Boiling heat transfer on the micro-nano structured surface fabricated by mechanical sandblasting/alkali-assisted oxidation

Abstract

In order to prepare stable and efficient surfaces to improve boiling heat transfer, the micro-nano structured surface (MNS) was prepared by mechanical sandblasting and alkali-assisted oxidation technique for saturated pool boiling experiment. For comparison purposes, experiments were also carried out on the plain copper surface (PCS), microstructured surface (MS) and nanostructured surface (NS). The results show that the heat transfer performance of different surfaces increases in the order PCS < NS < MS < MNS. Compared with the PCS, the critical heat flux (CHF) of MNS is increased by 55.6%, and the maximum heat transfer coefficient (HTC) is increased by 218%. In addition, the surface properties were characterized and the characterization results explained its excellent boiling performance. The formation of MNS enhances the surface roughness, effective surface area and wettability, thus promoting the supplement of liquid and delaying the occurrence of CHF. It can be seen from the visualization study results that the MNS has more nucleation sites, smaller bubble departure diameter and faster departure frequency. These promising results reveal the potential of micro-nano structured surfaces in various engineering applications.