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Experiments were conducted for the purpose of investigating the phenomenon of condensation-induced waterhammer in an ammonia refrigeration system. Waterhammer was initiated by introducing hot ammonia gas over static subcooled ammonia liquid placed in a horizontal 146.3 mm diameter carbon steel pipe approximately 6.0 m long. By means of fast response piezoelectric pressure transducers and a high speed data acquisition system rapid dynamic pressures were recorded whenever a condensation-induced event occurred. Moreover, by means of top-mounted diaphragm pressure transducers sensing gas pressure the speed of liquid slugs propagating along the pipe was determined. Based upon careful interpretation of the results criteria for the transition from initial stratified flow to slug flow were established, similar to the so-called Taitel-Dukler correlation in two-phase flow literature. Kondensationsinduzierte Druckstose in einem horizontalen Rohr. Zur Untersuchung von kondensationsinduzierten Druckstosen in einer Ammoniak-Kalteanlage wurden Experimente an einer Versuchsanlage durchgefuhrt. Kondensationsschlage wurden ausgelost, indem in einem horizontalen, 6 Meter langen Stahlrohr mit einem Durchmesser von 146,3 mm heiser Ammoniak-Dampf uber eine unterkuhlte ruhende Flussigkeitsschicht aus Ammoniak geleitet wurde. Mit Hilfe einer hochtransienten Druck-Messtechnik und einem Hochgeschwindigkeitssystem zur Datenerfassung wurden die dynamischen Drucke, die bei einem Kondensationsschlag auftraten, aufgezeichnet. Daruber hinaus konnte die Geschwindigkeit der entstehenden Flussigkeitspfropfen durch Membran-Druckaufnehmer, die am oberen Scheitel des Rohres angebracht waren, bestimmt werden. Uber eine sorgfaltige Interpretation der Messergebnisse konnte ein Kriterium fur den Ubergang von Schicht- zu Pfropfenstromung aufgestellt werden, vergleichbar mit dem von Taitel-Dukler, das aus der Literatur zu Zweiphasenstromungen bekannt ist.

Simulations of condensation-induced water hammer with one-dimensional two-fluid model requires explicit modeling of slug formation, slug propagation, and in some cases slug decay. Stratified flow correlations that are more or less well known in 1D two-fluid models, are crucial for accurate description of the initial phase of the slug formation and slug propagation. Slug formation means transition to other flow regime that requires different set of correlations. To use such two-fluid model for condensation induced water hammer simulations, a single slug must be explicitly recognized and captured. In the present work two cases of condensation-induced water hammer simulations performed with WAHA code, are described and discussed: injection of cold liquid into horizontal pipe filled with steam and injection of hot steam into horizontal pipe partially filled with cold liquid.