A new method of entrainment fraction measurement in annular gas–liquid flow in a small diameter vertical tube

A new method was introduced to measure liquid entrainment fraction in gas–liquid two-phase upward annular flow in a vertical tube (i.d.=9.525 mm). In this method, a new liquid–gas separator was designed and the chemically-based titration method was used to effectively measure the entrainment fraction in real time. Experiments were conducted at low system pressure (∼1 atm), and relatively low gas and liquid superficial velocities (Vsg=25.8–45.5 m/s, and Vsl=0.15–0.30 m/s). Data analysis shows that the results are repeatable and occupy the range commonly seen in annular flow. The entrainment fraction was found to be under 7% for all the experimental set points. The repeatability of the test results and comparisons with previous entrainment data indicate that the new technique can perform as well as the film removal technique.