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Experimental comparison of cycle modifications to a multi-stage two-evaporator transcritical CO2 refrigeration cycle

Number: 2166

Author(s) : BARTA R. B., BECK P. E., ZIVIANI D., GROLL E. A.


With increasing awareness of the adverse effects of carbon emissions on the environment, researchers within the heating, ventilation, air conditioning, and refrigeration (HVAC&R) community have been pushing for lower global warming potential (GWP) and natural working fluids as well as systems that are more efficient than the higher-GWP systems they replace. One such working fluid is carbon dioxide (CO2). While CO2 has the advantages of being lowcost, non-flammable, and possessing a high volumetric heat capacity, it has a high critical pressure associated with a low critical temperature, thus often necessitating transcritical operation that requires significant compressor input power. As such, numerous cycle modifications have been proposed that enable the transcritical CO2 cycle to match, and in some cases surpass, the coefficient of performance (COP) of existing hydrofluorocarbon (HFC) cycles under the same operating conditions. This work provides an experimental comparison of four cycle architectures that utilize the same compressors and heat exchangers. This enables a meaningful comparison of these modifications, consisting of open economization with an evaporator bypass, as well as both electronic expansion valve (EXV) and ejector expansion strategies, along with a pump applied between the gas cooler outlet and the ejector motive nozzle inlet for control and increased recoverable pressure differential. Experimental parametric studies were conducted, and comparisons of architecture costs and benefits are presented. Design recommendations are provided along with future work.

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  • Original title: Experimental comparison of cycle modifications to a multi-stage two-evaporator transcritical CO2 refrigeration cycle
  • Record ID : 30028424
  • Languages: English
  • Subject: Technology
  • Source: 2021 Purdue Conferences. 18th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2021/05
  • Document available for consultation in the library of the IIR headquarters only.


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