Heat capacity of petroleum fractions

Abstract

Heat capacity is an important thermodynamic parameter that is needed in calculating phase equilibria, particularly for petroleum disperse systems in predicting the low-temperature behavior of petroleum products. For hydrocarbons and other organic compounds in the ideal-gas state, heat capacities can be determined by means of many different formulas and tables. A formula is given in for calculating the heat capacity of petroleum fractions in the gas phase on the basis of data from structural-group analysis. The calculation of heat capacities of petroleum fractions in the liquid phase is much more complicated. A number of correlations with density and average boiling point have been proposed. However, none of these differ greatly in accuracy of calculation from the well-known formula of Cragoe. The error may be as much as 20%, which is not acceptable in thermodynamic calculations of equilibria in petroleum systems in the liquid phase. The authors have correlated the rather scanty literature data on the liquid-phase heat capacity of hydrocarbons, nonhydrocarbon components, and fractions of crude oil, as well as some data on the partial heat capacities of groups of organic compounds.