Abstract
The paper presents to discuss a historical evolution process of the primitive Carnot cycle to the modernized understandings, through which some prevalently accepted ideas and concepts embodied in the modern thermodynamics are also re-examined. Subsequently, the more detailed speculations on the modern Carnot cycle are exhibited, particularly, on the designated temperatures during isothermal processes from the viewpoint of energy conversion between heat and mechanical work and, further, extended to discuss the relations of more generalized thermal cycles including the polytropic changes as well as the related thermodynamics noticing the rigorous systematic understanding on the thermal cycles and the efficiencies.
