Influence of refrigerant solubility and surface geometry on the wetting properties of lubricating oil

• Basic geometry is an oil film strained between two vertically aligned surfaces.
• Wetting was quantified in terms of the half-filling and apparent contact angles.
• R-134a/POE ISO 10 oil mixtures were used in all tests (carbon steel surfaces).
• Diameters of the spheres and the spacing between them were evaluated.
• Surface curvature and solubility were found to influence the wetting parameters.

Experimental results are reported on the effect of refrigerant solubility on the wetting parameters (apparent contact angle and half-filling angle) of POE ISO 10 lubricating oil on carbon steel surfaces. The basic geometric configuration of the test section consisted of an oil film strained between two vertically aligned spheres. An ancillary configuration consisted of a sphere and a flat horizontal surface (infinite curvature radius). R-134a was used as the refrigerant in all tests. The influence of the diameters of the spheres and the spacing between them was also evaluated. It was found that an increase in the curvature of the surfaces gives rise to a reduction of the contact angle and an increase in the half-filling angle. In the sphere–sphere configuration, the contact angle was observed to be inversely proportional to the refrigerant solubility.