Research of two-phase flow instability in parallel narrow multi-channel system

Two-phase flow instabilities have been highly researched in the past decades. Many researches gave different stability criterions based on experiments or calculations. However, most of the experiments were designed for studying the specific type of instability, but sometimes what we want to know is the stabilities of one specific system. In this paper, a comprehensive study of two-phase flow instabilities in parallel narrow multi-channel system was done by RELAP5/Mod3.4 code. Firstly, a direct comparison was made of the stability boundaries obtained by experimental data and RELAP5/Mod3.4 code to verify the accuracy of RELAP5 code. Good agreement between the experimental and code prediction results was achieved. Then, the two-phase flow instabilities of parallel narrow multi-channel system were investigated in sequence. The in-phase and out-of-phase parallel channel instabilities (PCI), the Ledinegg instability and the out-of-phase density wave instability (DWI) induced by Ledinegg instability in parallel narrow multi-channel system had been investigated respectively. The effects of system parameters on the stability characteristics were also explored. It is found that the instability analysis of parallel narrow multi-channel system should include the above mentioned four types, which can constitute a complete picture of a system’s instability.

► The instabilities of parallel multi-channel system were studied systematically.
► The instabilities in single channel will also be induced in multi-channel.
► Flow excursion should be paid more attention in multi-channel system.
► The instability boundaries should include in-phase and out-of-phase DWIs.