Behavior of Drag Disc Turbine Transducers in Steady-State Two-Phase Flow

Many experiments being conducted to investigate the hypothesized loss-of-coolant accident (LOCA) in nuclear power plants involve the measurement of two-phase flow. This paper describes an experiment conducted to determine the behavior of a drag-disc turbine transducer (DTT) in a high pressure, high temperature, steam-water steady state environment. DTTs have been used extensively to measure mass flow rates in the Loss-of-Fluid-Test (LOFT) experiments. Drag discs and turbines have been used in many other safety related facilities. However, the performance of these instruments is highly dependent on flow regime and void fraction and this dependence makes data analysis difficult. Experiments conducted in separated flow are described in this paper. The results show the measured mass flow rates can be corrected if a three-beam gamma densitometer is available, if the calculated density ratio correction is less than three, and if the velocity measured by the turbine is greater than 2 m/ s. The results also suggest that the turbine and drag disc measure local mass average quantities averaged over the area of the DTT.