Superhierarchically rough films are rapidly synthesised on metal substrates via electrochemically triggered self-assembly of meso/macroporous-structured metal-organic framework (MOF) crystals. These coatings are applied to immobilise a functional oil with low surface energy to provide stable coatings repellent to a wide range of hydrophobic as well as hydrophilic fluids. Such omniphobic surfaces are highly interesting for several applications such as anti-fouling, anti-icing, and dropwise condensation, and become easily scalable with the presented bottom-up fabrication approach. As investigated by environmental scanning electron microscopy (ESEM), the presented perfluorinated oil-infused Cu-BTC coating constitutes of a flat liquid-covered surface with protruding edges of octahedral superstructured MOF crystals. Water and non-polar diiodomethane droplets form considerably high contact angles and even low-surface-tension fluids, e.g. acetone, form droplets on the infused coating. The repellent properties towards the test fluids do not change upon extended water spraying in contrast to oil-infused porous copper oxide or native copper surfaces. It is discussed in detail, how the presented electrodeposited MOF films grow and provide a proficient surface morphology to stabilise the functional oil film due to hemiwicking.

Dedicated to Professor Rüdiger Lange on the occasion of his 65th birthdayCompared to filmwise condensation on conventional condenser surfaces, heat transfer can be significantly enhanced by tuning the wettability of the surface to promote dropwise condensation. Following rapid advances in surface engineering, the last years have seen an unprecedented interest in dropwise condensation research. This brief review highlights recent advances in theory and experimental investigation regarding dropwise condensation on smooth hydrophobic surfaces, micro-and nanostructured superhydrophobic surfaces, biphilic surfaces with patterned wettability, and lubricant-infused surfaces.

It is well known that dropwise condensation corresponds to a high heat transfer coefficient. The high performance enhancement of dropwise condensation in comparison to filmwise condensation is attributed to the ability of non-wetting droplets to be shed from the surface by gravity, therefore reducing the overall thermal resistance. The common treatments to carry out the hydrophobic surface for dropwise condensation are coating and structure. The improvement of heat transfer efficiency by combination of surface treatments with coating and groove structure has been proved compared of surface with single surface treatment by coating or groove structure. Based on this result, in this study presents a model developed to predict the heat transfer efficiency of dropwise condensation for surface with coating and groove structure features. The model is established by heat transfer though a single droplet with the drop size distribution. The heat transfer of single drop is not only analyzed as combination of thermal resistances, but also considered capillary effect of droplet due to groove geometry and properties of surface. In addition, the model results are validated with experimental data which is investigated by varied modification of vapor side metallic surface properties at low absolute pressure. It can be a reference to design industrial condensers of heat exchangers in the future. Further to optimize the surface properties and improve the higher heat transfer performance of dropwise condensation

Metallische Werkstoffe weisen bei hohen Temperaturen und chemisch aggressiven Atmosphären geringe Standzeiten auf. Eine Alternative sind keramische Werkstoffe, die jedoch nicht wie metallische Werkstoffe verarbeitet werden können. Deshalb wird der Einsatz einer einfachen Wärmerohrgeometrie als Grundform für Wärmeübertragungssysteme in der Hochtemperaturtechnik betrachtet. Zur Auslegung von Hochtemperaturwärmeübertragern wird ein numerisches Berechnungsmodell zur genauen Bestimmung des Betriebsverhaltens großer Apparate vorgestellt, das neben konvektivem auch den strahlungsabhängigen Wärmetransport berücksichtigt.

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