A Carnot heat engine, shown in Fig P7.76, receives energy from a reservoir at Tres through a

Question:

A Carnot heat engine, shown in Fig P7.76, receives energy from a reservoir at Tres through a heat exchanger where the heat transferred is proportional to the temperature difference as Q.H = K (Tres - TH). It rejects heat at a given low temperature TL. To design the heat engine for maximum work output show that the high temperature, TH, in the cycle should be selected as TH = TresTL