Oct 262012

A thermodynamic systemThermodynamic System (or simply ‘system’) is a definite macroscopic region or space in the universe, in which one or more thermodynamic processes take place.

Everything external to a thermodynamic system is called surroundings.

System and surroundings are separated by a definite border called boundary. System, surroundings and boundary constitute the universe.

See the image on the right for better understanding. :)

Types of Thermodynamic System:

Thermodynamic systems can be broadly classified into three types. They are:

  1. Open System
  2. Closed System
  3. Isolated System

1. Open System:

An open system is a thermodynamic system which allows both mass and energy to flow in and out of it, across its boundary. The image below illustrates open system.

Open System

Example of open system: Water heated in an open container – Here, heat is the energy transferred, water is the mass transferred and container is the thermodynamic system. Both heat and water can pass in and out of the container.

2. Closed System:

A closed system allows only energy (heat and work) to pass in and out of it. It does not allow mass transfer across its boundary. The following image shows a closed system:

 Closed System

Example of closed system: Water heated in a closed vessel – Here only heat energy can pass in and out of the vessel

3. Isolated System:

An isolated system does not interact with its surroundings. It does not allow both mass and energy transfer across its boundary. It is more restrictive.

In reality, complete isolated systems do not exist. However, some systems behave like an isolated system for a finite period of time. The following image illustrates an isolated system:

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Written by

I am a mechanical engineer with a passion for technical stuff. I am the founder and former editor-in-chief of Mechteacher.com.

  • srinath

    good article…..was very helpful…

  • dileep

    Please give an Example of isolated system….. ……Consider THERMODYNAMIC UNIVERSE

    • http://mechteacher.com/ Surjeet S

      As I have stated in the article, complete isolated systems do not exist. However, some systems behave like an isolated system for a finite period of time. A good example for such a system is hot water in an insulated flask.

  • Pooja Wadhvane

    In which system do we live

  • Arpita

    For closed system, the example was water heated in a closed container, can you please explain how heat moves out of the system as the container is closed ? Thanks.

    • http://mechteacher.com/ Surjeet Sankararaj

      Heat moves out of the system through convection.

  • Zaka Ur Rehman

    System of car is? And big brother kindly give more examples of open and close system.

  • nathan

    very helpful and easy explaining for a rush exam

  • Judith Ajima

    Please I need an explanation on phase equilibrium. Thanks