Simulation of the Hydraulic Behaviour of TwoPhase Flows in Blocked Subchannels

Abstract

Tests have been carried out in two interconnected vertical channels with one of them being blocked. An air-water mixture at 20 degrees C was used as the working fluid. For blockages of different shapes and severities, the following flow variables have been measured: the axial void fraction distribution, the liquid mass exchange between the channels, the gas mass transfer between the channels, the axial pressure distribution in both channels, and the radial pressure differences between the channels. Using the time integral of the local instantaneous conservation laws as the starting point, a sub- channel model has been developed. The assumption of an ergodic stationary process has made possible further spatial integration of the resulting equations. The SIMPLER algorithm is adapted for the numerical solution. An adequate blockage model assures an overall momentum balance over the discretized cell elements. Comparison of the predictions of the proposed model with the experimental data confirms that it is capable of handling blockages of up to 90% of the flow area under single and two-phase flow conditions. For now, this model only accounts for the hydrodynamic aspect of vertical adiabatic flows.