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International Journal of Aerospace Engineering
Volume 2009, Article ID 409529, 11 pages
Research Article

Benefits of Exergy-Based Analysis for Aerospace Engineering Applications—Part I

1Department of Engineering Management & Systems, The University of Dayton, Dayton, OH 45469, USA
2Multidisciplinary Science & Technologies Center, U.S. Air Force Research Laboratory, Wright-Patterson AFB, OH 45433, USA

Received 11 March 2009; Revised 15 September 2009; Accepted 23 October 2009

Academic Editor: Victor Giurgiutiu

Copyright © 2009 John H. Doty et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


This paper compares the analysis of systems from two different perspectives: an energy-based focus and an exergy-based focus. A complex system was simply modeled as interacting thermodynamic systems to illustrate the differences in analysis methodologies and results. The energy-based analysis had combinations of calculated states that are infeasible. On the other hand, the exergy-based analyses only allow feasible states. More importantly, the exergy-based analyses provide clearer insight to the combination of operating conditions for optimum system-level performance. The results strongly suggest changing the analysis/design paradigm used in aerospace engineering from energy-based to exergy-based. This methodology shift is even more critical in exploratory research and development where previous experience may not be available to provide guidance. Although the models used herein may appear simplistic, the message is very powerful and extensible to higher-fidelity models: the 1st Law is only a necessary condition for design, whereas the 1st and 2nd Laws provide the sufficiency condition.