Zero-ODP Refrigerants for Low Tonnage Centrifugal Chiller Systems

This paper investigates the use of several zero-ozone depleting potential zero-ODP HFC refrigerants, including, HFC-134a, HFC-227ca, HFC-227ea, HFC-236ea, HFC-236cb, HFC-236fa, HFC-245cb, and HFC-254cb, for centrifugal chiller applications. We took into account the thermodynamic properties of the refrigerant and aerodynamic properties of the impeller compression process to this evaluation. For a given operating temperature lift, there are significant differences in the pressure ratio required by each refrigerant and this variation in pressure ratio directly affects compressor size, efficiency, and performance. A comparison of the HFC refrigerant candidates with CFC-114 shows that HFC-236ea, HFC-227ca, and HFC-227ea are viable alternatives for centrifugal water chillers. HFC-227ea results in a significantly lower enthalpy rise requirement, potentially allowing single-stage compression, however, wet compression could be a problem. Single-stage compression gives an overall performance advantage over CFC-114 and when considering thermodynamics and aerodynamics, as is necessary in centrifugal applications, we find that HFC-227ca and HFC-227ea have additional advantages over HFC-236ea and CFC-114.