Dead state reference datum

Before proceeding to the criteria for practical selection of the dead state reference datum for analyzing a particular process, some background fundamentals will be presented. 

Proper choice of a reference datum (a dead state) is important to efficiency analysis and costing. It needs to be recognized that the reference datum for available energy is an altogether different concept than the reference base for property tabulations. 

Some contend that the chemical reference datum for available energy can also be selected arbitrarily, just like a base for thermochemical tables (while admitting that the thermal reference datum—the "dead state temperature"—is not arbitrary). The contention is erroneous changing the various values of the available energy of a specific material by a constant amount (as a consequence of changing the reference datum) leads to misconceptions, to misevaluations, and to misallocations—in the determination of inefficiencies and costs. Absolute values of available energy can and should be evaluated. 

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