Solubility data of refrigerant/lubricant mixtures have been modeled with cu
bic equations of state (EOS): van der Waals (vdW), Soave-modified Redlich-K
wong (SRK), or Peng-Robinson (PR) types. The temperature dependence on the
"a" parameter in the EOS is modeled with a common empirical function for pu
re refrigerants, including oils. For lubricants, a hypothetical oil (UniOIL
) has been developed with universal oil EOS constants, and it is valid for
any kind of lubricant oil, Only an average molecular weight is required for
any type of oil. The mixing rules for the a and b parameters of EOS are mo
re general than the ordinary van der Waals-Berthelot formula, and a justifi
cation of such mixing rules is discussed. The refrigerants studied are R-32
, R-125, R-134a R-143a, R-152a, R-12, R-22, R-123 and R-13B1. The lubricant
s are naphthenic mineral (MO), alkylbenzene (AB/HAB), and polyol ester (POE
) oils, as well as model compounds with pure component oils (hydrocarbons a
nd POE), They are all analyzed with the UniOIL model. Good quality experime
ntal solubility (PTx) data were selected from the literature and well corre
lated within their experimental uncertainties. All the cubic EOS (vdW, SRK,
and PR) having the same type of mixing forms for the a and b parameters sh
owed excellent fits to the experimental PTx data with essentially the same
degree of accuracy, The results in this report are shown with the SRK type
EOS.