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Multiphase Science and Technology

ISSN Print: 0276-1459
ISSN Online: 1943-6181

Multiphase Science and Technology

DOI: 10.1615/MultScienTechn.v20.i3-4.20
pages 239-263


A. Dudlik
Fraunhofer UMSICHT, Oberhausen, Germany
H.-M. Prasser
Department of Mechanical and Process Engineering (MAVT), Swiss Federal Institute of Technology (ETHZ), ML K 13, Sonneggstrasse 3, 8092 Zürich, Switzerland
A. Apostolidis
Fraunhofer UMSICHT, Oberhausen, Germany
A. Bergant
Litostroj E.I. d.o.o., Slovenia


The water hammer and inertia-driven cavitation hammer phenomena caused by the activation of fast-acting valves were studied in a pipeline test facility at Fraunhofer UMSICHT in the context of the EURATOM project WAHALoads. The main goal of the project is the prediction of the loads on equipment and support structures. The presented experiments tackle some scenarios typical for power plants and supply material for code validation with regard to the modeling of both thermohydraulic effects and fluid-structure interaction. The test facility Pilot Plant Pipework, representing an approximately 230 m long experimental pipeline, was upgraded in order to allow experiments at system pressures of up to 30 bar at maximum temperatures of about 180° C. The test rig was further equipped with a test segment that simulates a piping system and the associated supports typical for a (nuclear) power plant. For a better understanding of thermohydraulic processes during cavitation behind the fast-acting valve, novel instrumentation was applied. Wire-mesh sensors as well as local void probes were equipped with integrated microthermocouples and used for the local instantaneous measurement of both void fractions and fluid temperature. The fast temperature measurement combined with the instantaneous detection of the passage of the gas-liquid interface measurement reveals insights into the condensation heat transfer controlling the speed of the void collapse in the case of a condensational water hammer.