Rankine cycle with respect to P-V, T diagrams:
The steam having high pressure is expanded to a low pressure within a reciprocating engine or a turbine.
If expansion is ideal (that is one of constant entropy), the cycle is called as Rankine cycle.
However, in actual plant friction takes place in the flow of steam through engine or turbine which results in expansion with increasing entropy. By applying 1st law to this method: (c) 3 - 4:The low-pressure wet steam is condensed completely at constant condenser pressure back into saturated water. The latent heat of condensation is rejected to the condenser cooling water which, in turn, rejects this heat to atmosphere. By applying 1st law of the thermodynamics, (d) 4 - 1:The low pressure saturated water is pumped back up to boiler pressure and it becomes sub saturated. The water then enters again in the boiler and begins a new cycle. By applying the first law:
However, Win can be neglected with the accuracy and we can assume h1 = h4.
The thermal efficiency of cycle can be given by: Specific steam consumption can be given by: