LOCAL COMPOSITION MODELING OF THE THERMODYNAMIC PROPERTIES OF REFRIGERANT AND OIL MIXTURES

Six local composition models of the thermodynamic behaviour of mixture s are described, Using data from the literature and a non-linear regre ssion analysis, a comparison of the predictive abilities of the models is undertaken for R12, R22, R134a and R125 with various oils. The Wil son and Heil equations provide the most consistent results, with the H eil equation providing a modest improvement over the Wilson model. Usi ng a 95% confidence interval, the Heil equation predicted the behaviou r of R12 with a paraffinic mineral oil to within 3.1%; its worst-case 2-sigma error was 10.4% (R22 with a polyol ester oil), and its average 2-sigma error for all of the mixtures was 6.2%. Using model parameter s and error estimates from the regression analyses, pressure-temperatu re-concentration behaviour for these mixtures can be predicted for sys tem design and simulation.