Modeling of the droplet entrainment fraction in adiabatic gas-liquid annular flow

The entrainment fraction, F_E, in annular flow is defined as the fraction of the total liquid flow in the form of droplets in the gas core. Its prediction is important for estimation of the pressure drop, liquid holdup, and dry-out in annular flow. A new correlation for the entrainment fraction as a function of the Weber number based on the superficial gas velocity is developed. The proposed correlation contains only two constants that are, in essence, based only on the superficial gas and liquid velocities. The present correlation was validated against the experimental data and models available in the literature. The correlation was found to predict the experimental data available in the literature for different pipe diameters, low and high pressures, single and multi-component fluids, and horizontal to vertical flow, and does not allow negative entrainment values at low liquid flow rates or a very large value that would exceed the maximum possible value.