Methods for calculating the heat capacity of decafluorobutane in a liquid

Abstract

This work presents a comparison of the values of isochoric and isobaric heat capacities in a liquid in the range of parameters from 20°C to 140°C and pressures from 2 MPa to 10 MPa, obtained by two different methods. Under one of the proposed methods isobaric and isochoric heat capacities are obtained within joint thermal (pυT-dependence) and acoustic (speed of sound) measurements, the other method represents heat capacity values are obtained from a unified equation of state presented by the authors earlier based on the results of experimental and computational studies. New density measurements on 7 isotherms in the liquid and supercritical areas of state in the temperature range from 5°C to 141°C and pressure from 1.6 MPa to 10.9 MPa are presented. Estimation of the calculated based on experimental data for the isochoric heat capacity is ± 5%. The discrepancy between the calculated values of the heat capacity by both methods in the entire range of the studied temperatures reaches 30%, which is explained by the lack of experimental data on the heat capacity in the known literature.