International audienceThis study presents film thickness and friction measurements of the refrigerant R1233zd (E-1-chloro-3,3,3,trifluoropropene-1) in a tribological contact. For the film thickness, optical interferometry technique with glass–steel contact is used in a ball-disc configuration, whilst for the traction measurements (Stribeck and traction curves), a contact ceramic ball–steel disc is used. In both cases, the Wedeven Associates Machines-5 tribometer is employed. An attempt to model the film thickness results is also carried out. The model gives a reasonably good prediction with respect to the experiments

The paper describes the latest technological solutions in rolling bearings (ball and roller) used in refrigerant compressors. First, the numerous tribological challenges faced by rolling contacts in a lubricant environment made of oil and refrigerant mixture are discussed. It is followed by a description of the even tougher conditions derived by the replacement of the more chemically stable pre-Montreal and pre-Kyoto Protocol refrigerants by the new generation of more environmental friendly refrigerants. In these conditions, rolling bearings are expected to suffer from surface distress and sometimes corrosion fatigue. Thus, attempts to model these conditions by using advanced tribological models are described. Finally, descriptions of different solutions in rolling bearings in refrigerant compressors facing challenges in lubrication and bearing life are described, all the way from traditional oil–refrigerant mixture lubrication up to the latest innovation related to oil-free lubrication, namely the pure refrigerant lubrication.

In refrigerant compressor, rolling bearings are lubricated with a mixture of oil and refrigerant. This has always represented a challenge for the bearing lubrication quality estimation (e.g. kappa or lambda parameters). Even if the dilution rate of the refrigerant is known, the exact effect on the lubricant film thickness remains doubtful due to the unknown piezo-viscosity and compressibility of the refrigerant and their variation with pressure and temperature. In the current paper, existing mixing laws for viscosity and piezo-viscosity are examined and adapted to better represent actual measurements. The results are compared with published Daniel plots showing reasonable agreement. Once this is done a modification to the bearing lubrication quality parameter kappa is proposed to better reflect the effect of the refrigerant on the lubrication quality of compressor rolling bearings. This is a first step in the direction of predicting the bearing life for this challenging application.

A first cavitation modeling with thermal effects for oil/refrigerant solutions lubricated ElastoHydroDynamic (EHD) point contacts is reported in this work. The solubility of the oil/refrigerant system is introduced into the Generalized Reynolds equation coupled with the elasticity equation and the energy conservation equation. The numerical results show a very good agreement with the published experimental results concerning film thickness prediction. Moreover, the present model describes the cavitation region on a physical basis. A discussion with other cavitation models from the literature is proposed. It puts into light the necessity of taking into account the solubility of the refrigerant into oil for such problems. Compared to pure oil, oil/refrigerant solutions can potentially reduce the amount of liquid oil for the next contact due to its higher cavitation intensity.