Thermodynamic Chapter 6 Thermal Power Plant

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Thermodynamic Chapter 6 Thermal Power Plant

  1. 1. 1 MEC 451 THERMODYNAMICS 1Global Aspiration …… A World Class University CHAPTER 6 THERMAL POWER PLANT
  2. 2. 2 PART 1 2Global Aspiration …… A World Class University GAS TURBINE POWER PLANT
  3. 3. 3 3Global Aspiration …… A World Class University Brayton Cycle The Brayton cycle (a.k.a. Joule cycle) is the air-standard ideal cycle approximation for the gas turbine engine.
  4. 4. 4 Process Description Related formula 1-2 Isentropic compression 2-3 Constant pressure heat addition 3-4 Isentropic expansion 4-1 Constant pressure heat rejection 1 2 1 1 2 2 1 −       =      = k k k T T V V P P 1 2 1 1 2 2 1 −       =      = k k k T T V V P P Brayton Cycle Process Description Global Aspiration …… A World Class University
  5. 5. 5 5Global Aspiration …… A World Class University The T-s and P-v diagrams are
  6. 6. 6 6Global Aspiration …… A World Class University The T-s for actual cycle (including pressure drop and isentropic efficiency)
  7. 7. 7 ∑∑         ++++=        ++++ out out out outoutoutout in in in inininin gz V hmWQgz V hmWQ 22 2...2... ( ) ( )outoutininin hmhmW ... =+ ( )12 . 12 . hhmW −= Global Aspiration …… A World Class University Energy balance: for compressor
  8. 8. 8 8Global Aspiration …… A World Class University Isentropic efficiency for compressor:
  9. 9. 9 ∑∑         ++++=        ++++ out out out outoutoutout in in in inininin gz V hmWQgz V hmWQ 22 2...2... ( ) ( )outoutininin hmhmQ ... =+ ( )23 . 23 . hhmQ −= Global Aspiration …… A World Class University Energy balance: for boiler 2 3
  10. 10. 10 ∑∑         ++++=        ++++ out out out outoutoutout in in in inininin gz V hmWQgz V hmWQ 22 2...2... ( ) ( )outoutoutinin hmWhm ... += ( )43 . 34 . hhmW −= Global Aspiration …… A World Class University 3 4 Energy balance: for turbine
  11. 11. 11 11Global Aspiration …… A World Class University Isentropic efficiency for turbine:
  12. 12. 12 ∑∑         ++++=        ++++ out out out outoutoutout in in in inininin gz V hmWQgz V hmWQ 22 2...2... ( ) ( ) outoutoutinin Qhmhm ... += ( )14 . 41 . hhmQ −= Global Aspiration …… A World Class University 4 1 Energy balance: for condenser
  13. 13. 13 13Global Aspiration …… A World Class University ηth Brayton net in out in W Q Q Q , = = −1 where the pressure ratio is rp = P2/P1 ηth Brayton p k k r , ( )/ = − − 1 1 1 Upon derivation Thermal efficiency of the Brayton cycle is defined as
  14. 14. 14 14Global Aspiration …… A World Class University
  15. 15. 15 15Global Aspiration …… A World Class University For fixed values of Tmin and Tmax, the net work of the Brayton cycle first increases with the pressure ratio, then reaches a maximum at rp = (Tmax/Tmin)k/[2(k - 1)] , and finally decreases.
  16. 16. 16 16Global Aspiration …… A World Class University ( ) ( )43 12 TTc TTc W W r p p t c bw − − ==   Back Work Ratio Part of the work output from turbine is used to drive the compressor, which in turn requires a work input. Therefore the back work ratio can be written as
  17. 17. 17 17Global Aspiration …… A World Class University Example GT-1 The ideal air-standard Brayton cycle operates with air entering the compressor at 95 kPa, 22°C. The pressure ratio rp is 6:1 and the air leaves the heat addition process at 1100 K. Determine the compressor work and the turbine work per unit mass flow, the cycle efficiency and the back work ratio. Assume constant properties.
  18. 18. 18 18Global Aspiration …… A World Class University Cycle Improvement - Regenerative Therefore, a heat exchanger can be placed between the hot gases leaving the turbine and the cooler gases leaving the compressor. This heat exchanger is called a regenerator or recuperator. For the Brayton cycle, the turbine exhaust temperature is greater than the compressor exit temperature.
  19. 19. 19 19Global Aspiration …… A World Class University
  20. 20. 20 20Global Aspiration …… A World Class University The regenerator effectiveness εregen is defined as the ratio of the heat transferred to the compressor gases in the regenerator to the maximum possible heat transfer to the compressor gases. q h h q h h h h q q h h h h regen act regen regen regen act regen , , max ' , , max = − = − = − = = − − 5 2 5 2 4 2 5 2 4 2 ε
  21. 21. 21 21Global Aspiration …… A World Class University For ideal gases using the cold-air-standard assumption with constant specific heats, the regenerator effectiveness becomes 5 2 4 2 regen T T T T ε − ≅ − Upon derivation the thermal efficiency becomes
  22. 22. 22 22Global Aspiration …… A World Class University
  23. 23. 23 23Global Aspiration …… A World Class University Example GT-2 Air enters the compressor of a regenerative gas turbine engine at 100 kPa and 300 K and is compressed to 800 kPa. The regenerator has an effectiveness of 65 percent, and the air enters the turbine at 1200 K. For a compressor efficiency of 75 percent and a turbine efficiency of 86 percent, determine (a) The heat transfer in the regenerator. (b) The back work ratio. (c) The cycle thermal efficiency. Assume air is an ideal gas with constant specific heats.
  24. 24. 24 24Global Aspiration …… A World Class University Cycle Improvement – Intercooling and Reheating
  25. 25. 25 25Global Aspiration …… A World Class University The T-s diagram for this cycle is shown below.
  26. 26. 26 26Global Aspiration …… A World Class University Example GT-3 An ideal gas turbine with two-stage compression and two- stage expansion has an overall pressure ratio of 8. Air enters each stage of the compressor at 300 K and each stage of turbine at 1300 K. Determine the back work ratio and the thermal efficiency of the cycle assuming (a) no regenerators and (b) an ideal regenerator with 100% effectiveness and (c) a regenerator with 60% effectiveness. Assume constant specific heats.
  27. 27. 27 27Global Aspiration …… A World Class University Aircraft Engine
  28. 28. 28 28Global Aspiration …… A World Class University Alstom GT26 Gas Turbine
  29. 29. 29 29Global Aspiration …… A World Class University PW 4000 112-INCH FAN ENGINE
  30. 30. 30 30Global Aspiration …… A World Class University Rolls – Royce Trent
  31. 31. 31 31Global Aspiration …… A World Class University General Electric (GE) Gas Turbine
  32. 32. 32 PART 2 32Global Aspiration …… A World Class University STEAM POWER PLANT
  33. 33. 33 KJM 281 33Global Aspiration …… A World Class University Based on the Carnot cycle the heat engine may be composed of the following components. Carnot Cycle
  34. 34. 34 KJM 281 34Global Aspiration …… A World Class University 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 0 100 200 300 400 500 600 700700 s [kJ/kg-K] T[C] 6000 kPa 100 kPa Carnot Vapor Cycle Using Steam 1 2 3 4 ηth Carnot net in out in L H W Q Q Q T T , = = − = − 1 1 The thermal efficiency of this cycle is given as
  35. 35. 35 KJM 281 35Global Aspiration …… A World Class University Reasons why the Carnot cycle is not used: Pumping process 1-2 requires the pumping of a mixture of saturated liquid and vapor. Low quality steam at the turbine exit. The impracticalities of the Carnot cycle can be eliminated by:  Condensing the steam completely in the condenser.  Superheating the steam to take advantage of a higher temperature.
  36. 36. 36 KJM 281 36Global Aspiration …… A World Class University Process Description 1-2 Isentropic compression in pump 2-3 Constant pressure heat addition in boiler 3-4 Isentropic expansion in turbine 4-1 Constant pressure heat rejection in condenser Rankine Cycle The simple Rankine cycle has the same component layout as the Carnot cycle. The processes in a simple Rankine cycle are:
  37. 37. 37 KJM 281 37Global Aspiration …… A World Class University
  38. 38. 38 KJM 281 38Global Aspiration …… A World Class University The pump work can be determined by: Cycle Analysis ( ) ( )121 12 2211 PPm hhmW hmWhm pump pump −= −= =+ • •• ••• υ The energy balance for boiler: ( )23 3322 hhmQ hmQhm in in −= =+ •• •••
  39. 39. 39 KJM 281 39Global Aspiration …… A World Class University The energy balance for turbine: ( )43 4433 hhmW hmWhm out out −= += •• ••• The energy balance for condenser: ( )14 1144 hhmQ hmQhm out out −= += •• ••• Based on the Second Law the thermal efficiency becomes: ( ) ( ) ( )23 1243 hh hhhh q w in net th − −−− ==η
  40. 40. 40 KJM 281 40Global Aspiration …… A World Class University Cycle Improvement
  41. 41. 41 KJM 281 41Global Aspiration …… A World Class University
  42. 42. 42 KJM 281 42Global Aspiration …… A World Class University Actual Cycle
  43. 43. 43 KJM 281 43Global Aspiration …… A World Class University Example SPP-1 A power plant operates on a simple Rankine cycle. Steam enters the turbine at 3 MPa and 350°C and is condensed in the condenser at a pressure of 75 kPa. Determine (a) the work net, (b) the heat input in the boiler, and (c) the thermal efficiency of the cycle.
  44. 44. 44 KJM 281 44Global Aspiration …… A World Class University Reheat Rankine Cycle
  45. 45. 45 KJM 281 45Global Aspiration …… A World Class University
  46. 46. 46 KJM 281 46Global Aspiration …… A World Class University Component Process First Law Analysis Boiler Constant Pressure qin = (h3 - h2 ) + (h5 - h4 ) Turbine Isentropic wout = (h3 - h4 ) + (h5 - h6 ) Condenser Constant Pressure qout = (h6 - h1 ) Pump Isentropic win = (h2 - h1 ) = v1 (P2 - P1 ) ( ) ( ) ( ) ( ) ( )4523 126543 hhhh hhhhhh q w in net th −+− −−−+− ==η
  47. 47. 47 KJM 281 47Global Aspiration …… A World Class University Example SPP-2 Consider a steam power plant operating on the ideal reheat Rankine cycle. Steam enters the high-pressure turbine at 15 MPa and 600°C and is condensed in the condenser at a pressure of 10 kPa. If the moisture content of the steam at the exit of the low-pressure turbine is not to exceed 10.4 percent, determine (a) the pressure at which the steam should be reheated, and (b) the thermal efficiency of the cycle. Assume the steam is reheated to the inlet temperature of the high-pressure turbine.
  48. 48. 48 KJM 281 48Global Aspiration …… A World Class University Regenerative Cycle
  49. 49. 49 KJM 281 49Global Aspiration …… A World Class University Regenerative Cycle with Open FWH
  50. 50. 50 KJM 281 50Global Aspiration …… A World Class University Regenerative Cycle with Closed FWH
  51. 51. 51 KJM 281 51Global Aspiration …… A World Class University Example SPP-3 Consider a steam power plant operating on the ideal regenerative Rankine with one open feedwater heater. Steam enters the turbine at 150 bar and 600°C and is condensed in the condenser at a pressure of 0.1 bar. Some steam leaves the turbine at a pressure of 12 bar and enters the open feedwater heater. Determine the fraction of steam extracted from the turbine and the thermal efficiency of the cycle.
  52. 52. 52 KJM 281 52Global Aspiration …… A World Class University Plant Layout
  53. 53. 53 KJM 281 53Global Aspiration …… A World Class University Plant Monitoring System
  54. 54. 54 PART 3 54Global Aspiration …… A World Class University SPECIAL APPLICATION
  55. 55. 55 KJM 281 55Global Aspiration …… A World Class University Cogeneration
  56. 56. 56 KJM 281 56Global Aspiration …… A World Class University Cogeneration Stand-Alone System
  57. 57. 57 KJM 281 57Global Aspiration …… A World Class University Trigeneration Plant
  58. 58. 58 KJM 281 58Global Aspiration …… A World Class University Combined Cycle
  59. 59. 59 KJM 281 59Global Aspiration …… A World Class University Karlsruhe Power Station (Germany) Topping cycle = 2 x Bottoming cycle
  60. 60. 60 KJM 281 60Global Aspiration …… A World Class University Sultan Ismail Power Station (Paka) Combined Cycle (808 MW) Gas Turbine – 137 MW x 4 Units Steam Turbine – 130 MW x 2 Unit Topping cycle = 2 x Bottoming cycle
  61. 61. 61 KJM 281 61Global Aspiration …… A World Class University Pasir Gudang Power Station (Johor) Combined Cycle (404 MW) Gas Turbine – 137 MW x 2 Units Steam Turbine – 130 MW x 1 Unit Topping cycle = 2 x Bottoming cycle
  62. 62. 62 KJM 281 62Global Aspiration …… A World Class University Connaught Bridge Power Station (Klang)
  63. 63. 63 KJM 281 63Global Aspiration …… A World Class University Binary Vapor Cycle
  64. 64. 64 KJM 281 64Global Aspiration …… A World Class University

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