SECOND LAW OF THERMODYNAMICS
Figure 36 Steam Cycle (Ideal)
Figure 37 is a T-s diagram of a cycle which more closely approximates actual plant processes.
The pumps and turbines in this cycle more closely approximate real pumps and turbines and thus
exhibit an entropy increase across them. Additionally, in this cycle, a small degree of subcooling
is evident in the condenser as shown by the small dip down to point 5. This small amount of
subcooling will decrease cycle efficiency since additional heat has been removed from the cycle
to the cooling water as heat rejected. This additional heat rejected must then be made up for in
the steam generator. Therefore, it can be seen that excessive condenser subcooling will decrease
cycle efficiency. By controlling the temperature or flow rate of the cooling water to the
condenser, the operator can directly effect the overall cycle efficiency.
Figure 37 Steam Cycle (Real)