A Comparative Study of Annular Two-Phase Flow Using Phase Doppler and Laser Diffraction Techniques

Gas-Liquid annular two-phase flow is one of the most common flow regimes in many industrial equipment. In this flow regime, liquid in part appears as a film on the channel walls whilst the rest of the liquid is carried as drops by the gas flowing in the center of the channel. Drop sizes and their velocities play a vital role in processes involving heat and mass transfer. This information is more useful for the oil industry where inclined drilling has become a common practice. The effect of inclination on the drop sizes and their velocities is still unknown and requires further investigation. In this work, an inclinable two-phase flow rig has been developed and two laser techniques - Phase Doppler and Laser Diffraction - have been employed to investigate flow at various flow conditions. The Laser Diffraction system mounted on the rig gave drop size distributions in the flow channel as the column was rotated from the vertical to the horizontal position. The Phase Doppler system, on the other hand, was attached with the rig and was rotated along the flow column to give drop sizes and their velocities under the similar flow conditions. This paper compares the data obtained through these two techniques and also describes the limitations of each technique in making measurements under identical flow conditions. Problem, in employing these two laser techniques are quite different and have been explained in a greater detail. In the end some typical results for both techniques have been presented and fully analysed.