Mixture Models for Refrigerants R

The fourth generation of refrigerants largely comprises mixtures containing halogenated olefins,1 for instance, to find non-flammable blends to replace the workhorse refrigerant R-134a.2 In order to reliably assess novel mixtures, new mixture models in the form of equations of state (EOS) are needed for each of the binary pairs included in the candidate mixtures. Of the six binary mixtures we selected for study, current models are all based upon estimation schemes or unpublished models in REFPROP 10.0.3,4 New reference experimental measurements are needed to improve the mixture models. As outlined below, these measurements were obtained as part of the larger project, forming the foundation for the mixture models. This work begins the process of filling in the holes where important mixture models need to be updated or developed.3 

The components considered in this work are all relatively similar and some information about them is presented in Table 1. Two [R-1234yf and R-1234ze(E)] are stereoisomers, and the three main components of the comprehensive measurements have a hydrocarbon backbone with the replacement of four hydrogens by fluorines (as indicated by 4 as the right-most numerical digit). Therefore, we might expect (as we see here) that mixtures of these compounds would behave in a relatively simple way, with nearly ideal mixing behaviors. This makes refrigerant mixtures such as these ideal candidates for the development of highly accurate mixture models.

Metadata on the pure components, sorted by normal boiling point temperature. Numerical values are taken from the respective EOS and are rounded for presentation; the unrounded value from the EOS should be used. M: molar mass

The hash used in REFPROP to define the mixture models is generated from the SHA256 hash of the standard InChI key from hashlib.sha256(StdInChIkey).hexdigest()[2:9] + “0” with the hashlib module from the Python standard library.