Experimental and Numerical Investigation of Electra KrF Laser Hibachi Foil Cooling with a Near-Wall Planar Jet

Repetitively pulsed operation (5 Hz) of the electra gas laser requires sufficient cooling of the transmission foils, which separate the vacuum diodes from the laser cell and is subject to excessive heat from the attenuation of electron beams. A new method adopting a near-wall, high-speed planar jet was proposed for the protection of the hibachi foil by enhanced convection heat transfer. The jet flows upwards and is parallel to the hibachi foil. Bench-top experiments simulating a single foil span between two neighboring supporting ribs were conducted. Jet velocities and surface heat fluxes were varied. Experimental Nusselt numbers were correlated as dependent on jet Reynolds number and normalized distance from the jet exit. CFD simulations were also performed, where good agreement was observed between the experiments and simulations. The study shows that the planar jet enhances heat transfer from the surface but with decreasing heat transfer coefficients downstream, which indicates that the foil is not cooled uniformly with a single planar jet.