Mt. Barao et al., MOLECULAR-PROPERTIES OF ALTERNATIVE REFRIGERANTS DERIVED FROM DIELECTRIC-CONSTANT MEASUREMENTS, International journal of thermophysics, 18(2), 1997, pp. 419-438
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.