An Experimental Investigation on Subcooled Boiling Flow in a Vertical Annulus with Visualization and Measurement of Local Flow Parameters

A series of experiments were conducted to investigate flow structures and local temperatures in subcooled boiling in a vertical heated channel at a pressure approximately equal to atmospheric pressure. The test section was the internally heated annulus with an effective heated length of 2 m and hydraulic diameter of 20 mm; the heat flux, mass flux, inlet subcooling degree, and exit pressure were adjusted in the test. The boiling flow phenomena were recorded with a high-speed camera for three flow conditions. In addition, local void fraction profiles that had been measured by optical fiber probes were identified. Furthermore, the surface temperatures of the heater rod were obtained, and the radial distributions of fluid temperature were measured by traversing precisely the sensing tip of the thermocouples.