scholarly journals Segregation and intermixing in polydisperse liquid-solid fluidized beds: A multi-fluid model validation study

2021 ◽  
Author(s):  
Shashank S. Tiwari ◽  
Swapnil V. Ghatage ◽  
Jyeshtharaj Joshi ◽  
Bo Kong
Keyword(s):  
Fluidized Beds ◽  
Fluid Model ◽  
Flow Regimes ◽  
Direct Numerical Simulations ◽  
Particle Interactions ◽  
Rational Closure ◽  
Regime Map ◽  
Bed Expansion ◽  
Flow Regime Map

Multifluid model (MFM) simulations have been carried out on liquid-solid fluidized beds (LSFB) consisting of binary and higher-order polydisperse particle mixtures. The role of particle-particle interactions was found to be as crucial as the drag force under laminar and homogenous LSFB flow regimes. The commonly used particle-particle closure models are designed for turbulent and heterogeneous gas-solid flow regimes and thus exhibit limited to no success when implemented for LSFB operating under laminar and homogenous conditions. A need is perceived to carry out Direct Numerical Simulations of liquid-solid flows and extract data from them to develop rational closure terms to account for the physics of LSFB. Finally, a recommendation flow regime map signifying the performance of the MFM has been proposed. This map will act as a potential guideline to identify whether or not the bed expansion characteristics of a given polydisperse LSFB can be correctly simulated using MFM closures tested.

scholarly journals The role of particle-particle interactions in bubbling gas-fluidized beds of Geldart A particles: A discrete particle study

2010 ◽  
Author(s):  
J. W. Wang ◽  
M. A. van der Hoef ◽  
J. A. M. Kuipers ◽  
Liejin Guo ◽  
D. D. Joseph ◽  
...  
Keyword(s):  
Fluidized Beds ◽  
Particle Interactions ◽  
Discrete Particle ◽  
Gas Fluidized Beds

An Experimental Investigation of Flow Patterns During Condensation of HFC Refrigerants in Horizontal Micro-Fin Tubes

2019 ◽  
Vol 27 (01) ◽  
pp. 1950010
Author(s):  
Sanjeev Singh ◽  
Rajeev Kukreja
Keyword(s):  
Heat Transfer ◽  
Flow Regime ◽  
Flow Regimes ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Horizontal Tubes ◽  
Regime Map ◽  
Fin Tubes ◽  
Flow Regime Map

Condensation heat transfer coefficients and flow regimes in two different horizontal micro-fin tubes are examined during the condensation of refrigerants R-134a and R-410A. The present investigation has focused on determination and prediction of condensation heat transfer coefficients and finding the interrelation between heat transfer coefficients and the prevailing flow regimes. During flow visualization, flow regimes have been captured using borosilicate glass tube at inlet and outlet of the test condenser using high speed digital camera. Stratified, stratified wavy, wavy annular, annular, slug and plug flows have been observed at different mass fluxes and vapor qualities of the refrigerants. The observed flow regimes are compared with the existing flow regime maps proposed by Breber et al. [Prediction of horizontal tube side condensation of pure components using flow regime criteria, J. Heat Transfer 102 (1980) 471–476], Tandon et al. [A new flow regime map for condensation inside horizontal tubes, J. Heat Transfer 104 (1982) 763–768.] and Thome et al. [Condensation in horizontal tubes, part 2: New heat transfer model based on flow regimes, Int. J. Heat Mass Transfer 46 (2003) 3365–3387.] Thome et al. [Condensation in horizontal tubes, part 2: New heat transfer model based on flow regimes, Int. J. Heat Mass Transfer 46 (2003) 3365–3387.] flow regime map shows good agreement with experimental data.

Regimes Map and Transition Boundaries for Immiscible Liquids Flow in Co-Axial Microtubes

2013 ◽  
Author(s):  
In-Hwan Yang ◽  
Mohamed S. El-Genk
Keyword(s):  
Motion Picture ◽  
Flow Regimes ◽  
Mineral Oil ◽  
Numerical Results ◽  
Experimental Investigations ◽  
Experimental Measurements ◽  
Immiscible Liquids ◽  
Regime Map ◽  
Flow Regime Map ◽  
Good Agreement

This work numerically simulates immiscible liquids flow in co-axial microtubes and investigates the effects of changing the injection velocities and physical properties of the liquids and the diameters of the co-axial microtubes on the prevailing flow regimes for forming disperse droplets. These regimes are dripping, transition and jetting. The solution is validated by comparing the present results with those of reported numerical and experimental investigations in all three flow regimes. The generated motion picture movies of the computation domain for up to 18 cycles of forming disperse droplets, help determine not only the breakup mechanisms of the droplets but also the conditions for shifting among the three regimes. A dimensionless correlation is developed based on the present numerical results for predicting the boundary between the transition and the jetting regimes. The correlation is good agreement, to within ±10%, with numerical results and within 20% of the reported experimental measurements for ionized water and PDMS (Polydimethylsiloxane) mineral oil. A flow regime map of the dripping, transition and jetting regimes and of the condition for shifting among them is developed.

Flow around six in-line square cylinders

2012 ◽  
Vol 710 ◽  
pp. 195-233 ◽  
Author(s):  
C. M. Sewatkar ◽  
Rahul Patel ◽  
Atul Sharma ◽  
Amit Agrawal
Keyword(s):  
Reynolds Number ◽  
Flow Regime ◽  
Lift Coefficient ◽  
Flow Regimes ◽  
Reynolds Numbers ◽  
Bluff Bodies ◽  
Square Cylinders ◽  
Chaotic Nature ◽  
Regime Map ◽  
Flow Regime Map

AbstractThe flow around six in-line square cylinders has been studied numerically and experimentally for $0. 5\leq s/ d\leq 10. 0$ and $80\leq \mathit{Re}\leq 320$, where $s$ is the surface-to-surface distance between two cylinders, $d$ is the size of the cylinder and $\mathit{Re}$ is the Reynolds number. The effect of spacing on the flow regimes is initially studied numerically at $\mathit{Re}= 100$ for which a synchronous flow regime is observed for $0. 5\leq s/ d\leq 1. 1$, while quasi-periodic-I, quasi-periodic-II and chaotic regimes occur between $1. 2\leq s/ d\leq 1. 3$, $1. 4\leq s/ d\leq 5. 0$ and $6. 0\leq s/ d\leq 10. 0$, respectively. These regimes have been confirmed via particle-image-velocimetry-based experiments. A flow regime map is proposed as a function of spacing and Reynolds number. The flow is predominantly quasi-periodic-II or chaotic at higher Reynolds numbers. The quasi-periodic and chaotic nature of the flow is due to the wake interference effect of the upstream cylinders which becomes more severe at higher Reynolds numbers. The appearance of flow regimes is opposite to that for a row of cylinders. The Strouhal number for vortex shedding is the same for all the cylinders, especially for synchronous and quasi-periodic-I flow regimes. The mean drag (${C}_{Dmean} $) experienced by the cylinders is less than that for an isolated cylinder, irrespective of the spacing. The first cylinder is relatively insensitive to the presence of downstream cylinders and the ${C}_{Dmean} $ is almost constant at 1.2. The ${C}_{Dmean} $ for the second and third cylinders may be negative, with the value of ${C}_{Dmean} $ increasing monotonically with spacing. The changes in root mean square lift coefficient are consistent with changes in ${C}_{Dmean} $. Interestingly, the instantaneous lift force can be larger than the instantaneous drag force on the cylinders. These results should help improve understanding of flow around multiple bluff bodies.

Flow regimes in circulating fluidized beds

1993 ◽  
Vol 16 (5) ◽  
pp. 307-313 ◽  
Author(s):  
Dingrong Bai ◽  
Yong Jin ◽  
Zhiqing Yu
Keyword(s):  
Fluidized Beds ◽  
Flow Regimes ◽  
Circulating Fluidized Beds

Modeling Approaches to Accurately Predict Minimum Fluidization Characteristics of Gas-Solid Fluidized Beds

2012 ◽  
Author(s):  
Santhip Krishnan Kanholy ◽  
Francine Battaglia
Keyword(s):  
Binary Mixtures ◽  
Fluidized Beds ◽  
Solid Phase ◽  
Cfd Modeling ◽  
Particle Interactions ◽  
Dead Zones ◽  
Modeling Approaches ◽  
Minimum Fluidization ◽  
Computational Fluid Dynamics Cfd ◽  
Eulerian Modeling

The hydrodynamics of fluidized beds involving gas and particle interactions are very complex and must be carefully considered when using computational fluid dynamics (CFD). Modeling particle interactions are even more challenging for binary mixtures composed of varying particle characteristics such as diameter or density. One issue is the presence of dead-zones, regions of particles that do not fluidize and accumulate at the bottom, affecting uniform fluidization. In Eulerian-Eulerian modeling, the solid phase is assumed to behave like a fluid and the presence of dead zones are not typically captured in a simulation. Instead, the entire bed mass present in an experiment is modeled, which assumes full fluidization. The paper will present modeling approaches that account for only the fluidizing mass by adjusting the initial mass present in the bed using pressure drop and minimum fluidization velocity from experiments. In order to demonstrate the fidelity of the new modeling approach, different bed materials are examined. Binary mixture models are also validated for two types of mixtures consisting of glass-ceramic and ceramic-ceramic compositions. It will be shown that adjusting the mass in the modeling of fluidized beds best represents the measured quantities of an experiment for both single-phase and binary mixtures.

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