Exergy analysis is a powerful tool in engineering which is outcome of second law of thermodynamics. It is accepted that the reversible machines are the most efficient machines and if energy losses are stopped completely, then the process approaches towards isentropic process. Exergy analysis also helps in taking account the important engineering decisions regarding design parameters of a system. Researchers carried out exergy studies of different thermal energy conversion systems describing various approach for exergy analysis and its usefulness in a more simple and effective manner. Many researchers, engineers and scientists calculated exergy change during a flow process theoretically and compared the data with practical process and reached to conclusion and optimized the properties and parameters to obtain required output and thus the efficiency.