Carnot Cycle

Carnot Cycle::

  • This cycle was proposed in 1824 by a German engineer  “SADI CARNOT”.
  • It is a hypothetical cycle which is used to compare other cycle.
  • It consists of four reversible process.

Assumptions of Carnot Cycle::

  • Working substances is a perfect gas.
  • There is no friction between the cylinder and piston.
  • Walls of cylinder and piston are considered as perfect heat insulator.
  • Transfer of heat does not affect the temperature of source or sink.

Processes of Carnot Cycle::

Process 1-2 (Isothermal Heat Addition):

  • Reversible isothermal heat addition at high temperature. 
  • The gas is allowed to expand isothermally by receiving heat (QH) from a hot reservoir.
Isothermal Heat Addition
Process 1-2: Isothermal Heat Addition

Process 2-3 (Adiabatic Expansion):

  • Reversible adiabatic expansion from high temperature to low temperature. 
  • The cylinder now is insulated and the gas is allowed to expand adiabatically and thus doing work on the surrounding.  
  • The gas temperature decreases from TH to TL.  
Adiabatic Expansion
Process 2-3: Adiabatic Expansion

Process 3-4 (Isothermal Heat Rejection):

  • Reversible isothermal heat rejection at low temperature.  
  • The insulation is removed and the gas is compressed isothermally by rejecting heat (QL) to a cold reservoir. 
Isothermal Heat Rejection
Process 3-4: Isothermal Heat Rejection

Process 4-1 (Adiabatic Compression):

  • Reversible adiabatic compression from low temperature to high temperature. 
  • The cylinder is insulated again and the gas is compressed adiabatically to state 1, raising its temperature from TL to TH.
Adiabatic Compression
Process 4-1: Adiabatic Compression

P-V & T-S diagram of Carnot Cycle:

P-V & T-S Diagram of Carnot Cycle
T-S & P-V diagram of Carnot cycle

Efficiency of a Carnot Cycle:

Efficiency of Carnot cycle
Efficiency of Carnot cycle

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