Characteristics of Liquid Film Thickness of Air-Water Annular Two-Phase Flow in a Helically Coiled Tube. Horizontal Coil.

Abstract

An experimental study has been carried out to clarify the characteristics of the liquid film thickness of air-water two-phase flow in a helically coiled tube placed horizontally. The distribution of the time-averaged local liquid film thickness around a tube periphery varies along the circumference of the coil at low gas velocities. A subsidiary peak of the film thickness forms on the outer side of the coil for large liquid flow rates. The mechanism of peak formation varies with magnitude of the gas velocity. The peripherally averaged liquid film thickness of a tube section in a coiled tube is thicker than that in a straight tube at high gas velocities. When the superficial gas velocity exceeds 20∼30 m/s, the centrifugal force of the gas-phase is dominant on the distribution of the film thickness around the tube periphery at the lower section. At a high gas velocity, it is expected that the characteristics of the liquid film on the downward or upward section of the coil are similar to those in a microgravity environment.