Phenomenological modeling of two-phase flow in water reactor at ANL (inverted annular flow modeling)

In predicting two-phase flow phenomena in nuclear reactors under various accident conditions, the interfacial transfer terms are among the most essential factors in the modeling. The interfacial geometry and thermo-hydraulics at the interface often dominate these two-phase flow phenomena. Among the various two-phase flow regimes, the inverted annular flow is relatively less well understood due to its special heat transfer conditions. However, this regime is quite important in terms of LWR accident analyses, since the peak cladding temperature often strongly depends on the thermo-hydraulics in this inverted annular flow and subsequent droplet dispersed flow. In view of this, the inverted annular flow transfer mechanisms and the flow regime transitions are studied in detail