Numerical Analysis of Two-Phase Pipe Flow of Liquid Helium Using Multi-Fluid Model

2001 ◽  
Vol 123 (4) ◽  
pp. 811-818 ◽  
Author(s):  
Jun Ishimoto ◽  
Mamoru Oike ◽  
Kenjiro Kamijo
Keyword(s):  
Phase Transition ◽  
Gas Phase ◽  
Liquid Helium ◽  
Two Phase Flow ◽  
Fluid Model ◽  
Numerical Results ◽  
Phase Flow ◽  
Two Dimensional ◽  
Two Phase ◽  
Normal Fluid

The two-dimensional characteristics of the vapor-liquid two-phase flow of liquid helium in a pipe are numerically investigated to realize the further development and high performance of new cryogenic engineering applications. First, the governing equations of the two-phase flow of liquid helium based on the unsteady thermal nonequilibrium multi-fluid model are presented and several flow characteristics are numerically calculated, taking into account the effect of superfluidity. Based on the numerical results, the two-dimensional structure of the two-phase flow of liquid helium is shown in detail, and it is also found that the phase transition of the normal fluid to the superfluid and the generation of superfluid counterflow against normal fluid flow are conspicuous in the large gas phase volume fraction region where the liquid to gas phase change actively occurs. Furthermore, it is clarified that the mechanism of the He I to He II phase transition caused by the temperature decrease is due to the deprivation of latent heat for vaporization from the liquid phase. According to these theoretical results, the fundamental characteristics of the cryogenic two-phase flow are predicted. The numerical results obtained should contribute to the realization of advanced cryogenic industrial applications.

A NUMERICAL STUDY OF TWO-PHASE FLOW USING A TWO-DIMENSIONAL TWO-FLUID MODEL

2004 ◽  
Vol 45 (10) ◽  
pp. 1049-1066 ◽  
Author(s):  
Moon-Sun Chung ◽  
Seung-Kyung Pak ◽  
Keun-Shik Chang
Keyword(s):  
Two Phase Flow ◽  
Numerical Study ◽  
Fluid Model ◽  
Phase Flow ◽  
Two Dimensional ◽  
Two Phase ◽  
Two Fluid Model ◽  
Two Fluid

AMADEUS Project and Microscopic Simulation of Boiling Two-Phase Flow by the Lattice-Boltzmann Method

1997 ◽  
Vol 08 (04) ◽  
pp. 843-858 ◽  
Author(s):  
Yasuyoshi Kato ◽  
Koji Kono ◽  
Takeshi Seta ◽  
Daniel Martínez ◽  
Shiyi Chen
Keyword(s):  
Phase Transition ◽  
Gas Phase ◽  
Lattice Boltzmann ◽  
Bubble Dynamics ◽  
Two Phase Flow ◽  
Phase Interface ◽  
Lattice Boltzmann Model ◽  
Phase Flow ◽  
Two Phase ◽  
Boltzmann Model

A two-dimensional lattice-Boltzmann model with a hexagonal lattice is developed to simulate a boiling two-phase flow microscopically. Liquid-gas phase transition and bubble dynamics, including bubble formation, growth and deformation, are modeled by using an interparticle potential based on the van der Waals equation of state. Thermohydrodynamics is incorporated into the model by adding extra velocities to define temperature. The lattice-Boltzmann model is solved by a finite difference scheme so that numerical stability can be ensured at large discontinuity across the liquid-gas phase boundary and the narrow phase interface thickness can be attained. It is shown from numerical simulations that the model has the ability to reproduce phase transition, bubble dynamics and thermohydrodynamics while assuring numerical instability and narrow phase interface.

Influence of the Fin on Two-Dimensional Characteristics of Dispersed Flow With Wall Liquid Film in the Vicinity of Obstacle

2002 ◽  
Author(s):  
Zoran V. Stosic ◽  
Vladimir D. Stevanovic ◽  
Akimi Serizawa
Keyword(s):  
Liquid Film ◽  
Gas Phase ◽  
Two Phase Flow ◽  
Fluid Model ◽  
Film Surface ◽  
Phase Flow ◽  
Atmospheric Conditions ◽  
Two Phase ◽  
Positive Effects ◽  
Rod Bundle

Spacers have positive effects on the heat transfer enhancement and critical heat flux (CHF) increase downstream of their location in the boiling channel. These effects are further increased by the inclusion of the fin on the spacer rear edge. Numerical simulation of a separation in a high void gas phase and dispersed droplets flow around a spacer, with a liquid film flowing on the wall, is performed. Mechanisms leading to the CHF increase due to the two-phase flow separation and liquid film thickening downstream the spacer are demonstrated. Numerical simulations of gas phase, entrained droplets and wall liquid film flows were performed with the three-fluid model and with the application of the high order numerical scheme for the liquid film surface interface tracking. Predicted is a separation of gas and entrained droplets streams around the spacer without and with a fin inclined 30 and 60 degrees to the wall, as well as a change of wall liquid film thickness in the vicinity of spacer. Results of liquid film dynamic behaviour are compared with the recently obtained experimental results. Multi-dimensional characteristics of surface waves on the liquid film were measured with newly developed ultrasonic transmission technique in a 3×3 rod bundle test section with air-water flow under atmospheric conditions. Obtained numerical results are in good agreement with experimental observations. The presented investigation gives insight into the complex mechanisms of separated two-phase flow with wall liquid film around the spacer and support thermal-hydraulic design and optimisation of flow obstacles in various thermal equipments.

A Numerical Modelling of Two-Phase Flow System

2008 ◽  
Author(s):  
Moon-Sun Chung ◽  
Jong-Won Kim
Keyword(s):  
Sound Speed ◽  
Two Phase Flow ◽  
Flow System ◽  
Fluid Model ◽  
Equation System ◽  
Pressure Jump ◽  
Phase Flow ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Two Phase

A two-dimensional two-fluid model for two-phase flow system is proposed. This two-dimensional model is based on the hyperbolic one-dimensional model which is improved in its mathematical property by adopting the interfacial pressure jump terms in the momentum equations. Owing to this surface-tension effect incorporated in the momentum equations, eigenvalues of the equation system can be obtained analytically and they are proved to be all real. The eigenvectors can also be obtained analytically with linearly independent form. Further, they consist of phasic convective velocities, the sound speed of gas phase, and the sound speed of liquid phase. Consequently, the governing equation system is mathematically hyperbolic with reasonable characteristic speeds by which the upwind numerical method avails. Advantages and possibility of the present model are discussed in some detail.

On Treatment of Negative Pressures in Fluid Dynamics

2005 ◽  
Author(s):  
Iztok Tiselj ◽  
Janez Gale
Keyword(s):  
Fluid Dynamics ◽  
Phase Transition ◽  
Two Phase Flow ◽  
Fluid Model ◽  
Saturation Pressure ◽  
Phase Flow ◽  
Two Phase ◽  
Negative Pressures ◽  
Two Fluid Model ◽  
Two Fluid

Rapid depressurization of a cold single-phase liquid leads to the onset of a vaporisation, i.e. the phase transition phenomena. Prior to the start and in the very first moment of the phase transition, pressure in the liquid may briefly drop to negative values, when initial liquid temperature is low enough. Metastable liquid in a state of tension is well known in static experiments, but is less known in the fluid dynamics. The present paper discusses some preliminary findings in the field of modeling of the negative pressures in transient water flows and subsequent phase transition with a single-pressure two-fluid model. A highly simplified single-pressure two-fluid model is used in the present work to describe the two-phase flow with negative liquid and positive vapor pressure. The assumption used at negative liquid pressures is equal temperature of liquid and newly generated vapor phase, while the gas pressure is assumed to be the saturation pressure at that temperature. Rather rough models seem to be sufficiently accurate due to the large uncertainty in the modeling of the single-to-two-phase flow transition, which strongly depends on the density of the nucleation sites in the liquid and at the wall.

On the Characteristics of a Two-Dimensional Two-Fluid Model

2008 ◽  
Author(s):  
Moon-Sun Chung ◽  
Sung-Jae Lee ◽  
Jong-Won Kim
Keyword(s):  
Two Phase Flow ◽  
Flow Problem ◽  
Fluid Model ◽  
Phase Flow ◽  
Two Dimensional ◽  
Two Phase ◽  
One Dimensional ◽  
Pipe System ◽  
Two Fluid Model ◽  
Two Fluid

In this study, we will suggest a two-dimensional two-fluid model considering the effect of mass and momentum interactions to simulate more realistic two-phase flow than the conventional model did. A hyperbolic two-fluid model had been developed for one-dimensional two-phase flow by Chung et al. [1] and it has been improved and applied to analyze one-dimensional two-phase flow problem including surface tension effect for either ordinary pipe system or minichannels. However, in order to simulate the two-dimensional two-phase flow problem efficiently in the future, the above one-dimensional model has need to be extended to two-dimensional equations and adopted to an upwind numerical method.

scholarly journals Natural modes of the two-fluid model of two-phase flow

2021 ◽  
Vol 33 (3) ◽  
pp. 033324
Author(s):  
Alejandro Clausse ◽  
Martín López de Bertodano
Keyword(s):  
Two Phase Flow ◽  
Fluid Model ◽  
Phase Flow ◽  
Two Phase ◽  
Natural Modes ◽  
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.

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