Comprehensive experimental performance study on a small-capacity transcritical R744 vapour-compression refrigeration unit equipped with an innovative ejector: Etude expérimentale complète des performances d'un groupe frigorifique à compression de vapeur transcritique R744 de petite capacité équipé d'un éjecteur innovant

Paride Gullo*, Michael Birkelund, Ekaterini E. Kriezi, Martin Ryhl Kærn

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

Ejector-equipped transcritical R744 condensing units are believed to lead to a low-to-zero commercial refrigeration sector. In order to overcome the persisting barrier to their wider adoption represented by the lack of an affordable ejector control technique, the novel pulse-width modulation (PWM) ejector, being low cost, simple and invulnerable to clogging was recently implemented. However, additional experimental evaluations are needed. Therefore, in this experimental work the performance of two PWM ejector-equipped transcritical R744 condensing units, i.e. with and without overfed evaporator, was carried out. The experimental assessment was implemented at the medium temperature (MT) of about -5°C, heat sink temperatures from 30°C to 40°C and compressor speeds from 40 Hz to 60 Hz.

The outcomes obtained revealed that the PWM ejector can effectively control the high pressure in transcritical operating conditions, regardless of the selected heat sink temperature and compressor speed. In addition, at the same cooling capacity, the PWM ejector-equipped R744 system was found to permit energy savings between 7.0 % and 11.1 % without overfed evaporator and between 11.5 % and 16.3 % with overfed evaporator compared to the standard R744 unit (i.e. with vapour by-pass valve and without ejector), respectively. Finally, higher values of coefficient of performance (COP) were found to be offered by the PWM ejector compared with its today's available competitors
Original languageEnglish
JournalInternational Journal of Refrigeration
Volume152
Pages (from-to)192-203
ISSN0140-7007
DOIs
Publication statusPublished - 2023

Keywords

  • CO2
  • Condensing unit
  • Cooling
  • Expansion work recovery
  • Flow modulation
  • Overfed evaporator
  • Modulation de débit
  • Refroidissement
  • Récupération des travaux d'agrandissement
  • Unité de condensation
  • Évaporateur suralimenté

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