New Insight for Predicting Liquid Holdup in A Gas-Liquid Slug Flow

Accurate prediction of liquid holdup in slug flow regimes is one of the most challenging steps in slug flow modelling. This paper presents a new insight for predicting slug flow liquid holdup. The slippage between the phases in two-phase flow is the controlling factor of the in-situ liquid holdup. The proposed method is based on two dimensionless parameters, namely, the ratio of the no slip liquid holdup to the slip (in-situ) liquid holdup and the ratio of the superficial liquid to gas velocities. Slug flow data follows self-similar nonlinear symmetrical sigmoidal behaviour. The method is validated using a data bank collected from published data in literature in addition to the state-of-the-art Unified model. This method is a promising method for prediction of slug flow liquid holdup and slug flow sub regimes in general. For large superficial liquid to gas velocity ratios greater than 10 the no-slip holdup is equal to the slip holdup. Surprisingly, for high superficial gas velocity greater than 15.8 m/s of air-water flow, all data regardless of the pipe diameter and inclination angles follow exactly the same plot.