Studies On The Effect Of Rolling Condition On Two-phase Flow Pattern In Horizontal Tubes

Nuclear power ships would be influenced by ocean conditions, such as rolling, incline and heave, so, to distinguish the two-phase flow patterns is very important to analyze the flow and heat transfer's characteristic.This study aims at experimentally and theoretically effect of rolling condition on gas-liquid flow patterns in horizontal tubes.All the experiments were carried out in a rolling test facility at atmospheric pressure and temperature. Air and water were used as flowing medium co-flow through test section, the test section is made of transparent tube and fixed horizontally on rolling facility. In condition of horizontal, incline and rolling, tubes of two different inside diameters: 25mm and 34.5mm were used respectively. During the experiments, the flow pattern was measured by visual observation, pressures were measured by differential pressure transmitter and void fractions were measured by fast globe valve. All of the dynamic data were timely collected and recorded by computer system.The result of experiment showed that, flow characteristics of different period in one cycle were dissimilitude. To low velocity two-phase flow, the flow is unstable under the effect of rolling, increasing the liquid velocity and gas velocity, the effect of rolling is weaken, and the flow patterns were similar with that in steady condition, such as upward declined flow and. downward declined flow. By analyzing the pressure drop's characteristics, it's showed that the signal of pressure drop in rolling condition have objectively provided information of flow patterns. Through analyzing the flow patterns in different conditions, it's found that inside diameter of tube, incline angle, rolling period and maximal rolling angle have significant effect on the transition of flow patterns.The definition and the classification of flow patterns in horizontal pipe under rolling condition were performed, which combined with the fluctuation characteristics of pressure drop can determine flow pattern. Flow pattern transition were described, and flow pattern maps were drawn, through the compare of maps, the effect of main parameters on flow pattern transition were analyzed, the parameters include inside diameter, incline angle, rolling period and maximal rolling angle. Through the analysis of single phase water with rolling motion, a new semi-empirical formula on single-phase frictional coefficient has been proposed which includes the effect factor of Reynolds number, rolling period and maximal rolling angle. The force analysis of annual flow under rolling condition was performed, and calculation formula for axial pressure drop on pipe inner surface has been proposed.