ANALYSIS OF TWO-PHASE FLOW INSTABILITY FOR STEAM GENERATOR

摘要

Two-phase flow instability is an important problem that affects the running of steam generators in nuclear reactor systems. In this paper, two-phase flow instability in parallel channels of a steam generator are analyzed to disclose the mechanism of flow instability by using the frequency domain method. The mathematical expressions of heat transfer and flow for a steam generator are proposed，and the transfer function of the closed-loop system is deduced by using linearization and Laplace transfer. The steam generator's stability is judged according to Nyquist stability criterion. Depending on this fundamental principal，the computer code is developed to analyze the stability of steam generators. The results displayed two conclusions; firstly, the increase of inlet orifices or mass flow rate enhances the stability of generator steam; secondly, the coupling interactions between channels and their external loop effects on the stability of generator steam are not ignored. The result show that the effects are non-monotonic on the stability of generator steam.