Original Article
Experimental research on the mechanisms of condensation induced water hammer in a natural circulation system

https://doi.org/10.1016/j.net.2021.05.035Get rights and content
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Highlights

  • The CIWH characteristics were analyzed in the NCS.

  • Three types of formation mechanisms of CIWH were identified and analyzed by 67 CIWH events in the NCS.

  • Occurrence probability and conditions of each type of CIWH were analyzed.

Abstract

Natural circulation systems (NCSs) are extensively applied in nuclear power plants because of their simplicity and inherent safety features. For some passive natural circulation systems in floating nuclear power plants (FNPPs), the ocean is commonly used as the heat sink. Condensation induced water hammer (CIWH) events may appear as the steam directly contacts the subcooled seawater, which seriously threatens the safe operation and integrity of the NCSs. Nevertheless, the research on the formation mechanisms of CIWH is insufficient, especially in NCSs. In this paper, the characteristics of flow rate and fluid temperature are emphatically analyzed. Then the formation types of CIWH are identified by visualization method. The experimental results reveal that due to the different size and formation periods of steam slugs, the flow rate presents continuous and irregular oscillation. The fluid in the horizontal hot pipe section near the water tank is always subcooled due to the reverse flow phenomenon. Moreover, the transition from stratified flow to slug flow can cause CIWH and enhance flow instability. Three types of formation mechanisms of CIWH, including the Kelvin-Helmholtz instability, the interaction of solitary wave and interface wave, and the pressure wave induced by CIWH, are obtained by identifying 67 CIWH events.

Keywords

Condensation induced water hammer
Two-phase flow
Natural circulation system
Steam slug
Formation mechanisms

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