Experimental research on wetting behavior of refrigerant–oil mixture on micro/nanostructured surface

• Wetting behavior of refrigerant–oil mixture on micro/nanostructured surface was investigated.
• Fluorinated self-assembled monolayer (F-SAM) or micro/nanostructure modified by F-SAM reduces surface wettability.
• Micro/nanostructure increases surface wettability.
• Oil increases wettability of refrigerant on micro/nanostructured surface.
• Oil reduces wettability of refrigerant on micro/nanostructured surface with F-SAM.

The wettability of micro/nanostructured surface is a key property for its application in enhancing the boiling heat transfer of refrigerant–oil mixture. The objective of this research is to experimentally investigate the wetting behavior of refrigerant–oil mixture on micro/nanostructured surface. Three types of surfaces including plain copper surface (PS), micro/nanostructured surface (MNS) and micro/nanostructured surface with fluorinated self-assembled monolayer (MNFS) were fabricated; and the wetting behavior of pure R141b as well as R141b-NM56 mixtures with different oil concentrations on three types of surfaces was measured. The experimental results show that the protuberant liquid film is formed during the wetting of refrigerant–oil mixture on MNS or PS, but does not exist on MNFS; the presence of F-SAM or micro/nanostructure modified by F-SAM reduces the surface wettability, while the presence of micro/nanostructure increases the surface wettability; oil increases the wettability of refrigerant on MNS, while it reduces the wettability of refrigerant on MNFS.