On the Unexpectedly Large Effect of the Re-vaporization of the Condensate Liquid Film in Two Tests in the Panda Facility Revealed by Simulations with the Gothic Code

The recently concluded OECD SETH project included experiments on basic flows and gas transport and mixing driven by jets and plumes in the multi-compartment geometry (two large, connected vessels) of the PANDA facility, which have been simulated with the advanced containment code GOTHIC. The two experiments considered here featured injection of saturated steam in one vessel and venting from the second vessel, both being initially filled with pure air. In these two tests steam was injected at different positions. In both tests, condensation produced a liquid film on the walls in the region above the injection. For these tests the analyses with GOTHIC provided strong indications that the key phenomenon for the simulation was the re-vaporization of the condensate film, and more precisely the amount of run-down liquid which flows into the lower part of the vessel, its velocity and its re-vaporization in that region. The unexpectedly large role played by the liquid film suggested a review of the modeling issues associated with the simulation of run-down condensate. It was concluded that important gaps exist in the knowledge of several fundamental processes, which should be considered in future theoretical and experimental work related to containment thermal-hydraulics.