Assessment Of The Pressure-volume-temperature（PVT）Data Of CO₂ And CH₄

The pressure-volume-temperature(PVT) data from experiments and molecular dynamics(MD) and Monte Carlo(MC) simulations of CO2 and CH4 since 1991 are assessed systematically in this work. The reference data used here are from the CO2 Helmholtz free energy model of Span and Wagner(1996)(SW96), the CH4 Helmholtz free energy model of Setzmann and Wagner(1991)(SW91), and their appropriate extrapolations.Among the experimental PVT data of CO2, the data of Klimeck et al.(2001) and Mantilla et al.(2010) agree very well with SW96 model. The data of Tomoya et al.(2004)also agree well with the SW96 model, but it has small systematic deviation. The volume data of Pensado et al.(2008) have obvious systematic deviations, but all deviations are within 0.8%. The data of Pe?ar and Dole?ek(2007) are accurate at P≥20 MPa, but their volume deviations are up to –3.3% near the critical pressure. The data of P?hler et al.(1997)and Langenfeld et al.(1992) have large deviations, where the deviations of the latter decrease rapidly with increasing pressure.The CO2 volume data of Belonoshko and Saxena(1991), Destrigneville et al.(1996)and Zhang et al.(2005) obtained by MD and MC simulations cover a wide P-T range The data of Belonoshko and Saxena(1991) have large uncertainties and systematic deviations.The volume data of Destrigneville et al.(1996) have obvious systematic deviations, which show very good positive correlation with pressure. The simulated data of Zhang et al.(2005)has an overall deviation of about +1%, but most deviations are within 3%, except for very few data points at low pressures.Among the experimental PVT data of CH4, the data of Li et al.(2012) and Klimeck et al.(2001) agree very well with the SW91 model. The data of Abdulagatov et al.(1996)agree well with the SW91 model or its extrapolation below 40 MPa, but their volume deviations become negative(within –1.5%) as pressure increases. The volume or pressure deviations of Abdulagatov et al.(1993) are scattered, but are all within 1%. The data of Shmonov et al.(1993) contain obvious systematic deviation, where the 140 MPa data contain misprints.Belonoshko and Saxena(1991) and Zhang et al.(2007) obtained many volume data of CH4 in a wide P-T range by MD simulations. The data of the former group have obvious systematic deviations, as well as large uncertainties in both temperature and pressure. The data of Zhang et al.(2007) below 1000 K agree well with the extrapolation of the SW91 model.