THE EFFECT OF A FLAT-PLATE-TYPE OBSTACLE ON A THIN LIQUID FILM FLOW

Detailed visual observations and measurements of local film thickness, axial distributions of static pressure and gas velocity along a flat-plate-type flow obstacle (with and without a projection used as a simulation of a grid type spacer in a nuclear reactor) were conducted with special attention to drypatch formation, or liquid film breakdown. The effect of the inclination of the test section or gravity was also investigated. The results made it clear that, the flat-plate itself did not promote drypatch formation but the projection had a strong effect, even in the case where the projection is in contact with the surface at only one point. In general, the drypatch occurred just in front of the projection in a wide range of both air and water flow rates in an inclined duct because the gravitational force acts to remove water downward as does the action of the horse shoe vortex formed stationary just in front of the projection.