The Mapping of Flow Regimes for a Light Material: Cork

2003 ◽  
Author(s):  
Joseph S. Mei ◽  
Esmail R. Monazam ◽  
Lawerence J. Shadle
Keyword(s):  
Mathematical Models ◽  
Flow Regime ◽  
Fluidized Bed ◽  
Density Ratio ◽  
Flow Regimes ◽  
Ambient Air ◽  
Gas Velocity ◽  
Dense Phase ◽  
Empirical Correlations ◽  
Light Material

A series of experiments was conducted in the 0.3-meter diameter circulating fluidized bed test facility at the U.S. Department of Energy’s National Energy Technology Laboratory (NETL). Cork, the bed material used in this study, is a coarse, light material, with a particle density of 189 kg/m3 and a mean diameter of 1007 μm. Fluidizing this material in ambient air provides approximately the same gas to solids density ratio as coal and coal char in a pressurized gasifier. Furthermore, the density ratio of cork to air under ambient conditions is similar to the density ratio of coal to gas at the gasification and pressurized fluidized bed combustion environment. The purpose of this study is to generate reliable data to validate the mathematical models currently under development at NETL. Using such coarse, light material can greatly facilitate the computation of these mathematical models. This paper presents and discusses data for the operating flow regimes of dilute-phase, fast-fluidization, and dense-phase transport by varying the solid flux (Gs) at a constant gas velocity (Ug). Data are presented by mapping the flow regime for coarse cork particles in a ΔP/ ΔL-Gs-Ug plot. The coarse cork particles exhibited different behavior than the measurements on heavier materials found in published literature, such as alumina, sand, FCC, and silica gel. Stable operation can be obtained at a fixed riser gas velocity that is higher than the transport velocity (e.g. at Ug = 3.2 m/sec), even though the riser is operating within the fast fluidization flow regime. Depending upon the solid influx, the riser can also be operated at dilute-phase or dense-phase flow regimes. Experimental data were compared to empirical correlations in published literature for flow regime boundaries, and solid fractions in the upper-dilute and the lower-dense regions of a fast fluidization flow regime. Comparisons of measured data show rather poor agreement with these empirical correlations. Xu et al. (2000) have observed this lack of agreement in their study of the effect of bed diameter on the saturation carrying capacity. The basis of empirical correlations depends on bed diameter and particle type, and are generally not well understood.

Flow Regime Study of a Light Material in an Industrial Scale Cold Flow Circulating Fluidized Bed

2006 ◽  
Vol 128 (2) ◽  
pp. 129-134 ◽  
Author(s):  
Joseph S. Mei ◽  
Esmail R. Monazam ◽  
Lawrence J. Shadle
Keyword(s):  
Experimental Data ◽  
Mathematical Models ◽  
Flow Regime ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Density Ratio ◽  
Gas Velocity ◽  
Dense Phase ◽  
Empirical Correlations ◽  
Light Material

A series of experiments was conducted in the 0.3meter diameter circulating fluidized bed test facility at the National Energy Technology Laboratory (NETL) of the U. S. Department of Energy. The particle used in this study was a coarse, light material, cork, which has a particle density of 189kg∕m3 and a mean diameter of 812μm. Fluidizing this material in ambient air approximates the same gas-solids density ratio as coal and coal char in a pressurized gasifier. The purpose of this study is twofold. First, this study is to provide a better understanding on the fundamentals of flow regimes and their transitions. The second purpose of this study is to generate reliable data to validate the mathematical models, which are currently under development at NETL. Utilization of such coarse, light material can greatly facilitate the computation of these mathematical models. Furthermore, the ratio of density of cork to air under ambient conditions is similar to the density ratio of coal to gas at the gasification and pressurized fluidized bed combustion environment. This paper presents and discusses the data, which covered operating flow regime from dilute phase, fast fluidization, and to dense phase transport by varying the solid flux, Gs at a constant gas velocity, Ug. Data are presented by mapping the flow regime for coarse cork particles in a ΔP∕ΔL‐Gs‐Ug plot. The coarse cork particles exhibited different behavior than the published literature measurements on heavier materials such as alumina, sand, FCC, silica gel, etc. A stable operation can be obtained at a fixed riser gas velocity higher than the transport velocity, e.g., at Ug=3.2m∕s, even though the riser is operated within the fast fluidization flow regime. Depending upon the solids influx, the riser can also be operated at dilute phase or dense phase flow regimes. Experimental data were compared to empirical correlations in published literature for flow regime boundaries as well as solids fractions in the upper dilute and the lower dense regions for fast fluidization flow regime. Comparisons of measured data with these empirical correlations show rather poor agreements. These discrepancies, however, are not surprising since the correlations for these transitions were derived from experimental data of comparative heavier materials such as sands, FCC, iron ore, alumina, etc.

Computational analysis of the particle size effect on the pressure profiles and type of flow regimes of TiO2 microparticles in a fluidized bed

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Alireza Bahramian
Keyword(s):  
Particle Size ◽  
Flow Regime ◽  
Fluidized Bed ◽  
Fluid Dynamic ◽  
Pressure Fluctuations ◽  
Flow Regimes ◽  
Particle Size Effect ◽  
Pressure Profiles ◽  
Effect Of Particle Size ◽  
Drag Models

Abstract The effect of particle size on the pressure profiles and flow regimes of the bed containing TiO2 microparticles (MPs) was investigated in a fluidized bed. The fluidization behavior of particles with mean diameters, d p , of 170, 200, 225, and 300 μm at different gas velocities, U g , was investigated both experimental and computational viewpoints. A computational fluid dynamic (CFD) model was developed by the Eulerian–Eulerian approach to evaluate the sensitivity of the Syamlal–O’Brien, and Gidaspow drag models on the predicted results of the bed pressure profiles. The results showed that with increasing particle size, the amplitude of pressure fluctuations increases and the type of flow regime in the bed tended from bubbling to slugging flow regime. The error analysis showed that the use of the Gidaspow model led to more accurate results than the Syamlal–O’Brien model in predicting the bed pressure drop and pressure fluctuations in the slugging flow regime. However, the Syamlal–O’Brien model was more suitable for predicting the pressure profiles in the bubbling flow regime. The results were more suitable for the bed containing particles of 300 μm than the beds with d p  ≤ 225 μm. The highest and lowest deviations between the experimental data and simulation outputs were obtained at U g of 0.295 and 0.650 m/s, respectively. The findings confirmed that the mutual effects existed between the d p pressure profiles, and the type of flow regimes in the bed.

Bubble Characteristics in a Developing Vertical Gas–Liquid Upflow Using a Conductivity Probe

1999 ◽  
Vol 122 (1) ◽  
pp. 138-145 ◽  
Author(s):  
Junping Zhang ◽  
Norman Epstein ◽  
John R. Grace ◽  
Kokseng Lim
Keyword(s):  
Flow Regime ◽  
Slug Flow ◽  
Flow Region ◽  
Flow Regimes ◽  
Chord Length ◽  
Bubble Velocity ◽  
Gas Velocity ◽  
Bubble Frequency ◽  
Local Bubble ◽  
Bubble Characteristics

Experiments were carried out in an 82.6-mm-dia column with a perforated distributor plate. Conductivity probes on the axis of the column were used to measure local bubble properties in the developing flow region for superficial air velocities from 0.0018 to 6.8 m/s and superficial water velocities from 0 to 0.4 m/s, corresponding to the discrete bubble, dispersed bubble, coalesced bubble, slug, churn, bridging, and annular flow regimes. Bubble frequency increased linearly with gas velocity in the discrete and dispersed bubble regimes. Bubble frequency also increased with gas velocity in the slug flow regime, but decreased in the churn and bridging regimes. Bubble chord length and its distribution were smaller and narrower in the dispersed than in the discrete bubble regime. Both the average and standard deviation of the bubble chord length increased with gas velocity in the discrete, dispersed, and churn flow regimes. However, the average bubble chord length did not change significantly in the slug flow regime due to the high population of small bubbles in the liquid plugs separating Taylor bubbles. The bubble travel length, defined as the product of local gas holdup and local bubble velocity divided by local bubble/void frequency, is used to correlate bubble characteristics and to characterize the flow regimes. [S0098-2202(00)00101-2]

Hydrodynamic review on liquid–solid magnetized fluidized bed

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Quanhong Zhu ◽  
Qingshan Huang ◽  
Chao Yang
Keyword(s):  
Flow Regime ◽  
Fluidized Bed ◽  
Flow Regimes ◽  
Terminal Velocity ◽  
Commercial Application ◽  
Hydrodynamic Characteristics ◽  
Hysteresis Phenomenon ◽  
Regime Transition ◽  
Flow Regime Transition ◽  
The Magnetic Field

AbstractThe magnetic field has been successfully used to intensify the liquid–solid contact performance in the fluidized bed, creating the magnetized fluidized bed (MFB). The MFBs with purely magnetizable particles and with the binary admixture of magnetizable and nonmagnetizable particles could be simply termed the pure MFB and admixture MFB, respectively. Their potential application in the chemical and biochemical industries has been thoroughly explored in the literature. However, a fundamental investigation on the hydrodynamics therein is far from sufficient, severely hindering the commercial application. For this reason, this review summarized the relevant findings, including (1) flow regime transition, (2) boundaries between two adjacent flow regimes, (3) unique features of the magnetically stabilized bed, (4) hysteresis phenomenon and bed voidage, (5) minimum fluidization velocity and terminal velocity, (6) numerical simulation and segregation of the admixture MFB, and (7) some explored applications. More importantly, the existing controversies and unsolved issues in this area were identified. Among others, the flow regime transition and unique hydrodynamic characteristics of each flow regime should be first clarified, only after which could the terminology describing all the flow regimes be unified and the results from different scholars be compared.

Investigating the particle dispersion in a spout-fluid bed using particle trajectory

2012 ◽  
Vol 10 (1) ◽  
Author(s):  
Yong Zhang ◽  
Wenqi Zhong ◽  
Baosheng Jin ◽  
Rui Xiao
Keyword(s):  
Flow Regime ◽  
Fluidized Bed ◽  
Particle Trajectory ◽  
Particle Dispersion ◽  
Axial Dispersion ◽  
Gas Velocity ◽  
Infrared Thermal Imaging ◽  
Fluid Bed ◽  
Radial Dispersion ◽  
Series Of Experiments

Abstract Particle dispersion in a spout-fluid bed was investigated using time series of particle trajectory by evaluation of dispersion coefficient based on Einstein’s expression. A series of experiments were performed in a lab-scale spout-fluid bed using microwave heating and infrared thermal imaging (MH-ITI) technique for recording the position of a tracer. The influence of gas velocity on the particle dispersion in different flow regimes has been taken into account. The results show that the particle dispersion behavior depends on the flow regime. In the flow regime of internal jet, the increase of gas velocity improves the axial dispersion. In the case of jet in fluidized bed with bubbling, increasing fluidizing gas velocity promotes the radial dispersion at the lower part of bed and the axial dispersion at the upper part of bed. In the flow regime of jet in fluidized bed with slugging, the effect of fluidizing gas is related to the slug pattern. The result also indicates that the transition of flow regime can be evaluated from the particle trajectory.

The influences of bathymetry and flow regime upon the morphology of sublittoral sponge communities

2000 ◽  
Vol 80 (4) ◽  
pp. 707-718 ◽  
Author(s):  
James J. Bell ◽  
David K.A. Barnes
Keyword(s):  
Turbulent Flow ◽  
Flow Regime ◽  
Current Flow ◽  
Volume Ratio ◽  
Basal Area ◽  
Morphological Diversity ◽  
Flow Regimes ◽  
High Energy ◽  
Similarity Analysis ◽  
Lough Hyne

Sponge communities were sampled at 3 m depth intervals at six sites experiencing different flow regimes at Lough Hyne, Ireland. Sponges were identified and classified within the following morphological groups: encrusting, massive, globular, pedunculate, tubular, flabellate, arborescent, repent and papillate morphological types on both vertical (≈90°) and inclined (≈45°) surfaces.Differences in the proportional abundance of the sponge body forms and density (sponge m−2) were observed between sites and depths. The density of sponges increased with depth at sites of slight to moderate current flow, but not at the site where current flow was turbulent. Morphological diversity of sponge communities decreased with increasing current flow due to the removal of delicate forms such as pedunculate and arborescent shaped sponges. Massive and encrusting morphologies dominated at the high-energy sites (fast and turbulent flow regimes) due to a high basal area to volume ratio, which prevents removal from cliff surfaces. However, pedunculate, papillate and arborescent types dominated at the low current sites as these shapes may help to prevent the settlement of sediment on sponge surfaces. Bray–Curtis Similarity analysis and Correspondence Analysis were used to distinguish between five different morphological communities.

3D Numerical Simulation of Polydisperse Pressurized Gas-Solid Fluidized Bed

2011 ◽  
Author(s):  
P. Fede ◽  
O. Simonin ◽  
I. Ghouila
Keyword(s):  
Numerical Simulation ◽  
Fluidized Bed ◽  
Ethylene Polymerization ◽  
Solid Phase ◽  
Three Dimensional ◽  
Gas Velocity ◽  
Particle Segregation ◽  
3D Numerical Simulation ◽  
Model Predictions ◽  
The Mean

Three dimensional unsteady numerical simulations of dense pressurized polydisperse fluidized bed have been carried out. The geometry is a medium-scale industrial pilot for ethylene polymerization. The numerical simulation have been performed with a polydisperse collision model. The consistency of the polydisperse model predictions with the monodisperse ones is shown. The results show that the pressure distribution and the mean vertical gas velocity are not modified by polydispersion of the solid phase. In contrast, the solid particle species are not identically distributed in the fluidized bed indicating the presence of particle segregation.

Flow and Energy Loss Downstream of Rectangular Sharp-Crested Weirs for Free and Submerged Flows

2021 ◽  
Author(s):  
Mahmud R. Amin ◽  
Nallamuthu Rajaratnam ◽  
David Z. Zhu
Keyword(s):  
Energy Loss ◽  
Flow Regime ◽  
Analytical Study ◽  
Flow Characteristics ◽  
Turbulent Jets ◽  
Flow Regimes ◽  
Impinging Jet ◽  
Relative Energy ◽  
Surface Flow ◽  
Upper Stage

Abstract This work presents an analytical study of the flow and energy loss immediately downstream of rectangular sharp-crested weirs for free and submerged flows, using the theory of plane turbulent jets and the analysis of some relevant studies. The flow regimes downstream of the sharp-crested weir is characterized as the impinging jet and surface flow regimes. Based on the flow characteristics and the downstream tailwater depths, each flow regime is further classified, and the relative energy loss equation is developed. It is found that significant energy loss occurs for the regime of supercritical flow and the upper stage of impinging jet flow. The energy loss for the submerged flow regime is minimal.

Sign in / Sign up

Export Citation Format

Share Document