Measurements of Bubbly Flow in a Subchannel by using Optical Sensor Probe

Understanding of the two-phase flow structure in a subchannel is extremely important in a view point of the safety analysis in nuclear power plants. The basic characteristic of a two-phase flow is clarified by two parameters such as void fraction and interfacial area concentration. So, extensive analytical and experimental studies have been performed on basic flow channels such as round tube and annulus. But studies on subchannels were very limited because of the geometrical complexity. Recently, experimental studies on a rod bundle have been published. Yun et. al. have been presented the interfacial flow structure of subcooled water boiling flow in a subchannel of a 3x3 rod bundle. Paranjape et. al. have been obtained a flow regime maps for an adiabatic air-water two-phase flow through a flow channel with 8x8 rod bundle. In spite of various experimental efforts to understand the flow structure in a subchannel, there were still coarse and insufficient experimental data. From this circumstance, this study presents precise measurements in a subchannel with a 4x4 rod bundle by using a two sensor optical probe