Finite time thermodynamic analysis of an irreversible vapour absorption refrigeration system using Langrangian multiplier method

Abstract

This paper presents an optimization of irreversible vapour absorption refrigeration (VAR) system on the basis of finite time thermodynamic approach. The complete VAR system is considered to be consisting of two sub-systems. One sub-system (generator-absorber assembly) is assumed as an irreversible heat engine whereas another subsystem (evaporator-condenser assembly) is assumed as an irreversible refrigeration cycle. The objective functions considered for optimization are thermal efficiency of heat engine cycle and COP of refrigeration cycle. Langrangian multiplier method has been applied to optimize these objective functions with respect to source/sink side heat exchanger areas. Two internal irreversibility coefficients (ΨS and Ψ’S) are introduced to analyze the effect of external and internal irreversibility on performance of VAR system. Results show that effect of internal irreversibility variation is more dominant on performance deviation of system. Further, it is also established that out of these two internal irreversibility coefficients, Ψ’S for evaporator-condenser assembly has more impact on overall COP of VAR system then internal irreversibility coefficient, ΨS for generator-absorber assembly.