THERMAL SCIENCE

International Scientific Journal

NUMERICAL INVESTIGATION OF AN R744 LIQUID EJECTOR FOR SUPERMARKET REFRIGERATION SYSTEMS

ABSTRACT
This paper presents a numerical investigation of an R744 liquid ejector applied to a supermarket refrigeration system. The use of the liquid ejector enables the operation of the evaporator in a flooded mode and recirculates the R744 liquid phase, which improves the energy efficiency of the refrigeration system. The investigation was performed using two ejectors of different sizes installed in a multi-ejector block. The numerical model was formulated based on the homogenous equilibrium model and validated with the experimental results. The influence of the pre-mixer, mixer and diffuser dimensions on the ejector performance measured using the mass entrainment ratio is presented. The results show that the best liquid ejector performance was obtained for the short lengths of the pre-mixer and mixer compared to the broadly investigated two-phase ejectors connected to the evaporator port. In addition, wide diffuser angles improved the mass entrainment ratio of both liquid ejectors, which may lead to a reduction in the diffuser length.
KEYWORDS
PAPER SUBMITTED: 2015-12-10
PAPER REVISED: 2016-03-02
PAPER ACCEPTED: 2016-04-06
PUBLISHED ONLINE: 2016-05-08
DOI REFERENCE: 10.2298/TSCI151210112H
CITATION EXPORT: view in browser or download as text file
THERMAL SCIENCE YEAR 2016, VOLUME 20, ISSUE 4, PAGES [1259 - 1269]
REFERENCES
  1. Deng, J. q., et al., Particular Characteristics of Transcritical CO2 Refrigeration Cycle With an Ejector, Applied Thermal Engineering, 27 (2007), 2-3, pp. 381-388, DOI No. 10.1016/j.applthermaleng.2006.07.016
  2. Elbel, S., Historical and Present Developments of Ejector Refrigeration Systems with Emphasis on Transcritical Carbon Dioxide Air-conditioning Applications, International Journal of Refrigeration-Revue Internationale Du Froid, 34 (2011), 7, pp. 1545-1561, DOI No. 10.1016/j.ijrefrig.2010.11.011
  3. Elbel, S., Hrnjak, P., Experimental Validation of a Prototype Ejector Designed to Reduce Throttling Losses Encountered in Transcritical R744 System Operation, International Journal of Refrigeration-Revue Internationale Du Froid, 31 (2008), 3, pp. 411-422, DOI No. 10.1016/j.ijrefrig.2007.07.013
  4. Hafner, A., et al., Multi-ejector Concept for R-744 Supermarket Refrigeration, International Journal of Refrigeration-Revue Internationale Du Froid, 43 (2014) pp. 1-13, DOI No. 10.1016/j.ijrefrig.2013.10.015
  5. Li, D., Groll, E. A., Transcritical CO2 Refrigeration Cycle with Ejector-expansion Device, International Journal of Refrigeration, 28 (2005), 5, pp. 766-773, DOI No. 10.1016/j.ijrefrig.2004.10.008
  6. Sumeru, K., et al., A Review on Two-phase Ejector as an Expansion Device in Vapor Compression Refrigeration Cycle, Renewable & Sustainable Energy Reviews, 16 (2012), 7, pp. 4927-4937, DOI No. 10.1016/j.rser.2012.04.058
  7. Li, Y., et al., Experimental Evaluation of an Ejector as Liquid Re-circulator in a Falling-film Water Chiller, International Journal of Refrigeration, 40 (2014), pp. 309-316, DOI No. 10.1016/j.ijrefrig.2013.11.001
  8. Dopazo, J. A., Fernández-Seara, J., Experimental Evaluation of an Ejector as Liquid Re-circulator in an Overfeed NH3 System With a Plate Evaporator, International Journal of Refrigeration, 34 (2011), 7, pp. 1676-1683, DOI No. 10.1016/j.ijrefrig.2010.12.023
  9. Girotto, S., CO2 Refrigeration System for Warm Climates, Enex srl, 2013, Padernello di Paese, www.enex-ref.com/download/Enjector_promo_eng.pdf
  10. Girotto, S., Benefits With Enjector, Enex srl, 2013, Padernello di Paese, www.enex-ref.com/download/Enjector_promo_eng.pdf
  11. Banasiak, K., et al., Development and Performance Mapping of a Multi-ejector Expansion Work Re-covery Pack for R744 Vapour Compression Units, International Journal of Refrigeration, 57 (2015), pp. 265-276, DOI No. 10.1016/j.ijrefrig.2015.05.016
  12. Smolka, J., et al., A Computational Model of a Transcritical R744 Ejector Based on a Homogeneous Real Fluid Approach, Applied Mathematical Modelling, 37 (2013), 3, pp. 1208-1224, DOI No. 10.1016/j.apm.2012.03.044
  13. Palacz, M., et al., Application Range of the HEM Approach for CO2 Expansion Inside Two-phase Ejec-tors for Supermarket Refrigeration Systems, International Journal of Refrigeration, 59 (2015), pp. 251-258, DOI No. 10.1016/j.ijrefrig.2015.07.006
  14. Hafner, A., et al., R744 Refrigeration System Configurations for Supermarkets in Warm Climates, in: 3rd IIR International Conference on Sustainability and the Cold Chain, ICCC 2014, International Insti-tute of Refrigeration, 2014
  15. Lemmon, E. W., et al., M.O., NIST Standard Reference Database 23: Reference Fluid Thermodynamic and Transport Properties-REFPROP, Standard Reference Data Program, 2013

© 2017 Society of Thermal Engineers of Serbia. Published by the Vinča Institute of Nuclear Sciences, Belgrade, Serbia. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International licence