Abstract
To clarify fundamentals of gravity effect on the behaviors of two-phase flow, experiments were conducted onboard aircraft. Annular flow of air-water mixture was realized independent of gravity level varying along a parabolic trajectory. Effect of gravity on the pressure drop was clarified systematically for a vertical upward flow in a tube for different combinations of liquid and gas flow rates. Pressure drop becomes low when gravity is reduced, and the effect of gravity decreases with the increase of gas or liquid flow rate. The gravity effect was corresponded to the change of interfacial shear stress on the surface of annular liquid film, and a method to correlate the gravity effect on interfacial friction factor having direct influence on the pressure drop was introduced. To clarify gravity effect on two-phase forced convective heat transfer, distribution of velocity and temperature across the annular liquid film were analyzed in detail based on measured values of pressure drop under different gravity conditions.
