Dividing annular/two-phase flow in horizontal T-junctions

Abstract

<p>The results of an experimental and analytical investigation of the separation phenomenon in dividing annular two-phase flow is presented. Detailed experiments have been carried out with a steam-water loop to isolate the effects of flow split, inlet quality, inlet mass flux and branch diameter on the phase and pressure distribution characteristics in horizontal T-junctions. Through the set of measurements made in the experimental program, the phase separation and pressure distribution characteristics were shown to be strongly interdependent. Based on these measurements, a physical model describing the phase separation mechanism is presented. This physical model is then developed mathematically. A model to predict the dividing flow characteristics for annular flow in a T-junction is proposed consisting of mixture and vapor 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. In the development of the branch model, a new equivalent inlet density for the branching flow ($\rho\sbsp{1}{*}$) and a two-phase multiplier ($\Phi\sp*$) are defined. 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 degree of phase redistribution 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.</p>