Revisiting the Compressibility of Oil/Refrigerant Lubricants

Abstract

A fixture was fabricated for the purpose of restraining the expansion of an existing metal bellows piezometer so that a refrigerant and oil mixture can be admitted under pressure. Measurements on a polyol ester (POE) with 9.2 wt.% of R134a show that the addition of refrigerant slightly increases compressibility. The previously reported reduction in compressibility (increase in bulk modulus) by Tuomas and Isaksson (2006, “Compressibility of Oil/Refrigerant Lubricants in Elasto-Hydrodynamic Contacts,” ASME J. Tribol., 128(1), pp. 218–220) of an ISO 68 POE when mixed with R134a cannot be supported by precise measurements of the volume compression. The increased compressibility found by Comuñas and co-workers (2002, “High-Pressure Volumetric Behavior of x 1, 1, 1, 2-Tetrafluoroethane + (1 − x) 2, 5, 8, 11, 14-Pentaoxapentadecane (TEGDME) Mixtures,” J. Chem. Eng. Data, 47(2), pp. 233–238) is the correct trend. The Tait equation of state (EoS) has been fitted to the data for both the neat POE and its 9.2% by weight mixture with refrigerant. The usual problem was encountered for the mixture with the Tait EoS at low pressure where the compressibility becomes greater than predicted due to proximity to the vapor dome. The measured relative volumes of the mixture can be used to collapse the viscosity to a master curve when plotted against the Ashurst–Hoover thermodynamic scaling parameter. The thermodynamic scaling interaction parameter is approximately the same as for the neat oil.

Fractionation and Characterization of the Bioactive Compounds of the Extracts of Buds of Syzygium aromaticum

“…The DEPT result further simplified the 13 This study therefore supports and justifies the traditional uses of Syzygium aromaticum flower buds for treating a variety of diseases. This is in line with the finding made by [38] who investigated the antibacterial activity of Syzygium aromaticum flower buds and came to the conclusion that the main ingredient in clove oil, eugenol, is widely used in folk medicine as an analgesic, anti-vomiting, antispasmodic, kidney-enhancer, antiseptic, diuretic, and aromatic agent [39].…”

“…The 0.5 McFarland standard was made by continuously swirling 9.95 mL of 0.18M H2SO4 with 0.05ml of barium chloride (BaCl2) (1.17% w/v BaCl2.2H2O). The McFarland standard tube was kept in storage with a tight seal to prevent evaporation loss [11,12,13].…”

Lubrication Quality of Compressor Rolling Bearings with Oil-Refrigerant Mixtures

“…Other authors, however, claim refrigerants are less compressible than oils [26]. However the consensus and measurements [27] seem to show that indeed refrigerant are more compressible than oils. To develop a multiplication adjustment factor for this equation due to the effect of higher or lower compressibility of the refrigerant, one needs to start from the effect of compressibility in the central film thickness.…”

Thermophysical Property Modeling of Lubricant Oils and Their Mixtures with Refrigerants Using a Minimal Set of Experimental Data

“…Today, however, there is no such model set to rely on for oils. The existing models, e.g., see refs − for oils, are generally empirical equations for each property (mainly density and viscosity) fitted to experimental data; these equations are usually independent of each other, which leads to thermodynamic inconsistencies. Moreover, entropy and enthalpy are hard to measure accurately, and thus, there are barely any empirical equations for both properties.…”