Abstract
Many upcoming new generation reactors employ natural circulation for heat transfer in normal mode of operation. Natural circulation systems are simpler and safer than their forced circulation counterparts. However, these systems are prone to flow instability which are undesirable due to several reasons. In the present work, a rectangular glass loop, wherein cooler is just above the heater, has been considered for experimental and numerical investigation at atmospheric pressure. Heat addition from room conditions has been studied to understand the natural circulation loop dynamics, checking the possibility of occurrence of instability with the new orientation of the heater and the cooler. Experiments were performed at different power levels and coolant flow rates. CFD analyses were performed for all the cases investigated experimentally using the commercial CFD code ANSYS FLUENT 14.0. No instability was observed during the experiments and none during the simulations done for the duration of the experiments.
Kurzfassung
Viele Reaktoren der neuen Generation nutzen natürliche Zirkulation zur Wärmeübertragung im Normalbetrieb. Natürliche Zirkulationssysteme sind einfacher aufgebaut und sollen sicherer als ihre Pendants mit Zwangsumlauf sein. Allerdings sind sie anfällig für Strömungsinstabilitäten, die aus verschiedenen Gründen unerwünscht sind. In der vorliegenden Arbeit wurde eine rechteckige Glasschleife, bei der sich der Kühler knapp oberhalb des Heizers befindet, für experimentelle und numerische Untersuchungen bei Atmosphärendruck verwendet. Dabei wurde die Wärmezufuhr aus dem Raum untersucht, um die Dynamik der natürlichen Zirkulationsschleife zu verstehen und den Einfluss der vertikalen Anordung von Heizer und Kühler auf die Entstehung von Instabilitäten untersucht. Es wurden Experimente mit verschiedenen Leistungsstufen und Kühlmitteldurchflussmengen durchgeführt. Für alle untersuchten Fälle wurden CFD-Analysen mit dem kommerziellen CFD-Code ANSYS FLUENT 14.0 erstellt. Dabei wurden Instabilitäten weder während der Experimentdauer noch während der Berechnungen beobachtet.
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