Experimental investigation on wettability of refrigerants on laser-ablated surfaces

Abstract

Due to the refrigerant's low surface tension, it is difficult to increase its static contact angle (SCA) on the surface. Existing studies all employed the method of low surface energy coating to increase the SCA of the refrigerant on the surface, but this method has the drawback of coating peeling. In this study, the SCAs of R134a and R1234ze(E) refrigerants on the surface were increased using a simple and reliable laser surface texturing technique. The results showed that the SCAs of R134a and R1234ze(E) on the polished surface were 6.2° and 6.4°, respectively, indicating that the surface was superhydrophilic. Immediately after laser ablation, the surface hydrophilicity was improved with SCA approaching 1° due to the increase in surface roughness and the oxidation effect of the surface. However, over time, the laser-ablated surface adsorbed substances containing hydrophobic C-C(H) groups, resulting in a gradual increase in SCA. The steady-state SCAs of R134a and R1234ze(E) on the laser-ablated surface were 12.2° and 12.7°, respectively, which were about twice the SCAs of the refrigerants on the polished surface. In terms of the increased percentage of SCA, the laser surface texturing technique is effective in increasing the hydrophobicity of the refrigerant on the surface.