Local liquid fraction measurement in annular two-phase flow using x-ray microtomography

Annular-dispersed two-phase flow in pipes consists of a thin wavy liquid film covering the pipe wall and a gas core with entrained liquid droplets. Knowledge of the film thickness and entrained liquid fraction is of importance in numerous industrial applications, such as the thermal design of heat exchangers.
The application of X-ray microtomography to obtain these parameters in case of small diameter pipes is presented here. The three-dimensional, time-averaged liquid fraction distribution has been measured in air-water annular flow in a horizontal pipe. In combination with pressure drop measurements, the film and entrained liquid mass flow rates are derived using a simple annular flow model. The portrayed method may also serve as a basis for the validation of computational fluid dynamics simulations of annular flow.