自由界面渦による気相巻き込み現象の定量評価

Abstract

On the gas-liquid interface of a sodium-cooled fast reactor, gas (bubble) entrainment can be caused by free surface vortices, which may result in, e.g. disturbance in core power. Therefore, it is important to develop an evaluation model to predict accurately the entrained gas flow rate for the prevention of such undesirable phenomena. In the previous studies, simple gas entrainment experiments have been conducted, in which, typically, the gas entrainment is caused by free surface vortex in an upper-tank and the entrained gas is separated from liquid in a lower-tank which is connected with the upper-tank by a suction pipe. The entrained gas flow rate had been measured while the liquid flow parameters, e.g. liquid level or flow rate, are changed. However, the influence of the pressure difference between the upper and lower tanks had not been focused on those studies. In this study, to measure accurate the entrained gas flow rate, a simple gas entrainment experiment is conducted with focusing on the effect of the pressure difference between upper and lower tanks. The pressure difference between upper and lower tanks are controlled by changing the gas pressure in the lower-tank. As a result, it is confirmed that the entrained gas flow rate increases with increasing the pressure difference between upper and lower tanks. By the visualization of the two-phase flow in the suction pipe, it is also observed that the pressure drop in the suction pipe increases with the increase in the entrained gas flow rate when intermittent liquid plug is generated in the two-phase flow.