Experimental study on two-phase natural circulation flow instability under low pressure and low steam quality

The author studied the two-phase flow instability for a vertical upward tube in natural circulation loop and the exit steam quality of test section is about 1%. Some oscillation curves are obtained in the experiment, and unstable mechanism is also presented. By means of dimensionless analysis of partial differential equations, an equation describing the relation among the system parameter at the threshold conditions is derived to give an empirical correlation for threshold conditions of flow instability. The experiment ranges are as follows: P = 0.2 - 0.6 MPa ΔTsub = 5 - 40 degree C G 450 - 1600 kg/(m2s)