Regenerative Cycle

In the reheat modification of The Renkine Cycle, the effective temperature at which energy is added is increased by supplying a large portion of energy in the superheat region.

The average temperature at which energy addition takes place can also be increased by preheating the feed water before it enters the boiler.

A Rankine cycle using this type of feed water heating is called a regenerative cycle (see Figures 28.2 (a) and (b)).

Figure 28.2a

Figure 28.2b

Consider the feed water heater

(28.5)

and

(28.6)

or

or

(28.7)

Fraction of steam extracted for preheating

The above equation can be used to determine the fraction of steam to be with drawn from the turbine at an intermediate state so that the resultant stream is a saturated liquid at state 3 after mixing.

Energy added in the boiler,

(28.8)

Energy rejected in the condenser,

(28.9)

(28.10)

The work output of the turbine,

The work spent in the pumps

Another arrangement

Another arrangement of regenerative feed heating is shown in Figure 28.3 (a) and (b).

Figure 28.3(a)

Figure 28.3(b)