Effect of Reheating and Feed Water Heating on Steam Generation

P M V SubbaraoProfessor

Mechanical Engineering Department

Good to Turbine and Cycle…..What about Steam Generator ???

Effect of Reheat Pressure

prh/pmax

0.2 0.4 0.6 0.8 1.0

~0.3

Selection of Optimal Reheat Point

Reheat Supercritical Rankine Cycle

1

2

2s

3

4

5

6

Reheating : A Means to implement High Live Steam Pressure

Impr

ovem

ent i

n E

ffic

ienc

y, % 593/6210C

593/5930C565/5930C

565/5650C

538/5650C

538/5380C

Supercritical

Single-Reheat Ultrasupercritical Product LineGE Power

Super Critical Cycle ~ 1990

Double Reheat Ultra Super Critical Cycle

8

Reheater Pressure Optimization forDouble Reheat Units

Impr

ovem

ent i

n E

ffic

ienc

y, %

Scope for Double Reheat in Ultra CriticalCycles

5380C

6100C

6100C

5380C

P,bar 350150

Super Critical Cycle of Year 2005

Double Reheat Super Critical Plants

Net efficiency on natural gas is expected to reach 49%. Net efficiency on coal is expected to reach 47%.

Super Critical Cycle of year 2010

> 50 %

Double-Reheat Ultrasupercritical Product LineGE Power

Ultra Supercritical Installations of The World

C

C

CC

Reassessment Thru Carnot Model

s

Non-Isentropic Expansion !!!

A Macro Carnot Cycle !!!!

Ideal Regenerative Cycle

Regenerative Turbine

Regenerative heat transfer. Change in kinetic and potential energies are negligible

3

4

T

inin mmCMSSSF ::

CVout

outin

inCV WgzVhmgzVhmQ

22

CVoutoutininREGEN WhmhmQ

ssuming a single fluid entering and leaving…

2374 hhmhhmhhmQW outinREGENCV

REGENQ

Analysis of Regeneration Cycle

s

12

2374

17

34

hhmW

hhhhmW

hhmQ

hhmQ

pump

turbine

out

in

additionHeat of Rate

outputPower Net cycle theof Efficiency

34

17

34

1734 1hh

hh

hhm

hhhhm

in

net

Q

W

smS