Carnot Engine

In the year 1824, Nicolas Carnot proposed a thermodynamic cycle called the Carnot cycle. This cycle has theoretical properties. Carnot suggested from his discovery that hot bodies are necessary in order to produce heat while cold bodies are required to convey the caloric value generated by the hot body. A cold body can help produce the mechanical work during this process. It also proves that the work involved is independent of materials that are used to generate heat where design and construction of the machine using these materials.

Modern representation

The following is a block diagram of a classic heat engine like Carnot -

From the figure, a working body means any fluid body or just vapor through which the heat energy (Q) can be transmitted to actual yield work. Nicolas Carnot proposed that this fluid body or working body can be of any type of material which can afford the expansion process. They can be the expansion of vapor of water, the vapor of alcohol, or even the expansion of mercury or permanent gas, etc. During the olden days, engines were manufactured in the form of a number of patterns and generally, boilers delivered QH. Meanwhile, a boiler delivers water whereas QC was basically delivered by cold flowing liquid, mainly water.

This can be in the form of a condenser which is located on a different part of the engine. From the figure, W denotes the yield work which literally means the piston movement as this movement helps rotate a crank arm. This crank arm can be utilized to power a pulley in order to lift water and throw it out of the salt mines which are submerged in it. In very simple terms, Carnot defines work as “weight lifted through a height” which simplifies everything.

Principles of Carnot engine

Initially, Carnot engines were designed for cyclical devices namely heat engines, based on the following statements -

• The efficiency produced by reversible heat engines can always be seen as lesser than that of the effectiveness of a reversible one that functions in between the two similar reservoirs.
• The efficiency of all the provided heat engines that function the two similar reservoirs is always equal.

In order to rapidly enhance the thermal efficiency generated by a gas power turbine, it is essential to improve the combustion room temperature. For instance, the blades of wind turbines cannot possibly hold high-temperature gas which can lead to an early failure.

Carnot’s Theorem

Carnot’s theorem states that the effectiveness of the reversible engine functions between two equal temperatures is always higher than the engine that functions between two known or unknown temperatures. Moreover, all the reversible engines that work on two similar temperatures always have the same efficiency. It does not matter what working material it uses. It always results in similar accuracy. According to Carnot’s theorem, the productivity and effectiveness of the reversible engines will always be much greater than that of the irreversible ones. A reversible heat engine acts as a heat pump as it works on reversed cycles.

Steps involved in a Carnot cycle

1. Isothermal expansion at T_h

The first process is reversible isothermal gas expansion. This is the amount of gas expanded in a reversible isothermal process. This process indicates that the amount of heat that is absorbed by an ideal gas (which can be represented as ) is from an actual heat source. This is situated at a temperature called . Here, the gas is capable of expanding and doing work in the environment.

2. Adiabatic expansion from T_h and:T₁

This process is called reversible adiabatic gas expansion. It is the expansion of gases due to a reversible adiabatic process. In this process, the system can be thermally insulated. Apart from this, gas present in this process helps to expand while doing the work on the surroundings with the help of its continuous action. This lowers the temperature,

3. Isothermal compression at T₁ :

The following process is named as reversible isothermal gas compression process where gas is being compressed with the aid of a reversible isothermal process. In this process, the heat loss is found to occur while the surroundings complete the work at temperature .

4. Adiabatic compression from and T₁ and T_h :

This process is also termed as reversible adiabatic gas compression. It is the compression of gas due to a reversible adiabatic process. This system is insulated thermally. In here, the temperature increases back to since the work on gas is continued in the surroundings.