Introduction and defination of thermodynamics

INTRODUCTION AND DEFINITION OF THERMODYNAMICS

Thermodynamics is a branch of science which deals with energy. Engineering thermodynamics is modified name of this science when applied to design and analysis of various energy conversion systems. Thermodynamics has basically a few fundamental laws and principles applied to a wide range of problems. Thermodynamics is core to engineering and allows understanding of the mechanism of energy conversion. It is really very difficult to identify any area where there is no interaction in terms of energy and matter. It is a science having its relevance in every walk of life. Thermodynamics can be classified as ‘Classical thermodynamics’ and ‘Statistical thermodynamics’. Here in engineering systems analysis the classical thermodynamics is employed. “Thermodynamics is the branch of physical science that deals with the various phenomena of energy and related properties of matter, especially of the laws of transformations of heat into other forms of energy and vice-versa.” Internal combustion engines employed in automobiles are a good example of the energy conversion equipment’s where fuel is being burnt inside the piston cylinder arrangement and chemical energy liberated by the fuel is used for getting the shaft work from crankshaft. Thermodynamics lets one know the answer for the questions as, what shall be the amount of work available from engine?, what shall be the efficiency of engine?, etc. For analysing any system there are basically two approaches available in engineering thermodynamics. Approach of thermodynamic analysis means how the analyser considers the system. Macroscopic approach is the one in which complete system as a whole is considered and studied without caring for what is there constituting the system at microscopic level. Contrary to this the microscopic approach is one having fragmented the system under consideration up to microscopic level and analysing the different constituent subsystems/microsystems. In this approach study is made at the microscopic level. For studying the system the micro level studies are put together to see the influences on overall system. Thus, the statistical techniques are used for integrating the studies made at microscopic level. This is how the studies are taken up in statistical thermodynamics. In general it can be said that, Macroscopic approach analysis = ∑ (Microscopic approach analysis).

DIMENSIONS AND UNITS

“Dimension” refers to certain fundamental physical concepts that are involved in the process of nature and are more or less directly evident to our physical senses, thus dimension is used for characterising any physical quantity. Dimensions can be broadly classified as “primary dimensions” and “secondary or derived dimensions”. “Basic dimensions such as mass ‘M’, length ‘L’, time ‘t’ and temperature ‘T’ are called primary dimensions, while quantities which are described using primary dimensions are called secondary dimensions such as for energy, velocity, force, volume, etc.”. “Units” are the magnitudes assigned to the dimensions. Units assigned to “primary dimensions” are called “basic units” whereas units assigned to “secondary dimensions” are called “derived units”. Various systems of units have prevailed in the past such as FPS (Foot-Pound-Second), CGS (Centimetre Gram-Second), MKS (Metre-Kilogram-Second) etc. but at present SI system (System-International) of units has been accepted world wide. Here in the present text also SI system of units has been used.

Following table gives the basic and derived units in SI system of units.