Molar Heat Capacity at Constant Volume of Trifluoromethane (R23) From the Triple-Point Temperature to 342 K at Pressures to 33 Mpa

Published

November 1, 2000

Author(s)

Joe W. Magee, H Duarte

Abstract

Molar heat capacities at constant volume (C_v) of trifluoromethane (R23) have been measured with an adiabatic calorimeter. Temperatures ranged from the triple point to 342 K, and pressures up to 33.5 Mpa. Measurements were conducted on the liquid in equilibrium with its vapor and on compressed liquid and gaseous samples. The samples were of high purity, verified by chemical analysis. Calorimetric quantities are reported for the two-phase (C_v²), saturated-liquid (C_ς^C_x'), and single-phase (C_v) molar heat capacities. The C_v⁽²⁾ data were used to estimate vapor pressures for values less than 100 kPa by applying a thermodynamic relationship between the two-phase internal energy U⁽²⁾ and the temperature derivaives of the vapor pressure. The triple-point temperature and the enthalpy of fusion were also measured. The principal sources of uncertainty are the temperature rise measurement and the change-of-volume work adjustment. The expanded relative uncertainty (with a coverage factor k=2 and thus a two-standard deviation estimate) is estimated to be 0.7%, for C_v 0.5%, for C_v², and 0.7% for C_sigma.

Citation

International Journal of Thermophysics

Volume

21

Issue

No. 6

Pub Type

Journals

Keywords

enthalpy of fusion, heat capacity, R23, trifluoromethane, triple point, vapor pressure

Citation

Magee, J. and Duarte, H. (2000), Molar Heat Capacity at Constant Volume of Trifluoromethane (R23) From the Triple-Point Temperature to 342 K at Pressures to 33 Mpa, International Journal of Thermophysics (Accessed April 26, 2024)