On the Critical Flows of Pressurized Pipe Systems

2008 ◽  
Author(s):  
Moon-Sun Chung ◽  
Sung-Jae Lee
Keyword(s):  
Prediction Model ◽  
System Analysis ◽  
Flow Model ◽  
Fluid Model ◽  
Benchmark Problems ◽  
Critical Flow ◽  
Quality Prediction ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Pipe Systems

Two-phase critical flows through some breaks of pressurized pipe systems are calculated by an improved critical flow model. These phenomena have many difficulties in predicting the two-phase critical flow rates at the break points mainly due to the inaccuracies of the critical flow model. Further, the case of critical flow through the small bottom break of horizontal pipe, the accuracy of a quality prediction model is also important as well as the critical flow model itself. In this study, an improved critical flow model is introduced which is based on a new sound speed criterion derived from the hyperbolic two-fluid model for non-equilibrium flow and this model is implemented to a system analysis code. Following to the vertically upward flows with quality variation and Marviken tests as benchmark problems, the small bottom break of a pressurized horizontal pipe is calculated and discussed in some details. The assessment results on the critical flow test through a small bottom break in a horizontal pipe show the importance of the accuracy of the critical flow model as well as that of the quality prediction model to reduce the relative errors.

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.

scholarly journals Computational investigation of liquid-solid slurry flow through an expansion in a rectangular duct

2014 ◽  
Vol 62 (3) ◽  
pp. 234-240 ◽  
Author(s):  
Gianandrea Vittorio Messa ◽  
Stefano Malavasi
Keyword(s):  
Volume Fraction ◽  
Particle Density ◽  
Fluid Model ◽  
Solid Volume Fraction ◽  
Solid Particles ◽  
Rectangular Duct ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Two Fluid Model ◽  
Two Fluid

Abstract The flow of a mixture of liquid and solid particles at medium and high volume fraction through an expansion in a rectangular duct is considered. In order to improve the modelling of the phenomenon with respect to a previous investigation (Messa and Malavasi, 2013), use is made of a two-fluid model specifically derived for dense flows that we developed and implemented in the PHOENICS code via user-defined subroutines. Due to the lack of experimental data, the two-fluid model was validated in the horizontal pipe case, reporting good agreement with measurements from different authors for fully-suspended flows. A 3D system is simulated in order to account for the effect of side walls. A wider range of the parameters characterizing the mixture (particle size, particle density, and delivered solid volume fraction) is considered. A parametric analysis is performed to investigate the role played by the key physical mechanisms on the development of the two-phase flow for different compositions of the mixture. The main focuses are the distribution of the particles in the system and the pressure recovery

Development of Sodium Two-Phase Flow Model for KALIMER Core Analysis

2002 ◽  
Author(s):  
W. P. Chang ◽  
Dohee Hahn
Keyword(s):  
Liquid Metal ◽  
Single Phase ◽  
System Analysis ◽  
Flow Model ◽  
Two Phase Flow ◽  
Water System ◽  
Phase Flow ◽  
Two Phase ◽  
Applicable Range ◽  
Further Development

An algorithm for sodium boiling is developed in order to extend the applicability of SSC-K, which is a main system analysis code for the KALIMER (Korea Advanced LIquid MEtal Reactor) conceptual design. As the capability of the current SSC-K version is limited to simulation of only a single-phase sodium flow, its applicable range should not be enough to assess the fuel integrity under some of HCDA (Hypothetical Core Disruptive Accident) initiating events where sodium boiling is anticipated. The two-phase flow model similar to that used for the light water system is known to be no more effective directly to liquid metal reactors, because the phenomena observed between two reactor coolant systems are definitely different. The developing algorithm is based on a multiple-bubble slug ejection model, which allows a finite number of bubbles in a channel at any time. The present work is a continuous effort following the former study to confirm a qualitative acceptance on the model. Since the model has been applied only to the active fuel region in the former study, a part of its qualification seems to have already been demonstrated. For its application to the whole KALIMER core channel, however, the model needs to be examined the applicability to the fuel regions other than the active fuel. The present study primarily focuses on that point. In a result, although the model may be improved in a sense through the present study over the previous modeling, a clear limitation is also confirmed with the validity of the model. The further development, therefore, is required for this model to achieve its goal by resolving such limitations.

Upwind Solutions for Two-Phase Flow Problems Using a Hyperbolic Two-Fluid Model

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

This study discusses on the implementation of an upwind method for a new 2-dimensional 2-fluid model including the surface tension effect in the momentum equations. This model consists of a complete set of 8 equations including 2-mass, 4-momentum, and 2-internal energy conservation equations having all real eigenvalues. Based on this equation system with upwind numerical method, the present authors first make a pilot 2-dimensional 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.

Homogeneous non-equilibrium two-phase critical flow model

1987 ◽  
Vol 10 (1) ◽  
pp. 420-426 ◽  
Author(s):  
Jens Jürgen Schröder ◽  
Nha Vuxuan
Keyword(s):  
Flow Model ◽  
Critical Flow ◽  
Two Phase ◽  
Non Equilibrium

Numerical Investigation of Slug Flow in a Horizontal Pipe Using a Multi-Scale Two-Phase Approach to Incorporate Gas Entrainment Effects

2016 ◽  
Author(s):  
Stefan Wenzel ◽  
Marek Czapp ◽  
Thomas Sattelmayer
Keyword(s):  
Flow Regime ◽  
Slug Flow ◽  
Fluid Model ◽  
Interfacial Area ◽  
Experimental Investigations ◽  
Multiscale Approach ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Horizontal Pipes ◽  
Interface Capturing

Numerical as well as experimental investigations of the highly intermittent slug flow regime of a gas-liquid mixture in horizontal pipes are of particular interest for nuclear reactor safety in post loss-of-coolant accident (LOCA) situations. The strong variation of governing interfacial length scales, as they are characterizing the slug flow regime, pushes common numerical multi-phase approaches to their limits, since they are designed either for interface capturing or for modeling the sub-grid behavior of the dispersed mixture. In this work an enhanced hybrid two-phase flow solver is employed to investigate the global and local characteristics of adiabatic, horizontal slug flows in a water-air system. A dynamic switching algorithm for an interface capturing procedure is introduced to examine segregated and dispersed parts in the same flow domain. The inter-facial area transport equation (IATE) is used to detect dispersed flow regions as well as to determine variable bubble sizes and their distribution within the slug body. Experimental results of videometry measurements on a horizontal, 10 m long pipe with an inner diameter of 54 mm at atmospheric pressure and room temperature are compared with numerical results of the same geometry in terms of global characteristics such as slug frequency and onset position. Local properties, such as the interfacial area density in the slug body, are also examined. This study demonstrates the capability of a coupled multiscale approach based on the Euler-Euler two-fluid model (TFM) for the simulation of slug flow in horizontal pipes with a high amount of entrainment.

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