Critical heat flux in pool boiling on femtosecond laser-irradiated copper powder-sintered surfaces

Abstract

This study aims to create a surface with a porous microgroove structure by simultaneously employing copper powder sintering and femtosecond (FS) laser processing in order to enhance critical heat flux (CHF). A total of eight distinct porous microgroove surfaces were fabricated under various FS-laser processing conditions. These surfaces underwent comprehensive analysis, including an examination of the surface morphology, surface wettability, and wicking capability. Under near-CHF condition, where the supplied heat flux reaches 90% of CHF, the movement of bubbles was observed using a high-speed camera. This observation revealed the formation of a thin microbubble layer on the porous microgroove surface, effectively retarding the generation of a vapor blanket. Furthermore, the wicking volume flux was measured for each specimen, indicating an efficient replenishment of the working fluid to the boiling surface. Importantly, the newly proposed surface exhibited a higher volume flux, compared with both the porous and microgroove surfaces. A direct relationship was observed between the experimentally determined CHF and wicking volume flux.