Study of Inertia Effects on Density Wave Oscillations in Two-Phase Systems

Abstract

Thermal-hydraulic instabilities and oscillations are unwanted effects which can result in severe damages of two phase flow systems. The most common dynamic two-phase flow instability, namely density wave oscillations, is studied. The stability influence of external parameters such as the inertia of the subcooled liquid before the heated channel and the inertia of the fluid after the heated channel are analyzed. Nondimensional stability maps, as a function of the subcooling and the phase-change numbers are constructed. The influence of the inertia components on the stability boundaries is studied and characterized. The study is performed by modeling a single boiling channel using a homogeneous model. A compressible transient model describes the evolution of the flow and pressure in the non-heated regions. Finally the problem is solved using a high-order method, allowing to describe the involved phenomena with high accuracy and avoiding the numerical diffusivity, characteristic of low order methods. The implementation of wavelet decomposition in the analysis of the imulation results is also described.