The Effect of Closure Laws on the Simulation Results of Two-Fluid Model of Gas-Solid Flows

2015 ◽  
Author(s):  
Yifei Duan ◽  
Zhi-Gang Feng
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Fluid Model ◽  
Transfer Model ◽  
Hill Model ◽  
Simulation Results ◽  
Two Fluid Model ◽  
Drag Models ◽  
Closure Laws ◽  
Two Fluid

There are two primary approaches in modeling fluid-solid flows based on the method of treating particles suspended in flows. The first approach is the Eulerian-Lagrangian or Discrete Element Method (DEM) approach that tracks individual particles by solving the equations of motion of these particles. The second approach is the Eulerian-Eulerian approach or two-fluid model (TFM) that considers particles as another continuum phase or fluid. The TFM is preferred in modeling and predicting gas-solid flow behaviors in many engineering applications because of its efficiency in handling large-scale complex systems with large number of particles. However, one of the challenges in TFM is the uncertainty related to the selection of closure laws and transport properties of solid phases. In this study we employ the MFIX code, a general-purpose TFM computer code developed at the National Energy Technology Laboratory, to investigate the effect of different drag models and heat transfer models on the simulation results on the flow hydrodynamics and heat transfer of gas-solid fluidized beds. Three drag models (Gidspow model, Syamlal-O’Brien model, and Koch-Hill model) and two heat transfer model (Gunn model and a recently developed model by Sun et al., 2015) are tested. Simulation results from these models are compared with experimental measurements. The accuracy and applicability of these models are assessed and discussed.

Numerical Analysis of Heat Transfer Test of Supercritical Water in a Tube Using the Three-Dimensional Two-Fluid Model Code

2008 ◽  
Author(s):  
Takeharu Misawa ◽  
Hiroyuki Yoshida ◽  
Hidesada Tamai ◽  
Kazuyuki Takase
Keyword(s):  
Heat Transfer ◽  
Fluid Model ◽  
Three Dimensional ◽  
Design Procedure ◽  
Supercritical Pressure ◽  
Thermal Design ◽  
Energy Agency ◽  
Pressure Region ◽  
Two Fluid Model ◽  
Two Fluid

The three-dimensional two-fluid model analysis code ACE-3D is developed in Japan Atomic Energy Agency for the thermal design procedure on two-phase flow thermal-hydraulics of light water-cooled reactors. In order to perform thermal hydraulic analysis of SCWR, ACE-3D is enhanced to supercritical pressure region. As a result, it is confirmed that transient change in subcritical and supercritical pressure region can be simulated smoothly using ACE-3D, that ACE-3D can predict the results of the past heat transfer experiment in the supercritical pressure condition, and that introduction of thermal conductivity effect of the wall restrains fluctuation of wall.

Numerical Simulation of Dense Phase Pneumatic Conveying Gypsum in Stepped Pipeline

2011 ◽  
Vol 306-307 ◽  
pp. 1387-1392
Author(s):  
Wei Xiang Wu ◽  
Zong Ming Liu ◽  
Guang Bin Duan
Keyword(s):  
Static Pressure ◽  
Fluid Model ◽  
Dynamic Pressure ◽  
Phase Flow ◽  
Pneumatic Conveying ◽  
Dense Phase ◽  
Two Phase ◽  
Simulation Results ◽  
Two Fluid Model ◽  
Two Fluid

The process of dense phase pneumatic conveying gypsum in stepped pipeline was simulated by using an Euler-Euler two fluid model of dense gas-particle two phase flow based on the kinetic theory of gas and granular. The simulation results showed dynamic pressure increased while static pressure decreased in the first two tapered pipe, but this trend became opposite in the last diffuser pipe. The gas and particle velocity both increased in the 80-65mm and 65-50mm tapered pipe, but decreased in 50-80mm diffuser pipe. In a short, the results showed that the simulation was consistent with the fact, which proved the feasibility of our simulation.

scholarly journals Hybrid Two-Fluid DEM Simulation of Gas-Solid Fluidized Beds

2006 ◽  
Author(s):  
Jin Sun ◽  
Francine Battaglia ◽  
S. Subramaniam
Keyword(s):  
Momentum Transfer ◽  
Fluidized Beds ◽  
Structural Information ◽  
Fluid Model ◽  
Fluid Phase ◽  
Transfer Model ◽  
Dem Simulation ◽  
Dem Simulations ◽  
Two Fluid Model ◽  
Two Fluid

Simulations of gas-solid fluidized beds have been carried out using a hybrid simulation method, which couples the discrete element method (DEM) for particle dynamics with the ensemble-averaged two-fluid (TF) equations for the fluid phase. The coupling between the two phases is modeled using an interphase momentum transfer term. The results of the hybrid TF-DEM simulations are compared to experimental data and two-fluid model simulations. It is found that the TF-DEM simulation is capable of predicting general fluidized bed dynamics, i.e., pressure drop across the bed and bed expansion, which are in agreement with experimental measurements and two-fluid model predictions. In addition, the TF-DEM model demonstrates the capability to capture more heterogeneous structural information of the fluidized beds than the two-fluid model alone. The microstructures in fluidized beds are analyzed and the implications to kinetic theory for granular flows are discussed. However, the TF-DEM simulations depend on the form of the interphase momentum transfer model, which can be computed in terms of averaged or instantaneous particle quantities. Various forms of the interphase momentum transfer model are examined, and their suitability to the hybrid TF-DEM simulation approach is evaluated.

CFD Analysis on Wall Boiling Model During Subcooled Boiling in Vertical Narrow Rectangular Channel

2018 ◽  
Author(s):  
Tingting Ren ◽  
Changqi Yan ◽  
Meiyue Yan ◽  
Shengzhi Yu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Fluid Model ◽  
Rectangular Channel ◽  
Subcooled Boiling ◽  
Site Density ◽  
Rectangular Channels ◽  
Two Fluid Model ◽  
Nucleate Site ◽  
Two Fluid

Two-fluid model is a common method to simulate the subcooled flow boiling heat transfer, in which the wall boiling model is mainly used for the partition of wall heat flux and the mass transfer between two phases on the wall. The model determines the amount of vapor phase and predicts the cross-sectional void fraction in the channel, nucleate site density and bubble departure diameter play an important role in the accurate prediction of wall boiling model. Eulerian two-fluid model coupled with Rensselaer Polytechnic Institute (RPI) wall boiling model is employed to simulate the heat transfer characteristics and boiling phenomena in vertical narrow rectangular channels by using FLUENT code. Based on the experimental data of subcooled boiling in vertical narrow rectangular channel, different combinations of nucleate site density and bubble departure diameter correlations are used to calculate under different conditions of heat flux and inlet subcooling. Comparing the calculated heat transfer coefficients along the vertical height with experimental results, it can be found that these two parameters have a significant effect on the subcooled boiling heat transfer in narrow rectangular channels. Different parameter combinations lead to differences in wall heat flux distribution, different heat flux and inlet subcooling also have different effects on these models, which eventually lead to different evaporative heat flux, thus affecting the prediction of void fraction.

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