Ejectors could improve CO2 transcritical system efficiency by up to 20% in Southern climates

To illustrate the fact that the efficiency challenge related to ordinary R744 booster systems operated at high ambient temperatures can be overcome, J. Schönenberger et al. analysed the performance of a CO2 commercial refrigeration system with parallel compressor technology and three ejectors, installed in a 5,000 m2 supermarket in Fribourg, Switzerland in 2013.

Thanks to the ejectors, the annual energy efficiency improvement potential compared to traditional CO2 systems with parallel compression is between 10 to 20%, depending on the climatic region and the integration of heat recovery systems.
In addition, further efficiency increase can be achieved by increasing the evaporation temperature of low temperature refrigeration.

Efficiency gains are attributed to the fact that the three ejectors partly recovering the expansion work. This in turn is applied to return liquid and vapour from the low pressure receiver downstream of the medium temperature evaporators back to the medium pressure receiver, located upstream of all evaporator refrigerant supply valves.
Moreover, frost formation on the evaporators and the number of defrost cycles is reduced.

Experience with ejectors implemented in a R744 booster system operating in a supermarket, J. Schönenberger et al.

This paper was presented during the 11th IIR-Gustav Lorentzen Conference in Hangzhou, China, in September 2014.
It can be downloaded in Fridoc database (free for IIR members within their free download quota):http://www.iifiir.org/clientBookline/service/reference.asp?INSTANCE=exploitation&OUTPUT=PORTAL&DOCID=IFD_REFDOC_0012281&DOCBASE=IFD_REFDOC_EN&SETLANGUAGE=EN
Remember to log in or register first !