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.

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

2008 ◽  
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 inter-subchannel fluid transfer, have been investigated experimentally and analytically. In the experiments, data on flow and void redistributions were obtained for hydraulically non-equilibrium 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 the test liquids. In addition, data on the void diffusion coefficient, D˜, 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 the model to account for the reduced surface tension effects.

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.

Measurement and Analysis of Void Fraction in a Multiple-Channel Simplifying Triangle Tight Lattice Rod Bundle

2006 ◽  
Author(s):  
Michio Sadatomi ◽  
Akimaro Kawahara ◽  
Hiroyuki Kudo ◽  
Hiroshi Shirai
Keyword(s):  
Surface Tension ◽  
Friction Force ◽  
Void Fraction ◽  
Wall Friction ◽  
Interfacial Friction ◽  
Multiple Channel ◽  
Rod Bundle ◽  
Annular Flows ◽  
Tight Lattice ◽  
Reduced Surface

In order to know the effects of reduced surface tension on void fraction, adiabatic experiments were conducted for both air-water and air-water with surfactant systems at room temperature and pressure. Void fraction data were obtained for bubbly, slug, churn and annular flows in a vertical channel with two subchannels simplifying a triangle tight lattice rod bundle. The void fraction was found to be lower in air-water system than air-water with surfactant one. In addition, the void fractions for both systems were found to be lower than those calculated by various correlations in literatures for circular pipe flow. In order to study the cause of the above data trend, for annular flows as a first step, the void fraction has been calculated by a subchannel analysis using wall and interfacial friction correlations in literatures as constitutive equations, and by assuming the liquid film to be uniform over the wall perimeter. The best agreement between the calculation and the experiment has been obtained when NASCA correlation for wall friction force and modified RELAP5/MOD2 correlation incorporating reduced surface tension effects for interfacial friction force were used.

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