new correlations for predicting thermodynamic properties of hydrocarbons in the ideal gas state

A new empirical correlation is developed for the accurate prediction of isobaric heat capacity, enthalpy, and entropy of pure hydrocarbons and petroleum fractions in the ideal gas state, with a particular emphasis on the low-temperature region (200–300 k). unlike traditional models such as kesler-lee, huang, and kuznetsov, which are often limited in accuracy or applicability at low temperatures or for heavy hydrocarbons, the proposed correlation integrates a fourth-degree polynomial approach and molecular weight dependence to extend predictive capabilities across a broad range of components—from butane to heavy fractions exceeding 570 g/mol. validation against 340 experimental data points for heat capacity and 112 data points for enthalpy and entropy reveals a significant reduction in aare and mare values, achieving errors of 0.90% and 2.10%, respectively. while the correlation provides excellent results for normal alkanes, its applicability to cycloalkanes and aromatic hydrocarbons is limited and may require further refinement. the proposed model holds strong potential for implementation in thermodynamic simulators for oil, gas, and condensate production and processing, especially under surface conditions where precise thermophysical data at subambient temperatures are critical.