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Trade-offs between design complexity and performance impacts for transcritical R744 ejectors.

Number: pap. 0031

Author(s) : BOTTICELLA F., LIU Z., ELBEL S.

Summary

It is well known that the transcritical CO2 cycle has higher intrinsic throttling losses than comparable subcritical cycles. Replacing the expansion valve with a two-phase ejector greatly improves cycle performance by reducing throttling losses. However, ejectors have yet to be successfully applied to low-capacity systems (approximately 1 to 5 kW), such as bottle coolers, window air conditioners, beverage dispensers, heat pump water heaters or similar. It is a real challenge to integrate ejectors into mass produced systems of small capacity in a cost-effective manner due to the relatively complex design of an ejector in comparison to simpler expansion devices. In addition to presenting system level results obtained with a transcritical CO2 bottle cooler with ejector, another aim of this paper is to systematically determine the possibilities for cost reduction by identifying performance trade-offs of less complex ejector designs. In a first step, a simplified diffuser design was investigated in combination with a conventional motive nozzle having converging-diverging design. Resulting system COPs and the impact on ejector efficiency are reported.

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Pages: 8

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Details

  • Original title: Trade-offs between design complexity and performance impacts for transcritical R744 ejectors.
  • Record ID : 30025702
  • Languages: English
  • Source: 8th Conference on Ammonia and CO2 Refrigeration Technology. Proceedings: Ohrid, North Macedonia, Avril 11-13, 2019.
  • Publication date: 2019/04/11
  • DOI: http://dx.doi.org/10.18462/iir.nh3-co2.2019.0031

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