Experimental Study on Boiling Two-Phase Flow Instability in a Single Helically Coiled Tube

The boiling phase change happened in the heating channel will induce flow instability. Thus, studying the two-phase flow instability in helically coiled tubes is of great significance in the design and operation of helical-coil one-through steam generators. In this paper, the boiling two-phase flow experiment in a single helically coiled tube is carried out on the thermal experimental platform, and the flow instability phenomenon when boiling two-phase flow occurs in the helically coiled tube is studied. In the experiment, the boiling two-phase flow instability is classified by analyzing the variation and spectral characteristics of parameters such as flow rate and pressure drop in the helically coiled tube at different times during the rise of heating power. The results show that when the experimental parameters are in the range of 0.1~3 MPa for pressure, 300~1200 kg/h for flow rate, 20~100℃ for inlet subcooling and 0~200 kW for heating power in the experimental section, the helically coiled tube heating channel exhibits flow drift instability as the power increases. Once the flow drifts to another flow value, low-amplitude high-frequency density wave oscillations occur under low steam quality conditions, while high-amplitude low-frequency density wave oscillations occur under high steam quality conditions. In addition, the increase of inlet subcooling, inlet flow rate and system pressure will improve the stability of the system.