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Experimental Thermal Conductivity Values for Mixtures of R32, R125, R134a, and Propane



Richard A. Perkins, E Schwarzberg, X P. Gao


Experimental measurements are reported for the thermal conductivity of eight binary and two ternary mixtures containing difluoromethane (R32), pentafluoroethane (R125), 1,1,1,2-tetrafluoroethane (R134a), and propane (R290). The mixtures were prepared gravimetrically from the pure components for accurate knowledge of the composition. Both the vapor and liquid phases of each mixture were studied over a temperature range from 245 K to 345 K with maximum pressures of 10 Mpa - 20 Mpa. The thermal conductivity data for the vapor phase of each mixture was obtained using transient and steady-state hot wires. Bare tungsten hot wires (4 {micro}mu diameter) were used for the vapor-phase measurements with both the transient and steady-state modes of operation. The extremely small wire diameter minimized corrections to the transient results that account for the finite wire diameter. Steady-state measurementsallowed measurements at lower pressures where the transient thermal wave penetrates to the outer cell wall in less than 1 s. Comparison between the transient and steady-state vapor resultsprovides a cross-check of the reliability of the vapor results. Anodized tantalum hot wires (25 {micro}mu diameter) were used for the liquid-phase measurements with the transient mode of operation. The anodized layer of tantalum pentoxide provides the electrical insulation required for accurate measurements in these highly polar and moderately electrically conducting liquids. The measurements cover the temperature region from 229 K to 347 K in the subcritical-vapor and compressed-liquid phases. A total of 5683 measurements are reported with an estimated uncertainty of 3 %. The data are compared with REFPROP version 6.01, a wide range extended corresponding states correlation for the thermophysical properties of alternative refrigerants and their mixtures.
NIST Interagency/Internal Report (NISTIR) - 5093
Report Number


hot wire, mixtures, propane, R125, R134a, R32, steady state, thermal conductivity, transient


Perkins, R. , Schwarzberg, E. and Gao, X. (1999), Experimental Thermal Conductivity Values for Mixtures of R32, R125, R134a, and Propane, NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed April 16, 2024)
Created December 1, 1999, Updated November 10, 2018