Influence of the copper and steel surfaces' roughness on surface energy and wettability
This article aims at solving the fundamental problem of thermal physics. This problem includes controlling small volumes of liquids on the heat exchange surfaces of special devices (for example, thermosyphons and heat pipes) working in a closed evaporative-condensation cycle. The authors analyze the effect of roughness on surface energy and wettability of different textures on typical heat exchange surfaces made of copper and steel prepared for operation by mechanical (abrasive) processing. Six textures were created on the copper and steel surfaces using a grinding and polishing machine. The roughness of the textures was evaluated based on the analysis of three-dimensional roughness characteristics (amplitude and hybrid). The surface wettability was studied on the experimental setup with the shadow method. The surface free energy of abrasively processed surfaces was determined by the Owens-Wendt-Rabel-Kaelble method. The results show the necessity of using at least one three-dimensional amplitude and hybrid characteristics to evaluate the textures. The authors have determined the conditions for the formation of Gaussian and sinusoidal textures. A significant increase in surface area is achieved when copper and steel are processed with the abrasive discs with an average grit size of up to 100 μm. This increase is up to 7% for copper and up to 2.7%. After abrasive processing of copper and steel surfaces, the proportion of the polar component in their total surface energy changes. This is a consequence of changes in dipole interactions and hydrogen bonds between atoms.