted pressure drop and temperature agree well with the available experimental data. Compared with the cold-model, the Flow characteristics of polymer particles and the PSDs show noticeable differences in the case of considering polymerization. A slightly higher bed expansion height and lower axial particle velocity are also presented in this case. The core-regions of the core–Annulus Flow structures in terms of the solid concentration and particle velocity are obviously broader than that of the cold-model. Moreover, due to the polymerization reaction and mass/heat transfer effects, more PE particles are concentrated on the middle–upper areas of the FBR. As expected, particle breakage leads to a decrease in the average PE particle diameter and an increase in the bed expansion height.