Viscosity measurements on saturated gas-expanded liquid systems—Ethanol and carbon dioxide

A recently developed method of falling-weight viscometry was employed to determine the experimental viscosities of the gas-expanded liquid system of ethanol and carbon dioxide at saturation. By adding carbon dioxide into an isochoric system containing metered amounts of ethanol, carbon dioxide concentrations within the gas-expanded liquid system were systematically varied between 0.15 and 0.80 mole fraction in 0.05 increments at constant system temperatures of 25, 30, 35 and 40 °C. Similar to the gas-expanded liquid system of methanol and carbon dioxide, an increase in carbon dioxide concentration in the liquid phase, liquid volume expansion, liquid density and system pressure resulted in a decrease in liquid phase viscosity. The significance of system temperature however, is more apparent with the gas-expanded liquid system of ethanol and carbon dioxide when compared to the gas-expanded liquid system of methanol and carbon dioxide. At equal compositions but varying system temperatures, not only is the viscosity of the ethanol and carbon dioxide system affected to a greater extent, the point at which viscosity reduction is insignificant with an increase in carbon dioxide composition occurs earlier with increasing system temperatures. The estimation of liquid phase viscosities of gas-expanded liquid systems is therefore difficult without experimental data.