Condensation heat transfer on slippery lubricant-impregnated nanohole-arrayed stainless-steel surface

Abstract

The condensation heat transfer performance of lubricant-impregnated surfaces has a competitive advantage owing to the improved mobility of droplets and self-healing characteristics. In this study, we fabricated the lubricant-impregnated surfaces featured with Teflon-coated anodized nanoporous oxide layer on stainless steel infused with Krytox GPL103 oil. The characterization shows that the droplet state on the surface changes from the pinning to slippery states (sliding angle α of 1.8 ± 0.3°) enabled by the presence of the lubricant oil. The condensation heat transfer performances of the lubricant-impregnated Teflon-coated anodized stainless-steel surface (L-T-AS) are investigated from the aspects of the surface wettability and droplet mobility, compared to that of Teflon-coated stainless-steel surface (T-S) and Teflon-coated anodized stainless-steel surface (T-AS). Whereas coalescence-induced droplet shedding and droplet sweeping are found on the T-S and T-AS, the shedding of discrete droplets and their sweeping without further coalescence are noticed on the L-T-AS. The heat transfer coefficient of the L-T-AS is 398.4% higher than that of the T-AS at the low subcooling temperature of 0.2 K. The heat transfer performance of the dropwise condensation of the L-T-AS has further been elucidated by the theoretical model considering the heat transfer rate through a single droplet associated with the density distribution function of the droplet.