MOLECULAR-PROPERTIES OF ALTERNATIVE REFRIGERANTS DERIVED FROM DIELECTRIC-CONSTANT MEASUREMENTS

A review of the current wc,rk in Lisbon on the measurement of the diel ectric constant of the liquid phase of some environmentally acceptable refrigerants proposed as alternative replacements of the chlorofluoro carbons (CFCs), responsible for the destruction of the ozone layer, is presented. Measurements on HCFC 141b, HCFC 142b, HCFC 123, HFC 134a, HFC 152a, and HFC 32 samples of stated purities of 99.8 mass % or bett er were performed as a function of pressure and temperature, in the te mperature range from 200 to 300 K and at pressures up to 20 MPa. The r atio of the capacitances of a cell filled with the sample and under va cuum was measured with a direct capacitance method. The dielectric-con stant measurements have a repeatability of 0.003% and an accuracy of 0 .1%. The theory developed by Vedam et al. based on the Eulerian Strain and the Kirkwood equation for the variation of the modified molar pol arization with temperature and density were applied to obtain the dipo le moments of the refrigerants in the liquid state, to obtain a physic al insight of the molecular behavior, and to understand the equilibriu m configuration of these liquids.