Entrainment and condensation effects in a steam-water shock tube

A steam explosion within a light water nuclear reactor during the course of a severe accident could accelerate an overlying water slug upwards, with the possibility of considerable work potential. This poses as a severe threat to the reactor vessel and the containment. One mitigating factor is the possibility of extensive entrainment of liquid drops from the lower surface of the slug due to nonlinear Taylor instability, which can cause premature breakthrough of the slug and also extensive condensation of hot vapor into the liquid drops. In this work, experiments were run in a vertical glass pipe, in which a water slug was accelerated upwards by breaking a diaphragm above a high pressure driver section containing either steam or nitrogen. From measurements of the pressure history within the driver section and the velocities of the upper and lower interfaces of the liquid column, based on high-speed motion pictures, the acceleration, rate of entrainment, and rate of condensation as functions of time are deduced. Based on the assumption that the droplets have a uniform radius dependent on the Taylor instability's fastest-growing wavelength, an overall heat transfer coefficient is estimated. Substantial reduction in work potential is achieved when condensation effects are present