ABSTRACT
In this chapter we extend the idea of reversible processes to reversible and irreversible cycles, by first introducing the rather obtuse concepts associated with entropy and entropy change that takes place with irreversible processes. We take another look at the heat engine and thermal efficiency for ideal cycles that we touched upon towards the end of Chapter 13 when we introduced the second law of thermodynamics in section 13.5. The important cycles covered are the thermodynamically reversible Carnot cycle, the constant volume or Otto cycle, the diesel cycle and the closed constant pressure cycle. In Chapter 16 we will extend our knowledge of the Otto and constant pressure cycles to the practical cycles of the four-stroke spark ignition piston engine and to the closed and open system gas turbine engine. We start with the concept of entropy and its use (among other things) in being able to find the end-state of an irreversible process.
