Toshitsugu Nakao

Development of Simplified Wave-type Vane in BWR Steam Dryer and Assessment of Vane Droplet Removal Characteristics

Air-water experiments were performed for the BWR steam dryer in order to elucidate droplet removal characteristics of the vane. Based on the results, a simplified vane was developed and its droplet removal characteristics were confirmed by air-water experiments using a whole dryer model. Phase-Doppler anemometer was used to measure droplet diameter distributions. In the experiments of the current vane with four-wave stages and 120° bend angle, almost all of the droplets were found to be trapped in the first and second vane stages. For the air velocity of 3.1 m/s, 90% of the inlet droplets were trapped there and 4% were trapped in the third and fourth stages, resulting in 6% being carried over. Sauter mean diameters at the exit were 6 and 5μm while at the inlet they were 71 and 64μm for the respective air velocities of 1 and 3 m/s. Based on the Weber number evaluation, the possible mechanism for the fine droplet generation was considered to be the breakup of droplets due to impingement on the liquid film f...

Experiments on Convection Heat Transfer Along a Vertical Flat Plate Between Pools with Different Temperatures

This paper reports that to evaluate the heat removal capability of an external water wall-type containment vessel, which is a passive system for containment cooling, thermal-hydraulic behavior in the suppression and outer pools has been examined experimentally. The following results are obtained: A thermal stratification boundary, which separates the pools into an upper high-temperature region and a lower low-temperature region, is observed just below the vent outlet. The natural-convection heat transfer coefficients (HTCs) for the downward and upward flows that appear inside and outside the primary containment vessel wall are measured. The condensation HTCs in the presence of non-condensable gas, which affect heat transfer between the wet well and the outer pool, are measured along the long wall. The capability for decay heat removal in the external water wall-type containment vessel for a 600-MW (electric) plant is evaluated based on these results and is found to be large enough.

Synchronized Vibrations of a Circular Cylinder in Cross Flow at Supercritical Reynolds Numbers

Synchronized vibrations of a circular cylinder in a water cross flow at supercritical Reynolds numbers were measured. Turbulence intensities were varied to investigate the effect of the Strouhal number on the synchronization range. Self-excited vibration in the drag direction due to symmetrical vortex shedding began only when the Strouhal number was about 0.29, at a reduced velocity of 1.1. The reduced velocities at the beginning of lock-in vibrations caused by Karman vortex shedding decreased from 1.5 to 1.1 in the drag direction and from 2.7 to 2.2 in the lift direction, as the Strouhal number increased from 0.29 to 0.48.

Evaluation Model of Turbine Meter for Two-Phase Flow

An evaluation model of a turbine meter has been developed to predict two-phase liquid velocity. The model considers the effects of blade configuration and void fraction distribution. In order to verify its applicability, experiments in single-phase and two-phase flows were performed and the model was compared with existing theories. This report describes the model and the experimental results on single-phase and two-phase flows.