Flashing Two-Phase Releases from the Desert Tortoise and Jack Rabbit Tests

There has been a great deal of discussion over several years about the predicted release rate and source conditions for a flashing two-phase release from pressurized storage of a liquid above its boiling point (of particular importance are ammonia and chlorine). The Desert Tortoise tests were designed to release ammonia from pressurized storage with sufficient overpressure to deliver a subcooled ammonia stream to the release point through a long pipe. However, it was evident that the mass release rates were not as high as expected. This experience was used to guide the design of the release mechanism used in the Jack Rabbit tests (which release pressurized ammonia and chlorine). Despite these efforts, visual observations indicated that flashing flow occurred inside the vessel in the Jack Rabbit tests for both ammonia and chlorine. This paper discusses one approach to describing the flow under these conditions and makes the argument that releases from large openings will result in flashing flow inside the vessel. These effects are important for the downwind transport and diffusion of material because flashing inside the vessel results in larger fluid velocities outside the vessel when compared with a liquid only discharge, and these higher velocities result in more initial air dilution due to jetting.