Research on two-phase flow instability in parallel rectangular channels

In the present work, a theoretical model for Density Wave Oscillations flow instability in parallel rectangular channels is built with a lumped mathematical model based on homogenous hypothesis. The parallel channel comprises the entrance section, heating section and riser section and the model consists of the boiling channel model, pressure drop model, parallel channel model and constructive model, while sub-cooled boiling effect is neglected and the final nonlinear ordinary differential equations are solved by Gear method. The model is validated with experimental data of a single channel with constant pressure drop and that of a twin-channel flow instability experiment. Then the flow instability in twin rectangular channel system is studied under different conditions. The effects of pressure, P, inlet throttling coefficient, k(in), and exit throttling coefficient, k(out) are examined through the parameter plane of the subcooling number, N-sub and phase change number, N-pch and the frequency of the oscillations, f. Finally, the effects of asymmetric heating and throttling on flow instability are also analyzed. (C) 2013 Elsevier Ltd. All rights reserved.