Entropy production diagrams

In a recent Note,¹ the entropy production in a process of thermalization between a system and a heat reservoir was depicted graphically for given initial temperatures $T1<T2$⁠. The process may occur via heating the system or by cooling it, depending on how the temperatures are assigned to the system and the reservoir. A simple extension of this Note considers a cyclic process involving two heat reservoirs, where the system, initially in equilibrium with the reservoir at temperature $T1$⁠, undergoes heating followed by cooling (⁠ $1→2→1$⁠). In each iteration of the cycle, an amount of heat $Q=C(T2−T1)>0$ is transferred from the reservoir 2 to reservoir 1. Then, the total entropy production is the sum of contributions from each process and is depicted by the area of the rectangle (Fig. 1, Ref. 1) with sides $[C/T2,C/T1]$ and $[T1,T2]$⁠, given by which, as expected, yields the entropy produced if Q amount of heat flows from reservoir 2 to reservoir 1.