Two-group drift-flux model for dispersed gas-liquid flows in medium-to-large pipes

The two-fluid model is crucial in many industrial applications for optimizing system performance and ensuring safety. Interfacial area concentration, when multiplied by the corresponding driving potentials, represents the typical equation that expresses the transfers between mass, momentum, and energy. As a result, interfacial area concentration modeling is necessary to complete the two-fluid model. The two-group interfacial area transport equation is suitable for interfacial area concentration modeling; the equation classifies bubbles into two groups based on their drag coefficients. The two-group drift-flux model simplifies the procedure without adding more transport equations. This study introduces a new two-group drift-flux model developed for dispersed two-phase flow in medium-diameter pipes in upward flow. The asymptotic distribution parameter was determined to be 1.00 for group-one bubbles and 1.25 for group-two bubbles based on the collected data. Additionally, previously developed drift velocity correlations were applied, and reasonable agreement was demonstrated with the experimental data. The group-one and group-two void fractions were predicted by the developed model with mean relative absolute errors of 37.2 % and 30.6 %, respectively. The two-group drift-flux model is applicable to a wide range of flow conditions, including varying hydraulic diameters and gas-liquid systems, such as air-water and steam-water systems. Due to limited data availability, the asymptotic distribution parameters for group-two bubbles were determined on a preliminary basis for medium-to-large pipes using a linear interpolation method; the parameters ranged from 1.25 to 1.40, for the non-dimensional hydraulic diameters between 18.6 and 40.0. This study demonstrates the effectiveness of the model in predicting two-phase flow parameters in medium-diameter pipes and contributes to expanding the applicability of two-group drift-flux model for engineering applications.