Opportunities in Nano-Engineered Surface Designs for Enhanced Condensation Heat and Mass Transfer

Abstract

Recent advancements in surface nanoengineering have spurred intense interests in their implementation for enhancing condensation heat transfer. When appropriately designed, nanoengineered surfaces not only lead to highly efficient transport mechanisms not achievable with conventional dropwise condensation, they also demonstrate the possibility of augmenting condensation of low surface tension fluids widely used in industry. These advantages are further enhanced by the development of highly scalable nanofabrication methods, which enable the potential transition from laboratory-scale prototypes to real-world industrial applications. In this review, we discuss the progress, opportunities, and challenges of enhancing condensation heat and mass transfer with nanoengineered surfaces. This article provides an overview of the recent developments in micro/nanoscale coating and structure fabrication techniques and performs a thorough comparison of their condensation performance, elucidating the complex interfacial transport mechanism involved. Surface structuring methods that are durable, scalable and low-cost are essential attributes for large-scale industrial implementation. Here, the methods used to improve surface durability and demonstrations of nanostructure-enhanced meter-scale condensers are presented. Limitations are discussed and the potential techniques to overcome these challenges are summarized. Given the recent development of metal additive manufacturing technology and its growing relevance in manufacturing processes, we end this review by providing our perspectives on the opportunities in enabling surface nanostructuring of metal additive manufactured materials and the potential of nanometric-millimetric co-design optimization for the development of next-generation additively manufactured condensers.

Ultrascalable Surface Structuring Strategy of Metal Additively Manufactured Materials for Enhanced Condensation

“…Despite more than a decade of intensive research, enabling jumping droplet condensation on aluminum materials in pure vapor and high supersaturation conditions remains challenging and has not been demonstrated. [ 50 ] To the best of our knowledge, our work represents the first demonstration of sustainable jumping droplet condensation in pure vapor, high supersaturation conditions on aluminum materials, which is only achievable using our AM surface structuring method. Consequently, highly efficient thermal devices may no longer be limited to heavy and expensive copper alloys as nanostructured aluminum alloys can now cater for lightweight applications for industries including aviation and aeronautics, automotive, electronics packaging, and electric and unmanned aerial vehicles.…”

Robust and durable liquid-repellent surfaces

“…159,183,311,312 Meanwhile, condensation-induced blisters through nanoscale pinholes on the hydrophobic thin coatings will result in the delamination of the coatings if the condensed droplets cannot overcome the Laplace pressure barrier generated by the pinned three-phase contact line at the pinhole, which finally develop into the failure of liquid repellence. [313][314][315] Another frequently-meet and significant situation for the wetting model transition is immersing the surface in the repelled liquid (either static or flowing), where a gradual disappearance of the cushion is observed (Fig. 19e), and this generally results from liquid static pressure, air diffusion driven by chemical potential gradient, and/or shear stress induced deformation/detachment of the air bubbles.…”

“…In addition, chemical degradations of the hydrophobic coatings of super liquid-repellent surfaces during water vapor condensation have also drawn much attention in recent years. 315,[396][397][398][399] For example, Wang et al studied the condensation-induced chemical degradation and failure of organofunctional silane (including trichloro(octadecyl)silane and trichloro (1H,1H,2H,2H-perfluorooctyl)silane) self-assembled monolayer coatings on Si/SiO 2 substrate. 399 The authors found that silane-uncoated defects within the coatings were generated during the synthesis of the coatings in uncontrolled environments with unregulated water/ moisture content, and these defects favored the condensed water to dissolve and hydrolyze the Si-O-Si bonds at the coating-solid interface, leading to partial detachment of the cross-linked silane agglomerates from the surface, which thereby acted as nucleation sites for degradation of the silane functionalized liquid-repellent coating.…”

Tunable and Robust Nanostructuring for Multifunctional Metal Additively Manufactured Interfaces

“…20−23 However, the development of a facile method that is cost-effective, highly scalable, and applicable to arbitrary shapes remains a challenge. 24 This challenge is further exacerbated by the growth of metal AM as a viable manufacturing technique. AM has the capability of fabricating complex, light, and innovative designs.…”

“…Previous efforts to tune structure designs have shown promise for optimizing the performance of conventionally used manufacturing materials in reducing droplet–surface contact time, − minimizing adhesion, , and having antiflooding performance. − However, the development of a facile method that is cost-effective, highly scalable, and applicable to arbitrary shapes remains a challenge . This challenge is further exacerbated by the growth of metal AM as a viable manufacturing technique.…”