Reversed Carnot Cycle

We have already discussed the concept of “Carnot Cycle” & “Its Efficiency” and we have also seen the concept of “Carnot Theorem And Its Explanation” in our previous post.

As we have already discussed that the Carnot Cycle is a reversible cycle and every process in the Carnot cycle is a reversible process. Therefore, every process of the Carnot cycle can be reversed. And the cycle can be operated in the opposite direction as well.

In this article, we're interested in learning more about the reversed Carnot cycle, also known as the reversed Carnot heat engine cycle.

Reversed Carnot Heat Engine

It is important to note that if a reversible process is reversed, all related energy types—such as heat energy or work energy—will have the same magnitude but the direction of their interaction with matter will be changed.

Let us first look at the Reverse Carnot Heat Engine cycle here;

The reversed Carnot heat engine cycle is depicted in the following figure. According to the diagram, the reversed Carnot heat engine cycle consists of four distinct processes. We'll go over each one here;

Step-1

"AB-Adiabatic Compression Process"

Process "AB" will be the adiabatic compression process or isentropic compression process. Working fluid will be compressed here during the adiabatic compression process or isentropic compression process "A to B" by receiving work energy "W" from surrounding.

       

Work energy will be added to the system from surrounding. During this process, pressure and temperature of working fluid will be increased but there will not be any heat interaction between system and surrounding. Volume of working fluid will be reduced during this process.

As shown in figure, temperature of the working fluid is increased from T₁ to T₂ during this process.

Step-2

"BC- Isothermal Compression Process"

Process "B to C" will be the isothermal compression process and therefore working fluid will be compressed here by keeping temperature constant. 

During the compression of the working fluid, temperature of working fluid will be increased but as we need to maintain the temperature constant and therefore we will use one cold thermal reservoir so that heat will be rejected to the cold thermal reservoir and temperature of the working fluid remain constant.

During this process BC, temperature of working fluid will remain constant and heat energy "Q₁" will be rejected by the system to the surrounding. 

 

Step-3 

"CD- Adiabatic Expansion Process"

Process "C to D" will be the adiabatic expansion process or isentropic expansion process. During this process, pressure and temperature of working fluid will be reduced while the volume of working fluid will be increased during this process.

There will not be any heat interaction between system and surrounding during this process. Temperature of working fluid will be reduced here from "T₂ to T₁" as shown in figure.

Step-4

"DA- Isothermal Expansion Process"

Process "D to A" will be the isothermal expansion process and therefore working fluid will be expanded here by keeping temperature constant. Pressure of working fluid will be reduced and volume of working fluid will be increased during this isothermal expansion process. 

             The temperature of working fluid will fall during this isothermal expansion process and therefore we have used one hot thermal reservoir in order to keep the temperature of working fluid constant. Heat energy "Q₂" will be added here to the system from surrounding at lower temperature.

 

Thus, during this process, heat energy "Q₂" will be absorbed by the working fluid at low temperature "T₁" from the space being cooled.

Conclusion

We have secured one reversible cycle "A-B-C-D-A" and this reversible cycle will be termed as "Reversed Carnot Heat Engine Cycle".

The term "Refrigerating Machine" can also refer to a reversed carnot heat engine. It will take in heat energy from a low-temperature region and transfer that heat energy by obtaining work energy from the surrounding to a high-temperature region.

!!!!The Coefficient Of Performance Of A Reverse Carnot Heat Engine Is Similar To That Of A Refrigerator!!!!

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