Local Flow Structure of Subcooled Boiling Flow of Water in a Heated Annulus

Local measurements of flow parameters were performed for vertical upward subcooled boiling flows in an internally heated annulus. The annulus channel consisted of an inner heater rod with a diameter of 19.0 mm and an outer round tube with an inner diameter of 37.5 mm, and the hydraulic equivalent diameter was 18.5 mm. The double-sensor conductivity probe method was used for measuring the local void fraction, interfacial area concentration, bubble Sauter mean diameter and gas velocity, whereas the miniature Pitot tube was used for measuring the local liquid velocity. A total of 32 data sets were acquired consisting of various combinations of heat flux, 88.1–350.9 kW/m², mass flux, 469.7–1061.4 kg/(m²s) and inlet liquid temperature, 83.8–100.5 °C. Six existing drift-flux models and six existing correlations of the interfacial area concentration were evaluated by the data obtained in the experiment.