A body of finite mass is originally at temperature T1, which is higher than that of a reservoir at temperature T2. Suppose an engine operates in a cycle between the body and the reservoir until it lowers the temperature of the body from T1 to T2, thus extracting heat Q from the body. If the engine does work W, then it will reject heat Q-W to the reservoir at T2. Applying the entropy principle, prove that the maximum work obtainable from the engine is
W (max) = Q - T2 (S1- S2)
Where S1- S2is the entropy decrease of the body.
If the body is maintained at constant volume having constant volume heat capacity Cv = 8.4 kJ/K which is independent of temperature, and if T1 = 373 K and T2 = 303 K, determine the maximum work obtainable.