Measurement of multi-dimensional distribution of local bubble parameters in a vertical annulus under subcooled boiling conditions

Abstract

In this study, an experimental investigation was performed to measure the local bubble parameters in steam-water subcooled boiling flow in a vertical channel at near-atmospheric pressure. The test section was a vertical concentric annulus in which the electric heater rod was installed at the center of the flow channel. The effective heated section was 2 m in length, and inner and outer diameters of the annulus were 10 mm and 30 mm, respectively. The optical fiber probes were used to measure various local bubble parameters in the subcooled flow boiling. The local void fraction, bubble arrival frequency, bubble velocity, interfacial area concentration (IAC), and Sauter mean diameter were measured at four elevations, and their radial profiles were obtained at 10 points by traversing the sensing tip of optical fiber probes. The high-speed camera was also applied for visualization of flow structures at three elevations. In the experiments, the flow conditions were set for the heat flux of 198 ~ 377 kW/m2, the mass flux of 376 ~ 680 kg/m2s and the inlet subcooling of 12.3 ~ 15.8 K at a pressure ranging from 115 to 202 kPa. It is expected that the obtained datasets will be useful for assessment of boiling models implemented in a CFD-scale analysis code.