Exergy calculations and refrigerant selection using flue gas waste heat in organic rankine cycle

Abstract

In this study, the second law efficiency of the organic Rankine cycle (ORC) designed was calculated for each of refrigerants, and the exergies of the ORC components were examined separately. Candidate refrigerants were determined for comparison. When determining candidate refrigerants, the first thing to consider was the low boiling point temperature. Five candidate refrigerants were determined for comparison purposes, namely R290, R600a, R32, R125, R143a. When determining candidate refrigerants, importance was given to the criterion that their boiling temperature should be lower than the boiling temperature of water. The refrigerant with the highest exergy efficiency was selected as the most suitable refrigerant among the candidate refrigerants. The temperature of sink has been taken as a value that lower than the boiling point temperature o the refrigerant that has the lowest boiling point temperature among the others instead of ambient temperature.The power generation, first law efficiency and second law efficiency of R32were found to be 170,3 kJ/kg, 0,3049 and 0,284, respectively.The thermal efficiency and second law efficiency values of the ORC using R32 are higher than those using other refrigerants for conditions in the considered textile plant.