Experimental Study of Flow Instability in a Natural Circulation System with Sub-cooled Boiling

Experimental study has been performed to investigate the flow instability in a natural circula- tion system with sub-cooled boiling by using Freon-12 as the working medium. In the experiments, two kinds of flow instability, flow instability with high frequency and flow instability with low frequency, were found for most conditions. It is shown that the flow instability with high frequency belongs to acoustic oscillation and the flow instability with low frequency is density wave instability. In the experiments the effect of the parameters of the working medium on the onset of the flow instabilities in the system were investigated. The stability boundaries were determined through the experiments. By means of dimensional analysis of integral equations, the common correlations describing the threshold condition of onset of the flow instabilities were obtained.