Research on a Numerical Analysis Method of Two-Phase Flow Instability in HOTSG

Density wave oscillation (DWO) is a fatal phenomenon in helical coil once-through steam generator (HOTSG), threatening the safe and stable operation. The effects of feedwater temperature, flow rate and outlet pressure on DWO were analyzed with self-developed code LOCUST which was validated with experiment results first. In this paper, LOCUST code was used to explore HOTSG two-phase flow instability characteristics, which was validated with experiment results. The critical pressure drop of the CNPRI HOTSG flow instability experiment was predicted, and the effects of feedwater temperature, feedwater flow rate and outlet steam pressure on density wave flow instability (DWO) of HOTSG were obtained. The results show that the flow instability could be accurately predicted with the time domain method. At the same conditions, the high pressure and large flow rate were conducive to reduce the probability of DWO. Moreover, the stable operating region was obtained according to the feedwater temperature.