scholarly journals CFD Modeling of Boiling Flow in PSBT 5×5 Bundle

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Simon Lo ◽  
Joseph Osman
Keyword(s):  
Fluid Model ◽  
Three Dimensional ◽  
Cfd Modeling ◽  
Computational Grids ◽  
Two Phase ◽  
Spacer Grids ◽  
Void Fractions ◽  
Rod Bundle ◽  
Two Fluid Model ◽  
Cfd Method

Three-dimensional computational fluid dynamics (CFD) method was used to model the boiling two-phase flow in one of the PSBT 5-by-5 rod bundle tests. The rod bundle with all the spacers was modeled explicitly using unstructured computational grids. The six-equation, two-fluid model with the wall boiling model was used to model the boiling two-phase flows in the bundle. The computed void fractions compare well with the measured data at the measuring plane. In addition to the averaged void data, the CFD results give a very detailed picture of the flow and void distributions in the bundle and how they are affected by solid structures in the flow paths such as the spacer grids and mixing vanes.

Numerical Simulation of Boiling Two-Phase Flow in Tight-Lattice Rod Bundle by 3-Dimensional Two-Fluid Model Code ACE-3D

2008 ◽  
Author(s):  
Hiroyuki Yoshida ◽  
Takeharu Misawa ◽  
Kazuyuki Takase
Keyword(s):  
Void Fraction ◽  
Lift Force ◽  
Fluid Model ◽  
Phase Flow ◽  
Two Phase ◽  
Rod Bundle ◽  
Fraction Distribution ◽  
Two Fluid Model ◽  
Tight Lattice ◽  
Two Fluid

Two-fluid model can simulate two phase flow less computational cost than inter-face tracking method and particle interaction method. Therefore, two-fluid model is useful for thermal hydraulic analysis in large-scale domain such as a rod bundle. Japan Atomic Energy Agency (JAEA) develops three dimensional two-fluid model analysis code ACE-3D, which adopts boundary fitted coordinate system in order to simulate complex shape channel flow. In this paper, boiling two-phase flow analysis in a tight lattice rod bundle is performed by ACE-3D code. The parallel computation using 126CPUs is applied to this analysis. In the results, the void fraction, which distributes in outermost region of rod bundle, is lower than that in center region of rod bundle. At height z = 0.5 m, void fraction in the gap region is higher in comparison with that in center region of the subchannel. However, at height of z = 1.1m, higher void fraction distribution exists in center region of the subchannel in comparison with the gap region. The tendency of void fraction to concentrate in the gap region at vicinity of boiling starting point, and to move into subchannel as water goes through rod bundle, is qualitatively agreement with the measurement results by neutron radiography. To evaluate effects of two-phase flow model used in ACE-3D code, numerical simulation of boiling two-phase in tight lattice rod bundle with no lift force model (neglecting lift force acting on bubbles) is also performed. From the comparison of numerical results, it is concluded that the effects of lift force model are not so large on overall void fraction distribution in tight lattice rod bundle. However, higher void fraction distribution in center region of the subchannel was not observed in this simulation. It is concluded that the lift force model is important for local void fraction distribution in rod bundles.

Simplification of Ensemble Averaged Two-Phase Flow with Heat and Mass Transfer Equations for Boiling in a Channel

2008 ◽  
Vol 273-276 ◽  
pp. 616-621
Author(s):  
Hikmet Ş. Aybar ◽  
Mohsen Sharifpur
Keyword(s):  
Two Phase Flow ◽  
Fluid Model ◽  
Three Dimensional ◽  
Phase Flow ◽  
Governing Equations ◽  
Ensemble Averaging ◽  
Two Phase ◽  
Transfer Equations ◽  
Two Fluid Model ◽  
Two Fluid

Generation of vapor and predication of its behavior is an important problem in many industries. In this study, the three dimensional governing equations for turbulence two-phase flow are derived using ensemble averaging two fluid model. The governing equations are simplified by a heuristic approach based on boiling data, and the equations are used to obtain the parameters for each phase along the channel. A computer program is written for the simplified one-dimensional equations, and the results are compared with experimental data.

Two-Phase Flow Pressure Drop in Right Angle Bends

2000 ◽  
Vol 122 (4) ◽  
pp. 761-768 ◽  
Author(s):  
Edward Graf ◽  
Sudhakar Neti
Keyword(s):  
Pressure Drop ◽  
Flow Boiling ◽  
Fluid Model ◽  
Bubbly Flow ◽  
Centrifugal Forces ◽  
Two Phase ◽  
Void Fractions ◽  
Aspect Ratios ◽  
Numerical Predictions ◽  
Two Fluid Model

Gas-liquid two-phase bubbly flows in right angle bends have been studied. Numerical predictions of the flow in right angle bends are made from first principles using an Eulerian-Eulerian two-fluid model. The flow geometry includes a sufficiently long inlet duct section to assure fully developed flow conditions into the bend. The strong flow stratification encountered in these flows warrant the use of Eulerian-Eulerian description of the flow, and may have implications for flow boiling in U-bends. The computational model includes the finer details associated with turbulence behavior and a robust void fraction algorithm necessary for the prediction of such a flow. The flow in the bend is strongly affected by the centrifugal forces, and results in large void fractions at the inner part of the bend. Numerical predictions of pressure drop for the flow with different bend radii and duct aspect ratios are presented, and are in general agreement with data in the literature. Measurements of pressure drop for an air-water bubbly flow in a bend with a nondimensional bend radius of 5.5 have also been performed, and these pressure drop measurements also substantiate the computations described above. In addition to the global pressure drop for the bend, the pressure variations across the cross section of the duct that give rise to the fluid migration (due to centrifugal forces), and stratification of the phases are interesting in their own right. [S0098-2202(00)01004-X]

Analysis of Two-Phase Cavitating Flow with Two-Fluid Model Using Integrated Boltzmann Equations

2013 ◽  
Vol 5 (05) ◽  
pp. 607-638 ◽  
Author(s):  
Shuhong Liu ◽  
Yulin Wu ◽  
Yu Xu ◽  
Hua-Shu Dou
Keyword(s):  
Turbulence Model ◽  
Two Phase Flow ◽  
Fluid Model ◽  
Three Dimensional ◽  
Cavitating Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Pump Sump ◽  
Two Fluid Model ◽  
Two Fluid

AbstractIn the present work, both computational and experimental methods are employed to study the two-phase flow occurring in a model pump sump. The two-fluid model of the two-phase flow has been applied to the simulation of the three-dimensional cavitating flow. The governing equations of the two-phase cavitating flow are derived from the kinetic theory based on the Boltzmann equation. The isotropic RNGk — ε — kcaturbulence model of two-phase flows in the form of cavity number instead of the form of cavity phase volume fraction is developed. The RNGk—ε—kcaturbulence model, that is the RNGk — eturbulence model for the liquid phase combined with thekcamodel for the cavity phase, is employed to close the governing turbulent equations of the two-phase flow. The computation of the cavitating flow through a model pump sump has been carried out with this model in three-dimensional spaces. The calculated results have been compared with the data of the PIV experiment. Good qualitative agreement has been achieved which exhibits the reliability of the numerical simulation model.

Effects of Surface Tension on Two-Phase Void Drift Between Triangle Tight Lattice Subchannels

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Akimaro Kawahara ◽  
Michio Sadatomi ◽  
Tatsuya Higuchi
Keyword(s):  
Surface Tension ◽  
Fluid Model ◽  
Two Phase ◽  
Multiple Channel ◽  
Drift Model ◽  
Rod Bundle ◽  
Two Fluid Model ◽  
Fluid Transfer ◽  
Tight Lattice ◽  
Reduced Surface

In this study, void drift phenomena, which are one of three components of the intersubchannel fluid transfer, have been investigated experimentally and analytically. In the experiments, data on flow and void redistributions were obtained for hydraulically nonequilibrium flows in a multiple channel consisting of two subchannels simplifying a triangle tight lattice rod bundle. In order to know the effects of the reduced surface tension on the void drift, water and water with a surfactant were used as test liquids. In addition, data on the void diffusion coefficient, D̃, needed in a void drift model, have been obtained from the redistribution data. In the analysis, the flow and the void redistributions were predicted by a subchannel analysis code based on a one-dimensional two-fluid model. From a comparison between the experiment and the code prediction, the present analysis code was found to be valid against the present data if newly developed constitutive equations of wall and interfacial friction were incorporated in to the model to account for the reduced surface tension effects.

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