Experimental study on control methods for transcritical CO2 two-phase ejector systems at off-design conditions

N. Lawrence, S. Elbel

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Recent studies have shown that expansion work recovery by use of a two-phase ejector offers significant opportunity for improving the COP of refrigeration systems, especially transcritical CO2 systems. However, performance improvement is known to be less significant at off-design conditions that are not as favorable to the ejector cycle. This paper investigates methods for controlling the high-side pressure of a transcritical CO2 ejector cycle. The use of an ejector with an adjustable motive nozzle throat area as well as a simple expansion valve upstream of the ejector to actively control high-side pressure are investigated and compared experimentally. Proper control of evaporator flow rate for different conditions is also investigated, and the penalty for not actively controlling the evaporator metering valve is also investigated. The control methods are investigated over a range of capacities and ambient temperatures in order to see the performance penalties to a transcritical CO2 ejector cycle when it is not controlled properly.

Original languageEnglish (US)
Title of host publication12th IIR Gustav Lorentzen Natural Working Fluids Conference, GL 2016
PublisherInternational Institute of Refrigeration
Pages511-518
Number of pages8
ISBN (Electronic)9782362150180
DOIs
StatePublished - 2016
Event12th IIR Gustav Lorentzen Natural Working Fluids Conference, GL 2016 - Edinburgh, United Kingdom
Duration: Aug 21 2016Aug 24 2016

Publication series

NameRefrigeration Science and Technology
ISSN (Print)0151-1637

Other

Other12th IIR Gustav Lorentzen Natural Working Fluids Conference, GL 2016
Country/TerritoryUnited Kingdom
CityEdinburgh
Period8/21/168/24/16

Keywords

  • Adjustable ejector
  • Capacity modulation
  • Carbon dioxide
  • High-side pressure control
  • Two-phase ejector

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Electrical and Electronic Engineering
  • Mechanical Engineering
  • Condensed Matter Physics

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