Prediction of H2O PVT relations at high temperatures by VHL equation of state

Based on the VHL equation of state(EOS) described by the L-J potential function, the water in the high-temperature situation is depicted by medium-high pressure thermodynamic states. The L-J potential function parameters of water adopt a temperature-dependent function form, and by using complex configuration optimization method, the specific value is obtained from the date in NIST during the range of 800K-1275K and 0.1GPa-1.0GPa. In order to test the suitability of VHL equation of state in high -temperature and medium-high pressure state, the theoretical and experimental data of higher temperature and pressure range are investigated. What’s more, the theoretical calculation results of VLW, DMW, BS and TIP4P equations of state are compared. The results show that, during the high-temperature and medium-high pressure section, the volumetric error of water calculated by VHL equation of state is less than 7%. Considering the uncertainty of the experimental data, it can be thought that the VHL equation of state and the temperature-dependent potential function form proposed in this paper can describe the state of water in high temperature, medium-high pressure better.