Simulation of the Flow Regime Stability of Natural-circulating Two-phase System

摘要

The cryogenic flow regime in a downcomer of reservoir can change from single-phase natural convection to natural-circulating two-phase flow because of heat leakage to the downcomer. It leads to a periodic sequence of vapor-bubble buoyancy, agglomeration and condensation. Numerical simulation of flow regime evolution is present to obtain temporal and spatial distribution of void fraction in a period, together with the transitional condition between bubble flow and slug flow. The result, which can be proved by experiments, is expected to predict and estimate the instability of flow regime.