A Novel Generator Design Utilised for Conventional Ejector Refrigeration Systems

Anas F. A. Elbarghthi, Mohammad Yousef Hdaib and Václav Dvořák
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Anas F. A. Elbarghthi: Department of Applied Mechanics, Faculty of Mechanical Engineering, Technical University of Liberec, Stdentská 1402/2, 46117 Liberec, Czech Republic
Mohammad Yousef Hdaib: Department of Applied Mechanics, Faculty of Mechanical Engineering, Technical University of Liberec, Stdentská 1402/2, 46117 Liberec, Czech Republic
Václav Dvořák: Department of Applied Mechanics, Faculty of Mechanical Engineering, Technical University of Liberec, Stdentská 1402/2, 46117 Liberec, Czech Republic

Energies, 2021, vol. 14, issue 22, 1-22

Abstract: Ejector refrigeration systems are rapidly evolving and are poised to become one of the most preferred cooling systems in the near future. CO 2 transcritical refrigeration systems have inherently high working pressures and discharge temperatures, providing a large volumetric heating capacity. In the current research, the heat ejected from the CO 2 gas cooler was proposed as a driving heating source for the compression ejector system, representing the energy supply for the generator in a combined cycle. The local design approach was investigated for the combined plate-type heat exchanger (PHE) via Matlab code integrated with the NIST real gas database. HFO refrigerants (1234ze(E) and 1234yf) were selected to serve as the cold fluid on the generator flowing through three different phases: subcooled liquid, a two-phase mixture, and superheated vapour. The study examines the following: the effectiveness, the heat transfer coefficients, and the pressure drop of the PHE working fluids under variable hot stream pressures, cold stream flow fluxes, and superheated temperatures. The integration revealed that the cold fluid mixture phase dominates the heat transfer coefficients and the pressure drop of the heat exchanger. By increasing the hot stream inlet pressure from 9 MPa to 12 MPa, the cold stream two-phase convection coefficient can be enhanced by 50% and 200% for R1234yf and R1234ze(E), respectively. Conversely, the cold stream two-phase convection coefficient dropped by 17% and 37% for R1234yf and R1234ze(E), respectively. The overall result supports utilising the ejected heat from the CO 2 transcritical system, especially at high CO 2 inlet pressures and low cold channel flow fluxes. Moreover, R1234ze(E) could be a more suitable working fluid because it possesses a lower pressure drop and bond number.

Keywords: ejector; CO 2; plate heat exchanger; refrigeration system; pressure drop (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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