System: A region in space on which we focus to study
its thermodynamic properties is known as system.
For example: we are studying the engine of
the vehicle, in this case engine is called as the system.
Similarly, the other examples of system
can be complete refrigerator, air-conditioner, washing machine, heat exchange,
a utensil with hot water etc.
Here, we will feed the engine with
fuels of different grades and load it with different loads to find out its
efficiency.
We will also find its performance
during idling, acceleration, varying speed, slow speed and high speed. A
thorough analysis of the engine is carried out; hence it is called as system.
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- The system is covered by the boundary and the area beyond the boundary is called as surroundings.
- The boundary of the system can be fixed or it can be movable.
- Between the system and surrounding the exchange of mass or energy or both can occur.
Types of Thermodynamic Systems
There are three main types of system:
- Open system,
- Closed system and
- Isolated system.
1.Open system: A system in which the transfer of mass as
well as energy can take place across its boundary is called as an open system. (mass and energy transfers)
- Our previous example of engine is an open system. In this case we provide fuel(mass) to engine and it produces power(energy) which is given out, thus there is exchange of mass as well as energy. The engine also emits heat, which is exchanged with the surroundings.
- The other example of open system is boiling water in an open vessel, where transfer of heat as well as mass in the form of steam takes place between the vessel and surrounding.
2.Closed system: The system in which only energy transfer takes place across its boundary with the surrounding, but no transfer of mass
takes place is called as closed system. The closed system is fixed mass system.
(only energy transfers)
- The fluid like air or gas being compressed in the piston and cylinder arrangement is an example of the closed system. In this case the mass of the gas remains constant but it can get heated or cooled.
- Another example is the water being heated in the closed vessel, where water will get heated but its mass will remn same.
3.Isolated system: The system in which neither the mass nor energy transfers takes place
across its boundary with the surroundings is called as isolated system
- For example if the piston and cylinder arrangement in which the fluid like air or gas is being compressed or expanded is insulated it becomes isolated system. Here there will neither transfer of mass nor that of energy.
- Similarly hot water, coffee or tea kept in the thermos flask is closed system. However, if we pour this fluid in a cup, it becomes an open system.