Measurement of oil in circulation in transcritical R744 systems using two-phase ejector

Jingwei Zhu, Francesco Botticella, Stefan Elbel

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

Abstract

The use of two-phase ejectors to recover expansion work to improve COP of transcritical R744 systems has been the subject of numerous investigations during the past decade. However, there is little understanding as to how oil in circulation in different parts of the system is affected when a two-phase ejector is used to replace the expansion valve. This paper presents detailed measurement results conducted on a transcritical R744 ejector system using polyalkylene glycol (PAG) oil, demonstrating that at the same test condition, the oil circulation rates (OCRs) in different parts of the system can easily vary by an order of magnitude. The highest OCRs of approximately 10% by mass were measured close to the evaporator inlet. The influence of compressor speed, ejector motive nozzle needle position and evaporator inlet metering valve opening on the OCRs was investigated and it is explained why these condition changes will result in variation of oil in circulation.

Original languageEnglish (US)
Title of host publication13th IIR Gustav Lorentzen Conference on Natural Refrigerants
Subtitle of host publicationNatural Refrigerant Solutions for Warm Climate Countries, Proceedings
PublisherInternational Institute of Refrigeration
Pages247-254
Number of pages8
ISBN (Electronic)9782362150265
DOIs
StatePublished - 2018
Event13th IIR Gustav Lorentzen Conference on Natural Refrigerants: Natural Refrigerant Solutions for Warm Climate Countries - Valencia, Spain
Duration: Jun 18 2018Jun 20 2018

Publication series

NameRefrigeration Science and Technology
Volume2018-June
ISSN (Print)0151-1637

Other

Other13th IIR Gustav Lorentzen Conference on Natural Refrigerants: Natural Refrigerant Solutions for Warm Climate Countries
CountrySpain
CityValencia
Period6/18/186/20/18

Keywords

  • Carbon dioxide
  • Ejector
  • Oil in circulation
  • Performance
  • Two-phase

ASJC Scopus subject areas

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

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