## Types of Thermodynamic Systems and Important Terms Related to Thermodynamics – Part 1

written by: Haresh Khemani • edited by: Swagatam • updated: 5/4/2010

Themodynamics is an important subject area studied under mechanical engineering. There are number of terms related to thermodynamics which are useful to know to understand this field. These terms and the types of systems in thermodynamics have been described in this article.

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### Importants Terms and Types of thermodynamic Systems

Here are some important terms which are found frequently in the subject area of thermodynamics and various types of system.

Thermodynamics: Thermodynamics is the branch of science or physics that studies various forms of energies and their conversion from one form to the other like electrical energy to mechanical energy, heat to electrical, chemical to mechanical, wind to electrical etc. The study of thermodynamics is comprised of important laws of thermodynamics namely first law of thermodynamics, second law of thermodynamics, third law of thermodynamics and Zeroth law of thermodynamics. Thermodynamics is an important subject area studied under Mechanical Engineering.

System: A quantity of the matter or part of the space which is under thermodynamic study is called as system. There are three types of system: closed system, open system and isolated system.

Surroundings or environment: Everything external to the matter or space, which is under thermodynamic study is called surroundings or environment.

Boundary: The boundary that separates the system and surrounding is called as system boundary. The system boundary may be fixed or moving.

Closed system: The system of fixed mass across the boundary of which no mass transfer can take place is called as closed system. However, across the closed system the energy transfer may take place. An example is fluid being compressed by the piston in cylinder.

Open system: The system across the boundary of which transfer of both mass as well as energy can take place across the boundary is called as open system. An example is an air compressor.

Isolated system: The system in which both the mass as well as energy content remains constant is called an isolated system. In this system no mass or energy transfer takes place across the boundary.

State of the system: The present status of the system described in terms of properties such as pressure, temperature, and volume is called the state of system.

Properties of the system: The characteristics by which the physical condition of the system is described are called as properties of system. Some examples of these characteristics are: temperature, pressure, volume etc and are called as properties of system. The system properties are of two types: extensive and intensive properties.

Extensive properties of system: The properties of the system that depend on the mass or quantity of the system are called extensive properties. Some examples of extensive properties are: mass, volume, enthalpy, internal energy, entropy etc.

Intensive properties of the system: These properties do not depend on the quantity of matter of the system. Some of the examples of intensive properties are: freezing point temperature, boiling point, temperature of the system, density, specific volume etc.

Types of Thermodynamic Systems and Important Terms - Part 2

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