Optimization of a double effect LiBr-H2O absorption system

Abstract

A computer program is developed to optimize a double-effect LiBr-H₂O absorption refrigeration system. Optimum coefficient of performance (COP) of the refrigeration system is sought for a fixed cooling load capacity of a system and fixed upper cycle pressure (pressure of Generator 1) and lower cycle pressure (pressure of Evaporator Absorber). For any fixed upper cycle pressure and lower cycle pressure, the intermediate pressure (pressure of Condenser/ Generator 2) of the system is varied until the optimum COP is obtained.

The effect of increasing of the temperature of Generator 1 on the COP of the system is also analysed. Pure water vapor is considered to be generated in both generators at the respective prevailing pressure and temperature combinations. Specific enthalpies of pure water vapor at outlet from the respective generators and the condensate water leaving the Condenser are automatically determined by the developed programme at the prevailing saturation temperatures. Concentrations at all state points in the cycle are also obtained from the programme at the respective state point pressure and temperature values. In the analysis, steady-state conditions and no pressure losses are assumed. The effect of the effectiveness of the heat exchangers on the COP of the system are also analysed using the developed program.