EXPERIMENTAL STUDY ON CHARACTERISTICS OF DYNAMIC PRESSURE IN DIRECT CONDENSATION OF STEAM AND WATER : DURING STEADY STEAM DISCHARGING AND AIR CLEARING PERIOD

摘要

An experimental study was carried out to investigate the characteristics of the pressure oscillation generated from non-condensable gas-steam-water direct condensation in subcooled water during the steady steam discharging and air clearing period. Steam and/or air is discharged through an I-type sparger whose pitc over diameter ratio (P/D) varies from 2 to 5. The tests were divisible into two separate phases. In the first phase, a low pressure steady steam test, the test conditions were restricted to the condensation oscillatio regime. The pressure pulse shows a peak at a pool temperature around 50 ～ 80℃ depending on the sparger and the steam mass flux. The dominant frequency of pressure oscillation increases significantly with the subcooling temperature of pool water and it lies in the range of 100 ～ 760Hz. The P/D ratio has a stron influence on the magnitude of pressure oscillation. As the P/D ratio increases, the amplitude of the dynamic pressure increases significantly. In the second phase of the test, a high pressure air clearing test, the dominant frequencies and amplitudes that occurred during the air clearing period were measured by using piezoelectric type pressure sensor and the Blowdown & Condensation (B&C) loop at KAERI. The steam mass flux is within the range of 1,230 ～ 2,380kg/m~2-s. The results show that the dominant frequency shows a very similar trend with that of the low pressure steady steam test. The dominant frequencies of the air clearing period, however, vary in the range of 5 ～ 30Hz depending on the water temperature and the shape of sparger.