CARNOT CYCLE

The Most Efficient Ever But Ideal

GROUP MEMBERS:

MUHAMMAD OMER (2015-EE-468) WALEED TARIQ (2015-EE-406)

ZAIN-UL-ABIDIN (2015-EE-456) RIDA FATIMA (2015-EE-462) USAMA BUTT (2015-EE-492)

CONTENTS INTRODUCTION HISTORY ASSUMPTIONS P-V DIAGRAM EFFICIENCY LIMITATIONS CONCLUSIONS

INTRODUCTION The most powerful and efficient heat cycle consisting of two isothermal and two adiabatic processes.

This actually is the idealization because in order to approach it’s efficiency the processes involved must be reversible and involves no change in entropy.

A system undergoing carnot cycle is called “Carnot Engine”.

HISTORY Proposed by Nicolas Léonard Sadi

Carnot in 1824. He was a French Engineer. Founder of the science of

thermodynamics. First one to recognize the relationship

between work and heat.

1796-1832

COMMON ASSUMPTIONS OF CARNOT CYCLE

Isothermal expansions and compressions are considered quasi-equilibrium.

No heat losses in pipes and other components.

The cycles do not have any friction. Thus, no pressure drops in the working fluid.

Changes in kinetic and potential energies are negligible.

P-V DIAGRAMProcesses:- Isothermal

Expansion (1-2)

Adiabatic Expansion

(2-3) Isothermal

Compression (3-4) Adiabatic

Compression (4-1)

4 STEPS

OF CARNO

T CYCLE

ELABORATION The fig. shows the schematic and

accompanying P-V diagram of a carnot cycle executed by water steadily circulating through a simple vapor power plant.

The steam exiting the boiler expands adiabatically through the turbine and the work is developed . The steam temperature decreases from TH To TL.

Two phases mixture flows through condenser where heat rejection occurs at constant temperature TL.

ELABORATION The mixture (liquid-vapour) enters the

pump (or compressor) and its pressure increases.This is an adiabatic process and requires input work.

The saturated liquid at high temperature enters the boiler,where change of phase occurs at constant temperature TH.

CARNOT THEOREM• No real engine can be more efficient

than a Carnot Engine operating between same two reservoirs.

• All Carnot Engines operating between reservoirs at the same temperature have the same efficiency.

PROOF OF CARNOT THEOREM

An impossible situation.A heat engine cannot drive a less

efficient heat engine. Voilation of 2nd Law of Thermodynamics. If ŋM > ŋL, then the net heat flow would

be backwards, i.e., into the hot reservoir.

PROOF OF CARNOT THEOREM FOR: Reversible Engines :

“ All reversible engines that operate between the same two heat reservoirs have the same efficiency.”

Irreversible Engines: “ No irreversible engine is more efficient than the Carnot engine operating between the same two reservoirs.”

EFFICIENCY OF CARNOT CYCLE Thermal efficiency of the Carnot cycle

can be calculated from: th=1-(QL/QH)=1-(TL/TH). So called the Carnot efficiency. The higher the temperature of the low-

temperature sink, the more difficult for a heat engine to transfer heat into it.Thus, lower thermal efficiency also.

LIMITATIONS OF CARNOT CYCLE The isentropic process 1-2 is practically

not achievable,as it is difficult to handle two phase system.

If the steam quality is poor then process 3-4 is difficult to carry out.

CONCLUSIONS We can say that Carnot Engine is one

of the most efficient one but it’s ideal one.

Let assume for a moment that it’s not an ideal cycle then what would happen??

I think there will be no other engines Because after this gorgeous thing there is no need