HTHP EA HomeIssue Contents

Dielectric constant and dipole moment of hydrofluorocarbon refrigerant mixtures R404A, R407C, and R507
Filipe de Brito, Anelia Gurova, Carlos Nieto de Castro, Umesh Mardolcar

Reliable dielectric property information about three HFC mixtures currently regarded as replacements for R22 and R502 is given. The static dielectric constants of the ternary systems HFC125/143a/134a (R404A), HFC32/125/134a (R407C), and of the binary system HFC125/143a (R507) in the liquid phase were measured by the direct capacitance method at temperatures from 217 to 303 K and under pressures up to 16 MPa. The uncertainty of the measurements is estimated to be within 0.1% and the repeatability 0.01%. A complete set of tables is given of experimental data as a function of temperature, pressure, and density, which covers dielectric property needs for most engineering applications. The data obtained were correlated as a function of density and temperature by polynomial equations. In order to study the dependence of dielectric constant on density and temperature on a molecular basis, the theory developed by Vedam and Chen and adapted by Diguet was applied to analyse the data. Estimates for the dipole moments of the mixtures based on dielectric constant measurements are given. The Kirkwood theory was used to obtain the values of apparent dipole moments of R404A, R407C, and R507 in the liquid phase.

Full Text (IP)