Local temperature and phase measurement in water-melt multiphase flow with bifunctional probe and electrical signal processing

Shibamoto, Yasuteru ; Sagawa, Jun*; Kukita, Yutaka*; Nakamura, Hideo  

A bifunctional probe was developed for simultaneous, high-speed measurement of local temperature and phase of fluid at the same place. It was designed for application to water/melt multi-phase experiments involving transient boiling of water on the surface of molten metal. An unsheathed thermocouple (TC) of a small wire diameter was used for phase detection, that is distinction of melt/water/vapor phase, as well as for temperature measurement of each phase. The phase was detected by measuring the electric impedance between the TC and the ground. A 100-kHz AC signal was imposed on the TC wire for this purpose. The AC signal was filtered out from the temperature signal before it was amplified. With the first design of low-pass filter (LPF), however, a large noise was induced in the temperature signal every time the TC was grounded electrically by contact with molten metal. This problem was overcome by redesigning the LPF. The final design succeeded in measuring the quick movements of interface and the temperature changes in the individual phases in a water-melt-vapor multiphase flow.