Effective Thermophysical Constants of Thousands of Fluids. I: Critical Temperature, Critical Pressure, Critical Density, and Acentric Factor

Thermophysical constants of pure fluids, including critical temperature, T_c, critical pressure, p_c, critical density, ρ_c, and acentric factor, ω, are fundamental for calculating thermophysical properties over wide pressure and temperature ranges. However, complete sets of (T_c, p_c, ρ_c, and ω) values, along with traceable determination methods and careful evaluations, are available only for a limited number of fluids in commonly used databases. To address this gap, we compiled, examined, and fitted complete (T_c, p_c, ρ_c, ω) values of 1422 pure fluids, mainly from three sources: NIST’s REFPROP 10.0 database, NIST’s ThermoData Engine 10 and Dortmund Data Bank 2023. The fitting was carried out using the experimental temperature, pressure, and density (T, p, ρ) data and saturated temperature and pressure (T_sat, p_sat) data, primarily with the Yang-Frotscher-Richter EoS. The results should be considered optimized values that best match experimental data, rather than absolute physical constants. The reliability of each value was assessed to guide future experimental research. This study is the first in a series aimed at determining effective thermophysical constants of thousands of fluids for the accurate calculation of all important thermophysical properties. The results will be implemented in the software OilMixProp and Ebsilon for practical applications.