IIR document

Experimental investigation of transcritical CO2 ejector system performance.

Author(s) : ELBEL S., HRNJAK P.


In order to compete with air-conditioning systems that use halogenated refrigerants, the performance of the transcritical CO2 cycle needs to be improved at elevated ambient temperatures. One of the options is through expansion work recovery by ejector for which CO2 offers excellent potential. This paper presents experimental results for different ejector geometries and operational parameters and derives appropriate control strategies. This particular ejector prototype has a variable area motive nozzle. A high-side pressure control strategy for efficient ejector system operation is developed and presented. Mass entrainment and suction pressure ratios can be used to evaluate and assess the ejector performance. It is shown how the metering valve installed downstream of the vapour-liquid separator can be used to control the balance between ejector entrainment and pressure lift. This allows compensation of effects caused by operation at different ambient temperatures and at off-design compressor speeds. Flow visualization and static wall pressure distributions indicate the existence of complicated two-phase shock patterns in the mixing section with a significant impact on ejector performance.

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Pages: ICR07-E1-72


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  • Original title: Experimental investigation of transcritical CO2 ejector system performance.
  • Record ID : 2007-2483
  • Languages: English
  • Source: ICR 2007. Refrigeration Creates the Future. Proceedings of the 22nd IIR International Congress of Refrigeration.
  • Publication date: 2007/08/21
  • Document available for consultation in the library of the IIR headquarters only.


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