ENERGY AND EXERGY ANALYSIS OF GAX AND GAX HYBRID ABSORPTION REFRIGERATION SYSTEMS

Abstract

In this work GAX and GAX hybrid aqua-ammonia absorption refrigeration cycles are studied and compared from the viewpoint of first and second laws of thermodynamics. The effect of generator temperature on COP, heat transfer rates in various components, exergetic efficiency and exergy destruction rates are evaluated. The effects of degassing range and approach temperature on COP and exergetic efficiency are studied. Comparison of hybrid and conventional GAX cycle is done and it is found that the GAX hybrid cycle has an average of 27% higher value of COP than the conventional GAX cycle. Exergy analysis is performed in order to calculate the total exergy destruction rate and to calculate the contribution of different components to the total exergy destruction. The generator temperature has more effect on exergetic efficiency than on COP for both GAX and hybrid cycles. The maximum exergy destruction occurs in desorber and absorber (as a unit component) of both the cycles while the lowest contribution belongs to the expansion valve 2. The required COP can be obtained in lower degassing range in the GAX hybrid cycle as compared to the simple GAX cycle. Therefore, GAX hybrid can operate successfully utilizing low temperature energy sources. The exergetic efficiency, like COP, attains a maximum value for a particular degassing range. Thus, increase in degassing range, always does not cause increase in COP and second law efficiency. The study shows that GAX hybrid systems are more promising than simple GAX systems.