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Thermophysical properties of the refrigerant mixtures R22L and R22M from dynamic light scattering (DLS)


A. Heller1, M. Rausch1, 2, A. Leipertz1, 2 and A. Fröba1, 2

1Graduate School in Advanced Optical Technologies (SAOT), University Erlangen-Nuremberg, Germany
2Institute of Engineering Thermodynamics (LTT), University of Erlangen-Nuremberg, Germany

Keywords: dynamic light scattering
property: thermal diffusivity, sound speed, surface tension, viscosity
material: refrigerant mixtures

Dynamic light scattering (DLS) has been used for the measurement of several thermophysical properties of the refrigerant mixtures R22L (79% pentafluoroethane - R125, 18.25% 1,1,1,2-tetrafluoroethane - R134a, and 2.75% isobutene - R600a) and R22M (50% R134a, 46.6% R125, and 3.4% R600a). Both refrigerant mixtures are designed for a replacement of R22 (chlorodifluoromethane) in existing refrigeration systems. While R22M is especially applicable for air conditioning systems operating at evaporation temperatures above 0°C, R22L is designed for medium and low temperature applications as they are found in supermarket or commercial refrigeration systems. Thermal diffusivity and sound speed have been obtained by light scattering from bulk fluids for the liquid phase under saturation conditions over a temperature range from about 290 K up to the liquid-vapor critical point with estimated uncertainties of less than ±1% and ±0.5%. By applying the method of DLS to a liquid-vapor interface, also called surface light scattering (SLS), the saturated liquid kinematic viscosity and surface tension can be determined simultaneously. These properties have been measured from about 240 K up to the liquid-vapor critical point with estimated uncertainties of less than ±2% and ±1%. The measured thermal diffusivity, sound speed, kinematic viscosity, and surface tension are represented by interpolating expressions with differences between the experimental and calculated values that are comparable with but always smaller than the uncertainties. The results are discussed in detail in comparison with literature data and with a simple prediction method based on the mass-weighted properties of the pure components expressed as functions of the reduced temperature.


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