Application of Bioinspired Superhydrophobic Surfaces in Two-phase Heat Transfer Experiments

Abstract

This paper addresses the potential to use Lotus leaf bioinspired surfaces in applications involving heat transfer with phase change, namely pool boiling and spray impingement. Besides describing the role of bioinspired topographical features, using an innovative technique combining high-speed visualization and time-resolved infrared thermography, surface durability is also addressed. Water is used for pool boiling and for spray impingement systems (simplified as single droplet impact), while HFE7000 is used in a pool boiling cooler for electronic components. Results show that surface durability is quickly compromised for water pool boiling applications, as the chemical treatment does not withstand high temperatures (T > 100 °C) during long time intervals (3 h – 4 h). For HFE7000 pool boiling (depicting lower saturation temperature − 34 °C), heat transfer enhancement is governed by the topography. The regular hierarchical pattern of the bioinspired surfaces promotes the heat transfer coefficient to increase up to 22.2%, when compared to smooth surfaces, while allowing good control of the interaction mechanisms until a distance between micro-structures of 300 μm – 400 μm. Droplet impingement was studied for surface temperatures ranging between 60 °C – 100 °C. The results do not support the use of superhydrophobic surfaces for cooling applications, but reveal great potential for other applications involving droplet impact on heated surfaces (e.g. metallurgy industry).