Sensitivity analysis of avoidable and unavoidable exergy destructions in a parallel double-effect LiBr–water absorption cooling system

Abstract

A parametric study has been carried out based on advanced exergy assessment for a parallel double-effect LiBr–water absorption chiller. The advanced exergy method provides the real potential of the equipment for improvement in the system by recognizing the avoidable irreversibilities. The sensitivity analysis of various parts of the exergy destruction (endogenous avoidable, endogenous unavoidable, exogenous avoidable, and exogenous unavoidable) in system components and the overall performance (coefficient of performance, exergy efficiency, and modified exergy efficiency) of the system has been done to identify the actual potential of different components of the system to improve the overall performance of the system relative to operational parameters. Operational parameters include the heat source temperature, heat sink temperature, and the difference between the absorption and condensation temperature. The results showed that by modifying and improving the performance of components, 18.5% of the total exergy destruction of the system could be reduced. The modified exergy efficiency reduces sharply (nearly 40%) with the rising heat sink temperature. The endogenous exergy destruction increases in all system components except the condenser and evaporator by the heat source temperature increase. With the increase in the heat sink temperature, the avoidable part of the total exergy destruction in the system increases due to the significant rise in the avoidable exogenous exergy destruction in the components, and the unavoidable endogenous exergy destruction decreases (more than 200%) in the absorber. Increasing the condensation temperature reduces the unavoidable endogenous exergy destruction in the components except for the low-temperature heat exchanger.