GASEOUS THERMAL-CONDUCTIVITY OF DIFLUOROMETHANE (HFC-32), PENTAFLUOROETHANE (HFC-125), AND THEIR MIXTURES

The gaseous thermal conductivity of difluoromethane (HFC-32), pentafluoroethane (HFC-125), and their binary mixtures was measured with a transient hot-wire apparatus in the temperature ranges 283-333 K at pressures up to saturation. The uncertainty of the data is estimated to be within 1%. The thermal conductivity as a function of composition of the mixtures at constant pressure and temperature is Found to have a small maximum near 0.3-0.4 mole Fraction of HFC-32. The gaseous thermal-conductivity data obtained for pure HFC-32 and HFC-125 were correlated with temperature and density together with the liquid thermal-conductivity data from the literature, based on the excess thermal-conductivity concept. The composition dependence of the thermal conductivity at a constant temperature is represented with the aid of the Wassiljewa equation.