Process: 8 Most Important  Heating and Expanding Process of Gases

The various process is used for heating and expanding the gases in thermodynamics engineering.

These methods are also applicable to the contraction or cooling of gases.

Thus the contraction means negative expansion and cooling means negative heating.

Here you find the 8 process of heating and expanding the gases.

Constant Volume Process,Constant Pressure Process,Constant Temperature Process,Hyperbolic Process,Polytrophic Process,Free Expansion,Throttling Process

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So, Here are 8 important  Heating and Expanding process of Gases 

  • Constant Volume Process

There will be no change in Volume and no external work will be done by the gas. When a Gas is heated in a fixed enclosed space.

Due to heating, Pressure and Temperature will rise. And the whole heat supplied will be stored in the form of Internal Energy.


  • Constant Pressure Process

When a Gas is heated at constant Pressure, the Volume and the Temperature of a Gas will increase.

There will be some external work done due to increase in Volume.

  • Constant Temperature Process

This is also known as “Isothermal Process”.

When a heat is supplied to a gas at Constant Temperature, the expansion occurred is called “Isothermal Expansion”.

The whole of the heat supplied to the gas will be used up in doing external work.


  • Hyperbolic Process

When a Gas is heated in such a way that its Pressure multiplied by its Volume remains constant. The expansion called “Hyperbolic”.
The work done and the heat supplied is same. This is identical only in the case of Perfect Gas and not for vapours. 
  • Reversible Adiabatic Process

This is also called as “Isentropic Process”.

The system neither receives nor gives out heat to the surrounding.

This means no exchange of heat between the system and the surrounding.

  • Polytropic Process

This follows the general law (PRESSURE x VOLUME raise to n equals to Constant).

Where the index “n” may have any value depending upon the method of carrying out expansion.

  • Free Expansion

This is said to occur when a fluid suddenly expands into a Vacuum Chamber through an Orifice of large dimension.

No heat is supplied or rejected, there is no work done and the Temperature during this process remains constant.

  • Throttling Process

This type of expansion occurs when a gas or vapour is expanded through an Aperture of minute dimensions.

Like a valve which is very slightly opened or a narrow throat.

In this, if it is a perfect gas, there is no change in Temperature.

Besides this information, you are suggested to read something more from below engineering books 

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