THERMO-HYDRAULIC BEHAVIOR OF INVERTED ANNULAR FLOW (EFFECTS OF FLOW DIRECTION AND CHANNEL DIAMETER)

Inverted, annular flow has been Investigated experimentally in a vertical channel and in horizontal channels, with three different diameters under various heated wall temperature, inlet subcooling and inlet velocity conditions, using Freon 113 as a test fluid. This enables clarification of flow direction and flow channel diameter effects on the thermo-hydraulic behavior, and offers a data base for clues to the modeling of the thermo-hydraulics of two-phase flow in a thermal non-equilibrium state. The effects of flow direction and channel diameter on wall heat transfer coefficient and vapor film thickness are also shown. Furthermore,the relationship between wall shear stress and vapor film thickness is specified. The wall shear stress in inverted annular flow for a smooth interface between vapor film and liquid core jet is less than that in liquid single-phase flow, but becomes larger when significant waves develop.