Chapter 19, Problem 32P

Consider a Carnot engine operating between temperatures T_h, and T_i, where T_i is intermediate between T_h and the ambient temperature T_c (Fig. 19.21). It should be possible to operate a second engine between T_h and T_c. Show that the maximum overall efficiency of such a two-stage engine is the same as that of a single engine operating between T_h, and T_c (which is why combined-cycle power plants achieve high efficiencies).

FIGURE 19.21 Problem 32