A Generalized Corresponding-State Equation for Accurate Correlation and Reliable Extrapolation of Vaporization Enthalpy

Accurate characterization of the vaporization enthalpy from the triple point to the critical point is often limited by scarce experimental data. Existing equations are typically optimized for data fitting and may lose their reliability when extrapolated beyond the fitted range. This work develops a simple three-parameter corresponding-state equation based on the thermodynamic characteristics of the vaporization enthalpy. Evaluated using reference data for 38 fluids and experimental data for 8 representative fluids, the proposed equation reproduces fitted data with deviations below 0.5%, comparable to or better than existing equations and generally within experimental uncertainty. It also exhibits stable extrapolation under unconstrained fitting. Furthermore, a partial parameter-fixing strategy based on sensitivity analysis reduces the dependence on the fitting range and improves robustness under data-limited conditions, lowering the average extrapolation deviation below 5%. Overall, the proposed equation provides a simple, accurate, and reliable framework for the vaporization enthalpy correlation and extrapolation.