Molar Heat Capacity at Constant Volume of 1,1-Difluoroethane (R152a) and 1,1,1-Trifluoroethane (R143a) from the Triple-Point Temperature to 345 K at Pressures to 35 Mpa

Published

September 1, 1998

Author(s)

Joe W. Magee

Abstract

Molar heat capacities at constant volume (C_v) of 1,1-difluoroethane (R152a) and 1,1,1-trifluoromethane (R143a) were measured with an adiabatic calorimeter. Temperatures ranged from their triple points to 345 K, and pressures up to 35 Mpa. Measurements were conducted on the liquid in equilibrium with its vapor and on compressed liquid samples. The samples were of high purity, verified by chemical analysis of each fluid. For the samples, calorimetric results were obtained for two-phase (C_v²), saturated-liquid (C_ς^C_x'), and single-phase (C_v) molar heat capacities. The C_{ς data were used to estimate vapor pressures for values less than 0.3 MPa by applying a thermodynamic relationship between the Saturated liquid heat capacity and the temperature derivatives of the vapor pressure. The principal sources of uncertainty are the temperature rise measurement and the change-of-volume work adjustment. The expanded uncertainty (at the two-sigma level) for C}dv^ is estimated to be 0.7 %, for C_v² it is 0.5 %, and for C_ς it is 0.7 %.

Citation

International Journal of Thermophysics

Volume

19

Issue

No. 5

Pub Type

Journals

Keywords

1, 1, 1-trifluoroethane, 1, 1-difluoroethane, enthalpy of fusion, heat capacity, R143a, R152a, triple point, vapor pressure

Citation

Magee, J. (1998), Molar Heat Capacity at Constant Volume of 1,1-Difluoroethane (R152a) and 1,1,1-Trifluoroethane (R143a) from the Triple-Point Temperature to 345 K at Pressures to 35 Mpa, International Journal of Thermophysics (Accessed April 26, 2024)