Exergy Analysis with a Flow Sheet Program

6 Exergy Analysis with a Flow Sheet Program 

In the hypothetical case that the process is reversible in the thermodynamic sense, the flow of exergy into the system will equal the flow of exergy 

Schematic representation of the exergy flow in a separation process. 

Because chemical transformation does not occur, we do not need to include the chemical exergy in the exergy flows. We can now write expressions for the terms in the exergy balance based on 1 mol feed entering the system for both the reversible and real separation processes. 

Note that the ExQ1 and ExQ2 terms differ for the reversible and irreversible cases. The reversible case has the minimum heat input Qmm at temperature level Tb since heat is transferred reversibly without a temperature gradient. Similarly, it is rejected at Tt. It is in these two terms that the reversible and irreversible exergy balances differ. Now, first consider the reversible exergy balance, where Exlost is, by definition, equal to zero. From Equation 10.19, for the reversible case, we obtain 

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