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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

Author(s)

Joe W. Magee

Abstract

Molar heat capacities at constant volume (Cv) 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 (Cv2), saturated-liquid (Cς^Cx'), and single-phase (Cv) molar heat capacities. The Cς 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 Cdv^ is estimated to be 0.7 %, for Cv2 it is 0.5 %, and for Cς it is 0.7 %.
Citation
International Journal of Thermophysics
Volume
19
Issue
No. 5

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 May 20, 2024)

Issues

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Created September 1, 1998, Updated February 17, 2017