Analytic Correlation for the Thermodynamic Properties of Water at Low Temperatures (200-300 K) and High Pressures (0.1-400 MPa).

Water is vital to all facets of life and is anomalously behaving in its condensed states, making it continually a substance of interest to researchers. Therefore, attempting to capture its properties via correlations and equations of state is extremely valuable. Liquid water has not been studied as extensively in the low-temperature and high-pressure region as in other regions. Some key applications for correlations in this region are cryopreservation (specifically in certain methods of cryopreservation such as hyperbaric (high-pressure) and isochoric (constant-volume) cryopreservation), deep oceans, hydrospheres, clouds, and precipitation. Although there are not nearly as many models for water at low temperatures and high pressures as there are in other temperature and pressure ranges, there are some models that do currently exist. However, these either do not extend to temperatures and pressures as extreme as the data that exist, or they are complex with large numbers of parameters making them more difficult for application. Herein, we present a new correlation for liquid water valid for the temperature range of 200-300 K (-73-27 °C) and pressure range of 0.1-400 MPa that can analytically calculate volume, isothermal compressibility, isobaric expansivity, constant pressure heat capacity, and speed of sound, using only 17 adjustable parameters. The analytical expressions that we derived, and the fitting method that we used can also be applied to other fluids of interest in the future.