Wetting behavior and interfacial tension of a refrigerant oil in air and refrigerant atmospheres

• Published in: International journal of refrigeration Vol. 107; pp. 225 - 233
• Main Authors: Rausch, Michael Heinrich, Schmidt, Patrick Sebastian, Gall, Thomas Roland, Giraudet, Cédric, Fröba, Andreas Paul
• Format: Journal Article
• Language: English
• Published: Paris Elsevier Ltd 01.11.2019; Elsevier Science Ltd
• Subjects: Atmospheres; Grinding; Grooves; Interfacial bonding; Interfacial tension; Lubricant; Lubricants; Lubricants & lubrication; Lubrifiant; Mouillage; Polyalkylene glycol; Polyalkylène glycol; Pressure; R-134a; Refrigerants; Refrigeration; Solid surfaces; Spreading velocity; Surface tension; Temperature; Temperature dependence; Tension interfaciale; Tetrafluoroethane; Vitesse de propagation; Wettability; Wetting; Tension interfaciale; Spreading velocity; Polyalkylène glycol; R-134a; Wetting; Polyalkylene glycol; Interfacial tension; Mouillage; Vitesse de propagation; Lubrifiant; Lubricant
• ISSN: 0140-7007; 1879-2081
• DOI: 10.1016/j.ijrefrig.2019.08.011

•New method for characterization of wetting behavior based on spreading velocities.•Increase in spreading velocity of PAG-based lubricant in R-134a atmosphere.•Non-uninform spreading accessible by optical analysis.•Decreasing interfacial tension with increasing R-134a pressure at constant temperature.•Temperature dependence of interfacial tension affected by solubility. In the present study, the wettability of ground AISI 321 steel and PTFE surfaces with a polyalkylene glycol-based lubricant in air and 1,1,1,2-tetrafluoroethane (R-134a) atmospheres is characterized. For this, spreading velocities are determined from videos recorded during the continuous dosing of lubricant on the solid surfaces. The results are compared with interfacial tension data for the lubricant measured by the pendant-drop method in air and R-134a atmospheres. Significantly higher wettability was found in the presence of refrigerant atmosphere, on the steel surface and along its grinding grooves, whereas no consistent temperature-dependent trends could be identified. The interfacial tension of the lubricant decreases with increasing temperature at ambient air atmosphere as well as with increasing R-134a pressure at a fixed temperature. The temperature-dependent behavior of the interfacial tension for a given refrigerant pressure is affected by the temperature itself and by the resulting solubility of the refrigerant in the lubricant. [Display omitted]