Critical temperature and performance of refrigerants - Application to chillers.

The comparison between fluids for a given application usually requires complex calculations; this makes it confusing for non experts to make relevant choices. In this paper, it is shown that in spite of the complexity of the issues, knowing only the critical temperature of a fluid is sufficient to make amazingly precise comparisons between fluids, regarding major parameters of practical interest. Cycle comparisons are made for a variety of natural and synthetic fluids. The conditions studied cover typical Air Conditioning applications, including warm climates, in various cycle configurations. The outputs are key parameters of practical importance: energy efficiency, operating pressures, and required volumetric flow. For most fluids, these parameters correlate amazingly well, making them predictable from the critical temperature only. This applies to the synthetic fluids and to hydrocarbons. But fluids with a very different molecular structure, like ammonia or water vapor may deviate significantly from this common behavior.