Halogenated Hydrocarbons and Their Mixtures: A Decade of Progress in Calorimetry
Joe W. Magee
An accurate knowledge of thermodynamic properties is a prerequisite to design efficient and cost-effective refrigeration systems that use halogenated hydrocarbons as working fluids. We present a review of a long-range NIST project concerning experimental methods and measurements of thermodynamic properties. In total, more than 6000 measurements were reported on selected pure components and their mixtures. Key properties measured include vapor pressures or vapor-liquid equilibrium, densities, and heat capacities. Because of their significance, the review emphasizes calorimetric measurements of heat capacitiesat constant volume Cv by means of an adiabatic method, while it also covers a concurrent effort that produced vapor pressures and densities. This measurement program produced thermodynamic measurements for pure halogenated hydrocarbons including HCFC-13, HFC-23, HFC-41, HCFC-123, HCFC-124, HFC-125, HFC-134a, HFC-143a, and HFC-152a, and for their binary and ternary mixtures including HFC-32+HFC-125, HFC-32+HFC-134a, HFC-125+HFC-134a, HFC-125+HFC-134a, and HFC-32_HFC-125+HFC-134a. In addition to heat capacities, calorimetric studies produced the first reliable measurements of triple point temperatures and enthalpies of fusion for seven pure compounds. Also, heat capacities measured in the two-phase region have provided a useful means for calculating thermodynamically consistent vapor pressures at temperatures between the triple-point and the vapor pressures at temperatures between the triple-point and the normal boiling-point temperatures. Taken as a whole, this body of calorimetric measurements had a significant impact on the development of accurate predictive models. Because of the sensitivity of the mathematical models to the behavior of the heat capacity, the heat capacities from this project have strongly influenced the selection, by an international panel, of the most reliable equations of state for HFC-32, HCFC-123, HFC-125, HFC-134a, HFC-143a, and HFC-152a. The heat capacities measured for mixture systems have had an equally strong impact on the developemnt of accurate models of mixtures.
Halogenated Hydrocarbons and Their Mixtures: A Decade of Progress in Calorimetry, NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD
(Accessed June 8, 2023)