Measurement and Prediction of Drop Size and Velocity in Gas-Liquid Churn Flow and Churn- Annular Flow

Gas-liquid churn flow is one of the most common flow patterns in gas well production. A profound understanding of the distribution of the droplet size and velocity distribution is of utmost importance for the calculation of pressure drop and prediction of liquid loading in gas well. This study explores the distribution of droplet size and velocity in churn and churn-annular flow. Based on experimental data, a new model for the droplet Sauter mean diameter, d₃₂, in churn flow is proposed. In this study, the droplet size and three velocity components of stirred flow and stirred circulation were measured using a phase Doppler anemometer (PDA). The distribution of size and velocity of droplets were then analyzed, and the change of droplet size and slip ratio under different gas and liquid flow rate is obtained. Finally, a new correlation of the Sauter mean diameter was proposed by using the correlation coefficient to fit the experimental results. The experimental results shows the size of droplet decreases significantly as the superficial gas velocity increases, the effect of liquid phase velocity on droplet size is not obvious. Droplet size is mainly distributed around relatively small values (100 μm < d < 200 μm) with a uniform distribution, and only a few large droplets (d > 200 μm) exist. The droplet axial velocity decreases with increasing droplet size, smaller droplets have greater axial speed range. The axial velocity of droplet increases while the radial velocity decreases during their migration from the liquid film to the centerline. This new correlation of d₃₂ agrees well with experimental data and reduces the mean relative error between experiment and model to 9.4%. This work provided an experiment study on droplet size and velocity distribution in churn flow and churn-annular flow, and a new correlation for the Sauter Mean Diameter was proposed, which significantly improved the prediction accuracy of droplet size and can be useful to the two-phase pipe flow modeling in liquid-producing gas wells.