Investigation of liquid-film formation along first wall of laser-fusion reactor

To protect the first wall of a laser-fusion reactor from extremely high energy/particle fluxes, a cascade-type falling liquid-film flow along the first wall has been proposed as one of realistic liquid-wall concept designs. On the cascade-typed liquid-wall concept, the first wall has multistage structure for renewal of starting point of liquid-film flow on it. Both experiments and numerical simulations have been conducted on liquid-film flow along the surface corresponding to the first wall. The experiments, which satisfy the Weber number coincident condition, were carried out using water as the working fluid. Numerical simulations are well simulated on liquid-film behavior observed in flow visualization experiment. Measurement of liquid-film thickness by using a confocal laser scanning microscopy gives information for evaluation on the heat transfer rate. For avoiding increase of vapor concentration in the center region of reactor chamber, saw-shaped wall design is also investigated. The POP (proof-of-principle) experiments and numerical simulations are conducted for the investigation on saw-shaped structure. Both results of experiments and simulations show that it is considerably difficult to cover the small-angle corner entirely with liquid film. Several modified wall surface with smart micro-structure are tested in order to prevent uncovering of the solid wall surface. Such modification has the possibility to cover entire area of the wall surface with liquid film.