Fabrication Of Metal-based Nanosurfaces With Enhanced Evaporation Heat Transfer Properties

Droplet evaporation, as a basic unit of the heat transfer, is widely used in the production processes, such as the thermal control system, cooling systems for nuclear reactors, cooling for the turbine blade, the surfaces of hot metal molds and the low-temperature heat pumps. Therefore, studying the droplet evaporation on hot surfaces and heat-transfer mechanism has important values both for the scientific research and practical application.During the process of the droplet evaporation, heat transfer between the solid phase and liquid phase will occur. The efficient heat transfer can be achieved only when the temperature of heat surface is below the Leidenfrost temperature, because the droplets can stay in boiling region after contact with other droplets. High temperature wettability on the surface of materials will greatly influence the Leidenfrost temperature. Therefore, improving the high temperature wettability on the surface used in heat transfer is one of the important methods of enhancing the droplet evaporation. Besides, the high temperature wettability of the surface is determined by the roughness and chemical composition on the surface of materials.The aim of this paper is to enhance the heat-transfer ability on the surfaces of copper and aluminum, which are modified by the nickel nanocones and alumina nanoporous. Our research is focus on the high-temperature wetting behaviors of water droplets on the surface, while the relationship between high temperature wettability and the nanostructures is studied in detail. Moreover, the evalution of the heat transfer ability of the nano-surface based on metal is given. The study has important significance for understanding the structure-activity relationship between nanostructures and heat transfer properties. Meanwhile, it also provides conditions for the development of new heat transfer nano materials and devices so as to achieve efficient energy utilization.This article main research contents are as follows:(1) The fabrication of nickel nanocones structure based on copper surface and research for the enhanced evaporation heat transfer properties: The nickel nanocones nanostructure have been fabricated on the surfaces of flat Cu by direct electrodeposition. By changing the conditions of electrodeposition, the modulation of the Ni-nanocone structures can be realized. By studying the Leidenfrost temperature and droplet evaporation lifetime on the surface of Ninanocones based on copper, the high-performance wetting performance and heat-transfer ability of water droplets can be obtained. And the stable Cu materials with optimal high-temperature wetting performance and heat-transfer ability can be achieved. In addition, by a simple O2 plasma treatment, the surface wettability of the nanocones based on copper s can be changed, and the high-temperature wetting performance and heat-transfer ability can be further improved.(2) The fabrication of alumina nanoporous structure based on aluminum surface and research for the enhanced evaporation heat transfer properties: Anodic aluminum oxide with nanoholes on the surfaces of aluminum foil can be observed. By changing the parameters of electrochemical reaction, the pore size of nanoholes arrays can be regulated. The hightemperature wetting performance of water droplets and heat-transfer ability can be studied by the Leidenfrost temperature and droplet evaporation experiments on the Al-based nanoholes. Moreover, the regulation of the Leidenfrost temperature can be realized by the structure parameters controlling of nanoholes.