Performance characteristics of ejector expander transcritical CO₂ refrigeration cycle

Abstract

The effects on the performance of the basic CO 2 refrigeration cycle when using an ejector as the expander to recover expansion work were investigated. A two-phase constant area ejector flow model was used in the ejector analysis. The coefficient of cooling performance and gas cooler pressure that yielded the maximum exergy efficiency, suction nozzle pressure drop, and optimum values for the ejector area ratio were determined for various evaporator and gas cooler outlet temperatures. Parametric studies were performed using engineering equation solver. The suction nozzle pressure drop had a significant effect on the ejector area ratio, coefficient of cooling performance, and exergy efficiency. It is necessary to design an ejector with the optimum area ratio to achieve the optimum pressure drop and maximum performance. Cycle that use the ejector as an expander always has higher coefficient of performance and exergy efficiency than conventional cycle under any operating condition. The irreversibility decreases compared to the classic refrigeration cycle when the ejector or turbine are used as an expander. The analysis results showed that -under a gas cooler pressure of 9.5 MPa, gas cooler outlet temperature of 40 C, evaporator temperature of 5 C, and cooling capacity of 3.5 kW -the total irreversibility of the ejector system was lower than those of the basic and turbine expander systems by 39.1% and 5.46%, respectively.

Energetic and Exergetic Analysis of an Ejector-Expansion Refrigeration Cycle Using the Working Fluid R32

“…This implies that the EECs of the two refrigerants all have an optimum SNPD that leads to a maximum COP for fixed condensing and evaporating temperatures. This general trend is consistent with the published literatures [19,[24][25][26]. The same inclination also can be seen for the VCC of the EEC versus the SNPD.…”

Investigation of ejector-equipped Joule–Thomson refrigerator operating below 77 K

“…The pressure drop of the refrigerant flow is taken into account only at the expansion valve. Finally, the efficiency of the ejector-JT refrigeration cycle is calculated from the definition of COP (coefficient of performance: cooling load / compression work) and the exergy efficiency (COP/COP ideal ) where COP ideal is the Carnot efficiency (Ersoy and Bilir, 2012).…”

Energy and Environmental Assessment of Co2 Booster Refrigeration Cycles With Flooded Evaporators and Parallel Compressor for Supermarkets in Türki̇ye

“…However, CO2 refrigeration systems have some difficulties such as higher equipment costs because of CO2's high working pressures (Goetzler et al, 2014) and critical temperature of CO2 which is 30.98 ℃ causing CO2 systems to operate transcritical (heat rejection at supercritical zone). In the literature review, there are studies dealing with the use and improvement of CO2 refrigeration systems both theoretically (Ersoy and Bilir, 2012;Ge et al, 2015;Gullo and Hafner, 2017;Mylona et al, 2017;Sarkar and Agrawal, 2010;Sawalha, 2008aSawalha, , 2008b and experimentally (Chesi et al, 2014;Fricke et al, 2016;Fritschi et al, 2017;Llopis, Sanz-Kock, et al, 2015;Nebot-Andrés et al, 2021). Alongside these studies focusing on the improvement of the systems, there are also city-based studies (Cui et al, 2020;Gullo et al, 2016;Işık, 2022;Karampour and Sawalha, 2018;Lata et al, 2021;Mitsopoulos et al, 2019;Sooben et al, 2019;Tsamos et al, 2017) to show the outcomes when they are used in supermarkets in daily operations.…”