Discover 3 Types of Thermodynamic Systems With Examples [PDF]

A thermodynamic system refers to a specific area, region, or quantity of matter that is the focus of our study. This system is finite and can be measured in terms of its mass (in kilograms). Essentially, we examine the properties of the system within this defined space or region. To put it another way, the thermodynamic process takes place within this specific system, which serves as the context for our analysis.

thermodynamic systems

what is the definition of system

In thermodynamics, a system is that body or space or, a region where we are going to measure the properties or where thermodynamics processes are happening. That particular space or body is called a system. The system can be the finite quantity of matter or a selected region in space. It can be liquid, solid, or gas.

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what is the definition of a surrounding

Surrounding is the space outside of the system and there is another term which is a boundary that means an imaginary or real wall that divides the system and surrounding. Mathematically boundary has no thickness. That means it has no volume A boundary can be fixed or movable.

Thermodynamic Systems

Let us Understand the system, surroundings, and body comprised in a thermodynamic system by the simple example.

  • You all know the flask/thermos, where you can pour warm water, milk, tea etc..
  • So, in that case, the inside liquid of the flask is called the system, the body of the flask is called the boundary which separates the inside liquid from the outer condition or atmosphere, and the outer region where the flask is placed is called the surrounding, it may be a room or an open space.

There are two approaches to the analysis of a region or space, and that is the Control mass approach and the Control volume approach.

If we considered a particular mass of the system, then the process of measurement is called the control mass approach and if we do not need to study the mass or if we consider the mass, the analysis will be complicated, and then we will consider the control volume approach.

Types of interaction in thermodynamic systems

  • Mass interaction
  • Energy interaction

the types of thermodynamic systems

There are three types of thermodynamic system which are as follows

  • Open system
  • Closed system
  • Isolated system
TYPES OF Thermodynamic Systems

Open system

When in a system, mass and energy interaction is possible, then this type of system is called an open system. That means mass can go in and mass can go out of the system as well as energy can go in and energy can go out of the system.

open system

In mechanical engineering maximum of mechanical devices like a pump, and a turbine is in the category of the open system.


  • Suppose you are considering a pump, in this case, the pump delivers fluid from one section to another section. Some portion of the mass will go into the pump and then go out to the particular region. That means a certain mass of water is entered and a certain mass of water is going out of the pump. So is the example of mass interaction.
  • As well as when the impeller rotates inside the casing of a pump, then the rotational mechanical energy is transferred to the fluid which results in the increasing kinetic and pressure energy of the liquid.

Closed system

The closed system is a system of fixed mass. It means mass cannot cross the system boundary, but energy can cross the system boundary. A closed system is nothing but a Control mass approach.

closed system


  • A piston-cylinder without a valve that means the mass (liquid or air anything) inside the cylinder is fixed. It can not go out of the cylinder because there is no valve in the cylinder. But when we compressed the mass, we need some energy which means energy can transfer to the fluid may be in the form of heat.

Isolated system

In this type of system, neither mass interaction is possible, or energy interaction is possible this type of system is called Isolated system. But in real life, this is quite hard, or you can say impossible to find this type of working system.

isolated system


  • An example of an isolated system is a thermos where you can pour hot tea, milk, or anything. But in a thermos, there is no transfer of mass, the mass inside the thermos is constant, but after a specific time, the hot tea or milk inside the thermos will be at the normal temperature, which means there is an interaction of energy with the surrounding.
  • So if a thermos is fully thermally insulated where mass along with temperature or energy can not cross the surroundings or no interaction of these two is possible then you can say this is the perfect example of an isolated system.


In conclusion, a thorough understanding of the various types of thermodynamic systems and their real-world examples is essential in grasping the behavior and properties of matter and energy. This knowledge is valuable in various fields, including physics, chemistry, and engineering, where accurate predictions and control over system behavior are vital for technological advancements and innovations.

By applying the principles of thermodynamics to different types of systems, researchers can make significant contributions to various industries, improving our daily lives and shaping the world around us.

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