Experimental study on two-phase flow instability in helically coiled tube under rolling motion

Helically coiled tube under ocean conditions will subject to serious two-phase flow instability. This study experimentally investigated two-phase flow instabilities in a helically coiled tube under static and rolling conditions. Under static condition, Density Wave Oscillation (DWO), Pressure Drop Oscillation (PDO), and Thermal Oscillation (TO) are observed, and the stability map for DWO is established. Under rolling condition, Singlephase flow oscillation, PDO, and DWO are observed, and compared to the phenomena of static condition. It is found that rolling condition can induce flow oscillation, making the DWO and PWO more severe. Through Fast Fourier Transform (FFT) analysis, it is found that impact of rolling conditions on flow instability diminishes as heating power is increased. In addition, the parameter effects of inlet subcooling, volumetric flow rate, system pressure, rolling angle and rolling period on flow stability are investigated.