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A novel hybrid dual-temperature absorption refrigeration system: Thermodynamic, economic, and environmental analysis

Mohammadi, Kasra, Efati Khaledi, Mohammad Saeed, Powell, Kody
Journal of cleaner production 2019 v.233 pp. 1075-1087
absorption, capital, carbon dioxide, compressors, environmental assessment, environmental performance, evaporators, flue gas, freezing, heat, operating costs, refrigeration, steam, temperature
The applications of multi-evaporator and low temperature refrigeration systems are growing rapidly, highlighting the necessity of developing new configurations that can be economically and environmentally attractive. In this study, a hybrid dual-evaporator absorption refrigeration system for refrigerating and freezing applications is proposed and evaluated from thermodynamic, economic, and environmental viewpoints. In the proposed system, two compressors were employed between the evaporators and absorbers to increase the absorbers pressure to a higher level. The detailed parametric study results demonstrated that only employing a compressor between the higher temperature evaporator and absorber is beneficial improving the coefficient of performance (COP) significantly. However, the economic results showed that the compressor should be implemented carefully because in most design and operating conditions, the required capital and operating costs outweigh the COP improvement. Under specified design conditions, integrating the second compressor with a pressure ratio of 2.5 significantly increased the COP from 0.404 to 0.624 while it caused an increase in the unit production cost of cooling (UPCC) from $0.211/ton-hr to $0.228/ton-hr. The use of flue gas as a heat input was found to have excellent potential to improve the economic and environmental performance of the system. A detailed comparison with a dual-temperature transcritical carbon dioxide refrigeration cycle from the literature demonstrated that, under similar conditions, the system of this study has a substantially lower UPCC than the system in the literature ($0.211/ton-hr and $0.110/ton-hr for the steam and waste heat driven systems against $0.457/ton-hr). Overall, the proposed system (with and without the compressor) of this study showed an excellent potential for dual-temperature refrigeration applications.