Molecular properties of alternative refrigerants derived from dielectric-constant measurements

A review of the current work in Lisbon on the naeasurement of the dielectric constant of the liquid phase of some environmentally acceptable refrigerants proposed as alternative replacements of the chlorolluorocarbons (CFCs), responsible lbr the destruction of the OZOlle layer, is preseInted. Measurements on HCFC 141b, HCFC 142b, HCFC 123, HFʹC 134a, HFC 152a, and HFC 32 samples of stated purities of 99.8 mass% or better were performed as a function of pressure and temperature, in the ternperature range frorn 200 to 300 K and at pressures up to 20 M Pa. The ratio of the capacitances of a cell filled with the sample and under vacuum was measured with a direct capacitance method. The dielectric-constant measurellaCnts have a repeatability of 0.003% and an accuracy of I).[ ~ The theory developed by Vedam et al. based on the Eulerian Strain and the Kirkwood equation lbr the variation of the rnodilied molar polarization with temperature and density were applied to obtain the dipole naoments of the refrigerants in the liquid state, to obtain a physical insight of the molecular behavior, and to understand the equilibrium conliguration of these liquids.