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Main Steam Cycle

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Main Steam Cycle. Let the fun begin…. Introduction. Parts of the Main Steam Cycle Four Phases of the cycle Definitions of each phase Components involved with phases Press-temp relationships. Parts of Main Steam Cycle. Steam Generator (nuclear) or Boiler (conventional) Turbines Condenser

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Main Steam Cycle

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  1. Main Steam Cycle Let the fun begin…

  2. Introduction • Parts of the Main Steam Cycle • Four Phases of the cycle • Definitions of each phase • Components involved with phases • Press-temp relationships

  3. Parts of Main Steam Cycle • Steam Generator (nuclear) or Boiler (conventional) • Turbines • Condenser • Main Condensate Pumps • Deaerating Feed Tank / Reserve Feed Tanks • Main Feed Pumps

  4. Main Steam Cycle

  5. Background • Cycle used is a Rankine cycle • P-v and T-s Diagrams • Trace the points of cycle • Provide graphical understanding of cycle • Four phases of cycle • Conventional vs. Nuclear

  6. Rankine Cycle T-s Diagram P-v Diagram 1-2: Feed Phase (DQ=0, DS=0), Win 2-3: Generation Phase (DP=0), Qin 3-4: Expansion Phase (DQ=0, DS=0), Wout 4-1: Condensation Phase (DP=0), Qout

  7. Generation Phase - Conventional • Boiler (1200 # steam) • Fuel burned to produce heat -> transferred to water which boils to steam • Steam collects in steam drum (saturated) • Superheater • Increase temp of steam and dries steam • Three reasons for superheating? • Minimize erosion (dry steam better for blading) • Minimize corrosion (less chemicals entrained) • Maximize DT (Carnot efficiency)

  8. Boiler and Superheater

  9. Generation Phase - Nuclear • Reactor (Rx) Plant • Fission in Rx core transforms nuclear energy to thermal energy • Steam Generator • Water Space • U-tubes • Steam Space • Moisture Separators

  10. Reactor Plant

  11. Expansion Phase • Steam travels down main steam piping • Turbines convert thermal energy -> mechanical energy (nozzles) and then work (blading) -> turn rotor/shaft • Pressure drops as steam goes through • Work performed on turbine blading • Main Engines (ME) -> propulsion • Ship’s Service Turbine Generators (SSTG) -> electricity

  12. Condensation • Vacuum 26-29” Hg • Air Ejectors - use 150# steam to establish initial vacuum and remove air • Maintained by condensation • volume of water << volume of steam -> contraction • Why vacuum? • Ease of steam recovery (“pulls” steam into MC) • More work out of turbines (larger DP and DT) • Ease of conversion to water

  13. Condensation • Main Condenser • Large, indirect, cross-flow, shell-and-tube HX • Seawater used to condense steam • Hotwell - holding area for condensate water at 80-100 F (lowest temp in cycle) • Main Condensate Pumps - send condensate to the DFT at 20-30 psi (suction side is lowest pressure in cycle)

  14. Main Condenser

  15. Feed Phase • Deaerating Feed Tank (DFT) • Direct-type HX (Aux Steam used) • Purposes • preheats feed • storage/surge volume • removes dissolved oxygen to minimize corrosion • FYI: RFT’s often used instead • Main Feed Pump • Supplies feed water to Steam Generator (must be high pressure to overcome pressure)

  16. Deaerating Feed Tank

  17. Putting It All Together

  18. Your Drawing • Boiler/Steam Generator • Superheater • Turbine • Condenser • Main Condensate Pumps • Main Feed Pumps • DFT/RFT • Economizer

  19. Questions?

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