Rationally 3D-Textured Copper Surfaces for Laplace Pressure Imbalance-Induced Enhancement in Dropwise Condensation

Abstract

Enhancing the thermal efficiency of a broad range of condenser devices requires means of achieving sustainable dropwise condensation on metallic surfaces, where heat transfer can be further enhanced, by harvesting the advantage of the sweeping action of vapor flow over the surface, facilitating a reduction in the droplet departure diameter. Here, we present a rationally driven, hierarchical texturing process of copper surfaces, guided by fundamental principles of wettability and coalescence, which achieves controlled droplet departure under vapor flow conditions and thus significantly enhances phase change thermal transport. The desired texture is attained by fabricating an array of 3D laser-structured truncated microcones on the surface, covered with papillae-like nanostructures and a hydrolytically stable, low surface energy self-assembled-monolayer coating. Passive droplet departure on this surface is achieved through progressive coalescence of droplets arising from microcavities formed by the microcone array, resulting in depinning and subsequent departure of the depinned condensate drops through vapor shear. The synergistic combination of vapor shear and the sustained dropwise condensation on the hierarchical copper surface results in a nearly 700% increase in heat transfer coefficients as compared to filmwise condensation from identical, standard unstructured surfaces.

Evolution of microstructures on stainless steel induced by ultra-short pulsed laser ablation

“…Microstructures are not necessarily an unwanted side effect, but can be used to alter the physical interplay at the surface of different materials. Well-known examples are the change in wettability [32,33], optical [34] and, recently, tribological properties [35][36][37]. The use of laser induced structures for tribology strongly depends on the envisioned application and lubrication condition.…”

Is dropwise condensation feasible? A review on surface modifications for continuous dropwise condensation and a profitability analysis

“…The focus will be on heat transfer investigations on smooth and structured surfaces with gravity-induced droplet shedding, as they comprise the most established literature. Comprehensive studies of the relevant literature on biphilic [28], [29], [30], [31], [32] or lubricant-infused surfaces [26], [27], [33], enhanced droplet shedding by droplet jumping [34], [35], [36] or by a Laplace pressure gradient [29], [37], [38], [39], and the influence of increased vapor velocities [38], [40] are beyond the scope of this review.…”

Hydrodynamics and mechanism of hydrophobic foam column tray: Contact angle hysteresis effect

“…Many emerging studies have emphasized the interfacial wettability effects on multiphase transport processes. Specifically, interfacial wettability effects have been investigated in terms of fluid dynamics (drag reduction and wet particle collision), hydrodynamics (membrane bubbling and sieve tray), heat transfer and anti‐icing, oil recovery, oil–water separation, micro‐reactor technology, and so forth.…”