High pressure annular two-phase flow in a narrow duct: Part I - Local measurements in the droplet field

Detailed measurements have been made in a high pressure, adiabatic (boiled at the inlet) annular flow in a narrow, high aspect ratio duct using a gamm a densitometer, hot-film anemometer and high-speed video photography. Measu rements of void friction, droplet frequency, velocity, drop size, and inter facial area concentration have been made to support the three-field computa tional capability. An important aspect of this resting is the use of a mode ling fluid (R-134a) in a vertical duct which permits visual access in annul ar flow. This modeling fluid accurately simulates the low liquid-to-vapor d ensity ratio of steam-water flows at high pressures. These measurements hav e been taken in a narrow duct of hydraulic diameter 4.85 mm, and a cross-se ction aspect ratio of 22.5. However, the flow displays profiles of various shapes not only in the narrow dimension, but also in the width dimension. I n particular, the shape of the void profiles depends on the entrained dropl et flux from the edges in the vapor core. The average diameter from these p rofiles compare well with the models developed in the literature, Interfaci al area concentration for these low density ratio flows is higher than the highest concentration reported for air-water flows. Video records show that along with the bow-shaped waves, three-dimensional lambda -shaped waves ap pear in annular flows for high flow rates. [S0098-2202(00)00902-0].