Begell House Inc.
Multiphase Science and Technology
MST
0276-1459
23
1
2011
ANALYSIS OF THE UMSICHTWATER HAMMER BENCHMARK EXPERIMENT 329 USING TRACE AND RELAP5
1-27
10.1615/MultScienTechn.v23.i1.10
W.
Barten
Paul Scherrer Institut; and 2Swiss Federal Nuclear Safety Inspectorate ENSI, Deterministic Safety Analyses DESA, Brugg Switzerland
Audrius
Jasiulevicius
Paul Scherrer Institut, 5232 Villigen PSI, Switzerland; and Vattenfall Nuclear Fuel AB, 16287 Stockholm, Sweden
O.
Zerkak
Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
R.
Macian-Juan
Paul Scherrer Institut, 5232 Villigen PSI, Switzerland; and Department of Nuclear Engineering, TU Munchen, Boltzmannstrasse 15, D-85748 Garching, Germany
two-phase flow
water hammer
cavitation
condensation
system codes
RELAP5
TRACE
In this paper, we assess the capabilities of the TRACE and RELAP5 codes to model coupled two-phase flow and pressure wave propagations in a piping system, since these codes are two of the most widely used tools to model complex system transients of nuclear facilities. With that aim, using the thermal-hydraulic capabilities of both codes in a spatially 1D approximation, the first few seconds after valve closure in the UMSICHT PPP water hammer experiment 329 have been analyzed considering the time-dependent interconnected behavior of pressure, void fraction, and flow rate at different positions in the pipe. With standard code parameters, the overall flow behavior in the first few seconds and the timing of the pressure excursions, as well as the first generation of void downstream of the valve, are well represented by both codes. The measured collapse of void at the first pressure excursion is underpredicted by both codes, and the predicted pressure excursion is thereby dispersed and damped. While the timing of the second pressure excursion is well predicted by both codes, the experimental damping, presumably being at least partly due to fluid-structure interaction (FSI), is not sufficiently reflected in the modeling results. With scoping calculations using TRACE and applying considerably increased condensation heat transfer rate, the calculated collapse of void with increasing pressure due to the reflection of flow at the valve is much more efficient. The timing, shape, and amplitude of the predicted first pressure excursion is in near-perfect agreement with the measured results, including the spiky shape, while the effects of local void generation and distribution still need improvements. The damping of the second pressure peak, being influenced by FSI with vibrations of the pipe structure, is still underestimated. On the whole, this study demonstrates that the best-estimate system codes TRACE and RELAP5 are potentially useful tools for the analysis of a cavitation water hammer in a pipe, and shows how far the models can calculate measured behavior. In order to use these codes for more accurate prediction of cavitation water hammer behavior, further development work is needed in order to better represent the dynamics of direct-contact condensation and flashing in the considered parameter range and, when needed, FSI.
VISUALIZATION AND AXIAL VIEWING TECHNIQUES
29-55
10.1615/MultScienTechn.v23.i1.20
N.
Lecoeur
Department of Chemical Engineering, Imperial College London, Prince Consort Road, London SW7 2BY, United Kingdom
Y. J.
Zeng
Department of Chemical Engineering, Imperial College London, London SW7 2BY, UK
Colin P.
Hale
Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK
Geoffrey F.
Hewitt
Department of Chemical Engineering & Chemical Technology, Imperial College of Science, Technology & Medicine, Prince Consort Road, London SW7 2B Y, England, UK
axial view technique
axial images
visualisation
two-phase flow
droplet entrainment
Axial viewing techniques are advanced photographic methods that have been widely used to visualize two-phase flow systems. A review of the axial viewing techniques is presented, describing the development of axial view systems from their origin to diverse variants of the original device such as the parallel-light technique, the in-line axial viewer used on the Imperial College high pressure multiphase flow rig, and the high-temperature axial viewing system. With these techniques, it has been possible to visualize in detail the various flows and to identify previously unknown mechanisms. These techniques show great continuing potential in elucidating two-phase flow phenomena.
TWO-PHASEWATER HAMMER SIMULATION WITH THE CATHARE CODE
57-75
10.1615/MultScienTechn.v23.i1.30
P.
Nika
ENSMA, Training Course for the Engineer Diploma, 86961 Futuroscope Chasseneuil Cedex France
G.
Serre
CEA Grenoble DEN/DER/SSTH/LMDL, 17 rue des martyrs, 38054 Grenoble Cedex 9, France
water hammer
CATHARE
The 1D module of the CATHARE code has been used to perform calculations of two water hammer tests in which phase change is of great importance. Several sensitivity studies on the meshing, the time step, the flashing, and the condensation model constants have been performed for both tests. A model specific to wall elasticity has been added since it affects the speed of sound. All these works result in a good prediction of the pressure and void fraction fields until the occurrence of the largest pressure peak, which is the most important for pipe design.
THE DISTRIBUTION PARAMETER C0 IN THE DRIFT FLUX MODELING OF FORCED CONVECTIVE BOILING
77-100
10.1615/MultScienTechn.v23.i1.40
Fabrice
Francois
Commissariat à l'Energie Atomique, DTN/SE2T, 38054 Grenoble Cedex 9, France
Jean-Marc
Delhaye
Department of Mechanical Engineering, Clemson University, Clemson, SC, USA
Philippe
Clement
Commissariat à l'Energie Atomique, DEN/DNT/SE2T, Grenoble, France
drift-flux
distribution parameter
forced convective boiling
subcooled boiling
saturated boiling
Forced convective boiling is of great interest for several applications in the power and process
industry, particularly in nuclear plants. Depending on the type of pressurized water reactors,
boiling may be encountered in the cooling channels during startup, nominal, incidental or accidental
conditions with void fractions as large as 0.90. The objective of the present study is to characterize
the two-phase flow patterns under such thermal hydraulic conditions. Using experimental data sets
obtained on a Refrigerant 12 (R12) loop at CEA/Grenoble, we have shown that at high void fractions
the flow behaves like a bubble emulsion; i.e., the liquid phase remains the continuous phase whatever
the void fraction. On the basis of this conclusion, we propose a new model for the distribution
parameter, C0, of the drift-flux model. This model is first qualified on subcooled, low void fraction R12
experimental data in a circular tube. The model is then shown to give results in good agreement with
high void fraction saturated R12 data in a circular tube as well as with experimental data obtained
for water saturated boiling at pressures greater than 10 MPa in narrow rectangular channels.