Liquid-Phase Thermodynamic Properties for Propane (1), n-Butane (2), and Isobutane (3)

Hydrocarbons (HCs) are environmentally friendly natural refrigerants and are expected to be promising alternative candidates to replace some currently used halogenated hydrocarbon refrigerants. Some available data sets for HCs used to formulate the equations of state (EoS) for them are relatively old, so we point out that new data with less uncertainty are expected to play an essential role in updating the EoS for HCs. Therefore, a set of PVT property measurements for hydrocarbon refrigerants including propane, n -butane, and isobutane was conducted in the present study. A newly developed vibrating-tube densimeter was employed for the measurements, and then a total of 430 liquid PVT properties were obtained, including those at the saturation boundaries. The measurement range is (240 to 380) K for temperature and up to 7 MPa for pressure. The measurement uncertainty is about 3 mK for temperature, 0.26 kPa + 0.022% for pressure, and 0.1 kg·m -3 + 0.024% for density. The present data were compared with available thermodynamic models that are currently considered to be the most reliable. A set of modified Tait equations of state for the liquid phase are also discussed.