Study of Inertia and Compressibility Effects on the Density Wave Oscillations of Two-Phase Boiling Flows in Parallel Channels

In this research, a theoretical model is presented to investigate the density wave oscillations (DWOs), in two horizontal parallel channels with lumped parameter model based on two phase homogeneous hypothesis. The parallel channel is composed of the entrance section, heating section and outlet section and the model consists of the boiling channel model, pressure drop model, parallel channel model, constructive model and inertia and compressibility effects, while subcooled boiling effect is neglected and the governing equations are solved by Gear method. The model is validated with experimental data of a single channel flow instability experiment. Then the flow instability in twin channel system is studied under different conditions. This model can analyze the effects of external parameters, such as fluid inertia and compressible gases on the stability margins of density wave oscillations. The results show that, the fluid inertia and compressible gases can significantly change the stability margins of two parallel channels; in fact, the stability behavior of two parallel channel system improves with increasing the inlet inertia and outlet compressibility but, increasing the outlet inertia and inlet compressibility have negative effects the system stability.