THE DIELECTRIC-CONSTANT OF LIQUID HFC 134A AND HCFC 142B

This paper presents measurements of the dielectric constant of HFC 134 a and HCFC 142b, as a function of pressure and temperature, in the tem perature range from 200 to 300 K and pressures up to 20 MPa, using a d irect capacitance method. The samples used had a stated purity of 99.8 and 99.9%, respectively. The values of the dielectric constant have a precision of 0.01% and an accuracy of 0.1%. The data obtained were co rrelated as a function of density and pressure. The theory developed b y Vedam et al., based on the Eulerian strain, and the Kirkwood equatio n for the variation of modified molar polarization with temperature an d density were applied to analyze the data and to obtain the dipole mo ment of both refrigerants in the liquid state.