Sunday, January 24, 2010
Carnot cycle
Carnot engine
Carnot is an ideal engine it is consist of a cylinder with frictionless piston which is filled with ideal gas. The wall of cylinder and piston should be insulator and bottom should be good conductor. An infinite heat capacity of hot body and cold is used as source of heat and heat sink.
Carnot cycle
In which thermodynamic process Carnot engine works is called Carnot cycle. It is consist in the following four process.
1. Isothermal process
2. Adiabatic process
3. Isothermal compression
4. Adiabatic compression
Isothermal process
Carnot is an ideal engine it is consist of a cylinder with frictionless piston which is filled with ideal gas. The wall of cylinder and piston should be insulator and bottom should be good conductor. An infinite heat capacity of hot body and cold is used as source of heat and heat sink.
Carnot cycle
In which thermodynamic process Carnot engine works is called Carnot cycle. It is consist in the following four process.
1. Isothermal process
2. Adiabatic process
3. Isothermal compression
4. Adiabatic compression
Isothermal process
In this process an ideal gas filled cylinder is placed on the source of heat. The temperature of the system is kept constant during process when the piston is slightly moved upward the internal energy of the system becomes low because of doing work. To keep the temperature constant the heat Q1 is supplied from the source of heat.
Consider the initial pressure of the gas = P1
The initial volume of the gas = V1
The initial temperature of the gas=T1
At the final stage the pressure become =P2
The final volume = V2
But the temperature remain constant = T1
Adiabatic expansion
to stop the heat absorbing and discharging to make the system isolated. Now the external pressure is reduced immediately the gas expands because of internal pressure this internal energy is used to work. In this process no external energy is provided to the system its temperature fall from T1 to T2 at the end of this process the pressure of gas is P3 and its volume is V3
Isothermal compression
At the 3rd step cylinder is kept on a heat sink the temperature of the heat sink must be equal to the temperature of the gas now the external pressure applied on the cylinder is increased slowly. In this way by doing work on gas the internal energy of the system increased and as a result it temperature increased. To keep the gas temperature at constant some heat Q2 insert in sink from the bottom of the cylinder. At the end of this process the pressure of the gas becomes P4
The volume of the gas V4
The temperature of the gas T2
Adiabatic compression
In the final step of Carnot cycle the cylinder is kept on an insulator and its external pressure is sharply increased in this way work is done on the system and the temperature of the system will be increased. The gas is compressed in adiabatic compression until it reaches in its initial stage so that it temperature become T1volume V1 and pressure P1
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