Flooding Experiments with Steam/Water and Air/Water at Elevated Pressure in a Large Diameter Vertical Tube

Abstract

An experimental investigation to acquire flooding data using steam/water and air/water fluid pairs at elevated pressures was conducted. This research provides the first flooding data above atmospheric pressure in large diameter vertical tubes and can be used to improve the flooding models in one-dimensional system codes. A stainless steel test section consisting of a 3-inch inner diameter tube was modified to permit flooding experiments up to 60 psia for air/water experiments at 25 ◦C and 30 psia for steam/water experiments at near saturated conditions. Extensive modifications were made to the test facility to allow for high pressure testing, including the addition of a large compressed air supply, two plate type heat exchangers, and extensive instrumentation. The air/water and steam/water flow paths are nearly identical, yielding a test facility capable of providing data that can be directly compared while avoiding influences from complicated geometry effects.

The data at higher pressures suggest that the momentum transfer necessary for the onset of flooding is achievable for lower superficial velocities as the gas density increases. Flooding characteristics are presented in terms of the Kutateladze number, and the effect of fluid properties on flooding, such as density and surface tension, are discussed. If condensation is accounted for, the saturated steam/water data at 30 psia closely trends with the air/water flooding data. This research provides fundamental data that can be used to address the pressure scaling deficiencies in flooding correlations for reactor safety codes and also evaluate the applicability of air/water data for steam/water applications.