Here, the engine 1 is the one cycle engine, and the engines 2 and 3 make the two cycle engine where there is the intermediate reservoir at T 2. We also have used the fact that the heat q 2 passes through the intermediate thermal reservoir at T 2 without losing its energy. (I.e., q 2 is not lost during its passage through the reservoir at T 2 .) This fact can be proved by the following.