Predictions of Void Fraction in Convective Subcooled Boiling Channels Using a One-Dimensional Two-Fluid Model

1995 ◽  
Vol 117 (3) ◽  
pp. 799-803 ◽  
Author(s):  
Lin-Wen Hu ◽  
Chin Pan
Keyword(s):  
Void Fraction ◽  
Fluid Model ◽  
Subcooled Boiling ◽  
One Dimensional ◽  
Two Fluid Model ◽  
Two Fluid

Proposed Use of the One-Dimensional Two-Fluid Model With Momentum Flux Parameters

2000 ◽  
Author(s):  
Jin Ho Song ◽  
H. D. Kim
Keyword(s):  
Differential Equations ◽  
Void Fraction ◽  
Momentum Flux ◽  
Fluid Model ◽  
Sufficient Conditions ◽  
Wave Number ◽  
One Dimensional ◽  
Two Fluid Model ◽  
The One ◽  
Two Fluid

Abstract The dynamic character of a system of the governing differential equations for the one-dimensional two-fluid model, where the appropriate momentum flux parameters are employed to consider the velocity and void fraction distribution in a flow channel, is analyzed. In response to a perturbation in the form of a traveling wave, a linear stability analysis is performed for the governing differential equations. The analytical expression for the growth factor as a function of wave number, void fraction, drag coefficient, and relative velocity is derived. It provides the necessary and sufficient conditions for the stability of the one-dimensional two-fluid model in terms of momentum flux parameters. It is analytically shown that the one-dimensional two-fluid model is mathematically well posed by use of appropriate momentum flux parameters, while the conventional two-fluid model makes the system unconditionally unstable. It is suggested that the velocity and void distributions should be properly accounted for in the one-dimensional two-fluid model by use of momentum flux parameters.

Development of one-dimensional two-fluid model with consideration of void fraction covariance effect

2018 ◽  
Vol 55 (7) ◽  
pp. 720-732 ◽  
Author(s):  
Tetsuhiro Ozaki ◽  
Takashi Hibiki ◽  
Shuichiro Miwa ◽  
Michitsugu Mori
Keyword(s):  
Void Fraction ◽  
Fluid Model ◽  
One Dimensional ◽  
Two Fluid Model ◽  
Two Fluid

A Physically Based, One-Dimensional Two-Fluid Model for Direct Contact Condensation of Steam Jets Submerged in Subcooled Water

2015 ◽  
Vol 1 (2) ◽  
Author(s):  
David Heinze ◽  
Thomas Schulenberg ◽  
Lars Behnke
Keyword(s):  
Direct Contact ◽  
Two Phase Flow ◽  
Fluid Model ◽  
Interfacial Area ◽  
Phase Flow ◽  
Two Phase ◽  
One Dimensional ◽  
Two Fluid Model ◽  
Contact Condensation ◽  
Two Fluid

A simulation model for the direct contact condensation of steam in subcooled water is presented that allows determination of major parameters of the process, such as the jet penetration length. Entrainment of water by the steam jet is modeled based on the Kelvin–Helmholtz and Rayleigh–Taylor instability theories. Primary atomization due to acceleration of interfacial waves and secondary atomization due to aerodynamic forces account for the initial size of entrained droplets. The resulting steam-water two-phase flow is simulated based on a one-dimensional two-fluid model. An interfacial area transport equation is used to track changes of the interfacial area density due to droplet entrainment and steam condensation. Interfacial heat and mass transfer rates during condensation are calculated using the two-resistance model. The resulting two-phase flow equations constitute a system of ordinary differential equations, which is solved by means of the explicit Runge–Kutta–Fehlberg algorithm. The simulation results are in good qualitative agreement with published experimental data over a wide range of pool temperatures and mass flow rates.

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.

Prediction of Parameters Distribution of Upward Boiling Two-Phase Flow With Two-Fluid Models

2002 ◽  
Author(s):  
Wei Yao ◽  
Christophe Morel
Keyword(s):  
Void Fraction ◽  
Fluid Model ◽  
Constitutive Relations ◽  
Turbulent Dispersion ◽  
Dispersion Force ◽  
Liquid Temperature ◽  
Two Phase ◽  
Radial Profiles ◽  
Two Fluid Model ◽  
Two Fluid

In this paper, a multidimensional two-fluid model with additional turbulence k–ε equations is used to predict the two-phase parameters distribution in freon R12 boiling flow. The 3D module of the CATHARE code is used for numerical calculation. The DEBORA experiment has been chosen to evaluate our models. The radial profiles of the outlet parameters were measured by means of an optical probe. The comparison of the radial profiles of void fraction, liquid temperature, gas velocity and volumetric interfacial area at the end of the heated section shows that the multidimensional two-fluid model with proper constitutive relations can yield reasonably predicted results in boiling conditions. Sensitivity tests show that the turbulent dispersion force, which involves the void fraction gradient, plays an important role in determining the void fraction distribution; and the turbulence eddy viscosity is a significant factor to influence the liquid temperature distribution.

scholarly journals Dissipation of turbulence by magnetohydrodynamic shock waves

2015 ◽  
Vol 11 (S315) ◽  
Author(s):  
Andrew Lehmann ◽  
Mark Wardle
Keyword(s):  
Shock Front ◽  
Fluid Model ◽  
Neutral Species ◽  
One Dimensional ◽  
Neutral Gas ◽  
Gas Dynamic ◽  
Magnetohydrodynamic Shock ◽  
Two Fluid Model ◽  
Ion Species ◽  
Two Fluid

AbstractWe characterise steady, one-dimensional fast and slow magnetohydrodynamic (MHD) shocks using a two-fluid model. Fast MHD shocks are magnetically driven, forcing ions to stream through the neutral gas ahead of the shock front. This magnetic precursor heats the gas sufficiently to create a large, warm transition zone where all fluid variables only weakly change in the shock front. In contrast, slow MHD shocks are driven by gas pressure where neutral species collide with ion species in a thin hot slab that closely resembles an ordinary gas dynamic shock.We computed observational diagnostics for fast and slow shocks at velocities vs=2–4 km/s and preshock Hydrogen nuclei densities nH = 102-4 cm−3. We followed the abundances of molecules relevant for a simple oxygen chemistry and include cooling by CO, H2 and H2O. Estimates of intensities of 12CO rotational lines show that high-J lines, above J = 6 → 5, are more strongly excited in slow MHD shocks.

An Upwind Numerical Method for a Hyperbolic One-Dimensional Two-Fluid Model

2011 ◽  
Author(s):  
Youn-Gyu Jung ◽  
Moon-Sun Chung ◽  
Sung-Jae Yi
Keyword(s):  
Numerical Method ◽  
Fluid Model ◽  
Equation System ◽  
Benchmark Problems ◽  
Two Phase ◽  
One Dimensional ◽  
Flow Problems ◽  
Complete Set ◽  
Two Fluid Model ◽  
Two Fluid

This study discusses on the implementation of an upwind method for a one-dimensional two-fluid model including the surface tension effect in the momentum equations. This model consists of a complete set of six equations including two-mass, two-momentum, and two-internal energy conservation equations having all real eigenvalues. Based on this equation system with upwind numerical method, the present authors first make a pilot code and then solve some benchmark problems to verify whether this model and numerical method is able to properly solve some fundamental one-dimensional two-phase flow problems or not.

Discussion on the pressure drop calculation for oil‐water separated flow using a one dimensional two‐fluid model

2019 ◽  
Vol 97 (12) ◽  
pp. 3156-3174
Author(s):  
Nannan Liu ◽  
Wei Wang ◽  
Yingying Liu ◽  
Liang Ma ◽  
Jing Gong
Keyword(s):  
Pressure Drop ◽  
Fluid Model ◽  
Separated Flow ◽  
One Dimensional ◽  
Oil Water ◽  
Two Fluid Model ◽  
Two Fluid
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