Quantitative Elastohydrodynamic Film-Forming for an Oil/Refrigerant System

Abstract

The first calculations of film thickness for an oil/refrigerant system using quantitative elastohydrodynamics are reported in this work. It is demonstrated that primary measurements of the properties of the oil/refrigerant system can be employed to accurately predict film thickness in concentrated contacts. An unusual response to lubricant inlet temperature is revealed, wherein the film thickness may increase with temperature as a result of decreasing refrigerant solubility in oil when the inlet pressure is high. There is competition between the reduction in viscosity of the oil and the reduction of refrigerant concentration with increased temperature. For high inlet pressure, the dilution effect is dominant, whereas for low inlet pressure, the temperature dependence of the viscosity of the solution dominates over the range of inlet temperatures considered. It seems that only central film thicknesses have been experimentally measured for oil/refrigerant systems leaving these calculations as the only means of assessing the minimum.

Lubrication Quality of Compressor Rolling Bearings with Oil-Refrigerant Mixtures

“…As shown in this paper the Jacobson safety factor f leaves some freedom to the engineer to adapt the safety of the pursued design, since there are still several unknown factors. One of Table 3 Oil and refrigerant properties [13,14,16] (a) with f = 1.5 (b) with f = 2 Fig. 6 Adjustment factor for kappa for the two bearings of Table 1, with two values of the safety factor (Jacobson factor) them already discussed in [7] is the chemical aggressiveness of the refrigerant towards the bearing steel, reducing its fatigue strength due to corrosion or poor lubricity.…”

“…As discussed before, studies have been carried out in the past to measure and to estimate the film thickness in EHL contacts lubricated with oil-refrigerant mixtures [10][11][12][13][14]. In the calculation of film thickness in EHL contacts lubricated with oilrefrigerant mixtures the estimation of the mixture properties is a key intermediate step.…”

“…The viscosity data of the pure liquids is the starting point of the calculation. For the oil (RENSIO TRITON SEZ 68) the data published in [14], and for the refrigerant HFC-134a the measurements from [13] were used. The saturation pressure for the distinct mixing ratios of 70, 80 and 90% of oil, which are common in compressor applications and, therefore, shown in this type of graphs, are adapted from the leaflet provided by the oil manufacturer [19].…”

“…Also, Akei et al [11,12] with proposed mixture laws for viscosity and piezo-viscosity. And the recent experimental work of Bair [13] and the full elastohydrodynamic lubrication (EHL) numerical calculations of film thickness and pressures for mixtures of Bair et al [14].…”

Progress in rolling bearing technology for refrigerant compressors

“…Many studies have been carried out in the past to measure or to estimate the film thickness in EHL contacts lubricated with oil-refrigerant mixtures. [3][4][5][7][8][9][10][11][12] More recent studies of oil-refrigerant mixtures in EHL are in Bair et al 24,25 and Tuomas. 26 In the calculation of film thickness in EHL contacts lubricated with oil-refrigerant mixtures the estimation of the mixture properties is a key intermediate step.…”