Solubility of refrigerants in various lubricants

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.