SOLUBILITY AND MISCIBILITY OF REFRIGERANTS R407C AND R410A WITH SYNTHETIC COMPRESSOR OILS
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2016
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In this paper, solubility and low temperature miscibility of refrigerants R407C and R410A in four different commercial Polyolester (POE) lubricants, produced by the same company but with different ISO standard viscosity grade, are measured with the aim to evaluate the possible correlation of solubility and miscibility with standard viscosity of the lubricant. Vapor pressure (solubility) is measured using calibrated, constant volume cells at oil mass fractions 30, 50, 70, 80, and 90% over a temperature range from -20 to 100 °C, and pressures up to 5 MPa. The measurements of low temperature miscibility limit (lower critical solution temperature LCST) were made using high-pressure sapphire cell. LCST was directly obtained by visual observation of a «milky haze» followed by a phase separation. Miscibility data were obtained at oil mass fractions from 5 to 50% over a temperature range from -60 to 0 °C. A set of simple equations was derived to describe the experimental results. Analysis of the obtained results showed that the solubility of refrigerant/lubricant mixtures depends weakly on the viscosity grade of the oil. At the same time, the miscibility gap (LCST) differ much bigger for various refrigerant/lubricant mixtures. The lower viscosity grade of the oil, the lower LCST of the refrigerant/lubricant mixture. LCSTs for the mixtures of R407C with the lubricants with the viscosity grades 32 and 220 differ by 30-45 °С.