Numerical Investigation on the Enhancement of Steam-Air Condensation Heat Transfer Outside Spiral Pipes

Abstract When loss of coolant accident (LOCA) or main steam line break accident (MSLB) occurs in the nuclear power plant, a large amount of high pressure and temperature steam will be released into the air space, in HPR1000, a Passive Containment Heat Removal System (PCS) is utilized for extracting heat from containment during reactor accident scenarios. Due to the non-condensable gas near the condensation wall will generate additional thermal resistance, it is crucial to enhance external heat transfer in this situation. In this study, the Computational Fluid Dynamics (CFD) method was employed to investigate the heat transfer characteristics of steam-air condensation outside spiral pipes. The effects of different pipe initial spiral radius range from 0.02 m to 0.2 m, pipe pitch of 1.1d and 2.0d, pipe diameter, also pipe bundle on heat transfer characteristics were analyzed. The results indicate that the spiral pipe has an excellent condensation heat transfer enhancement. For a single spiral pipe, a narrow initial spiral radius will deteriorate heat transfer while enhancing heat transfer after increasing the initial spiral radius. When it comes to spiral pipe bundle, increasing the radial pitch enhances air layer shedding, thereby improving condensing heat transfer ability. However, in terms of large pipe pitch, the impact of increasing the radial pitch is minimal.