Modeling heat capacity of liquid hydrofluorocarbons and hydrofluoroolefins

Abstract

As for a heat capacity model of molecular liquids, high regression accuracy and reasonable extrapolation ability are two long-term goals. However, very few methods can meet the two requirements, which limits the accuracy of relevant engineering calculations. In this work, a semi-empirical model which can solve this problem was established to obtain the heat capacity (cp) of hydrofluorocarbons (HFCs) and hydrofluoroolefins (HFOs). Here, heat capacities of HFCs and HFOs in the whole liquid region can be obtained if the critical parameters (Tc, pc), acentric factor, ideal gas isochoric heat capacity and at least two different experimental cp data points are known. The proposed model was utilized to calculate the liquid isobaric heat capacity of 12 fluids (10 HFCs and 2 HFOs) and the average absolute deviation (AAD) of the present method calculations from experimental data is 1.01%. Furthermore, heat capacities calculated by the proposed model were compared with the calculations from other models. The results indicate that the present fitting method is superior to other models for representing heat capacities, with regard to the accuracy. Additionally, 36 data points of experimental liquid heat capacity of trans-1,3,3,3-Tetrafluoropropene (also known as HFO-1234ze(E)) in high pressure region were reported in this work and were used to check the present model’s extrapolation ability. High regression accuracy and good extrapolation performance make the proposed method a valuable tool to represent liquid heat capacity of hydrofluorocarbons and hydrofluoroolefins.