Availability in a finite process

Let x-y be a finite process in which heat is supplied reversibly to a heat engine. Taking an elementary cycle, let dQ₁ be the heat received by the engine reversibly at temperature T₁. Then

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For the whole process x-y,

Fig. 1.24 Unavailable energy by 2 nd law of thermodynamics

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Hence, maximum work obtainable is

UE = Qx - y - Wmax

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UE = T0(sy - sx)

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