MEASUREMENTS OF SOLUBILITY, LIQUID DENSITY, AND LIQUID VISCOSITY FOR CO_2-LUBRICANT MIXTURES

摘要

Experimental data on solubility, liquid density, liquid viscosity, and miscibility measured with carbon dioxide (CO_2) and three types of potential lubricants, a polyalkyene glycol (PAG), a polyolester (POE), and a polyvinyl ether (PVE), are presented. Measurements were also made and are presented with a baseline polyalkyene glycol (PAG) lubricant with 1,1,1,2-tetrafluoroethane (HFC-134a). An experimental facility for measuring the thermophysical properties of the refrigerant-lubricant mixtures has been developed to carry out experiments from -30 to 125℃ with pressures from vacuum to 15.0 MPa. The apparatus operates on a recirculation method utilizing a vibrating-tube densimeter for mixture density measurements, an oscillating piston viscometer for mixture viscosity measurements, platinum RTDs for temperature measurements and a precision strain-gauge pressure transducer for solubility measurements. Measurements have k = 2 uncertainty levels of ±0.15 K in temperature, ±20 kPa or ±3.5 kPa in pressure, liquid density uncertainty of ±0.002 g/cm~3, liquid viscosity uncertainties down to ±0.1 cP, and liquid refrigerant composition uncertainty below ±0.002 g/g. The data are presented both in tabular formant and in the form of "Daniel Charts", a viscosity-temperature chart that contains an overlay of the solubility of the refrigerant-lubricant mixture. Since CO_2 is only partially soluble in the chosen lubricants, the miscibility phase separation boundary (VLLE) was also measured.