Abstract
Though the balance of entropy has been denoted as Second Law of Thermodynamics in the previous chapters, its classical formulation comes along with thermodynamic cycles. Thus, the focus now is on these cycles. However, there are two different types of thermodynamic cycles: Clockwise cycles on the one hand convert heat into mechanical energy and are named thermal engines. Counterclockwise cycles on the other hand are fridges and heat pumps, that lift thermal energy from a lower to a higher temperature level. However, at that stage cycles are represented in a so-called black-box notation, i.e. the fluxes at its border are balanced without focussing on the detailed physical processes that run inside the machine.
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Notes
- 1.
Such a machine would be operated in steady state.
- 2.
A fictive machine, that violates the first law of thermodynamics, i.e. releases more energy than energy is supplied, is called a Perpetuum Mobile of the first kind.
- 3.
Mind, that generation of entropy is a source term, so it is going into the system!
- 4.
Both notations are equivalent and lead to the same physical interpretations. Since the machine shall be operated in steady state, the indication of the fluxes is advantageous.
- 5.
This machine is built for cooling!
- 6.
How this is realised will be clarified in part II.
- 7.
This is a Carnot-machine!
- 8.
This machine is built for heating!
- 9.
This also is a Carnot-machine!
- 10.
Only by doing so, heat can be lifted against the temperature gradient, as the entropy balance has shown!
- 11.
In case the Carnot machine is realised by a closed system!
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Schmidt, A. (2019). Second Law of Thermodynamics. In: Technical Thermodynamics for Engineers. Springer, Cham. https://doi.org/10.1007/978-3-030-20397-9_15
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DOI: https://doi.org/10.1007/978-3-030-20397-9_15
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