According to the lawof thermodynamics, exergy can reflect both quality and quantity of energy and exergy destruction can express the irreversibility of heat transfer process. Bejan [28] discussed the concept of irreversibility. He overviewed the fundamentals of exergy analysis, entropy generation minimization and summarized the thermodynamic optimization. Wang et al. [29] derived a phenomenological equation of exergy transfer by applying nonequilibrium thermodynamics to the second law analysis, which indicated the relation between exergy flux, exergy resistance and exergy driving forces. Wu et al. [30,31] researched the exergy transfer characteristics of fluid flow and heat transfer inside a circular duct under fully developed laminar and turbulent forced convection with constant wall temperature and heat flux. They proposed the local and mean exergy transfer Nusselt number, and demonstrated the effect of different parameters on the convective
exergy transfer characteristics. Most of the exergy analyses are conducted on the system level development. And the optimization are conducted by analysing the exergy values or changes of component input and output streams as well as energy interactions. It is meaningful to develop a method to optimize the convective heat transfer through the analysis of local exergy destruction.