On illustrating Carnot’s general proposition by means of reversible Stirling engines

Carnot’s general proposition, also referred to as one of Carnot’s principles, states that the work producing potential of heat—harvested by reversible heat engines—is independent of the working fluid and of engine internal details, being only a function of the temperatures of the reservoirs with which the engine exchanges heat. This concept, usually presented in introductory thermodynamics courses to ME students in the context of the second law of thermodynamics before entropy is introduced, is customarily proven by contradiction, i.e., by a violation of the second law, using second law concepts and abstractions such as ‘thermal reservoirs’ and ‘reversible engines’, without concrete examples, even though Carnot’s proposition mentions concrete things such as working fluids and engine internal details. This work proposes to document the usage of different reversible Stirling engine models that take the engine arrangement down to engine constructive parameters, crankshaft angles, and the like, as well as fluid properties into account towards illustrating the validity of Carnot’s general proposition without using entropy.