Influence of Water Sub-Cooling on Discharge Characteristics in a Water Storage Tank

The influences of water sub-cooling on water discharge behaviors from the water storage tank were studied experimentally with a test rig, which consists of a water vessel, a steam supplier, valves and piping. From this study, it is found that the gravitational discharging process is effected strongly by the steam condensation, taking place between steam and cold water in the vessel during discharge. Increased sub-cooling of the water, enhances the steam condensation, and promotes a deeper penetration of steam into water. The two modes of condensation identified in this study are: steam-supply-limit-mode and steam-condensation-limit-mode. The first mode occurs at the primary discharge period if water sub-cooling is large than a certain value, for example, 50 deg. C sub-cooling in this study. Conclusions were derived based on this study for the impact of subcooling on discharge characteristics with respect to flow, pressure, and other parameters. Some suggestions to avoid or reduce undesired phenomena are also presented. (authors)