Pitfalls of Exergy Analysis
Abstract
The wellknown GouyStodola theorem states that a device produces maximum useful power when working reversibly, that is with no entropy production inside the device. This statement then leads to a method of thermodynamic optimization based on entropy production minimization. Exergy destruction (difference between exergy of fuel and exhausts) is also given by entropy production inside the device. Therefore, assessing efficiency of a device by exergy analysis is also based on the GouyStodola theorem. However, assumptions that had led to the GouyStodola theorem are not satisfied in several optimization scenarios, e.g. nonisothermal steadystate fuel cells, where both entropy production minimization and exergy analysis should be used with caution. We demonstrate, using nonequilibrium thermodynamics, a few cases where entropy production minimization and exergy analysis should not be applied.
 Publication:

Journal of Non Equilibrium Thermodynamics
 Pub Date:
 April 2017
 DOI:
 10.1515/jnet20160043
 arXiv:
 arXiv:1611.01410
 Bibcode:
 2017JNET...42..201V
 Keywords:

 exergy analysis;
 nonequilibrium thermodynamics;
 fuel cells;
 optimization;
 entropy production minimization;
 Physics  Chemical Physics
 EPrint:
 Accepted to Journal of Nonequilibrium thermodynamics