A Study on Thermo-Hydraulic Instability of Boiling Natural Circulation Loop with a Chimeny (2nd Report, Experimental Approach to Clarify the Flow Instability in Detail)

Experiments are are conducted to investigate two-phase flow instabilities in a boiling natural circulation loop with a chimney induced by flashing in the chimney at lower pressure. The type of instability that occurred in the experiments is suggested to be density wave oscillations induced by flashing in the chimney. The differences from other instabilities such as geysering, flow pattern transition instability, and natural circulation oscillations are discussed on the basis of the dynamic characteristics, the oscillation period, and the transient flow resume.