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Sunday, 30 March 2014

Advantages and Disadvantages of Closed Cycle Gas Turbine

Advantages and Disadvantages of Closed Cycle Gas Turbine Points : Advantages and Disadvantages of Closed Cycle Gas Turbine Advantage
  1. As the working fluid does not mixed with the products of combustion therefore it is possible to use a gas of higher density and higher specific heat then air such as krypton, argon" xenon etc. This will reduce the size of the various components. Helium has been successfully used as working medium in closed cycle gas turbines. The specific heat of helium at constant pressure at being nearly five times that of the air so heat drops and hence energy delta per kg of mass flow in about five times in turbines using air heat exchanger sued in glass turbines using helium as working medium less surface area of about 1/3 that of heat exchanger used in gas turbines using air as working medium. Therefore the size of helium unit is comparatively smaller.
  2. As the working medium does not mix with the product of combustion so there is no accumulation of carbon deposits on blade and nozzles of the turbine. The compressor remain free of dust as the working medium may be cleaned. Therefore, the periodic cleaning of component is not needed.
  3. The system has improved part load efficiency as the output can be varied by withdrawing or admitting more working medium.
  4. External heating can be done by inexpensive solid fuels such as coal.
Disadvantages
  1. As the system is under an initial high pressure with a working medium other than air, therefore the system should be gastight. This increase the cost of the system.
  2. A large air heater is needed and this air heater is not as sufficient as the combustion chamber used in open cycle.
  3. As the system needs cooling water so the system cannot be used in aeronautical engines.

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