[3K10-15] Two-Phase Flow and Phase Change 3

[3K11] Detailed temperature measurement of natural convective subcooled boiling in a narrow gap between a cylindrical heater and a flat plate

*Mao Takeyama¹, Tomoaki Kunugi¹, Zensaku Kawara¹, Takehiko Yokomine¹, Takano Kenji¹ (1. Kyoto Univercity)

Keywords:boiling two-phase flow, narrow gap, detailed temperature measurement, high tempo-spatial resolution visualization

When a loss of flow accident, a natural convective subcooled boiling would occur in the sub-channels of the fuel assembly.This study was focused on the natural convective subcooled boiling in a narrow gap between a cylindrical heater and a flat plate, that structure is similar to a subchannel composed of a fuel rod and the channel-box wall of fuel assembly, and measured the detailed temperature field in the gap by using a miniature thermocouple.In the experiment, a narrow gap of 1mm width was made by a cylindrical heater and a flat plate installed in a water pool. Temperature fields in the narrow gap were measured with 250 micron-dia. thermocouple. The wall effects on the temperature field under the various degrees of subcooling and the heat fluxes were discussed. Moreover, flow visualization with a high speed camera with high tempo-spatial resolutions were conducted.As a result, it was found that the big boiling bubbles were generated, and fill in the gap, and then the flow and temperature fields in the gap were influenced by them.