Modeling heat capacity of saturated hydrocarbon in liquid phase over a wide range of temperature and pressure

Abstract

Hydrocarbons are widely used in various industrial processes. Heat capacity of liquids is one of the basic properties in engineering equipment design and establishment of equations of state. Therefore, it is important to develop reliable and accurate models for representing heat capacities of hydrocarbon liquids. In this paper, a new model was proposed to calculate the isobaric heat capacity (cp) of saturated hydrocarbons (contain only single bonds between carbon atoms, including n-alkanes, branched alkanes and cycloalkanes) in liquid phase over a wide range of temperature and pressure. The present model was inspired by the Peng-Robinson equation of state and general thermodynamic relationships, with an empirical correction to improve the heat capacity formulation by Peng-Robinson equation for representing isobaric heat capacity of saturated hydrocarbons in liquid phase. The proposed model was used to reproduce the isobaric heat capacity of 19 compounds. The average absolute deviations between the results of the present model and corresponding experimental data are 0.47% with known critical point, acentric factor, ideal gas isochoric/isobaric heat capacity and at least two different experimental cp data points. Moreover, the isobaric heat capacity data obtained by the proposed model were compared with the calculations from other models (Peng Robinson equation and Helmholtz equation). The proposed model offers a simple and reliable way to obtain the isobaric heat capacity of saturated hydrocarbons in liquid state with satisfactory accuracy. In addition, the new model also revealed an excellent extrapolation ability in the high temperature region, which means researchers can obtain high-temperature liquid cp data even not reported by using present model based on several available experimental cp data points.