A Mechanistic Model for Countercurrent Steam-Water Flow

Abstract

A one-dimensional model has been developed to describe the flow behavior of a liquid film draining down a heated wall, in the presence of countercurrent vapor flow. The effects of nonequilibrium void generation at the walls and condensation of countercurrent vapor on the penetrating liquid film interface, as well as on the bypassed liquid, have been considered. The momentum exchange is described by a correlation, assumed to apply at the entrance region, where the amount of liquid film flow is limited by the net vapor upflow. Theoretical predictions were compared with over 600 test results, obtained in 1/15- and 2/15-scale models of a PWR downcomer, over a wide range of test parameters. The comparisons exhibit a fairly good agreement.