For boiling water reactors (BWR) and steam generators, the water level is a safety-relevant process variable. The most commonly applied measuring method is based on the calculation of the liquid level from geodetic pressure differences to a reference column of defined height and density. However, transition processes occurring under operational and accident conditions may lead to dynamic changes in the reference level and, therefore, to fluctuations in the differential pressure signal. This paper presents experiments and numerical simulations on the steady-state and transient behavior of gas/liquid phase boundaries in “zero chamber level vessels” (ZCLV). In these slightly inclined miniature tubes, the constant reference level is provided by surface tension forces and the capillary effect, respectively. To investigate the basic topology of gas/liquid interfaces under simplified conditions (environmental parameters, no heat transfer), a test facility with optical access was developed. The construction allows for variations of the inner tube diameter, inclination angle, and liquid mass flow rate, respectively. By this means, experiments on phase boundaries were carried out for ethanol/air and water/air. The results provide information about the impact of geometry parameters and their interactions on the interface topology. In addition, the dynamic draining of excess liquid mass at the free end of the tube and at artificial weld seams, which is supposed to be the reason for temperature fluctuations observed in ZCLV during power operation of BWR, was experimentally analyzed. The measurements represent the basis for an experimental validation and optimizations of the numerical flow code ANSYS CFX 12.0. In the next step, water/vapor phase boundaries at 286 °C and 70 bars will be investigated by applying X-ray radiography to a scale model. The results will be discussed in context with the hydrostatic level measurement in BWR.

References

References
1.
Dziubek
,
A.
,
2007
, “
Condensation in an Inclined Tube With Small Diameter. Modeling, Analysis and Numerical Simulation of a Moving Boundary Problem With Phase Change and Surface Tension
,” Ph.D. thesis, Technische Universität Berlin, Berlin, Germany.
2.
Ghiaasiaan
,
M.
,
2008
, “
Two-Phase Flow, Boiling and Condensation in Conventional and Miniature Systems
,”
1st ed.
,
Cambridge University Press
,
New York
.
3.
Pantzali
,
M. N.
,
Mouza
,
A. A.
, and
Paras
,
S. V.
,
2007
, “
Study of Hydrodynamic Characteristics of the Liquid Layer During Counter-Current Flow in Inclined Small Diameter Tubes: The Effect of Liquid Properties
,”
Proceedings of the 6th International Conference on Multiphase Flow (ICMF 2007)
,
Leipzig, Germany, July 9–13
.
4.
Schulz
,
S.
, and
Hampel
,
R.
,
2011
, “
The Influence of Material Properties and Geometrical Parameters on the Topology of Gas-Liquid Interfaces in Inclined Tubes of Small Diameter—Experiments and Simulation
,”
Proceedings of ICONE 19
,
Makuhari, Japan, October 24–25
.
5.
Xue
,
H. T.
,
Fang
,
Z. N.
,
Yang
,
Y.
,
Huang
,
J. P.
, and
Zhou
,
L. W.
,
2006
, “
Contact Angle Determined by Spontaneous Dynamic Capillary Rises With Hydrostatic Effects: Experiment and Theory
,”
Chem. Phys. Lett.
,
432
, pp.
326
330
.10.1016/j.cplett.2006.10.017
6.
Ansys, Inc.
,
2009
, “
CFX-Solver Modeling Guide
,”
Ansys, Inc.
,
Canonsburg, PA
, pp.
146
147
.
7.
Brackbill
,
J. U.
,
Kothe
,
D. B.
, and
Zemach
,
C.
,
1992
, “
A Continuum Method for Modeling Surface Tension
,”
J. Comput. Phys.
,
100
, pp.
335
354
.10.1016/0021-9991(92)90240-Y
8.
Özkan
,
F.
,
Hecht
,
K.
,
Pfeifer
,
P.
,
Schubert
,
K.
, and
Kraushaar-Czarnetzki
,
B.
,
2010
, “
Influence of the Contact Angle on Two-Phase Flow in Microreactors for Nitrobenzene–Hydrogen–Stainless Steel/Carbon
,”
Surf. Interface Anal.
,
42
, pp.
1122
1127
.10.1002/sia.3386
9.
Stange
,
M.
,
2004
,
Dynamik von Kapillarströmungen in Zylindrischen Rohren
,
Cuvillier Verlag
,
Göttingen, Germany
.
10.
van Mourik
,
S.
,
2002
, “
Numerical Modelling of the Dynamic Contact Angle
,” M.S. thesis, University of Groningen, Groningen, The Netherlands.
11.
van Mourik
,
S.
,
Veldman
,
A. E. P.
, and
Dreyer
,
M. E.
,
2005
, “
Simulation of Capillary Flow With a Dynamic Contact Angle
,”
Microgravity Sci. Technol.
,
17
, pp.
87
93
.10.1007/BF02872093
12.
Schulze
,
R.-D.
,
Possart
,
W.
,
Kamusewitz
,
H.
, and
Bischof
,
C.
1989
, “
Young's Equilibrium Contact Angle on Rough Solid Surfaces—Part I: An Empirical Determination
,”
J. Adhes. Sci. Technol.
,
3
, pp.
39
48
.10.1163/156856189X00038
13.
Chaouki
,
J.
,
Larachi
,
F.
, and
Dudukoviæ
,
M. P.
,
1997
,
Non-Invasive Monitoring of Multiphase Flows
,
Elsevier
,
Amsterdam
.
14.
Zucht
,
A.
,
Müller
,
A.
, and
Böhme
,
G.
,
2008
, “
Untersuchung der Phasengrenze eines fluiddynamischen Systems mit experimentellen und numerischen Methoden
,”
Forsch. Ingenieurwes.
,
72
, pp.
241
258
.10.1007/s10010-008-0084-x
You do not currently have access to this content.