GAS-LIQUID FLOW PATTERNS AT MICROGRAVITY CONDITIONS

Understanding two-phase flow at microgravity conditons is important to a variety of space applications, including the design of thermal transport systems for the anticipated high-power-level space station. Two-phase air-water flow pattern data are reported at microgravity conditions during a series of parabolic trajectories flown on the NASA KC-135 aircraft. The liquid superficial velocity ranges from 0.09 to 3.73 m/s, and the gas superficial velocity from 0.2 to 29.9 m/s. Bubble, slug, frothy slug-annular and annular flows are observed to exist. Transitions between the different flow patterns are analyzed based on a force balance approach. It is found that the gas-phase Weber number serves as an excellent criterion for the transitions from slug to frothy slug-annular flows, and also from frothy slug-annular to annular flows.