Scalable and Resilient Etched Metallic Micro- and Nanostructured Surfaces for Enhanced Flow Boiling

Abstract

Flow boiling and evaporation in tubes and channels occur in a wide variety of energy systems, such as refrigeration, air conditioning, power generation, electronics cooling, distillation, and purification. In this work, we demonstrate remarkably increased heat transfer coefficients of 270% during refrigerant flow boiling in scalable microstructured (∼40 μm), industrial-scale (∼1 m long) aluminum (Al) tubes, when compared to smooth unstructured Al tubes. To achieve scalable nanomanufacturing, we create highly conformal and durable structured surfaces by relying on hydrochloric acid Al etching. Flow boiling tests were conducted in 6.35 mm diameter Al tubes using R134a refrigerant as the working fluid. To benchmark our approach and to elucidate the effect of the structure length scale, we also fabricated ultrascalable boehmite (AlO­(OH)) nanostructured (∼300 nm) Al tubes, showing that etched microscale features are necessary and key to enhancement. Durability tests conducted using a 28 day long continual flow boiling experiment demonstrated negligible degradation of the etched surfaces. The scalable and cost-effective techniques used to create these durable, etched-Al microstructures may significantly reduce manufacturing cost when contrasted with current enhancement approaches such as extrusion, drawing, and welding.

Superbiphilic Laser‐Microengineered Surfaces with A Self‐Assembled Monolayer Coating for Exceptional Boiling Performance

“…Although boiling heat transfer is one of the most intense heat transfer mechanisms, researchers in this field have extensively investigated numerous types of methods in the last few decades [8,9] to further improve the boiling performance. Studies range from enhancements based on boiling fluid modification, [9,10] such as with the addition of nanoparticles (i.e., nanofluids) [11,12] or with mixtures of different surface tensions, [13,14] to studies focusing on surface modification, [15,16] with an emphasis on changing the surface topography [17,18] and morphology [19,20] alongside with its wetting behavior. [21,22] In recent years, various technologies have been explored to tailor the surface topography and morphology to improve boiling performance.…”

Scalable Slippery Omniphobic Covalently Attached Liquid Coatings for Flow Fouling Reduction

“…Dip coating enables internal coating of tube samples and hence enabled flow fouling experiments. This different application method is a step forward from a lab-scale fabrication technique toward a real-world application method. − Second, the developed coating has a lower surface roughness ( R q ≈ 0.9 nm) when compared to electrophoretically deposited SiO 2 coatings ( R q ≈ 50 nm). Surface roughness greatly influences the surface nucleation site density that governs the nucleation rate of the foulant …”

Advances in micro and nanoengineered surfaces for enhancing boiling and condensation heat transfer: a review

“…Recently, microstructured aluminum surfaces demonstrating up to 270% enhancement have displayed good preliminary durability with the structured surface displaying negligible variation in heat transfer/SEM studies after 28 days. 187 Overall, more work needs to be done in this regard with long term durability tests focused on variation of operating parameters and channel sizes.…”