The process of extracting steam from the turbine at certain points during its expansion and using
this steam for heating for feed water is known as Regeneration or Bleeding of steam. The arrangement
of bleeding the steam at two stages is shown in Figure below
Let,
m2 = Weight of bled steam at a per kg of feed water heated
m2 = Weight of bled steam at a per kg of feed water heated
H1 = Enthalpies of steam and water in boiler
Hw1 = Enthalpies of steam and water in boiler
H2, H3 = Enthalpies of steam at points a and b
t2, t3 = Temperatures of steam at points a and b
H4, Hw4 = Enthalpy of steam and water exhausted to hot well.
Work done in turbine per kg of feed water between entrance and a
= H1 – H2
Work done between a and b = (1 – m2)(H2 – H3)
Work done between b and exhaust = (1 – m2 – m3)(H3 – H4)
Total heat supplied per kg of feed water = H1 – Hw2
Efficiency (η) = Total work done/Total heat supplied
= {(H1 – H2) + (1 – m2)(H2 – H3) + (1 – m2 – m3)(H3 – H4)}/(H1 – Hw2)
