1. Carnotization of Rankine Cycle thru Regeneration
P M V Subbarao
Professor
Mechanical Engineering Department
Use of Entropy Carrying Vehicles …..

2. Reassessment Thru Carnot Model

3. Zone Heat Addition Leading High Entropy Generation

4. Irreversible Heat transfer process : Rankine Cycle
External Irreversibilities in A Rankine cycle
Flue gases
Rate of Entropy generation in universe due to Heat addition: 3 1
External Irreversibility-1 8
1kg
2sv
2sl 7 T 6
Rate of Entropy generation in universe due to Heat rejection: 2 5 4 1
Cooling water e f
External Irreversibility-2 S s

5. Look for More Opportunities to Reduce Wastage

6. Follow the Steam Path

7. Follow the Steam Path

8. Follow the Steam Path

9. Follow the Steam Path

10. Regeneration Using Partially Expanded Steam

11. Regeneration Cycle with Mixer (Open Feed Water Heater)

12. Synthesis of Rankine Cycle with OFWH5 6 T 6’ 4
p2=p6 3 2 1 7

13. Analysis of mixing in OFWH
Constant pressure mixing process h6 y
Consider unit mass flow rate of steam thru the turbine h2
1-y h3
Conservation of energy:

14. Analysis of Regeneration through OFWH

15. Optimal Location of FWH

16. Comparison of Performance of Bleed & Condensing Steams
hcond
hbleed
Pregen, MPa

17. Performance of FWH Cycle
~ 12MPa
htotal
pbleed, MPa

18. Performance of bleed Steam
~ 2 Mpa
hbleed
pbleed, MPa

19. Gross Workoutput of bleed Steam
~ 12MPa
wbleed
pregen, MPa

20. Workoutput of bleed Steam
wbleed
y pregen, MPa

21. More Work output with more bleed Steams
wbleed
y pregen, MPa

22. Progress in Rankine Cycle
Year
1907
1919
1938
1950
1958
1959
1966
1973
1975 MW 5 20 30 60
120
200
500
660
1300
p,MPa
1.3
1.4
4.1
6.2
10.3
16.2
15.9
24.1
Th oC
260
316
454
482
538
566
565
Tr oC --
FHW 2 3 4 6 7 8
Pc,kPa
13.5
5.1
4.5
3.4
3.7
4.4
5.4
h,%
~17
27.6
30.5
35.6
37.5
39.8
39.5 40

23. Open (Direct Contact) Feed Water Heater

24. An Impractical Efficient Model for Power Plant
Turbine B SG
Yj-11,hbj-1
yj, hbj
Yj-2,hbj-2 C
OFWH
OFWH
OFWH C
1 ,hf (j)
1- yj
hf (j-1)
1- yj – yj-1
hf (j-2)
1- yj – yj-1- yj-2
hf (j-3)
n number of OFWHs require n+1 no of Pumps…..
The presence of more pumps makes the plant subtle…

25. Closed Feed Water Heater (Throttled Condensate)

26. Reversible Installation for Closed Feed Water Heater

27. Thermal Efficiency Specific Work Output
Effect of no of feed water heaters on thermal efficiency and work output of a regeneration cycle
Thermal Efficiency
Specific Work Output

28. Thermodynamic Analysis of A Modern Power Plant

29. Efficiency of Danish Coal-Fired Power Plants
Continuous development resulted around the mid 80's in an average efficiency of 38% for all power stations, and best values of 43%.
In the second half of the 1990’s, a Danish power plant set a world record at 47%.

30. Average efficiency, specific coal usage, CO2 emissionsh
Indian Coal Plants:
Efficiency of modern coal power plant = 34-36%
Efficiency of old power plant = 20-30%

31. Major Equipment in A Power Plant
Steam generator
Turbine
Condenser
Pump
Feed Water Heaters