Second law comparison of single effect and double effect vapour absorption refrigeration systems

Abstract

In this paper a comparative study between single effect and double effect absorption refrigeration systems with identical cold output is carried out. Simulation results were used to study the influence of the various operating parameters on the performance coefficient, the thermal loads of the components, exergetic efficiency (rational efficiency) and the total change in exergy of the two systems. It is concluded that the COP of double effect system is approximately twice the COP of single effect system but the exergetic efficiency of double effect system increase slightly compared to the exergetic efficiency of single effect system. It is found that for each condenser and evaporator temperature, there is an optimum generator temperature where the total change in exergy of the single effect and double effect absorption refrigeration systems is minimum. At this point the COP and exergetic efficiency of the systems become maximum. In this study and when the evaporation temperature is varied from 4 °C to 10 °C, condenser and absorber temperatures are varied from 33 °C to 39 °C and generator (HPG) temperature is varied from 60 °C to 190 °C the maximum COP values of the single effect refrigeration systems are in the range of 0.73–0.79 and for double effect refrigeration systems are in the range of 1.22–1.42. The maximum exergetic efficiency values of the single effect refrigeration systems are in the range of 12.5–23.2% and for double effect refrigeration systems are in the range of 14.3–25.1%.