Pressure and fluid oscillations in vent system due to steam condensation, 2

A parametric analysis was conducted to determine from experimental data the characteristics of pressure oscillations generated when steam fed through vent tubes is made to condense in a pool of subcooled water. The occurrence of the high-frequency oscillations (around 100 -- 200 Hz with the present experimental arrangement) was found to be intimately related to the extent of development of the low-frequency component of oscillations representing either the reciprocating movement of the steam-water interface in the vents--conducive to ''chugging''-- or under conditions where the interface had descended into the water pool, the alternating expansion and contraction of the steam bubble formed around the vent exit. Four patterns of occurrence of the high-frequency pressure oscillations were distinguished, each pattern corresponding to a specific range of parameters governing the experimental conditions, as defined by zones on a map drawn on the coordinate plane relating the pool-water temperature to the steam mass flux fed through the vent tubes. It was noted, however, that the differences in the patterns of oscillation occurrence did not influenece the basic characteristics of the wave shape presented by the pressure oscillations, which suggested a common mechanism governing the generation of high-frequency oscillation, whether occurring in pulsed form accompanied by ''chugging'' or in the continuous form of condensation oscillation. Associating the foregoing observation with the fact that the steam mass flux flowing through vent tubes varies in synchronization with the interface motion-which is intimately related to alternations in the degree of subcooling of the water in the vicinity of steam-water interface, a coherent explanation is presented on the patterns of occurrence of the high-frequency oscillations, under both conditions of chugging and of condensation oscillation. (author)