Evaluation of Multistage Centrifugal Chiller Performance Metrics with Different Low Global Warming Potential Refrigerants

With a raising concern about climate change and global warming, various environmental regulations such as Kigali Amendment and EU Directive 517/2014 have already set the target to gradually phase out R134a and R123 refrigerants. In the current study, both the medium-pressure refrigerants (R134a and its alternatives R513A and R1234ze(E)) and low-pressure refrigerants (R123 and its alternatives R514A and R1233zd(E)) have been theoretically investigated for multistage chiller systems with a fixed cooling capacity. Compared with a single-stage chiller, a multistage chiller gives a \(\sim 4\)%–8% COP enhancement for medium-pressure refrigerants and \(\sim 4\)%–6% COP increase for low pressure refrigerants. Multistage systems can help to downsize the evaporator and provide more than 5% lifetime emission reductions. A two-stage chiller system is more preferable than the others for its high operating energy saving potential with limited additional component cost increase. In addition, R134a exhibits a better heat transfer performance than its candidates, while R123 exhibits a reverse behavior. R513A can exhibit a \(\sim 9\)% emission reduction as compared with R134a, and R1234ze(E) can provide a \(\sim 18\)% emission drop benefit as compared with R134a. R513A and R134a have a close compressor impeller diameter, and a similar trend can also be exhibited between R514A and R123. Accordingly, R513A is more preferred to replace R134a, and R514A to replace R123 for drop-in considerations due to their close compressor size, close COP, and reduced lifetime emissions. With approaching more strict refrigerant regulations and laws in the future, R1234ze(E) can be the ultimate option to replace R134a.