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ABSTRACT
In this paper, the performance characteristics of an ejector-expansion refrigeration cycle using six low GWP alternative refrigerants for R134a are presented through the first and second laws of thermodynamics. The ejector is modelled by assuming a constant-mixing pressure. The investigated refrigerants are compared based on the optimum ejector area ratio, discharge temperature, volumetric cooling capacity (VCC), coefficient of performance (COP) and exergy efficiency (ηex). The drop-in analysis is considered based on the same operating/designing parameters, and the VCC, COP and ηex improvements over the conventional refrigeration cycle are presented. The improvements in COP and VCC are between 7.914%–18.46% and 5.712%–22.82%, respectively, for the investigated range of evaporating and condensing temperatures. These values are higher than that of R134a by about 21% and 16%, respectively. The VCC using R1234yf is very close to R134a with a maximum reduction of 6.5%. Therefore, R1234yf refrigerant appears to be the best alternative to R134a in an ejector-expansion system with an appreciable COP and ηex devaluation. R152a outperforms R134a in terms of COP and ηex, thus it is a suitable alternative to R134a except for safety.
Data Availability Statement
The data that support the findings of this study are available from the corresponding author, upon reasonable request.
Acknowledgments
We would like to thank our Institutions “University of Al-Qadisiyah” and “Al-Furat Al-Awsat Technical University” for their support and for giving us the time for writing and completing the present study.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Nomenclature
| A | = | Area (m2) |
| COP | = | Coefficient of performance |
| CR | = | Compression ratio |
| h | = | Specific enthalpy (kJ/kg) |
| m | = | Mass flow rate (kg/s) |
| P | = | Pressure (MPa) |
| PLR | = | Pressure lift ratio |
| q | = | Cooling capacity (kJ/kg) |
| s | = | Entropy(KJ/kg.k) |
| SNPD | = | Suction nozzle pressure drop (MPa) |
| T | = | Temperature |
| V | = | Velocity (m/s) |
| VCC | = | Volumetric cooling capacity |
| w | = | Specific work (kJ/kg) |
| x | = | Vapor quality |