Numerical investigations on steam-air condensation heat transfer enhancement outside helical coiled tube.

The high efficiency heat extraction from the containment in severe accident is of utmost importance for nuclear power plants, and the Passive Containment Heat Removal System (PCS) is utilized for removing heat efficiently in third generation nuclear units. In order to enhance external steam-air condensation heat transfer, previous studies have primarily focused on specific structures, rib tubes, S-shaped tubes, or inclined tubes bundles, for instance. In the present study, a novel structure of helical coiled tube was designed and its external heat transfer characteristics were obtained through numerical simulation. The effects of coiled pitch, radial helical pitch, tube diameters and heights, two tube arrangements of vertical and horizontal on heat transfer characteristics were elucidated. It can be concluded that radial helical pitch and coiled pitch jointly impact the heat transfer, a proper large radial helical pitch and narrow coiled pitch can result in an approximate 9% enhancement in condensation heat transfer coefficient (h a), and the utilization of narrowed pipe diameters and longer tube heights facilitates the augmentation of heat transfer. Moreover, for vertical arrangement, h a can be enhanced over 15% by rising tube numbers, for horizontal arrangement, h a primarily influenced by tube pitch, the heat transfer is deteriorated by narrow tube pitch, but improved by widening them. • A novel effect that influences the external condensation heat transfer was proposed. • Derived condensation behavior during steam-air external condensation on helical coiled tube. • Effects of various parameters on heat transfer characteristics outside helical coiled tube were elucidated. • A helical tube bundle structure exhibiting exceptional heat transfer performance was obtained. [ABSTRACT FROM AUTHOR]