Conventional and advanced exergy analyses of an air-conditioning system in a subway station

Air-conditioning systems in subway stations consume a large amount of energy. In this study, conventional and advanced exergy analyses were carried out to determine the energy-saving potential of an air-conditioning system in a subway station. Results show that air handling unit (AHU) should be improved for the highest values of relative irreversibility (RI) with conventional exergy analysis, whereas the compressor should have the highest improvement priority for the largest avoidable exergy destruction with advanced exergy analysis. Moreover, influences of compressor efficiency, condensation temperature, and evaporation temperature on avoidable exergy destruction of the air-conditioning system were also investigated. According to the findings, compressor efficiency significantly influences the system's total avoidable exergy destruction. The lower the compressor efficiency, the more rapidly the avoidable exergy destruction of the compressor increases. Furthermore, the avoidable exergy destruction of condenser, compressor, cooling tower (CT), and cooling water pump (CWP) increases with the rise of the condensation temperature, whereas that of the evaporator, throttling valve (TV), condenser, compressor, CT, and CWP decreases with the rise of the evaporation temperature.