Review of the Second Carnot Principle
2nd Carnot Principle
:All reversible power cycles operating between the same two thermal reservoirs have the same efficiency.
The thermal efficency of a reversible thermodynamic cycle:
- does not depend on the working fluid or its properties
- but only on the temperatures of the two thermal resevoirs.
We learned how to calculate η in Chapter 5:

Now, based on the 2nd Carnot Principle, we expect to find an equation that relates the thermal efficiency of a HE to the temperatures of the two reservoirs:
η = fxn( TH , TC )
We begin this lesson by determining the function that relates η to TC and TH.
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