The potential impact of the small-scale ejector on the R744 transcritical refrigeration system

Highlights: • The ejector improved the COP by 2.05% over the conventional parallel layout. • The ejector could reduce the supplied power up to 18% based on the cooling load. • 21% of the expansion work was recovered by the ejector. • Employing the ejector revealed a noticeable lack of total system exergy destruction. The evident adverse effects of climate change and the consequences of global warming has left an exigent circumstance requiring crucial actions on the applications and technology of refrigeration and air conditioning systems as it concerns its tremendous indirect contributions to greenhouse gas emissions. This field has witnessed steady expansion in recent times. The attendant high-grade energy consumption calls for pragmatic approaches to developing innovative technologies aimed at energy management and finding measures to curb global warming. This current study intends to illustrate the impact of implementing a small-size ejector profile on the R744 transcritical refrigeration system to improve the system performance by recovering some expansion work and reduce power consumption. The ejector-supported system was compared with the parallel compression concept as the baseline system and carried out at different pressure lift and exit gas cooler properties. The result indicated a COP and exergy efficiency improvement up to 2.05% and 1.92% for the set conditions respectively, while the COP could be improved to the highest of 11.22% when the system cooling load is at minimum. Moreover, the ejector played a vital role in the system input power, where up to 3.46% of the energy consumption was reduced at subcritical heat rejection conditions. Operating the system with an ejector at a lower cooling capacity allows a further 18% reduction in overall power consumption. In addition, the exergy analysis revealed a noticeable lack of total system exergy destruction by deploying the ejector in parallel with the high-pressure valve, which recovered 21% of the expansion work and saved 46% of the HPV exergy losses. Furthermore, the result exhibited a maximum system exergy loss of 7.8% at the set condition and a maximum of 13.2% total system exergy destruction rate recovered by the ejector, which depends on the cooling load.