Influence of Noncondensable Gas–Dust Mixture on Direct Contact Condensation of Steam at Atmospheric Pressure

At the Department of Civil and Industrial Engineering (DICI) of the University of Pisa, an experimental research program, funded by International Thermonuclear Experimental Reactor (ITER) Organization, concerning steam direct condensation in a flux containing also noncondensable gas and dust, was carried out. This mixture of fluids and dust is injected into the ITER pressure suppression tanks during a loss of coolant accident (LOCA) in the Vacuum Vessel. The aim of the research program is to determine the steam condensation efficiency in such conditions. Experimental tests were performed injecting this mixture in a tank partially filled with water. Alumina was used to simulate the actual dust present in the ITER Vacuum Vessel. Mass flow rates, temperature, and pressure of the different fluids involved were recorded during the tests. The steam condensation into the subcooled water pool at a temperature ranging between 318 and 369 K was investigated to determine the condensation regimes occurring during the mixture injection. The values of the fraction of the energy absorbed by water, dust, and metallic structures of the heat losses and of the average heat transfer coefficient were determined considering pure steam, steam-dust and steam-air-dust injection. The average heat transfer coefficient, determined calculating the steam jet surfaces by means of image elaboration, was compared with empirical correlations.