[SY-O9] Symposium O-9

[SY-O9] Lubrication with a refrigerant : a challenge made possible thanks to fluid/surface chemistry

Stéphane TROMP¹, Laurent JOLY², Manuel COBIAN³, ^○Nicolas FILLOT¹ (1.Univ Lyon, INSA-Lyon, , CNRS UMR5259, LaMCoS, F-69621 Villeurbanne, France, 2.Univ Lyon, Universite Claude Bernard Lyon 1, CNRS, Institut Lumiere Matiere, F-69622 Villeurbanne, France, 3.Univ Lyon, Ecole Centrale de Lyon, ENISE, ENTPE, CNRS UMR5513, Laboratory of Tribology and System Dynamics, F-69134 Ecully, France)

Lubrication is often seen as the major solution to avoid wear and high friction due to the relative motion of solids in contact. But this sometimes requires a heavy design (e.g. addition of lubricant pumps) while the actual trend goes for weight reduction of mechanical systems. The use of working fluids (e.g. refrigerant, gasoline) instead of classical lubricants (oil) allow to bypass this problem. Nonetheless, tribological contacts have to work with ultra low viscosity fluids (not designed to be good lubricants). The major consequence is that the film thickness separating the surfaces reaches the same order of magnitude as surface roughness. At this stage, a minimum quantity of fluid needs to be trapped between apserities to avoid direct contact. This is made possible if fluid molecules are adsorbed onto the surfaces.
The work presented here aims at explaining experimental observations of R-1233zd refrigerant ability to lubricate a highly loaded contact. Starting from a dedicated force field parametrization for the refrigerant-hematite interaction (from DFT calculations [1]), Large-Scale Molecular Dynamics simulations of extreme compression and shearing of R-1233zd show the resistance of the refrigerant adsorption, and its capability to undergo normal and tangential stresses.

[1] S. Tromp, L. Joly, M. Cobian, N. Fillot, Chemical Physics at Interfaces within a Refrigerant-Lubricated Contact: From Electronic Structure to Large-Scale Molecular Dynamics Simulations. J. Phys. Chem. C, 2018, DOI: 10.1021/acs.jpcc.7b11267