Abstract
Condensation of steam inside a reactor containment during Loss of Coolant Accident (LOCA) situations is essential to maintain the integrity of the containment. In such situations, steam condenses, in the presence of Non-Condensable Gases (NCGs), on the containment walls as well as on the surfaces of different safety devices/components employed inside the containment. These surfaces generally have different orientations, such as vertical, horizontal, or inclined at different angles. Literature indicates that condensation heat fluxes are significantly different at different inclination angles of the test surface. A large experimental database and conclusive results are available for steam condensation on long vertical surfaces. However, condensation on inclined surfaces is not completely understood. Therefore, it is essential to perform further studies to better appreciate the condensation heat fluxes at different inclination angles of the test surface, and thereby understand the overall containment thermalhydraulics. In the present work, steam condensation in the presence of air is studied at all possible orientations of the test surface, i.e., from condensation over the horizontal test surface to condensation underneath the horizontal test surface. An experimental plan is devised to perform steam condensation experiments at 13 different inclinations of the test plate, varying from -90° (underneath the test surface) to +90° (over the test surface) in increments of ~ 20°. The experiments are performed at two bulk pressures (1.7 bar abs., and 4.2 bar abs.), and three different steam-air mixture compositions (pure steam, i.e., 0%, 22% and 40% w/w air in the steam-air mixture). The heat flux for the upward facing surface is found to decrease continuously from 0° to +90°, whereas it first increases in the downward facing surface (0° to -70°) and then decreases afterwards. Further, the condensation heat flux for the downward facing surface is found to be always higher than the upward facing plate for a particular inclination angle. The primary reason for higher heat fluxes in the downward facing surface is the unstable gas boundary layer due to higher molecular weight of air compared to the steam-air bulk mixture.
