It is more convenient to analyze the performance of steam power plants by means of idealized cycles which are theoretical approximations of the real cycles. The Carnot cycle is an ideal, but non-practising cycle giving the maximum possible thermal efficiency for a cycle operating on selected maximum and minimum temperature ranges.It is made up of four ideal processes:
1 - 2 : Evaporation of water into saturated steam within the boiler at the constant maximum cycle temperature T1 (= T2)
2 - 3 : Ideal (i.e., constant-entropy) expansion within the steam engine or turbine i.e., S2 = S3.
3 - 4 : Partial condensation within the condenser at the constant minimum cycle temperature T3 (= T4).
4 - 1 : Ideal (i.e., constant-entropy) compression of very wet steam within the compressor to complete the cycle, i.e., S4 = S1.
