The behaviour of a steam slug in upward water flow in an isothermal vertical pipe at a reduced pressure.

Abstract

We investigated the behaviour of a steam slug which was rising in an isothermal vertical pipe at a reduced pressure. When the water temperature around the steam slug was higher than the saturated temperature, the slug grew upon rising in the pipe. The temperature difference between the steam slug and the surrounding water was increased, when water velocity in the pipe was increased or a static pressure to the system was decreased. The increase in velocity of the leading edge of a rising steam slug was caused by the slug growth. But the trailing edge velocity of a steam slug was equal to that of an air slug without growth in water. As the water temperature around the tip of the steam slug was locally higher than the mean flow temperature, it was regarded that the liquid vaporization, which caused the slug growth, occured at the front face of the slug.