Performance Analysis of Power Plant Condensers

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Performance Analysis of Power Plant Condensers

• P M V Subbarao
• Professor
• Mechanical Engineering Department
• I I T Delhi

A Device Which makes Power Plant A True Cycle.. A
Device Which set the limit on minimum cycle
pressure..
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T-S Diagram Rankine Cycle with FWHs.
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Two-Pass Surface Condenser
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T-S Diagram Rankine Cycle with FWHs.
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Thermal Processes Occurring in Condensers

• The condenser never receives pure seam from the
  turbine.
• A mixture of steam and non-condensable gases
  (Air-steam mixture) enters the condenser.
• The ratio of the quantity of gas that enters the
  condenser to the quantity of steam is called the
  relative air content.

• The value of e, depends on type, capacity, load
  and design dimensions of the condenser plant.

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Variation of Steam-air Mixture Parameters
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• Using Dalons Law

Gas laws
Volumes and temperatures are same.
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• At the entry to condenser the relative content of
  air is very low and partial pressure of steam is
  almost equal to condenser pressure.
• As air-steam mixture moves in the condenser,
  steam is condensed and the relative content of
  air increases.
• Accordingly, the partial pressure of steam drops
  down.
• The total pressure in the bottom portion of
  condenser is lower than that of the top portion.
• The pressure drop from inlet to exit of condenser
  is called steam exhaust resistance of a
  condenser.
• The partial pressure of air at the bottom of the
  condenser cannot be neglected.

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• The temperature of steam is a function of
  condenser pressure.
• As the air-steam mixture moves through the
  condenser and the steam is condensed, its
  temperature decreases owing to decreasing partial
  pressure of saturated steam.
• This is due to increase in relative content of
  air in the mixture.
• The pressure also decreases due to resistance to
  flow of steam.
• The zone of intensive condensation.
• The zone of cooling of air-steam mixture.

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Variation of Steam Partial Pressure Saturation
Temperature
Saturation Temperature, 0C
Steam Partial Pressure, kPa
exit
Inlet
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Condenser with Air Removal Pump A practicable
Concept
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Combined Condensation Air Pumping Action
Air Pumping Action Vs Condensing Action !!!
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Effect of Air Leakage on Condenser Pressure
Inlet Condenser Pressure, mm of Hg
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30
40
50
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Cooling water Inlet Temperature
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Power Loss Due to Excess Back Pressure
What is Techno-economically Viable value of TTD ?
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Condensate Depression

• The temperature of condensate is always a few
  degrees lower than the coincident condensing
  steam temperature.
• Subcooling of condensate is undesirable on two
  accouts
• It lowers the thermodynamic efficiency of the
  power cycle.
• It enhances the propensity of the condensate to
  reabsorb non-condensibles.