THERMAL-CONDUCTIVITY OF REFRIGERANTS R123, R134A, AND R125 AT LOW-TEMPERATURES

Using a transient coaxial cylinder technique, thermal conductivities were measured for liquid 1,1,1-trifluoro-2,2-dichloroethane (refrigerant R123), 1,1,1,2-tetrafluoroethane (refrigerant R134a), and pentafluoroethane (refrigerant R125). The uncertainty of the experimental data is estimated to be within 2-3 %. Thermal conductivities of refrigerants were measured at temperatures ranging from - 114 to 20-degrees-C under pressures up to 10 MPa. The apparatus was calibrated with four kinds of liquids and gases. The features of the density dependence of thermal conductivity are indicated. Existing equations for calculating the coefficient are analyzed in cases where development has been sufficient to enable comparisons to be made with experiment. Saturated-liquid thermal conductivities for R134a and R123 are compared with corresponding experimental values.