Hydrodynamic stability of the porous wetted wall protection schemes in IFE reactors

A numerical investigation has been conducted to analyze the fluid dynamic aspects of the porous wetted wall protection scheme for IFE reactor first walls. The transient three-dimensional conservation equations, together with a level contour reconstruction method, have been used to track the three-dimensional evolution of the liquid film surface on a porous downward facing wall with different liquid injection velocities. Parametric calculations have been performed to develop generalized non-dimensional charts for the droplet detachment time, detached droplet equivalent diameter, and minimum film thickness during the transient as a function of the relevant liquid properties, and the various design and operating parameters. The effects of initial film thickness, liquid injection velocity through the porous wall, surface disturbance amplitude and configuration, disturbance mode number, and surface inclination angle have been examined. The results suggest that, when applied to the downward facing upper half of the reactor cavity, liquid film stability may impose a limit on the minimum repetition rate in order to avoid liquid ‘dripping’ into the reactor cavity between shots. The results also suggest that a minimum injection velocity is required in order to maintain the film thickness over the entire surface above a specified minimum value. The generalized charts obtained in this investigation make it possible to establish ‘design windows’ for successful implementation of the wetted wall protection scheme with various coolants and operating conditions.