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An Introduction To Basic Thermodynamics.

In this universe energy is available in various forms.A Branch of Science which deals with energy in all its forms and the laws governing the transformation of energy from one form to another is known as "Thermodynamics".Energy is available in the form of Mechanical,Thermal,Chemical Or Electrical etc...Thermodynamics covers a very broad field and is a base to many branches of Natural Science,Engineering and Technology.As we are concerned with Mechanical Engineering,the part of the subject which applies to engineering,is generally referred as Engineering Thermodynamics or Applied Thermodynamics.

It is important to all concerned engineers who are in the field of Power Generation Machinery,should have a working knowledge of all matters dealing with the conversion of heat energy into power.In designing of Boilers,Gas Turbines,Air Compressors,Steam Turbines,Internal Combustion Engines,Steam Engines,Refrigerating Machines etc... the law of Thermodynamics are very useful.In those days energy is on high demand due to rapid industrialisation all over the world.It is therefore,necessary to design and operate Thermal Plants and Machines at their highest level of performance and for efficient utilization of fuels and natural resources available.

Thermodynamics deals with the behaviour of gases and vapours when subjected to variations of temperature and pressure and the relationship between heat energy and mechanical energy,commonly referred to as work.When a substance undergoes to a change from one condition to another,in a process,energy transformation may occur.common process are those of heating or cooling and expansion or compression in the cylinder with or without production or supply of mechanical work.Chemical reaction and/or change of phase may occur in some process involving liberation of heat.

Now we will see some basic terms used in Thermodynamics.These are as follows.

01)Working Substance or Medium:-

Any Thermodynamic Process or change involves the use of working substance,which has the ability to receive,store and reject energy as required by the particular process.This medium may be in any one of the physical state such as solid,liquid vapour and gaseous.For example,in Steam Power Plant,water vapours used as Thermodynamic Medium where as in Ice Plant,Ammonia or Freon used as working substance.In Internal Combustion Engine and Gas Turbine,a mixture of air and fuel forms the working medium in the initial process and products of combustion in remaining processes.


A Thermodynamic System is a specific portion of matter,with definite boundary on which our attention is focused.The system boundary may be real,imaginary,fixed or deformable.Every thing outside the system which has direct bearing on its behaviour is known as surroundings.

There are three main types of system.
A) Isolated System:-In this system,both energy and mass can not exchange with its surroundings.
B) Closed System:-In this system,transfer of energy takes place but transfer of mass does not take place.
C) Open System:-In this system,energy and mass both may be transferred between the system and surroundings.

03)State and Properties of Substance:-

The exact condition of a substance is called its state and variables which determine the state are spoken of as its properties or parameters.The principal properties are pressure,volume,temperature,internal energy,enthalpy and entropy.If the Thermodynamic State is fixed,the properties are fixed with it.

04)Process and Cycle:-

When a system undergoes changes in its state,it is said to have undergone process,thus,a process is the path joining succession of state passed through by a system.A cycle is a process or a combination of processes so conducted that the initial and final states of the system are the same.

Some more details will cover in coming posts.I hope the above information will help you to understand something about Basic Thermodynamics.

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