Viscosities of HFC-32 and HFC-32/lubricant mixtures

A modified capillary tube method has been used to measure viscosities for HFC-32 over a temperature range from -20 to 90°C and a pressure range from 0.1 to 5.3 MPa, and for the liquid mixtures of HFC-32 with a synthetic polyolester oil at temperatures from 20 to 75°C and oil mass fractions from 0.44 to 1. Estimated uncertainties in the measured viscosities do not exceed ±1.2 and ±1.8% for the pure fluocarbon and the mixtures, respectively. It is found that viscosity isotherms for HFC-32 at subcritical temperatures exhibit a minimum with increasing pressure, with the viscosity decreasing as much as 10% relative to its value at one atmosphere. Correlations are presented for dilute gas viscosities, excess viscosities, and saturated liquid and vapor viscosities. These correlations are shown to fit our data within experimental uncertainties. For HFC-32/lubricant mixtures, a free-volume viscosity model has been applied to correlate the experimental data.