Thermodynamics

Carnot Engine

By now we all know how an engine works. But do you know what a Carnot engine is? It’s an engine that is found in your refrigerators and air conditioners. It involves two reversible isothermal transitions and two reversible adiabatic transitions. Let us study more about it below.

Suggested Videos

Play
Play
Play
Arrow
Arrow
ArrowArrow
First Law of Thermodynamics
Thermodynamic Processes
Introduction to Thermodynamics
Slider

 

Carnot Engine Principles

Carnot principles are only for the cyclical devices like heat engines, which state that :

  • The efficiency of an irreversible heat engine is always less than the efficiency of a reversible one operating between the same two reservoirs.
  • The efficiencies of all reversible heat engines operating between the same two reservoirs are the same.

Read about Reversible and Irreversible process in more detail here

To increase the thermal efficiency of a gas power turbine, it is necessary to increase the temperature of the combustion chamber. Like, turbines blades cannot withstand the high-temperature gas and lead to early fatigue.

Carnot’s Theorem

                                                                                                                    Source Wikipedia

This theorem states that no engine working between two given temperatures can be more efficient than a reversible engine working between the same two temperatures and that all the reversible engines working between the same two temperatures have the same efficiency, whatever the working substance may be. According to the Carnot theorem, the reversible engine will always have a greater efficiency than the irreversible one. The reversible heat engine operates on a reverse cycle and functions as a heat pump (or refrigerator).

The Carnot cycle is reversible representing the upper limit on the efficiency of an engine cycle. Practical engine cycles are irreversible and thus have inherently lower efficiency than the Carnot efficiency when operating at the same temperatures.One of the factors determining efficiency is the addition of to the working fluid in the cycle and its removal. The Carnot cycle achieves maximum efficiency because all the heat is added to the working fluid at the maximum temperature.

The Efficiency of Carnot’s Cycle

The Carnot cycle is reversible representing the upper limit on the efficiency of an engine cycle. Practical engine cycles are irreversible and thus have inherently lower efficiency than the Carnot efficiency when operating at the same temperatures.One of the factors determining efficiency is the addition of to the working fluid in the cycle and its removal. The Carnot cycle achieves maximum efficiency because all the heat is added to the working fluid at the maximum temperature.

Carnot cycle

The Carnot engine cycle when acting as a heat engine consists of the following steps:
  • Reversible isothermal expansion of the gas at the “hot” temperature.
  • Isentropic (reversible adiabatic) expansion of the gas.
  • Reversible isothermal compression of the gas at the “cold” temperature.
  • Isentropic compression of the gas.

Read about Reversible and Irreversible process in more detail here

Solved Example For You

Q.Which of the following statements is incorrect?

  1. All reversible cycles have the same efficiency.
  2. The reversible cycle has more efficiency than an irreversible one.
  3. Carnot cycle is a reversible one
  4. Carnot cycle has maximum efficiency in all cycles.

Answer: A. We all know that the Carnot cycle is a reversible and reversible cycle has the maximum efficiency of all other cycles.

Share with friends

Customize your course in 30 seconds

Which class are you in?
5th
6th
7th
8th
9th
10th
11th
12th

Leave a Reply

avatar
  Subscribe  
Notify of

Stuck with a

Question Mark?

Have a doubt at 3 am? Our experts are available 24x7. Connect with a tutor instantly and get your concepts cleared in less than 3 steps.

Download the App

Watch lectures, practise questions and take tests on the go.

Do you want

Question Papers

of last 10 years for free?

No thanks.