Porous Media Approach of a CFD Code to Analyze Thermal Hydraulics of PWR Components

2014 ◽  
Author(s):  
Ik Kyu Park ◽  
Seung Jun Lee ◽  
Soo Hyoung Kim ◽  
Hyungrae Kim ◽  
Jae Ryong Lee ◽  
...  
Keyword(s):  
Porous Media ◽  
Numerical Model ◽  
Fluid Model ◽  
Constitutive Relations ◽  
Numerical Procedure ◽  
Component Analysis ◽  
Thermal Hydraulics ◽  
Two Fluid Model ◽  
Validation Calculation ◽  
Two Fluid

This paper presents a set of numerical procedure to innovate CFD code into a PWR component analysis code. A porous media approach is adapted to two-fluid model and conductor model, and a pack of constitutive relations close the numerical model into a PWR component analysis code. The separate verification calculations on conductor model and porous media approach, and the validation calculation for the integrated component-scale code are introduced.

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.

Assessment of Components of the Subcooled Boiling Model for CFD Simulations

2010 ◽  
Author(s):  
Deoras Prabhudharwadkar ◽  
Martin A. Lopez de Bertodano ◽  
John Buchanan ◽  
Avinash Vaidheeswaran
Keyword(s):  
Fluid Model ◽  
Constitutive Relations ◽  
Bubble Diameter ◽  
Density Ratio ◽  
Data Sets ◽  
Vapor Generation ◽  
Wide Range ◽  
Two Fluid Model ◽  
Bubble Sizes ◽  
Two Fluid

This paper describes the details of validation of heat and mass transfer models used for subcooled boiling simulation with a CFD two-fluid model. This research was focused on assessment of the wall heat flux partitioning model using the state-of-the-art multidimensional experimental data available in the literature. Various constitutive relations used to close the vapor generation rate at the heated wall were studied and the best suited combination of these was obtained. The current study was restricted to vertical flows through pipe and annulus geometries. Three data sets from the literature were considered: first with R12 at about 26 bar pressure, second with water at atmospheric pressure and third with R113 at 2.69 bar pressure. In these data sets, the bubble diameter distribution across the ducts was measured. Bubble diameter estimation brings in the largest uncertainty in the two-fluid model predictions and hence using the data with known bubble sizes allowed to focus on assessment of other parameters which use constitutive relations to model vapor generation rate, e.g. bubble nucleation site density and bubble departure frequency at the wall. The simulations were carried out using the CFD code CFX-12. The R12 data used here corresponds to fluid-vapor density ratio which is equivalent to that of water-steam at 150 bar. Therefore the density ratio varies over two orders of magnitude. The surface tension also varies over a wide range from 0.0017 to 0.057 N/m. The ratio of the flow channel hydraulic diameter to the bubble diameter in these simulations varied between 4 and 40. The two-fluid model was modified, for cases involving bubble sizes too large to be represented using the continuum assumption, in order to obtain satisfactory results. Hence, the model that has been developed for this study is applicable for a wide range of physical conditions and bubble sizes.

TWO PHASE MIXTURE FILTRATION

2010 ◽  
Vol 13 (4) ◽  
pp. 5-17
Author(s):  
I. Antonov ◽  
A. Terziev ◽  
S. Antonov ◽  
Nam Thanh Nguyen ◽  
Lien Duc Hoang
Keyword(s):  
Mathematical Model ◽  
Porous Media ◽  
Fluid Model ◽  
Longitudinal Direction ◽  
Phase Flow ◽  
Two Phase ◽  
Phase Mixture ◽  
Two Fluid Model ◽  
The Mathematical Model ◽  
Two Fluid

This study describes new theory about filtrating of two-phase mixture passing through porous media. As a base of the two-fluid model of the two-phase flow and accepting the porous material as a media with increased resistance. The mathematical model is numerically solved using the appropriate descretization method. Some preliminary results from the numerical solution are presented – gas and admixture velocities distribution in longitudinal direction as a function of filtrating layer thickness.

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