ISI BILIMI VE TEKNIGI DERGISI-JOURNAL OF THERMAL SCIENCE AND TECHNOLOGY, cilt.34, ss.9-18, 2014 (SCI İndekslerine Giren Dergi)
In this study, energy and exergy analysis of compression-absorption cascade refrigeration cycles were performed. In order to determine the best suitable working pair in the absorption section of the cascade refrigeration system, LiBr-H2O and NH3-H2O pairs were compared by considering only R134a in the vapour compression section. In the case of using LiBr-H2O fluid couple in the absorption section of cascade refrigeration cycles, the coefficient of performance (COP) is 27% higher and total exergy destruction rate is 20% lower compared with the case of using NH3-H2O fluid couple. Based on these results, the first and second law thermodynamic analyses were carried out for different working temperatures of the system components by using only LiBr-H2O in the absorption section and using various refrigerants, namely NH3, R134a, R410A and CO2, in the vapor compression section. The results show that the COP of the cascade system increases by increasing the generator and evaporator temperatures, while it decreases by increasing the condenser and absorber temperatures. However, the exergetic efficiency decreases with increasing generator, absorber and condenser temperatures. Moreover, it was determined that NH3/LiBr-H2O cascade cycle has the best thermodynamic performance, while CO2/LiBr-H2O cascade cycle has substantially poorer performance than this cycle.