Tk J

where Qk is the heat transfer rate through the boundary at temperature Tk at location k, W is the work rate, y/ is the flow exergy, s is the specific entropy, and the subscript zero indicates properties at the dead state of P0 and T0 .

The exergy destroyed or the irreversibility may be expressed as follows:

where SIgen is the rate of entropy.

Van Gool (1997) has also proposed that maximum improvement in the ex-ergy efficiency for a process or system is obviously achieved when the exergy loss or irreversibility (Exin — Exout) is minimized. Consequently, he suggested that it is useful to employ the concept of an exergetic 'improvementpotential rate' when analyzing different processes or sectors of the economy. This improvement potential in the rate form, denoted II3 , is given as (Hammond and Stapleton, 2001)

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