Introduction and Scope


Thermo: is a Greek word means Heat

Dynamic: means force

Thermodynamics is a branch of science which deals with:

  • Energy transfer [i.e. heat and work interactions] and its effect on the state or condition [i.e. properties] of a system.
  • It pertains to the study of:
    • Interaction of system and surroundings: it relates the changes which the system undergoes.
    • Energy and its transformation: all aspects of energy conversion, energy exchange, energy transfer, energy saving, etc.
  • It is a science having its relevance in every walk of life. It is very difficult to identify any area where there is no interaction in terms of energy and matter. Thermodynamics is basically a few fundamental laws and principles applied to a wide range of problems. 
  • Donald Haynie an American biophysicist claims that the word thermodynamics in 1840 was coined from Greek roots, i.e. therme meaning heat and dynamic meaning power. It was used by James Joule in 1858 to relate heat and power, however, Joule never used the term Thermodynamic, and by 1858, the term thermodynamics as a functional term was used by William Thomson.

Engineering thermodynamics: is the science that deals with design and analysis of practical energy conversion devices such as power plants develop shaft power from heat, refrigerators, heat pumps, air-conditioners, heat exchangers, nozzles, diffusers, etc,. It also studies the properties of various substances used in these devices. 


  • Thermodynamics derives its strength from experimental observation. These observations are formulated into four laws, which are known as:
  1. Zeroth Law:
  • deals with thermal equilibrium
  • concept of equality of temperature
  • provides a means for measuring temperature
  1. First Law:
  • pertains to the conservation of energy
  • introduces concept of internal energy
  1. Second Law:
  • relates the direction of flow of heat
  • indicates limits on conversion of  heat into work
  • introduces the concept of entropy
  1. Third Law:
  • ​​​​​​​defines absolute zero of entropy
  • ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​These laws are based on logical reasoning and experimental observations and have no mathematical proof.
  • The application of thermodynamic laws and principles are found in all fields of energy technology, notably in Steam and Nuclear power plant, IC-Engines, Gas turbines, Air-conditioning, Refrigeration, Gas dynamics, Jet-propulsion, Compressors, Chemical process plants, Direct energy conversion devices, etc.