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Comparative thermodynamic performance analysis of a cascade system for cooling and heating applications

Yilmaz, Fatih, Selbaş, Reşat
International journal of green energy 2019 v.16 no.9 pp. 674-686
carbon dioxide, cooling, exergy, heat, heat exchangers, temperature
In this study, a comparative thermodynamic performance analysis of cascade system (CCS) for cooling and heating applications is presented and compared for different refrigerant couples. The CCS consists of the low-temperature cycle (LTC) and high-temperature cycle (HTC). The CO₂ was used as working fluid in LTC, whereas the HFE 7000, R134a, R152a, R32, R1234yf, and R365mfc refrigerants were used in HTC. The heating and cooling coefficients of performance (COPₕₜ, COPcₗ) and exergy efficiency of CCS are investigated parametrically according to various factors such as the evaporator, condenser, and reference temperatures. After thermodynamic analyses are completed, the COPcₗ of CCS is obtained as 1.802, 1.806, 1.826, 1.769, 1.777, and 1.835 for CO₂-HFE7000, CO₂-R134a, CO₂-R152a, CO₂-R32, CO₂-R1234yf, and CO₂-365mfc refrigerant couples, respectively. Furthermore, the heat exchanger has the highest exergy destruction rate, whereas the expansion valves have the lowest of exergy destruction rate.