Exergy Analysis Framework for Underground Transportation Systems

The environmental problems are mainly consequences from a too strong belief in traditional engineering and economic growth as the solution. An important human step against ignorance should be to understand that the real world processes involving energy and matter need to be linked to the environmental engineering education, design and operation. Energy systems involving coversion chain processes are highly irreversible and, consequently, they could have low exergy efficiencies. This study aimed at examining an underground railway train as a system where different energy forms occur, so that the successive energy conversion chain is emphasized and the energy and exergy efficiencies, respectively, are compared. Also, because at low speed the mechanical brake can't be avoid, among the environment issues, from viewpoint of exergy efficiency, a special aspect is represented by an abnormal but frequent situation of train operation, concerning the unequal charge of the traction induction motors. In this application there are presented numerical simulations and experimental data related to unequally charged motors regime. The exergy analysis can help improve and optimize the underground transportation system design and operation, but also represents an environmental engineering education example.