Post-CHF two-phase flow with low wall-superheat

Heat transfer was measured to a two-phase flow in the post-CHF region under liquid-heated conditions and low wall-superheat. The boiling fluid was water at high pressure, 7.0–15.3 MPa, and mass fluxes in the range of 720–3200 kg/m²s. Experiments were performed in a vertical tube with a 10 mm inside diameter and a 13.1 m heated length. In considering the effects of thermodynamic non-equilibrium and direct drop-wall heat transfer at the low wall-superheats of this investigation (25–100°C), 13 correlations, models and analysis were compared to the data. A review of these formulations is presented including development bases and approaches. The effects of both non-equilibrium and drop-wall heat transfer were evaluated, and recommendations are presented for post-CHF heat transfer predictions at low wall-superheat.