Cut-off temperature evaluation and performance comparison from energetic and exergetic perspective for NH3-H2O absorption refrigeration system

Abstract

This study represents the thermodynamic analysis and optimization of single effect aqua-ammonia absorption cooling system. Mathematical models are derived from thermodynamic theory to compute the optimum performance parameters. Cut-off temperature to operate the system is obtained at various operating temperatures. Analysis depicts that with raise in evaporator temperature from −5 to 5°C, the required cut-off temperature decreased from 72°C to 59°C. Through realistic comparison between thermodynamic first and second law analysis, optimum generator temperature corresponding to maximum COP and minimum exergy destruction is evaluated. It is found that the optimum generator temperature corresponding to exergy approach is 11°C lower as compared to energy approach. Optimum generator temperature is a strong function of evaporator and condenser temperature. Hence, it is feasible to determine optimum generator temperature for certain range of evaporator and condenser temperatures. Contours of optimum generator temperature for various combinations of condenser and absorber temperatures are presented.