Optimization and comprehensive exergy-based analyses of a parallel flow double-effect water-lithium bromide absorption refrigeration system

Highlights: • Advanced exergy analysis is applied to a parallel flow double-effect H₂O-LiBr absorption chiller. • Endogenous/exogenous and avoidable/unavoidable irreversibilities are calculated. • System performance is optimized for maximum COP and exergy efficiency using the Golden Section method. • Effects of operating conditions on COP and exergy efficiency of the system are examined. • Real potential priorities for possible improvements of the system and its components are identified. -- Abstract: In this paper, a parallel flow double-effect water-lithium bromide absorption refrigeration cycle is investigated using comprehensive exergy-based analyses. The exergy destruction of each device is calculated and used for further analysis. The performance of the system is optimized for maximum coefficient of performance and exergy efficiency, considering the distribution ratio as a variable using the Golden Section method. The maximum coefficient of performance, i.e. 1.295, is obtained at a high pressure generator temperature of 169.6 °C, and the maximum exergy efficiency, i.e. 0.225, is obtained at a high pressure generator temperature of 142.7 °C. Advanced exergy analysis, a state of the art thermodynamic method, is employed for diagnosing equipment and cycle malfunctions. Not only can the aforementioned analysis pinpoint the source of irreversibility, it also provides the avoidable irreversibility as well. The results show that the endogenous part of the exergy destruction is much larger than the exogenous part, implying it is better to focus on component efficiencies to improve system performance. Moreover, the unavoidable part of the total exergy destruction is much larger than the avoidable portion, indicating that exergy destruction cannot be decreased owing to technical limitations of equipment.