The characteristics of horizontal, annular two-phase flow were experimentally investigated for a mixture of low-pressure air and water. The experiments were conducted in a horizontal loop consisting of a 50.3 mm diameter circular pyrex glass piping with an overall length of 16 m.
For a very wide range of flow conditions, the liquid film characteristics were measured as a function of a circumferential position. The local liquid entrainment flux measurements were made in the gas core. In addition, pressure drop in the developing and fully-developed zones as well as the average void fraction were measured. The measured values of those physical quantities and the highest circumferential location from which liquid film starts to form toward the tube bottom are presented, and the effects of various flow parameters on them are examined. Results are analyzed, and the compatibility of the liquid film thickness measurements with the average liquid fraction is discussed. Simple empirical correlations for the liquid film thickness distribution and entrainment fraction are proposed.