Abstract
Functionalized interfaces enhancing phase-change processes have immense applicability in thermal management. Here, a methodology for fabrication of surfaces enabling extreme boiling heat transfer performance is demonstrated, combining direct nanosecond laser texturing and chemical vapor deposition of a hydrophobic fluorinated silane. Multiple strategies of laser texturing are explored on aluminum with subsequent nanoscale hydrophobization. Both superhydrophilic and superhydrophobic surfaces with laser-engineered microcavities exhibit significant enhancement of the pool boiling heat transfer. Surfaces with superhydrophobic microcavities allow for enhancements of a heat transfer coefficient of over 500%. Larger microcavities with a mean diameter of 4.2 μm, achieved using equidistant laser scanning separation, induce an early transition into the favorable nucleate boiling regime, while smaller microcavities with a mean diameter of 2.8 μm, achieved using variable separation, provide superior performance at high heat fluxes. The enhanced boiling performance confirms that the Wenzel wetting regime is possible during boiling on apparently superhydrophobic surfaces. A notable critical heat flux enhancement is demonstrated on superhydrophobic surfaces with an engineered microstructure showing definitively the importance and concomitant effect of both the surface wettability and topography for enhanced boiling. The fast, low-cost, and repeatable fabrication process has great potential for advanced thermal management applications.
Highlights
Emergence of new information technologies including artificial intelligence, internet of things, and big data requires a powerful computer infrastructure, which is a major consumer of electricity and is projected to grow at a rate of 10% per year.[1]
This study presents a low-cost, fast, and reliable method of producing superhydrophobic aluminum surfaces for extreme pool boiling performance by combining laser surface functionalization with chemical vapor deposition (CVD) of a hydrophobic fluorinated silane
We convincingly show that superhydrophobic surfaces, which allow the establishment of the Wenzel wetting regime and have an appropriate microstructure, can increase the critical heat flux (CHF), which contradicts the current understanding of boiling heat transfer performance on poorly wettable surfaces
Summary
Emergence of new information technologies including artificial intelligence, internet of things, and big data requires a powerful computer infrastructure, which is a major consumer of electricity and is projected to grow at a rate of 10% per year.[1]. Several methods for micro- and nanotexturing of the boiling surface have been shown to enhance boiling heat transfer,[19,20] yet few of these methods are truly scalable and straightforward while still offering great boiling enhancements.[21−23] lies the advantage of laser texturing, which can be utilized to modify the micro- and nanostructure of the surface, its chemical composition, and morphology,[24,25] all of which significantly affect boiling heat transfer To this effect, Kruse et al.[26] produced multiscale structures on stainless steel using a femtosecond laser, while Nirgude and Sahu[27] applied nanosecond laser texturing to functionalize copper surfaces. The developed surfaces provide sacrifice-free boiling performance enhancement and offer both increased cooling system safety and highly efficient cooling with heat transfer coefficients in an excess of 200 kW m−2 K−1
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