On the development of a model for predicting phase separation phenomena in dividing two-phase flow

A model to predict the dividing flow characteristics for annular flow in a T-junction is proposed consisting of mixture and vapour phase continuity equations, two pressure change correlations and a closure relationship. The pressure change from the inlet through the run of the T is modelled by way of a balance of axial momentum at the junction based on a separated flow assumption. The branch pressure change is modelled using a balance of mechanical energy for the branching flow consisting of reversible and irreversible components. The closure relationship links the phase separation characteristics with the junction pressure changes. It involves a balance between pressure and inertia forces within the junction volume defining a dividing surface for each phase between the run and branch flows. The branch quality is then determined using a well-defined inlet flow distribution. The model is capable of predicting the experimentally observed phase separation characteristics from three independent studies of annular/steam—water and air-water flow in dividing T-junctions.