Current Intergroup mass transfer limitations in the multi-group two-fluid model

This work investigates the intergroup mass transfer term in the multi-group two-fluid model with interfacial area transfer equation. In the two-fluid model, the intergroup mass transfer term is relied upon for bubble accounting between bubble groups. Its role in the gas-phase continuity equations makes it of vital importance for accurate prediction of two-phase flow. Past intergroup mass transfer modeling is reviewed, highlighting the limited applicability to phase change flows due to the closure need of the intergroup mass transfer coefficient. The analysis explores the difficulty presented by the intergroup mass transfer coefficient. The dependence of the intergroup mass transfer coefficient on the bubble number density distribution is studied to provide limiting conditions of its applicability. A new empirical bubble size distribution method is developed, employing distribution functions such as Nukiyam-Tanasawa and Ronsin-Rammler distribution. Experimental data in flows with phase-change are used to develop a new correlation of the intergroup mass transfer coefficient. The result shows that the new intergroup mass transfer coefficient is promising for use over a wide range of practical two-phase flows.